Antisense inhibition of microRNA-21 and microRNA-221 in tumor-initiating stem-like cells modulates tumorigenesis, metastasis, and chemotherapy resistance in pancreatic cancer

Abstract

Our preliminary studies identified a small population side population (SP) cells in pancreatic cancer cells with stem cell-like properties, which were able to induce fast and aggressive tumor formation in nude mice. Gene expression analysis showed a significant difference in the expression of more than 1,300 genes in SP cells, among which a highly significant difference in microRNA expression of miR-21 and miR-221 between SP and NSP cells was identified. SP cells were identified and characterized by flow cytometry using Hoechst 33342 dye staining from a highly metastatic human pancreatic cancer cell line (L3.6pl). Antagomir transfection was performed using miRNA-21 and miRNA-221 antisense oligonucleotides (ASOs) and followed by detection of cell apoptosis, cell cycle progression, chemosensitivity, and invasion. Sorted SP cells from gemcitabine-resistant L3.6pl cells (L3.6pl(Gres)-SP) cells were orthotopically implanted in nude mice with or without miRNA-21 and miRNA-221 ASOs mono- and combination therapy. The administration of antagomir-21 and antagomir-221 significantly reduced the SP cell fraction, decreased SP cell differentiation, and downstream gene regulation, and thereby induced reduction of L3.6pl cell proliferation, invasion, and chemoresistance against gemcitabine and 5-Fluorouracil. Combination of ASOs therapy against miRNA-21 and miRNA-221 significantly inhibited primary tumor growth and metastasis compared to single antagomir treatment, especially, in L3.6plGres-SP-induced pancreatic tumor growth in vivo. These findings further indicate that the inhibition of miR-21 and miR-221 appear particularly suitable to target stem-like subpopulations and address their specific biological function to promote tumor progression in pancreatic cancer.

Overexpression of microRNA-21 strengthens stem cell-like characteristics in a hepatocellular carcinoma cell line

“…Our observation that miR-21 overexpression leads to faster tumor growth in a nude mouse xenograft model is consistent with a report that inhibiting miR-21 in pancreatic CSCs substantially decreased the growth of pancreatic tumor xenografts [42]. In another study, colorectal cancer cells were stably transfected with miR-21 plasmid and subcutaneously injected into female SCID mice [43].…”

miRNA analysis in pancreatic cancer: the Dartmouth experience

“…For miR-21 and miR-122, ASOs increase the levels of their targets (PTEN, BCL2, RECK and CDKN1B), reduce proliferation and increase apoptosis of pancreatic cancer cells. In addition, they sensitize PDAC cells to gemcitabine [20,35,39].…”

Integrating MicroRNA Expression Profiling Studies to Systematically Evaluate the Diagnostic Value of MicroRNAs in Pancreatic Cancer and Validate Their Prognostic Significance with the Cancer Genome Atlas Data

“…Hence, emerging studies have discovered that the differential expression of miRNA, such as miR-21, miR-99a, and miR-34a, could predict the prognosis of PaCa patients [16][17][18]. In pancreatic tumor tissue, aberrant expression of miRNAs, such as miR-21, miR-221, miR-34a, and miR-217, were reported, which suggested that these molecular regulators had the potential to serve as biomarkers [17,[19][20][21]. Meta-analyses were conducted to evaluate the diagnostic value of miRNAs, and they showed moderate predictive values for PaCa diagnosis [22,23].…”