Characterization of NF-kappa B expression in Hodgkin's disease: Inhibitionof constitutively expressed NF-kappa B results in spontaneous caspase-independent apoptosis in Hodgkin and Reed-Sternberg cells

Although the neoplastic cells of classical Hodgkin's disease (CHD) demonstr ate high levels of constitutively active nuclear NF-kappaB, the precise phy siologic and clinical significance of NF-kappaB expression is currently und efined Expression of active NF-kappaB p65(Rel A) was evaluated in patient s amples of CHD and nodular lymphocyte predominance Hodgkin's disease. The ac tion of the chemical NF-kappaB inhibitors gliotoxin and MG132 and the effec t of NF-kappaB inhibition utilizing an adenovirus vector carrying a dominan t-negative I kappaB alpha mutant (Ad5I kappaB) were then demonstrated in CH D cell lines (L428, KMH2, and HS445). Hodgkin and Reed-Sternberg (HRS) cell s from all patient and cell line specimens showed strong immunopositivity f or active p65(Rel A). Expression was also seen in lymphocytic/histiocytic c ells from all cases of nodular lymphocyte predominance Hodgkin's disease. A fter chemical NF-kappaB inhibition, p65(Rel A) was significantly reduced in nuclear extracts from cultured HRS cells as revealed by electrophoretic mo bility shift assays. Furthermore, chemical NF-kappaB inhibition resulted in time- and concentration-dependent apoptosis in HRS cells. With the excepti on of MG132-induced apoptosis in HS445, apoptosis by chemical NF-kappaB inh ibition was not significantly altered by preincubation with various caspase inhibitors (z-DQMD-FMK, z-DEVD-FMK, z-VAD-FMK, z-VEID-FMK, and z-IETD-FMK) . Regardless of the chemical inhibitor used, no significant change in caspa se-3 functional activity was found in CHD cell lines. HRS cells infected wi th Ad5I kappaB also showed a marked increase in spontaneous apoptosis compa red with wild type adenovirus-infected and control cells. Overall, the inhi bition of active NF-kappaB in HRS cells resulting in spontaneous caspase-in dependent apoptosis demonstrates a critical role for NF-kappaB in HBS cell survival and resistance to apoptosis.