Disease relevance of CHFR

• We found CpG methylation-dependent silencing of CHFR expression in 45% of cancer cell lines, 40% of primary colorectal cancers, 53% of colorectal adenomas, and 30% of primary head and neck cancers [1].
• In the present study, we examined the functional consequences of epigenetic inactivation of the mitotic checkpoint gene CHFR in gastric cancers [2].
• This is the first description of aberrant hypermethylation of the CHFR gene in any type of human cancer, and provides further evidence of the involvement of multiple checkpoint alterations in lung cancer [3].
• We report here that in colorectal cancer, inactivation of the MLH1 gene is frequently accompanied by hypermethylation of the CpG island in the promoter of the mitotic gene checkpoint with forkhead and ring finger domains (CHFR) [4].
• CHFR promoter hypermethylation in colon cancer correlates with the microsatellite instability phenotype [4].

High impact information on CHFR

• To explore whether downregulation of Chfr contributes directly to tumorigenesis, we generated Chfr knockout mice [5].
• Expression of the mitotic checkpoint protein Chfr is lost in 20-50% of primary tumors and tumor cell lines [5].
• In contrast, the tumour cell lines that had lost chfr function entered metaphase without delay [6].
• Ectopic expression of wild-type chfr restored the cell cycle delay and increased the ability of the cells to survive mitotic stress [6].
• Here, we show that in response to microtubule poisons this "antephase" checkpoint is primarily mediated by the p38 stress kinases and requires the Chfr protein that is absent or inactive in several transformed cell lines and lung tumors [7].

Chemical compound and disease context of CHFR

• CHFR expression was silenced by DNA methylation of the 5' region of the gene in 20% of the gastric cancer cell lines tested and in 39% of primary gastric cancers; expression could be restored by treatment with 5-aza-2'-deoxycytidine, a methyltransferase inhibitor [2].
• In conclusion, our data suggested that low CHFR expression associated with high mitotic indices in response to nocodazole treatment were common in the breast cancer cell lines studied [8].
• In this study, we investigated epigenetic CHFR inactivation in human gastric cancers by examining CHFR expression and methylation status in gastric cancer cell lines with RT-PCR analysis, bisulfite PCR and sequencing [9].
• Two of 10 gastric cancer cell lines (20%) showed Chfr promoter hypermethylation with resultant loss of expression, which could be restored by 5-aza-2' deoxycytidine treatment [10].

Biological context of CHFR

• CHFR, a novel checkpoint gene inactivated in human cancer, delays chromosome condensation in cells treated with microtubule poisons [11].
• After exposure to microtubule poisons, the CHFR-expressing cells arrested transiently in early prophase with a characteristic ruffled morphology of the nuclear envelope and no signs of chromosome condensation [11].
• The CHFR mitotic checkpoint protein delays cell cycle progression by excluding Cyclin B1 from the nucleus [11].
• Ectopic expression of Cyclin B1 with a mutant nuclear export sequence induced chromosome condensation, and thus overcame the CHFR checkpoint [11].
• Intermolecular fluorescence resonance energy transfer analysis identified a distinct fraction of CHFR that interacts with PML in living cells [12].

Anatomical context of CHFR

• To address this question, we analyzed the pattern of CHFR expression in a number of human cancer cell lines and primary tumors [1].
• CHFR downregulation has been found in primary cancers or in the established tumor cells of various origins, such as the lung, colon, esophagus, and stomach [13].
• Aberrant methylation of the CHFR gene in digestive tract cancer [14].
• A Xenopus cell-free system for analysis of the Chfr ubiquitin ligase involved in control of mitotic entry [15].
• As for non-neoplastic gastric epithelia, 1% (one of 91) from noncancer-bearing and 5% (four of 71) from cancer-bearing stomachs exhibited Chfr promoter hypermethylation [10].

Associations of CHFR with chemical compounds

• Apparently, the absence of CHFR is associated with sensitivity of cells to mitotic stress caused by microtubule inhibition, and restoration of CHFR expression by 5-aza-2'-deoxycytidine or adenoviral gene transfer restored the checkpoint [2].
• Transfection of CHFR in one of these cancer cell lines lowered the mitotic index after nocodazole treatment [8].
• The DNA methylation status of the CHFR gene was examined by combined bisulfite restriction analysis of DNAs from 41 GC tissues and the methylation status was compared to their sensitivity to chemotherapy [16].
• Furthermore, in contrast to previous reports, we find that the checkpoint requires ubiquitylation but not proteasome activity, which is in agreement with the recent demonstration that Chfr conjugates ubiquitin through lysine 63 and not lysine 48 [7].
• Specifically, the Chfr pathway prolongs the phosphorylated state of tyrosine 15 in Cdc2 [17].

Enzymatic interactions of CHFR

• The checkpoint protein Chfr is a ligase that ubiquitinates Plk1 and inhibits Cdc2 at the G2 to M transition [17].

Regulatory relationships of CHFR

• Using Xenopus cell-free extracts, we demonstrated that Chfr delays the entry into mitosis by negatively regulating the activation of the Cdc2 kinase at the G2-M transition [17].
• Chfr expression is downregulated by CpG island hypermethylation in esophageal cancer [18].

Other interactions of CHFR

• PML bodies control the nuclear dynamics and function of the CHFR mitotic checkpoint protein [12].
• We conclude that the mechanism by which CHFR delays chromosome condensation involves inhibition of accumulation of Cyclin B1 in the nucleus [11].
• The coordinated loss of both mismatch repair caused by methylation of MLH1 and loss of checkpoint control associated with methylation of CHFR suggests the potential to overcome cell cycle checkpoints, which may lead to an accumulation of mutations [4].
• Moreover, CpG methylation and thus silencing of CHFR depended on the activities of two DNA methyltransferases, DNMT1 and DNMT3b, as their genetic inactivation restored CHFR expression [1].
• Epigenetic inactivation of CHFR in nasopharyngeal carcinoma through promoter methylation [19].

Analytical, diagnostic and therapeutic context of CHFR

• Finally, cells with CHFR methylation had an intrinsically high mitotic index when treated with microtubule inhibitor [1].
• Cells not expressing CHFR showed impaired checkpoint function, which led to nuclear localization of cyclin B1 after treatment with docetaxel or paclitaxel, two microtubule inhibitors [2].
• Hypermethylation of CHFR promoter region was also strongly correlated with decreased CHFR expression in NPC cell lines and xenografts [19].
• In 29 patients treated with a combination of S-1 and docetaxel, there was no clear association between the CHFR methylation status and response to chemotherapy (p = 0.092) [16].
• MATERIALS AND METHODS: Ninety-eight colorectal cancer patients were examined using a methylation-specific PCR (MSP) for CHFR CpG island in primary tumors [20].

References