The Role of PIWIL4, an Argonaute Family Protein, in Breast Cancer

Zifeng Wang,Na Liu,Shuo Shi,Sanhong Liu,Haifan Lin

doi:10.1074/jbc.m116.723239

Abstract

P-element-induced wimpy testis (PIWI) proteins bind to PIWI-interacting RNAs and play key roles in the biogenesis and functions of PIWI-interacting RNAs. It has been reported that PIWI proteins are essential for stem cell self-renewal and germline development in diverse organisms and that they 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 cells derived from breast cancer. Reducing PIWIL4 expression drastically impairs the migration ability of MDA-MB-231 cells, significantly increases their apoptosis, and mildly affects their proliferation. Our transcriptome and proteome analysis reveal that these functions are at least partially achieved via the PIWIL4 regulation of TGF-β and FGF signaling pathways and MHC class II proteins. These findings suggest that PIWIL4 may serve as a potential therapeutic target for breast cancer.

Highlights

PIWI5 proteins represent a subfamily of the Argonaute (Ago) protein family and are highly conserved among eukaryotes and archaea
To explore the mechanisms involved in Triple-negative breast cancer (TNBC), we focused our study on using a cell line (MDA-MB-231) as a model in which PIWIL4 is expressed at the highest level
The PIWIL4 Gene Is Highly Expressed in both Breast Cell Lines and Breast Cancer Samples—It has been reported that P-element-induced wimpy testis (PIWI) proteins have aberrant and ectopic expression in cancers, such as the expression of PIWIL2 in breast cancer [17,18,19,20,21,22, 35]

Summary

Experimental Procedures

Cell Culture and Clinical Samples—MDA-MB-231, MDAMB-435, MDA-MB-468, and MDA-MB-453 cells were cultured in L-15 medium (Leibovitz, Sigma, L1518-500ML) supplemented with 10% fetal bovine serum and incubated at 37 °C without CO2. BT474 and 4T1 cells were cultured in RPMI 1640 medium (Life Technologies, 61870036) supplemented with 10% fetal bovine serum, and MCF-10A cells were cultured in MEBM medium (Lonza, CC-3151) supplemented with 10% bovine calf serum, and these three cell lines were incubated at 37 °C with 5% CO2

PIWI Proteins and Breast Cancer

Results

Discussion