MT 2A Phosphorylation by PKC Mu/PKD Influences Chemosensitivity to Cisplatin in Prostate Cancer

The metallothioneins (MT) are a family of small molecular weight trace metal and free radical scavenging proteins well established to play a role in resistance to chemotherapy and radiation in human cancer. MT gene expression is up regulated in response to the presence of heavy metal ions such as zinc. The activation of MT gene expression in response to zinc treatment in LNCaP and C4-2 prostate cancer (PC) cells was shown by western blotting and DNA microarray analysis. Chemotherapy and radiation sensitivity assays of cells following treatment with cisplatin or radiation were performed in the presence or absence of 150 micron M ZnSO4 and cell viability measured after 72 hours by MTS viability clonogenic and flow cytometry assays. Increasing concentrations of ZnSO4 up regulated MT expression in a dose dependent manner. Microarray analysis demonstrated specific increase in MT expression. Cells treated with zinc demonstrated a significantly decreased sensitivity to cisplatin compared to controls (p 0.05). We have established a physiological in vitro cell line model of MT induction using Zn which is significantly associated with resistance to cisplatin chemotherapy in PC. Immunohistochemistry (IHC) analysis for MT expression in human prostate cancer specimens confirmed nuclear and cytoplasmic expression of MT in majority of specimens. However there was no significant difference in expression between various grades of PC. The original document contains color images.