CHFR (Checkpoint with fork-head associated and ring finger)

Growing evidence in mice, primary human tumors, and mammalian cell culture models indicate that CHFR may function as a potent tumor suppressor. CHFR functions as part of an early G2/M checkpoint, more specifically in antephase. Antephase refers to late G2 when chromosome condensation starts. This early mitotic checkpoint causes a delay in chromosome condensation in response to mitotic stresses. The human CHFR gene was originally identified during a search for novel cell cycle checkpoint proteins that have fork-head associated domains. Initial analysis indicated that the CHFR-associated G2/M checkpoint was inactivated in a subset of cancers as demonstrated by high mitotic indices (a high percentage of cells that have condensed chromosomes) in response to exposure to the microtubule poison, nocodazole, due to lack of CHFR expression or CHFR mutations in various cancers. Many other studies showed promoter hypermethylation leading to low/no expression of CHFR

Overexpressed Genes/ESTs and Characterization of Distinct Amplicons on 17823 in Breast Cancer Cells

Abstract17823 is a frequent site of gene amplification in breast cancer. Several lines of evidence suggest the presence of multiple amplicons on 17823. To characterize distinct amplicons on 17823 and localize putative oncogenes, we screened genes and expressed sequence tags (ESTs) in existing physical and radiation hybrid maps for amplification and overexpression in breast cancer cell lines by semiquantitative duplex PCR, semiquantitative duplex RT-PCR, Southern blot, Northern blot analyses. We identified two distinct amplicons on 17823, one including TBX2 and another proximal region including RPS6KB1 (PS6K) and MUL. In addition to these previously reported overexpressed genes, we also identified amplification and overexpression of additional uncharacterized genes and ESTs, some of which suggest potential oncogenic activity. In conclusion, we have further defined two distinct regions of gene amplification and overexpression on 17823 with identification of new potential oncogene candidates. Based on the amplification and overexpression patterns of known and as of yet unrecognized genes on 17823, it is likely that some of these genes mapping to the discrete amplicons function as oncogenes and contribute to tumor progression in breast cancer cells