MCF‐7 human mammary adenocarcinoma cells exhibit augmented responses to human insulin on a collagen IV surface

Human mammary cell lines are extensively used for preclinical safety assessment of insulin analogs. However, it is essentially unknown how mitogenic responses can be optimized in mammary cell‐based systems. We developed an insulin mitogenicity assay in MCF‐7 human mammary adenocarcinoma cells, under low serum (0.1% FCS) and phenol red‐free conditions, with 3H thymidine incorporation as endpoint. Based on EC50 values determined from 10‐fold dilution series, β‐estradiol was the most potent mitogen, followed by human IGF‐1, human AspB10 insulin and native human insulin. AspB10 insulin was significantly more mitogenic than native insulin, validating the ability of the assay to identify hypermitogenic human insulin analogs. With MCF‐7 cells on a collagen IV surface, the ranking of mitogens was maintained, but fold mitogenic responses and dynamic range and steepness of dose–response curves were increased. Also, PI3K pathway activation by insulin was enhanced on a collagen IV surface. This study provided the first determination and ranking of the mitogenic potencies of standard reference compounds in an optimized MCF‐7 assay. The optimized MCF‐7 assay described here is of relevance for in vitro toxicological testing and carcinogenicity safety assessment of new insulin compounds. Copyright © 2009 John Wiley & Sons, Ltd.