Dopamine D1 receptor activation induces dehydroepiandrosterone sulfotransferase (SULT2A1) in HepG2 cells.

AIM: Dopamine receptors are present in the nervous system and also widely distributed in the periphery. The aim of this study was to investigate the role of D1 subtype dopamine receptors (DRD1) in the regulation of dehydroepiandrosterone sulfotransferase (SULT2A1) in HepG2 cells. METHODS: HepG2 cells were treated with DRD1 agonists with or without DRD1 antagonist for 9 d. DRD1 and SULT2A1 mRNA expression, protein expression, and SULT2A1 activity were detected using RT-PCR, Western blotting and HPLC, respectively. The level of cAMP was measured using a commercial kit. RESULTS: All the 5 DR subtypes (DRD1-DRD5) were found to be expressed in HepG2 cells. Treatment of HepG2 cells with the specific DRD1 agonists SKF82958 (2.5 µmol/L) or SKF38393 (5 and 50 µmol/L) significantly increased the mRNA and protein expression of both DRD1 and SULT2A1, and increased SULT2A1 activity and cAMP levels. These effects were partially blocked by co-treatment with the specific DRD1 antagonist SCH23390 (2.5 µmol/L). In addition, transfection of HepG2 cells with DRD1-specific siRNAs decreased DRD1 mRNA expression by 40%, which resulted in the reduction of SULT2A1 mRNA expression by 60%, protein expression by 40%, and enzyme activity by 20%. CONCLUSION: DRD1 activation upregulates DRD1 and SULT2A1 expression and SULT2A1 activity in HepG2 cells, suggesting that the DRD1 subtype may be involved in the metabolism of drugs and xenobiotics through regulating SULT2A1.

Inhibition of EGFR autophosphorylation plays an important role in the anti-breast cancer efficacy of the dithiocarbamate derivative TM208.

AIM: To investigate the effects of a novel dithiocarbamate derivative TM208 on human breast cancer cells as well as the pharmacokinetic characteristics of TM208 in human breast cancer xenograft mice. METHODS: Human breast cancer MCF-7 and MDA-MB-231 cells were treated with TM208 or a positive control drug tamoxifen. Cell proliferation was examined using SRB and colony formation assays. Cell apoptosis was analyzed with Annexin V-FITC/PI staining assay. Protein expression was examined with Western blot, ELISA and immunohistochemical analyses. MCF-7 breast cancer xenograft nude mice were orally administered TM208 (50 or 150 mg·kg(-1)·d(-1)) or tamoxifen (50 mg·kg(-1)·d(-1)) for 18 d. On d 19, the tumors were collected for analyses. Blood samples were collected from the mice treated with the high dose of TM208, and plasma concentrations of TM208 were measured using LC-MS/MS. RESULTS: Treatment of MCF-7 and MDA-MB-231 cells with TM208 dose-dependently inhibited the cell proliferation and colony formation in vitro (the IC50 values were 36.38 ± 3.77 and 18.13 ± 0.76 µmol/L, respectively). TM208 (20-150 µmol/L) dose-dependently induced apoptosis of both the breast cancer cells in vitro. In MCF-7 breast cancer xenograft nude mice, TM208 administration dose-dependently reduced the tumor growth, but did not result in the accumulation of TM208 or weight loss. TM208 dose-dependently inhibited the phosphorylation of EGFR and ERK1/2 in both the breast cancer cells in vitro as well as in the MCF-7 xenograft tumor. CONCLUSION: Inhibition of EGFR autophosphorylation plays an important role in the anticancer effect of TM208 against human breast cancer.