Mapping of a candidate colorectal cancer tumor‐suppressor gene to a 900‐kilobase region on the short arm of chromosome 8

Abstract

Loss of heterozygosity (LOH) on 8p occurs at high frequencies in many tumor types, including colorectal carcinoma (CRC). We previously used microcell-mediated chromosome transfer (MMCT) into the CRC cell line SW620 to map a approximately 7.7-Mb colorectal cancer-suppressor region (CRCSR) at 8p22-23.1. In the current study, we transferred small fragments of this CRCSR into SW620 to refine the region further. Two microcell hybrids containing a 321- to 898-kb region around the D8S552 marker at 8p23.1 showed suppression of soft agar clonicity and tumorigenicity in athymic mice when compared to control cell lines. These data suggest that the putative colorectal tumor-suppressor gene is within this small region. We analyzed two candidate genes within this region: FLJ23749 and KIAA1456. Expression of both genes was detected in normal colonic crypt cells and in mucosa. Quantitative reverse transcriptase polymerase chain reaction showed downregulation of KIAA1456 in 9 of 12 primary colorectal tumors compared to matching normal mucosa, but normal or increased expression of FLJ23749. FLJ23749 was expressed in all CRC cell lines tested; however, KIAA1456 was downregulated in three cell lines, including SW620, and was restored in the suppressed microcell hybrids. 5'aza-2'Deoxycytidine treatment of the downregulated cell lines restored expression of KIAA1456, but bisulfite genomic sequencing did not show a correlation between promoter methylation and expression. Forty percent of the primary tumors showed LOH at this CRCSR locus, and mutation analysis revealed somatic mutations in 1 of 88 primary colorectal tumors for both KIAA1456 and FLJ23749. Despite the rarity of somatic mutations, the expression data suggest that KIAA1456 is still a candidate for the putative 8p colorectal cancer tumor-suppressor gene.

Codon-biased translation can be regulated by wobble-base tRNA modification systems during cellular stress responses

“…Several lines of tumorigenic colorectal cancer cells, including SW620 and HCT116, do not express the yeast Trm9 homolog hTRM9L, most likely due to epigenetic gene silencing. 8,93 The latter is consistent with the observation that treatment of SW620 cells with 5-deazacytidine promoted expression of hTRM9L and led to a significant decrease in tumor size in xenograft models. Similarly, SW620 and HCT116 cells reengineered to express hTRM9L also had a significant decrease in tumor growth as well as resistance to the aminoglycoside antibiotic paromomycin, which kills in part by inducing translational errors.…”

Are there any more ovarian tumor suppressor genes? A new perspective using ultra high‐resolution copy number and loss of heterozygosity analysis

“…Regions primarily targeted by CN loss, for example 8p, where almost all LOH is accompanied by CN loss, may be more likely to target multiple genes by haploinsufficiency, rather than LOH unmasking gene mutation or methylation. This possibility may explain why mutation searches for TSGs on 8p have been notably fruitless compared with functional evidence from microcell-mediated chromosome transfer (Gustafson et al, 1996;Lai et al, 2003;Flanagan et al, 2004). In contrast, regions with more CNN LOH are clearly not primarily targeting haploinsufficient TSGs.…”

Transfer RNA Methytransferases and Their Corresponding Modifications in Budding Yeast and Humans: Activities, Predications, and Potential Roles in Human Health

“…A 2011 study has uncovered a new function for hABH8. In the study, hABH8 was shown in vitro and in vivo to generate one stereoisomer of 5-methylcarbonylhydroxymethyluridine (mchm HKIAA1456 has been labeled a putative tumor suppressor for colorectal cancer and was found to be downregulated in 9 of 12 primary tumors analyzed as well as in several colon cancer cell lines (Flanagan et al, 2004). However, hKIAA1456 mutations were only found in one of the 88 tumors studied and epigenetic silencing is a likely route to inactivation in tumors.…”