Purpose

CFTR mutations not only cause cystic fibrosis, but also increase the risk of colorectal cancer. A putative role of CFTR in colorectal cancer patients without cystic fibrosis has so far, however, not been investigated. RAC3 is a nuclear receptor coactivator that has been found to be overexpressed in several human tumors, and to be required for maintaining cancer stemness. Here, we investigated the functional relationship between CFTR and RAC3 for maintaining cancer stemness in human colorectal cancer.

Methods

Cancer stemness was investigated by analysing the expression of stem cell markers, clonogenic growth and selective retention of fluorochrome, using stable transfection of shCFTR or shRAC3 in HCT116 colorectal cancer cells. In addition, we performed pathway enrichment and network analyses in both primary human colorectal cancer samples (TCGA, Xena platform) and Caco-2 colorectal cancer cells including (1) CD133+ or CD133- side populations and (2) CFTRwt or CFTRmut cells (ConsensusPathDB, STRING, Cytoscape, GeneMANIA).

Results

We found that the CD133+ side population expresses higher levels of RAC3 and CFTR than the CD133- side population. RAC3 overexpression increased CFTR expression, whereas CFTR downregulation inhibited the cancer stem phenotype. CFTR mRNA levels were found to be increased in colorectal cancer samples from patients without cystic fibrosis compared to those with CFTR mutations, and this correlated with an increased expression of RAC3. The expression pattern of a gene set involved in inflammatory response and nuclear receptor modulation in CD133+ Caco-2 cells was found to be shared with that in CFTRwt Caco-2 cells. These genes may contribute to colorectal cancer development.

Conclusions

CFTR may play a non-tumor suppressor role in colorectal cancer development and maintenance involving enhancement of the expression of a set of genes related to cancer stemness and development in patients without CFTR mutations.

中文翻译：

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CFTR与RAC3表达维持人结直肠癌癌细胞干性的功能关系

目的

CFTR突变不仅会导致囊性纤维化，还会增加患结直肠癌的风险。然而，到目前为止，CFTR 在没有囊性纤维化的结直肠癌患者中的假定作用尚未得到研究。RAC3 是一种核受体共激活剂，已被发现在几种人类肿瘤中过度表达，并且是维持癌症干性所必需的。在这里，我们研究了 CFTR 和 RAC3 之间在维持人类结直肠癌癌症干性方面的功能关系。

方法

通过在 HCT116 结肠直肠癌细胞中稳定转染 shCFTR 或 shRAC3，通过分析干细胞标志物的表达、克隆生长和荧光染料的选择性保留来研究癌症干性。此外，我们对原代人类结直肠癌样本（TCGA、Xena 平台）和 Caco-2 结直肠癌细胞进行了通路富集和网络分析，包括（1）CD133+ 或 CD133- 侧群和（2）CFTRwt 或 CFTRmut 细胞（ConsensusPathDB , STRING, Cytoscape, GeneMANIA)。

结果

我们发现 CD133+ 侧群比 CD133-侧群表达更高水平的 RAC3 和 CFTR。RAC3 过表达增加了 CFTR 表达，而 CFTR 下调抑制了癌症干表型。与具有 CFTR 突变的患者相比，未出现囊性纤维化的患者的结直肠癌样本中 CFTR mRNA 水平增加，这与 RAC3 的表达增加有关。发现 CD133+ Caco-2 细胞中涉及炎症反应和核受体调节的基因组的表达模式与 CFTRwt Caco-2 细胞中的表达模式相同。这些基因可能有助于结直肠癌的发展。

结论

CFTR 可能在结直肠癌的发展和维持中发挥非肿瘤抑制作用，包括在没有 CFTR 突变的患者中增强与癌症干性和发展相关的一组基因的表达。