ACTIVATION OF NUCLERA FACTOR-κ B AND CONTROL OF THE EXPRESSION OF CELL ADHESION MOLECULES IN HUMAN PROSTATE CANCER CELLS

Abstract

(Purpose) Cell adhesion molecules (CAMs) have been considered to play key roles in cancer metastasis through binding of cancer cells to the endothelial cells or matrix. We have found that constitutive expression of E-selectin, ICAM-1 (intercellular adhesion molecule-1) and VCAM-1 (vascular cell adhesion molecule-1) on the cell surface of prostate cancer cell lines, PC-3 LNCaP, and DU145. In an attempt to explain the highly metastatic potential of these cells, we investigated expression of CAMs. Since these expressed CAMs are known to be regulated by a transcription factor NFκB. We have examined if NFκB is activated in these prostate cancer cell lines.
(Material and Method) Expression of E-selectin, ICAM-1, Sialyl-Lewis X, LFA-1 (lymphocyte function-associated antigen-1), integrinα 4, and integrinβ1 were examined by indirect immunofluorescent staining and Western blotting using specific monoclonal antibodies. We then examined whether pro-inflammatory cytokines known to stimulate NFκB, IL-1 and TNF, could drive the nuclear translocation of NFκB. Ten ng/ml of recombinant human IL-1β or TNFα was added to the cell culture and the CAMS level, as well as nuclear translocation of NFκB, was examined.
(Results) The staining levels of ICAM-1, VCAM-1, and integrinβ1 were highly elevated in PC-3 and DU145. In surprising, NFκB was retained in the cytoplasm (as an inactive form) and not detectable in the nucleus (active form) as demonstrated by immunofiuorescence. Although time-dependent expression of these molecules were explored, the level of ICAM-1 and VCAM-1 on the cell surface were unchanged. However, nuclear translocation of NFκB could be induced.
(Conclusion) These observations indicate that while the signaling pathway to NFκB is intact, it is not directed to induction of its target CAM genes. It is possible that other transcription factors might be involved in these cells and that they might to be constitutively stimulated during the carcinogenesis of prostate cancer.