Endocrine Abstracts

Introduction

Dysregulation of alternative splicing is emerging as a new hallmark of cancer. This dysregulation may originate from mutations and/or altered expression of specific components of the splicing machinery. Indeed, our group has shown that the expression profile of the splicing machinery is altered in several types of cancer, including endocrine-related cancers. However, to date, the status of alternative splicing and its putative dysregulation has not been reported in pulmonary neuroendocrine neoplasms (LungNENs), specifically typical and atypical pulmonary carcinoids.

Aims

The aim of this work was to explore the potential dysregulation of the splicing machinery in LungNENs and whether it contributes to splicing alterations and pathophysiology in these tumors.

Methods

A custom-made qPCR array was used to measure the expression of 45 components of the splicing machinery in tumor and non-tumor adjacent tissue samples of a cohort of 33 typical and atypical pulmonary carcinoids patients. Results were validated using a publicly available external cohort of 51 patients (GSE108055). Further analyses were made with immunohistochemistry in paraffin-embedded samples. Statistical analyses were made to explore the potential associations between expression levels of the components of the splicing machinery measured and relevant clinical parameters of patients. In addition, alternative splicing analyses were performed in an RNAseq of an independent cohort of 20 patients, to test whether intratumoral expression of key dysregulated components of the splicing machinery could be associated to an alteration of alternative splicing of specific molecular pathways.

Results

One third of the components of the splicing machinery were dysregulated in pulmonary carcinoids. Remarkably, a discrete subset of specific components of the major and minor spliceosome, as well as key splicing factors displayed significant associations to key clinical parameters, including tumor stage, node invasion and/or tumor dissemination. These results were validated in the external cohort of patients, and key components were selected based on their relevance and the association to clinical parameters. Alternative splicing analyses in the available RNAseq showed that the expression of these key components was correlated to altered patterns of alternative splicing.

Conclusions

Our results show that the splicing machinery is profoundly dysregulated in pulmonary carcinoids, where some of its components are associated to key clinical parameters of tumor malignancy. These results pave the way to employ novel avenues to study pulmonary carcinoids and discover new diagnostic, prognostic and therapeutic tools.

Fundings

MINECO (PID2019–105201RB-I00, FPU18/02275), Junta de Andalucía (BIO-0139) and CIBERobn.