BackgroundProstate cancer is the second leading cause of cancer related death in men in the Unite... more BackgroundProstate cancer is the second leading cause of cancer related death in men in the United States, mainly due to disease progression to metastatic castration-resistant prostate cancer (mCRPC). Although immunological treatment with the FDA-approved vaccine sipuleucel-T extends survival for 2–4 months by targeting the prostate-restricted antigen PAP, the identification of more immunogenic tumor-associated antigens (TAAs) continues to be an unmet need.MethodsWe evaluated the differential expression profile of the subset of epithelial cells reported to give rise to CRPC from mice following an androgen deprivation/repletion cycle. The expression levels of a set of androgen-responsive genes was further evaluated in prostate, brain, colon, liver, lung, and skin normal tissues from murine and human databases. The expression of a novel prostate-restricted TAA was then analyzed in primary tumors across all human cancer types in The Cancer Genome Atlas (TCGA). Finally, the immunogenici...
5035 Background: ARV7+ mCRPC is an aggressive phenotype with a median PFS of 3-4 mo and OS of 7-9... more 5035 Background: ARV7+ mCRPC is an aggressive phenotype with a median PFS of 3-4 mo and OS of 7-9 mo. We hypothesized that ARV7+ tumors would be enriched for DNA repair mutations, rendering them more responsive to combined immune checkpoint blockade. Methods: We enrolled 15 mCRPC pts with ARV7+ CTCs (using a CLIA-certified assay) into a single arm phase 2 study. Pts received Nivo 3 mg/kg plus Ipi 1 mg/kg every 3 wk x 4 doses, then maintenance Nivo 3 mg/kg every 2 wk. Targeted sequencing for DNA repair defects was performed on pretreatment tumor biopsies (n=11) or cell-free DNA (n=4). Primary endpoint: PSA50response rate. Secondary endpoints: objective response rate (ORR) in pts with measurable disease, durable PFS (lack of progression ≥24 wk), PSA‐PFS, radiographic (r)PFS, overall survival (OS), and frequency/intensity of AEs. Results: 15 ARV7+ men were enrolled, with median f/u 8.4 (range 1.9–10.5) mo. Median age was 65, 47% had ECOG ≥1, median PSA was 115 ng/mL, 67% had visceral/n...
Severe radiation-related lymphopenia is common and associated with decreased survival in patients... more Severe radiation-related lymphopenia is common and associated with decreased survival in patients with several solid tumors. As the mechanisms underlying systemic lymphopenia are poorly understood, we developed an animal model to study the effects of brain radiation on lymphocytes and cytokines. C57 BL/6 and BALB/c mice received focal brain irradiation (4 Gy x 10 fractions or 2 Gy x 30 fractions). Weekly total lymphocyte counts (TLC), lymphocyte subsets and cytokines in blood and lymph nodes were measured. Non-irradiated lymph nodes were collected and examined before, during, and after radiation. We found that systemic TLC decreased rapidly irrespective of mouse strain or radiation schedule. 4 Gy x 10 resulted in a 42% and 75% & 70% and 49% TLC reduction in C57 BL/6 and BALB/c mice respectively. 2 Gy x 30 caused a 70% / 49% decrease in TLC in C57 BL/6 and BALB/c. Similar trends were seen for total T cells, CD4, regulatory T and CD8 cells. Changes in lymph node architecture and cellu...
This study evaluated the expression of PD-L1 and markers of immune mediated resistance in human m... more This study evaluated the expression of PD-L1 and markers of immune mediated resistance in human medulloblastoma (MB), the most common malignant pediatric brain tumor. Overall levels of PD-L1 in human MB were low; however, some cases demonstrated robust focal expression associated with increased immune infiltrates. The case with highest PD-L1 expression was a sonic hedgehog (SHH) MB. In cell lines, SHH MB, which are low-MYC expressing, demonstrated both constitutive and inducible expression of PD-L1 while those in Group 3/4 that expressed high levels of MYC had only inducible expression. , IFN-γ robustly stimulated the expression of PD-L1 in all cell lines while radiation induced variable expression. Forced high MYC expression did not significantly alter PD-L1. Human MB tumor samples were evaluated for expression of PD-L1 and immune cell markers in relation to molecular subgroup assignment. PD-L1 expression was functionally analyzed under conditions of interferon gamma (IFN-γ), radia...
Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Purpose: Multiple pre-clini... more Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Purpose: Multiple pre-clinical studies and case reports have described potential synergy between radiotherapy and immunotherapy, including checkpoint blockade with anti-PD1 and anti-CTLA-4 antibodies. However, further understanding of how radiotherapy contributes to immune mediated cell death, especially with regards to timing and dose per fraction, is needed to guide protocols for clinical trials. Here we investigated the development of radiation induced antigen-specific immune responses (RASIR) using stereotactic image guided small animal radiotherapy combined with anti-PD1 checkpoint blockade in a B16 melanoma model. Experimental Design: MC38 colorectal carcinoma, B16, and B16-OVA melanoma were cultured in complete RPMI media. A gamma-cell irradiator was used for in-vitro irradiation of cell suspensions. For in-vivo experiments 6-8 week old C57BL/6 mice were injected with 1x10^5 or 5x10^5 B16-OVA cells into the flank. Tumors were irradiated using a stereotactic CT guided small animal irradiator to treat a 1cmx1cm field prescribed to isocenter. For adoptive transfer experiments mice received 2x10^6 purified OT1 T-cells via retro-orbital injection. Anti-PD1 antibody was given intraperitoneally in three scheduled doses of 200ug. Cells were processed, stained, and analyzed by Flow cytometry on BD FACSCaliber or LSR II for indicated cell surface markers or intracellular cytokines. Results: We found that irradiation with 10Gy or 20Gy increased cell surface expression of MHC Class I, CCR7, CXCR3, and FAS in MC38 colorectal carcinoma and B16 melanoma at 24 and 48 Hours. We observed in-vivo that stereotactic radiotherapy of B16-OVA melanoma tumors increased CFSE labeled proliferation and Interferon-gamma activation of adoptively transferred OT1 T-cells in the draining lymph node and spleen. 18 Gy of radiotherapy resulted in increased activation and proliferation of antigen-specific T-cells when compared to 12Gy suggesting a possible dose response. Furthermore, when radiotherapy was combined with scheduled anti-PD1 antibody there was near eradication of B16-OVA melanoma tumors accompanied by increased development of endogenous antigen-specific immune responses. Conclusions: Radiotherapy increased expression of immunogenic cell surface markers in MC38 colorectal carcinoma and B16 melanoma. Stereotactic radiotherapy induced endogenous CD8 mediated antigen-specific immune responses when combined with scheduled anti-PD1 immunotherapy and resulted in near eradication of established B16-OVA melanoma. This study provides important pre-clinical evidence to support and guide clinical trials combining radiotherapy with anti-PD1 checkpoint blockade in melanoma. Future goals include analyzing development of RASIR using fractionated stereotactic radiotherapy with combined checkpoint blockade in multiple different tumor types. Citation Format: Andrew Sharabi, Christopher Nirschl, Tina Ceccato, Brian Francica, Angela Alme, Thomas Nirschl, Esteban Velarde, Theodore DeWeese, Charles Drake. Antigen-specific immune responses in melanoma using stereotactic radiotherapy combined with anti-PD1 checkpoint blockade. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 635. doi:10.1158/1538-7445.AM2014-635
The immune-modulating effects of radiotherapy (XRT) have gained considerable interest recently, a... more The immune-modulating effects of radiotherapy (XRT) have gained considerable interest recently, and there have been multiple reports of synergy between XRT and immunotherapy. However, additional preclinical studies are needed to demonstrate the antigen-specific nature of radiation-induced immune responses and elucidate potential mechanisms of synergy with immunotherapy. Here, we demonstrate the ability of stereotactic XRT to induce endogenous antigen-specific immune responses when it is combined with anti-PD-1 checkpoint blockade immunotherapy. Using the small animal radiation research platform (SARRP), image-guided stereotactic XRT delivered to B16-OVA melanoma or 4T1-HA breast carcinoma tumors resulted in the development of antigen-specific T cell- and B cell-mediated immune responses. These immune-stimulating effects of XRT were significantly increased when XRT was combined with either anti-PD-1 therapy or regulatory T cell (Treg) depletion, resulting in improved local tumor cont...
