A Cancer Reprogramming Method Using MicroRNAs as a Novel Therapeutic Approach against Colon Cancer: Research for Reprogramming of Cancer Cells by MicroRNAs

Background: We previously generated induced pluripotent stem cells by reprograming adipose stem cells through the introduction of microRNAs targeting four transcription factors (Oct3/4, Sox2, c-Myc, and Klf4). In this study, we aimed to reprogram cancer cells using microRNAs to explore their therapeutic potential. Methods: Mature microRNAs (mir-302a-d, 369-3p and 5p, and mir-200c, as needed) were introduced into colon cancer cells (DLD-1, RKO, and HCT116) using lipofection. Results: The transfected cells exhibited an embryonic stem cell-like morphology and expressed the undifferentiated marker genes Nanog, Oct3/4, SOX2, and Klf4, as well as tumor-related antigen-1-60. These cells expressed neurogenic or adipogenic markers, indicating that reprogramming of the cancer cells was partially successful. Moreover, we found that miRNA-expressing DLD-1 cells showed low proliferative activity in vitro and in vivo, accompanied by increased expression of the tumor suppressor genes p16^ink4a and p21^waf1. miRNA-expressing DLD-1 cells also exhibited enhanced sensitivity to 5-fluorouracil, possibly through the downregulation of multidrug-resistant protein 8. The reprogrammed cells from DLD-1, RKO, and HCT116 cells exhibited reduced c-Myc expression, in contrast to the high c-Myc expression in the induced pluripotent cancer cells that were generated using four transcription factors. Conclusions: Our cancer reprogramming method employing simple lipofection of mature microRNAs is safe and well suited for clinical application, because it avoids integration of exogenous genes into the host genome and allows escape from augmentation of c-Myc gene expression.