Metastatic cancer cells adapt to thrive in secondary organs. To investigate metastatic adaptation... more Metastatic cancer cells adapt to thrive in secondary organs. To investigate metastatic adaptation, we performed transcriptomic analysis of metastatic and non-metastatic murine breast cancer cells. We found that pleiotrophin (PTN), a neurotrophic cytokine, is a metastasis-associated factor that is expressed highly by aggressive breast cancers. Moreover, elevated PTN in plasma correlated significantly with metastasis and reduced survival of breast cancer patients. Mechanistically, we find that PTN activates NF-κB in cancer cells leading to altered cytokine production, subsequent neutrophil recruitment, and an immune suppressive microenvironment. Consequently, inhibition of PTN, pharmacologically or genetically, reduces the accumulation of tumor-associated neutrophils and reverts local immune suppression, resulting in increased T cell activation and attenuated metastasis. Furthermore, inhibition of PTN significantly enhanced the efficacy of immune checkpoint blockade and chemotherapy i...
<p>A–C) 1×10<sup>6</sup> Pan02 cells were injected into the tail of the pancrea... more <p>A–C) 1×10<sup>6</sup> Pan02 cells were injected into the tail of the pancreas of <i>SPARC+/+</i> and <i>SPARC−/−</i> mice. Tumors were allowed to grow for 10 days prior to initiation of losartan therapy (600 mg/L) via drinking water <i>ad libitum</i> in 2% sucrose. A) Survival curve of <i>SPARC+/+</i> and <i>SPARC−/−</i> mice treated with losartan (LOS). The table lists the median survival and associated p-values calculated with the Gehan-Breslow-Wilcoxon test (n = 10/group). The survival curve is modified from Arnold et al 2010 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031384#pone.0031384-Arnold1" target="_blank">[23]</a>. B) Graph displays spleen weight and the fold change calculated based on the weight of spleens taken from non-tumor bearing (NT) mice. Significance was determined by a Student's t-test and all significant p-values are indicated. C, D) 1×10<sup>6</sup> Pan02 cells were injected into the tail of the pancreas of <i>SPARC+/+</i> and <i>SPARC−/−</i> mice. Losartan therapy was given as above was initiated 24 hours after tumor cell injection and mice were sacrificed 28 days later. (C) Images of H&E stained primary tumor sections show residual pancreas and the primary tumor border of untreated and losartan-treated (LOS) <i>SPARC+/+</i> and <i>SPARC−/−</i> mice. Dotted lines demarcate the normal adjacent pancreas (P) from the primary tumor (T). Total magnification (50×) and scale bars (500 µm) are indicated. (D) H&E section of a spleen displaying disruption of the splenic capsule and local tumor invasion (I). Total magnification (200×) and scale bars (100 µm) are shown. Image of an H&E stained liver section revealing the common site for distant metastasis (M). Total magnification (200×) and scale bars (100 µm) are indicated.</p
<p>Fluorescence immunohistochemistry was utilized to quantify microvessel density and peric... more <p>Fluorescence immunohistochemistry was utilized to quantify microvessel density and pericyte recruitment in Pan02 orthotopic tumors grown in <i>SPARC+/+</i> and <i>SPARC−/−</i> mice treated with losartan (A–B). (A) Tumor sections were stained with rat anti-mouse endothelial cell Meca-32 (red) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031384#pone.0031384-Hallmann1" target="_blank">[64]</a>. DAPI (blue) marks cell nuclei. The percent thresholded area normalized to untreated <i>SPARC+/+</i>, number of blood vessels and mean blood vessel area were quantified. Total magnification (200×) and scale bars (100 µm) are indicated. (B) Sections were stained with Meca-32 and rabbit anti-NG2. Percent mature vessels were calculated as the number of Meca-32 & NG2 colocalized vessels divided by the total number of Meca-32 positive vessels. Total magnification (100×) and scale bars (200 µm) are shown. C) <i>SPARC+/+</i> and <i>SPARC−/−</i> mice bearing orthotopic Pan02 tumors and treated with losartan were injected intravenously with fluorescein isothiocyanate-conjugated dextran (FITC-Dextran) (25 mg/ml) (2×10<sup>6</sup> mw; D7137; Molecular Probes/Invitrogen) in 0.9% sterile saline at a dose of 200 µl/mouse. The fluorescent dextran was allowed to circulate 10 minutes before the mice were euthanized. Tissue was snap-frozen, sectioned (10 µm) and immediately analyzed by fluorescence microscopy. Percent thresholded area was quantified. Total magnification (200×) and scale bars (100 µm) are indicated. All p-values were calculated with the Student's t test.</p
Vascular endothelial growth factor-A (VEGF) is the predominant angiogenic factor that is expresse... more Vascular endothelial growth factor-A (VEGF) is the predominant angiogenic factor that is expressed in solid tumors. Besides its critical function in mediating tumor angiogenesis, multiple studies have demonstrated that VEGF also contributes to tumor immunosuppression. VEGF interferes with immune cell trafficking indirectly by promoting a vascular immune barrier through VEGF receptor (VEGFR) activity on endothelial cells. However, VEGFRs are also expressed on multiple immune cell types, including T cells (effector T cells, Tregs) and myeloid cells (DCs, TAMs, MDSCs), where VEGF can have direct effects on immune cell phenotype and function. Thus, it is not surprising that strategies targeting VEGF/VEGFRs have shown efficacy in alleviating tumor-associated immunosuppression and have been combined with immunotherapies, especially immune checkpoint blockade. In this review, we discuss the direct and indirect effects of VEGF on the immunosuppressive tumor microenvironment with particular ...
