CRISPR/RfxCas13d guide RNAs used in this study.

KSHV has not been found to transform human B cells alone. We show now it infects both peripheral and tonsillar B cells inefficiently and cooperates with EBV to co-transform a similar, small fraction of cells from both sources. These cells yield immortalized progeny, one hallmark of transformation, and depend on both viruses for their continued growth. The cells secrete multiple cytokines that support their paracrine growth and express viral genes that mediate expression of these cytokines. The co-transformed cells grow preferentially as tumors in the peritoneal cavities of NSG mice outgrowing B cells transformed only by EBV. The levels of EBV genes expressed in co-transformed cells decrease during growth in vitro and more so during tumor growth in vivo while those of KSHV increase, mirroring that found In Primary Effusion Lymphoma (PEL) derived cell lines. The expression of cellular genes changes too, to reflect that of PEL biopsies. Both KSHV and EBV oncogenes are expressed in the co-transformed cells that regulate the gene signature of PELs, making these co-transformed cells a tractable model with which to understand this unique lymphoma associated with these two tumor viruses. Studies of this model will also illuminate the individual contributions of each virus to the many cancers they cause.

迄今尚未发现卡波西肉瘤相关疱疹病毒（Kaposi's Sarcoma-Associated Herpesvirus, KSHV）可单独转化人类B细胞。本研究证实，该病毒低效感染外周血及扁桃体来源的B细胞，并与EB病毒（Epstein-Barr Virus, EBV）协同，从两种来源的细胞中共同转化出占比相似的少量细胞群。此类细胞可产生永生化子代，这是细胞转化的标志性特征之一，且其持续增殖依赖于两种病毒的共同作用。该类细胞会分泌多种细胞因子以支持自身的旁分泌增殖，并表达介导此类细胞因子表达的病毒基因。共同转化的细胞优先在NSG小鼠的腹腔内形成肿瘤，其生长速度超过仅被EB病毒转化的B细胞。共同转化细胞中EB病毒基因的表达水平在体外培养过程中逐渐降低，在体内成瘤阶段下降更为显著；而KSHV基因的表达水平则呈上升趋势，这与原发性渗出性淋巴瘤（Primary Effusion Lymphoma, PEL）细胞系中的表达模式一致。细胞内基因的表达谱同样发生改变，其特征与PEL患者活检组织的基因表达谱相符。卡波西肉瘤相关疱疹病毒与EB病毒的癌基因均在共同转化细胞中表达，这些癌基因可调控PEL的基因表达特征，使得此类共同转化细胞成为研究这两种肿瘤病毒相关独特淋巴瘤的可操作模型。依托该模型开展的研究，还可阐明两种病毒各自在其所引发的多种肿瘤中所发挥的作用。