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 (E2). 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 PCB3. This may be due to cytotoxicity and/or antiestrogenic compounds in the mixtures.