BMC Cancer 2005, 5:104 http://www.biomedcentral.com/1471-2407/5/104 Table 2: Summary of GIRK mRNA expression in lung cells. This is a compilation of data shown in Figures 1–6 & Table 1. Some of the indicated data was not shown. GIRK1 GIRK2 GIRK3 GIRK4 NF NF E E NF NF E E ND ND E E NF NF E Normal primary SAEC PNEC SCLC WBA H69 H146 H187 H209 H526 NSCLC H322 H441 H549 H727 H2170 H226 H520 NF NF E E E NF NF NF NF NF E E E E E E – mRNA expression NF – mRNA expression not found ND – mRNA expression not determined X – human primer not compatible with hamster breast cancers tested [6], and this expression of GIRK1 was associated with a more aggressive clinical behavior. GIRK1 has also been shown to contribute to tumor pro- gression in NSCLC human tumors [24]. Differences in GIRK channel mRNA expression was seen in different types of lung cancer. The three adenocarcino- mas from the lung cancer patient samples did not express GIRK1, and a subset of lung adenocarcinoma cell lines (H322, H441) also did not express GIRK1. However, GIRK1 expression was seen in an adenocarcinoma cell line with alveolar type II cell phenotype (A549). These variations may be due to differences between the Clara cell and the alveolar type II lineage, or it may be due to the small sample size. The cell linage of the lung cancer patient samples is unknown. Data from our laboratory has also indicated differences in responses to anticancer agents between alveolar type II and Clara cells in the lungs [33]. Further research with additional cell lines and tissue samples is needed to determine if the differences in GIRK expression between alveolar type II cells and Clara cells is significant. The two samples from squamous cancer patients also did not express GIRK1 mRNA. However, squamous carcinoma cells lines and a carcinoid cell lines do express GIRK1. In all NSCLC cell lines that express GIRK1, either GIRK2 or GIRK4 mRNA was expressed, indicating that E E E E E E E E ND ND E E E E E E X E E E E E E ND ND E E E E E functional GIRK potassium channels are possible in these non-SCLC cancer cell lines. Our data showing lack of GIRK1 expression in tumors from human adenocarcino- mas and squamous cell carcinomas in is in contrast to Takanami et al. [24]. They found that in 72 NSCLC patients, 69% had high GIRK1 levels and 31% had low GIRK1 levels [24]. The differences may be due to our small sample size, or there may be other factors in cancer patients that affect GIRK1 expression. The expression of GIRK2 or GIRK4 has not been determined in previous studies. The mRNA for GIRK1 & GIRK2 channels have not been detected in the normal cell lines tested, although the mRNA for GIRK4 channels was found in SAE normal cells. Our data indicates more differential expression of GIRK1 and GIRK2 than of GIRK4 in both SCLC and NSCLC cell lines. It is our hypothesis that GIRK4 is less important in lung cancer due to the fact it was expressed in all normal and cancerous cell lines. Further study is needed to determine the importance of GIRK1 and GIRK2 in lung cancer. In addition GIRK3 was found in all cell lines tested, including SAEC and normal hamster PNEC. Since GIRK3 expression was seen in all cells tested, we also feel it is unlikely to be a factor in tumor growth or progression. This hypothesis is supported by data indicating that one of the functions of GIRK3 is to inhibit plasma membrane Page 7 of 10 (page number not for citation purposes)