Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant tumor characterized by intrinsic or rapidly acquired chemoresistance. The remarkable desmoplastic response has been reported as a major contributor to chemoresistance, suggesting that PDAC progression could be highly influenced by mechanical factors (1). A recent study showed a key role of epithelial tension and matricellular fibrosis in the aggressiveness of SMAD4 mutant PDAC (2). Here we aimed at evaluating new mechanopharmacology approaches to overcome chemoresistance. PDAC cells attached to collagen and fibronectin showed a decreased sensitivity to chemotherapy, while the malignant phenotype was highly correlated to α2β1 integrin(ITGA2)-mediated adhesion to type I collagen (3). We hence hypothesized that this integrin might modulate chemoresistance. In two cohorts of 50 radically resected patients treated with gemcitabine, high expression of ITGA2 (assessed by immunohistochemistry in tissue-microarrays with 4 cores for each tumor) correlated to significantly shorter progression and overall free survival. Our hypothesis was further investigated in a gemcitabine-resistant clone (PANC1-R). In this clone, ITGA2 was among the top 10 most differentially upregulated genes at next-generation sequencing analysis. Using migration assays, we found that PANC1-R were more invasive than PANC1 cells, and a specific siRNA for ITGA2 caused a significant reduction of invasiveness while enhancing both gemcitabine antiproliferative effects and apoptosis induction. Using elastic micropillar arrays of varying stiffness (20-150kPa) (4), we observed delayed spreading of PANC1-R compared to PANC1 while a 24-hour treatment with a non-cytotoxic dose of gemcitabine activated traction forces in both lines, albeit to a lesser extent in PANC1-R. Remarkably, these cells showed also a significant increase of CXCR4 and MMP2 expression when growing in spheroids embedded in stiff collagen, as well as a different trend in modulation of E2F1 after exposure to gemcitabine, when growing as 2D collagen monolayers on soft and stiff flat PDMS, suggesting that aggressive/invasive behavior and response to gemcitabine are altered by both collagen and stiffness. These results define ITGA2 as a new prognostic factor, exerting its function through the promotion of metastatic behavior and altered drug response of PDAC cells under differential biomechanical conditions, which holds a potential as a novel therapeutic target to overcome PDAC resistance.

References:

1. Coppola et al. Drug Resist Updates 2017;31:43.

2. Laklai et al. Nat Med 2016;22:497.

3. Grzesiak, Bouvet. Br J Cancer 2016;94:1311.

4. van Hoorn et al. Nano Lett 2014;14:4257.

Citation Format: Ilaria Carnevale, Stefano Coppola, Niccola Funel, Erik H. Danen, Thomas Schmidt, Elisa Giovannetti. α2β1 integrins are potential regulators of chemoresistance through modulation of biomechanical cues in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4040.