Serine/threonine-protein kinase B-raf (BRAF) mutations are found in 8–15% of colorectal cancer patients and identify a subset of tumors with poor outcome in the metastatic setting. We have previously reported that BRAF-mutant human cells display a high rate of protein production, causing proteotoxic stress, and are selectively sensitive to the proteasome inhibitors bortezomib and carfilzomib. In this work, we tested whether carfilzomib could restrain the growth of BRAF-mutant colorectal tumors not only by targeting cancer cells directly, but also by promoting an immune-mediated antitumor response. In human and mouse colorectal cancer cells, carfilzomib triggered robust endoplasmic reticulum stress and autophagy, followed by the emission of immunogenic-damage-associated molecules. Intravenous administration of carfilzomib delayed the growth of BRAF-mutant murine tumors and mobilized the danger-signal proteins calreticulin and high mobility group box 1 (HMGB1). Analyses of drug-treated samples revealed increased intratumor recruitment of activated cytotoxic T cells and natural killers, concomitant with the downregulation of forkhead box protein P3 (Foxp3)⁺ T-cell surface glycoprotein CD4 (CD4)⁺ T cells, indicating that carfilzomib promotes reshaping of the immune microenvironment of BRAF-mutant murine colorectal tumors. These results will inform the design of clinical trials in BRAF-mutant colorectal cancer patients.

中文翻译：

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卡非佐米在 BRAF 突变结直肠癌模型中的临床前疗效

丝氨酸/苏氨酸蛋白激酶 B-raf ( BRAF ) 突变存在于 8-15% 的结直肠癌患者中，并确定了转移情况下预后不良的肿瘤子集。我们之前报道过，BRAF突变的人类细胞表现出高蛋白生成率，引起蛋白毒性应激，并且对蛋白酶体抑制剂硼替佐米和卡非佐米选择性敏感。在这项工作中，我们测试了卡非佐米是否可以通过直接靶向癌细胞以及促进免疫介导的抗肿瘤反应来抑制BRAF突变结直肠肿瘤的生长。在人和小鼠结直肠癌细胞中，卡非佐米引发强大的内质网应激和自噬，随后释放免疫原性损伤相关分子。静脉注射卡非佐米可延缓BRAF突变小鼠肿瘤的生长，并动员危险信号蛋白钙网蛋白和高迁移率族蛋白 1 (HMGB1)。对药物处理样本的分析显示，肿瘤内激活的细胞毒性 T 细胞和自然杀伤细胞的募集增加，同时叉头盒蛋白 P3 (Foxp3) ⁺ T 细胞表面糖蛋白 CD4 (CD4) ⁺ T 细胞的下调，表明卡非佐米促进重塑BRAF突变小鼠结直肠肿瘤的免疫微环境。这些结果将为BRAF突变结直肠癌患者的临床试验设计提供信息。