Frequent impairment of the spindle assembly checkpoint in hepatocellular carcinoma

Abstract

BACKGROUNDChromosomal instability (CI) leading to aneuploidy is one form of genetic instability, a characteristic feature of various types of cancers. Recent work has suggested that CI can be induced by a spindle assembly checkpoint defect. The aim of the current study was to determine the frequency of a defect of the checkpoint in hepatocellular carcinoma (HCC) and to establish whether alterations of genes encoding the checkpoint were associated with CI in HCC.METHODSAneuploidy and the function of the spindle assembly checkpoint were examined using DNA flow cytometry and morphologic analysis with microtubule disrupting drugs. To explore the molecular basis, the authors examined the expression and alterations of the mitotic checkpoint gene, BUB1, using Northern hybridization and direct sequencing in 8 HCC cell lines and 50 HCC specimens. Furthermore, the authors examined the alterations of other mitotic checkpoint genes, BUBR1, BUB3, MAD2B, and CDC20, using direct sequencing in HCC cell lines with aneuploidy.RESULTSAn impaired spindle assembly checkpoint was found in five (62.5%) of the eight aneuploid cell lines. Transcriptional expressions of the BUB1 gene appeared in all cell lines. While some polymorphic base changes were noted in BUB1, BUBR1, and CDC20, no mutations responsible for impairment of the mitotic checkpoint were found in either the HCC cell lines or HCC specimens, which suggests that these genes did not seem to be involved in tumor development in HCC.CONCLUSIONSThe loss of spindle assembly checkpoint occurred with a high frequency in HCC with CI. However, other mechanisms might also contribute to CI in HCC. Cancer 2002;94:2047–54. © 2002 American Cancer Society.DOI 10.1002/cncr.10448

A double missense variation of theBUB1 gene and a defective mitotic spindle checkpoint in the pancreatic cancer cell line Hs766T

“…This heterozygous nucleotide change would not alter the protein sequence and is likely to be a naturally occurring polymorphism. In addition to this novel polymorphism, several polymorphisms that have been previously reported for BUB1B were also found in other tumors and cell lines (see Table 2) (Cahill et al, 1998;Saeki et al, 2002).…”

A Missense Mutation in Rev7 Disrupts Formation of Polζ, Impairing Mouse Development and Repair of Genotoxic Agent-induced DNA Lesions

“…Thus, Rev7/Mad2l2 might also regulate cell cycle progression as an arbiter of the spindle assembly checkpoint and could contribute to the growth retardation and germ cell depression observed in Rev C70R mutant mice. To test this possibility, we treated Rev7 C70R/C70R MEF with colcemid and harvested the cells hourly over 8 h. The cells were fixed and stained with phosphohistone H3 (Ser-10) antibody, a marker of mitosis, and the mitotic index was measured for each genotype (11,35). We observed increased cell arrest at mitosis in the presence of colcemid in all genotypes (Fig.…”

Cell cycle regulation and hepatocarcinogenesis

“…Consistent with this model, alterations in the expression of genes involved mitotic checkpoint assembly has been detected in these tumors. 84 What are the genes that control the hepatic G 2 /M transition? A series of studies by Costa and colleagues using the partial hepatectomy and carcinogenic animal models has elucidated the importance of the forkhead familiy protein FOXM1B for regulation of hepatocyte proliferation at several stages of the cell cycle including the G 2 /M transition.…”