Breast cancer is a serious illness affecting approximately one in nine women in the United States. Although an actual cause for
breast cancer is unknown, genetic and environmental factors have been associated with its onset. Elevated levels of
estrogen and heightened expression of the WNT10B proto-oncogene have been implicated in the development of human malignant
breast tumors because they enhance the proliferation of mammary tissue. Two
pyrethroid insecticides,
sumithrin and
fenvalerate, have been shown to mimic estrogenic activity in MCF-7 human
breast carcinoma cells by inducing pS2 expression whereas two other
pyrethroids,
permethrin and d-trans
allethrin do not have the same capability. To investigate if
estrogen and these four
pyrethroid insecticides could affect the expression of a gene related to mammary gland development, WNT10B expression in
pyrethroid-treated MCF-7 cells was examined. MCF-7 cells under normal growth conditions do not express WNT10B.
Reverse-transcriptase polymerase chain reaction (RT-PCR), nested PCR and Southern hybridization were employed to detect WNT10B expression. As controls, cells were treated with either
ethanol,
corn oil, or Vista LPA
solvent. When compared to the
solvent-treated controls,
sumithrin,
fenvalerate and
estrogen treated MCF-7 cells all had increased levels of WNT10B expression. The non-estrogenic
pyrethroids, d-trans
allethrin and
permethrin, demonstrated a similar elevation of WNT10B expression at a lower concentration, but not at the higher concentration. The results suggest that
pyrethroid insecticides and
estrogen can enhance the expression of the WNT10B proto-oncogene. However, since both the estrogenic and non-estrogenic substances amplified Wnt10B expression, the mechanism likely involves multiple distinct pathways.