A Study of Alternative TrkA Splicing Identifies TrkAIII as a Novel Potentially Targetable Participant in PitNET Progression
by
, , , , , , , , , , , , , , and
Maddalena Sbaffone
1,†,
Marie-Lise Jaffrain-Rea
1,2,†,
Lucia Cappabianca
1,
Francesca Carbonara
1,
Francesca Gianno
2,3,
Tiziana Feola
2,4,
Marianna Ruggieri
1,
Veronica Zelli
1,
Rita Maccarone
1
,
Stefano Guadagni
1,
Marco Clementi
1,
Antonietta Arcella
2,
Vincenzo Esposito
2,5,
Giulia Carozza
1,
Ilaria Martelli
1,
Antonietta Rosella Farina
1,‡ and
Andrew Reay Mackay
1,*,‡ 1
Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, Via Vetoio, 67100 L’Aquila, Italy
2
Neuromed, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), 86077 Pozzilli, Italy
3
Department of Radiological, Oncological and Pathological Sciences, La Sapienza University of Rome, 00185 Rome, Italy
4
Department of Experimental Medicine, La Sapienza University of Rome, 00185 Rome, Italy
5
Department of Neurology and Psychiatry, La Sapienza University of Rome, 00185 Rome, Italy
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
‡
These authors contributed equally to this work.
Biology 2024, 13(3), 171; https://doi.org/10.3390/biology13030171
Submission received: 25 January 2024
/
Revised: 1 March 2024
/
Accepted: 5 March 2024
/
Published: 7 March 2024
(This article belongs to the Special Issue Molecular Biology of Neuroendocrine Tumors: Pathogenesis, Diagnosis and Treatment)
Simple Summary
Pituitary neuroendocrine tumors (PitNETs) develop from anterior pituitary cells and, although generally benign, comprise a small subset of therapy-resistant aggressive or metastatic tumors. This highlights the need to identify novel potential therapeutic targets. PitNETs have low rates of somatic mutation and their pathogenesis is poorly understood. PitNETs are associated with conditions linked to alternative splicing, which may activate oncogenic pathways, and express the neurotrophin receptor tropomyosin receptor kinase A (TrkA), which exhibits oncogenic alternative TrkAIII splicing in other neuroendocrine tumors. In this study, we report for the first time that alternative TrkAIII mRNA splicing is common in PitNETs and can associate with intracellular TrkAIII activation, identifying TrkAIII as a novel potential targetable oncogenic participant in PitNET pathogenesis and progression.
Abstract
Pituitary neuroendocrine tumors (PitNETs) are generally benign but comprise an aggressive, invasive, therapy-resistant, metastatic subset, underpinning a need for novel therapeutic targets. PitNETs exhibit low mutation rates but are associated with conditions linked to alternative splicing, an alternative oncogene pathway activation mechanism. PitNETs express the neurotrophin receptor TrkA, which exhibits oncogenic alternative TrkAIII splicing in other neuroendocrine tumors. We, therefore, assessed whether TrkAIII splicing represents a potential oncogenic participant in PitNETs. TrkAIII splicing was RT-PCR assessed in 53 PitNETs and TrkA isoform(s) expression and activation were assessed by confocal immunofluorescence. TrkAIII splicing was also compared to HIF1α, HIF2α, SF3B1, SRSF2, U2AF1, and JCPyV large T antigen mRNA expression, Xbp1 splicing, and SF3B1 mutation. TrkAIII splicing was detected in all invasive and most non-invasive PitNETs and was significantly elevated in invasive cases. In PitNET lineages, TrkAIII splicing was significantly elevated in invasive PIT1 PitNETs and high in invasive and non-invasive SF1 and TPIT lineages. Immunoreactivity consistent with TrkAIII activation characterized PitNET expressing TrkAIII mRNA, and invasive Pit1 PitNETs exhibited elevated HIF2α expression. TrkAIII splicing did not associate with SF3B1 mutations, altered SF3B1, SRSF2, and U2AF1 or JCPyV large T antigen expression, or Xbp1 splicing. Therefore, TrkAIII splicing is common in PitNETs, is elevated in invasive, especially PIT1 tumors, can result in intracellular TrkAIII activation, and may involve hypoxia. The data support a role for TrkAIII splicing in PitNET pathogenesis and progression and identify TrkAIII as a novel potential target in refractory PitNETs.
