The antiangiogenic CXC chemokines interferon γ (IFN-γ)-inducible T-cell α chemoattractant (I-TAC) and monokine induced by IFN-γ (Mig) are known as members of IFN-γ-inducible antiangiogenic CXC chemokines. However, the expression of these chemokines in highly angiogenic tumors remains poorly understood. The authors examined expression of I-TAC, Mig, and their receptor, CXCR3, in tissue samples from patients with renal cell carcinoma (RCC).
Twenty-one samples of untreated RCC and corresponding normal renal tissues were obtained from surgical specimens. The expression levels of I-TAC, Mig, and CXCR3 were investigated using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, real-time RT-PCR analysis, and Western blot analysis. Immunohistochemistry was carried out to clarify the localization of both chemokines and of CXCR3.
RT-PCR analysis showed strong expression levels of I-TAC, Mig, and CXCR3 in RCC tissues and very weak or undetectable expression in normal kidney tissues. Real-time RT-PCR analysis showed that expression levels of I-TAC, Mig, and CXCR3 in RCC tissues were 14.9 times greater, 30.3 times greater, and 9.9 times greater compared with the levels in the corresponding normal kidney tissues, respectively (P < 0.01). Western blot analysis showed up-regulation of I-TAC, Mig, and CXCR3 at the protein level. Immunofluorescence double stainings revealed that I-TAC coincided with pericytes and vascular smooth muscle cells (VSMCs) in tumor angiogenic vessels. Mig was detected in tumor endothelial cells (TECs) and in infiltrating leukocytes. In the corresponding normal kidney tissues, neither VSMCs nor endothelial cells showed positive stainings for these chemokines. CXCR3 was expressed in both tumor cells and infiltrating leukocytes.
The results revealed special feature of vascular mural cells and TECs in RCC. The up-regulated I-TAC and Mig, produced by tumor vessels, may interact with CXCR3 expressed in tumor cells, with possible pathophysiologic significance in RCC progression. Cancer 2005. © 2004 American Cancer Society.