Hiroya Tamaki

Human cytotoxic T-lymphocyte responses specific for peptides of the wild-type Wilms' tumor gene (WT1 ) product

Abstractu2002The product of the Wilms tumor gene WT1 is a transcription factor overexpressed not only in leukemic blast cells of almost all patients with acute myeloid leukemia, acute lymphoid leukemia, and chronic myeloid leukemia, but also in various types of solid tumor cells. Thus, it is suggested that the WT1 gene plays an important role in both leukemogenesis and tumorigenesis. Here we tested the potential of WT1 to serve as a target for immunotherapy against leukemia and solid tumors. Four 9-mer WT1 peptides that contain HLA-A2.1-binding anchor motifs were synthesized. Two of them, Db126 and WH187, were determined to bind to HLA-A2.1 molecules in a binding assay using transporter associated with antigen processing-deficient T2 cells. Peripheral blood mononuclear cells from an HLA-A2.1-positive healthy donor were repeatedly sensitized in vitro with T2 cells pulsed with each of these two WT1 peptides, and CD8+ cytotoxic T lymphocytes (CTLs) that specifically lyse WT1 peptide-pulsed T2 cells in an HLA-A2.1-restricted fashion were induced. The CTLs also exerted specific lysis against WT1-expressing, HLA-A2.1-positive leukemia cells, but not against WT1-expressing, HLA-A2.1-negative leukemia cells, or WT1-nonexpressing, HLA-A2.1-positive B-lymphoblastoid cells. These data provide the first evidence of human CTL responses specific for the WT1 peptides, and provide a rationale for developing WT1 peptide-based adoptive T-cell therapy and vaccination against leukemia and solid tumors.

Expression of the Wilms' Tumor Gene WT1 in Solid Tumors and Its Involvement in Tumor Cell Growth

To determine the role of the Wilms tumor gene WT1 in tumorigenesis of solid tumors, expression of the WT1 gene was examined in 34 solid tumor cell lines (four gastric cancer cell lines, five colon cancer cell lines, 15 lung cancer cell lines, four breast cancer cell lines, one germ cell tumor cell line, two ovarian cancer cell lines, one uterine cancer cell line, one thyroid cancer cell line, and one hepatocellular carcinoma cell line) by means of quantitative reverse transcriptase‐polymerase chain reaction. WT1 gene expression was detected in three of the four gastric cancer cell lines, all of the five colon cancer cell lines, 12 of the 15 lung cancer cell lines, two of the four breast cancer cell lines, the germ cell tumor cell line, the two ovarian cancer cell lines, the uterine cancer cell line, the thyroid cancer cell line, and the hepatocellular carcinoma cell line. Therefore, of the 34 solid tumor cell lines examined, 28 (82%) expressed WT1. Three cell lines expressing WT1 (gastric cancer cell line AZ‐521, lung cancer cell line OS3, and ovarian cancer cell line TYK‐nu) were further analyzed for mutations and/or deletions in the WT1 gene by means of single‐strand conformation polymorphism analysis. However, no mutations or deletions were detected in the region of the WT1 gene ranging from the 3/end of exon 1 to exon 10 (the WT1 gene consists of 10 exons) in these three cell lines. Furthermore, when AZ‐521, OS3, and TYK‐nu cells were treated with WT1 antisense oligomers, the growth of these cells was significantly inhibited in association with a reduction in WT1 protein levels. Furthermore, constitutive expression of the transfected WT1 gene in cancer cells inhibited the antisense effect of WT1 antisense oligomer on cell growth. These results indicated that the WT1 gene plays an essential role in the growth of solid tumors and performs an oncogenic rather than a tumor‐suppressor gene function.

Overexpression of the Wilms' tumor gene WT1 in de novo lung cancers

Expression of the Wilms tumor gene WT1 in de novo lung cancer was examined using quantitative real‐time RT‐PCR and immunohistochemistry. Overexpression of the WT1 gene was detected by RT‐PCR in 54/56 (96%) de novo non‐small cell lung cancers examined and confirmed by detection of WT1 protein with an anti‐WT1 antibody. Overexpression of the WT1 gene was also demonstrated in 5/6 (83%) de novo small cell lung cancers by immunohistochemistry. Furthermore, when the WT1 gene was examined for mutations by direct sequencing of genomic DNA in 7 lung cancers, no mutations were found. These results suggest that the nonmutated, wild‐type WT1 gene plays an important role in tumorigenesis of de novo lung cancers and may provide us with the rationale for new therapeutic strategies for lung cancer targeting the WT1 gene and its products.

