Increased nuclear factor-κB activation is related to the tumor development of renal cell carcinoma

Although an aggressive phenotype of renal cell carcinoma (RCC) is known to frequently be associated with inflammatory paraneoplastic syndrome including serum C-reactive protein (CRP) elevation, the molecular mechanism underlying this clinical phenomenon as well as what yields the malignant phenotype leading to the progression of RCC has yet to be elucidated. Based on the increased level of inflammatory cytokines such as interleukin-6 in advanced cases of RCC, a cytokine-inducible transcription factor, namely, nuclear factor-kappaB (NF-kappaB), may thus play a role in the progression of RCC. An electrophoretic mobility shift assay (EMSA) was carried out to determine the activity of NF-kappaB. Out of 45 cases of RCC, 15 cases (33%) showed a >200% increase in the NF-kappaB activity in comparison with that seen in normal renal tissue. In locally advanced cases (greater than or equal topT3), 64% (9/14) showed an increased activity whereas it was only observed in 19% (6/31) of localized cases (less than or equal topT2). All three cases with metastases showed an increased NF-kappaB activity. The NF-kappaB activity determined by EMSA was further confirmed by an immunohistochemical analysis using an antibody recognizing the nuclear localization signal (NLS) in p65 subunit of NF-kappaB. The serum CRP elevation correlated with the increased NF-kappaB activation, and therefore NF-kappaB may be a causative transcription factor of inflammatory paraneoplastic syndrome. A high NF-kappaB activity was associated with an increased expression of both the p65 and p50 subunits of NF-kappaB and a concomitant decreased expression of IkappaBalpha. No functional mutations of the IkappaBalpha gene were detected. The NF-kappaB activity may therefore be a late event in carcinogenesis related to tumor development, thereby representing a possible molecular target in the treatment of RCC.