Endocrine Abstracts (2009) 20 P52

Expression of mTOR pathway in human adrenocortical carcinomas and in vitro effects of mTOR inhibitors in human adrenocortical cell lines

Maria Cristina De Martino1,2, Peter van Koetsveld1, Diana Sprij-Mooij1, Richard A Feelders1, Steven W J Lamberts1, Wouter W de Herder1, Annamaria Colao2, Rosario Pivonello2 & Leo J Hofland1

1Division of Endocrinology, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands; 2Department of Endocrinology & Oncology, ‘Federico II’ University, Naples, Italy.

Background: Adrenocortical carcinoma (ACC) is an uncommon malignancy with a still scantily understood pathogenesis and generally poor prognosis. Surgery, performed at early stages, offers the best chance for cure, but unfortunately, it is often noncurative. Medical treatment produced disappointing responses. mTOR inhibitors, such as sirolimus (S) and temsirolimus (T), are promising antineoplastic drugs in several types of carcinomas.

Methods: To evaluate whether ACC might be a candidate for treatment with S or T, we have studied the mRNA expression of mTOR, 4EBP1 and S6K, in 40 human adrenal samples (10 (ACC), 16 adenomas (ACA), 10 hyperplasia (AH), 4 normal (NA)), and in NCI-H295 and SW13 cell lines, by qRT-PCR. The effects of S and T on cell growth (after 24 h, 3 d, 6 d and 9 d) and on the induction of apoptosis (after 24 h and 3 d) were studied by DNA-measurement and the analysis of DNA-fragmentation, respectively, in NCI-H295 and SW13 cell lines.

Results: In ACC, the expression of S6K was lower than in other adrenal samples (ACC=0.13±0.1 versus ACA=0.33±0.16, AH=0.36±0.13, NA=0.31±0.12; P<0.01; median±S.D.), and the expression of mTOR was significantly higher than in NCI-H295 and SW13 cell lines (0.34±0.53 vs 0.18±0.029 and 0.1±0.02, respectively; P<0.005; median±S.D.). A significant correlation was found among the mTOR, 4EBP1 and S6K mRNA levels in ACC (P=0.01). S and T were able to suppress the cell growth of both cell lines, in a similar and dose- and time-dependent manner. SW13 cells (EC50≅7.5×10−11; maximum effect≅90% at 10−8) were significantly more sensitive to treatment with S and T than NCI-H295 cells (EC50≅10−8; maximum effect≅50% at 10−5). A slight induction of DNA-fragmentation, was observed only at the higher concentrations used.

Conclusion: The results of the current study demonstrated that sirolimus and temsirolimus inhibit the in vitro proliferation of ACC cell lines, suggesting that mTOR-inhibitory drugs may have a role in the treatment of ACC.