Intravesical BCG immunotherapy is the standard of care in treating non-muscle invasive bladder ca... more Intravesical BCG immunotherapy is the standard of care in treating non-muscle invasive bladder cancer, yet its mechanism of action remains elusive. Both innate and adaptive immune responses have been implicated in BCG activity. Although prior research has indirectly demonstrated the importance of T cells and shown a rise in CD4(+) T cells in bladder tissue after BCG, T-cell subpopulations have not been fully characterized. We investigated the relationship between effector and regulatory T cells in an immune competent, clinically relevant rodent model of bladder cancer. Our data demonstrate that cancer progression in the MNU rat model of bladder cancer was characterized by a decline in the CD8/FoxP3 ratio, consistent with decreased adaptive immunity. In contrast, treatment with intravesical BCG led to a large, transient rise in the CD4(+) T-cell population in the urothelium, and was both more effective and immunogenic compared to intravesical chemotherapy. Whole transcriptome ex...
5077 Background: GVAX-Prostate is a GM-CSF–secreting allogeneic cellular vaccine, whose immunogen... more 5077 Background: GVAX-Prostate is a GM-CSF–secreting allogeneic cellular vaccine, whose immunogenicity may be enhanced by androgen ablation as well as low-dose Cy. We conducted a neoadjuvant immunologic study comparing Deg vs. Cy/GVAX→Deg. Methods: Men with high-risk PCa (T1c–3b N0 M0, Gleason 7–10) were randomized 1:1 to Deg(240 mg SQ) vs. Cy(200 mg/m2 IV)/GVAX(2.5×108 PC3 cells, 1.6×108 LNCaP cells) given 2 wk before Deg; all pts then had RP 2 wk after Deg. CD8+ T cell and Treg densities in the primary tumor were quantified by IHC (cells/mm2). Clinical endpoints were time-to-PSA-relapse, time-to-next-therapy, and time-to-metastasis. The study was powered (α = 0.05, β = 0.18) to show a 2-fold increase in mean CD8+ density with Cy/GVAX→Deg (Arm B) vs. Deg (Arm A). Results: 28 men were enrolled (Arm A = 15, Arm B = 13). A concurrent control group (N = 20) who did not receive neoadjuvant therapy provided untreated RP tumor samples. Baseline variables were balanced across study arms: 6...
Radiotherapy (RT) enhances innate and adaptive antitumor immunity; however, the effects of radiat... more Radiotherapy (RT) enhances innate and adaptive antitumor immunity; however, the effects of radiation on suppressive immune cells, such as regulatory T cells (Treg), in the tumor microenvironment (TME) are not fully elucidated. Although previous reports suggest an increased Treg infiltration after radiation, whether these Tregs are functionally suppressive remains undetermined. To test the hypothesis that RT enhances the suppressive function of Treg in the TME, we selectively irradiated implanted tumors using the small animal radiation research platform (SARRP), which models stereotactic radiotherapy in human patients. We then analyzed tumor-infiltrating lymphocytes (TIL) with flow-cytometry and functional assays. Our data showed that RT significantly increased tumor-infiltrating Tregs (TIL-Treg), which had higher expression of CTLA-4, 4-1BB, and Helios compared with Tregs in nonirradiated tumors. This observation held true across several tumor models (B16/F10, RENCA, and MC38). We f...