Pancreatic cancer is the third leading cause of cancer-related deaths in the United States with a... more Pancreatic cancer is the third leading cause of cancer-related deaths in the United States with a 5-year survival less than 5%. Resistance to standard therapy and limited response to immune checkpoint blockade due to the immunosuppressive and stroma-rich microenvironment remain major challenges in the treatment of pancreatic cancer. A key cellular program involved in therapy resistance is epithelial plasticity, which is also associated with invasion, metastasis, and evasion of immune surveillance. The receptor tyrosine kinase AXL is a key driver of tumor cell epithelial plasticity. High expression and activity of AXL is associated with poor prognosis, metastasis, and therapy resistance in multiple types of cancer including pancreatic. Here, we show that an AXL inhibitor (TP-0903), has antitumor and therapy sensitizing effects in preclinical models of pancreatic ductal adenocarcinoma (PDA). We demonstrate that TP-0903 as a single agent or in combination with gemcitabine and/or anti-p...
Pancreatic cancer is increasing in incidence and is expected to be the second leading cause of ca... more Pancreatic cancer is increasing in incidence and is expected to be the second leading cause of cancer-related mortality by the year 2030. Understanding molecular pathways that contribute to pancreatic cancer initiation and progression provides the opportunity to uncover potential molecular vulnerabilities that can be exploited therapeutically. In this issue of Cancer Research, Lee and colleagues provide compelling evidence that BRCA1-associated protein (BAP1) functions as a tumor suppressor in pancreatic cancer by promoting the activity of the Hippo tumor suppressor pathway, highlighting YAP and TAZ, Hippo effectors, as attractive therapeutic targets in pancreatic ductal adenocarcinoma, especially in BAP1-deficient or low tumors.See related article by Lee et al., p. 1656
Pancreatic ductal adenocarcinoma (PDA), a leading cause of cancer-related death in the US, has a ... more Pancreatic ductal adenocarcinoma (PDA), a leading cause of cancer-related death in the US, has a high metastatic rate and is associated with persistent immune suppression. AXL, a member of the TAM (TYRO3, AXL, MERTK) receptor tyrosine kinase family, has been identified as a driver of metastasis and immune suppression in multiple cancer types. Here we use single cell RNA sequencing to reveal that AXL is expressed highly in tumor cells that have a mesenchymal-like phenotype and that AXL expression correlates with classic markers of mesenchymal tumor cells. We demonstrate that AXL-deficiency extends survival, reduces primary and metastatic burden and enhances sensitivity to gemcitabine in an autochthonous model of PDA. PDA in AXL-deficient mice displayed a more differentiated histology, higher nucleoside transporter expression and a more active immune microenvironment compared to PDA in wild-type mice. Finally, we demonstrate that AXL-positive mesenchymal tumor cells are critical for P...
The extracellular matrix (ECM), a principal component of pancreatic ductal adenocarcinoma (PDA), ... more The extracellular matrix (ECM), a principal component of pancreatic ductal adenocarcinoma (PDA), is rich in fibrillar collagens that facilitate tumor cell survival and chemoresistance. Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that specifically binds fibrillar collagens and has been implicated in promoting cell proliferation, migration, adhesion, ECM remodeling, and response to growth factors. We found that collagen-induced activation of DDR1 stimulated protumorigenic signaling through protein tyrosine kinase 2 (PYK2) and pseudopodium-enriched atypical kinase 1 (PEAK1) in pancreatic cancer cells. Pharmacologic inhibition of DDR1 with an ATP-competitive orally available small-molecule kinase inhibitor (7rh) abrogated collagen-induced DDR1 signaling in pancreatic tumor cells and consequently reduced colony formation and migration. Furthermore, the inhibition of DDR1 with 7rh showed striking efficacy in combination with chemotherapy in orthotopic xenografts and a...
