The Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) K1 protein induces expression of angiogenic and invasion factors

Wang L, Wakisaka N, Tomlinson CC, DeWire SM, Krall S, Pagano JS and Damania B
Source: Cancer Res
Publication Date: (2004)
Issue: 64(8): 2774-2781
Research Area:
Cancer Research/Cell Biology
Immunotherapy / Hematology
Cells used in publication:
Endothelial, umbilical vein, human (HUVEC)
Species: human
Tissue Origin: vein
Nucleofectorâ„¢ I/II/2b
Primary human umbilical vein endothelial cells(HUVECs) were immortalized by nucleofecting a human telomerase reverse transcriptase construct. Immortalized HUVECs were nucleofected with a vector coding for either wild-type or mutant K1 protein. The wild-type protein increased the secretion of VEGF about fourfold while the mutant K1 protein had no detectable effect. RT-PCR revealed a significant increase of mRNA of four different VEGF transcripts. Nucleofection with wild-type K1 protein also led to a sixfold enhancement of MMP-9 expression. The transfection efficiency was monitored by independent nucleofection with a GFP-encoding plasmid.
Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) has been linked to Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. In addition to endothelial cells and B lymphocytes, KSHV also has been shown to infect epithelial cells and keratinocytes. The transmembrane glycoprotein K1, encoded by the first open reading frame of KSHV, is a signaling protein capable of eliciting B-cell activation. We show that KSHV K1 can induce expression and secretion of vascular endothelial growth factor (VEGF) in epithelial and endothelial cells. Up-regulation of VEGF was mediated at the transcriptional level because expression of K1 resulted in VEGF promoter activation. We also show that K1 induces expression of matrix metalloproteinase-9 (MMP-9) in endothelial cells. Additional analyses with K1 mutant proteins revealed that the SH2 binding motifs present in the K1 cytoplasmic tail are necessary for VEGF secretion and MMP-9 induction. These results indicate that K1 signaling may contribute to KSHV-associated pathogenesis through a paracrine mechanism by promoting the secretion of VEGF and MMP-9 into the surrounding matrix.