PRMT1 and neoplasm: To investigate how PRMT1 regulates PD-L1 expression, we next generated multiple mouse tumors cells, including CT26, MC38, 4T1, and B16, that stably expressed tet-inducible shPrmt1 (Supplementary Fig. 6a–d), and found that mPD-L1 expression was robustly elevated after doxycycline-induced knockdown of Prmt1 in these mouse tumor cells (Fig. 6a, Supplementary Fig. 6b–d).