Deficiencies in Chfr and Mlh1 synergistically enhance tumor susceptibility in mice
Zheng Fu, Kevin Regan, Lizhi Zhang, Michael H. Muders, Stephen N. Thibodeau, Amy French, Yanhong Wu, Scott H. Kaufmann, Wilma L. Lingle, Junjie Chen, Donald J. Tindall
Zheng Fu, Kevin Regan, Lizhi Zhang, Michael H. Muders, Stephen N. Thibodeau, Amy French, Yanhong Wu, Scott H. Kaufmann, Wilma L. Lingle, Junjie Chen, Donald J. Tindall
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Research Article Oncology

Deficiencies in Chfr and Mlh1 synergistically enhance tumor susceptibility in mice

Abstract

Genetic instability, which leads to an accumulation of various genetic abnormalities, has been considered an essential component of the human neoplasic transformation process. However, the molecular basis of genomic instability during tumorigenesis remains incompletely understood. Growing evidence indicates that checkpoint with forkhead and ring finger domains (CHFR), a recently identified mitotic checkpoint protein, plays an important role in maintaining chromosome integrity and functions as a tumor suppressor. In this study, we used high-throughput technology to conduct gene expression profiling of human colon cancers and found that loss of CHFR expression frequently occurred in colon cancers with high microsatellite instability (MSI-H). Downregulation of CHFR expression was closely associated with overexpression of Aurora A, an important mitotic kinase. Mice with deficiencies in both Chfr and Mlh1 (the gene that encodes the DNA mismatch-repair protein Mlh1) displayed dramatically higher incidence of spontaneous tumors relative to mice deficient for only one of these genes. These results suggest that defects in both Chfr and Mlh1 synergistically increase predisposition to tumorigenesis.

Authors

Zheng Fu, Kevin Regan, Lizhi Zhang, Michael H. Muders, Stephen N. Thibodeau, Amy French, Yanhong Wu, Scott H. Kaufmann, Wilma L. Lingle, Junjie Chen, Donald J. Tindall

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Figure 4

Deficiencies in both Chfr and Mlh1 lead to increased chromosomal aberrations.

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Deficiencies in both Chfr and Mlh1 lead to increased chromosomal aberrat...
(A) Chfr–/–Mlh1–/– cells show a rate of aneuploidy similar to that of Chfr–/–Mlh1+/+ cells. We counted the chromosome number of 100 metaphase spreads/sample from P3 MEFs. Two different MEF lines/genotype were used. (B) Representative pictures of metaphase spreads from MEFs (WT, Chfr–/–Mlh1–/–, and Chfr+/+Mlh1–/–). Arrows indicate different types of aberrations. Original magnification, ×1000. (C) Spontaneous chromosomal aberrations were evaluated in MEFs with indicated genotypes. *P < 0.01, compared with Chfr+/+Mlh1+/+; **P < 0.01, compared with Chfr–/–Mlh1+/+; ***P < 0.01, compared with Chfr+/+Mlh1–/– (ANOVA with Bonferroni’s test). (D) DNA damage–induced chromosomal aberrations were scored in MEFs with indicated genotypes. MEFs were treated with 1 Gy of IR and allowed to recover for 1 hour. *P < 0.05, compared with Chfr+/+Mlh1+/+; **P < 0.05, compared with Chfr–/–Mlh1+/+ (ANOVA with Bonferroni’s test). Two different MEF lines/genotype were used in C and D. Columns indicate mean values from 2 MEF lines; error bars show SD. Number of chromosomal aberrations per chromosome is presented. Results of individual MEF line from C and D are presented in Supplemental Figure 3. (E) Mitotic index was determined in MEFs with indicated genotypes. Two different MEF lines/genotype were used. The mitotic index is presented as the average percentage of histone H3-Ser28–stained nuclei. Over 1000 DAPI-stained nuclei were evaluated for each genotype from triplicate experiments. *P < 0.05, compared with Chfr+/+Mlh1+/+ (ANOVA with Bonferroni’s test). Results shown are mean ± SD.