Abstract 2636: Tumor associated MUC1 mediates TGF-β in pancreatic cancer

Abstract

Abstract Pancreatic Cancer (PC) is the third leading cause of cancer-related deaths in the United States, with a five-year survival rate at 9%. Over 90% of PC is categorized as Pancreatic Ductal Adenocarcinoma (PDA). 85% of PDA overexpress tumor associated Mucin-1 (tMUC1), a membrane bound glycoprotein that is aberrantly glycosylated. Overexpression of tMUC1 in PDA plays a critical role in tumor progression and metastasis by promoting oncogenic signaling through its cytoplasmic tail (tMUC1-CT). Transforming growth factor-β (TGF-β) plays pleiotropic roles during cancer development and progression. Within normal cells and early carcinogenesis, TGF-β functions as a tumor suppressor and induces apoptosis. This effect is mediated by activation of the canonical SMAD pathway via engagement of TGF-β Receptor 1 (TGF-βRI). However, during later stages of cancer, TGF-β becomes a tumor promoter and stimulates epithelial to mesenchymal transition (EMT), migration, and invasion thus enhancing metastasis through the non-canonical Erk1/2 pathway. We have shown that high tMUC1 expressing PDA cells respond to TGF-β via activation of the non-canonical pathway and undergoes EMT whereas, low tMUC1 expressing PDA cells respond to TGF-β via activation of the canonical SMAD pathway and undergoes apoptosis. tMUC1 plays a key role in regulating TGF-β’s dual function in PDA. We hypothesize that signaling via tMUC1-CT enables TGF-β function to switch from a tumor suppressor to a tumor promoter. The effects of TGF-β1 to induce apoptosis versus proliferation and invasiveness was determined in a panel of tMUC1 high and low PDA cell lines. Analysis of apoptosis and cell cycle was conducted using flow cytometry, while invasiveness was determined using the Boyden chamber assay. Proteins levels were determined using western blot. TGF-β pathway genes were studied in patient data collected from GTEx (healthy, n=171) and TCGA (PDA, n=178). It was compared using Pearson's correlation coefficient. Finally, we determined the anti-tumor efficacy of neutralizing TGF-β1 in vivo in high and low tMUC1-expressing PDA tumors. In response to TGF-β, tMUC1 high PDA cells resisted apoptosis, enhanced invasiveness, and activated the Erk pathway, while tMUC1 low cells became apoptotic and activated the SMAD pathway. Cell cycle analysis confirms a significant increase in apoptosis in tMUC1 low PDA cells, however tMUC1 high PDA cells resist TGF-β induced apoptosis. Signal transduction was dependent upon tyrosine phosphorylation of tMUC1-CT domain by Src. RNA-Seq analysis in TCGA PDA tissue reveal eight genes that show significant correlation (low p-value OR p-value < 0.05) while it was insignificant in the GTEx healthy tissue. Finally, in mice, tMUC1-high PDA tumors responded to the neutralization of TGF-β1 by significantly reducing tumor growth, while having no effect on tMUC1-low PDA tumors. tMUC1 expression levels in PDA may serve as a marker for eligibility for potential anti-TGF-β therapies. Citation Format: Priyanka Grover, Ru Zhou, Mahboubeh Yazdanifar, Mohammad Ahmad, Angat Puri, Kajal Grover, Xinghua Shi, Pinku Mukherjee. Tumor associated MUC1 mediates TGF-β in pancreatic cancer [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 2636.