Reciprocal interactions between tumor cells and their microenvironment vitally impact tumor progression. In this study, we show that GM-CSF produced by primary breast tumor cells induced the activation of plasmacytoid pre-dendritic cells (pDC), a cell type critical to anti-viral immunity. pDC that expressed the GM-CSF receptor were increased in breast tumors compared to non-involved adjacent breast tissue. Tumor-activated pDC acquired naive CD4+ T cell stimulatory capacity and promoted a regulatory Th2 response. Lastly, the concomitant increase of GM-CSF and pDC was significantly associated with relatively more aggressive breast cancer subtypes. Our results characterize the first tumor-derived factor that can activate pDC to promote a regulatory Th2 response, with implications for therapeutic targeting of a tumor-immune axis of growing recognition in its significance to cancer.

Adenoviruses have been clinically tested as anticancer therapies but their utility has been severely limited by rapid, systemic cytokine release and consequent inflammatory toxicity. Here, we describe a new approach to tackling these dangerous side effects. Using human ovarian cancer cell lines as well as malignant epithelial cells harvested from the ascites of women with ovarian cancer, we show that tumor cells do not produce cytokines in the first 24 hours following in vitro infection with the oncolytic adenovirus dl922-947. In contrast, dl922-947 does induce inflammatory cytokines at early time points following intraperitoneal delivery in mice with human ovarian cancer intraperitoneal xenografts. In these animals, cytokines originate predominantly in murine tissues, especially in macrophage-rich organs such as the spleen. We use a nonreplicating adenovirus to confirm that early cytokine production is independent of adenoviral replication. Using β3 integrin knockout mice injected intraperitoneally with dl922-947 and β3 null murine peritoneal macrophages, we confirm a role for macrophage cell surface β3 integrin in this dl922-947–induced inflammation. We present new evidence that co-administration of a cyclic RGD-mimetic–specific inhibitor of β3 integrin significantly attenuates the cytokine release and inflammatory hepatic toxicity induced by dl922-947 in an intraperitoneal murine model of ovarian cancer. Importantly, we find no evidence that β3 inhibition compromises viral infectivity and oncolysis in vitro or anticancer efficacy in vivo. By enabling safe, systemic delivery of replicating adenoviruses, this novel approach could have a major impact on the future development of these effective anticancer agents. Cancer Res; 75(14); 1–11. ©2015 AACR.

Adenoviruses have been clinically tested as anti-cancer therapies but their utility has been severely limited by rapid, systemic cytokine release and consequent inflammatory toxicity. Here we describe a new approach to tackling these dangerous side effects. Using human ovarian cancer cell lines as well as malignant epithelial cells harvested from the ascites of women with ovarian cancer, we show that tumour cells do not produce cytokines in the first 24 hours following in vitro infection with the oncolytic adenovirus dl922-947. In contrast, dl922-947 does induce inflammatory cytokines at early time points following intraperitoneal (IP) delivery in mice with human ovarian cancer IP xenografts. In these animals, cytokines originate predominantly in murine tissues, especially in macrophage-rich organs such as the spleen. We use a non-replicating adenovirus to confirm that early cytokine production is independent of adenoviral replication. Using beta3 integrin knockout mice injected IP with dl922-947 and beta3 null murine peritoneal macrophages we confirm a role for macrophage cell surface beta3 integrin in this dl922-947-induced inflammation. We present new evidence that co-administration of a cyclic RGD-mimetic specific inhibitor of beta3 integrin significantly attenuates the cytokine release and inflammatory hepatic toxicity induced by dl922-947 in an IP murine model of ovarian cancer. Importantly, we find no evidence that beta3 inhibition compromises viral infectivity and oncolysis in vitro or anticancer efficacy in vivo. By enabling safe, systemic delivery of replicating adenoviruses, this novel approach could have a major impact on the future development of these effective anti-cancer agents.

Antibodies that block the interaction between programmed death ligand 1 (PD-L1) and PD-1 have shown impressive antitumor activity. Patients with tumors expressing PD-L1 are most likely to respond to this treatment. The aim of our study was to develop a noninvasive imaging technique to determine tumor PD-L1 expression in vivo. This could allow selection of patients that are most likely to benefit from anti–PD-1/PD-L1 treatment and to monitor PD-L1 expression during therapy. The monoclonal antibody PD-L1.3.1 was radiolabeled with Indium-111 (111In) and characterized using PD-L1–expressing MDA-MB-231 cells. Subsequently, the optimal antibody dose and time point for imaging was determined in mice with MDA-MB-231 xenografts. Finally, SPECT/CT imaging was performed in xenograft models with different PD-L1 expression levels and tumor sections were analyzed for PD-L1 expression using IHC. The optimal antibody dose of 111In-PD-L1.3.1 (K
d = 1 nmol/L) for SPECT/CT imaging was ≤1 μg. Highest tumor-to-normal tissue contrast was obtained at days 3 and 7 after injection. 111In-PD-L1.3.1 SPECT/CT showed efficient accumulation in high PD-L1–expressing tumors (MDA-MB-231 and SK-Br-3), whereas no specific uptake was observed in tumors with low or no detectable levels of PD-L1 (SUM149, BT474, and MCF-7). SPECT/CT and autoradiography showed a very heterogeneous distribution of 111In-PD-L1.3.1 within the tumor. In conclusion, this is the first study showing the feasibility of noninvasive in vivo imaging of PD-L1 expression in tumors. 111In-PD-L1.3.1 showed efficient and specific uptake in PD-L1 expressing xenografts. This technique may enable patient selection for PD-1 and PD-L1–targeted therapy. Cancer Res; 75(14); 1–9. ©2015 AACR.

Antibodies that block the interaction between programmed death ligand 1 (PD-L1) and PD-1 have shown impressive anti-tumor activity. Patients with tumors expressing PD-L1 are most likely to respond to this treatment. The aim of our study was to develop a noninvasive imaging technique to determine tumor PD-L1 expression in vivo. This could allow selection of patients that are most likely to benefit from anti-PD-1/PD-L1 treatment and to monitor PD-L1 expression during therapy. The monoclonal antibody PD-L1.3.1 was radiolabeled with Indium-111 (111In) and characterized using PD-L1 expressing MDA-MB-231 cells. Subsequently, the optimal antibody dose and time point for imaging was determined in mice with MDA-MB-231 xenografts. Finally, SPECT/CT imaging was performed in xenograft models with different PD-L1 expression levels and tumor sections were analyzed for PD-L1 expression using immunohistochemistry. The optimal antibody dose of 111In-PD-L1.3.1 (Kd = 1 nM) for SPECT/CT imaging was ≤ 1 µg. Highest tumor-to-normal tissue contrast was obtained at day 3 and 7 post injection. 111In-PD-L1.3.1 SPECT/CT showed efficient accumulation in high PD-L1 expressing tumors (MDA-MB-231, SK-Br-3), while no specific uptake was observed in tumors with low or no detectable levels of PD-L1 (SUM149, BT474, MCF-7). SPECT/CT and autoradiography showed a very heterogeneous distribution of 111In-PD-L1.3.1 within the tumor. In conclusion, this is the first study showing the feasibility of non-invasive in vivo imaging of PD-L1 expression in tumors. 111In-PD-L1.3.1 showed efficient and specific uptake in PD-L1 expressing xenografts. This technique may enable patient selection for PD-1 and PD-L1 targeted therapy.