Abstract
Loss of tumor suppressor is a common phenomenon in tumor cell. The defect accompanies with alterations of gene transcription and protein expression profiles. In this study, a frequently lost tumor suppressor in breast cancer, PTEN, is knockdown by siRNA in human mammary cell. Protein profile of the PTEN depleted cells was analyzed by two-dimension differential gel electrophoresis combined with matrix-assisted laser desorption ionization/time of flight mass spectrometry. Ten of the protein spots were identified, and most of them play roles in oncogenesis or tumor suppression. These proteins participate in cell growth (alpha-enolase), proliferation (NF2), cytoskeleton rearrangement (Hsp27), and apoptosis (suppressor of tumorigenicity 20, ST20). Additionally, a functional unknown protein, CCDC90A, is also found. We subsequently used Western blotting and real-time quantitative polymerase chain reaction to examine whether the differential expressions are regulated at gene transcriptional or protein translational level. The gene expression and quantity of the identified proteins were compared among normal mammary cell (MCF10A), non-invasive and invasive breast cancer cell (MCF7 and MDA231, respectively). In summary, we investigated the proteins that differentially expressed in PTEN knock-down cells and analyzed the correlations to breast tumor progression. We identified that CCDC90A is negatively regulated by PTEN expression and up-regulated through tumor progression; a phenomenon that has not been reported. This study offers extended information for future research on those proteins to explore the occurrence and progression of breast cancer.