Cabergoline-induced NDFIP1 upregulation in pituitary neuroendocrine tumor cells activates mTOR signaling and contributes to cabergoline resistance.

PURPOSE: To investigate the molecular mechanisms underlying resistance to dopamine agonists (DA).

METHODS: LC-MS/MS analysis was performed on rat pituitary neuroendocrine tumors (PitNET) cell line GH3 to identify differentially expressed proteins induced by cabergoline (CAB) treatment. A total of 180 human PITNET samples were subjected to transcriptome analysis. Immunohistochemistry (IHC) was conducted on 29 tumor samples to validate NDFIP1 alteration. A xenograft mouse model was established by subcutaneously injecting GH3 cells, with or without NDFIP1 overexpression, into nude mice to investigate tumor growth. PitNET cell lines were treated with CAB. Cell proliferation was assessed using the CCK-8, and protein expression levels were examined through Western blot analysis.

RESULTS: CAB treatment upregulated FDFT1 and NDFIP1 protein expression in GH3 cells, with NDFIP1 showing a significant positive correlation with tumor size, as confirmed by IHC results. MMQ and GH3 cells overexpressing NDFIP1 exhibited enhanced viability and reduced sensitivity to CAB. In vivo experiments demonstrated that subcutaneous injection of NDFIP1-overexpressing GH3 cells led to enhanced tumor growth compared to parental GH3 cells. Although the total levels of PTEN remained unaltered, NDFIP1 overexpression induced PTEN nuclear translocation, potentially activating the mTOR pathway. This was supported by increased phosphorylation of key mTOR pathway components, including p-AKT and p-4EBP1, in cells overexpressing NDFIP1.

CONCLUSION: CAB treatment induces the upregulation of NDFIP1 in PitNET cells, which correlates with tumor size and contributes to reduced CAB sensitivity, potentially through activation of the mTOR pathway. NDFIP1 as a potential therapeutic target for overcoming DA resistance in PitNET patients.