Primary Effusion Lymphoma

Researchers have discovered a key mechanism used by Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8), to induce cancer. The research points to effective new treatment options for KSHV-associated cancers, including Kaposi's sarcoma, primary effusion lymphoma, and HHV8-associated multicentric Castleman disease. Cleveland Clinic researchers have discovered a key mechanism used by Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8), to induce cancer. The research points to effective new treatment options for KSHV-associated cancers, including Kaposi's sarcoma, primary effusion lymphoma, and HHV8-associated multicentric Castleman disease. "Our findings have significant implications: viruses cause between 10% to 20% of cancers worldwide, a number that is constantly increasing as new discoveries are made. Treating virus-induced cancers with standard cancer therapies can help shrink tumors that are already there, but it doesn't fix the underlying problem of the virus," said Jun Zhao, Ph.D., of Cleveland Clinic Florida Research & Innovation Center. "Understanding how pathogens transform a healthy cell into a cancer cell uncovers exploitable vulnerabilities and allows us to make and repurpose existing drugs that can effectively treat virus-associated malignancies." The Nature Communicationsstudy, led by Dr. Zhao, reveals that KSHV manipulates two human enzymes called CDK6 and CAD to reshape the way human cells produce new nucleotides -- the building blocks of DNA and RNA -- and process glucose. The changes to how infected cells grow and how KSHV persists put cells at a much higher risk of forming tumors and play a crucial role in causing cancer. The team showed the virus activates a specific pathway driving cell metabolism and proliferation. Inhibiting this process with existing FDA-approved breast cancer drugs reduced KSHV replication, blocked lymphoma progression and shrunk existing tumors in preclinical models. Like other herpesviruses, KSHV often has no symptoms initially and remains in the body after primary infection. The virus stays dormant, suppressed by the immune system. However, KSHV can reactivate when immunity is weakened -- as in older people, those with HIV/AIDS, and transplant recipients. In these high-risk groups, the now active virus can trigger aggressive cancers. KSHV-induced cancers are fast-acting, aggressive and difficult to treat. An estimated 10% of people in North America and Northern Europe have KSHV, but this ranges throughout the globe. More than 50% of individuals in parts of Northen Africa are estimated to have the virus. Experts estimate these rates are higher, as KSHV often goes undiagnosed because of lack of symptoms. These findings have implications that reach past KSHV; researchers can apply knowledge about KSHV to other cancer-associated viruses that might use the same process to cause cancer. To understand the cells' metabolic processes to uncover the virus's vulnerabilities, Dr. Zhao collaborated with Michaela Gack, Ph.D., Scientific Director of the Florida Research & Innovation Center. Rapidly replicating cancer cells reprogram metabolism to fuel growth. Meanwhile, most viruses cannot produce energy or necessary molecules on their own, so they rely on human cells to do the work for them. The team found that the virus takes over the host protein CDK6 and CAD, causing the infected cells to produce extra metabolites, which allows faster replication of the virus and an uncontrolled proliferation of the cells. The research team treated pre-clinical models with a CDK6-blocking drug, Palbociclib, an FDA-approved breast cancer medication, as well as a compound targeting CAD. They saw significant decreases in tumor size and increases in cancer survival rates: most tumors virtually disappeared after about a month of treatment, and remaining tumors shrank around 80%. Survival increased to 100% for selected lymphoma cell lines. Dr. Zhao and his team are working to better understand the connections among KSHV, CDK6/CAD pathway, and cancer formation. With the knowledge they obtain, they plan to implement and refine their experimental drug combinations for clinical trials. "Cellular metabolism could be hijacked by both viruses and cancers for pathogenesis," said Dr. Zhao. "By investigating these metabolic rewiring mechanisms, we aim to find the Achilles' heel of cancer-causing viruses and non-viral cancers. I'm excited to see what the future of this work holds."

2024年1月12日，武汉大学病毒学国家重点实验室张军杰教授课题组在国际学术期刊PLOS Pathogens上在线发表题为“Non-canonical regulation of the reactivation of an oncogenic herpesvirus by the OTUD4-USP7 deubiquitinases”的研究论文，揭示了去泛素化酶复合体OTUD4-USP7在肿瘤疱疹病毒裂解再激活中发挥的关键作用。卡波氏肉瘤相关疱疹病毒(KSHV)是一种人类肿瘤疱疹病毒，其感染可引起卡波氏肉瘤、原发性渗出性淋巴瘤等多种恶性肿瘤。KSHV的生命周期分为潜伏感染和裂解复制，从潜伏感染到裂解复制的转换过程称为裂解再激活，这一过程在病毒复制及引起肿瘤发生都发挥了关键作用。KSHV 病毒基因ORF50编码的病毒蛋白RTA在裂解再激活中发挥分子开关的作用。此前的研究表明RTA的稳定性受到泛素化修饰调控，然而去泛素化是否调控RTA及KSHV裂解再激活尚不明确。在该研究中，作者们通过串联亲和纯化鉴定RTA的结合蛋白，发现去泛素化酶OTUD4与RTA相互作用。进一步研究表明，OTUD4能够导致RTA去泛素化从而稳定RTA，促进KSHV裂解再激活。令人意外的是，OTUD4丧失去泛素化酶活性的突变体同样能导致RTA去泛素化并稳定RTA，提示OTUD4可能扮演了接头蛋白的角色，通过结合另外一个去泛素化酶发挥作用。作者们筛选了OTUD4结合的去泛素化酶，发现去泛素化酶USP7与OTUD4结合，实验证实USP7也在KSHV裂解再激活中发挥了关键作用。进一步的研究证实RTA通过结合OTUD4进而招募USP7，USP7直接去泛素化RTA，从而稳定RTA，促进病毒复制。该研究不仅揭示了肿瘤疱疹病毒KSHV通过劫持OTUD4-USP7去泛素化酶复合体促进裂解再激活的机制，也为治疗相关感染引发的恶性肿瘤提供了新的靶点。武汉大学医学研究院/免疫与代谢前沿科学中心/病毒学国家重点实验室张军杰教授为该论文的通讯作者，医学研究院2022级博士研究生王绍伟为该论文的第一作者，武汉大学口腔医学院和医学研究院联合培养博士后田学张为并列第一作者。该研究的合作者包括武汉大学病毒学国家重点实验室蓝柯教授和白磊博士，武汉大学医学研究院钟波教授和于可颖博士，武汉大学人民医院林丹丹教授，汕头大学覃青松教授及美国南加州大学Pinghui Feng教授。研究获得国家重点研发计划、国家自然科学基金、中央高校基本科研业务费专项资金及病毒学国家重点实验室自主科研项目等资助。示意图：KSHV RTA招募OTUD4-USP7复合体去泛素化稳定RTA，促进病毒复制。论文链接：https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1011943识别微信二维码，添加生物制品圈小编，符合条件者即可加入生物制品微信群！请注明：姓名+研究方向！版权声明本公众号所有转载文章系出于传递更多信息之目的，且明确注明来源和作者，不希望被转载的媒体或个人可与我们联系(cbplib@163.com)，我们将立即进行删除处理。所有文章仅代表作者观点，不代表本站立场。