AR-V7-expressing metastatic prostate cancer is an aggressive phenotype with poor progression-free... more AR-V7-expressing metastatic prostate cancer is an aggressive phenotype with poor progression-free survival (PFS) and overall survival (OS). Preliminary evidence suggests that AR-V7-positive tumors may be enriched for DNA-repair defects, perhaps rendering them more sensitive to immune-checkpoint blockade. We enrolled 15 metastatic prostate cancer patients with AR-V7-expressing circulating tumor cells into a prospective phase-2 trial. Patients received nivolumab 3 mg/kg plus ipilimumab 1 mg/kg every 3 weeks for four doses, then maintenance nivolumab 3 mg/kg every 2 weeks. Targeted next-generation sequencing was performed to determine DNA-repair deficiency (DRD) status. Outcomes included PSA response rates, objective response rates (ORR), PSA progression-free survival (PSA-PFS), clinical/radiographic PFS and OS. Median age of participants was 65, median PSA was 115 ng/mL, 67% had visceral metastases, and 60% had ≥4 prior systemic therapies. Six of 15 men (40%) had DRD mutations (three ...
Clinical cancer research : an official journal of the American Association for Cancer Research, Jan 13, 2018
In the proper context, radiation therapy (RT) can promote anti-tumor immunity. It is unknown if e... more In the proper context, radiation therapy (RT) can promote anti-tumor immunity. It is unknown if elective nodal irradiation (ENI), a strategy that irradiates tumor-associated draining lymph nodes (DLN), impacts adaptive immune responses and combinatorial efficacy of RT with immune checkpoint blockade (ICB). We developed a preclinical model to compare stereotactic RT (Tumor RT) with or without ENI to examine immunological differences between RT techniques that spare or irradiate the DLN. Tumor RT was associated with up-regulation of an intratumoral T-cell chemoattractant chemokine signature (CXCR3, CCR5-related) that resulted in robust infiltration of antigen-specific CD8+ effector T-cells as well as FoxP3+ regulatory T-cells (Tregs). The addition of ENI attenuated chemokine expression, restrained immune infiltration and adversely impacted survival when combined with ICB, especially with anti-CLTA4 therapy. The combination of stereotactic RT and ICB led to long-term survival in a subs...
BackgroundProstate cancer is the second leading cause of cancer related death in men in the Unite... more BackgroundProstate cancer is the second leading cause of cancer related death in men in the United States, mainly due to disease progression to metastatic castration-resistant prostate cancer (mCRPC). Although immunological treatment with the FDA-approved vaccine sipuleucel-T extends survival for 2–4 months by targeting the prostate-restricted antigen PAP, the identification of more immunogenic tumor-associated antigens (TAAs) continues to be an unmet need.MethodsWe evaluated the differential expression profile of the subset of epithelial cells reported to give rise to CRPC from mice following an androgen deprivation/repletion cycle. The expression levels of a set of androgen-responsive genes was further evaluated in prostate, brain, colon, liver, lung, and skin normal tissues from murine and human databases. The expression of a novel prostate-restricted TAA was then analyzed in primary tumors across all human cancer types in The Cancer Genome Atlas (TCGA). Finally, the immunogenici...
5035 Background: ARV7+ mCRPC is an aggressive phenotype with a median PFS of 3-4 mo and OS of 7-9... more 5035 Background: ARV7+ mCRPC is an aggressive phenotype with a median PFS of 3-4 mo and OS of 7-9 mo. We hypothesized that ARV7+ tumors would be enriched for DNA repair mutations, rendering them more responsive to combined immune checkpoint blockade. Methods: We enrolled 15 mCRPC pts with ARV7+ CTCs (using a CLIA-certified assay) into a single arm phase 2 study. Pts received Nivo 3 mg/kg plus Ipi 1 mg/kg every 3 wk x 4 doses, then maintenance Nivo 3 mg/kg every 2 wk. Targeted sequencing for DNA repair defects was performed on pretreatment tumor biopsies (n=11) or cell-free DNA (n=4). Primary endpoint: PSA50response rate. Secondary endpoints: objective response rate (ORR) in pts with measurable disease, durable PFS (lack of progression ≥24 wk), PSA‐PFS, radiographic (r)PFS, overall survival (OS), and frequency/intensity of AEs. Results: 15 ARV7+ men were enrolled, with median f/u 8.4 (range 1.9–10.5) mo. Median age was 65, 47% had ECOG ≥1, median PSA was 115 ng/mL, 67% had visceral/n...
