Proteomics evaluation of MDA-MB-231 breast cancer cells in response to RNAi-induced silencing of hPTTG

Breast cancer is the most common cancer in women worldwide. Several genes are up-regulated in breast cancer such as human pituitary tumor transforming gene (hPTTG). This study aims to evaluate cell proliferation and the downstream expression pattern of hPTTG1 gene at the mRNA and protein levels after specific down-regulation of hPTTG1 by siRNA. The human breast cancer MDA-MB-231 cell line was transfected with siRNA against hPTTG1. The mRNA and protein expression levels were examined by Real-time PCR and Western blot, respectively. The cell proliferation was assayed by MTS. To investigate the pattern of protein expression, total cellular protein was analyzed by 2D gel electrophoresis and mass spectroscopy. Subsequently, the possible biological consequences were determined by the bioinformatics databases. Subsequent of hPTTG1 silencing in the MDA_MB-231 cells, the proliferation of cells decreased obviously. In response to hPTTG1 silencing, the levels mRNA and protein were effectively down-regulated 80% and 50%, respectively, at 48 h post-transfection. The proteomics evidenced that PTTG1 increased the expression of 5 proteins. The reduced expression of PTTG1 was functionally involved in hypoxia (NPM1, ENO1), cell proliferation and apoptosis (ENO1, NPM1, NME1, STMN1), and metastasis (NPM1, NME1). We identified the hPTTG1-regulated proteins and its molecular mechanism in pathogenesis of breast cancer. Further study emphasis is to understand the association of hPTTG1 with other genes in cancer progression. This novel modality might also consider for identification of targeted drugs, prognosis and follow up in breast cancer gene therapy.