The available drug treatment options for adrenocortical carcinoma (ACC) are limited. In our previous studies, the in vitro activity of 9-cis retinoic acid (9-cisRA) on adrenocortical NCI-H295R cells was shown along with its antitumoral effects in a small pilot xenograft study. Our aim was to dissect the antitumoral effects of 9-cisRA on ACC in a large-scale xenograft study involving mitotane, 9-cisRA and their combination. 43 male SCID mice inoculated with NCI-H295R cells were treated in four groups (i. control, ii. 9-cisRA, iii. mitotane, iv. 9-cisRA + mitotane) for 28 days. Tumor size follow-up, histological and immunohistochemical (Ki-67) analysis, tissue gene expression microarray, quantitative real-time-PCR for the validation of microarray results and to detect circulating microRNAs were performed. Protein expression was studied by proteomics and Western-blot validation. Only mitotane alone and the combination of 9-cisRA and mitotane resulted in significant tumor size reduction. The Ki-67 index was significantly reduced in both 9-cisRA and 9-cisRA+mitotane groups. Only modest changes at the mRNA level were found: the 9-cisRA-induced overexpression of apolipoprotein A4 and down-regulation of phosphodiesterase 4A was validated. The expression of circulating hsa-miR-483-5p was significantly reduced in the combined treatment group. The SET protein was validated as being significantly down-regulated in the combined mitotane+9-cisRA group. 9-cisRA might be a helpful additive agent in the treatment of ACC in combination with mitotane. Circulating hsa-miR-483-5p could be utilized for monitoring the treatment efficacy in ACC patients, and the treatment-induced reduction in protein SET expression might raise its relevance in ACC biology.
Keywords: 9-cis retinoic acid; Adrenocortical cancer; SET protein; circulating microRNA; mitotane; xenograft.