OBJECTIVETo investigate the function of unclassical NF-kappaB signaling pathway and TNF associated-factor (TRAF)-3 in Hodgkin's lymphoma (HL) cells, and explore a reasonable explanation for alternative NF-kappaB signaling pathway activation in HL cells.

METHODSThe intranuclear NF-kappaB activity in L428 and KM-H2 cells was examined by electrophoretic mobility shift assay (EMSA). The NF-kappaB DNA complex in L428 cell nuclear extracts was further quantified by an ELISA-based NF-kappaB family transcription factor activity assay. The expression of other NF-kappaB family members in the cytoplasm, and the TRAF3 expression were detected by Western blot analysis. The effects of TRAF3 on the unclassical NF-kappaB signaling pathway in L428 cells were studied by transient expression of TRAF3.

RESULTSThe NF-kappaB signaling pathway activity persistently remained in L428 and KM-H2 cells. Both classical and unclassical NF-kappaB activity in L428 cells was highly expressed. There were enhanced p52 protein accumulation and RelB expression and a very weak expression of TRAF3 in both L428 and KM-H2 cells. Transient transfection of TRAF3-expression vector increased the TRAF3 expression and blocked the p100 processing and p52 protein accumulation in both cells.

CONCLUSIONThe classical as well as the unclassical NF-kappaB activities characterized by p100 processing and p52-RelB nuclear localization are persistently present in HL cells. Lack of the TRAF3 expression might be one of the reasons for the aberrant expression of the unclassical NF-kappaB activity.