Abstract 3714: Role of miR-29a in pancreatic stellate cell mediated stromal remodeling in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive form of malignancy with nearly equal incidence and mortality rates in patients. The disease is characterized by dense desmoplastic tumor-associated stroma, which prevents effective therapeutic delivery to the tumor core and confers resistance to chemotherapy. The central effectors of such characteristic stroma in PDAC are the pancreatic stellate cells (PSCs), which are activated by autocrine and paracrine signaling of the tumor cells and deposit excessive amounts of extracellular matrix (ECM) proteins- the major component of the stroma. This interaction of the PSCs with the cancer cells greatly promote tumor progression and metastasis. In our previous work, we demonstrated that microRNA (miRNA) 29a plays a key role in PSC-mediated stromal reaction, and that the loss of the molecule in PSCs accelerates ECM protein accumulation and cancer growth. To understand the mechanistic regulation of miR-29a in PDAC stroma, we performed RNA-seq analysis with human PSCs (hPSCs), which identified 197 genes that differentially expressed with miR-29a overexpression at a false discovery rate less than 0.05. This included 19 downregulated and one upregulated direct miR-29a targets. Of these, expression of six key targets with the highest fold changes, namely, ADAMTS2, IGF1, E2F7, LAMC1, CLDN1 and ITGA6 by miR-29a were validated at the protein level in hPSCs. In addition, canonical pathways associated with the target genes and their network interactions were assessed, which identified the association of the key targets with pathways such as collagen synthesis, insulin signaling, TGF-β and PI3K/Akt pathways. ADAMTS2, E2F7, LAMC1 and CLDN1 expressions were significantly upregulated in PDAC patient pancreas compared to that in healthy individuals. Together, the current study presents a comprehensive understanding of miR-29a mediation in stromal remodeling, and elucidates associated pathways in regulating PSCs' function in PDAC desmoplasia and pancreatic carcinogenesis.

Citation Format: Shatovisha Dey, Sheng Liu, Tricia D. Factora, Solaema Taleb, Primavera Riverahernandez, Lata Udari, Xiaoling Zhong, Jun Wan, Janaiah Kota. Role of miR-29a in pancreatic stellate cell mediated stromal remodeling in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3714.

Global targetome analysis reveals critical role of miR-29a in pancreatic stellate cell mediated regulation of PDAC tumor microenvironment

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive forms of malignancies with a nearly equal incidence and mortality rates in patients. Pancreatic stellate cells (PSCs) are critical players in PDAC microenvironment to promote the aggressiveness and pathogenesis of the disease. Dysregulation of microRNAs (miRNAs) have been shown to play a significant role in progression of PDAC. Earlier, we observed a PSC-specific downregulation of miR-29a in PDAC pancreas, however, the mechanism of action of the molecule in PSCs is still to be elucidated. The current study aims to clarify the regulation of miR-29a in PSCs and identifies functionally important downstream targets that contribute to tumorigenic activities during PDAC progression.

METHODS

In this study, using RNAseq approach, we performed transcriptome analysis of paired miR-29a overexpressing and control human PSCs (hPSCs). Enrichment analysis was performed with the identified differentially expressed genes (DEGs). miR-29a targets in the dataset were identified, which were utilized to create network interactions. Western blots were performed with the top miR-29a candidate targets in hPSCs transfected with miR-29a mimic or scramble control.

RESULTS

RNAseq analysis identified 202 differentially expressed genes, which included 19 downregulated direct miR-29a targets. Translational repression of eight key pro-tumorigenic and -fibrotic targets namely IGF-1, COL5A3, CLDN1, E2F7, MYBL2, ITGA6 and ADAMTS2 by miR-29a was observed in PSCs. Using pathway analysis, we find that miR-29a modulates effectors of IGF-1-p53 signaling in PSCs that may hinder carcinogenesis. We further observe a regulatory role of the molecule in pathways associated with PDAC ECM remodeling and tumor-stromal crosstalk, such as INS/IGF-1, RAS/MAPK, laminin interactions and collagen biosynthesis.

CONCLUSIONS

Together, our study presents a comprehensive understanding of miR-29a regulation of PSCs, and identifies essential pathways associated with PSC-mediated PDAC pathogenesis. The findings suggest an anti-tumorigenic role of miR-29a in the context of PSC-cancer cell crosstalk and advocates for the potential of the molecule in PDAC targeted therapies.