Increased Frequency and Vasculogenic Potential of Endothelial Colony-Forming Cells in Patients with Kaposi’s Sarcoma

Abstract

Kaposi's sarcoma (KS) is characterized by hyperproliferation of spindle cells that have an endothelial origin and assume their characteristic features upon infection with human herpesvirus-8, the causative agent for KS. The multifocal nature of KS suggests that spindle cells derive from circulating HHV8-infected precursors that yet lack identification. We investigated whether endothelial colony-forming cells (ECFCs) obtained from KS patients may be putative precursors of spindle cells by assessing whether their in vitro behavior may evoke the in vivo behavior of KS spindle cells. We isolated and cultured ECFCs from the blood of 83 patients with classic KS and compared them with ECFCs obtained from 86 healthy donors. ECFCs were highly increased in the blood of classic KS patients; they showed higher proliferative and vasculogenic potential and higher production of IL-6 than control ECFCs. Similarly to spindle cells in KS lesions, a variable proportion of cells within each ECFC colony expressed the human herpesvirus-8 latency-associated nuclear antigen. ECFCs obtained from classic KS patients evoked KS spindle cell behavior, thus supporting the hypothesis that ECFCs may be putative precursors of spindle cells. ECFCs can therefore represent a noninvasive tool for studying KS and screening drug activity, thus possibly guiding personalized care for KS patients.

Enhanced phosphorylation of sphingosine and ceramide sustains the exuberant proliferation of endothelial progenitors in Kaposi sarcoma

“…The patients had histologically confirmed diagnosis of cKS, were positive for anti‐HHV8 antibody, negative for HIV, and were not in systemic chemotherapy. Their KS stage at the time of blood withdrawal was 1A, 1B, and 3B, respectively, according to our classification that takes into account the prevalent type of lesions, localization, evolutive pattern (A and B, indicating slowly and rapidly evolving disease), and presence of complications . Neither cKS patients nor controls had suffered from chronic inflammatory, autoimmune, and cancer disease other than KS, nor they had clinically evident infections.…”

“…Isolation and culture of ECFCs were performed on fresh peripheral blood samples. ECFCs were isolated and cultured from PBMCs essentially as previously described . Briefly, PBMCs, obtained by Ficoll density gradient centrifugation (Cedarlane, Hornby, Canada), were resuspended in EGM‐2 medium (Lonza Inc., Allendale, NJ, USA) and seeded onto 24‐well tissue culture plates previously coated with human fibronectin (Sigma‐Aldrich, St. Louis, MO, USA).…”

“…Their KS stage at the time of blood withdrawal was 1A, 1B, and 3B, respectively, according to our classification that takes into account the prevalent type of lesions, localization, evolutive pattern (A and B, indicating slowly and rapidly evolving disease), and presence of complications. 8,[14][15][16] Neither cKS patients nor controls had suffered from chronic inflammatory, autoimmune, and cancer disease other than KS, nor they had clinically evident infections. They were not under treatment with drugs that have been reported to affect the number and function of endothelial progenitor cells (including statins, angiotensin-converting enzyme inhibitors, calcium antagonists, and metformin).…”

“…Accordingly, endothelial colony‐forming cells (ECFCs), a unique endothelial stem cell population that can be isolated from the blood and is endowed with typical endothelial phenotype, clonal proliferative potential, and ability to perform angiogenesis and vasculogenesis in vivo, are HHV8 infected in KS patients . Moreover, we recently demonstrated that the frequency of circulating ECFCs was markedly higher in KS patients compared with healthy donors, and that ECFCs from KS patients showed a higher proliferative and vasculogenic potential and increased cytokine production compared with control ECFCs . Notwithstanding, emerging studies indicate that ECFCs from KS patients evoke the in vivo behavior of KS spindle cells, and may represent their precursors and potential virus reservoirs, little is known on the signaling mediators responsible for their proliferative properties.…”

“…7 Moreover, we recently demonstrated that the frequency of circulating ECFCs was markedly higher in KS patients compared with healthy donors, and that ECFCs from KS patients showed a higher proliferative and vasculogenic potential and increased cytokine production compared with control ECFCs. 8 Notwithstanding, emerging studies indicate that ECFCs from KS patients evoke the in vivo behavior of KS spindle cells, and may represent their precursors and potential virus reservoirs, little is known on the signaling mediators responsible for their proliferative properties.…”