Identification of a novel homeobox-containing gene, LAGY, which is downregulated in lung cancer

We have isolated a novel gene, lung cancer-associated gene Y (LAGY), by suppression subtractive hybridization. The nucleotide sequence of LAGY predicts a small protein of 73 amino acids containing a putative homeobox domain with a molecular mass of 8.1 kD. Multipletissue Northern blot analysis revealed that LAGY is present in human placenta, lung, brain, heart and skeletal muscle. Gene mapping locates LAGY on chromosome 4q11-13.1. The expression of LAGY mRNA was widely lost in 18 lung tumor cell lines comprising all major histological types, as shown by Northern blot analysis and semiquantitative reverse transcriptionpolymerase chain reaction. In an investigation of 72 primary lung tumors, this gene was significantly downregulated in tumors compared to 9 normal lung tissue samples. There was a significant reduction of LAGY expression in squamous cell carcinoma (SCC; n = 27) with increasing grade and stage. No expression was detectable in two high-grade SCCs or two small cell and large cell lung carcinomas (n = 4 for each). In adenocarcinoma (n = 37), expression was reduced; however, this did not reach statistical significance. Since homeodomain-containing genes are known to transcriptionally regulate key cellular processes and are associated with carcinogenesis, we suggest that LAGY might be linked to lung cancer development and progression.