ESPE Abstracts

Background: Patients with PTEN (phosphatase and tensin homolog) hamartoma tumor syndrome and germ line mutations in PTEN frequently develop lipomatosis, for which there is no standard treatment. Rapamycin was shown to reduce the growth of lipoma cells with heterozygous PTEN deficiency in vitro, but concomitantly induced an up regulation of AKT phosphorylation.

Objective and hypotheses: Since it was shown that resveratrol stabilizes PTEN, we asked whether co-treatment with resveratrol could suppress the rapamycin-induced AKT phosphorylation in PTEN-deficient lipoma cells.

Method: PTEN-deficient lipoma cells and primary PTEN WT preadipocytes were treated with resveratrol, rapamycin or a combination of both. Cell viability was measured by WST-1. Analysis of cell cycle and apoptosis induction was done by staining with propidium iodie and annexin-V-FITC/propidium iodide, respectively, with subsequent flow cytometry. Expression of PTEN and phosphorylation of AKT, S6 kinase and mammalian target of rapamycin was analysed by western blot.

Results: Resveratrol treatment resulted in decreased lipoma cell viability by inducing G1 phase cell cycle arrest and apoptosis. PTEN expression and AKT phosphorylation were not significantly changed, whereas p70S6 kinase phosphorylation was reduced in PTEN-deficient lipoma cells after resveratrol treatment. Rapamycin/resveratrol co-treatment significantly decreased viability further at lower doses of resveratrol and resulted in decreased p70S6 kinase phosphorylation compared to rapamycin treatment alone, suggesting that resveratrol potentiated the growth inhibitory effects of rapamycin by reducing p70S6 kinase activation. Both viability and p70S6 kinase phosphorylation of primary PTEN WT preadipocytes were less affected compared to PTEN-deficient lipoma cells by equimolar concentrations of resveratrol.

Conclusion: These results support the concept of combining chemopreventive natural compounds with mTOR inhibitors in cancer therapy to increase the efficacy of chemotherapeutic drugs.

Funding: We are grateful for the support and funding of the Integrated Research and Treatment Center (IFB) Adiposity Diseases MD Pro_1 and MD Pro_2 granted to J L, Clinical Research Units (KFO) 152 (K7-10) and ‘Kompetenznetz Adipositas Seed Money’ grant to A G.