New models for interrogating the impact of sex chromosomes and sex hormones on glioblastoma

Washington University, Saint Louis MO

Investigators

Abstract

PROJECT SUMMARY There is a sex disparity seen in cancers throughout the body where males have both a higher incidence and a higher mortality than females. This phenomenon is seen in glioblastoma (GBM) that comprises over 50% of brain tumors and are characterized by resistance to therapies and a dismal prognosis. This is not only true for adults, but children as well, suggesting that factors other than the effects of sex hormones may be playing a role in this phenomenon. Because enhanced nutrient consumption and metabolism are critical to enhanced tumorigenesis and its effect on poor patient outcomes, our group investigates the effects of biological sex on cancer metabolism as a driver for the sex disparity where male tumors engage in more carbohydrate and amino acid metabolism concomitant with higher PI3K-Akt-mTOR signaling that are associated with faster tumor growth and worse survival. Intriguingly, the metabolic sex differences that we observe in human and rodent GBM are also present in cell lines, suggesting a cell-intrinsic component. This could be due to direct sex chromosome effects and/or epigenetic tissue patterning effects from exposure to in utero gonadal sex hormones. Unfortunately, laboratory models for rigorous mechanistic sex differences research in GBM are lacking. This proposal will develop novel GBM models to address the hypothesis that sex chromosomes and sex hormones are both drivers of GBM phenotype, measured by proliferation and cellular metabolism. In the first Aim, we will use the Four Core Genotypes (FCG) mouse model to define the contributions of sex chromosomes and organizational effects of in utero exposure to sex hormones to astrocyte metabolism before and after mesenchymal GBM transformation. First, wildtype FCG astrocytes will be harvested from P1 pups and assayed for sex differences across key metabolic and signaling pathways important for cancer. CRISPR-Cas9 of FCG astrocytes will then be used to generate the mesenchymal subtype GBM models Nf1-/-Tp53-/- (proof of principle with strong sex-specific phenotype) and Pten-/-Tp53-/- (to test effects of Pten deletion on sex differences in PI3K- Akt-mTOR signaling). Cell lines and allografted tumors will be assayed for growth, metabolism and gene expression. Novel, advanced diffusion MR imaging from our lab will be used to noninvasively assay changes in the tumor microenvironment. In the second aim, we will develop human induced pluripotent stem cell (iPSC) models to evaluate the contributions of sex chromosomes to cellular differentiation and mesenchymal GBM transformation. NF1-/-TP53-/- transformed NPC will then be generated from iPSC using published methods developed by our team. NF1-/-TP53-/- NPC will be orthotopically xenografted into mice. Cell lines and tumors will be assayed for growth, metabolism and gene expression including imaging-based growth and tumor microenvironment assessment as above. This research proposal is innovative because it develops the necessary models to investigate the effects of biological sex on cancer biology and patient outcomes. This R21 presents a clear path to a future R01 that will involve the expansion of cell and animal models to study sex chromosome and gonadal effects on GBM, advancing the NIH’s initiative to incorporate sex as a critical biological variable.