Strategies to Enhance the Therapeutic Ratio of Radiation as a Cancer Treatment, 2016
Inhibitors of cancer-specific pathways can selectively kill off tumor cells. However, heterogenei... more Inhibitors of cancer-specific pathways can selectively kill off tumor cells. However, heterogeneity of neoplastic tissue often allows other cancer cells to repopulate the tissue area, leading to regeneration of resistant disease. β-Lapachone is a novel bioactivatable drug that relies specifically on tumor-directed upregulated levels of NAD(P)H:quinone oxidoreductase 1 (NQO1) to kill most solid cancers, such as 90 % of pancreatic and non-small cell lung, 60 % of breast, colon, and prostate, as well as 50 % of head and neck cancers. Once β-lapachone is bioactivated by the NQO1 enzyme, massive levels of hydrogen peroxide are produced that, in turn, damage the DNA of cancer cells, while associated normal tissues, which lack NQO1, are protected by high levels of catalase. If tumors are irradiated prior to applying β-lapachone, the drug (clinical form, ARQ761) can work in combination with the vast spectrum of DNA lesions created by ionizing radiation, particularly DNA base lesions, single and double strand breaks (SSBs and DSBs), in addition to the massive hydrogen peroxide-based lesions created by β-lapachone, to cause tumor-dependent poly(ADP-ribose) polymerase 1 (PARP1) hyperactivation. Once tumor-selective PARP hyperactivation is induced in cancer cells, they die due to low concomitant catalase levels. In contrast, associated normal tissue, as well as other normal tissue, lack elevated levels of NQO1 and have high catalase levels. Cancer cell death ultimately occurs by NAD+-depletion, where resistance to NQO1 bioactivatable drugs has not been noted to date. Current studies are focused on pancreatic and non-small cell lung cancers, as NQO1 is elevated in nearly all of these cancers.
The deposition of extracellular matrix (ECM) is a defining feature of pancreatic ductal adenocarc... more The deposition of extracellular matrix (ECM) is a defining feature of pancreatic ductal adenocarcinoma (PDA) where ECM signaling can promote cancer cell survival and epithelial plasticity programs. However, ECM signaling can also limit PDA tumor growth by producing cytotoxic levels of reactive oxygen species (ROS). For example, excess fibronectin (FN) stimulation of α5β1 integrin on stromal cells in PDA results in reduced angiogenesis and increased tumor cell apoptosis due to oxidative stress. Fibulin-5 (Fbln5) is a matricellular protein that blocks FN-integrin interaction and thus directly limits ECM-driven ROS production and supports PDA progression. Compared to normal pancreatic tissue, Fbln5 is expressed abundantly in the stroma of PDA; however, the mechanisms underlying the stimulation of Fbln5 expression in PDA are undefined. Using in vitro and in vivo approaches, we report that hypoxia triggers Fbln5 expression in a transforming growth factor β (TGF-β)- and PI3K-dependent man...
Apoptosis is an evolutionarily conserved and tightly regulated cell death modality. It serves imp... more Apoptosis is an evolutionarily conserved and tightly regulated cell death modality. It serves important roles in physiology by sculpting complex tissues during embryogenesis and by removing effete cells that have reached advanced age or whose genomes have been irreparably damaged. Apoptosis culminates in the rapid and decisive removal of cell corpses by efferocytosis, a term used to distinguish the engulfment of apoptotic cells from other phagocytic processes. Over the past decades, the molecular and cell biological events associated with efferocytosis have been rigorously studied, and many eat-me signals and receptors have been identified. The externalization of phosphatidylserine (PS) is arguably the most emblematic eat-me signal that is in turn bound by a large number of serum proteins and opsonins that facilitate efferocytosis. Under physiological conditions, externalized PS functions as a dominant and evolutionarily conserved immunosuppressive signal that promotes tolerance and...
Pancreatic ductal adenocarcinoma (PDA) is a highly metastatic disease that resists most current t... more Pancreatic ductal adenocarcinoma (PDA) is a highly metastatic disease that resists most current therapies. A defining characteristic of PDA is an intense fibrotic response that promotes tumor cell invasion and chemoresistance. Efforts to understand the complex relationship between the tumor and its extracellular network and to therapeutically perturb tumor-stroma interactions are ongoing. Fibronectin (FN), a provisional matrix protein abundant in PDA stroma but not normal tissues, supports metastatic spread and chemoresistance of this deadly disease. FN also supports angiogenesis, which is required for even hypovascular tumors such as PDA to develop and progress. Targeting components of the tumor stroma, such as FN, can effectively reduce tumor growth and spread while also enhancing delivery of chemotherapy. Here, we review the molecular mechanisms by which FN drives angiogenesis, metastasis and chemoresistance in PDA. In light of these new findings, we also discuss therapeutic stra...
Repurposing 'old' drugs can facilitate rapid clinical translation but necessitates novel ... more Repurposing 'old' drugs can facilitate rapid clinical translation but necessitates novel mechanistic insight. Warfarin, a vitamin K "antagonist" used clinically for the prevention of thrombosis for over 50 years, has been shown to have anti-cancer effects. We hypothesized that the molecular mechanism underlying its anti-tumor activity is unrelated to its effect on coagulation, but is due to inhibition of the Axl receptor tyrosine kinase on tumor cells. Activation of Axl by its ligand Gas6, a vitamin K-dependent protein, is inhibited at doses of warfarin that do not affect coagulation. Here we show that inhibiting Gas6-dependent Axl activation with low dose warfarin or with other tumor-specific Axl targeting agents, blocks the progression and spread of pancreatic cancer. Warfarin also inhibited Axl-dependent tumor cell migration, invasiveness and proliferation while increasing apoptosis and sensitivity to chemotherapy. We conclude that Gas6-induced Axl signaling is ...
