OBJECTIVE HLCDG1, which locates in chromosome 5q33 (between D5S436 and D5S470),is a novel gene that our laboratory has cloned recently. The expression of HLCDG1 gene was significantly down-regulated or deleted in the primary lung carcinoma. This study was designed to observe if HLCDG1 has the potential to suppress growth of lung carcinoma cells. METHODS The recombinant plasmid, pcDNA3.1(+)/HLCDG1, was constructed and subsequently transfected into A549 cells through liposome transfection. The A549 cells stably expressing HLCDG1 gene were established by G418 selection. RT-PCR was used to demonstrate the expression of HLCDG1 gene. Furthermore, the cell proliferation assay, the soft agar assay, and the tumorigenesis assay were used to analyze the malignant phenotype of the HLCDG1-transfected cells. RESULTS The HLCDG1-transfected cells exhibited the expression of HLCDG1 mRNA by RT-PCR. The population double time (PDT) of HLCDG1-transfected group, vector-transfected group, and nontransfected group were 70.0 hours, 43.3 hours, and 39.5 hours, respectively; the difference between HLCDG1-transfected group and the other two groups was significant (P< 0.05). The colony formation rates of HLCDG1-transfected group, the vector-transfected group, and nontransfected group were 8.5%, 29.0%, and 35.0%, respectively. The rate of HLCDG1-transfected cells was markedly lower than those of the other two groups (P< 0.05). Moreover, these clones were injected into athymic nude mice. After 43 days, they were killed, and their tumors were isolated. These tumors weighed 0.120g, 0.612g, and 0.924g, respectively. CONCLUSIONS The expression of HLCDG1 in A549 cells may have the potential to suppress tumor cell growth and the tumorigenesis of A549 cells transplanted in nude mice. These results suggested that HLCDG1 gene might be a good candidate of tumor suppressor gene correlated with lung carcinoma.