Donepudi Manjula, Jovasevic Vladimir M, Raychaudhuri Pradip, Mokyr Margalit B
Cancer Immunol Immunother. 2003 Mar;52(3):162-70. doi: 10.1007/s00262-002-0345-8. Epub 2003 Feb 6.
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.
我们之前已经表明，将MOPC - 315或P815肿瘤细胞暴露于广泛使用的抗癌药物美法仑（L - PAM，L - 苯丙氨酸氮芥）会导致B7 - 1表面表达迅速上调。由于表达B7 - 1的肿瘤细胞依赖于表达B7的宿主抗原呈递细胞（APC）来产生CD8(+) T细胞介导的抗肿瘤免疫，并且由于L - PAM促进来自MOPC - 315肿瘤携带者的CD8(+) T细胞获得根除肿瘤的免疫力，因此进行了当前的研究以确定L - PAM是否也上调宿主APC上的B7 - 1表达。在此我们表明，将正常脾细胞暴露于L - PAM会在24小时内导致B220(+)细胞（B细胞）上的B7 - 1表达上调。对L - PAM导致B7 - 1表达上调的机制的研究表明，在正常脾细胞暴露于L - PAM后2小时内，B7 - 1 mRNA明显积累，并且这种积累需要从头合成RNA，表明这种调节是在转录水平上。抗氧化剂N - 乙酰 - L - 半胱氨酸（NAC）可阻止L - PAM诱导的B7 - 1 mRNA积累，表明活性氧对转录调节很重要。虽然AP - 1和NF - κB被认为是氧化还原敏感的转录因子，但L - PAM仅导致NF - κB活化，该活化特异性结合到包含B7 - 1基因中相应结合位点的探针上。此外，对NF - κB活化的选择性抑制可阻止L - PAM诱导的B7 - 1 mRNA积累，表明NF - κB活化对于正常脾细胞中L - PAM诱导的B7 - 1基因表达至关重要。最后，发现对正常小鼠体内给予免疫增强剂量的L - PAM会上调其脾脏中B7 - 1 mRNA的表达。因此，L - PAM不仅上调肿瘤细胞上的B7 - 1表达，还上调宿主细胞上的B7 - 1表达的能力可能有助于L - PAM在肿瘤携带者中增强获得CD8(+) T细胞介导的根除肿瘤免疫的活性。