The Wilms’ tumor gene WT1 is a good marker for diagnosis of disease progression of myelodysplastic syndromes

The Wilms’ tumor gene, WT1, is a tumor marker for leukemic blast cells. The WT1 expression levels were examined for 57 patients with myelodysplastic syndromes (MDS) (refractory anemia (RA), 35; RA with excess of blasts (RAEB) 14; RAEB in transformation (RAEB-t), six; and MDS with fibrosis, two) and 12 patients with acute myeloid leukemia (AML) evolved from MDS. These levels significantly increased in proportion to the disease progression of MDS from RA to overt AML via RAEB and RAEB-t in both bone marrow (BM) and peripheral blood (PB). WT1 expression levels in PB significantly correlated with the evolution of RAEB or RAEB-t to overt AML within 6 months. Therefore, WT1 expression levels in PB were superior to those in BM for early prediction of the evolution to AML by means of quantitation of the WT1 expression levels. Furthermore, WT1 expression in PB of patients with overt AML evolved from MDS was significantly decreased by effective chemotherapy or allogeneic stem cell transplantation and became undetectable in long-term survivors. These results clearly showed that WT1 expression levels are a tumor marker for preleukemic or leukemic blast cells of MDS and thus reflect the disease progression of MDS. Therefore, monitoring of WT1 expression levels has made continuous assessment of the disease progression of MDS possible, as well as the prediction of the evolution of RAEB or RAEB-t to overt AML within 6 months. The results also showed that quantitation of WT1 expression levels is useful for diagnosis of minimal residual disease of MDS with high sensitivity, thus making it possible to evaluate the efficacy of treatment for MDS.

Constitutive expression of the Wilms’ tumor gene WT1 inhibits the differentiation of myeloid progenitor cells but promotes their proliferation in response to granulocyte-colony stimulating factor (G-CSF)

Bone marrow (BM) cells that were concentrated for hematopoietic progenitor cells by in vivo treatment with 5-FU were infected with a recombinant retrovirus containing a human full-sized, non-spliced type WT1 (Wilms tumor gene 1) cDNA and then colony-assayed in the presence of granulocyte-colony stimulating factor (G-CSF). Significantly more colony-forming units granulocyte-monocyte (CFU-GM), colony-forming units granulocyte (CFU-G), and colony-forming units monocyte (CFU-M) colonies were formed in response to G-CSF from the BM cells infected with the WT1-containing retrovirus than from the control BM cells infected with an empty vector. Furthermore, FACS analysis of cell surface differentiation markers showed the inhibition of differentiation by constitutive WT1 expression resulting from the infection with the WT1-containing retrovirus. These results thus showed that the constitutive WT1 expression promoted the proliferation of myeloid progenitor cells but inhibited their differentiation in response to G-CSF, suggesting the alteration of G-CSF signaling pathway. The results also supported our hypothesis that the WT1 gene performs an oncogenic rather than a tumor suppressor gene function in hematopoietic progenitor cells, although the WT1 gene potentially performs both functions. This finding implies an important role of the WT1 gene in leukemogenesis.

Very low frequencies of human normal CD34+ haematopoietic progenitor cells express the Wilms' tumour gene WT1 at levels similar to those in leukaemia cells.

Summary. The Wilms tumour gene, WT1, is expressed at high levels in leukaemia cells and plays an important role in leukaemogenesis. WT1 is also expressed in human normal CD34+ bone marrow (BM) cells at about 100 times lower levels than in leukaemia cells. To identify and characterize WT1‐expressing cells in CD34+ BM cells, they were sorted into single cells and analysed for WT1 expression using two kinds of single‐cell reverse transcriptase polymerase chain reaction (RT–PCR) methods. Using the semiquantitative single‐cell polyA‐PCR + sequence‐specific (SS)‐PCR method, WT1 expression was detected in four (1·3%) out of 319 CD34+ BM single cells. To confirm the above results, a single‐cell nested sequence‐specific (NSS)‐RT–PCR method that was less quantitative but more sensitive than the polyA‐PCR + SS‐PCR method was also performed, and WT1 expression was detected in 15 (1·1%) out of 1315 CD34+ BM single cells. In total, WT1 expression was found in 19 (1·2%) out of 1634 CD34+ BM single cells. No significant differences in the frequencies of WT1‐expressing cells were found between CD34+CD38– and CD34+CD38+ BM single cells. Furthermore, WT1‐expressing CD34+ BM single cells expressed WT1 at levels similar to those in K562 leukaemia single cells. Analysis of lineage‐specific and cell cycle gene expression in WT1‐expressing CD34+ BM single cells showed that the WT1 gene could be expressed in both uncommitted, dormant CD34+CD38– and lineage‐committed, proliferating CD34+CD38+ BM cells. Our results could indicate that these WT1‐expressing CD34+ BM cells were normal counterparts of leukaemia cells.

