Endocrine Abstracts

Background: Pituitary adenomas (PAs)/Pituitary Neuroendocrine Tumors (PitNETs) are a complex and heterogeneous group of lesions. Genetic and epigenetic studies have been performed to identify predictors of treatment outcome.

Study aim: To profile clinically non-aggressive (NA) and aggressive (A) PAs/PitNETs, and carcinomas for somatic mutations and epigenetic alterations of genes involved in cell proliferation/differentiation, miRNA/lncRNA-post-transcriptional regulators, and therapy targets.

Patients and Methods: 64 NA and 41 A PAs/PitNETs (40 males; 21 ACTH-, 50 FSH-/lH-, 16 GH-, 3 GH/PRL-, 12 PRL-secreting; 1 null cell; 2 plurihormonal PIT-1+) and 6 carcinomas (3 males; 3 ACTH-, 2 PRL- and 1 FSH/lH-secreting) treated by endoscopic surgery from 2003 to 2017, with ≥1-year follow-up were included. Clinico-radiological and histological data were collected. Somatic mutations of 17, and DNA methylation of 22 genes were assessed in fresh frozen and/or formalin-fixed paraffin-embedded tumor tissue (20% VAF and 100x coverage in both strands). Ten normal pituitaries were used as control.

Results: 6/64 (9.4%) NA and 9/41 (22%) A PAs/PitNETs and 1/6 (16.6%) carcinoma showed ≥1 mutation ( P=0.0024), involving TP53 ( n=3; 2.7%), NOTCH1 (n=4; 3.6%), AIP ( n=6; 5.4%), USP8 ( n=3; 2.7%) or PIK3CA ( n=3; 2.7%). Carcinomas presented the highest methylation levels of PARP15, LINC00599, MIR193a, MIR137HG and ZAP70 followed by A and NA PAs/PitNETs (P<0.05). LRRTM1, NTM, CDH1 were hypermethylated in carcinomas only. GNAS, PDCD1 and AIP methylation was higher in NA than A PAs/PitNETs and carcinomas (P<0.05). Hypermethylation could silence genes and reduce the expression of PARP15, LINC00599 and miR-193a, thus inducing cancer cells growth and proliferation by modulating p53 expression and related apoptotic pathways in aggressive tumors. PDCD1 methylation could predict the response to anti-PD1 and PDL-1 inhibitors, as well as the escape of tumor cells from immunological control. Methylation levels of MAGEA family, UXT and FLNA gens, interacting with the androgen receptor (AR) and p53, differed between males and females in PAs/PitNETs and carcinomas, supporting the role of AR expression and the synergy of epigenetics and somatic gene mutations in pituitary tumorigenesis.

Conclusions: Different profiles of somatic gene mutations and methylation were identified in NA and A PAs/PitNETs, and carcinomas. Altered methylation appears an early event that could contribute to tumor aggressiveness, response to treatment and progression to carcinoma directly, or indirectly by inducing gene mutation. Involvement of X-linked genes could underly gender variability in tumor behavior. These data reinforce the importance of combining molecular analysis with clinico-radiological and pathological data in attempting to predict tumor behavior.