Hengst Jeremy A, Nduwumwami Asvelt J, Yun Jong K
Department of Pharmacology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, 6565 MD Anderson Blvd, Houston, TX 77030, USA.
Cancers (Basel). 2022 Oct 22;14(21):5182. doi: 10.3390/cancers14215182.
We recently identified the sphingosine kinases (SphK1/2) as key intracellular regulators of immunogenic cell death (ICD) in colorectal cancer (CRC) cells. To better understand the mechanism by which SphK inhibition enhances ICD, we focused on the intracellular signaling pathways leading to cell surface exposure of calreticulin (ectoCRT). Herein, we demonstrate that ABT-263 and AZD-5991, inhibitors of Bcl-2/Bcl-X and Mcl-1, respectively, induce the production of ectoCRT, indicative of ICD. Inhibition of SphK1 significantly enhanced ABT/AZD-induced ectoCRT production, in a caspase 8-dependent manner. Mechanistically, we demonstrate that ABT/AZD-induced Bak/Bax activation stimulates pro-survival SphK1/sphingosine-1-phosphate (S1P) signaling, which attenuates ectoCRT production. Additionally, we identified a regulatory role for ceramide synthase 6 (CerS6)/C16:0 ceramide in transporting of ectoCRT to the cell surface. Together, these results indicate that the sphingolipid metabolic regulators of the sphingolipid rheostat, S1P and C16:0 ceramide, influence survival/death decisions of CRC cells in response to ICD-inducing chemotherapeutic agents. Importantly, SphK1, which produces S1P, is a stress-responsive pro-survival lipid kinase that suppresses ICD. While ceramide, produced by the inhibition of SphK1 is required for production of the cell surface marker of ICD, ectoCRT. Thus, inhibition of SphK1 represents a means to enhance the therapeutic efficacy of ICD-inducing agents.
我们最近确定鞘氨醇激酶（SphK1/2）是结肠直肠癌（CRC）细胞中免疫原性细胞死亡（ICD）的关键细胞内调节因子。为了更好地理解SphK抑制增强ICD的机制，我们聚焦于导致钙网蛋白（ectoCRT）细胞表面暴露的细胞内信号通路。在此，我们证明分别作为Bcl-2/Bcl-X和Mcl-1抑制剂的ABT-263和AZD-5991可诱导ectoCRT产生，这是ICD的指征。SphK1的抑制以半胱天冬酶8依赖性方式显著增强ABT/AZD诱导的ectoCRT产生。从机制上讲，我们证明ABT/AZD诱导的Bak/Bax激活刺激了促生存的SphK1/鞘氨醇-1-磷酸（S1P）信号传导，这减弱了ectoCRT的产生。此外，我们确定了神经酰胺合酶-6（CerS6）/C16:0神经酰胺在将ectoCRT转运至细胞表面中的调节作用。总之，这些结果表明鞘脂变阻器的鞘脂代谢调节因子S1P和C16:0神经酰胺会影响CRC细胞对诱导ICD的化疗药物的生存/死亡决定。重要的是，产生S1P的SphK1是一种应激反应性促生存脂质激酶，可抑制ICD。而抑制SphK1产生的神经酰胺是ICD的细胞表面标志物ectoCRT产生所必需的。因此，抑制SphK1是增强诱导ICD药物治疗效果的一种手段。
