Intratumor heterogeneity of prognostic DNA-based molecular markers in adrenocortical carcinoma

Background: The prognosis of adrenocortical carcinoma (ACC) is heterogeneous. Genomic studies have identified ACC subgroups characterized by specific m olecular alterations, including features measured at DNA level (somatic mutations, chromosome alterations, DNA methylation), which are closely associated with outcome. The aim of this study was to evaluate intratumor heterogeneity of prognostic molecular markers at the DNA level. Methods: Two different tissue samples (primary tumor, local recurrence o r metastasis) were analyzed in 26 patients who underwent surgery for primary or recurrent ACC. DNA-related biomarkers with prognostic role were investigated i n frozen and paraffin-embedded samples. Somatic mutations of p53/Rb and Wnt/β-catenin pathways were assessed using next-generation sequencing (n = 26), chromosome alteration profiles were determined using SNP arrays (n = 14) and methylation profiles were determined using four-gene bisulfite pyrosequencing (n = 12). Results: Somatic mutations for ZNRF3, TP53, CTNN1B and CDKN2A were found in 7, 6, 6 and 4 patients, respectively, with intratumor heterogeneity in 8/26 patients (31%). Chromosome alteration profiles were ‘Noisy’ (numerous and anarch ic alterations) in 8/14 and ‘Chromosomal’ (extended patterns of loss of heterozygo sity) in 5/14 of the study samples. For these profiles, no intratumor heterogenei ty was observed. Methylation profiles were hypermethylated in 5/12 and non-hyperm ethylated in 7/12 of the study samples. Intratumor heterogeneity of methylation p rofiles was observed in 2/12 patients (17%). Conclusions: Intratumor heterogeneity impacts DNA-related molecular markers. While somatic mutation can differ, prognostic DNA methylation and chro mosome alteration profile seem rather stable and might be more robust for the prog nostic assessment.