The role of PIWIL4 in breast cancer

PIWI proteins bind to PIWI-interacting RNAs (piRNAs) and play key roles in the biogenesis and functions of piRNAs. It has been reported that PIWI proteins are essential for stem cell self-renewal and germline development in diverse organisms, and are ectopically expressed in multiple forms of cancer. However, the role of PIWI in cancer remains elusive. Here we report that one of the four PIWI proteins in humans, PIWIL4, is highly expressed in both breast cancer tissues and the cytoplasm of MDA-MB-231 cell line derived from breast cancer. Reducing PIWIL4 expression drastically impairs migration ability of MDA-MB-231 cells, significantly increases their apotosis, and mildly affects their proliferation. Our transcriptome and proteome analyses reveal that these functions are at least partially achieved via the PIWIL4 regulation of TGF-beta and FGF signaling pathways and major histocompatibility complex (MHC) class II proteins. These findings suggest that PIWIL4 may serve as a potential therapeutic target for breast cancer. Overall design: Examination of small RNAs in two conditions