Abstract 110: Modulation of cancer-associated fibrotic stroma reduces pathological progression of PDAC

Background: Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with a five-year survival rate of just 9% after diagnosis. Despite large efforts in developing treatments, the outcome of therapies for patient survival only improves marginally. Dense fibrotic stroma and ECM orchestrated by cancer-associated pancreatic stellate cells (CAPaSC) is considered to be one of the major contributors of resistance to anti-tumor therapies in this disease. The presence of dense collagen fibrils forms a physical block to drug delivery and the completely collapsed intratumoral blood vessels lead to poor blood perfusion resulting in treatment failure. CAPaSC also engage in symbiotic “cross-talk” with cancer cells through cytokines, growth factors, and chemokines supporting cancer cell growth, survival, and resistance to apoptosis. In turn, cancer cells provide factors that support pancreatic stellate cells (PaSC) proliferation and survival. PaSC upon activation express high levels of integrin αVβ3. We previously reported the development of a protein, ProAgio that targets integrin αVβ3 at a novel site and induces apoptosis of integrin αVβ3 expressing cells. We demonstrate here that ProAgio specifically induces apoptosis of CAPaSC and reduces collagen in the pancreatic tumor, enabling delivery of drug molecules into the tumor. Objective: To test whether targeting CAPaSC reduces the pathological progression of PDAC in murine models. Methods: We examined the effects of ProAgio in vitro and in a xenograft mouse model in vivo wherein Panc-1 cells were co-implanted with immortalized and activated human PaSC. Further, we used two murine PDAC models: a) Genetically engineered mouse (GEM) KPC model, and, b) KP orthotopic mouse model where KPC cells were orthotopically injected into the pancreas. Mice were treated with 20 doses of ProAgio (10mg/kg; i.p.). Tumor histological analysis was performed. Drug diffusion was measured by administering Fluor 595-conjugated goat IgG via tail vein. Results: PaSC promoted the growth of pancreatic cancer cells in vitro. Integrin αVβ3 is highly upregulated in CAPaSC and ProAgio effectively induced apoptosis of CAPaSC. ProAgio treatment markedly inhibited the tumor growth when Panc-1 cells were co-implanted with activated human PaSC. In more clinically relevant models, such as GEM KPC and KP orthotopic mouse models, ProAgio treatment exhibited around 60-70% decrease in α-SMA positive cells and intratumoral collagen levels. In addition, ProAgio treatment decompressed the intratumoral vessels without an increase in angiogenesis and significantly increased the delivery of drug into the tumor. In conclusion, our findings for the first time demonstrate that ProAgio may potentially be a unique agent that is capable of specifically depleting CAPaSC in PDAC to facilitate treatment. Citation Format: Malvika Sharma, Ravi Chakra Turaga, Falguni Mishra, Yi Yuan, Zhi-Ren Liu. Modulation of cancer-associated fibrotic stroma reduces pathological progression of PDAC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 110.