Targeting HIF-1α promotes ferroptosis and boosts antitumor immunity in MSS colorectal cancer.

The lack of effective therapeutic options available for microsatellite stable (MSS) colorectal cancer (CRC) remains a significant clinical challenge. Interestingly, chemotherapy-resistant cancer cells can be induced to undergo ferroptosis, prompting our investigation into RSL3, a potent ferroptosis inducer, in MSS CRC cells. Our findings revealed that while RSL3 suppressed the growth of MSS CRC cells, a subset displayed resistance. Single-cell sequencing uncovered an aberrant activation of hypoxia pathways in RSL3-resistant MSS CRC cells. Inhibiting HIF-1α, the key transcription factor driving hypoxia signaling, restored RSL3 sensitivity in these resistant cells; moreover, this sensitivity was attenuated upon HIF-1α overexpression. Chromatin immunoprecipitation assays further demonstrated that in RSL3-resistant cells, HIF-1α was enriched at the promoter of P4HA1, a gene implicated in ferroptosis resistance, thereby enhancing its expression. Additionally, in vivo experiments using syngeneic transplantation of CT26 cells in mice revealed that combining RSL3 with an HIF-1α inhibitor markedly enhanced tumor suppression and metastasis prevention, concomitant with increased intratumoral infiltration of CD8(+) T cells and CD86(+) macrophages. Notably, the combination enhanced the antitumor response of anti-PD1, a treatment otherwise ineffective on this tumor. These findings suggest that targeting HIF-1α represents a promising therapeutic strategy when used in conjunction with a ferroptosis inducer for the treatment of MSS CRC.