Kaposi’s sarcoma-associated herpesvirus infection of human bone-marrow-derived mesenchymal stem cells and their angiogenic potential

Unveiling the role of KSHV-infected human mesenchymal stem cells in Kaposi's sarcoma initiation

Kaposi's sarcoma (KS) may derive from Kaposi's sarcoma herpesvirus (KSHV)-infected human mesenchymal stem cells (hMSCs) that migrate to sites characterized by inflammation and angiogenesis, promoting the initiation of KS. By analyzing the RNA sequences of KSHV-infected primary hMSCs, we have identified specific cell subpopulations, mechanisms, and conditions involved in the initial stages of KSHV-induced transformation and reprogramming of hMSCs into KS progenitor cells. Under proangiogenic environmental conditions, KSHV can reprogram hMSCs to exhibit gene expression profiles more similar to KS tumors, activating cell cycle progression, cytokine signaling pathways, endothelial differentiation, and upregulating KSHV oncogenes indicating the involvement of KSHV infection in inducing the mesenchymal-to-endothelial (MEndT) transition of hMSCs. This finding underscores the significance of this condition in facilitating KSHV-induced proliferation and reprogramming of hMSCs towards MEndT and closer to KS gene expression profiles, providing further evidence of these cell subpopulations as precursors of KS cells that thrive in a proangiogenic environment.

The Kaposi's sarcoma progenitor enigma: KSHV-induced MEndT-EndMT axis

Endothelial-to-mesenchymal transition has been described in tumors as a source of mesenchymal stroma, while the reverse process has been proposed in tumor vasculogenesis and angiogenesis. A human oncogenic virus, Kaposi's sarcoma herpes virus (KSHV), can regulate both processes in order to transit through this transition 'boulevard' when infecting KS oncogenic progenitor cells. Endothelial or mesenchymal circulating progenitor cells can serve as KS oncogenic progenitors recruited by inflammatory cytokines because KSHV can reprogram one into the other through endothelial-to-mesenchymal and mesenchymal-to-endothelial transitions. Through these novel insights, the identity of the potential oncogenic progenitor of KS is revealed while gaining knowledge of the biology of the mesenchymal-endothelial differentiation axis and pointing to this axis as a therapeutic target in KS.

Kaposi's sarcoma-associated herpesvirus at 27

Kaposi's sarcoma-associated herpesvirus (KSHV) was discovered 27 years ago and its link to several pathologies - Kaposi's sarcoma, primary effusion lymphoma, and the B cell variant of Multicentric Castleman disease - is now well established. However, many questions remain about how KSHV causes tumors. Here, I will review studies from the last few years (primarily 2019-2021) that report new information about KSHV biology and tumorigenesis, including new results about KSHV proteins implicated in tumorigenesis, genetic and environmental variability in KSHV-related tumor development, and potential vulnerabilities of KSHV-caused tumors that could be novel therapeutic targets.

PDGFRA defines the mesenchymal stem cell Kaposi's sarcoma progenitors by enabling KSHV oncogenesis in an angiogenic environment

Kaposi's sarcoma (KS) is an AIDS-defining cancer caused by the KS-associated herpesvirus (KSHV). Unanswered questions regarding KS are its cellular ontology and the conditions conducive to viral oncogenesis. We identify PDGFRA(+)/SCA-1(+) bone marrow-derived mesenchymal stem cells (Pα(+)S MSCs) as KS spindle-cell progenitors and found that pro-angiogenic environmental conditions typical of KS are critical for KSHV sarcomagenesis. This is because growth in KS-like conditions generates a de-repressed KSHV epigenome allowing oncogenic KSHV gene expression in infected Pα(+)S MSCs. Furthermore, these growth conditions allow KSHV-infected Pα(+)S MSCs to overcome KSHV-driven oncogene-induced senescence and cell cycle arrest via a PDGFRA-signaling mechanism; thus identifying PDGFRA not only as a phenotypic determinant for KS-progenitors but also as a critical enabler for viral oncogenesis.

