Delineating the Spectrum of Pituitary Adenoma Based on the WHO 2017 Classification.

BACKGROUND: The WHO 2017 classification of endocrine tumors incorporates lineage-specific transcription factors (TF) and hormone expression for the classification of pituitary adenoma (PA). There is paucity of reports describing the spectrum of PA based on this classification. OBJECTIVE: The aim of this study was to delineate the spectrum of PA based on WHO 2017 classification of endocrine tumors. MATERIALS AND METHODS: PA diagnosed in the year 2018 were studied. H and E and hormonal immunohistochemistry (IHC) for GH, PRL, ACTH, TSH, FSH, LH, CK, T-Pit and MIB-1 were performed and the results were analyzed. RESULTS: The cohort included 88 cases. M: F ratio was 2:1. Clinically, 22 (25%) were functional and 66 (75%) were non-functional adenomas. Amongst the clinically functional adenomas, GH secreting adenomas were the commonest (68%). Majority (83%) of non-functional adenomas were hormone positive with gonadotroph adenomas being the commonest (72.7%). Eleven (12.5%) PA were clinically and hormonally silent. Three of these showed intense nuclear T-Pit positivity, classifying them under silent corticotroph adenoma. Lineage of the remaining eight adenomas remained undetermined, since, IHC for Pit-1 and SF-1 was not performed. The aggressive adenomas identified by IHC included sparsely granulated somatotroph adenoma, Crooke cell adenoma, silent corticotroph adenoma, densely granulated lactotroph adenoma in men and constituted 17% of the PA. Four (4/88) cases were clinically invasive. CONCLUSION: A large majority of PA including aggressive adenomas can be identified by IHC. Addition of T-Pit helped to identify silent corticotroph adenoma. Pit -1 and SF-1 TF would help identify plurihormonal Pit-1 PA and null cell adenomas.

Genes with 5' terminal oligopyrimidine tracts preferentially escape global suppression of translation by the SARS-CoV-2 NSP1 protein

Viruses rely on the host translation machinery to synthesize their own proteins. Consequently, they have evolved varied mechanisms to co-opt host translation for their survival. SARS-CoV-2 relies on a non-structural protein, Nsp1, for shutting down host translation. However, it is currently unknown how viral proteins and host factors critical for viral replication can escape a global shutdown of host translation. Here, using a novel FACS-based assay called MeTAFlow, we report a dose-dependent reduction in both nascent protein synthesis and mRNA abundance in cells expressing Nsp1. We perform RNA-Seq and matched ribosome profiling experiments to identify gene-specific changes both at the mRNA expression and translation level. We discover a functionally-coherent subset of human genes are preferentially translated in the context of Nsp1 expression. These genes include the translation machinery components, RNA binding proteins, and others important for viral pathogenicity. Importantly, we uncovered a remarkable enrichment of 5' terminal oligo-pyrimidine (TOP) tracts among preferentially translated genes. Using reporter assays, we validated that 5 UTRs from TOP transcripts can drive preferential expression in the presence of NSP1. Finally, we found that LARP1, a key effector protein in the mTOR pathway may contribute to preferential translation of TOP transcripts in response to Nsp1 expression. Collectively, our study suggests fine tuning of host gene expression and translation by Nsp1 despite its global repressive effect on host protein synthesis.