Stratifying nonfunctional pituitary adenomas into two groups distinguished by macrophage subtypes

Area of Science:

• Immunology
• Endocrinology
• Oncology

Background:

• Tumor-associated macrophages (TAMs) exist as M1 (anti-tumoral) and M2 (pro-tumoral) subtypes.
• The role of TAMs and their subtypes in non-functional pituitary adenomas (NFPAs) is largely unknown.

Purpose of the Study:

• To investigate the presence, subtypes, and functional roles of TAMs in NFPAs.
• To determine the association between TAMs and NFPA characteristics like size, invasiveness, and proliferation.

Main Methods:

• Flow cytometry and qPCR were used to analyze TAMs in 16 NFPA samples.
• In vitro studies assessed the effects of M1 and M2 macrophages on NFPA invasion and proliferation.

Main Results:

• CD11b+ myeloid cells, primarily monocyte-derived TAMs, were abundant in NFPAs.
• Higher CD11b+ cell fractions correlated with increased NFPA size and MIB1 index.
• M2 TAMs were associated with increased NFPA invasion and proliferation, while M1 TAMs were less prevalent in invasive tumors.

Conclusions:

• TAM polarization towards the M2 subtype promotes NFPA proliferation and invasion.
• NFPA growth may involve an M2 TAM-driven phase followed by a slower growth phase with M1 polarization.
• Targeting TAMs could offer novel therapeutic strategies for NFPAs.