Cadmium and cancer of prostate and testis.

Cancer of the prostate is an important and potentially fatal disease in humans but the etiology is yet undefined. Cadmium and cadmium compounds are known to be human carcinogens based on findings of increased risk to lung cancer among exposed workers, but a relationship between cancer of the prostate and/or testis in humans is unclear in spite of suggestive results in rats. Parenteral administration or oral exposure to cadmium can result in proliferate lesions and tumors of the prostate in rats. The ability of cadmium to produce neoplasms in the prostate of rats is atypically dose-related and only occurs in rats at doses below the threshold for significant testicular toxicity. Testicular androgen production is essential for the maintenance of the prostate and prostate tumors. The rat testis may also develop tumors if cadmium is given parenterally at high doses. Subsequent to testicular hemorrhagic necrosis, there will be loss of testosterone production and hyperplasia and neoplasia of testicular interstitial cells, thought to be a response to trophic hormone release from the pituitary. The pathogenesis of prostatic cadmium carcinogenesis might include aberrant gene expression resulting in stimulation of cell proliferation or blockage of apoptosis. Activation of transcription factors such as the metallothionein gene and activation of some protooncogenes may enhance cell proliferation with damaged DNA. Suppression of DNA repair would add to the population of cells with damaged DNA. Chemically induced apoptosis can be blocked by cadmium, facilitating aberrant cell accumulation.