Abstract 149: Antisense inhibition of microRNA-21 and -221 in tumor-initiating stem-like cells modulates biological functions of pancreatic cancer including tumorigenesis, metastasis, and chemoresistance

Abstract

Abstract Introduction. Our preliminary studies identified a small population of pancreatic cancer cells with stem-like properties. These cells, called Side Population (SP) cells, were able to induce fast and aggressive tumor formation in nude mice. Cultured SP were able to differentiate into daughter SP or non-SP cells and were found to be highly chemoresistant. Furthermore, performed gene expression analysis showed a significant difference in the expression of more than 1300 genes in SP cells, among which the difference in microRNA expression between SP and non-SP cells was identified as the most interesting candidate for our further studies. Methods. Pancreatic cancer stem-like cells from highly metastatic cell line L3.6pl were identified and characterized by flow cytometry using Hoechst 33342 dye staining. The gene expression was assessed by Affymetrix and the results were further confirmed by quantitative RT-PCR. The antagomir transfection was performed using microRNA-21 and -221 oligonucleotide antisense. Tumor cell apoptosis, cell cycle progression, chemoresistance, and invasion were quantitated by propidium iodide staining and Boyden chamber assay, respectively. Results. In our study, some microRNAs, including miR-21, miR-221, miR-211, and miR-30c-2 were significantly upregulated in stem-like SP from L3.6pl cells. Interestingly, in these cells both miR-21 and miR-221 were involved in the modulation of expression of more than 200 genes, including RASSF6, RAB2B, TP63, TP53INP1, TP53INP2, TET1, MAPK10, MAP2K6, CDK6, TNFRSF11B, SOCS6, STK33, and SMAD7. The administration of antagomir-21 and -221 significantly reduced the SP fracture, decreased SP cell differentiation, positively affected L3.6pl cell proliferation, invasion, and chemoresistance against gemcitabine and 5-Fluorouracil. Conclusion. Our results demonstrate the significance of both microRNA-21 and -221 in tumor-initiating capability of stem-like tumor cells in pancreatic cancer. Both microRNAs contribute to the most important biological functions of pancreatic cancer including apoptosis, metastasis, and chemoresistance, and may further serve as a potential target for pancreatic cancer therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 149. doi:10.1158/1538-7445.AM2011-149