Down-regulation of a novel gene, DRLM, in human liver malignancy from 4q22 that encodes a NAP-like protein.

Frequent observations of allelic loss in chromosomal band 4q21-22 in hepatocellular carcinoma (HCC) have suggested the presence of one or more tumor suppressor genes in this region. We screened HCC cell lines by reverse transcription-polymerase chain reaction (RT-PCR) to detect alterations in expression of genes within the region in question by examining expressed sequence tags located there. These experiments identified a full-length cDNA of 2311 bp in length encoding a novel, 182-amino-acid peptide belonging to the class of nucleosome assemble protein lacking nuclear localization signal sequence. Polyclonal antibody was raised by expression of a constructed recombinant glutathione S-transferase fusion protein. in vitro expression and Western blotting revealed that the novel protein distributed in cytoplasm. This gene showed loss or extreme decrease of expression in five of 13 HCC cell lines. We named it DRLM ('down-regulated in liver malignancy'). Our results suggest that loss of expression of DRLM at 4q21-22 may play an important role in human hepatocarcinogenesis.