Abstract B208: Targeting ITGA5 in pancreatic stellate cells as a novel strategy to restrain pancreatic tumor growth

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Abstract Pancreatic ductal adenocarcinoma (PDAC) is the deadliest tumor type with a 5-year survival rate of less than 5%. PDAC is characterized by abundant desmoplastic stroma, driving tumor progression and metastasis. Cancer-associated fibroblasts (CAFs) are the key pro-tumorigenic stromal cells in pancreatic tumor, mainly derived from pancreatic stellate cells (PSCs). In this study, we identified integrin alpha5 (ITGA5) as a novel target overexpressed in PSCs and studied the value of ITGA5 as a prognostic and therapeutic target in pancreatic cancer. Then, we designed a novel peptide against ITGA5 and investigated its therapeutic effects in vitro and in vivo. In human patient tumor samples (n=137), 66% of the patients were positive for ITGA5 and the expression of ITGA5 was co-localized with α-SMA, as shown with immunostaining. Overall, clinical data analysis revealed that the overexpression of ITGA5 (log-rank p=0.022) was significantly linked to poor overall survival. In vitro, activation of human PSCs (hPSCs) with TGF-β1 significantly induced ITGA5 expression in PSCs. Importantly, knockdown of ITGA5 in PSCs led to a dramatic reduction of ECM proteins and other fibrotic markers (RT2 profiler array), when activated with TGFβ. Next, knockdown (KD) of ITGA5 in hPSCs led to the reprogramming of their phenotype, as shown of the reduced proliferation and TGF-β induced contractility. The reprogramming of ITGA5-KD hPSCs was at least attributed to the inhibition of FAK, Smad2 and AKT signaling. Next, ITGA5-KD-PSCs showed lower migration compared to Ctr-shRNA-PSCs, attributed to loss of FAK, Rac, Cdc4 signaling. Furthermore, ITGA5-KD-PSCs had a substantial decrease in cell adhesion and 3D spheroid formation compared to control shRNA-PSCs. In vivo, coinjection of Panc-1 and hPSCs in SCID mice showed an increased fibrosis and tumor growth compared to Panc-1 tumors. Interestingly, tumors formed with Panc-1+ hPSCs (ITGA5-KD) had a reduced fibrosis and tumor progression. Then, we examined our novel peptide against ITGA5 in vitro and found a strong inhibition of TGF-β-mediated differentiation and phenotypic changes of PSCs. Intriguingly, treatment of the coinjection (Panc-1 + PSC) tumors with the peptide either intratumoral or i.p. twice a week significantly reduced the tumor growth. The reduced tumor growth might be attributed to the reduction in fibroblasts compared to vehicle groups, as shown with desmin expression. In conclusion, we demonstrate that ITGA5 is a key prognostic and therapeutic target in pancreatic tumor stroma and that inhibition of ITGA5 with our novel peptide could be a promising approach to abolish pancreatic tumor progression. Citation Format: Praneeth Kuninty, Sanne de Geus, Ruchi Bansal, Jonas Schnittert, Peter Kuppen, Alexander Vahrmeijer, Arne Ostman, Cornelies Sier, Jai Prakash. Targeting ITGA5 in pancreatic stellate cells as a novel strategy to restrain pancreatic tumor growth [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B208.

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