PurposeGlioblastoma (GBM) is a lethal disease characterized by inevitable recurrence. Here we inv... more PurposeGlioblastoma (GBM) is a lethal disease characterized by inevitable recurrence. Here we investigate the molecular pathways mediating resistance, with the goal of identifying therapeutic opportunities to target this tumor.Experimental DesignWe developed a longitudinal in vivo recurrence model utilizing patient-derived explants to produce paired specimens (pre- and post-recurrence) following temozolomide(TMZ) and radiation(IR). These specimens were evaluated for treatment response and to identify gene expression pathways driving treatment resistance. Findings were clinically validated using spatial transcriptomics of human GBMs.ResultsThese studies reveal in replicate cohorts, a gene expression profile characterized by upregulation of mesenchymal and stem-like genes at recurrence. Analyses of clinical databases revealed increased expression of this transcriptional profile to be significantly associated with worse median overall survival (248 days vs 430 days, p=0.0004), and upre...
Despite the use of ionizing radiation (IR) and temozolomide (TMZ), outcome for glioblastoma (GBM)... more Despite the use of ionizing radiation (IR) and temozolomide (TMZ), outcome for glioblastoma (GBM) patients remains dismal. Poly (ADP-ribose) polymerase (PARP) is important in repair pathways for IR-induced DNA damage and TMZ-induced alkylation at N7-methylguanine and N3-methyldenine. However, optimized protocols for administration of PARP inhibitors have not been delineated. In this study, the PARP inhibitor ABT-888 was evaluated in combination with and compared to current standard-of-care in a genetically engineered mouse GBM model. Results demonstrated that concomitant TMZ/IR/ABT-888 with adjuvant TMZ/ABT-888 was more effective in inducing apoptosis and reducing proliferation with significant tumor growth delay and improved overall survival over concomitant TMZ/IR with adjuvant TMZ. Diffusion-weighted MRI, an early translatable response biomarker detected changes in tumors reflecting response at 1 day post TMZ/IR/ABT-888 treatment. This study provides strong scientific rationale f...
Survival rates associated with pancreatic cancer remain dismal despite advancements in detection ... more Survival rates associated with pancreatic cancer remain dismal despite advancements in detection and experimental treatment strategies. Genetically engineered mouse models of pancreatic tumorigenesis have gained considerable attention based on their ability to recapitulate key clinical features of human disease including chemotherapeutic resistance and fibrosis. However, it is unclear if transgenic systems exemplified by the Kras(G12D)/Trp53(R172H)/Pdx-1-Cre (KPC) mouse model recapitulate the functional heterogeneity of human pancreatic tumors harboring distinct cells with tumorigenic properties. To facilitate tracking of heterogeneous tumor cell populations, we incorporated a luciferase-based tag into the genetic background of the KPC mouse model. We isolated pancreatic cancer cells from multiple independent tumor lines and found that roughly 1 out of 87 cells exhibited tumorigenic capability. Notably, this frequency is significantly higher than reported for human pancreatic adenoc...
Attempts to target mutant KRAS have been unsuccessful. Here, we report the identification of Smad... more Attempts to target mutant KRAS have been unsuccessful. Here, we report the identification of Smad ubiquitination regulatory factor 2 (SMURF2) and UBCH5 as a critical E3:E2 complex maintaining KRAS protein stability. Loss of SMURF2 either by small interfering RNA/short hairpin RNA (siRNA/shRNA) or by overexpression of a catalytically inactive mutant causes KRAS degradation, whereas overexpression of wild-type SMURF2 enhances KRAS stability. Importantly, mutant KRAS is more susceptible to SMURF2 loss where protein half-life decreases from >12 hours in control siRNA-treated cells to <3 hours on Smurf2 silencing, whereas only marginal differences were noted for wild-type protein. This loss of mutant KRAS could be rescued by overexpressing a siRNA-resistant wild-type SMURF2. Our data further show that SMURF2 monoubiquitinates UBCH5 at lysine 144 to form an active complex required for efficient degradation of a RAS-family E3, β-transducing repeat containing protein 1 (β-TrCP1). Conv...
