Tumor-specific exon creation of the HELLS/SMARCA6 gene in non-small cell lung cancer

To identify tumor-suppressor genes on chromosome 10 in non-small cell lung cancers, we isolated 10 types of splicing variant of the HELLS/SMARCA6 gene transcripts. HELLS/SMARCA6 is a novel member of SNF2 family, which is implicated in cellular functions like chromatin remodeling. Variant 1 was an alternatively spliced isoform containing an insertion of a 44 ntd intronic sequence between exons 3 and 4, giving rise to a premature termination of translation. Expression of variant 1 was detected exclusively in lung cancer specimens (11 of 43 cases, 26%) but was not detected in corresponding normal tissues. The D10S520 marker in the proximity of the HELLS/SMARCA6 gene showed prevalent allelic loss (41%) compared to flanking markers (25-31%). These results suggest that loss of function of HELLS/SMARCA6 by allelic loss and aberrant proteins by tumor-specific exon creation may result in epigenetic deregulation, leading lung cells to malignancy or its progression.