Charlotte Viëtor¹, Anand Iyer², Eric Bindels³, Lona Moradi-Zeyenedpour⁴, Theo Luider⁴, Cornelis Verhoef⁵, Tessa van Ginhoven⁵, Richard Feelders², Leo Hofland², 


(1) Erasmus MC, dept. of Internal Medicine, sector Endocrinology, and dept. of Surgery, Rotterdam, Nederland. (2) Erasmus MC, dept. of Internal Medicine, sector Endocrinology, Rotterdam, Nederland. (3) Erasmus MC, dept. of Hematology, Rotterdam, Nederland. (4) Erasmus MC, dept. of Neurology, laboratory of Neuro-Oncology/Clinical & Cancer Proteomics, Rotterdam, Nederland. (5) Erasmus MC, dept. of Surgery, Rotterdam, Nederland.

Background:

Mitotane is the first-line medical treatment option for adrenocortical carcinoma (ACC). Drawbacks of mitotane treatment are substantial, including severe toxicity and contralateral adrenal gland destruction, whilst both clinical and in vitro studies have shown that it is only effective in 25-30% of ACCs. This study aimed to identify tissue biomarkers to improve future patient selection for mitotane therapy.

Methods:

We conducted a transcriptomics and proteomics study on fresh-frozen ACC tissues classified as responders (n=13), partial responders (n=10), or non-responders (n=7) based on in vitro mitotane-induced inhibition of cell proliferation. RNA sequencing and shotgun LC-MS were performed. Gene and protein expression patterns associated with response to mitotane were assessed in a correlation analysis and using DESeq2, followed by pathway analysis with Ingenuity and Weighted Gene Co-expression Network Analysis (WGCNA).  Also, data were compared to previous ACC transcriptomic studies.

Results:

Distinct transcriptomic and proteomic signatures characterized mitotane responders compared to partial and non-responders, whereas fewer differences were found between those latter groups. A total of 718 genes and 60 proteins were differentially expressed between responders and non-responders to mitotane. Pathway analysis revealed upregulation of cell cycle and collagen production genes and downregulation of mitochondrial proteins in responders, which was also observed using WGCNA. Transcriptomic clustering with clinicopathological data indicated that responders frequently presented with cortisol-producing ACC and metastatic disease or lymph node involvement. Comparison with prior studies showed transcriptomic patterns of responders aligning with aggressive, proliferative ACC subtypes.

Conclusion:

Transcriptomic and proteomic profiling offers promise to predict mitotane response in ACC. Our findings suggest that responders exhibit features of aggressive ACC, with upregulated cell cycle and collagen genes and suppressed mitochondrial proteins.