Role of micro-RNA 199a-3p in lymph node stromal extracellular vesicles on tumorigenesis in colorectal cancer

Abstract Introduction: MicroRNAs (miRNAs) are short non-coding RNAs implicated in post-transcriptional regulation of gene expression. Abnormal expression of miRNAs in cancer is associated with enhanced tumorigenesis and metastatic potential. Our previous data has shown that extracellular vesicles (EV) secreted by human lymph node stromal cells (LNSC) enhance tumorigenesis in colorectal cancer (CRC). By systemic searching and modifying miRNAs carried by EV through overexpression and inhibition on LNSC, we aim to demonstrate their effect on CRC progression in vitro and orthotopic mouse model. Methods: Total microRNA sequencing was analyzed using in-silico computer prediction models. Four overexpressed miRNAs in the LNSC-EV were selected (miR-155-5p, miR-199a-3p, mi-143-3p, and mi-214-3p). Tumor cell proliferation assay was performed using a CRC SW620 cell line transfected with selected miRNA mimics or inhibitors or controls. In our mouse model, miRNA transfected SW620 cells tagged with luciferase/RFP, were injected into the rectal submucosa of NOD/SCID mice. Tumor growth and metastases were observed by weekly bioluminescent imaging (BLI). At week 7, tumors were weighed and BLI of the tumors and organs were recorded. Immunohistochemistry staining was performed on the paraffin sections of tumors, livers and lung collected from these mice. Results: In vitro proliferation assays, cells transfected with the mimic of miRNA 199a-3p significantly increased CRC SW620 cell proliferation (p<0.01) while cells treated with the inhibitor showed decreased proliferation (p<0.05). In our orthotopic mouse model, mice with SW620 cells transfected with the mimic had increased frequencies of tumorigenesis (94% vs. 14%) and liver and lung metastasis comparing to control group (56% vs 9.5%, 50% vs 0%). Mice injected with SW620 cells transfected with the miRNA inhibitor had decreased tumor growth compared to the negative control (p<0.05). Conclusion: Our study shows that miRNAs carried in LNSC-EV are crucial for CRC progression. Specifically, inhibition of miRNA-199a-3p may serve as a therapeutic target in the treatment of CRC. Understanding the role and mechanisms of this miRNA in CRC could lead to the improved management of patients with CRC. Citation Format: Hallie Baer, Jessica Simon, Lara McKean-Baste, Alicia N. Ray, Heather Green, Grace Maresh, Xin Zhang, David Marjolin, Jennifer Paruch, Li Li. Role of micro-RNA199a-3p in lymph node stromal extracellular vesicles on tumorigenesis in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1487.