Evidence for Kaposi Sarcoma Originating from Mesenchymal Stem Cell through KSHV-induced Mesenchymal-to-Endothelial Transition

The major transmission route for Kaposi sarcoma-associated herpesvirus (KSHV) infection is the oral cavity through saliva. Kaposi sarcoma (KS) frequently occurs in the oral cavity in HIV-positive individuals and is often the first presenting sign of AIDS. However, the oral target cells for KSHV infection and the cellular origin of Kaposi sarcoma remain unknown. Here we present clinical and experimental evidences that Kaposi sarcoma spindle cells may originate from virally modified oral mesenchymal stem cells (MSC). AIDS-KS spindle cells expressed neuroectodermal stem cell marker (Nestin) and oral MSC marker CD29, suggesting an oral/craniofacial MSC lineage of AIDS-associated Kaposi sarcoma. Furthermore, oral MSCs were highly susceptible to KSHV infection, and infection promoted multilineage differentiation and mesenchymal-to-endothelial transition (MEndT). KSHV infection of oral MSCs resulted in expression of a large number of cytokines, a characteristic of Kaposi sarcoma, and upregulation of Kaposi sarcoma signature and MEndT-associated genes. These results suggest that Kaposi sarcoma may originate from pluripotent MSC and KSHV infection transforms MSC to Kaposi sarcoma-like cells through MEndT.Significance: These findings indicate that Kaposi sarcomas, which arise frequently in AIDS patients, originate from neural crest-derived mesenchymal stem cells, with possible implications for improving the clnical treatment of this malignancy. Cancer Res; 78(1); 230-45. ©2017 AACR.

Infection of KSHV and Interaction with HIV: The Bad Romance

Kaposi's sarcoma-associated herpesvirus (KSHV), namely, human herpesvirus 8 (HHV-8), is considered as the pathogen of Kaposi's sarcoma (KS), the most frequent cancer in untreated HIV-infected individuals. Patients infected with HIV have a much higher possibility developing KS than average individual. Researchers have found that HIV, which functions as a cofactor of KS, contributes a lot to the development of KS. In this article, we will give a brief introduction of KS and KSHV and how the interaction between KSHV and HIV contributes to the development of KS. Also we will take a glance at the development of treatment in KS, especially AIDS-KS.

Latent Kaposi's sarcoma-associated herpesvirus infection in bladder cancer cells promotes drug resistance by reducing reactive oxygen species

Kaposi's sarcoma-associated herpesvirus (KSHV) is the major etiologic agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. Recent studies have indicated that KSHV can be detected at high frequency in patient-derived bladder cancer tissue and might be associated with the pathogenesis of bladder cancer. Bladder cancer is the second most common cancer of the genitourinary tract, and it has a high rate of recurrence. Because drug resistance is closely related to chemotherapy failure and cancer recurrence, we investigated whether KSHV infection is associated with drug resistance of bladder cancer cells. Some KSHV-infected bladder cancer cell lines showed resistance to an anti-cancer drug, cisplatin, possibly as a result of down-regulation of reactive oxygen species. Additionally, drug resistance acquired from KSHV infection could partly be overcome by HDAC1 inhibitors. Taken together, the data suggest the possible role of KSHV in chemo-resistant bladder cancer, and indicate the therapeutic potential of HDAC1 inhibitors in drug-resistant bladder cancers associated with KSHV infection.

Human Mesenchymal Stem Cells of Diverse Origins Support Persistent Infection with Kaposi's Sarcoma-Associated Herpesvirus and Manifest Distinct Angiogenic, Invasive, and Transforming Phenotypes

Kaposi's sarcoma (KS), a highly angiogenic and invasive tumor often involving different organ sites, including the oral cavity, is caused by infection with Kaposi's sarcoma-associated herpesvirus (KSHV). Diverse cell markers have been identified on KS tumor cells, but their origin remains an enigma. We previously showed that KSHV could efficiently infect, transform, and reprogram rat primary mesenchymal stem cells (MSCs) into KS-like tumor cells. In this study, we showed that human primary MSCs derived from diverse organs, including bone marrow (MSCbm), adipose tissue (MSCa), dental pulp, gingiva tissue (GMSC), and exfoliated deciduous teeth, were permissive to KSHV infection. We successfully established long-term cultures of KSHV-infected MSCa, MSCbm, and GMSC (LTC-KMSCs). While LTC-KMSCs had lower proliferation rates than the uninfected cells, they expressed mixtures of KS markers and displayed differential angiogenic, invasive, and transforming phenotypes. Genetic analysis identified KSHV-derived microRNAs that mediated KSHV-induced angiogenic activity by activating the AKT pathway. These results indicated that human MSCs could be the KSHV target cells in vivo and established valid models for delineating the mechanism of KSHV infection, replication, and malignant transformation in biologically relevant cell types.

IMPORTANCE

Kaposi's sarcoma is the most common cancer in AIDS patients. While KSHV infection is required for the development of Kaposi's sarcoma, the origin of KSHV target cells remains unclear. We show that KSHV can efficiently infect human primary mesenchymal stem cells of diverse origins and reprogram them to acquire various degrees of Kaposi's sarcoma-like cell makers and angiogenic, invasive, and transforming phenotypes. These results indicate that human mesenchymal stem cells might be the KSHV target cells and establish models for delineating the mechanism of KSHV-induced malignant transformation.