miR-644a is a tumor cell-intrinsic mediator of sex bias in glioblastoma

Background: Biological sex is an important risk factor for glioblastoma (GBM), with males having a higher incidence and poorer prognosis. The mechanisms for this sex bias are thought to be both tumor intrinsic and tumor extrinsic. MicroRNAs (miRNAs), key posttranscriptional regulators of gene expression, have been previously linked to sex differences in various cell types and diseases, but their role in the sex bias of GBM remains unknown.

Methods: We leveraged previously published paired miRNA and mRNA sequencing of 39 GBM patients (22 male, 17 female) to identify sex-biased miRNAs. We further interrogated a separate single-cell RNA-sequencing dataset of 110 GBM patients to examine whether differences in miRNA target gene expression were tumor cell-intrinsic or tumor cell extrinsic. Results were validated in a panel of patient-derived cell models.

Results: We identified 10 sex-biased miRNAs (p _adjusted < .1), of which 3 were more highly expressed in males and 7 more highly expressed in females. Of these, miR-644a was higher in females, and increased expression of miR-644a target genes was significantly associated with decreased overall survival (HR 1.3, P = .02). Furthermore, analysis of an independent single-cell RNA-sequencing dataset confirmed sex-specific expression of miR-644a target genes in tumor cells (P < 10^-15). Among patient-derived models, miR-644a was expressed a median of 4.8-fold higher in females compared to males.

Conclusions: Our findings implicate miR-644a as a candidate tumor cell-intrinsic regulator of sex-biased gene expression in GBM.