Effective therapies are needed to enhance the long-term survival of patients with pancreatic duct... more Effective therapies are needed to enhance the long-term survival of patients with pancreatic ductal adenocarcinoma (PDAC), which is the fourth leading cause of cancer-related deaths in the United States and eighth worldwide. The mere 5-year survival rate of 5% is the lowest of all cancers and is due in part to late diagnosis and resistance to conventional therapy. Therefore, it is critical to identify molecular vulnerabilities in PDAC for developing targeted therapies. Activating point mutations in the small GTPase, K-Ras are present in 90% of PDAC cases. However, successful strategies that exploit the reliance of PDAC on mutant K-Ras have not been developed. Recent studies have shown that PDAC cell lines demonstrate a pronounced dependence on autophagy and that oncogenic Ras activates autophagy to maintain tumorigenesis. However, the mechanism by which oncogenic Ras induces autophagy is poorly understood. Notably, Tank Binding Kinase 1 (TBK1) operates downstream of the Ras effector...
Axl is a member of the TAM (Tyro3, Axl and Mer) family of receptor tyrosine kinases that regulate... more Axl is a member of the TAM (Tyro3, Axl and Mer) family of receptor tyrosine kinases that regulate multiple cellular responses including cell survival, proliferation, and migration. Axl expression is predictive of poor patient overall survival in a variety of human cancers including triple negative breast (TNBC), pancreatic ductal adenocarcinoma (PDA) and non-small cell lung cancer (NSCLC). Axl expression is induced by the epithelial-to-mesenchymal transition (EMT) gene program in cancer cells and Axl signaling is required to maintain EMT-associated features including invasiveness, metastasis, stem cell-like traits and resistance to targeted inhibitors and other chemotherapeutic agents. BGB324/R428 is an oral, selective small molecule inhibitor of Axl that recently was evaluated in early clinical safety studies in healthy volunteers. Treatment with BGB324 up to and including 1.5 gms daily (per os) was established as being safe and well tolerated. The endpoints of the study included p...
Secreted protein acidic and rich in cysteine (SPARC), a member of the family of matricellular pro... more Secreted protein acidic and rich in cysteine (SPARC), a member of the family of matricellular proteins, regulates the interaction of cells with pleiotropic factors and proteins of the extracellular matrix (ECM). Although it has been appreciated that transforming growth factor beta 1 (TGF-beta1) induces SPARC and collagen type I, we have recently shown that SPARC regulates the expression of TGF-beta1 and collagen type I in renal mesangial cells via a TGF-beta1-dependent pathway, and have proposed a reciprocal, autocrine regulatory feedback loop between SPARC and TGF-beta1. Herein, we sought to determine how SPARC regulates TGF-beta1-dependent signal transduction. Our data indicate that SPARC modulates the TGF-beta1-dependent phosphorylation of Smad-2 in primary mesangial cells derived from wild-type and SPARC-null mice. We also show that SPARC regulates the levels and activation of the stress-activated c-jun-N-terminal kinase (JNK) in mesangial cells by augmentation of the stimulatory effects of TGF-beta1. Furthermore, we found that SPARC increases the levels and the activity of the transcription factor c-jun. These effects of SPARC on the TGF-beta1 signaling pathway appear to be mediated through an interaction with the TGF-beta1-receptor complex, but only in the presence of TGF-beta1 bound to its cognate type II receptor. That SPARC is directly involved in the regulation of the TGF-beta1 signaling cascade is consistent with the paradigm that matricellular proteins modulate interactions among cells, growth factors, and their respective receptors.
Purpose: New strategies to detect tumor angiogenesis and monitor response of tumor vasculature to... more Purpose: New strategies to detect tumor angiogenesis and monitor response of tumor vasculature to therapy are needed. Contrast ultrasound imaging using microbubbles targeted to tumor endothelium offers a noninvasive method for monitoring and quantifying vascular effects of antitumor therapy. We investigated the use of targeted microbubbles to follow vascular response of therapy in a mouse model of pancreatic adenocarcinoma. Experimental Design: Microbubbles conjugated to monoclonal antibodies were used to image and quantify vascular effects of two different antitumor therapies in s.c. and orthotopic pancreatic tumors in mice. Tumor-bearing mice were treated with anti-vascular endothelial growth factor (VEGF) monoclonal antibodies and/or gemcitabine, and the localization of microbubbles to endoglin (CD105), VEGF receptor 2 (VEGFR2), or VEGF-activated blood vessels (the VEGF-VEGFR complex) was monitored by contrast ultrasound. Results: Targeted microbubbles showed significant enhancem...
