Capicua suppresses colorectal cancer progression via repression of ETV4 expression

Abstract

Background: Although major driver gene mutations have been identified, the complex molecular heterogeneity of colorectal cancer (CRC) remains unclear. Capicua (CIC) functions as a tumor suppressor in various types of cancers; however, its role in CRC progression has not been examined. Methods: Databases for gene expression profile in CRC patient samples were used to evaluate the association of the levels of CIC and Polyoma enhancer activator 3 (PEA3) group genes (ETS translocation variant 1 (ETV1), ETV4, and ETV5), the best-characterized CIC targets in terms of CIC functions, with clinicopathological features of CRC. CIC and ETV4 protein levels were also examined in CRC patient tissue samples. Gain-and loss-of function experiments in cell lines and mouse xenograft models were performed to investigate regulatory functions of CIC and ETV4 in CRC cell growth and invasion. qRT-PCR and western blot analyses were performed to verify the CIC regulation of ETV4 expression in CRC cells. Rescue experiments were conducted using siRNA against ETV4 and CIC-deficient CRC cell lines. Results: CIC expression was decreased in the tissue samples of CRC patients. Cell invasion, migration, and proliferation were enhanced in CIC-deficient CRC cells and suppressed in CIC-overexpressing cells. Among PEA3 group genes, ETV4 levels were most dramatically upregulated and inversely correlated with the CIC levels in CRC patient samples. Furthermore, derepression of ETV4 was more prominent in CIC-deficient CRC cells, when compared with that observed for ETV1 and ETV5. The enhanced cell proliferative and invasive capabilities in CIC-deficient CRC cells were completely recovered by knockdown of ETV4. Conclusion: Collectively, the CIC-ETV4 axis is not only a key module that controls CRC progression but also a novel therapeutic and/or diagnostic target for CRC.

Capicua is a fast-acting transcriptional brake

“…1,[9][10][11] In the absence of RTK signals, Cic represses target genes, many of which are known oncogenes involved in cell proliferation. 12 Exposing cells to ligands that bind RTKs activates the extracellular signal-regulated kinase (ERK) cascade, which counteracts Cic repression, analogous to releasing the brake pedal of a car, to induce target gene transcription. 5,13 The current quantitative models for Cic-dependent gene control rely on studies of the initial pulse of RTK activation in the Drosophila blastoderm, during 13 synchronous nuclear divisions spanning the first 2 h post-fertilization (hpf).…”

Regulation and function of capicua in mammals

“…However, T cellspecific Cic null mice did not show T-ALL phenotypes up to 14 months of age 33 , suggesting that the loss of CIC in T cells may be insufficient to cause T-ALL, and CIC deficiency in other types of immune cells may contribute to disease onset in mice. Decreased CIC expression at the protein level is frequently observed in various types of cancer [19][20][21]28,46 . Moreover, the CIC protein levels are often not correlated with the mRNA levels within the same cancer samples, suggesting that CIC exhibits robust post-transcriptional regulation in cancer cells 19,21 .…”

“…Nuclear expression of CIC decreases gradually as prostate cancer (PC) becomes more aggressive 20 . CIC levels are also substantially downregulated in hepatocellular carcinoma (HCC), glioblastoma (GBM), and colorectal cancer (CRC) 19,21,28 . The decreased expression of CIC leads to the derepression of PEA3 group genes, thereby promoting cell growth and invasion in PC, HCC, GBM, and CRC cell lines [19][20][21]28 .…”

“…CIC levels are also substantially downregulated in hepatocellular carcinoma (HCC), glioblastoma (GBM), and colorectal cancer (CRC) 19,21,28 . The decreased expression of CIC leads to the derepression of PEA3 group genes, thereby promoting cell growth and invasion in PC, HCC, GBM, and CRC cell lines [19][20][21]28 . Notably, the major PEA3 group members (e.g., ETV1, ETV4, or ETV5) regulated by CIC differ among cancer cell types; the expression of ETV5 and ETV4 is most highly and significantly upregulated by CIC deficiency in PC and HCC cell lines, respectively 20,21 .…”

“…CIC-DUX4 fusion proteins activate the expression of ETV1, ETV4, and ETV5, which encode oncogenic transcription factors 18 , thereby promoting cancer progression 17 . Many studies have verified that CIC functions as a tumor suppressor in various types of cancer [19][20][21][22][23][24][25][26][27][28] . Endogenous functions of CIC have been elucidated by examinations of the phenotypes of Cic mutant mice.…”