Lgr5-negative cancer cells seed metastases in colorectal cancer

Cancer stem cells (CSCs) are a minority population of cancer cells that display stem cell-like multipotent and self-renewal properties. They give rise to the bulk of cancer cells with limited replicative potential. In colorectal cancer (CRC), CSCs are marked by expression of the leucine-rich repeat-containing G-protein receptor 5 (Lgr5). Since CSCs display multipotent and self-renewal properties, this population is thought to seed metastases. Here, we used a mouse model and human xenografts to investigate the cell-of-origin of metastases. Surprisingly, we found that most CRC cells that disseminated and entered the blood circulation were Lgr5-. Lgr5- cancer cells arriving at the metastatic site formed lesions in which Lgr5+ CSCs appeared. This plasticity could occur independently of stemness-inducing factors, and was an indispensable event for the outgrowth of metastases, since neutralization of this plasticity prevented metastatic outgrowth. Combined, our study shows that most metastases are seeded by Lgr5- cancer cells, and that these cells have a niche-independent and intrinsic capacity to become CSCs and restore epithelial hierarchy. Overall design: Single-cell mRNA sequencing of genetically engineered colorectal tumor organoids and mouse derived tumors.

癌症干细胞（Cancer stem cells, CSCs）是占癌细胞群体极少数的亚群，具备干细胞样多能性与自我更新特性，可分化产生绝大多数复制潜能有限的癌细胞。在结直肠癌（colorectal cancer, CRC）中，CSCs以富含亮氨酸重复序列G蛋白偶联受体5（leucine-rich repeat-containing G-protein receptor 5, Lgr5）的表达为特征标志物。鉴于CSCs具有多能性与自我更新能力，该细胞群被认为是转移灶的起始来源。本研究借助小鼠模型与人类异种移植瘤，探究了转移灶的起源细胞。令人意外的是，我们发现绝大多数播散并进入血液循环的结直肠癌细胞为Lgr5阴性（Lgr5-）。抵达转移部位的Lgr5阴性癌细胞所形成的病灶内，可出现Lgr5阳性（Lgr5+）的CSCs。这种细胞可塑性可不依赖于干性诱导因子发生，且是转移灶增殖形成的必要事件——阻断该可塑性可抑制转移灶的生长。综合来看，本研究证实绝大多数转移灶由Lgr5阴性癌细胞起始，且这类细胞具备不依赖于微环境的内在能力，可转化为CSCs并重建上皮细胞层级结构。
实验整体设计：对基因工程结直肠癌肿瘤类器官及小鼠来源肿瘤开展单细胞mRNA测序。