Sulfotransferase Expression And Its Control In Breast Cancer

SULT1E1 is the only sulfotransferase that displays affinity for 17p~estradiol in a physiological (nanomolar) concentration range (Zhang et al., 1998). Other SULTs, including SULT1A1 and SULT1A3, are able to sulfate estrogens in vitro however. For example, cells transfected with the cDNA coding for the enzyme originally called placental hEST 1 (Bernier et al., 1994b; Luu-The et al., 1996), now identified as SULT1A3, was able to transform estrone to EjS at nanomolar concentrations (Bernier et al., 1994b).

Using reverse transcriptase-polymerase chain reaction amplification, the expression of SULT1A3 mRNA was detected in the hormone-dependent MCF-7 and T47-D, as well as in hormone-independent MDA-MB-231 and MDA-468, human breast cancer cells. An interesting correlation of the relative SULT activity and the SULT1A3 mRNA expression was found in various breast cancer cells studied (Chetrite et al., 1998; Figure 8.5).

Qian et al. (1998) demonstrated that the restoration of SULT1E1 expression in MCF-7 cells by cDNA transfection could significantly attenuate the response on both gene activity and DNA synthesis, and cell numbers were used as markers of estrogen-stimulated cell growth and proliferation. These authors suggest that loss or down regulation of SULT1E1 expression may enhance the growth-stimulating effect of estrogens and can contribute to the process of tumor initiation.

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