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Cristina L Ronchi, Erika Peverelli, Sabine Herterich, Isabel Weigand, Giovanna Mantovani, Thomas Schwarzmayr, Silviu Sbiera, Bruno Allolio, Jürgen Honegger, Silke Appenzeller, Andrea G Lania, Martin Reincke, Davide Calebiro, Anna Spada, Michael Buchfelder, Joerg Flitsch, Tim M Strom, and Martin Fassnacht

Context

Alterations in the cAMP signaling pathway are common in hormonally active endocrine tumors. Somatic mutations at GNAS are causative in 30–40% of GH-secreting adenomas. Recently, mutations affecting the USP8 and PRKACA gene have been reported in ACTH-secreting pituitary adenomas and cortisol-secreting adrenocortical adenomas respectively. However, the pathogenesis of many GH-secreting adenomas remains unclear.

Aim

Comprehensive genetic characterization of sporadic GH-secreting adenomas and identification of new driver mutations.

Design

Screening for somatic mutations was performed in 67 GH-secreting adenomas by targeted sequencing for GNAS, PRKACA, and USP8 mutations (n=31) and next-generation exome sequencing (n=36).

Results

By targeted sequencing, known activating mutations in GNAS were detected in five cases (16.1%), while no somatic mutations were observed in both PRKACA and USP8. Whole-exome sequencing identified 132 protein-altering somatic mutations in 31/36 tumors with a median of three mutations per sample (range: 1–13). The only recurrent mutations have been observed in GNAS (31.4% of cases). However, seven genes involved in cAMP signaling pathway were affected in 14 of 36 samples and eight samples harbored variants in genes involved in the calcium signaling or metabolism. At the enrichment analysis, several altered genes resulted to be associated with developmental processes. No significant correlation between genetic alterations and the clinical data was observed.

Conclusion

This study provides a comprehensive analysis of somatic mutations in a large series of GH-secreting adenomas. No novel recurrent genetic alterations have been observed, but the data suggest that beside cAMP pathway, calcium signaling might be involved in the pathogenesis of these tumors.

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Laura-Sophie Landwehr, Jochen Schreiner, Silke Appenzeller, Stefan Kircher, Sabine Herterich, Silviu Sbiera, Martin Fassnacht, Matthias Kroiss, and Isabel Weigand

Background

The response of advanced adrenocortical carcinoma (ACC) to current chemotherapies is unsatisfactory and a limited rate of response to immunotherapy was observed in clinical trials. High tumour mutational burden (TMB) and the presence of a specific DNA signature are characteristic features of tumours with mutations in the gene MUTYH encoding the mutY DNA glycosylase. Both have been shown to potentially predict the response to immunotherapy. High TMB in an ACC cell line model has not been reported yet.

Design and methods

The JIL-2266 cell line was established from a primary ACC tumour, comprehensively characterised and oxidative damage, caused by a dysfunctional mutY DNA glycosylase, confirmed.

Results

Here, we characterise the novel patient-derived ACC cell line JIL-2266, which is deficient in mutY-dependent DNA repair. JIL-2266 cells have a consistent STR marker profile that confirmed congruousness with primary ACC tumour. Cells proliferate with a doubling time of 41 ± 13 h. Immunohistochemistry revealed positivity for steroidogenic factor-1. Mass spectrometry did not demonstrate significant steroid hormone synthesis. JIL-2266 have hemizygous mutations in the tumour suppressor gene TP53 (c.859G>T:p.E287X) and MUTYH (c.316C>T:p.R106W). Exome sequencing showed 683 single nucleotide variants and 4 insertions/deletions. We found increased oxidative DNA damage in the cell line and the corresponding primary tumour caused by impaired mutY DNA glycosylase function and accumulation of 8-oxoguanine.

Conclusion

This model will be valuable as a pre-clinical ACC cell model with high TMB and a tool to study oxidative DNA damage in the adrenal gland.