Transferrin Receptor 1 Overexpression Drives Proliferation and Ferroptosis Sensitivity in Glioblastoma: A Potential Therapeutic Vulnerability

Glioblastoma (GBM) is an aggressive CNS malignancy with extensive tumor growth and invasion. Highly proliferating cells require an increased intracellular iron concentration to maintain cell metabolism. We assessed the expression of transferrin receptor 1 (TFR1), the principal iron transporter, in GBM and ascertained its clinicopathological significance, implication in pathobiology, and therapeutic potential. Ninety-four cases of adult-type hemispheric GBM were included, along with 60 cases of IDH-mutant astrocytic and oligodendroglial tumors (grade 2-4) for comparison. The protein and mRNA expression were assessed by immunohistochemistry and qRT-PCR, respectively. We used U87MG and LN229 cell lines for in vitro analysis. TFR1 expression was significantly higher in GBM than in other IDH-mutant/lower-grade diffuse gliomas at mRNA and protein level. The non-tumor brain was negative on immunohistochemistry, and strong immunoreactivity was present only in GBM, indicating its diagnostic significance. SiRNA-mediated knockdown of TFR1 was associated with reduced cell survival, proliferation, migration, invasion, and increased apoptosis in vitro. Ferroptosis induction by RSL3/FIN56 led to increased TFR1 expression and ROS generation. The pro-ferroptotic effect of these drugs could be reversed by TFR1 knockdown. Hence, TFR1 appears to be crucially implicated in the cell survival and proliferation and ferroptosis sensitivity of malignant cells. Temozolomide in combination with siRNA-mediated gene silencing showed a significantly higher antitumor effect than the drug or silencing alone. This may be one of the important therapeutic vulnerabilities of GBM. High TFR1 expression was associated with shorter overall survival in all gliomas together but not in GBM separately.