WT1 and glomerular function

The Wilms' Tumour 1 (WT1) gene plays an important role at three different stages of kidney development. The onset of kidney formation, the progression of kidney formation and the maintenance of normal kidney function. Disruption of WT1 may lead to a whole spectrum of kidney diseases ranging from tumour development to mild forms of renal failure. However, the underlying mechanisms are largely unknown. The WT1 proteins have been implicated in various cellular processes like proliferation, differentiation and apoptosis and in agreement with these diverse functions, the number of target genes is still mounting. The development of mouse models in recent years has contributed considerably to a better understanding of the biological activities of WT1, and in this article we will discuss the role of WT1 during kidney formation and kidney function.     

Identification of a WT1 protein‐derived peptide,WT1187, as a HLA‐A*0206‐restricted,WT1‐specific CTL epitope

The Wilms' tumor gene WT1 is overexpressed in various kinds of hematopoietic malignancies as well as solid cancers, and this protein has been demonstrated to be an attractive target antigen for cancer immunotherapy. WT1‐specific CTL epitopes with a restriction of HLA‐A*2402 or HLA‐A*0201 have been already identified. In the present study it has been demonstrated that a 9‐mer WT1‐derived WT1₁₈₇ peptide, which had already been shown to elicit a WT1‐specific CTL response with a restriction of HLA‐A*0201, can also elicit a CTL response with a restriction of HLA‐A*0206. In all three different HLA‐A*0206⁺ healthy donors examined, WT1₁₈₇ peptide‐specific CTL could be generated from peripheral blood mononuclear cells, and the CTL showed cytotoxic activity that depended on dual expression of WT1 and HLA‐A*0206 molecules. The present study describes the first identification of a HLA‐A*0206‐restricted, WT1‐specific CTL epitope. The present results should help to broaden the application of WT1 peptide‐based immunotherapy from only HLA‐A*0201‐positive to HLA‐A*0206‐positive cancer patients as well.     

Evidence for WT1 as a Wilms tumor (WT) gene: intragenic germinal deletion in bilateral WT.

The inactivation of two alleles at a locus on the short arm of chromosome 11 (band 11p13) has been suggested to be critical steps in the development of Wilms tumor (WT), a childhood kidney tumor. Two similar candidate WT cDNA clones (WT33 and LK15) have recently been identified on the basis of both their expression in fetal kidney and their location within the smallest region of overlap of somatic 11p13 deletions in some tumors. These homozygous deletions, however, are large and potentially affect more than one gene. Using a cDNA probe to the candidate gene, we have analyzed DNA from both normal and tumor tissue from WT patients, in an effort to detect rearrangements at this locus. We report here a patient with bilateral WT who is heterozygous for a small (less than 11 kb) germinal deletion within this candidate gene. DNA from both tumors is homozygous for this intragenic deletion allele, which, by RNA-PRC sequence analysis, is predicted to encode a protein truncated by 180 amino acids. These data support the identification of this locus as an 11p13 WT gene (WT1) and provide direct molecular data supporting the two-hit mutational model for WT.     

A WT1 protein‐derived,naturally processed 16‐mer peptide,WT1332, is a promiscuous helper peptide for induction of WT1‐specific Th1‐type CD4+ T cells

The Wilms' tumor gene WT1 is overexpressed in various tumors, and the WT1 protein has been demonstrated to be an attractive target antigen for cancer immunotherapy. A WT1 protein‐derived 16‐mer peptide, WT1₃₃₂ (KRYFKLSHLQMHSRKH), which was naturally generated through processing in cells and could elicit Th1‐type CD4⁺ helper T cell responses with an HLA‐DRB1*0405‐restriction has previously been identified by us. In the present study, it has been demonstrated that WT1₃₃₂ can induce WT1₃₃₂‐specific CD4⁺ T cell responses with the restriction of not only HLA‐DRB1*0405 but also HLA‐DRB1*1501, ‐DRB1*1502, or ‐DPB1*0901. These HLA class II‐restricted WT1₃₃₂‐specific CD4⁺ T cell lines produced IFN‐γ but neither IL‐4 nor IL‐10 with WT1₃₃₂ stimulation, thus showing a Th1‐type cytokine profile. Furthermore, HLA‐DRB1*1501 or ‐DRB1*1502‐restricted WT1₃₃₂‐specific CD4⁺ T cell lines responded to WT1‐expressing transformed cells in an HLA‐DRB1‐restricted manner, which is consistent with our previous finding that WT1₃₃₂ is a naturally processed peptide. These results indicate that the natural peptide, WT1₃₃₂, is a promiscuous WT1‐specific helper epitope. WT1₃₃₂ is expected to apply to cancer patients with various types of HLA class II as a WT1‐specific helper peptide in combination with HLA class I‐restricted WT1 peptides.     

WT1 peptide vaccination combined with BCG-CWS is more efficient for tumor eradication than WT1 peptide vaccination alone

A Wilms tumor gene WT1 is expressed at high levels not only in most types of leukemia but also in various types of solid tumors, including lung and breast cancer. WT1 protein has been reported to serve as a target antigen for tumor-specific immunotherapy both in vitro in human systems and in vivo in murine models. We have shown that mice immunized with WT1 peptide or WT1 cDNA could reject a challenge from WT1-expressing tumor cells (a prophylactic model). However, it was not examined whether WT1 peptide vaccination had the potency to reject tumor cells in a therapeutic setting. In the present study, we demonstrated for the first time that WT1 peptide vaccination combined with Mycobacterium bovis bacillus Calmette-Guérin cell wall skeleton (BCG-CWS) was more effective for eradication of WT1-expressing tumor cells that had been implanted into mice before vaccination (a therapeutic model) compared with WT1 peptide vaccination alone. An intradermal injection of BCG-CWS into mice, followed by that of WT1 peptide at the same site on the next day, generated WT1-specific cytotoxic T lymphocytes (CTLs) and led to rejection of WT1-expressing leukemia or lung cancer cells. These results showed that BCG-CWS, which was well known to enhance innate immunity, could enhance WT1-specific immune responses (acquired immunity) in combination with WT1 peptide vaccination. Therefore, WT1 peptide vaccination combined with BCG-CWS may be applied to cancer immunotherapy in clinical settings.H. Nakajima and K. Kawasaki contributed equally to this study.