The potential importance of the sulphatase pathway for the in situ formation of oestrogen from oestrogen sulphates was recently demonstrated in a study in which MCF-7 breast cancer cells transfected with either vector (MCF-7v) or vector containing the STS cDNA (MCF-7STS) were inoculated into the flanks of ovariectomised nude mice (James et al, 2001). This evidence concerns the gene STS and breast cancer.