Virtual Screening and Optimization of Novel mTOR Inhibitors for Radiosensitization of Hepatocellular Carcinoma.

BACKGROUND: Radiotherapy has an ameliorative effect on a wide variety of tumors, but hepatocellular carcinoma (HCC) is insensitive to this treatment. Overactivated mammalian target of rapamycin (mTOR) plays an important part in the resistance of HCC to radiotherapy; thus, mTOR inhibitors have potential as novel radiosensitizers to enhance the efficacy of radiotherapy for HCC. METHODS: A lead compound was found based on pharmacophore modeling and molecular docking, and optimized according to the differences between the ATP-binding pockets of mTOR and PI3K. The radiosensitizing effect of the optimized compound (2a) was confirmed by colony formation assays and DNA double-strand break assays in vitro. The discovery and preclinical characteristics of this compound are described. RESULTS: The key amino acid residues in mTOR were identified, and a precise virtual screening model was constructed. Compound 2a, with a 4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine scaffold, exhibited promising potency against mTOR (mTOR IC50=7.1 nmol/L (nM)) with 126-fold selectivity over PI3Kα. Moreover, 2a significantly enhanced the sensitivity of HCC to radiotherapy in vitro in a dose-dependent manner. CONCLUSION: A new class of selective mTOR inhibitors was developed and their radiosensitization effects were confirmed. This study also provides a basis for developing mTOR-specific inhibitors for use as radiosensitizers for HCC radiotherapy.

Effects of ginsenoside Rh2(GS-Rh2) on cell cycle of Eca-109 esophageal carcinoma cell line / 中国中药杂志

<p><b>OBJECTIVE</b>To investigate the effects of ginsenoside Rh2 (GS-Rh2) on growth inhibition and cell cycle of Eca-109 esophageal carcinoma cell line in culture.</p><p><b>METHOD</b>The effects of GS-Rh2 on cell growth inhibition was detected by MTT assay. Cell cycle was analyzed by flow cytometry (FCM). Cell morphology was observed by a light microscope after HE staining. The protein expression of cell cycle components (cyclinE, CDK2, p21WAF1) were examined by immunocytochemistry and Western blot. The mRNA expression were examined by semiquantitative RT-PCR.</p><p><b>RESULT</b>GS-Rh2 inhibited the proliferation of Eca-109 cells in dose and time-dependent manners. The inhibition rate was about 50% after 1-day treatment with 20 microg x mL(-1) GS-Rh2 x 20 microg x mL(-1) GS-Rh2 induced the mature differentiation and morphological reversion. With increasing dose of GS-Rh2 treatment, the cell number of G0/G1 phase was increased, whereas it decreased at S and G2/M phase. There was significant difference between 10, 20 microg x mL(-1) GS-Rh2 groups and the corresponding group without GS-Rh2 treatement. After treating cells by 20 microg x mL(-1) GS-Rh2 for 1, 2, 3 days individually, the protein and mRNA expression of both cyclinE and CDK2 reduced, while the expression of p21WAF1 enhanced gradually.</p><p><b>CONCLUSION</b>GS-Rh2 could arrest Eca-109 cells at G0/G1 phase and induce cell differentiation tending to normal. Furthermore, GS-Rh2 had an effect on expression of cell cycle components (cyclinE, CDK2 and p21WAF1) to inhibit Eca-109 cell proliferation.</p>