CSIG-20. LIPOCALIN-2 DRIVES CELL-INTRINSIC FUNCTIONS IN GLIOBLASTOMA

Abstract Glioblastoma (GBM) continues to persist despite aggressive therapies, many of which are cytotoxic, and therapeutic failure is driven, in part, by the tumor cell’s ability to evade multiple forms of cell death, including ferroptosis. Lipocalin-2 (LCN2) functions to sequester iron and is considered an inflammatory marker through its function of limiting iron for bacterial usage; it has also been described to have pro and anti-tumorigenic effects depending on environmental iron status. In previously published studies in brain metastases, LCN2 promotes tumor cell proliferation by sequestering iron for cancer cells growth and survival, but the mechanisms of how LCN2 contributes to GBM progression is unknown. LCN2 expression in patient data revealed that high LCN2 expression is associated with reduced survival in GBM patients. A survey of mouse glioma models demonstrated a range of LCN2 secretion across models with KR158 and CPA being high and medium LCN2 secretors. LCN2 short hairpin knockdown of KR158 and CPA and decreased tumor cell viability and proliferation. Furthermore, when both KR158 and CPA control versus LCN2 knockdown cells were orthotopically implanted into mice, survival was increased. To understand if LCN2 impacted cell death dynamics, we investigated various cell death mechanisms and found that LCN2 knockdown increases tumor susceptibility to ferroptotic death by sensitizing cells to lipid peroxidation as well as reducing key anti-ferroptotic proteins GPX4 and xCT. To elucidate downstream mechanisms, we performed a phosphorylation array and discovered that phosphorylation of AXL, which has recently been linked to ferroptosis, is decreased with LCN2 knockdown. Moreover, AXL phosphorylation was localized to the nucleus, indicating that LCN2 knockdown attenuates AXL processing and downstream signaling. Overall, these findings indicate that LCN2 in GBM promotes tumor cell growth through AXL signaling and evasion of ferroptotic death, ultimately revealing a novel signaling network that can be leveraged for future therapeutic development.