Inhibiting SCD expression by IGF1R during lorlatinib therapy sensitizes melanoma to ferroptosis

Induction of ferroptosis is an emerging strategy to suppress melanoma progression. Strategies to enhance the sensitivity to ferroptosis induction would be a major advance in melanoma therapy. Here, we used a drug synergy screen that combined a ferroptosis inducer, RSL3, with 240 anti-tumor drugs from the FDA-approved drug library and identified lorlatinib to synergize with RSL3 in melanoma cells. We further demonstrated that lorlatinib sensitized melanoma to ferroptosis through inhibiting PI3K/AKT/mTOR signaling axis and its downstream SCD expression. Moreover, we found that lorlatinib's target IGF1R, but not ALK or ROS1, was the major mediator of lorlatinib-mediated sensitivity to ferroptosis through targeting PI3K/AKT/mTOR signaling axis. Finally, lorlatinib treatment sensitized melanoma to GPX4 inhibition in preclinical animal models, and melanoma patients with low GPX4 and IGF1R expression in their tumors survived for longer period. Altogether, lorlatinib sensitizes melanoma to ferroptosis by targeting IGF1R-mediated PI3K/AKT/mTOR signaling axis, suggesting that combination with lorlatinib could greatly expand the utility of GPX4 inhibition to melanoma patients with IGF1R-proficient expression.