背景:胃癌(GC)中骨髓转移(BMM)被低估。GC合并BMM经常使严重的血液学异常复杂化,如弥散性血管内凝血和微血管病性溶血性贫血。它们构成了高度侵袭性GC(HAGC)亚型。与未指定的晚期GC(NAGC)相比,HAGC的预后很差,具有特殊的临床和病理特征。但是来自GC的BMM的分子机制仍然是初步的。
方法:分析HAGC和NAGC之间的转录组差异。鉴定了在HAGC中特异性上调的基因,研究了它们对细胞迁移和侵袭的影响。通过GC细胞系证实ACTN2基因的功能,骨转移动物模型和患者组织。此外,通过多重免疫荧光染色探索ACTN2衍生-BMM的分子机制,westernblot,染色质免疫沉淀,和荧光素酶报告基因测定。
结果:我们根据HAGC和NAGC之间的转录组差异阐明了BMM的关键机制。评估了在HAGC中特异性上调的五个基因对细胞迁移和侵袭的影响。在小鼠模型中检测到ACTN2基因编码蛋白α-Actinin-2增强了GC细胞的转移能力和诱导的BMM。机械上,α-Actinin-2参与丝状伪足的形成,通过取代α-Actinin-1在GC细胞中形成α-Actinin-2:α-Actinin-4复合物来促进肌动蛋白丝的交联。此外,NF-κB亚基RelA和α-Actinin-2在GC细胞核中形成异源三聚体。作为RelA的直接靶标:α-Actinin-2异源三聚体,ACTN2基因是α-Actinin-2表达的正自动调节环。
结论:我们证明了丝足之间的联系,BMM和ACTN2激活,其中ACTN2和RelA之间的前馈激活环通过肌动蛋白响应于远处转移而建立。鉴于BMM在GC中的新的丝足形成功能和新机制,我们提出ACTN2作为一种可药用的分子脆弱性,可能提供针对GC的BMM的潜在治疗益处.
Bone marrow metastasis (BMM) is underestimated in gastric cancer (GC). GC with BMM frequently complicate critical hematological abnormalities like diffused intravascular coagulation and microangiopathic hemolytic anemia, which constitute a highly aggressive GC (HAGC) subtype. HAGC present a very poor prognosis with peculiar clinical and pathological features when compared with not otherwise specified advanced GC (NAGC). But the molecular mechanisms underlying BMM from GC remain rudimentary.
The transcriptomic difference between HAGC and NAGC were analyzed. Genes that were specifically upregulated in HAGC were identified, and their effect on cell migration and invasion was studied. The function of ACTN2 gene were confirmed by GC cell lines, bone-metastatic animal model and patients\' tissues. Furthermore, the molecular mechanism of ACTN2 derived-BMM was explored by multiple immunofluorescence staining, western blot, chromatin immunoprecipitation, and luciferase reporter assays.
We elucidated the key mechanisms of BMM depending on the transcriptomic difference between HAGC and NAGC. Five genes specifically upregulated in HAGC were assessed their effect on cell migration and invasion. The ACTN2 gene encoding protein α-Actinin-2 was detected enhanced the metastatic capability and induced BMM of GC cells in mouse models. Mechanically, α-Actinin-2 was involved in filopodia formation where it promoted the Actin filament cross-linking by replacing α-Actinin-1 to form α-Actinin-2:α-Actinin-4 complexes in GC cells. Moreover, NF-κB subunit RelA and α-Actinin-2 formed heterotrimers in the nuclei of GC cells. As a direct target of RelA:α-Actinin-2 heterotrimers, the ACTN2 gene was a positive auto-regulatory loop for α-Actinin-2 expression.
We demonstrated a link between filopodia, BMM and ACTN2 activation, where a feedforward activation loop between ACTN2 and RelA is established via actin in response to distant metastasis. Given the novel filopodia formation function and the new mechanism of BMM in GC, we propose ACTN2 as a druggable molecular vulnerability that may provide potential therapeutic benefit against BMM of GC.