Having previously demonstrated the co-expression status of the Lin28A and androgen receptor (AR) in ER-/Her2+ breast cancer, we tested the hypothesis that Lin28A can activate AR and promotes growth of ER-/Her2+ breast cancer. The expression of Lin28A and AR were examined after Lin28A siRNA and Lin28A plasmid were transfected into ER-/Her2+ breast cancer cells. Chromatin immune-precipitation (ChIP) analysis and Luciferase Assays were used to evaluate the effect of Lin28A and c-myc on AR promoter activity. MTT assays, Boyden chamber invasion assays, colony formation assays and flow cytometry analysis were performed. ER-/Her2+ breast cancer cells which transfected with Lin28A siRNAs and Lin28A plasmid were injected into nude mice, and tumorigenesis was monitored. Our data showed that Lin28A can induced AR expression in ER-/Her2+ breast cancer cells. ChIP analysis showed that Lin28A stimulates the recruitment of c-Myc to the promoter of the AR gene. Lin28A enhanced growth ability, colonies ability, cells proliferation activities, invasive ability and inhibited cells apoptosis of ER-/Her2+ breast cancer cells. Lin28A high expression cells exhibited significantly higher tumorigenic ability in vivo. Our study demonstrates that Lin28A can activates androgen receptor via regulation of c-myc and promotes malignancy of ER-/Her2+ breast cancer. Our findings underline a novel role for Lin28A in breast cancer development and activation of the AR axis.
Keywords: Her2; Lin28A; androgen receptor; breast cancer; c-myc.