METALLOTHIONEINS AND ONCOLOGY

The metallothionein (MT) family is a class of low-molecular-weight, cysteine-rich proteins (MT-1, MT-2, MT-3, and MT-4) with high affinity for metal ions. Apart from their involvement in metal ion homeostasis and detoxification, protection against oxidative damage, and cell proliferation and apoptosis, they are also implicated in drug and radiotherapy resistance and several aspects of the carcinogenic process. Variable MT expression has been observed in different cancer types, reaching statistically significant correlation with clinicopathological parameters in some cases; nevertheless, MT expression as a marker of prognosis or as a predictor for the response to either chemotherapy or radiotherapy remains unclear. The present review examines the expression of MT in different human tumors in correlation with resistance to radiation therapy or chemotherapy and patients' final outcome. Detailed studies focused on the expression of MT isoforms and isotypes in different tumor types could elucidate the role of this group of proteins in patients' prognosis and resistance to treatment strategies.