Antitumoral actions of 9-cis retinoic acid and mitotane in an adrenocortical xenograft model. Mus musculus

The actual drug treatment options for adrenocortical carcinoma (ACC) are rather narrow and intensive efforts are going on to find novel effective agents. In our previous functional genomics study, retinoid signaling via the retinoid X receptor (RXR) was detected as a major pathogenic pathway in ACC and we have demonstrated the in vitro activity of 9-cis retinoic acid (9-cisRA) acting via the RXR on NCI-H295R cells and also found that 9-cisRA has antitumoral effects in a small pilot xenograft study. In the present study our aim was to confirm the antitumoral effect of 9-cisRA on adrenocortical cancer in a large xenograft study involving both mitotane and 9-cisRA and their combination. 43 male SCID mice inoculated with NCI-H295R cells were treated in four groups (i. control – corn oil vehicle, ii. 5 mg/kg 9-cisRA, iii. 200 mg/kg mitotane, iv. 5 mg/kg 9-cisRA + 200 mg/kg mitotane) for 28 days. Regular tumor size follow-up, histological and immunohistochemical (Ki-67) analysis, tissue gene expression microarray have been performed. Quantitative real-time-PCR was used for the validation of the microarray results and to detect circulating and tissue microRNAs. To examine the proteome proteomics and Western-blot analysis were executed. We have found that both 9-cisRA and mitotane reduced tumor growth relative to control, but only the combination of the two agents resulted in significant tumor size reduction. The Ki-67 index was significantly reduced in both 9-cisRA and 9-cisRA+mitotane groups. Gene expression analysis revealed 483 genes with significant differences in expression, but only without Benjamini-Hochberg correction (APOA4 and PDE4A were validated). Overall design: 43 SCID mice in four groups: 1) control, 2)mitotane, 3)9-cisRA, 4)combined treated. Treatment time: 28 days. Per os treatment