Significance of α9β31 and αvβ 6 integrin expression in breast carcinoma

Background: Both α9β31 and αvβ36 integrins have been newly identified from the tracheal epithelium of guinea pig. It has been pointed out that α9β1 functions as a receptor for tenascin-C and osteopontin. As for the ligands ofαvβ6, fibronectin and tenascin-C have been identified. It has not been ascertained whether α9β1 and αrvβl6 are expressed in normal breast tissue, benign breast lesion or breast carcinoma. Methods: Immunohistochemical staining forαr9β31 and αvβ6 was performed in benign breast lesion and breast carcinoma specimens. Western blotting was carried out on 1 1 breast carcinoma cases. Results: α9β l was expressed in the cytoplasm of carcinoma cells in 23 of 90 cases (26%) and av/36 in the membrane of carcinoma cells in 16 of 90 cases (18%). However, these findings of α9β31 and αvβ36 did not correlate with any clinicopathological factors including the patients' age, tumor size, histological type of carcinoma, location of carcinoma cells and hormone receptor status. With regard to the histological grade of carcinoma, αvβ6 and α9β31 expression did not statistically correlate, although no expression of ave6 was observed in 14 cases of Grade I. On Western-blott analysis strong and weak bands consistent with αvβ36 were noted in the membrane fraction extracted from breast carcinoma cells. On the other hand weak bands consistent with a9 subunit were noted in the whole cell lysates of breast carcinoma cells and very weak or no bands consistent with αr9 subunit were noted in the membrane fraction extracted from the breast carcinoma cells. Conclusions: Significance of a9/31 and αvβ6 integrins expression in breast carcinoma was still unknown on clinicopathological examination. The findings of Western blot analysis may indicate that the transportation system of glycoproteins such as integrins to the cell membrane of carcinoma cells is disturbed, although these integrins can be produced.