PDF(Pubmed)
Abstract：
Vemurafenib (PLX4032), small-molecule inhibitor of mutated BRAFV600E protein, has emerged as a potent anti-cancer agent against metastatic melanoma harboring BRAFV600E mutation. Unfortunately, the effect of PLX4032 in the treatment of metastatic BRAF mutated colorectal cancer (CRC) is less potent due to high incidence of fast-developing chemoresistance. It has been demonstrated that sphingolipids are important mediators of chemoresistance to various therapies in colon cancer. In this study, we will explore the role of major regulators of sphingolipid metabolism and signaling in the development of resistance to vemurafenib in BRAF mutant colon cancer cells. The obtained data revealed significantly increased expression levels of activated sphingosine kinases (SphK1 and SphK2) in resistant cells concomitant with increased abundance of sphingosine-1-phosphate (S1P) and its precursor sphingosine, which was accompanied by increased expression levels of the enzymes regulating the ceramide salvage pathway, namely ceramide synthases 2 and 6 and acid ceramidase, especially after the exposure to vemurafenib. Pharmacological inhibition of SphK1/SphK2 activities or modulation of ceramide metabolism by exogenous C6-ceramide enhanced the anti-proliferative effect of PLX4032 in resistant RKO cells in a synergistic manner. It is important to note that the inhibition of SphK2 by ABC294640 proved effective at restoring the sensitivity of resistant cells to vemurafenib at the largest number of combinations of sub-toxic drug concentrations with minimal cytotoxicity. Furthermore, the obtained findings revealed that enhanced anti-proliferative, anti-migratory, anti-clonogenic and pro-apoptotic effects of a combination treatment with ABC294640 and PLX4032 relative to either drug alone were accompanied by the inhibition of S1P-regulated AKT activity and concomitant abrogation of AKT-mediated cellular levels of nucleophosmin and translationally-controlled tumour protein. Collectively, our study suggests the possibility of using the combination of ABC294640 and PLX4032 as a novel therapeutic approach to combat vemurafenib resistance in BRAF mutant colon cancer, which warrants additional preclinical validation studies.
摘要：
Vemurafenib(PLX4032),突变的BRAFV600E蛋白的小分子抑制剂，已成为一种有效的抗癌剂，可对抗携带BRAFV600E突变的转移性黑色素瘤。不幸的是,PLX4032治疗转移性BRAF突变结直肠癌(CRC)的效果较差,原因是快速发展的化疗耐药发生率较高.已经证明鞘脂是结肠癌中对各种疗法的化学抗性的重要介质。在这项研究中,我们将探讨鞘脂代谢和信号传导的主要调节因子在BRAF突变结肠癌细胞对vemurafenib耐药性发展中的作用。获得的数据显示，抗性细胞中激活的鞘氨醇激酶（SphK1和SphK2）的表达水平显着增加，同时鞘氨醇-1-磷酸（S1P）及其前体鞘氨醇的丰度增加，伴随着调节神经酰胺补救途径的酶的表达水平增加，即神经酰胺合酶2和6和酸性神经酰胺酶，尤其是在接触vemurafenib之后.通过外源性C6-神经酰胺对SphK1/SphK2活性的药理学抑制或对神经酰胺代谢的调节以协同方式增强PLX4032在抗性RKO细胞中的抗增殖作用。重要的是要注意ABC294640对SphK2的抑制被证明在具有最小细胞毒性的亚毒性药物浓度的最大数量的组合下有效地恢复抗性细胞对维罗非尼的敏感性。此外，获得的研究结果表明，增强抗增殖，反迁徙,ABC294640和PLX4032联合治疗的抗克隆作用和促凋亡作用,相对于单独使用任一种药物,伴随着S1P调节的AKT活性的抑制和AKT介导的核磷蛋白和翻译控制的肿瘤蛋白的细胞水平的废除.总的来说，我们的研究表明，使用ABC294640和PLX4032的组合作为一种新的治疗方法来对抗Vemurafenib在BRAF突变结肠癌中的耐药性的可能性，这需要额外的临床前验证研究。
