Researchers at Cleveland Clinic have discovered that androgen hormones such as testosterone can limit the growth of glioblastoma tumors in men. Results published today in Nature show that men receiving testosterone supplements for reasons unrelated to cancer showed a 38% lower risk of death compared to patients not taking these supplements.
These findings are surprising because testosterone is known to contribute to the growth of other forms of cancer in men, such as prostate cancer, where hormone therapy is used routinely to decrease levels of androgen hormones and block cancer progression. However, these hormones were found to play a very different role in glioblastoma, an aggressive form of brain cancer that is more commonly diagnosed in men.
“This outcome is a welcome surprise and may potentially offer a lead for new treatments for a kind of cancer that is deadlier in men,” said Anthony Letai, MD, PhD, director of NIH’s National Cancer Institute (NCI).
In a mouse model of glioblastoma the researchers found that reducing levels of androgen hormones induced overdrive on the hypothalamus-pituitary-adrenal (HPA) axis, a brain circuit that controls reactions to stress and many physiological processes including hormone secretion. This caused a spike in stress hormones that led the brain to reinforce the protective function of the blood-brain barrier and create an immunosuppressive environment in the brain, reducing the ability of immune cells to fight against the tumor.
“The brain has evolved to keep stuff out and that includes immune cells from elsewhere in the body. It’s a delicate tissue that often doesn’t want huge immune reactions,” said Justin D. Lathia, PhD, professor of cancer sciences and scientific director of the Brain Tumor Center at Cleveland Clinic.
Importantly, this effect was only observed in male mice. In females, changes in testosterone levels did not produce the same effects.
These findings were then confirmed in human samples obtained from 1,300 men with glioblastoma participating in the NIH database Surveillance, Epidemiology, and End Results (SEER). An analysis showed that men who received supplemental testosterone for reasons unrelated to their glioblastoma diagnosis had a 38% lower risk of death than other male patients.
More research will be needed to better understand the complex pathway activated by testosterone and other androgen hormones. While the current study identified inflammation in the hypothalamus as a potential trigger of HPA axis activation, future work will look for the exact mechanism glioblastoma tumors employ to induce this reaction from an entirely different region of the brain.
Lathia noted that, although these results do not establish a causal link between testosterone and patient outcomes for men diagnosed with glioblastoma, the study opens the door for future clinical trials that dive deeper into the link between androgen hormones and glioblastoma tumor growth. He added, “An obvious follow-up study would be to find out whether androgen deprivation, which is a common treatment for cancer, is actually detrimental for glioblastoma.”
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