title: Sensitization of multiple myeloma and B lymphoma lines to dexamethasone and gamma-radiation-induced apoptosis by CD40 activation.
abstract: We examined the effects of CD40 activation with dexamethasone (Dex) or 60Co-gamma-irradiation on the growth of malignant B cells in vitro, using the human multiple myeloma (MM) cell line, XG2, and the B lymphoma Daudi cell line as models. Both lines are resistant to Dex and irradiation; 10(-7)M Dex or 10 Gy of gamma-irradiation induced only minimal growth arrest and apoptosis of the cells. Treatment of the cells with the agonistic anti-CD40 monoclonal antibody 5C11 partially inhibited the proliferation of the Daudi cells; XG2 underwent apoptosis. XG2 is an Interleukin-6 (IL-6)-dependent myeloma cell line and CD40 activation blocked XG2 in the G1 phase of the cell cycle, in a manner similar to the effect of IL-6 deprivation. Daudi was blocked in the G2/M phase after treatment with the agonistic CD40 mAb 5C11. Furthermore, the activation of CD40 on Daudi and XG2 enhanced their sensitivity to dexamethasone-and gamma-irradiation -induced growth arrest and apoptosis. CD40 activation stimulated both anti-apoptotic Bcl-XL and pro-apoptotic Bax mRNA synthesis in the Daudi cell line; CD40 activation increased the Bax mRNA level but had no effect on the Bcl-XL mRNA level in the XG2 cell line. Apoptosis in both cell lines was associated with an increasing ratio of Bax-to-Bcl-XL both in mRNA and in protein levels. It is concluded that use of the anti-CD40 mAb 5C11 either by itself or in combination with chemotherapy and/or radiotherapy may have significant therapeutic potential.
authors.affiliation: Medical Biotechnology Institute, Soochow University, Suzhou, People's Republic of China.
authors.forename: Zhao-Hua
authors.initials: ZH
authors.lastname: Zhou
authors.forename: Qin
authors.initials: Q
authors.lastname: Shi
authors.forename: Jiang-Fang
authors.initials: JF
authors.lastname: Wang
authors.forename: Yong-Jing
authors.initials: YJ
authors.lastname: Chen
authors.forename: Yu-Mei
authors.initials: YM
authors.lastname: Zhuang
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Pan
authors.forename: Chang-Shao
authors.initials: CS
authors.lastname: Xu
authors.forename: Chun-Jian
authors.initials: CJ
authors.lastname: Qi
authors.forename: Xue-Guang
authors.initials: XG
authors.lastname: Zhang
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects*; D019013:CD40 Antigens / Q000276:immunology* / Q000378:metabolism; D045744:Cell Line, Tumor; D003907:Dexamethasone / Q000494:pharmacology*; D005720:Gamma Rays; D006801:Humans; D016393:Lymphoma, B-Cell / Q000378:metabolism* / Q000473:pathology; D009101:Multiple Myeloma / Q000378:metabolism* / Q000473:pathology
chemical_list: D018931:Antineoplastic Agents, Hormonal; D019013:CD40 Antigens; D003907:Dexamethasone