Severe radiation-related lymphopenia is common and associated with decreased survival in patients... more Severe radiation-related lymphopenia is common and associated with decreased survival in patients with several solid tumors. As the mechanisms underlying systemic lymphopenia are poorly understood, we developed an animal model to study the effects of brain radiation on lymphocytes and cytokines. C57 BL/6 and BALB/c mice received focal brain irradiation (4 Gy x 10 fractions or 2 Gy x 30 fractions). Weekly total lymphocyte counts (TLC), lymphocyte subsets and cytokines in blood and lymph nodes were measured. Non-irradiated lymph nodes were collected and examined before, during, and after radiation. We found that systemic TLC decreased rapidly irrespective of mouse strain or radiation schedule. 4 Gy x 10 resulted in a 42% and 75% & 70% and 49% TLC reduction in C57 BL/6 and BALB/c mice respectively. 2 Gy x 30 caused a 70% / 49% decrease in TLC in C57 BL/6 and BALB/c. Similar trends were seen for total T cells, CD4, regulatory T and CD8 cells. Changes in lymph node architecture and cellu...
This study evaluated the expression of PD-L1 and markers of immune mediated resistance in human m... more This study evaluated the expression of PD-L1 and markers of immune mediated resistance in human medulloblastoma (MB), the most common malignant pediatric brain tumor. Overall levels of PD-L1 in human MB were low; however, some cases demonstrated robust focal expression associated with increased immune infiltrates. The case with highest PD-L1 expression was a sonic hedgehog (SHH) MB. In cell lines, SHH MB, which are low-MYC expressing, demonstrated both constitutive and inducible expression of PD-L1 while those in Group 3/4 that expressed high levels of MYC had only inducible expression. , IFN-γ robustly stimulated the expression of PD-L1 in all cell lines while radiation induced variable expression. Forced high MYC expression did not significantly alter PD-L1. Human MB tumor samples were evaluated for expression of PD-L1 and immune cell markers in relation to molecular subgroup assignment. PD-L1 expression was functionally analyzed under conditions of interferon gamma (IFN-γ), radia...
Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Purpose: Multiple pre-clini... more Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Purpose: Multiple pre-clinical studies and case reports have described potential synergy between radiotherapy and immunotherapy, including checkpoint blockade with anti-PD1 and anti-CTLA-4 antibodies. However, further understanding of how radiotherapy contributes to immune mediated cell death, especially with regards to timing and dose per fraction, is needed to guide protocols for clinical trials. Here we investigated the development of radiation induced antigen-specific immune responses (RASIR) using stereotactic image guided small animal radiotherapy combined with anti-PD1 checkpoint blockade in a B16 melanoma model. Experimental Design: MC38 colorectal carcinoma, B16, and B16-OVA melanoma were cultured in complete RPMI media. A gamma-cell irradiator was used for in-vitro irradiation of cell suspensions. For in-vivo experiments 6-8 week old C57BL/6 mice were injected with 1x10^5 or 5x10^5 B16-OVA cells into the flank. Tumors were irradiated using a stereotactic CT guided small animal irradiator to treat a 1cmx1cm field prescribed to isocenter. For adoptive transfer experiments mice received 2x10^6 purified OT1 T-cells via retro-orbital injection. Anti-PD1 antibody was given intraperitoneally in three scheduled doses of 200ug. Cells were processed, stained, and analyzed by Flow cytometry on BD FACSCaliber or LSR II for indicated cell surface markers or intracellular cytokines. Results: We found that irradiation with 10Gy or 20Gy increased cell surface expression of MHC Class I, CCR7, CXCR3, and FAS in MC38 colorectal carcinoma and B16 melanoma at 24 and 48 Hours. We observed in-vivo that stereotactic radiotherapy of B16-OVA melanoma tumors increased CFSE labeled proliferation and Interferon-gamma activation of adoptively transferred OT1 T-cells in the draining lymph node and spleen. 