Coexpression of Normally Incompatible Developmental Pathways in Retinoblastoma Genesis [single tumor cell data]. Homo sapiens

It is widely believed that the molecular and cellular features of a tumor reflect its cell-of-origin and can thus provide clues about treatment targets. The retinoblastoma cell-of-origin has been debated for over a century. Here we report that human and mouse retinoblastomas have molecular, cellular, and neurochemical features of multiple cell classes, principally amacrine/horizontal interneurons, retinal progenitor cells, and photoreceptors. Importantly, single-cell gene expression array analysis showed that these multiple cell type–specific developmental programs are coexpressed in individual retinoblastoma cells, which creates a progenitor/neuronal hybrid cell. Importantly, neurotransmitter receptors, transporters, and biosynthetic enzymes are expressed in human retinoblastoma, and targeted disruption of these pathways reduces retinoblastoma growth in vivo and in vitro. Our finding that retinoblastoma tumor cells express multiple neuronal differentiation programs that are normally incompatible in development suggests that the pathways that control retinal development and establish distinct cell types are perturbed during tumorigenesis. Therefore, the cell-of-origin for retinoblastoma cannot be inferred from the features of the tumor cells themselves. However, we now have a detailed understanding of the neuronal pathways that are deregulated in retinoblastoma and targeting the catecholamine and indolamine receptors or downstream components could provide useful therapeutic approaches in future studies. This example highlights the importance of comprehensive molecular, cellular and physiological characterization of human cancers with single cell resolution as we incorporate molecular targeted therapy into treatment regimens. Overall design: 20 single cells isolated from primary pediatric retinoblastoma tumors were assayed to asses the within tumor consistency of expression signals

学界普遍认为，肿瘤的分子与细胞特征可反映其起源细胞（cell-of-origin），并可为治疗靶点的发掘提供线索。视网膜母细胞瘤的起源细胞这一议题已争论逾百年。
本研究发现，人类与小鼠的视网膜母细胞瘤均具备多种细胞类别的分子、细胞及神经化学特征，主要涵盖无长突/水平中间神经元（amacrine/horizontal interneurons）、视网膜祖细胞（retinal progenitor cells）以及感光细胞（photoreceptors）。尤为关键的是，单细胞基因表达芯片分析显示，这些多种细胞类型特异性的发育程序在单个视网膜母细胞瘤细胞中共表达，进而形成祖细胞-神经元杂交细胞。
值得注意的是，人类视网膜母细胞瘤可表达神经递质受体、转运蛋白及生物合成酶，靶向阻断这些通路可在体内与体外环境中抑制肿瘤生长。
我们的研究结果表明，视网膜母细胞瘤肿瘤细胞可表达多种在正常发育过程中相互排斥的神经元分化程序，这提示调控视网膜发育、并确立不同细胞类别的信号通路在肿瘤发生过程中发生了紊乱。因此，无法通过肿瘤细胞自身的特征推断视网膜母细胞瘤的起源细胞。
不过，我们现已对视网膜母细胞瘤中失调的神经元通路形成了详尽的认知，靶向儿茶酚胺与吲哚胺受体或其下游组分，有望在未来研究中成为有效的治疗策略。
该案例凸显了在将分子靶向疗法纳入临床治疗方案的当下，以单细胞分辨率对人类癌症开展全面的分子、细胞及生理学特征表征的重要性。
实验整体设计：本研究对从原发性儿童视网膜母细胞瘤组织中分离得到的20个单细胞进行了检测，以评估肿瘤内部表达信号的一致性。