[Carcinogenic effects of polychlorinated biphenyls (PCBs) and their derivatives, including carcinogenicity to the...

PCBs are compounds whose physical/chemical properties led to their wide spread commercial use. The persistence and stability of PCBs have resulted in a world wide distribution. PCDFs, ones of PCB derivatives, are primary causal agents of mass food poisoning, called Yusho in Japan and Yu-Cheng in Taiwan. Several epidemiologic studies on the carcinogenicity of PCBs in both occupational exposure and accidental intoxication suggest that PCBs might be a potent carcinogen in liver and lung. Many investigators reported that PCBs induced hepatocellular carcinoma in rat and mice. Although either mutagenic or genotoxic effects of PCBs are not definite, their tumor promoting effects have been repeatedly demonstrated in the liver. The effects of PCBs as tumor promoter in the lung have also been reported. PCB congeners that efficaciously promote carcinogenesis increase cytochrome P-450-dependent monooxygenases, which are abundant both in bronchiolar Clara cells and in hepatocytes. PCB congeners which are inducers of P-450 may be active as tumor promoter by inhibiting intercellular communication and/or by stimulating cell proliferation. Furan derivatives like PCDFs have high affinity to bronchiolar Clara cells and hepatocytes. PCDFs induce necrosis and epoxide formation to their target cells, which might result in carcinogenesis of liver and lung.