Transforming growth factor-β (TGF-β) signaling regulates cell proliferation and differentiation, ... more Transforming growth factor-β (TGF-β) signaling regulates cell proliferation and differentiation, which contributes to development and disease. Upon binding TGF-β, the type I receptor (TGFBRI) binds TGFBRII, leading to the activation of the transcription factors SMAD2 and SMAD3. Using an RNA interference screen of the human kinome and a live-cell reporter for TGFBR activity, we identified the kinase BUB1 (budding uninhibited by benzimidazoles-1) as a key mediator of TGF-β signaling. BUB1 interacted with TGFBRI in the presence of TGF-β and promoted the heterodimerization of TGFBRI and TGFBRII. Additionally, BUB1 interacted with TGFBRII, suggesting the formation of a ternary complex. Knocking down BUB1 prevented the recruitment of SMAD3 to the receptor complex, the phosphorylation of SMAD2 and SMAD3 and their interaction with SMAD4, SMAD-dependent transcription, and TGF-β-mediated changes in cellular phenotype including epithelial-mesenchymal transition (EMT), migration, and invasion. ...
Proceedings of the National Academy of Sciences, 2007
Chemokines and chemokine receptors have been posited to have important roles in several common ma... more Chemokines and chemokine receptors have been posited to have important roles in several common malignancies, including breast and lung cancer. Here, we demonstrate that CXCR7 (RDC1, CCX-CKR2), recently deorphanized as a chemokine receptor that binds chemokines CXCL11 and CXCL12, can regulate these two common malignancies. Using a combination of overexpression and RNA interference, we establish that CXCR7 promotes growth of tumors formed from breast and lung cancer cells and enhances experimental lung metastases in immunodeficient as well as immunocompetent mouse models of cancer. These effects did not depend on expression of the related receptor CXCR4. Furthermore, immunohistochemistry of primary human tumor tissue demonstrates extensive CXCR7 expression in human breast and lung cancers, where it is highly expressed on a majority of tumor-associated blood vessels and malignant cells but not expressed on normal vasculature. In addition, a critical role for CXCR7 in vascular formation...
There is an urgent need for the development of novel therapies to treat pancreatic cancer, which ... more There is an urgent need for the development of novel therapies to treat pancreatic cancer, which is among the most lethal of all cancers. KRAS-activating mutations, which are found in more than 90% of pancreatic adenocarcinomas, drive tumor dependency on the Ras/MAPK and Akt signaling pathways. Radiation is currently being explored as a component of the standard treatment regimen for pancreatic cancer. This study's purpose was to test the hypothesis that MAP kinase kinase (MEK or MAP2K) inhibitors will offer clear therapeutic benefit when integrated into radiotherapy treatment regimens for treatment of this disease. We explored the activation of the mitogen-activated protein kinase (MAPK) and Akt pathways in response to radiation in multiple pancreatic tumor cell lines. Small molecule inhibitors of MEK (PD0325901) and Akt (API-2) were subsequently evaluated for their radiosensitizing potential alone and in combination. In vivo efficacy was tested in subcutaneous MIA-PaCa2 xenogr...
Purpose: Functional imaging biomarkers of cancer treatment response offer the potential for early... more Purpose: Functional imaging biomarkers of cancer treatment response offer the potential for early determination of outcome through the assessment of biochemical, physiologic, and microenvironmental readouts. Cell death may result in an immunologic response, thus complicating the interpretation of biomarker readouts. This study evaluated the temporal effect of treatment-associated inflammatory activity on diffusion magnetic resonance imaging and 2-[18F]-fluoro-2-deoxy-d-glucose-positron emission tomography imaging (FDG-PET) biomarkers to delineate the effects of the inflammatory response on imaging readouts. Experimental Design: Rats with intracerebral 9L gliosarcomas were separated into four groups consisting of control, an immunosuppressive agent dexamethasone (Dex), 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and BCNU+Dex. Animals were imaged using diffusion-weighted magnetic resonance imaging and FDG-PET at 0, 3, and 7 days posttreatment. Results: In the BCNU- and BCNU+Dex-treat...
Prostate cancer ranks as the most common lethal malignancy diagnosed and the second leading cause... more Prostate cancer ranks as the most common lethal malignancy diagnosed and the second leading cause of cancer mortality in American men. Although high response rates are achieved using androgen blockade as first-line therapy, most men progress toward hormone-refractory prostate cancer. Systemic chemotherapies have been shown to improve clinical outcome in hormone refractory prostate cancer patients; however, they are not curative. Due to the high incidence of bone involvement in hormone-refractory prostate cancer, assessment of treatment response in metastatic prostate cancer to the bone remains a major clinical need. In this current study, we investigated the feasibility of using the functional diffusion map (fDM) as an imaging biomarker for assessing early treatment response in a preclinical model of metastatic prostate cancer. The fDM biomarker requires a pretreatment and midtreatment magnetic resonance imaging diffusion map, which is used to quantify spatially distinct therapeutic...
