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

Abstract

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.

Viral and cellular N6-methyladenosine and N6,2′-O-dimethyladenosine epitranscriptomes in the KSHV life cycle

“…However, it was obvious that KMSC and KMM cells shared more common 5′UTR hypomethylated pathways compared to KiSLK cells. KMSC and KMM are primary cells transformed by KSHV, which are excellent models for studying KSHV-induced oncogenesis 36,37 . Indeed, the top 5′UTR hypomethylated and 3′UTR hypermethylated pathways in both KMM vs MM and KMSC vs MSC were broadly related to oncogenic/mitogenic signaling, cytoskeleton and extracellular signaling, endocytosis, loss of contact inhibition, remodeling of adherens junction, and cellular adhesion/invasion, all of which have been implicated in KSHV latency and cellular transformation (Fig.…”

“…Of these genes, numerous pathways implicated in cellular transformation are enriched. In particular, the epithelial-mesenchymal transition (EMT) process is critical for embryogenesis and wound healing; however, KS and other cancer cells have hijacked this process to promote tumor growth, invasion, vascular extravasation, and metastasis 36,37,46 . EMT can be induced by various stimuli including growth factors and oncogenic signaling 46,47 .…”

“…KiSLK cells derived from iSLK cells by infection with a recombinant KSHV BAC16 34 were grown as iSLK cells except that the medium also contained 1.2 mg/ml hygromycin B. BCBL1-R, a KSHV-infected PEL cell line BCBL1 stably expressing doxycycline-inducible RTA, was grown in RPMI1640 supplemented with 10% FBS, 1% penicillin-streptomycin, and 20 μg/ml hygromycin B 35 . MSC cells, which are primary human adipose tissue-derived mesenchymal stem cells, were cultured in MSC medium (ScienCell Research Laboratories, Carlsbad, CA) containing 20% FBS as previously described 37 . KMSC cells derived from MSC cells by infection and transformation with BAC36 32,37 were cultured in the same media with the addition of 100 μg/ml hygromycin B.…”

An APE1 inhibitor reveals critical roles of the redox function of APE1 in KSHV replication and pathogenic phenotypes

“…Although the nature and cellular origin of KS cells remains contentious, KSHV infection of both endothelial cells and mesenchymal stem cells (MSCs) confer the cells with certain KS features including angiogenic, invasive and transformation phenotypes [37,38]. When human MSCs from periodontal ligament (PDLSC) were infected with KSHV, increased angiogenesis activity was shown in an in vitro Matrigel tubulogenesis assay (Fig 2B).…”

Kaposi sarcoma–associated herpesvirus: immunobiology, oncogenesis, and therapy

“…KSHV provides a growth advantage to infected endothelial cells. The virus consistently immortalizes, but rarely transforms, primary cells in culture (15)(16)(17)(18)(19). It is only under special circumstances and perhaps upon infection of rare progenitor cells with stem cell properties that the interplay between virus and host leads to a fully transformed state.…”