18 Gy of radiotherapy resulted in increased activation and proliferation of antigen-specific T-cells when compared to 12Gy suggesting a possible dose response. Furthermore, when radiotherapy was combined with scheduled anti-PD1 antibody there was near eradication of B16-OVA melanoma tumors accompanied by increased development of endogenous antigen-specific immune responses. Conclusions: Radiotherapy increased expression of immunogenic cell surface markers in MC38 colorectal carcinoma and B16 melanoma. Stereotactic radiotherapy induced endogenous CD8 mediated antigen-specific immune responses when combined with scheduled anti-PD1 immunotherapy and resulted in near eradication of established B16-OVA melanoma. This study provides important pre-clinical evidence to support and guide clinical trials combining radiotherapy with anti-PD1 checkpoint blockade in melanoma. Future goals include analyzing development of RASIR using fractionated stereotactic radiotherapy with combined checkpoint blockade in multiple different tumor types. Citation Format: Andrew Sharabi, Christopher Nirschl, Tina Ceccato, Brian Francica, Angela Alme, Thomas Nirschl, Esteban Velarde, Theodore DeWeese, Charles Drake. Antigen-specific immune responses in melanoma using stereotactic radiotherapy combined with anti-PD1 checkpoint blockade. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 635. doi:10.1158/1538-7445.AM2014-635
The immune-modulating effects of radiotherapy (XRT) have gained considerable interest recently, a... more The immune-modulating effects of radiotherapy (XRT) have gained considerable interest recently, and there have been multiple reports of synergy between XRT and immunotherapy. However, additional preclinical studies are needed to demonstrate the antigen-specific nature of radiation-induced immune responses and elucidate potential mechanisms of synergy with immunotherapy. Here, we demonstrate the ability of stereotactic XRT to induce endogenous antigen-specific immune responses when it is combined with anti-PD-1 checkpoint blockade immunotherapy. Using the small animal radiation research platform (SARRP), image-guided stereotactic XRT delivered to B16-OVA melanoma or 4T1-HA breast carcinoma tumors resulted in the development of antigen-specific T cell- and B cell-mediated immune responses. These immune-stimulating effects of XRT were significantly increased when XRT was combined with either anti-PD-1 therapy or regulatory T cell (Treg) depletion, resulting in improved local tumor cont...
Intravesical BCG immunotherapy is the standard of care in treating non-muscle invasive bladder ca... more Intravesical BCG immunotherapy is the standard of care in treating non-muscle invasive bladder cancer, yet its mechanism of action remains elusive. Both innate and adaptive immune responses have been implicated in BCG activity. Although prior research has indirectly demonstrated the importance of T cells and shown a rise in CD4(+) T cells in bladder tissue after BCG, T-cell subpopulations have not been fully characterized. We investigated the relationship between effector and regulatory T cells in an immune competent, clinically relevant rodent model of bladder cancer. Our data demonstrate that cancer progression in the MNU rat model of bladder cancer was characterized by a decline in the CD8/FoxP3 ratio, consistent with decreased adaptive immunity. In contrast, treatment with intravesical BCG led to a large, transient rise in the CD4(+) T-cell population in the urothelium, and was both more effective and immunogenic compared to intravesical chemotherapy. Whole transcriptome ex...