PurposeGlioblastoma (GBM) is a lethal disease characterized by inevitable recurrence. Here we inv... more PurposeGlioblastoma (GBM) is a lethal disease characterized by inevitable recurrence. Here we investigate the molecular pathways mediating resistance, with the goal of identifying therapeutic opportunities to target this tumor.Experimental DesignWe developed a longitudinal in vivo recurrence model utilizing patient-derived explants to produce paired specimens (pre- and post-recurrence) following temozolomide(TMZ) and radiation(IR). These specimens were evaluated for treatment response and to identify gene expression pathways driving treatment resistance. Findings were clinically validated using spatial transcriptomics of human GBMs.ResultsThese studies reveal in replicate cohorts, a gene expression profile characterized by upregulation of mesenchymal and stem-like genes at recurrence. Analyses of clinical databases revealed increased expression of this transcriptional profile to be significantly associated with worse median overall survival (248 days vs 430 days, p=0.0004), and upre...
Despite the use of ionizing radiation (IR) and temozolomide (TMZ), outcome for glioblastoma (GBM)... more Despite the use of ionizing radiation (IR) and temozolomide (TMZ), outcome for glioblastoma (GBM) patients remains dismal. Poly (ADP-ribose) polymerase (PARP) is important in repair pathways for IR-induced DNA damage and TMZ-induced alkylation at N7-methylguanine and N3-methyldenine. However, optimized protocols for administration of PARP inhibitors have not been delineated. In this study, the PARP inhibitor ABT-888 was evaluated in combination with and compared to current standard-of-care in a genetically engineered mouse GBM model. Results demonstrated that concomitant TMZ/IR/ABT-888 with adjuvant TMZ/ABT-888 was more effective in inducing apoptosis and reducing proliferation with significant tumor growth delay and improved overall survival over concomitant TMZ/IR with adjuvant TMZ. Diffusion-weighted MRI, an early translatable response biomarker detected changes in tumors reflecting response at 1 day post TMZ/IR/ABT-888 treatment. This study provides strong scientific rationale f...
Survival rates associated with pancreatic cancer remain dismal despite advancements in detection ... more Survival rates associated with pancreatic cancer remain dismal despite advancements in detection and experimental treatment strategies. Genetically engineered mouse models of pancreatic tumorigenesis have gained considerable attention based on their ability to recapitulate key clinical features of human disease including chemotherapeutic resistance and fibrosis. However, it is unclear if transgenic systems exemplified by the Kras(G12D)/Trp53(R172H)/Pdx-1-Cre (KPC) mouse model recapitulate the functional heterogeneity of human pancreatic tumors harboring distinct cells with tumorigenic properties. To facilitate tracking of heterogeneous tumor cell populations, we incorporated a luciferase-based tag into the genetic background of the KPC mouse model. We isolated pancreatic cancer cells from multiple independent tumor lines and found that roughly 1 out of 87 cells exhibited tumorigenic capability. Notably, this frequency is significantly higher than reported for human pancreatic adenoc...
Attempts to target mutant KRAS have been unsuccessful. Here, we report the identification of Smad... more Attempts to target mutant KRAS have been unsuccessful. Here, we report the identification of Smad ubiquitination regulatory factor 2 (SMURF2) and UBCH5 as a critical E3:E2 complex maintaining KRAS protein stability. Loss of SMURF2 either by small interfering RNA/short hairpin RNA (siRNA/shRNA) or by overexpression of a catalytically inactive mutant causes KRAS degradation, whereas overexpression of wild-type SMURF2 enhances KRAS stability. Importantly, mutant KRAS is more susceptible to SMURF2 loss where protein half-life decreases from >12 hours in control siRNA-treated cells to <3 hours on Smurf2 silencing, whereas only marginal differences were noted for wild-type protein. This loss of mutant KRAS could be rescued by overexpressing a siRNA-resistant wild-type SMURF2. Our data further show that SMURF2 monoubiquitinates UBCH5 at lysine 144 to form an active complex required for efficient degradation of a RAS-family E3, β-transducing repeat containing protein 1 (β-TrCP1). Conv...
