Two variants of the human hepatocellular carcinoma-associated HCAP1 gene and their effect on the growth of the human liver cancer cell line Hep3B

We have cloned a cDNA from chromosome band 17p13.3, designated as HCAPI (HCC-associated protein 1, originally named HC56). Database searches revealed that HCAPI shares most of its open reading frame with GEMIN4. Single nucleotide polymorphism (SNP) screening revealed a high incidence of SNP in the coding region of HCAPI (12 SNP sites). A collection of 140 controls and 22 cases from the Qidong area was genotyped at 6 SNP sites. The 22 cases exhibited higher frequencies of minor alleles than did the controls, and 2 sites revealed significant differences between the controls and the cases. We constructed 2 haplotypes, HCAPI-N (with common alleles at 5 SNP sites) and HCAPI-M (with minor alleles at 5 SNP sites), in a mammalian expression system. Both haplotypes resulted in a remarkable reduction in colony formation and suppression of cell growth after being transfected into the human hepatocellular carcinoma (HCC) cell line. The inhibitory effect of HCAPI-N was stronger than that of HCAPI-M. Different haplotypes also resulted in different gene expression profiles in the Hep3B cell line according to an examination of 588 genes on an Atlas membrane. The expression induced by HCAPI-M caused an up-regulation of genes involved in cellular proliferation and a down-regulation of genes involved in cellular apoptosis and DNA repair. These results, in addition to the statistical data, are biological evidence that the HCAPI-M variant of HCAPI has a reduced inhibitory effect on hepatocarcinoma cell growth and an impaired DNA repair system. This suggests that HCAPI-M may be related to cancer susceptibility. (C) 2003 Wiley-Liss, Inc.