Simultaneous Inhibition of LSD1 and TGF-β Enables Eradication of Poorly Immunogenic Tumors with anti-PD-1 Treatment

Epigenetic regulators are a class of promising targets in the combination with immune checkpoint inhibitors for cancer treatment, but the impact of the broad effects of perturbing epigenetic regulators on tumor immunotherapy remains to be fully explored. Here we show that ablation of the histone demethylase LSD1 in multiple tumor cells induces TGF-β expression, which exerts an inhibitory effect on T cell immunity through suppressing the cytotoxicity of intratumoral CD8+ T cells and consequently dampens the antitumor effect of LSD1 ablation-induced T cell infiltration. Importantly, concurrent depletion of LSD1 and TGF-β in combination with PD-1 blockade significantly increases both CD8+ T cell infiltration and cytotoxicity, leading to eradication of poorly immunogenic tumors and a long-term protection from tumor re-challenge. Thus, combining LSD1 inhibition with blockade of TGF-β and PD-1 may represent a promising triple combination therapy for treating certain refractory tumors. B16 tumors of different genetic settings (scramble, Lsd1 KO, Tgfb TKO and Lsd1/Tgfb QKO) were implanted to wild-type mice for 14 days. Tumors were harvested and tumor-infiltrating lymphocytes were enriched, then subjected to CD8+ T cells isolation by microbeads and positive selection. Afterwards, CD3+CD8+ cells were sorted by FACS. Total RNA was extracted and subjected to polyA+ RNA purification, before used for making library. The prepared libraries were sequenced at 150bp from both ends.