1. ¹Department of Pathology, Loyola University Medical Center, Maywood, Illinois
2. ²Cardinal Bernardin Cancer Center, Loyola University Medical Center, Maywood, Illinois
3. ³Department of Pathology University of Michigan Medical School, Ann Arbor, Michigan

Correspondence: Serhan Alkan, M.D., Department of Pathology, Loyola University Medical Center, EMS Building, Suite 2230, 2160 S. First Avenue, Maywood, IL 60153. e-mail: SALKAN@luc.edu; fax: 708-327-2620

⁴Keith F. Izban, M.D., received the Society for Hematopathology, Pathologist-in-training award 1999 for presenting data from this investigation.

Accepted 16 August 2000.

Abstract

Although the neoplastic cells of classical Hodgkin's disease (CHD) demonstrate high levels of constitutively active nuclear NF-B, the precise physiologic and clinical significance of NF-B expression is currently undefined. Expression of active NF-B p65(Rel A) was evaluated in patient samples of CHD and nodular lymphocyte predominance Hodgkin's disease. The action of the chemical NF-B inhibitors gliotoxin and MG132 and the effect of NF-B inhibition utilizing an adenovirus vector carrying a dominant-negative IB mutant (Ad5IB) were then demonstrated in CHD cell lines (L428, KMH2, and HS445). Hodgkin and Reed-Sternberg (HRS) cells from all patient and cell line specimens showed strong immunopositivity for active p65(Rel A). Expression was also seen in lymphocytic/histiocytic cells from all cases of nodular lymphocyte predominance Hodgkin's disease. After chemical NF-B inhibition, p65(Rel A) was significantly reduced in nuclear extracts from cultured HRS cells as revealed by electrophoretic mobility shift assays. Furthermore, chemical NF-B inhibition resulted in time- and concentration-dependent apoptosis in HRS cells. With the exception of MG132-induced apoptosis in HS445, apoptosis by chemical NF-B inhibition 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 caspase-3 functional activity was found in CHD cell lines. HRS cells infected with Ad5IB also showed a marked increase in spontaneous apoptosis compared with wild type adenovirus-infected and control cells. Overall, the inhibition of active NF-B in HRS cells resulting in spontaneous caspase-independent apoptosis demonstrates a critical role for NF-B in HRS cell survival and resistance to apoptosis.