Melphalan-induced up-regulation of B7-1 surface expression on normal splenic B cells.
We have previously shown that exposure of MOPC-315 or P815 tumor cells to the widely used anticancer drug melphalan ( L-PAM, L-phenylalanine mustard) leads to rapid up-regulation of B7-1 surface expression. Since B7-1-expressing tumor cells depend on B7-expressing host antigen presenting cells (APC) for the generation of CD8(+) T-cell-mediated antitumor immunity, and since L-PAM promotes the acquisition of tumor-eradicating immunity by CD8(+) T-cells from MOPC-315 tumor bearers, the current studies were undertaken to determine if L-PAM also up-regulates B7-1 expression on host APC. Here we show that exposure of normal spleen cells to L-PAM leads within 24 h to up-regulated B7-1 expression on B220(+) cells (B cells). Studies into the mechanism through which L-PAM leads to up-regulated B7-1 expression revealed that within 2 h after exposure of normal spleen cells to L-PAM, accumulation of B7-1 mRNA is evident and this accumulation requires de novo RNA synthesis, indicating that the regulation is at the transcriptional level. The L-PAM-induced accumulation of B7-1 mRNA was prevented with the antioxidant N-acetyl- L-cysteine (NAC), indicating that reactive oxygen species are important for the transcriptional regulation. Although AP-1 and NF-kappa B are considered redox-sensitive transcription factors, L-PAM led only to activation of NF-kappa B that bound specifically to a probe containing the corresponding binding site in the B7-1 gene. Moreover, selective inhibition of NF-kappa B activation prevented the L-PAM-induced B7-1 mRNA accumulation, indicating that NF-kappa B activation is essential for L-PAM-induced B7-1 gene expression in normal spleen cells. Finally, in vivo administration of an immunopotentiating dose of L-PAM to normal mice was found to up-regulate B7-1 mRNA expression in their spleens. Thus, the ability of L-PAM to up-regulate B7-1 expression not only on tumor cells but also on host cells may contribute to the potentiating activity of L-PAM for the acquisition of CD8(+) T-cell-mediated tumor-eradicating immunity in tumor bearers.
Donepudi
Manjula
M
Jovasevic
Vladimir M
VM
Raychaudhuri
Pradip
P
Mokyr
Margalit B
MB
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D001402:B-Lymphocytes / Q000378:metabolism*; D018122:B7-1 Antigen / Q000096:biosynthesis*; D001665:Binding Sites; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D005434:Flow Cytometry; D008558:Melphalan / Q000494:pharmacology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D010084:Oxidation-Reduction; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000166:cytology* / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015854:Up-Regulation
D018906:Antineoplastic Agents, Alkylating; D000975:Antioxidants; D018122:B7-1 Antigen; D016328:NF-kappa B; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D003609:Dactinomycin; D008558:Melphalan