Tumor recurrence is identified as a significant adverse prognostic indicator in patients with colorectal cancer (CRC) following curative resection [2]. In our study, we're looking into new key genes for CRC using bioinformatics, especially those linked to autophagy-related genes. We firstly identified CENPF as a top candidate gene in CRC progression, examined its functional role in metastatic progression and demonstrated the therapeutic value of targeting CENPF in inhibiting CRC liver metastasis. Mechanically, we found CENPF protein could undergo ubiquitination, leading to subsequent proteasomal degradation. And USP4 as a deubiquitinating enzyme (DUB), interacted with and deubiquitinated CENPF, thereby stabilizing it. Taken together, our data showed that a novel USP4-CENPF axis played an important regulatory role in CRC metastasis and may serve as a potential target for CRC treatment.
Due to the complexity and variability of CRC, effective targeted therapies for CRC and the availability of effective signatures that can accurately predict recurrence remain limited [20]. Autophagy, as a mechanism supporting cell survival, has emerged as a pivotal factor in cancer metastasis. Its impact can be twofold: either promoting or inhibiting metastasis, contingent upon factors such as cancer cell subtype, the tumor microenvironment, and the stage of tumor progression [36, 37]. We conducted correlation analysis using multiple transcriptome sequencing datasets in CRC and an autophagy gene list to identify candidate gene sets. We then intersected the differences between cancer and adjacent tissues to identify potential important targets for CRC treatment, in which is a candidate set comprising 54 genes. Among them, fifteen candidate genes, including DACH1, GALNT6, IFITM1, EGFL6, WNT5A, CDK1, GDF15, SOX9, KIF23, CPNE1, BHLHE40, NEK2, ASPM, PLA2G16, and PMEPA1, have been proven to play important roles in CRC [38–52], which indicated a certain degree of reliability in our screening process. Using two different siRNAs to target candidate genes, we examined their effects on the migratory capacity of HCT116 colorectal cancer cells. Interestingly, knocking down CENPF with siRNA showed the most pronounced inhibition of HCT116 migration, which has not been previously reported. Therefore, the role of CENPF in CRC has become the focus of our research. Moreover, leveraging data from GEO, TCGA databases, and our own colorectal cancer tissue microarrays from two different centers, we explored CENPF expression patterns and prognostic significance in CRC. Consistently, findings indicated upregulation of both CENPF mRNA and protein in colorectal tumors compared to adjacent normal tissues. In addition, CENPF expression correlated with CRC prognosis, showing more significant predictive efficacy in disease-free survival, indicating its potential oncogenic role in CRC metastasis. Previous results have demonstrated that CENPF was highly expressed in the lung adenocarcinoma (LUAD), and CENPF expression correlated with T stage and poor prognosis [53]. Moreover, CENPF knockout significantly inhibited LUAD cell growth, the tumor growth of mice [53]. Also, CENPF is markedly elevated in pancreatic cancer (PC) and linked to poor patient outcomes [5]. Knocking down CENPF inhibits PC cell proliferation, migration, and EMT, inducing G2/M phase cell cycle arrest and restraining in vivo pancreatic cell growth [5]. Importantly, knocking down CENPF expression significantly altered invasive and migratory capacity of CRC cells, as evidenced from a series of in vitro experiments and in xenograft nude mice models of
liver metastasis in vivo. Therefore, the consistent results from our comprehensive study verified CENPF acted as a novel tumor oncogene in CRC.
Another major finding of our study is that we've uncovered the role of ubiquitination in controlling CENPF protein expression and its functions. Until now, there have been few reports confirming the factors that regulate CENPF expression. Previous research has shown that several members of the CENP family, including CENPA, CENPH, and CENPN, are degraded via the ubiquitin-proteasome pathway[32–34]. First, we discovered that MG132 effectively blocked the degradation of CENPF protein and CENPF underwent ubiquitination modifications, suggesting that CENPF could be regulated by ubiquitin-proteasome axis. To further identify the DUBs that can potentially deubiquitinate
and stabilize CENPF, we screened a human DUB expression library consisting of 53 DUBs-Flag plasmids in HEK293T cells. The top 18 knockdowns of DUB genes that stabilized CENPF level most significantly were selected for a second-round screening
genes. Each of those DUBs was then co-overexpressed together with HA-CENPF in HCT116 cells. Coimmunoprecipitation (co-IP) experiments showed the interaction exists exclusively between USP4 and CENPF. Based on two rounds of screening, we propose that USP4 is the most likely deubiquitinase regulating CENPF stability. Mechanically, USP4 interacts with CENPF and decreases CENPF ubiquitination levels, thus stabilizing it. Accordingly, USP4 expression was significantly positively corelated with CENPF in human CRC samples from two different tertiary hospitals in China, as confirmed by immunohistochemistry. Importantly, the interaction of CENPF and USP4 then controlled the invasion and migration of colorectal cancer. Previous evidence has confirmed a critical role for USP4 in regulating p53, TGFβ, Wnt/β-catenin, and NF-κB signaling, implicating dysregulation of USP4 expression in the development of cancer [54]. In CRC, USP4 has been shown to promote colorectal cancer cell metastasis in vitro and in vivo by regulating the stability and activity of β-catenin and PRL-3 [20, 22]. Previous studies showed that mutating the catalytic residue Cys311 to Ala abolishes USP4's deubiquitination and stabilization of β-catenin. In our study, the C311S mutation in USP4 also lost its ability to stabilize and deubiquitinate CENPF. Thus, we speculate that CENPF is a key downstream target of USP4 in regulating colorectal cancer metastasis. Furthermore, high USP4 and high CENPF are significant determinants of poor survival in patients with CRC.
This study had some limitations as follows. First, we explained how post-translational modifications regulate CENPF's abnormal expression and function. However, we also found that CENPF transcription levels are abnormally elevated in colorectal cancer. Understanding the mechanisms behind this upregulation is essential for effectively targeting CENPF abnormalities. Second, the role of the CENPF-USP4 axis in CRC metastasis has been identified, but the specific downstream molecular mechanisms remain unclear and require further investigation.
In summary, our groundbreaking research, for the first time, has unveiled CENPF as a novel promoter of CRC metastasis and elucidate the molecular mechanism of the interaction between CENPF and USP4 in inducing migration and invasion of colorectal cancer cells, evidenced from molecular, cellular, animal models, and clinical specimens. Thus, USP4-CENPF axis may represent a potential therapeutic target and predictive markers in CRC.