Metastatic cancer cells adapt to thrive in secondary organs. To investigate metastatic adaptation... more Metastatic cancer cells adapt to thrive in secondary organs. To investigate metastatic adaptation, we performed transcriptomic analysis of metastatic and non-metastatic murine breast cancer cells. We found that pleiotrophin (PTN), a neurotrophic cytokine, is a metastasis-associated factor that is expressed highly by aggressive breast cancers. Moreover, elevated PTN in plasma correlated significantly with metastasis and reduced survival of breast cancer patients. Mechanistically, we find that PTN activates NF-κB in cancer cells leading to altered cytokine production, subsequent neutrophil recruitment, and an immune suppressive microenvironment. Consequently, inhibition of PTN, pharmacologically or genetically, reduces the accumulation of tumor-associated neutrophils and reverts local immune suppression, resulting in increased T cell activation and attenuated metastasis. Furthermore, inhibition of PTN significantly enhanced the efficacy of immune checkpoint blockade and chemotherapy i...
<p>A–C) 1×10<sup>6</sup> Pan02 cells were injected into the tail of the pancrea... more <p>A–C) 1×10<sup>6</sup> Pan02 cells were injected into the tail of the pancreas of <i>SPARC+/+</i> and <i>SPARC−/−</i> mice. Tumors were allowed to grow for 10 days prior to initiation of losartan therapy (600 mg/L) via drinking water <i>ad libitum</i> in 2% sucrose. A) Survival curve of <i>SPARC+/+</i> and <i>SPARC−/−</i> mice treated with losartan (LOS). The table lists the median survival and associated p-values calculated with the Gehan-Breslow-Wilcoxon test (n = 10/group). The survival curve is modified from Arnold et al 2010 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031384#pone.0031384-Arnold1" target="_blank">[23]</a>. B) Graph displays spleen weight and the fold change calculated based on the weight of spleens taken from non-tumor bearing (NT) mice. Significance was determined by a Student's t-test and all significant p-values are indicated. C, D) 1×10<sup>6</sup> Pan02 cells were injected into the tail of the pancreas of <i>SPARC+/+</i> and <i>SPARC−/−</i> mice. Losartan therapy was given as above was initiated 24 hours after tumor cell injection and mice were sacrificed 28 days later. (C) Images of H&E stained primary tumor sections show residual pancreas and the primary tumor border of untreated and losartan-treated (LOS) <i>SPARC+/+</i> and <i>SPARC−/−</i> mice. Dotted lines demarcate the normal adjacent pancreas (P) from the primary tumor (T). Total magnification (50×) and scale bars (500 µm) are indicated. (D) H&E section of a spleen displaying disruption of the splenic capsule and local tumor invasion (I). Total magnification (200×) and scale bars (100 µm) are shown. Image of an H&E stained liver section revealing the common site for distant metastasis (M). Total magnification (200×) and scale bars (100 µm) are indicated.</p
<p>Fluorescence immunohistochemistry was utilized to quantify microvessel density and peric... more <p>Fluorescence immunohistochemistry was utilized to quantify microvessel density and pericyte recruitment in Pan02 orthotopic tumors grown in <i>SPARC+/+</i> and <i>SPARC−/−</i> mice treated with losartan (A–B). (A) Tumor sections were stained with rat anti-mouse endothelial cell Meca-32 (red) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031384#pone.0031384-Hallmann1" target="_blank">[64]</a>. DAPI (blue) marks cell nuclei. The percent thresholded area normalized to untreated <i>SPARC+/+</i>, number of blood vessels and mean blood vessel area were quantified. Total magnification (200×) and scale bars (100 µm) are indicated. (B) Sections were stained with Meca-32 and rabbit anti-NG2. Percent mature vessels were calculated as the number of Meca-32 & NG2 colocalized vessels divided by the total number of Meca-32 positive vessels. Total magnification (100×) and scale bars (200 µm) are shown. C) <i>SPARC+/+</i> and <i>SPARC−/−</i> mice bearing orthotopic Pan02 tumors and treated with losartan were injected intravenously with fluorescein isothiocyanate-conjugated dextran (FITC-Dextran) (25 mg/ml) (2×10<sup>6</sup> mw; D7137; Molecular Probes/Invitrogen) in 0.9% sterile saline at a dose of 200 µl/mouse. The fluorescent dextran was allowed to circulate 10 minutes before the mice were euthanized. Tissue was snap-frozen, sectioned (10 µm) and immediately analyzed by fluorescence microscopy. Percent thresholded area was quantified. Total magnification (200×) and scale bars (100 µm) are indicated. All p-values were calculated with the Student's t test.</p
Vascular endothelial growth factor-A (VEGF) is the predominant angiogenic factor that is expresse... more Vascular endothelial growth factor-A (VEGF) is the predominant angiogenic factor that is expressed in solid tumors. Besides its critical function in mediating tumor angiogenesis, multiple studies have demonstrated that VEGF also contributes to tumor immunosuppression. VEGF interferes with immune cell trafficking indirectly by promoting a vascular immune barrier through VEGF receptor (VEGFR) activity on endothelial cells. However, VEGFRs are also expressed on multiple immune cell types, including T cells (effector T cells, Tregs) and myeloid cells (DCs, TAMs, MDSCs), where VEGF can have direct effects on immune cell phenotype and function. Thus, it is not surprising that strategies targeting VEGF/VEGFRs have shown efficacy in alleviating tumor-associated immunosuppression and have been combined with immunotherapies, especially immune checkpoint blockade. In this review, we discuss the direct and indirect effects of VEGF on the immunosuppressive tumor microenvironment with particular ...
