Despite the abundant evidence for high allelic loss of chromosome 14q in human cancers (Lee et al., 1997; Chang et al., 1995; Mutirangura et al., 1998; Hu et al., 1999; Hu et al., 2000; Dekken et al., 1999), tumor suppressor genes mapped to this chromosome have yet to be identified due to the complexity of the chromosomal alterations reported. To narrow down the search for candidate genes, we performed monochromosome transfer of chromosome 14 into an esophageal squamous cell carcinoma (ESCC) cell line, SLMT-1 S1. Statistically significant suppression of the tumorigenic potential of microcell hybrids (MCHs), containing the transferred chromosome 14, provides functional evidence that tumor suppressive regions on chromosome 14 are essential for ESCC. Tumor segregants (TSs) emerging in the...[ Read more ]

Despite the abundant evidence for high allelic loss of chromosome 14q in human cancers (Lee et al., 1997; Chang et al., 1995; Mutirangura et al., 1998; Hu et al., 1999; Hu et al., 2000; Dekken et al., 1999), tumor suppressor genes mapped to this chromosome have yet to be identified due to the complexity of the chromosomal alterations reported. To narrow down the search for candidate genes, we performed monochromosome transfer of chromosome 14 into an esophageal squamous cell carcinoma (ESCC) cell line, SLMT-1 S1. Statistically significant suppression of the tumorigenic potential of microcell hybrids (MCHs), containing the transferred chromosome 14, provides functional evidence that tumor suppressive regions on chromosome 14 are essential for ESCC. Tumor segregants (TSs) emerging in the nude mice during the tumorigenicity assay were analyzed by detailed PCR-microsatellite typing to identify non-randomly eliminated critical regions (CRs). A 680 kb CR mapped to 14q32.13 and a ~2.2 Mb CR mapped to 14q32.33 were delineated. Dual color bacterial artificial chromosome fluorescent in situ hybridization (BAC FISH) analysis of MCHs and TSs verified the selective loss of the 14q32.13 region. In contrast, similar transfers of an intact chromosome 11 into SLMT-1 S1 did not significantly suppress tumor formation. These functional complementation studies showing the correlation of tumorigenic potential with critical regions of chromosome 14 validate the importance of the 14q32 region in tumor suppression in ESCC. The present study also paves the path for further identification of novel tumor suppressor genes (TSGs), which are relevant in the molecular pathogenesis of ESCC.

Chromosomal regions with a high rate of loss of heterozygosity (LOH) may implicate candidate TSG(s) that is/are involved in the molecular pathogenesis of ESCC. In ESCC, chromosome 13q LOH ranged from 48% - l00%, as independently observed from different groups (Boynton et al., 1991; Huang et al., 1992; Hu et al., 2000; Li et al., 2001; Li et al., 2003; Hu et al., 2003) and 13q genetic aberrations of 22% - 100% revealed by comparative genomic hybridization (CGH) (Pack et al., 1999; Tada et al., 2000; Wei et al., 2002). However, it is still unclear if the loss of genetic materials is a cause or consequence of ESCC, as this indirect evidence only implicates the presence of candidate TSG(s). Direct functional evidence for tumor suppression after transferring genetic materials is still scanty in ESCC. A tumor suppression effect was observed after the transfer of chromosome 13 into SLMT-1 S1. The tumor suppressive effect observed in MCH13-113 suggested TSGs may be located at 13q34. Three critical regions, CR1 and CR2, at 13q12.3, and CR3 at 13q14.11, were delineated during TS deletion analysis. TSGs important for ESCC may be located on 13q12.3 and 13q14.11.

The first functional proof from microcell-mediated chromosome transfer (MMCT) that tumor suppressive regions on chromosomes 13 and 14 are essential for ESCC development is provided in the current study.