Department of Surgery and Cancer, Ovarian Cancer Action Research Centre, Imperial College London, London, UK.
Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore.
EMBO Rep. 2018 Aug;19(8). doi: 10.15252/embr.201745670. Epub 2018 Jun 15.
In ovarian cancer, the prometastatic RTK AXL promotes motility, invasion and poor prognosis. Here, we show that reduced survival caused by AXL overexpression can be mitigated by the expression of the GPI-anchored tumour suppressor OPCML Further, we demonstrate that AXL directly interacts with OPCML, preferentially so when AXL is activated by its ligand Gas6. As a consequence, AXL accumulates in cholesterol-rich lipid domains, where OPCML resides. Here, phospho-AXL is brought in proximity to the lipid domain-restricted phosphatase PTPRG, which de-phosphorylates the RTK/ligand complex. This prevents AXL-mediated transactivation of other RTKs (cMET and EGFR), thereby inhibiting sustained phospho-ERK signalling, induction of the EMT transcription factor Slug, cell migration and invasion. From a translational perspective, we show that OPCML enhances the effect of the phase II AXL inhibitor R428 and We therefore identify a novel mechanism by which two spatially restricted tumour suppressors, OPCML and PTPRG, coordinate to repress AXL-dependent oncogenic signalling.
在卵巢癌中,促转移的 RTK AXL 促进了迁移、侵袭和预后不良。在这里,我们发现 AXL 过表达导致的存活率降低可以通过表达糖基磷脂酰肌醇锚定的肿瘤抑制因子 OPCML 得到缓解。此外,我们证明 AXL 可以直接与 OPCML 相互作用,当 AXL 被其配体 Gas6 激活时,这种相互作用更为明显。因此,AXL 在富含胆固醇的脂质区域聚集,OPCML 就位于这个区域。在这里,磷酸化的 AXL 被带到与脂质区域受限的磷酸酶 PTPRG 接近的位置,后者使 RTK/配体复合物去磷酸化。这阻止了 AXL 介导的其他 RTK(cMET 和 EGFR)的反式激活,从而抑制了持续的磷酸化 ERK 信号转导、EMT 转录因子 Slug 的诱导、细胞迁移和侵袭。从转化医学的角度来看,我们表明 OPCML 增强了 II 期 AXL 抑制剂 R428 的效果。因此,我们确定了一种新的机制,即两个空间受限的肿瘤抑制因子 OPCML 和 PTPRG 协调抑制 AXL 依赖性致癌信号。