Pancreatic cancer is the third leading cause of cancer-related deaths in the United States with a... more Pancreatic cancer is the third leading cause of cancer-related deaths in the United States with a 5-year survival less than 5%. Resistance to standard therapy and limited response to immune checkpoint blockade due to the immunosuppressive and stroma-rich microenvironment remain major challenges in the treatment of pancreatic cancer. A key cellular program involved in therapy resistance is epithelial plasticity, which is also associated with invasion, metastasis, and evasion of immune surveillance. The receptor tyrosine kinase AXL is a key driver of tumor cell epithelial plasticity. High expression and activity of AXL is associated with poor prognosis, metastasis, and therapy resistance in multiple types of cancer including pancreatic. Here, we show that an AXL inhibitor (TP-0903), has antitumor and therapy sensitizing effects in preclinical models of pancreatic ductal adenocarcinoma (PDA). We demonstrate that TP-0903 as a single agent or in combination with gemcitabine and/or anti-p...
Pancreatic cancer is increasing in incidence and is expected to be the second leading cause of ca... more Pancreatic cancer is increasing in incidence and is expected to be the second leading cause of cancer-related mortality by the year 2030. Understanding molecular pathways that contribute to pancreatic cancer initiation and progression provides the opportunity to uncover potential molecular vulnerabilities that can be exploited therapeutically. In this issue of Cancer Research, Lee and colleagues provide compelling evidence that BRCA1-associated protein (BAP1) functions as a tumor suppressor in pancreatic cancer by promoting the activity of the Hippo tumor suppressor pathway, highlighting YAP and TAZ, Hippo effectors, as attractive therapeutic targets in pancreatic ductal adenocarcinoma, especially in BAP1-deficient or low tumors.See related article by Lee et al., p. 1656
Pancreatic ductal adenocarcinoma (PDA), a leading cause of cancer-related death in the US, has a ... more Pancreatic ductal adenocarcinoma (PDA), a leading cause of cancer-related death in the US, has a high metastatic rate and is associated with persistent immune suppression. AXL, a member of the TAM (TYRO3, AXL, MERTK) receptor tyrosine kinase family, has been identified as a driver of metastasis and immune suppression in multiple cancer types. Here we use single cell RNA sequencing to reveal that AXL is expressed highly in tumor cells that have a mesenchymal-like phenotype and that AXL expression correlates with classic markers of mesenchymal tumor cells. We demonstrate that AXL-deficiency extends survival, reduces primary and metastatic burden and enhances sensitivity to gemcitabine in an autochthonous model of PDA. PDA in AXL-deficient mice displayed a more differentiated histology, higher nucleoside transporter expression and a more active immune microenvironment compared to PDA in wild-type mice. Finally, we demonstrate that AXL-positive mesenchymal tumor cells are critical for P...
The extracellular matrix (ECM), a principal component of pancreatic ductal adenocarcinoma (PDA), ... more The extracellular matrix (ECM), a principal component of pancreatic ductal adenocarcinoma (PDA), is rich in fibrillar collagens that facilitate tumor cell survival and chemoresistance. Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that specifically binds fibrillar collagens and has been implicated in promoting cell proliferation, migration, adhesion, ECM remodeling, and response to growth factors. We found that collagen-induced activation of DDR1 stimulated protumorigenic signaling through protein tyrosine kinase 2 (PYK2) and pseudopodium-enriched atypical kinase 1 (PEAK1) in pancreatic cancer cells. Pharmacologic inhibition of DDR1 with an ATP-competitive orally available small-molecule kinase inhibitor (7rh) abrogated collagen-induced DDR1 signaling in pancreatic tumor cells and consequently reduced colony formation and migration. Furthermore, the inhibition of DDR1 with 7rh showed striking efficacy in combination with chemotherapy in orthotopic xenografts and a...
