Assessing the immune gene and cellular networks within human non-functioning and growth-hormone secreting pituitary adenomas via transcriptomic and pathway analysis

EJ. Spiteri*^a (Ms), JP. Ebejer^a (Dr), R. Formosa^b (Dr), NP. Pace^a (Dr), M. Gruppetta^a (Dr), J. Vassallo^a (Prof), D. Saliba^a (Prof)

^a University of Malta, Msida, MALTA ; ^b University of Malta - Queen Mary University London Campus, Msida, MALTA

* emma.j.spiteri.16@um.edu.mt

Human pituitary neuroendocrine tumours (PitNETs), or pituitary adenomas, are comprised of various subtypes namely functioning pituitary adenomas (FPAs) including GH-secreting adenomas (GHPAs) and non-functioning pituitary adenomas (NFPAs). Despite being the second-most common type of intracranial tumour, the molecular components and cellular processes implicated in the proliferation, maintenance, and development of these tumours have not yet been clearly identified. This is especially the case for their immune gene and cellular networks.

To address this issue, we implemented transcriptomic analysis to obtain a list of differentially expressed genes (DEGs) sourced from GHPA (n=3) and NFPA (n=7) RNA-sequencing data. A cohort of genes was then selected for further processing using ShinyGO, KEGG and Reactome for pathway analysis, and ‘My Gene Set’ from the Immunological Genome Project and CIBERSORTx to observe the baseline expression data for these genes within a subset of immune cells (i.e. B-cells, abT-cells, gdT-cells, innate lymphocytes, dendritic cells, macrophages, and monocytes).

A total of 4039 DEGs resulted from transcriptomic analysis of which 2,274 were upregulated in NFPAs in comparison to GHPAs and 1,765 were upregulated in GHPAs in comparison to NFPAs. These included ELMO1, CD40, VAV2, SHH, and IL15. Pathway analysis showed that these genes were predominantly implicated in a number of immune pathways including natural killer cell-mediated cytotoxicity, NF-kappa B signaling pathway, interferon-gamma signaling, and neutrophil degranulation. Furthermore, out of all immune cells assessed B-cells had the lowest overall expression values for the DEGs. All the other immune cell types assessed appeared to have a similar trend in expression values throughout.

Through transcriptomics and pathway analysis, this study highlighted distinct immune gene expression patterns in GHPAs and NFPAs. This suggests that there are numerous well-known and novel DEGs and pathways within immune gene and cellular networks that could have a probable role in PitNET functioning. Currently, we are performing gene prioritization to select a subset of genes to be used as candidates for subsequent validation via qRT-PCR and other related techniques.

The author has declared no conflict of interest.