A recent article published in Cancer Discovery (Bayik, 2020, Cancer Discov) highlights disparities in immune system functions between male and female glioblastoma patients that may underlie some of the observed sex differences in cancer incidence, prognosis and treatment response. Defne Bayik, PhD a postdoctoral fellow in Justin Lathia, PhD's lab at Cleveland Clinic Lerner Research Institute, and colleagues from Cleveland Clinic, Case Western Reserve University, University Hospitals, The University of Southern Denmark, Moffitt Cancer Center, and Northwestern University found that monocytic myeloid-derived suppressor cells (MDSC) were enriched in the tumors of male mice, but not female mice. The findings of the work reveal a previously unknown explanation for sex differences in glioblastoma and demonstrates how this knowledge may be therapeutically exploitable. Case Comprehensive Cancer Center members Ahmad Khalil, PhD, Tae Hyun Hwang, PhD, Manmeet Ahluwalia, MD, Feixiong Cheng, PhD, and Justin Lathia, PhD also contributed to the work.