Summary: Glioblastoma, the most common and deadly brain cancer, shows clear differences between men and women in how often it occurs, how it responds to treatment, and survival. New research has uncovered a sex-specific biological mechanism: the neurotransmitter GABA (gamma-aminobutyric acid) selectively reprograms a subset of immune cells in females, creating an immunosuppressive environment that fuels tumor growth. This discovery points to potential sex-specific immunotherapies for glioblastoma.
Key Facts
- Distinct immune cell patterns: Male glioblastoma is associated more with monocytic MDSCs, while granulocytic MDSCs correlate with poorer outcomes in female patients.
- GABA-driven metabolic shift: GABA alters the metabolism of granulocytic myeloid-derived suppressor cells (gMDSCs) in females, increasing their ability to suppress anti-tumor T cells.
- Therapeutic specificity: Blocking GABA receptors reversed this immunosuppressive effect and improved survival in female preclinical models but had no impact in male models.
- Human tissue confirmation: Biopsies from female glioblastoma patients showed higher levels of GABA and GABA receptors in granulocytic MDSCs compared with male samples.
- Broader oncology relevance: Because suppressive MDSCs are recruited in many aggressive cancers, targeting GABA-mediated metabolic pathways may have applications beyond glioblastoma.
Source: University of Miami
Men and women differ in susceptibility, symptoms, and treatment responses for many diseases. The immune system, which plays a central role in cancer progression and response to therapy, is also influenced by biological sex. These differences can affect the success of immunotherapies and influence clinical outcomes.
Glioblastoma (GBM), the deadliest primary brain tumor, occurs more often and carries poorer prognosis in men than in women. Yet the biological reasons for these sex disparities have been poorly understood. A multidisciplinary team at Sylvester Comprehensive Cancer Center, part of the University of Miami Miller School of Medicine, has now identified a sex-specific immune mechanism that promotes glioblastoma growth in females.
Published in Nature Cancer and led by Defne Bayik, Ph.D., with Asmita Pathak, Ph.D., the study focused on myeloid-derived suppressor cells (MDSCs). MDSCs are immune cells that, under normal conditions, limit inflammation and prevent excessive immune responses. Tumors, however, often co-opt these cells to suppress anti-tumor T cell activity and protect malignant cells from immune attack.
Prior work had shown sex-linked differences in MDSC populations within glioblastoma. Male tumors tended to contain higher levels of monocytic MDSCs (mMDSCs), while granulocytic MDSCs (gMDSCs) were more prominent and clinically relevant in females. The current study asked why gMDSCs support tumor growth in females but not in males, and whether this difference could be targeted therapeutically.
The researchers tested candidate drugs and signaling pathways that might regulate gMDSC activity and identified GABA signaling as a compelling candidate. In laboratory experiments, exposure to GABA selectively reprogrammed the metabolism of female gMDSCs—upregulating pathways that drive immunosuppression—while male gMDSCs and mMDSCs did not display this response. Blocking the GABA receptor (GABBR) in female preclinical glioblastoma models reduced gMDSC-mediated suppression and extended survival; the same intervention had no measurable benefit in male models.
To validate these findings in humans, the team analyzed tumor biopsies from patients with glioblastoma. Female tumor samples showed higher GABA levels and increased expression of GABA receptors within gMDSCs compared with male samples. These human data mirrored the laboratory results and support the idea that GABA signaling drives a female-specific immunosuppressive program in glioblastoma.
Mechanistically, the study links GABBR activation to upregulation of pathways involved in L-arginine transport and nitric oxide synthesis (including NOS2), which in turn enhances the T cell–suppressive function of gMDSCs in females. Pharmacologic antagonism of GABBR reduced NOS2 activity and diminished the suppressive capacity of tumor-infiltrating gMDSCs in female mice.
These results have two major implications. First, they underscore the importance of considering sex as a biological variable in cancer research and drug development. Treatments effective in one sex may be ineffective or irrelevant in the other if tumors exploit different immune pathways. Second, they identify the GABA–gMDSC axis as a potential, female-specific therapeutic target for glioblastoma. Given the role of MDSCs in other cancers, inhibitors of this pathway may also be valuable in additional tumor types after careful evaluation.
“Glioblastoma may be more common in men, but women still represent a substantial portion of patients,” said Bayik. “Understanding sex-specific mechanisms lets us design therapies that are tailored and more likely to benefit each patient.” Ongoing work aims to define the underlying reasons for sex differences in gMDSC metabolism and to explore targeted interventions that could translate to clinical trials.
Key Questions Answered:
A: MDSCs normally act as immune regulators that dampen excessive inflammation and protect tissues from immune-driven damage. In the tumor microenvironment, however, glioblastoma recruits these immature myeloid cells and converts them into an immunosuppressive shield. These tumor-associated MDSCs block T cell activity and other anti-tumor responses, allowing cancer cells to escape immune surveillance and grow unchecked.
A: The study found a sex-specific wiring of immune cells: female granulocytic MDSCs express higher levels of GABA receptors and are uniquely responsive to GABA. When GABA binds these receptors in female gMDSCs, it triggers a metabolic reprogramming that increases their immunosuppressive functions. Male tumors rely more on monocytic MDSCs, which do not undergo this GABA-driven shift, leaving their behavior unaffected by the neurotransmitter.
A: The results challenge one-size-fits-all approaches by showing that male and female glioblastomas can use different immune mechanisms to evade the immune system. Therapies targeting the GABA–gMDSC pathway could be effective in female patients but not in males, highlighting the need for sex-informed clinical trials and tailored treatment strategies to improve outcomes for both sexes.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full by the editorial team.
- Additional context and clarifications were added by staff to aid reader understanding.
About this brain cancer research news
Author: Sandy Van
Source: Sylvester Comprehensive Cancer Center, University of Miami
Contact: Sandy Van – Sylvester Comprehensive Cancer Center
Image credit: Neuroscience News
Original Research: Pathak A., Bayik D., et al., “GABA signaling activation drives glioblastoma progression in female mice through myeloid-derived suppressor cells.” Nature Cancer. DOI: 10.1038/s43018-026-01192-5. Open access.
Abstract (summary): Sex differences in immune responses shape cancer outcomes and therapy effects in glioblastoma. This study identifies GABA as a female-specific driver of immune suppression in GBM. Activation of GABA receptor B enhances the T cell–suppressive function of granulocytic MDSCs from female mice by upregulating L-arginine transport and nitric oxide synthase 2 (NOS2) pathways. GABBR agonists promote tumor growth via gMDSCs in female preclinical models, while GABBR antagonists extend survival and reduce NOS2 in tumor-infiltrating gMDSCs only in females. Human GBM immune cells from female patients show enriched GABA-related signatures and higher GABA concentrations than male counterparts. These results support evaluating GABA pathway inhibitors as sex-informed strategies for cancer immunotherapy.