Evaluating Established Roles, Future Perspectives and Methodological Heterogeneity for Wilms' Tumor 1 (WT1) Antigen Detection in Adult Renal Cell Carcinoma, Using a Novel N-Terminus Targeted Antibody (Clone WT49)

Abstract

Renal cell carcinoma (RCC) is arguably the deadliest form of genitourinary malignancy and is nowadays viewed as a heterogeneous series of cancers, with the same origin but fundamentally different metabolisms and clinical behaviors. Immunohistochemistry (IHC) is increasingly necessary for RCC subtyping and definitive diagnosis. WT1 is a complex gene involved in carcinogenesis. To address reporting heterogeneity and WT1 IHC standardization, we used a recent N-terminus targeted monoclonal antibody (clone WT49) to evaluate WT1 protein expression in 56 adult RCC (aRCC) cases. This is the largest WT1 IHC investigation focusing exclusively on aRCCs and the first report on clone WT49 staining in aRCCs. We found seven (12.5%) positive cases, all clear cell RCCs, showing exclusively nuclear staining for WT1. We did not disregard cytoplasmic staining in any of the negative cases. Extratumoral fibroblasts, connecting tubules and intratumoral endothelial cells showed the same exclusively nuclear WT1 staining pattern. We reviewed WT1 expression patterns in aRCCs and the possible explanatory underlying metabolomics. For now, WT1 protein expression in aRCCs is insufficiently investigated, with significant discrepancies in the little data reported. Emerging WT1-targeted RCC immunotherapy will require adequate case selection and sustained efforts to standardize the quantification of tumor-associated antigens for aRCC and its many subtypes.

Keywords: WT1; Wilms’ tumor 1; adult renal cell carcinoma; biomarker; clone WT49; diagnosis; immunohistochemistry; molecular pathology; novel therapeutic targets; prognosis.

Figure 1

HE staining: (A) 200×, conventional solid clear cell renal carcinoma; (B) 200×, papillary architecture of RCC; (C) 400×, chromophobe RCC—clear cytoplasm with chromophobic perinuclear halo; (D) 200×, sarcomatoid dedifferentiation.

Figure 2

WT1 IHC staining: (A) 200×, control image of a quasi-normal positive glomerulus; (B) 400×, positive fusiform cells outside of the tumor tissue, with a morphology suggestive of fibroblasts/myofibroblasts; (C) 400×, blood vessel with a majority of endothelial cells manifesting positive nuclear staining; (D) 400×, large blood vessel close-up, with scarce positive endothelial cells (**) and a single positive adjacent tumor cell (*); (E) 400×, moderate density of positive tumor cells (+2), manifesting predominantly high intensity nuclear staining; (F) 400×, low density (+1) tumor tissue, manifesting only 2 distinct positive cells, with weak-intensity (*) and moderate-intensity (**) nuclear staining.

Figure 3

WT1 IHC staining: (a) 400×, positive connecting tubule cells, low-to-moderate nuclear staining; (b) 200×, positive renal corpuscles with severe degenerative lesions, compressed by neighboring tumor tissue, but with relatively unaffected podocytes.

Figure 4

High-density clear cell nuclear WT1 IHC staining (+3), moderate intensity. (a) Case 1: 200×. (b) Case 2: 200×.