Strategies to Enhance the Therapeutic Ratio of Radiation as a Cancer Treatment, 2016
Inhibitors of cancer-specific pathways can selectively kill off tumor cells. However, heterogenei... more Inhibitors of cancer-specific pathways can selectively kill off tumor cells. However, heterogeneity of neoplastic tissue often allows other cancer cells to repopulate the tissue area, leading to regeneration of resistant disease. β-Lapachone is a novel bioactivatable drug that relies specifically on tumor-directed upregulated levels of NAD(P)H:quinone oxidoreductase 1 (NQO1) to kill most solid cancers, such as 90 % of pancreatic and non-small cell lung, 60 % of breast, colon, and prostate, as well as 50 % of head and neck cancers. Once β-lapachone is bioactivated by the NQO1 enzyme, massive levels of hydrogen peroxide are produced that, in turn, damage the DNA of cancer cells, while associated normal tissues, which lack NQO1, are protected by high levels of catalase. If tumors are irradiated prior to applying β-lapachone, the drug (clinical form, ARQ761) can work in combination with the vast spectrum of DNA lesions created by ionizing radiation, particularly DNA base lesions, single and double strand breaks (SSBs and DSBs), in addition to the massive hydrogen peroxide-based lesions created by β-lapachone, to cause tumor-dependent poly(ADP-ribose) polymerase 1 (PARP1) hyperactivation. Once tumor-selective PARP hyperactivation is induced in cancer cells, they die due to low concomitant catalase levels. In contrast, associated normal tissue, as well as other normal tissue, lack elevated levels of NQO1 and have high catalase levels. Cancer cell death ultimately occurs by NAD+-depletion, where resistance to NQO1 bioactivatable drugs has not been noted to date. Current studies are focused on pancreatic and non-small cell lung cancers, as NQO1 is elevated in nearly all of these cancers.
The deposition of extracellular matrix (ECM) is a defining feature of pancreatic ductal adenocarc... more The deposition of extracellular matrix (ECM) is a defining feature of pancreatic ductal adenocarcinoma (PDA) where ECM signaling can promote cancer cell survival and epithelial plasticity programs. However, ECM signaling can also limit PDA tumor growth by producing cytotoxic levels of reactive oxygen species (ROS). For example, excess fibronectin (FN) stimulation of α5β1 integrin on stromal cells in PDA results in reduced angiogenesis and increased tumor cell apoptosis due to oxidative stress. Fibulin-5 (Fbln5) is a matricellular protein that blocks FN-integrin interaction and thus directly limits ECM-driven ROS production and supports PDA progression. Compared to normal pancreatic tissue, Fbln5 is expressed abundantly in the stroma of PDA; however, the mechanisms underlying the stimulation of Fbln5 expression in PDA are undefined. Using in vitro and in vivo approaches, we report that hypoxia triggers Fbln5 expression in a transforming growth factor β (TGF-β)- and PI3K-dependent man...
Apoptosis is an evolutionarily conserved and tightly regulated cell death modality. It serves imp... more Apoptosis is an evolutionarily conserved and tightly regulated cell death modality. It serves important roles in physiology by sculpting complex tissues during embryogenesis and by removing effete cells that have reached advanced age or whose genomes have been irreparably damaged. Apoptosis culminates in the rapid and decisive removal of cell corpses by efferocytosis, a term used to distinguish the engulfment of apoptotic cells from other phagocytic processes. Over the past decades, the molecular and cell biological events associated with efferocytosis have been rigorously studied, and many eat-me signals and receptors have been identified. The externalization of phosphatidylserine (PS) is arguably the most emblematic eat-me signal that is in turn bound by a large number of serum proteins and opsonins that facilitate efferocytosis. Under physiological conditions, externalized PS functions as a dominant and evolutionarily conserved immunosuppressive signal that promotes tolerance and...
Pancreatic ductal adenocarcinoma (PDA) is a highly metastatic disease that resists most current t... more Pancreatic ductal adenocarcinoma (PDA) is a highly metastatic disease that resists most current therapies. A defining characteristic of PDA is an intense fibrotic response that promotes tumor cell invasion and chemoresistance. Efforts to understand the complex relationship between the tumor and its extracellular network and to therapeutically perturb tumor-stroma interactions are ongoing. Fibronectin (FN), a provisional matrix protein abundant in PDA stroma but not normal tissues, supports metastatic spread and chemoresistance of this deadly disease. FN also supports angiogenesis, which is required for even hypovascular tumors such as PDA to develop and progress. Targeting components of the tumor stroma, such as FN, can effectively reduce tumor growth and spread while also enhancing delivery of chemotherapy. Here, we review the molecular mechanisms by which FN drives angiogenesis, metastasis and chemoresistance in PDA. In light of these new findings, we also discuss therapeutic stra...
Repurposing 'old' drugs can facilitate rapid clinical translation but necessitates novel ... more Repurposing 'old' drugs can facilitate rapid clinical translation but necessitates novel mechanistic insight. Warfarin, a vitamin K "antagonist" used clinically for the prevention of thrombosis for over 50 years, has been shown to have anti-cancer effects. We hypothesized that the molecular mechanism underlying its anti-tumor activity is unrelated to its effect on coagulation, but is due to inhibition of the Axl receptor tyrosine kinase on tumor cells. Activation of Axl by its ligand Gas6, a vitamin K-dependent protein, is inhibited at doses of warfarin that do not affect coagulation. Here we show that inhibiting Gas6-dependent Axl activation with low dose warfarin or with other tumor-specific Axl targeting agents, blocks the progression and spread of pancreatic cancer. Warfarin also inhibited Axl-dependent tumor cell migration, invasiveness and proliferation while increasing apoptosis and sensitivity to chemotherapy. We conclude that Gas6-induced Axl signaling is ...
