Aim: To investigate immunohistochemical expression and the localization of connexin-43 (Cx-43) in primary lung cancer and its metastases. Introduction: Connexins are transmembrane proteins forming gap junctions that allow intercellular communication. Significance of gap junctions and connexins in lung cancer are not clear enough. Material and Methods: We analyzed autopsy samples of primary and metastatic lung carcinoma from Institute of Pathology in Belgrade. There were 11 primary lung carcinomas, 7 lung cancer metastases in lymph nodes, and 12 haematogenic metastases. We performed immunohistochemical staining for connexin-43 (Cx43) and measured expression (percentage of positive cells and intensity of staining) and localization of Cx43 in primary tumor and its metastases. Results: Lymphatic and hematogenous metastases of lung cancer showed a stronger expression of connexin-43 than primary tumor itself. Unlike 9% of primary carcinoma, 28% of lymphatic metastases and 50% of hematogenous metastases had expression of connexins in more than 50% of tumor cells (p=0.11). The intensity of connexin-43 expression was statistically significantly less in primary lung cancer than in all the metastases together(p=0.04). The expression of this marker was different in different histological types, where small cell carcinoma rarely expressed connexin, while the squamous carcinoma was mostly positive to immunohistochemical staining on Cx43. Dominant localization of expression was the combined cytoplasmic-membranous. Conclusion: Our results showed that lung cancer expresses connexin-43 mostly in cytoplasm as well as on the cell membrane. Further research on a larger sample is required to establish whether Cx-43 could be used as a prognostic biomarker in lung cancer.

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