Enhancing PD-L1 Degradation by ITCH during MAPK Inhibitor Therapy Suppresses Acquired Resistance. Enhancing PD-L1 Degradation by ITCH during MAPK Inhibitor Therapy Suppresses Acquired Resistance

MAPK inhibitor (MAPKi) therapy in melanoma leads to accumulation of tumor-surface PD-L1/2, which may evade antitumor immunity and accelerate acquired resistance. Here, we discover that the E3 ligase ITCH binds, ubiquitinates, and down-regulates tumor-surface PD-L1/L2 in MAPKi-treated human melanoma cells, thereby modulating activation of co-cultured T cells. During MAPKi therapy in vivo, tumor cell-intrinsic ITCH knockdown in murine melanoma induced tumor-surface PD-L1, reduced intratumoral cytolytic CD8+ T cells, and accelerated acquired resistance only in immune-proficient mice. Conversely, tumor cell-intrinsic ITCH over-expression reduced MAPKi-elicited PD-L1 accumulation, augmented cytolytic CD8+ T-cell infiltration, and suppressed acquired resistance in BrafMUT, NrasMUT, and Nf1MUT murine melanoma and KrasMUT pancreatic cancer models. CD8+ T-cell depletion and tumor cell-intrinsic PD-L1 over-expression nullified the ability of ITCH over-expression to suppress MAPKi-resistance, supporting in vivo the ITCH­–PD-L1­–T-cell regulatory axis demonstrated in human cancer cell lines. Moreover, we identified a small-molecular ITCH activator which suppressed acquired MAPKi-resistance in vivo. Thus, MAPKi-elicited tumor-surface PD-L1 accelerates acquired-resistance, and degrading PD-L1 by activating ITCH may be a combinatorial approach to promote antitumor T-cell immunity and durable responses. Overall design: This dataset contains the scRNAseq and scTCR-seq data of intratumoral CD45+ cells in murine melanoma model (NILER1-4, Nras mutant) under MEKi treatment and scRNAseq data of dissociated tumors in BRAFmut murine melanoma model (YUMMER1.7) under MEKi treatment

丝裂原活化蛋白激酶抑制剂（MAPK inhibitor，缩写MAPKi）治疗黑色素瘤时，可诱导肿瘤表面程序性死亡受体配体1/2（PD-L1/2）积累，进而介导肿瘤免疫逃逸并加速获得性耐药。本研究发现，E3泛素连接酶（E3 ligase）ITCH可结合经MAPKi处理的人黑色素瘤细胞表面的PD-L1/L2，对其进行泛素化修饰并下调其表达水平，从而调节共培养T细胞的活化状态。在体内MAPKi治疗过程中，小鼠黑色素瘤细胞内源性ITCH敲低会诱导肿瘤表面PD-L1表达，减少瘤内溶细胞性CD8+ T细胞浸润，且仅在免疫功能完整的小鼠中加速获得性耐药。与之相反，肿瘤细胞内源性ITCH过表达可减少MAPKi诱导的PD-L1积累，增加溶细胞性CD8+ T细胞浸润，并在BRAF突变型（BrafMUT）、NRAS突变型（NrasMUT）及NF1突变型（Nf1MUT）小鼠黑色素瘤和KRAS突变型（KrasMUT）胰腺癌模型中抑制获得性耐药。CD8+ T细胞耗竭及肿瘤细胞内源性PD-L1过表达会抵消ITCH过表达抑制MAPKi耐药的能力，这在体内验证了人类癌细胞系中证实的ITCH-PD-L1-T细胞调控轴。此外，本研究还发现一种小分子ITCH激活剂，可在体内抑制MAPKi获得性耐药。综上，MAPKi诱导的肿瘤表面PD-L1可加速获得性耐药，而通过激活ITCH降解PD-L1或许可作为一种联合治疗策略，以增强抗肿瘤T细胞免疫应答并实现持久临床应答。总体实验设计：本数据集包含经丝裂原活化蛋白激酶/细胞外调节蛋白激酶抑制剂（MEK inhibitor，缩写MEKi）治疗的NRAS突变型小鼠黑色素瘤模型（NILER1-4）中瘤内CD45+细胞的单细胞RNA测序（scRNAseq）与单细胞T细胞受体测序（scTCR-seq）数据，以及经MEKi治疗的BRAF突变型小鼠黑色素瘤模型（YUMMER1.7）中解离肿瘤组织的单细胞RNA测序数据。