Monitoring Minimal Residual Disease in Leukemia Using Real-time Quantitative Polymerase Chain Reaction for Wilms Tumor Gene (WT1)

We previously showed that Wilms tumor gene (WT1) expression level, measured by quantitative reverse transcriptase polymerase chain reaction (RT-PCR), was useful as an indicator of minimal residual disease (MRD) in leukemia and myelodysplastic syndrome. However, in conventional quantitative RT-PCR (CQ-PCR), RT-PCR must be performed for various numbers of cycles depending onWT1 expression level. In the present study, we developed a new real-time quantitative RT-PCR (RQ-PCR) method for quantitatingWT1 transcripts. Results of intraassay and interassay variability tests demonstrated that the real-timeWT1 assay had high reproducibility.WT1 expression levels measured by the RQ- and the CQ-PCR methods were strongly correlated (r = 0.998). Furthermore, a strong correlation was observed amongWT1 transcript values normalized with 3 different control genes (β-actin,ABL, andglyceraldehyde-3-phosphate dehydrogenase) and between relativeWT1 transcript values withWT1 expression in K562 cells as the reference and absoluteWT1 transcript copy numbers per microgram RNA. WhenWT1 expression andminor bcr-abl expression were concurrently monitored in 2 patients withbcr-abl-positive acute lymphoblastic leukemia, both MRDs changed mostly in parallel, indicating the reliability and validity of our RQ-PCR method. In conclusion, this RQ-PCR method is convenient and reliable for monitoring MRD and enables routine clinical use of aWT1 assay.

Successful donor leukocyte transfusion at molecular relapse for a patient with acute myeloid leukemia who was treated with allogeneic bone marrow transplantation: importance of the monitoring of minimal residual disease by WT1 assay

We report here that a patient with relapsed AML after allogeneic bone marrow transplantation achieved and maintained complete remission (CR) after effective donor leukocyte transfusion (DLT), without the occurrence of GVHD and marrow aplasia, for more than 21 months. This continuous CR maintenance is mainly due to the application of DLT at molecular relapse that was diagnosed by monitoring minimal residual disease (MRD) by the quantitation of WT1 (Wilms tumor gene) expression levels (WT1 assay). The present case demonstrates that early application of DLT at molecular relapse is essential for the improvement of the efficacy of DLT for relapsed AML after BMT.

Successful engraftment of HLA-haploidentical related transplants using nonmyeloablative conditioning with fludarabine, busulfan and anti-T-lymphocyte globulin

Successful engraftment of HLA-haploidentical related transplants using nonmyeloablative conditioning with fludarabine, busulfan and anti-T-lymphocyte globulin

Combination of tacrolimus, methotrexate, and methylprednisolone prevents acute but not chronic Graft-Versus-Host disease in unrelated bone marrow transplantation

Background. Graft-versus-host disease (GVHD) is still a major problem in allogeneic bone marrow transplantation (BMT). Prophylactic regimens used against GVHD in unrelated BMT, including cyclosporine (CsA)-plus-methotrexate (MTX), CsA-plus-MTX-plus-prednisone, and tacrolimus (FK506)-plus-MTX, are still unsatisfactory (34–70% occurrence of grades II–IV GVHD). To address this problem, we examined the efficacy of FK506-plus-MTX-plus-methylprednisolone (mPSL) in 20 patients who underwent BMT from unrelated donors. Methods. All patients received FK506 beginning the day before transplantation at a dose of 0.03 mg/kg per day by continuous intravenous (IV) infusion. MTX was administered at a dose of 10 mg/m2 IV on day 1, and 7 mg/m2 on days 3, 6, and 11. Intravenous administration of mPSL was started at a dose of 2 mg/kg per day on day 1. In the absence of acute GVHD, mPSL was gradually tapered from day 29. Results. Development of acute GVHD was almost completely suppressed (one patient with grade I, none with grades II–IV). However, the incidence and severity of chronic GVHD did not decrease. Eight of 12 patients with extensive chronic GVHD died of thrombotic microangiopathy or infection. A vigorous fluctuation (>100 U/mL per 10 days) of the soluble interleukin 2 receptor level in the serum after engraftment was highly related to the occurrence of chronic GVHD. Conclusions. An FK506-plus(+)-MTX-plus(+)-mPSL prophylactic regimen could almost completely suppress acute GVHD but not chronic GVHD in unrelated BMT. In this GVHD prophylactic system, the extent of the change of soluble interleukin 2 receptor level may be a good predictor of development of chronic GVHD.