Unchanged frequency of loss of heterozygosity and size of the deleted region at 8p21-23 during metastasis of lung cancer

The genetic mechanisms involved in lung cancer development and progression are beginning to be understood. Many studies have documented frequent loss of heterozygosity (LOH) at specific chromosomal regions in cancer cells; this implies that tumor suppressor genes (TSG) are usually present in those regions. Recently, it has been reported that LOH or chromosomal deletions at chromosome 8p21-23 represent early events frequently occurring in lung cancer. In addition, the size of these chromosome 8 deletions, as well as their frequency, was also reported to increase during lung cancer progression. To determine the spectrum and frequency of alterations of chromosome 8p21-23 in human lung cancer and whether these increase with progression of the tumors, we performed LOH analysis of chromosome 8p and 3p in the genomic DNA from cells from primary and metastatic sites of lung cancer, as well as from normal lung. We studied 35 subjects with primary lung cancer including 30 tumors with distant metastasis. Detection of allelic deletion utilized a PCR-based approach of microsatellite polymorphism analysis, which was performed using the microsatellite markers D8S1130, D8S1106, D8S511, D8S1827, D8S549, D8S261, LPL, D8S258, D8S136, NEFL, D3S1295, D3S1313, D3S1234, D3S1300, D3S1351, D3S1339, and D3S1340. The overall allelic deletion rates were 10 of 28 (35.7%) at 8p and 13 of 33 (39.4%) at 3p. The allelic deletions in the primary cancer and its metastatic sites were in each case identical in both frequency and size of the deleted regions. In our analysis, 8p21-23 deletions were not always associated with 3p deletions in primary lung cancer. These results therefore suggest that allelic deletion at chromosome 8p21-23 is an early and frequent event in the carcinogenesis and development of lung cancer, independent of chromosome 3p deletion. However, a continuing increase in the frequency of LOH at 8p21-23 and in the size of the deleted region rarely occurs during the process of metastasis.