Section of Cancer Genomics, Center for Cancer Research, NCI, NIH, Bethesda, Maryland.
NIAID Collaborative Bioinformatics Resource (NCBR), National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland.
Clin Cancer Res. 2020 Jul 1;26(13):3468-3480. doi: 10.1158/1078-0432.CCR-19-1984. Epub 2020 Apr 6.
The standard treatment of patients with locally advanced rectal cancer consists of preoperative chemoradiotherapy (CRT) followed by surgery. However, the response of individual tumors to CRT is extremely diverse, presenting a clinical dilemma. This broad variability in treatment response is likely attributable to intratumor heterogeneity (ITH).
We addressed the impact of ITH on response to CRT by establishing single-cell-derived cell lines (SCDCL) from a treatment-naïve rectal cancer biopsy after xenografting.
Individual SCDCLs derived from the same tumor responded profoundly different to CRT . Clonal reconstruction of the tumor and derived cell lines based on whole-exome sequencing revealed nine separate clusters with distinct proportions in the SCDCLs. Missense mutations in and were clonal in the resistant SCDCL, but not detected in the sensitive SCDCL. Single-cell genetic analysis by multiplex FISH revealed the expansion of a clone with a loss of in the resistant SCDCL. Gene expression profiling by tRNA-sequencing identified the activation of the Wnt, Akt, and Hedgehog signaling pathways in the resistant SCDCLs. Wnt pathway activation in the resistant SCDCLs was confirmed using a reporter assay.
Our model system of patient-derived SCDCLs provides evidence for the critical role of ITH for treatment response in patients with rectal cancer and shows that distinct genetic aberration profiles are associated with treatment response. We identified specific pathways as the molecular basis of treatment response of individual clones, which could be targeted in resistant subclones of a heterogenous tumor.
局部晚期直肠癌患者的标准治疗包括术前放化疗（CRT）后再行手术。然而，个体肿瘤对 CRT 的反应极为多样，这带来了临床困境。这种治疗反应的广泛变异性可能归因于肿瘤内异质性（ITH）。
我们通过建立经异种移植的治疗初治直肠腺癌活检的单细胞衍生细胞系（SCDCL）来研究 ITH 对 CRT 反应的影响。
源自同一肿瘤的单个 SCDCL 对 CRT 的反应明显不同。基于全外显子组测序对肿瘤和衍生细胞系进行克隆重建，揭示了 SCDCL 中存在九个不同的簇，其比例各不相同。耐药 SCDCL 中存在 的错义突变具有克隆性，但在敏感 SCDCL 中未检测到。通过多重荧光原位杂交的单细胞遗传分析，发现耐药 SCDCL 中存在 的缺失克隆扩增。通过 tRNA 测序进行的基因表达谱分析鉴定了耐药 SCDCL 中 Wnt、Akt 和 Hedgehog 信号通路的激活。使用报告基因测定证实了耐药 SCDCL 中 Wnt 通路的激活。
我们的患者衍生 SCDCL 模型系统为直肠癌患者治疗反应中 ITH 的关键作用提供了证据，并表明不同的遗传异常谱与治疗反应相关。我们确定了特定的途径作为个体克隆治疗反应的分子基础，这可能成为异质性肿瘤中耐药亚克隆的靶点。
