Immunohistochemical expression of hypoxia inducible factor-1alpha and its downstream molecules in sarcomatoid renal cell carcinoma

PURPOSE: Sarcomatoid renal cell carcinomas, highly aggressive variants of renal cell carcinoma subtypes, often present with or develop metastases soon after the primary diagnosis. Most metastatic cases do not respond to immunotherapy or aggressive chemotherapy. Recently targeted therapies, particularly those targeting hypoxia inducible pathway molecules, have been tested clinically on metastatic clear cell renal cell carcinoma with promising initial results. No such studies are available on sarcomatoid renal cell carcinoma. We investigated the hypoxia inducible pathway marker immunohistochemical expression profile, and any potential therapeutic implications that such expression may have, in these tumors. MATERIALS AND METHODS: Immunohistochemical staining for hypoxia inducible factor-1alpha, glucose transporter 1, carbonic anhydrase IX and vascular endothelial growth factor was performed in 22 clear cell and 12 nonclear cell sarcomatoid renal cell carcinomas. The immunoreactivity in the tumors was graded from 0 to 3+ (0-no staining, 1+-1% to 25% cells positive, 2+-26% to 50% cells positive and 3+-greater than 50% cells positive). The results were then compared with various clinical parameters to assess for associations. RESULTS: Most clear cell renal cell carcinomas over expressed (2+ or 3+) hypoxia inducible factor-1alpha (in 59%), carbonic anhydrase IX (95%), glucose transporter 1 (91%) and vascular endothelial growth factor (95%). None of the nonclear cell sarcomatoid renal cell carcinomas showed 2+ or 3+ expression of hypoxia inducible factor-1alpha, carbonic anhydrase IX or glucose transporter 1, but 92% showed diffuse positivity for vascular endothelial growth factor. Over expression of carbonic anhydrase IX showed no association with survival, unlike that reported in (nonsarcomatoid) clear cell renal cell carcinoma. There was significant discordance in the staining grades among hypoxia inducible factor-1alpha, carbonic anhydrase IX and glucose transporter 1 in clear cell renal cell carcinoma, suggesting that mechanisms other than hypoxia inducible pathway may be involved in some sarcomatoid clear cell renal cell carcinoma. CONCLUSIONS: Hypoxia inducible pathway markers continue to be over expressed in sarcomatoid clear cell renal cell carcinoma, and can be of diagnostic usefulness in such high grade tumors. Over expression of vascular endothelial growth factor in the clear and nonclear cell groups raises the possibility that vascular endothelial growth factor targeted therapies may have a role in the management of sarcomatoid renal cell carcinoma, and deserve further investigation.