Laboratory of Molecular Oncology, Centre for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad, 500001, India.
Graduate Studies, Manipal University, Manipal, Karnataka, India.
J Mol Med (Berl). 2018 Feb;96(2):135-146. doi: 10.1007/s00109-017-1607-4. Epub 2017 Nov 9.
Our previous extensive analysis revealed a significant proportion of early-onset colorectal tumors from India to be localized to the rectum in younger individuals and devoid of deregulated Wnt/β-catenin signaling. In the current study, we performed a comprehensive genome-wide analysis of clinically well-annotated microsatellite stable early-onset sporadic rectal cancer (EOSRC) samples. Results revealed extensive DNA copy number alterations in rectal tumors in the absence of deregulated Wnt/β-catenin signaling. More importantly, transcriptome profiling revealed a (non-Wnt/β-catenin, non-MSI) genetic signature that could efficiently and specifically identify Wnt- rectal cancer. The genetic signature included a significant representation of genes belonging to Ca/NFAT signaling pathways that were validated in additional samples. The validated NFAT target genes exhibited significantly higher expression levels than canonical Wnt/β-catenin targets in Wnt- samples, an observation confirmed in other CRC expression data sets as well. We confirmed the validated genes to be transcriptionally regulated by NFATc1 by (a) evaluating their respective transcript levels and (b) performing promoter-luciferase and chromatin immunoprecipitation assays following ectopic expression as well as knockdown of NFATc1 in CRC cells. NFATc1 and its targets RUNX2 and GSN could drive increased migration in CRC cells. Finally, the validated genes were associated with poor survival in the cancer genome atlas CRC expression data set. This study is the first comprehensive molecular characterization of EOSRC that appears to be driven by noncanonical tumorigenesis pathways.
Early-onset sporadic rectal cancer exhibits DNA gain and loss without Wnt activation. Ca/NFAT signaling appears to be activated in the absence of Wnt activation. An eight-gene genetic signature distinguishes Wnt+ and Wnt- rectal tumors. NFAT and its target genes regulate tumorigenic properties in CRC cells.
我们之前的广泛分析显示，来自印度的大量早期结直肠癌肿瘤在年轻个体中定位于直肠，并且没有受到 Wnt/β-连环蛋白信号的调节。在当前的研究中，我们对经过临床充分注释的微卫星稳定的早期散发直肠肿瘤（EOSRC）样本进行了全面的全基因组分析。结果表明，在不存在 Wnt/β-连环蛋白信号失调的情况下，直肠肿瘤存在广泛的 DNA 拷贝数改变。更重要的是，转录组谱分析揭示了一种（非 Wnt/β-连环蛋白、非 MSI）遗传特征，可以有效地、特异性地识别 Wnt-直肠肿瘤。该遗传特征包括属于 Ca/NFAT 信号通路的基因的显著代表性，这些基因在其他样本中得到了验证。验证的 NFAT 靶基因在 Wnt-样本中的表达水平明显高于经典 Wnt/β-连环蛋白靶基因，这一观察结果在其他 CRC 表达数据集也得到了证实。我们通过（a）评估各自的转录水平和（b）在 CRC 细胞中外源性表达和 NFATc1 敲低后进行启动子荧光素酶和染色质免疫沉淀测定，证实了验证的基因受 NFATc1 的转录调控。NFATc1 及其靶基因 RUNX2 和 GSN 可以驱动 CRC 细胞的迁移增加。最后，验证的基因与癌症基因组图谱 CRC 表达数据集中的不良生存相关。这项研究是对 EOSRC 的首次全面分子特征描述，它似乎是由非典型肿瘤发生途径驱动的。
早期散发的直肠肿瘤表现出 DNA 获得和丢失，而没有 Wnt 激活。Ca/NFAT 信号似乎在没有 Wnt 激活的情况下被激活。一个由八个基因组成的遗传特征可区分 Wnt+和 Wnt-直肠肿瘤。NFAT 和其靶基因调节 CRC 细胞中的肿瘤发生特性。
