Genotoxic effects of drospirenone and ethinylestradiol in human breast cells (in vitro) and bone marrow cells of female mice (in vivo)

Estrogen and progesterone congeners as found in various oral contraceptive formulations have been implicated as the cause of cancer in sex and tissue-specific targets. The mechanism of carcinogenesis by sex steroids is still debatable. In this study, we evaluated the genotoxicity induced by two components of one of the commonly used oral contraceptive formulation; drospirenone and ethinylestradiol in human breast cells (MCF-7) in vitro and in bone marrow cells of female mice in vivo. DNA damage was assessed by alkaline comet assay. Both of the drugs produced DNA damage in human breast cells at exposure concentrations which are about 100-fold and above than normally found in human blood after their lowest recommended doses. The DNA damage was produced only after metabolic activation by mice liver S-9 fraction in both cases. The co-exposure with both the compounds at median exposure levels resulted in potentiation of DNA damage. In bone marrow cells of adult female mice, both the compounds produced DNA damage at human equivalent doses after exposure was carried out repeatedly for approximately one estrus cycle (5 days). The co-administration with the compounds resulted in potentiation of DNA damage as indicated by percent tail DNA in comet assay. Thus it is concluded that drospirenone and ethinylestradiol cause DNA damage in certain target specific tissue (mammary epithelial cells) and in female bone marrow cells. The co-exposure with drospirenone and ethinylestradiol results in potentiation of genotoxicity which may pose a threat of cancer development in women taking these drugs for long periods.