Stimulation of MCF-7 cell proliferation by low concentrations of Chinese domestic polychlorinated biphenyls

The simple and sensitive in vitro MCF-7 human breast cancer cell proliferation assay was used to examine the proliferation abilities of two Chinese commercial polychlorinated biphenyl ( PCB) mixtures made in the 1960s. Chinese PCB3 and Chinese PCB5 were compared with 17 beta-estradiol (E-2). All of the positive activities of these types of Chinese PCBs were significantly different compared to controls with respect to MCF-7 cell doubling time. At lower levels of 7.8 pg/ml and 182 pg/ml, the Chinese PCB3 showed 94% and 86% of relative proliferation effects compared to 17 beta-estradiol, respectively. Chinese PCB5, also showed higher cell proliferation activity at lower level of 8.3 pg/ml, with relative proliferation effect as high as 107% in comparison to 17 beta-estradiol. Thus, both PCBs seem to be different from corresponding Aroclor mixtures. However, Chinese PCBs did not express cell proliferation effects at higher levels of 9.1 ng/ml for Chinese PCB3 and 166 pg/ml and 8.3 ng/ml for Chinese PCB5. This may be due to cytotoxicity and/or antiestrogenic compounds in the mixtures.