Abstract C044: MICAL2 expression in pancreatic cancer cells modulates the tumor microenvironment through the TGF beta pathway
Authors: Garg Bharti , Sharma Shweta , Khan Sohini , Esparza Edgar , Sass Sarah , Jacquish Dawn , Mose Evangeline , Tiriac Herve , Lowy Andrew 
Published: November 2022

Introduction: Pancreatic cancer is characterized by a desmoplastic, fibroinflammatory stroma. The crosstalk between cancer cells and their surrounding tumor microenvironment (TME) promotes disease progression, metastasis, and chemoresistance. We identified MICAL2 as a super-enhancer associated gene in pancreatic cancer. MICAL2 (molecule interacting with Cas-L) proteins are Flavin monooxygenases that promotes actin depolymerization and indirectly regulate SRF transcription. In other work, we have found that MICAL2 promotes pancreatic cancer growth and progression. In this study, we evaluated how MICAL2 pancreatic cancer cell expression modulates the PDAC tumor microenvironment. Methods: RNA-Seq analysis performed on human pancreas cancer cells (AsPC) before and after MICAL2 knockdown revealed differential regulation of TGF-β and other proinflammatory cytokines. We validated the expression of TGF-β and other potent cytokines in multiple human and mouse pancreas cancer cell lines by q-PCR. We next exposed human and mouse pancreatic stellate cells (PSCs) to conditioned media from cancer cells before and after MICAL2 knockdown and checked the expression of TGF-β responsive genes by qPCR. KrasG12D/+; Trp53R172H/+; Pdx1-cre (KPC) cells with and without MICAL2 were orthotopically injected to assess the in vivo tumor growth and metastasis. We sorted epithelial cells and CAFs from KPC orthotopic tumors with and without MICAL2 by using EPCAM, PDGFR, and PDPN markers. Results: MICAL2 knockdown (KD) resulted in downregulation of TGF-β gene in both human and mouse pancreas cancer cell lines (50% reduction, p&lt;0.05). Human hPSCs and mouse mPSCs co-cultured with pancreatic cancer cells showed a significant downregulation of myofibroblastic and inflammatory CAFs genes including a-SMA, fibronectin, IL1α and IL6 upon MICAL2 KD as compared to hPSCs and mPSCs co-cultured with shcontrol cells. Orthotopic injections of KPC MICAL2 KD cells led to decreased tumor growth as compared to shcontrol (0.26 gm vs. 1 gm, p = 0.008). Our Immunofluorescence revealed less collagen deposition and α-SMA expression and reduced secretion of IL6 by stromal cells in MICAL2 KD tumors. Flow sorting showed less percentage of epithelial and CAF population in MICAL2 KD orthotopic tumors as compared to Shcontrol tumors. A qPCR analysis of the sorted populations showed less expression of TGF-β on epithelial cells and reduced expression of IL6 on PDGFRα/PDPN+ CAFs extracted from MICAL2 KD tumors as compared to control tumors. Conclusion: These data reveal that MICAL2 expression mediates tumor-stromal crosstalk through TGF- β. Ongoing work is focused on dissecting the role of MICAL2 in priming the metastatic niche through remodeling of the TME.

Citation Format: Bharti Garg, Shweta Sharma, Sohini Khan, Edgar Esparza, Sarah Sass, Dawn Jacquish, Evangeline Mose, Herve Tiriac, Andrew Lowy. MICAL2 expression in pancreatic cancer cells modulates the tumor microenvironment through the TGF beta pathway [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C044.