Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
Portage Glasgow Limited, Glasgow, UK.
BMC Cancer. 2019 Mar 25;19(1):266. doi: 10.1186/s12885-019-5489-4.
Recent advances in the treatment of melanoma that involve immunotherapy and B-Raf inhibition have revolutionised cancer care for this disease. However, an un-met clinical need remains in B-Raf inhibitor resistant patients where first-generation B-Raf inhibitors provide only short-term disease control. In these cases, B-Raf inhibition leads to paradoxical activation of the C-Raf - MEK - ERK signalling pathway, followed by metastasis. PDE8A has been shown to directly interact with and modulate the cAMP microdomain in the vicinity of C-Raf. This interaction promotes C-Raf activation by attenuating the PKA-mediated inhibitory phosphorylation of the kinase.
We have used a novel cell-penetrating peptide agent (PPL-008) that inhibits the PDE8A - C-Raf complex in a human malignant MM415 melanoma cell line and MM415 melanoma xenograft mouse model to investigate ERK MAP kinase signalling.
We have demonstrated that the PDE8A - C-Raf complex disruptor PPL-008 increased inhibitory C-Raf-S259 phosphorylation and significantly reduced phospho-ERK signalling. We have also discovered that the ability of PPL-008 to dampen ERK signalling can be used to counter B-Raf inhibitor-driven paradoxical activation of phospho-ERK in MM415 cells treated with PLX4032 (Vemurafenib). PPL-008 treatment also significantly retarded the growth of these cells. When applied to a MM415 melanoma xenograft mouse model, PPL-008C penetrated tumour tissue and significantly reduced phospho-ERK signalling in that domain.
Our data suggests that the PDE8A-C-Raf complex is a promising therapeutic treatment for B-Raf inhibitor resistant melanoma.
涉及免疫疗法和 B-Raf 抑制的黑色素瘤治疗的最新进展彻底改变了这种疾病的癌症治疗方法。然而，在 B-Raf 抑制剂耐药患者中仍存在未满足的临床需求，第一代 B-Raf 抑制剂仅提供短期疾病控制。在这些情况下，B-Raf 抑制导致 C-Raf-MEK-ERK 信号通路的反常激活，随后发生转移。已经表明 PDE8A 与 C-Raf 附近的 cAMP 微区直接相互作用并调节该微区。这种相互作用通过减轻激酶的 PKA 介导的抑制性磷酸化来促进 C-Raf 的激活。
我们使用了一种新型的穿透肽剂（PPL-008），该肽剂在人恶性 MM415 黑色素瘤细胞系和 MM415 黑色素瘤异种移植小鼠模型中抑制 PDE8A-C-Raf 复合物，以研究 ERK MAP 激酶信号。
我们已经证明，PDE8A-C-Raf 复合物破坏剂 PPL-008 增加了抑制性 C-Raf-S259 磷酸化，并显著降低了磷酸化-ERK 信号。我们还发现，PPL-008 减弱 ERK 信号的能力可用于对抗 PLX4032（vemurafenib）处理的 MM415 细胞中 B-Raf 抑制剂驱动的磷酸化-ERK 的反常激活。PPL-008 处理还显著延缓了这些细胞的生长。当应用于 MM415 黑色素瘤异种移植小鼠模型时，PPL-008C 穿透肿瘤组织并显著降低该区域的磷酸化-ERK 信号。
我们的数据表明，PDE8A-C-Raf 复合物是一种有前途的治疗 B-Raf 抑制剂耐药性黑色素瘤的治疗方法。
