Sunitinib decreases adrenocortical cancer cell proliferation and specifically inhibits adrenal steroidogenesis
Miriam Reuss1, Matthias Kroiss1, Sarah Johanssen1, Melanie Beyer1, Martina Zink1, Michaela Hartmann2, Vivek Dhir3, Stefan Wudy2, Wiebke Arlt3, Silviu Sbiera1, Bruno Allolio1 & Martin Fassnacht1
Background: The multi-tyrosine kinase inhibitor sunitinib is approved for advanced renal cell carcinoma and gastrointestinal stroma tumors. It targets both tumor vessels and malignant cells. Animal experiments have pointed to a direct adrenotoxic effect of the drug.
Aims: We hypothesized that sunitinib may inhibit proliferation of adrenocortical cancer (ACC) cells and influence adrenal steroid hormone synthesis.
Results: Sunitinib reduced cell viability in both ACC cell lines NCI-h295 and SW13 in a dose-dependent manner (MTT assays SW13: 96±7% (0.1 μM), 90±9%* (1 μM), 79±9%* (2 μM), 62±9%* (5 μM), and 57±3%* (10 μM) vs 100±9% in control cells, *P<0.01). Analyses of selected steroid hormones in supernatant of NCI-h295-cells indicated a significant decrease of glucocorticoid secretion after incubation with sunitinib, while precursor hormones accumulated. Using isotope dilution gas chromatography mass spectrometry a complete steroid profile exhibited an increased ratio of DHEA/androstenedione (0.1 μM: 1.02±0.04; 1 μM: 1.30±0.06*; 5 μM: 1.50±0.05*; *P<0.01) and 17-OH-pregnenolone/17-OH-progesterone. This suggested a dose-dependent inhibition of 3β-hydroxysteroid dehydrogenase (HSD3B) catalyzing these reactions. Whilst no direct inhibition of HSD3B activity by sunitinib was detected in yeast microsome assays, we found a dose-dependent down-regulation of HSD3B in real time PCR and western blot after 24 h incubation with sunitinib (relative RNA expression: 1 μM 47±7%*; 5 μM 33±7%*; 10 μM 27±6%*; protein expression: 1 μM 82±8%; 5 μM 62±8%*; 10 μM 55±9%*; *P<0.05), whereas the expression of other adrenal enzymes like CYP11A1 remained unaffected.
Conclusion: Our data demonstrate a specific blockade of adrenal steroidogenesis by sunitinib via downregulation of HSD3B. Studies in patients treated with sunitinib are warranted to assess the clinical impact of this finding. Whether inhibition of ACC cell proliferation by sunitinib is clinically relevant is currently investigated in the SIRAC-trial.