Resistance to Dopamine Agonists in Pituitary Tumors: Molecular Mechanisms

Area of Science:

• Endocrinology
• Neuro-oncology
• Molecular Medicine

Background:

• Pituitary neuroendocrine tumors (PitNET) are common intracranial tumors, with prolactin-secreting adenomas being the most prevalent.
• Dopamine agonists (DAs) are the primary medical therapy for prolactinomas, effectively reducing tumor size and hormone secretion by targeting the dopamine receptor type 2 (D2DR).
• DAs are also used off-label for other PitNET expressing D2DR, but resistance can occur in a subset of patients.

Purpose of the Study:

• To review the molecular mechanisms underlying resistance to dopamine agonist therapy in pituitary neuroendocrine tumors (PitNET).
• To elucidate the molecular events that lead to unsuccessful DA therapy in PitNET patients.

Main Methods:

• Mini-review of current literature on molecular mechanisms of DA resistance in PitNET.
• Analysis of molecular events affecting dopamine receptor (DR) expression and function.

Main Results:

• Dopamine receptor (DR) expression is crucial for DA efficacy in PitNET.
• Several molecular events can impair DA therapy by negatively affecting DR membrane expression, including down-regulation and altered intracellular trafficking.
• Disruptions in DR signal transduction pathways also contribute to DA resistance.

Conclusions:

• Resistance to dopamine agonists in PitNET is a complex issue involving multiple molecular mechanisms.
• Understanding these mechanisms, particularly those affecting dopamine receptor expression and signaling, is key to improving treatment outcomes for PitNET patients.
• Further research is needed to fully elucidate these pathways and develop strategies to overcome DA resistance.