Abstract: Objective To investigate the effect of LIN28B on maintaining the stemness of cancer stem cells in MCF-7 breast cancer cell line. Methods LIN28B was instantaneously overexpressed in MCF-7 cells (LIN28B-MCF-7). The expression of stemness related genes in both mRNA and protein level were detected by either qPCR or western blot; the proportion of CD44high /CD24low cells was quantitated by flow cytometry；tumorsphere forming ability was analyzed by in vitro experiment; the differential expression of miRNAs either in LIN28B overexpression cells or wild type cells were detected by miRNA-sequencing or real-time PCR . The ability of tumorspheres forming was detected after transfecting miRNA mimics. Results The expression of LIN28B was significantly increased in MCF-7 cells that transfected p-CMV6-LIN28B (P<0.001) . The expression of either mRNA and protein of SOX2, NANOG, c-Myc and OCT4 were up-regulated (P<0.05) ; the proportion of CD44high/CD24low cells was increased from 1.71% to 11.60% (P<0.05); the number of tumorspheres were significantly improved (P<0.01) in LIN28B-MCF-7 cells; 16 miRNAs of differential expression were found by miRNA-sequencing in LIN28B-MCF-7 cells comparing to wild type cells. The proportion of CD44high/CD24low cells was increased from 1.14% to 3.59% （P<0.05）, and the ability of tumorsphere forming was significantly increased in MCF-7 cells after transfecting miR-92b-5p mimic (P<0.01). Conclusion It is suggested that LIN28B maintance the stemness of cancer stem cells by regulating miRNAs in MCF-7 cell line.

Key words: LIN28B , cancer stem cells , tumor associated stemness , miRNAs