Tob 1 is low-expressed in adrenocortical carcinoma and regulates steroidogenic enzymes expression and cell apoptosis of human adrenal cortical cell

Background: Adrenocortical carcinoma (ACC) is an uncommon endocrine malignancy tumor. Finding an effective method is still needed to help diagnose and treat ACC. The aim of the present study was to evaluate the potential effect of Tob1 on ACC. Methods: Tob1 expression in adrenal tissues of patients with ACC or adrenocortical adenoma (ACA) was detected by immunohistochemical staining, western blotting and RT-PCR, respectively. For the in vitro assay, Tob1 overexpression plasmid (pcDNA3.0/Tob1) or empty plasmid (pcDNA3.0) was transfected into H295R cells. The cortisol concentration was detected by ELISA. The mRNA levels of steroidogenic enzymes including CYP11A1, CYP17A1, and 3β-HSD were analyzed by RT-PCR. The cell apoptosis of H295R cells was analyzed by FCM. The expression of k-Ras, p-Raf, Raf, p-MEK, MEK, p-ERK, and ERK were detected by western blotting. Results: Protein and mRNA levels of Tob1 in ACC were significantly decreased as compared with control group. The mRNA levels of CYP11A1, CYP17A1, and 3β-HSD was inhibited by Tob1 overexpression. The cortisol concentration in culture supernatant of H295R cells was also reduced by Tob1 overexpression. Tob1 overexpression induced cell apoptosis of H295R cells. In addition, Tob1 reduced the phosphorylation of Raf, MEK and ERK, suggesting that Ras-Raf-MEK-ERK pathway was involved in the effect of Tob1 on H295R cells. Conclusion: The results indicated that low-expressed Tob1 might be useful to differentiate between ACC and ACA clinically. In addition, Tob1 is a tumor suppressor of ACC and provided a new insight in ACC treatment.