Montaner Silvia, Sodhi Akrit, Ramsdell Amanda K, Martin Daniel, Hu Jiadi, Sawai Earl T, Gutkind J Silvio
Department of Diagnostic Sciences and Pathology, University of Maryland, Baltimore, USA.
Cancer Res. 2006 Jan 1;66(1):168-74. doi: 10.1158/0008-5472.CAN-05-1026.
The Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a G protein-coupled receptor (vGPCR) that has been implicated in the initiation of Kaposi's sarcoma, identifying vGPCR as an attractive target for preventing Kaposi's sarcoma. However, as only a fraction of cells in advanced Kaposi's sarcoma lesions express vGPCR, it is unclear whether this unique viral oncogene contributes to Kaposi's sarcoma progression. We therefore set out to determine whether the few cells that express vGPCR in established tumors represent an appropriate therapeutic target for the treatment of patients with preexisting Kaposi's sarcoma. To this end, we generated endothelial cell lines stably expressing vGPCR or key KSHV latently expressed proteins (vCyclin, vFlip, and LANA1). The endothelial cell line expressing vGPCR was rendered sensitive to treatment with the nucleoside analogue ganciclovir by using a bicistronic construct coexpressing the herpes simplex virus 1 thymidine kinase. S.c. injection into nude mice with mixed-cell populations formed tumors that approximate the ratio of vGPCR-expressing and KSHV latent gene-expressing cells. These mice were then treated with ganciclovir to specifically target only the vGPCR-expressing cells. Surprisingly, despite the expression of KSHV latent genes in the vast majority of tumor cells, specifically targeting only the few vGPCR-expressing cells in established tumors resulted in tumor regression. Moreover, we observed an increase in apoptosis of latent gene-expressing cells after the pharmacologic deletion of the vGPCR-expressing cells. These findings indicate that vGPCR may play a key role in Kaposi's sarcoma progression and provide experimental justification for developing molecular-based therapies specifically targeting vGPCR and its effectors for the treatment of Kaposi's sarcoma patients.
卡波西肉瘤相关疱疹病毒（KSHV）编码一种G蛋白偶联受体（vGPCR），该受体与卡波西肉瘤的起始有关，这使得vGPCR成为预防卡波西肉瘤的一个有吸引力的靶点。然而，由于在晚期卡波西肉瘤病变中只有一小部分细胞表达vGPCR，目前尚不清楚这种独特的病毒癌基因是否有助于卡波西肉瘤的进展。因此，我们着手确定在已建立的肿瘤中表达vGPCR的少数细胞是否是治疗已有卡波西肉瘤患者的合适治疗靶点。为此，我们构建了稳定表达vGPCR或关键KSHV潜伏表达蛋白（vCyclin、vFlip和LANA1）的内皮细胞系。通过使用共表达单纯疱疹病毒1胸苷激酶的双顺反子构建体，使表达vGPCR的内皮细胞系对核苷类似物更昔洛韦治疗敏感。将混合细胞群体皮下注射到裸鼠体内形成的肿瘤，其vGPCR表达细胞与KSHV潜伏基因表达细胞的比例接近实际情况。然后用更昔洛韦治疗这些小鼠，以特异性靶向仅表达vGPCR的细胞。令人惊讶的是，尽管绝大多数肿瘤细胞中都表达KSHV潜伏基因，但仅特异性靶向已建立肿瘤中少数表达vGPCR的细胞却导致肿瘤消退。此外，我们观察到在药物性清除表达vGPCR的细胞后，潜伏基因表达细胞的凋亡增加。这些发现表明，vGPCR可能在卡波西肉瘤进展中起关键作用，并为开发专门针对vGPCR及其效应器的分子疗法治疗卡波西肉瘤患者提供了实验依据。
