RESUMO
Recent studies have suggested that BK polyomavirus (BKPyV) may be associated with the development of urothelial carcinoma. In Merkel cell carcinoma, TAg and tAg are the major viral proteins of Merkel cell polyomavirus with oncogenic potential. In this study, we aimed to distinguish the role of TAg and tAg in cell migration. Our result demonstrated that ERK was phosphorylated in human renal tubular cells expressing its TAg and tAg after BKPyV infection. Treatment with the ERK inhibitor U0126 suppressed BKPyV gene expression and reduced BKPyV replication. Both TAg and tAg induced cell migration via ERK-dependent signaling. Furthermore, the expression of TAg and tAg had a significant regulatory effect on focal adhesion molecules in renal proximal tubular cells, which strongly suggests that alterations in the focal adhesion complexes are critically involved in TAg and tAg-induced cell migration. Gelatin zymography profiling revealed that TAg regulates the expression and activity of MMP-2 and MMP-9, but not tAg. Interestingly, TAg regulates the expression and activity of MMP-9 through ERK signaling, whereas MMP-2 is regulated through an ERK-independent pathway. Unbalanced ERK pathway activity is frequently observed in many cancers, while MMP proteins are usually overexpressed in aggressive tumors. These findings support the view that BKPyV is an oncogenic virus.
RESUMO
PURPOSE: BK Polyomavirus (BKPyV) infection manifests as renal inflammation and can cause kidney damage. Tumor necrosis factor-α (TNF-α) is increased in renal inflammation and injury. The aim of this study was to investigate the effect of TNF-α blockade on BKPyV infection. METHODS: Urine specimens from 22 patients with BKPyV-associated nephropathy (BKPyVN) and 35 non-BKPyVN kidney transplant recipients were analyzed. RESULTS: We demonstrated increased urinary levels of TNF-α and its receptors, TNFR1 and TNFR2, in BKPyVN patients. Treating BKPyV-infected human proximal tubular cells (HRPTECs) with TNF-α stimulated the expression of large T antigen and viral capsid protein-1 mRNA and proteins and BKPyV promoter activity. Knockdown of TNFR1 or TNFR2 expression caused a reduction in TNF-α-stimulated viral replication. NF-κB activation induced by overexpression of constitutively active IKK2 significantly increased viral replication and the activity of the BKPyV promoter containing an NF-κB binding site. The addition of a NF-κB inhibitor on BKPyV-infected cells suppressed viral replication. Blockade of TNF-α functionality by etanercept reduced BKPyV-stimulated expression of TNF-α, interleukin-1ß (IL-1ß), IL-6 and IL-8 and suppressed TNF-α-stimulated viral replication. In cultured HRPTECs and THP-1 cells, BKPyV infection led to increased expression of TNF-α, interleukin-1 ß (IL-1ß), IL-6 and TNFR1 and TNFR2 but the stimulated magnitude was far less than that induced by poly(I:C). This may suggest that BKPyV-mediated autocrine effect is not a major source of TNFα. CONCLUSION: TNF-α stimulates BKPyV replication and inhibition of its signal cascade or functionality attenuates its stimulatory effect. Our study provides a therapeutic anti-BKPyV target.