Transforming growth factor-β (TGF-β) signaling regulates cell proliferation and differentiation, ... more Transforming growth factor-β (TGF-β) signaling regulates cell proliferation and differentiation, which contributes to development and disease. Upon binding TGF-β, the type I receptor (TGFBRI) binds TGFBRII, leading to the activation of the transcription factors SMAD2 and SMAD3. Using an RNA interference screen of the human kinome and a live-cell reporter for TGFBR activity, we identified the kinase BUB1 (budding uninhibited by benzimidazoles-1) as a key mediator of TGF-β signaling. BUB1 interacted with TGFBRI in the presence of TGF-β and promoted the heterodimerization of TGFBRI and TGFBRII. Additionally, BUB1 interacted with TGFBRII, suggesting the formation of a ternary complex. Knocking down BUB1 prevented the recruitment of SMAD3 to the receptor complex, the phosphorylation of SMAD2 and SMAD3 and their interaction with SMAD4, SMAD-dependent transcription, and TGF-β-mediated changes in cellular phenotype including epithelial-mesenchymal transition (EMT), migration, and invasion. ...
Proceedings of the National Academy of Sciences, 2007
Chemokines and chemokine receptors have been posited to have important roles in several common ma... more Chemokines and chemokine receptors have been posited to have important roles in several common malignancies, including breast and lung cancer. Here, we demonstrate that CXCR7 (RDC1, CCX-CKR2), recently deorphanized as a chemokine receptor that binds chemokines CXCL11 and CXCL12, can regulate these two common malignancies. Using a combination of overexpression and RNA interference, we establish that CXCR7 promotes growth of tumors formed from breast and lung cancer cells and enhances experimental lung metastases in immunodeficient as well as immunocompetent mouse models of cancer. These effects did not depend on expression of the related receptor CXCR4. Furthermore, immunohistochemistry of primary human tumor tissue demonstrates extensive CXCR7 expression in human breast and lung cancers, where it is highly expressed on a majority of tumor-associated blood vessels and malignant cells but not expressed on normal vasculature. In addition, a critical role for CXCR7 in vascular formation...
There is an urgent need for the development of novel therapies to treat pancreatic cancer, which ... more There is an urgent need for the development of novel therapies to treat pancreatic cancer, which is among the most lethal of all cancers. KRAS-activating mutations, which are found in more than 90% of pancreatic adenocarcinomas, drive tumor dependency on the Ras/MAPK and Akt signaling pathways. Radiation is currently being explored as a component of the standard treatment regimen for pancreatic cancer. This study's purpose was to test the hypothesis that MAP kinase kinase (MEK or MAP2K) inhibitors will offer clear therapeutic benefit when integrated into radiotherapy treatment regimens for treatment of this disease. We explored the activation of the mitogen-activated protein kinase (MAPK) and Akt pathways in response to radiation in multiple pancreatic tumor cell lines. Small molecule inhibitors of MEK (PD0325901) and Akt (API-2) were subsequently evaluated for their radiosensitizing potential alone and in combination. In vivo efficacy was tested in subcutaneous MIA-PaCa2 xenogr...
Purpose: Functional imaging biomarkers of cancer treatment response offer the potential for early... more Purpose: Functional imaging biomarkers of cancer treatment response offer the potential for early determination of outcome through the assessment of biochemical, physiologic, and microenvironmental readouts. Cell death may result in an immunologic response, thus complicating the interpretation of biomarker readouts. This study evaluated the temporal effect of treatment-associated inflammatory activity on diffusion magnetic resonance imaging and 2-[18F]-fluoro-2-deoxy-d-glucose-positron emission tomography imaging (FDG-PET) biomarkers to delineate the effects of the inflammatory response on imaging readouts. Experimental Design: Rats with intracerebral 9L gliosarcomas were separated into four groups consisting of control, an immunosuppressive agent dexamethasone (Dex), 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and BCNU+Dex. Animals were imaged using diffusion-weighted magnetic resonance imaging and FDG-PET at 0, 3, and 7 days posttreatment. Results: In the BCNU- and BCNU+Dex-treat...
Prostate cancer ranks as the most common lethal malignancy diagnosed and the second leading cause... more Prostate cancer ranks as the most common lethal malignancy diagnosed and the second leading cause of cancer mortality in American men. Although high response rates are achieved using androgen blockade as first-line therapy, most men progress toward hormone-refractory prostate cancer. Systemic chemotherapies have been shown to improve clinical outcome in hormone refractory prostate cancer patients; however, they are not curative. Due to the high incidence of bone involvement in hormone-refractory prostate cancer, assessment of treatment response in metastatic prostate cancer to the bone remains a major clinical need. In this current study, we investigated the feasibility of using the functional diffusion map (fDM) as an imaging biomarker for assessing early treatment response in a preclinical model of metastatic prostate cancer. The fDM biomarker requires a pretreatment and midtreatment magnetic resonance imaging diffusion map, which is used to quantify spatially distinct therapeutic...
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Papers by Alnawaz Rehemtulla