CDC25A pathway toward tumorigenesis: Molecular targets of CDC25A in cell-cycle regulation.

The cell division cycle 25 (CDC25) phosphatases regulate key transitions between cell-cycle phases during normal cell division, and in the case of DNA damage, they are key targets of the checkpoint machinery that ensure genetic stability. Little is known about the mechanisms underlying dysregulation and downstream targets of CDC25. To understand these mechanisms, we silenced the CDC25A gene in breast cancer cell line MDA-MB-231 and studied downstream targets of CDC25A gene. MDA-MB-231 breast cancer cells were transfected and silenced by CDC25A small interfering RNA. Total messenger RNA (mRNA) was extracted and analyzed by quantitative real-time polymerase chain reaction. CDC25A phosphatase level was visualized by Western blot analysis and was analyzed by 2D electrophoresis and LC-ESI-MS/MS. After CDC25A silencing, cell proliferation reduced, and the expression of 12 proteins changed. These proteins are involved in cell-cycle regulation, programmed cell death, cell differentiation, regulation of gene expression, mRNA editing, protein folding, and cell signaling pathways. Five of these proteins, including ribosomal protein lateral stalk subunit P0, growth factor receptor bound protein 2, pyruvate kinase muscle 2, eukaryotic translation elongation factor 2, and calpain small subunit 1 increase the activity of cyclin D1. Our results suggest that CDC25A controls the cell proliferation and tumorigenesis by a change in expression of proteins involved in cyclin D1 regulation and G1/S transition.