Exposure to cadmium (Cd) is associated with a spectrum of human pathogenesis including the prostate cancer (CaP). A clear dose-response relation between Cd-exposure and abnormal prostate serum antigen (PSA), a marker for CaP have been reported in men exposed to Cd. However, the molecular mechanism underlying the malignant cell transformation following Cd exposure is yet to be determined, while the association between Cd and CaP in both pre-clinical and clinical models are well established. The goal of this application is to investigate the underlying mechanism of how Cd causes malignant cell transformation (from normal to transformed cells) and on the development of tumorigenesis by the Cd-transformed cells (transformed cells to tumorigenesis). Our preliminary results suggest that during cellular transformation, Cd exposure induced endoplasmic reticulum (ER)-stress, which triggered the phosphorylation of stress transducers including PERK and eIF2-? resulted in the activation of ATF4 and initiate the induction of autophagy that protects Cd- damaged cells. Although, induction of autophagy markers (Atg -12 and Atg-16L, LC3B and Lamp1) were seen in Cd-treated cells, the autophagy process is incomplete, due to failure autophagosome and autolysosome fusion, which allowed the damaged cell to proliferate for transformation. A massive accumulation of p62 in Cd- treated cells, which also confirmed the defective autophagy. Silencing EGFR activation by siRNA or pharmacological inhibitors significantly inhibited the growth in transformed cells, but not in Cd-treated normal cells or Cd- transforming cells suggesting that EGFR activation plays a critical role, only after cellular transformation. Xenograft tumor tissues generated by Cd-transformed cells expressed high levels of ATF-4, EGFR, p62 and LC3B in correlation with in vitro findings. Moreover, increased expression of the proteins (ATF- 4, EGFR, p62, and LC3B) in human CaP specimen?s agreement with Gleason sum in comparison with benign prostatic hyperplasia and ?normal? adjacent tissues. Based on the results we hypothesize that Chronic exposure of prostate epithelial cells to Cd causes ER-stress and subsequently defective autophagy, leading to increased survival of damaged cells that result in malignant cell transformation and in transformed cell EGFR activation play a significant role in tumorigenesis.
Three specific aims are proposed:
Aim -1: To demonstrate that Cd causes ER-stress which in turn induced defective autophagy during the transformation of prostate epithelial cells.
Aim 2 : Investigate the protective role of defective autophagy, which increases the survival of Cd-damaged cells during the transformation of prostate epithelial cells.
Aim -3: study Cd-induced tumorigenesis in mouse models and validate the molecular markers in human prostate specimens.
Cadmium (Cd) is a non-essential metallic element that is found at varying levels in soil throughout the United States. Exposure to cadmium (Cd) is associated with a spectrum of human pathogenesis including the prostate cancer. The goal of this application is to investigate the underlying mechanism of how Cadmium (Cd) causes malignant cell transformation (from normal to transformed cells) and how transformed to tumorigenesis (transformed cells to tumorigenesis). This study will highlight the better understanding of the complex interrelationship among prostate cancer phenotypes and the molecular, cellular, biochemical, and pathological changes associated with cadmium and prostate cancer.