Low Protein Expression of ATRX and ZNRF3 as a Novel Prognostic Marker of Adult Adrenocortical Carcinoma

Abstract Adrenocortical carcinoma (ACC) is a rare malignant neoplasia that is usually associated with a dismal prognosis. ACC overall survival (OS) depends on the particular biology of the tumor. Pan-genomic studies have demonstrated the involvement of ATRX and ZNRF3 genes in adrenocortical tumorigenesis. Aim: To evaluate ATRX and ZNRF3 protein expression in a large cohort of adults with ACC followed at a single tertiary referral center to establish the prognostic value of these genes. Methods: Two pathologists analyzed immunohistochemically-stained slides for ATRX and ZNRF3 (blinded assessment) proteins using tissue microarrays comprising tissue samples from 82 ACC (kappa 0.854; P<0.001). Cohort: female 76.8%; median age 38.2 (15.3–85.4) years; 67.5% of patients presented with hypercortisolism; ENSAT stage 1, 11.12%; 2, 44.44%; 3 and 4: (44.44%). The median follow-up time was 39.58 (1.4–406.8) months; 39 patients died during this period. Low protein expression was defined as follows: ATRX, when < 25% of tumor cells were immunoreacted; ZNRF3, when a score < 3 (extension + intensity) was established. Results: Low ATRX protein expression was positively associated with the age at diagnosis (P< 0.001), and it was negatively correlated with tumor size (P=0.020) and with Weiss score (P=0.033). Low ZNRF3 protein expression correlated negatively with tumor weight (P=0.026), with tumor size (P= 0.005), and with Weiss score (P=0.002). Regarding OS, the low protein expression of ATRX and ZNRF3 was associated with a decrease of OS (P=0.045 and P=0.012, respectively). The Cox model for ATRX protein expression showed a HR of 0.521 (95% CI 0.273–0.997; P=0.049); for ZNRF3 expression, HR = 0.441 (95% CI 0.229–0.852; P=0.015). The combined protein expression of both genes was also associated with a decrease in OS in this cohort (P=0.02). The high ATRX and ZNRF3 protein expressions were positively associated with optimistic recurrence-free survival (P=0.027, P=0.005, respectively). Conclusion: The knowledge of tumor biology is an important step to deliver personalized medicine, affording the opportunity to design better clinical approaches and targeted therapies. This study brought pan-genomic studies closer to clinical practice with an easily accessible tool for stratifying patients with ACC. We demonstrated that low levels of protein expression of ATRX and ZNRF3 are negative prognostic markers of ACC.