Towards an improved Kaposi sarcoma immunotherapy: Investigating the interplay of the oncogenic Kaposi sarcoma herpesvirus G-protein coupled receptor with the host chemokine system

Anna Grosskopf, Ph.D.,  National Cancer Institute, Center for Cancer Research
Recipient of the: $50,000 Sarcoma Foundation of America Research Award

Kaposi sarcoma (KS) is a highly vascularized tumor of the skin and viscera that is driven by the oncogenic Kaposi Sarcoma Herpesvirus (KSHV). Skin KS can cause painful edema while visceral KS of the lungs or gastrointestinal tract has the highest rates of mortality. KS manifests most frequently in the context of immune suppression, including transplant recipients and people living with HIV. In sub-Saharan Africa, where KSHV is endemic, KS is a major cause of cancer mortality in men. Therapeutic approaches use toxic chemotherapy or broad immune activation, but KS often recurs. There are no treatments that target KSHV-specific molecules. Immunotherapy that targets the chemokine system relies on a detailed knowledge of the expression and role of these immune modulators in specific cancer types. For KS, the role of the chemokine system is not well-established. Of note, KSHV encodes a viral chemokine receptor (vGPCR) that is defined as an oncogene. The vGPCR drives tumors in mice and responds to human chemokines. The goal of this study is to use RNAseq OMICS approaches to define the chemokine profile of KS and analyze how these chemokines influence vGPCR signaling. Understanding the molecular mechanisms that regulate vGPCR function and drive KS development will identify potential targets for KS-directed therapy. To identify chemokines dysregulated in KS patients, I used bioinformatics to analyze two independent RNAseq datasets of KS skin tumors compared to normal skin. Based on our preliminary data, the first part of our project will focus on the impact of these chemokines on vGPCR-dependent transcriptional changes. All analysis will be conducted in lymphatic endothelial cells and B cells, two cell types central to KSHV-associated diseases. RNA sequencing of cells expressing wild type or mutant vGPCR will allow us to differentiate constitutive receptor activity from chemokine-induced responses. We expect to identify key chemokines and novel vGPCR target genes in pathways that inform KS oncogenic processes including angiogenesis, cell proliferation and survival. In the second part of this project, endothelial and B cell infection models will be used for functional studies to validate the key pathways and target genes regulated by the vGPCR. A specific focus will be placed on the chemokine system and key features of KS such as cell proliferation and blood vessel formation. A murine gammaherpesvirus that is closely related to KSHV will be engineered to express the KSHV vGPCR and used to validate vGPCR-specific contributions in the context of infection. This project will advance the sarcoma field by elucidating how a viral chemokine receptor hijacked from the host can drive a virus-induced sarcoma. RNAseq discovery validated by functional assays will not only define how chemokines in the tumor microenvironment regulate vGPCR-signaling that promotes KS, but also identify chemokines that regulate vGPCR as potential targets for immunomodulatory therapy.