Benzo[b]thiophene-6-carboxamide 1,1-dioxides: inhibitors of human cancer cell growth at nanomolar concentrations.

Benzo[b]thiophenesulfonamide 1,1-dioxide derivatives (BTS) were described as candidate antineoplastic drugs. In the hope of finding new compounds with improved antitumour activity and reduced toxicity, we have designed and synthesized a small series of benzo[b]thiophene-6-carboxamide 1,1-dioxide derivatives (BTC) structurally related with the best reported BTS. Growth inhibition of HTB-54, CCRF-CEM and HeLa tumour cells lines at nanomolar concentrations was exhibited by some of the BTC. Hydrophobic substituents on the carboxamide group increased cytotoxicity but substitution by a hydroxy group diminished it, thus pointing to the electronic density on benzo[b]thiophene nucleus as a determinant factor. The process of cell death induced by BTC derivatives was further analyzed in CCRF-CEM cells, where these compounds induced apoptosis in a time and dose-dependent manner and cell cycle arrest at S phase. BTC derivatives also induced a significant increase in intracellular ROS levels in this cell line. Previous treatment of the cells with the antioxidant N-acetyl-cysteine abrogated the induction of apoptosis by BTC indicating that ROS generation is a previous event required to trigger the BTC induced apoptotic process.

Estradiol induces type 8 17beta-hydroxysteroid dehydrogenase expression: crosstalk between estrogen receptor alpha and C/EBPbeta.

Hydroxysteroid (17-beta) dehydrogenase (HSD17B) are the enzymes responsible for the reversible interconversion of 17-hydroxy and 17-keto steroids. The human and mouse type 8 17beta-HSD (HSD17B8) selectively catalyze the conversion of estradiol (E2) to estrone (E1). We previously described thatHSD17B8 is transcriptionally regulated by C/EBPbeta, and that C/EBPbeta is bound to CCAAT boxes located at -5 and -46 of the transcription start site in basal conditions in HepG2 cells. Furthermore, ectopic expression of C/EBPbeta transactivated the HSD17B8 promoter activity. Here, we show that HSD17B8 expression is up-regulated in response to E2 in the estrogen receptor alpha (ERalpha) positive MCF-7 cells. Results showed that this induction is mediated by ERalpha because i) E2 did not induce HSD17B8 expression in ERalphanegative HepG2 cells, ii) ectopic expression of ERalpha restored E2-induced HSD17B8 expression, and iii) this induction was blocked by the anti-ER ICI 182,780. Additional experiments showed that no estrogen response element was necessary for this regulation. However, the CCAAT boxes located at the HSD17B8 proximal promoter were required for E2-induced transcription. Furthermore, co-immunoprecipitation studies revealed tethering of ERalphatoC/EBPbeta in response to E2 in cells expressing ERalpha. Additionally, chromatin immunoprecipitation assays demonstrated that, in response to E2, ERalpha is recruited to the CCAAT boxes in which C/EBPbeta is already bound. Taken together, our results reveal that ERalpha is involved in the transcriptional regulation of HSD17B8 gene in response to E2 through its interaction with C/EBPbeta.