Whole genome and transcriptome analysis (WGTA) of metastatic adrenocortical carcinoma (mACC).

Abstract

e16123 Background: mACC is a rare disease, and no standard treatments exist beyond cytotoxic chemotherapy and mitotane. Recurrent molecular changes have been described, but their clinical significance is still poorly understood, and whether they can guide treatment is unknown. Methods: The genomic and transcriptomic profiles of 6 pts with mACC were analyzed as part of a prospective molecular profiling clinical trial (NCT02155621). Findings were correlated with histopathological and clinical data. Results: Whole genome sequencing of six ACC tumors and matched normal tissues was performed; whole-transcriptome sequencing was performed on five of the six tumors. All cases met Weiss criteria for ACC (including 1 pt with oncocytic ACC). Profiling revealed gain of function variations in CTNBB1 gene in 3 cases (p.S45A, p.S45P and homozygous deletion of exons 2 and 3). A stop-gained mutation (Q167*) and a homozygous copy loss of TP53 gene was observed in 2 cases; mutations of CTNBB1 and TP53 co-occurred in one case. Variations in other DNA repair genes included germline FANCA Q1362* and somatic BRCA2 E790* stop-gained mutations, and a structural variation in RAD52. Copy number amplification was observed for KDM5A (2/6) and RAD52 (2/6), while NF1 (1/6), CDKN2A (1/6), CDKN2B (1/6) and RB1 (2/6) were subjected to homozygous copy losses. Average ploidy models: one diploid, 4 triploid and one tetraploid case; whole chromosome copy losses and gains were seen in all samples. Three cases showed high homologous repair deficiency scores; associated with respectively, an in-frame deletion of V613 in ATM, a TP53 homozygous loss, and a structural variant of RAD52. All six cases exhibit signature 3 or signature 8. At last follow-up, 2 pts remained alive. Treatments included cytotoxic chemotherapy, mitotane, streptozotocin, sunitinib, avelumab with a SMAC mimetic (NCT02022098), a TTK inhibitor (NCT02792465) on the basis of a CTNNB1 mutation and temozolomide with olaparib on the basis of ATM loss. Conclusions: Our findings recapitulate published data on the molecular profile of mACC and support previous findings of large scale chromosomal variation. We identify new potential drivers in chromatin remodelling, cell cycle, and DNA damage repair genes.