Objective      To investigate the expression profiles of GPC5 gene in lung adenocarcinoma tumor tissue and corresponding normal tissue

and analyze its mutation.        Methods        The expression differences of GPC5 in tumor tissue and normal tissue of the 2 datasets downloaded from gene expression omnibus (GEO) were analyzed. The somatic mutations and copy number variation (CNV) of GPC5 gene was analyzed through the cancer genome atlas (TCGA). Real-time quantitative PCR was used to detect the expression of GPC5 gene in tumor tissue and matched normal tissue from 39

lung cancer patients for further verification.        Results        The expression level of GPC5 was significantly lower in the tumor tissue than in the matched normal tissue by analyzing 2 datasets from GEO (

P

<

0.05). The results of real-time quantitative PCR confirmed that the expression of GPC5 was significantly lower in the tumor tissue than in the matched normal tissue (

P

<

0.01)

and the expression was significantly lower in tumor tissue of TNM stage Ⅱ to Ⅲa than the tumor at TNM stage Ⅰ (

P

<

0.05).       Conclusion        CNV of GPC5 gene is common in lung adenocarcinoma tissue. Heterozygosity loss may be the cause of reduced expression level of GPC5.