Finally, a precedent exists that hormonal influence may override any tumour suppressive effects of Cx26 expression as stably transfected Cx26 expressing MCF7 cells, with strong growth suppressing effects in vitro, lacked growth suppressing effects in vivo potentially as a result of the pro-tumorigenic effects of 17β estradiol pellets [35]. This evidence concerns the gene GJB2 and neoplasm.