5077 Background: GVAX-Prostate is a GM-CSF–secreting allogeneic cellular vaccine, whose immunogen... more 5077 Background: GVAX-Prostate is a GM-CSF–secreting allogeneic cellular vaccine, whose immunogenicity may be enhanced by androgen ablation as well as low-dose Cy. We conducted a neoadjuvant immunologic study comparing Deg vs. Cy/GVAX→Deg. Methods: Men with high-risk PCa (T1c–3b N0 M0, Gleason 7–10) were randomized 1:1 to Deg(240 mg SQ) vs. Cy(200 mg/m2 IV)/GVAX(2.5×108 PC3 cells, 1.6×108 LNCaP cells) given 2 wk before Deg; all pts then had RP 2 wk after Deg. CD8+ T cell and Treg densities in the primary tumor were quantified by IHC (cells/mm2). Clinical endpoints were time-to-PSA-relapse, time-to-next-therapy, and time-to-metastasis. The study was powered (α = 0.05, β = 0.18) to show a 2-fold increase in mean CD8+ density with Cy/GVAX→Deg (Arm B) vs. Deg (Arm A). Results: 28 men were enrolled (Arm A = 15, Arm B = 13). A concurrent control group (N = 20) who did not receive neoadjuvant therapy provided untreated RP tumor samples. Baseline variables were balanced across study arms: 6...
Radiotherapy (RT) enhances innate and adaptive antitumor immunity; however, the effects of radiat... more Radiotherapy (RT) enhances innate and adaptive antitumor immunity; however, the effects of radiation on suppressive immune cells, such as regulatory T cells (Treg), in the tumor microenvironment (TME) are not fully elucidated. Although previous reports suggest an increased Treg infiltration after radiation, whether these Tregs are functionally suppressive remains undetermined. To test the hypothesis that RT enhances the suppressive function of Treg in the TME, we selectively irradiated implanted tumors using the small animal radiation research platform (SARRP), which models stereotactic radiotherapy in human patients. We then analyzed tumor-infiltrating lymphocytes (TIL) with flow-cytometry and functional assays. Our data showed that RT significantly increased tumor-infiltrating Tregs (TIL-Treg), which had higher expression of CTLA-4, 4-1BB, and Helios compared with Tregs in nonirradiated tumors. This observation held true across several tumor models (B16/F10, RENCA, and MC38). We f...
AR-V7-expressing metastatic prostate cancer is an aggressive phenotype with poor progression-free... more AR-V7-expressing metastatic prostate cancer is an aggressive phenotype with poor progression-free survival (PFS) and overall survival (OS). Preliminary evidence suggests that AR-V7-positive tumors may be enriched for DNA-repair defects, perhaps rendering them more sensitive to immune-checkpoint blockade. We enrolled 15 metastatic prostate cancer patients with AR-V7-expressing circulating tumor cells into a prospective phase-2 trial. Patients received nivolumab 3 mg/kg plus ipilimumab 1 mg/kg every 3 weeks for four doses, then maintenance nivolumab 3 mg/kg every 2 weeks. Targeted next-generation sequencing was performed to determine DNA-repair deficiency (DRD) status. Outcomes included PSA response rates, objective response rates (ORR), PSA progression-free survival (PSA-PFS), clinical/radiographic PFS and OS. Median age of participants was 65, median PSA was 115 ng/mL, 67% had visceral metastases, and 60% had ≥4 prior systemic therapies. Six of 15 men (40%) had DRD mutations (three ...
Clinical cancer research : an official journal of the American Association for Cancer Research, Jan 13, 2018
In the proper context, radiation therapy (RT) can promote anti-tumor immunity. It is unknown if e... more In the proper context, radiation therapy (RT) can promote anti-tumor immunity. It is unknown if elective nodal irradiation (ENI), a strategy that irradiates tumor-associated draining lymph nodes (DLN), impacts adaptive immune responses and combinatorial efficacy of RT with immune checkpoint blockade (ICB). We developed a preclinical model to compare stereotactic RT (Tumor RT) with or without ENI to examine immunological differences between RT techniques that spare or irradiate the DLN. Tumor RT was associated with up-regulation of an intratumoral T-cell chemoattractant chemokine signature (CXCR3, CCR5-related) that resulted in robust infiltration of antigen-specific CD8+ effector T-cells as well as FoxP3+ regulatory T-cells (Tregs). The addition of ENI attenuated chemokine expression, restrained immune infiltration and adversely impacted survival when combined with ICB, especially with anti-CLTA4 therapy. The combination of stereotactic RT and ICB led to long-term survival in a subs...
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Papers by Thomas Nirschl