对于骨肉瘤患者来说，疾病相关的死亡往往源于肺转移，这是许多实体瘤所共有的现象。虽然已建立的转移病灶行为具有侵袭性，但到达肺部的肿瘤细胞中只有很少数能够存活。通过识别促进转移肿瘤细胞存活的机制，我们可以开发预防和治疗转移的治疗策略。本研究通过分析小鼠肺部转移病灶的单细胞RNA测序（scRNAseq）数据，探究在定居过程中宿主细胞和肿瘤细胞的变化。我们利用这些数据阐明了在经过传播后仍能存活的细胞中活跃的信号通路，并确定了促进其活化的候选宿主衍生信号。我们通过活体细胞报告系统、免疫细胞化学以及荧光免疫组织化学验证了这些发现。然后我们利用药理学抑制验证了关键候选因子的功能相关性，使用转移性骨肉瘤模型验证了这一点。表达模式表明，在早期和已建立的转移病灶中，MAPK通路显著升高。MAPK活性与抗凋亡基因的表达，尤其是MCL1的表达相关。生态位细胞产生促进ERK磷酸化和MCL1在肿瘤细胞中的表达的生长因子。早期和已建立的转移病灶都对MCL1抑制敏感，但对MEK抑制不敏感。在小鼠骨肉瘤模型中，联合MCL1抑制和化疗可以预防定居和消除已建立的转移病灶。生态位产生的生长因子推动了骨肉瘤MAPK活性和MCL1表达，促进转移定植。尽管后期转移病灶产生的MCL1较少，但它们仍然依赖它。MCL1是人类和犬科患者临床试验中的一个有前景的靶点。© 2023.作者。

For patients with osteosarcoma, disease-related mortality most often results from lung metastasis-a phenomenon shared with many solid tumors. While established metastatic lesions behave aggressively, very few of the tumor cells that reach the lung will survive. By identifying mechanisms that facilitate survival of disseminated tumor cells, we can develop therapeutic strategies that prevent and treat metastasis.We analyzed single cell RNA-sequencing (scRNAseq) data from murine metastasis-bearing lungs to interrogate changes in both host and tumor cells during colonization. We used these data to elucidate pathways that become activated in cells that survive dissemination and identify candidate host-derived signals that drive activation. We validated these findings through live cell reporter systems, immunocytochemistry, and fluorescent immunohistochemistry. We then validated the functional relevance of key candidates using pharmacologic inhibition in models of metastatic osteosarcoma.Expression patterns suggest that the MAPK pathway is significantly elevated in early and established metastases. MAPK activity correlates with expression of anti-apoptotic genes, especially MCL1. Niche cells produce growth factors that increase ERK phosphorylation and MCL1 expression in tumor cells. Both early and established metastases are vulnerable to MCL1 inhibition, but not MEK inhibition in vivo. Combining MCL1 inhibition with chemotherapy both prevented colonization and eliminated established metastases in murine models of osteosarcoma.Niche-derived growth factors drive MAPK activity and MCL1 expression in osteosarcoma, promoting metastatic colonization. Although later metastases produce less MCL1, they remain dependent on it. MCL1 is a promising target for clinical trials in both human and canine patients.© 2023. The Author(s).