Effective therapies are needed to enhance the long-term survival of patients with pancreatic duct... more Effective therapies are needed to enhance the long-term survival of patients with pancreatic ductal adenocarcinoma (PDAC), which is the fourth leading cause of cancer-related deaths in the United States and eighth worldwide. The mere 5-year survival rate of 5% is the lowest of all cancers and is due in part to late diagnosis and resistance to conventional therapy. Therefore, it is critical to identify molecular vulnerabilities in PDAC for developing targeted therapies. Activating point mutations in the small GTPase, K-Ras are present in 90% of PDAC cases. However, successful strategies that exploit the reliance of PDAC on mutant K-Ras have not been developed. Recent studies have shown that PDAC cell lines demonstrate a pronounced dependence on autophagy and that oncogenic Ras activates autophagy to maintain tumorigenesis. However, the mechanism by which oncogenic Ras induces autophagy is poorly understood. Notably, Tank Binding Kinase 1 (TBK1) operates downstream of the Ras effector...
Axl is a member of the TAM (Tyro3, Axl and Mer) family of receptor tyrosine kinases that regulate... more Axl is a member of the TAM (Tyro3, Axl and Mer) family of receptor tyrosine kinases that regulate multiple cellular responses including cell survival, proliferation, and migration. Axl expression is predictive of poor patient overall survival in a variety of human cancers including triple negative breast (TNBC), pancreatic ductal adenocarcinoma (PDA) and non-small cell lung cancer (NSCLC). Axl expression is induced by the epithelial-to-mesenchymal transition (EMT) gene program in cancer cells and Axl signaling is required to maintain EMT-associated features including invasiveness, metastasis, stem cell-like traits and resistance to targeted inhibitors and other chemotherapeutic agents. BGB324/R428 is an oral, selective small molecule inhibitor of Axl that recently was evaluated in early clinical safety studies in healthy volunteers. Treatment with BGB324 up to and including 1.5 gms daily (per os) was established as being safe and well tolerated. The endpoints of the study included p...
Secreted protein acidic and rich in cysteine (SPARC), a member of the family of matricellular pro... more Secreted protein acidic and rich in cysteine (SPARC), a member of the family of matricellular proteins, regulates the interaction of cells with pleiotropic factors and proteins of the extracellular matrix (ECM). Although it has been appreciated that transforming growth factor beta 1 (TGF-beta1) induces SPARC and collagen type I, we have recently shown that SPARC regulates the expression of TGF-beta1 and collagen type I in renal mesangial cells via a TGF-beta1-dependent pathway, and have proposed a reciprocal, autocrine regulatory feedback loop between SPARC and TGF-beta1. Herein, we sought to determine how SPARC regulates TGF-beta1-dependent signal transduction. Our data indicate that SPARC modulates the TGF-beta1-dependent phosphorylation of Smad-2 in primary mesangial cells derived from wild-type and SPARC-null mice. We also show that SPARC regulates the levels and activation of the stress-activated c-jun-N-terminal kinase (JNK) in mesangial cells by augmentation of the stimulatory effects of TGF-beta1. Furthermore, we found that SPARC increases the levels and the activity of the transcription factor c-jun. These effects of SPARC on the TGF-beta1 signaling pathway appear to be mediated through an interaction with the TGF-beta1-receptor complex, but only in the presence of TGF-beta1 bound to its cognate type II receptor. That SPARC is directly involved in the regulation of the TGF-beta1 signaling cascade is consistent with the paradigm that matricellular proteins modulate interactions among cells, growth factors, and their respective receptors.
Purpose: New strategies to detect tumor angiogenesis and monitor response of tumor vasculature to... more Purpose: New strategies to detect tumor angiogenesis and monitor response of tumor vasculature to therapy are needed. Contrast ultrasound imaging using microbubbles targeted to tumor endothelium offers a noninvasive method for monitoring and quantifying vascular effects of antitumor therapy. We investigated the use of targeted microbubbles to follow vascular response of therapy in a mouse model of pancreatic adenocarcinoma. Experimental Design: Microbubbles conjugated to monoclonal antibodies were used to image and quantify vascular effects of two different antitumor therapies in s.c. and orthotopic pancreatic tumors in mice. Tumor-bearing mice were treated with anti-vascular endothelial growth factor (VEGF) monoclonal antibodies and/or gemcitabine, and the localization of microbubbles to endoglin (CD105), VEGF receptor 2 (VEGFR2), or VEGF-activated blood vessels (the VEGF-VEGFR complex) was monitored by contrast ultrasound. Results: Targeted microbubbles showed significant enhancem...
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