Elevated levels of TGF-β are a negative prognostic indicator for patients diagnosed with pancreatic cancer; as a result the TGF-β pathway is an attractive target for therapy. However, clinical application of pharmacologic inhibition of TGF-β remains challenging because TGF-β has tumor suppressor functions in many epithelial malignancies including pancreatic cancer. In fact, direct neutralization of TGF-β promotes tumor progression of genetic murine models of pancreatic cancer. Here we report that neutralizing the activity of murine TGF-β receptor 2 using a monoclonal antibody (2G8) has potent anti-metastatic activity in orthotopic human tumor xenografts, syngenic tumors and a genetic model of pancreatic cancer. 2G8 reduced activated fibroblasts, collagen deposition, microvessel density and vascular function. These stromal specific changes resulted in tumor cell epithelial differentiation and a potent reduction in metastases. We conclude that TGF-β signaling within stromal cells participates directly in tumor cell phenotype and pancreatic cancer progression. Thus, strategies that inhibit TGF-β dependent effector functions of stromal cells could be efficacious for the therapy of pancreatic tumors.

Background:We examined the impact of insulin-like growth factor binding protein-4 (IGFBP-4) on growth factor-induced angiogenesis in vivo. Results: IGFBP-4 inhibited IGF-1 and FGF-2, but not VEGF-induced angiogenesis, and this inhibition depended on p38 MAPK activity. Conclusion:The anti-angiogenic activity of IGFBP-4 depends in part on p38 MAPK. Significance: New insight is provided into how blood vessels respond to endogenous inhibitors during growth factor-stimulated angiogenesis.

TGFβ signaling is known to play a central role in tumor biology, via inducing and/or enhancing tumor cell growth and differentiation, modulating the extracellular matrix in the stroma, inducing epithelial to mesenchymal transition, modulating angiogenesis, and inhibiting immune surveillance and anti-tumor immunity. Galunisertib is a pharmacological inhibitor of the TGFβ pathway which acts by inhibiting signaling though TGFβRI. Galunisertib is currently being evaluated clinically in several Phase I and II studies; as a monotherapy, galunisertib has shown antitumor activity against a variety of tumors, including durable and long-term responses in patients with glioma.To explore the impact of Galunisertib monotherapy on anti-tumor T cell immunity, we utilized murine tumor models. Treatment of mice with well-established 4T1-LP (poorly immunogenic 4T1 breast tumor engineered to express luciferase) implanted in the mammary fat pad resulted in strong dose-dependent anti-tumor activity with nearly 100% inhibition of tumor growth across doses during the dosing period, with complete tumor responses upon cessation of treatment in~50% of animals at the highest dose tested; depletion studies demonstrated that regression of 4T1-LP was dependent on the presence of CD8+ T cells. Rechallenge of treated, tumor free mice resulted in complete rejection of 4T1-LP tumor cells but no rejection of EMT6-LM2 tumor cells, demonstrating the establishment of a durable response and immunological memory. Treatment of mice bearing established parental 4T1 tumors in the mammary fat pad resulted in no significant inhibition of tumor growth, indicating that the presence of a foreign antigen (i.e. LP), potentially enhanced the ability to regress the 4T1-LP derivative. Animals that rejected the immunogenic 4T1-LP tumors were able to also reject 4T1 parental cells upon rechallenge, suggesting the development of a secondary immune response via antigen spreading as a consequence of effective tumor targeting. In the CT26 murine colon carcinoma model, treatment of established tumors with galunisertib or anti-PD-L1 as monotherapies resulted in tumor growth inhibition compared to control of 75% and 86%, respectively (T/C values of 25% and 14%); complete responders were observed in about 20% of treated animals in both monotherapy groups. Combination of galunisertib with anti-PD-L1 resulted in an enhanced tumor growth inhibition of 98% (T/C value of~2%), and a complete response rate of 50%, suggesting at least additive activity with potential for synergy when targeting the TGFβ and PD-1 pathways. Taken together, these data demonstrate the potential for galunisertib treatment to enhance the development of antitumor T cell immunity, which can be enhanced by combinations with immune check point inhibitors.

<p>Supplemental Materials and Methods. Description of additional methods and procedures used in the study.</p>

<div>Abstract<p>Elevated levels of TGFβ are a negative prognostic indicator for patients diagnosed with pancreatic cancer; as a result, the TGFβ pathway is an attractive target for therapy. However, clinical application of pharmacologic inhibition of TGFβ remains challenging because TGFβ has tumor suppressor functions in many epithelial malignancies, including pancreatic cancer. In fact, direct neutralization of TGFβ promotes tumor progression of genetic murine models of pancreatic cancer. Here, we report that neutralizing the activity of murine TGFβ receptor 2 using a monoclonal antibody (2G8) has potent antimetastatic activity in orthotopic human tumor xenografts, syngeneic tumors, and a genetic model of pancreatic cancer. 2G8 reduced activated fibroblasts, collagen deposition, microvessel density, and vascular function. These stromal-specific changes resulted in tumor cell epithelial differentiation and a potent reduction in metastases. We conclude that TGFβ signaling within stromal cells participates directly in tumor cell phenotype and pancreatic cancer progression. Thus, strategies that inhibit TGFβ-dependent effector functions of stromal cells could be efficacious for the therapy of pancreatic tumors. <i>Cancer Res; 74(18); 4996–5007. ©2014 AACR</i>.</p></div>