Objectives: To investigate the expression of B7-H3 and B7-H1 in renal angiomyolipoma (AML) tumors and the related, devastating syndrome of pulmonary lymphangioleiomyomatosis (LAM). We recently reported the high expression of T-cell co-regulatory B7-H ligands in renal cell carcinoma tumor vasculature and tumor cells. AML is a highly vascular tumor that most frequently emanates from the kidney. Events leading to its pathogenesis remain enigmatic and understudied. Methods: Immunohistochemical methods were used to assess the tumor expression of B7-H1 and B7-H3 in paraffin-embedded tissues from 110 patients who had undergone partial or radical nephrectomy for renal AML and from 7 patients with LAM who had undergone lung biopsy. Results: B7-H3 was expressed by 100% of the AML and LAM specimens, and B7-H1 expression was detected in only 2.7% of the specimens studied. Both membranous and cytoplasmic B7-H3 expression was noted in the smooth muscle, blood vessel, and lipoid cell components of the tumors; however, no expression was detected in the adjacent, normal parenchyma tissue. B7-H3 staining was noted in a median of 90% (range 20%-100%) of cells from renal AMLs and was independent of patient age (P = .43), sex (P = .27), tumor size (P = .21), and symptomatic presentation (P = .35). Conclusions: B7-H3 was expressed at high levels in renal AMLs and pulmonary LAM, and B7-H1 was infrequently expressed in these tumors. Additional studies are needed to evaluate the utility of B7-H3 as a diagnostic marker or immune/angiogenic target to improve the management of AML and the potentially devastating condition of LAM, for which effective treatment is lacking.
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