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Molecular Oncology, Markers, Clinical Correlates |
Departments of Surgical Oncology [Y. M., A. A., C. E., T. T., Y. T., S. N.], Molecular Medicine [H. T.], and Clinical Laboratory Science [H. S.], Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| ABSTRACT |
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Experimental Design: WT1 mRNA expression in tumor tissues (n = 99) was examined by a quantitative, real-time PCR assay.
Results: No significant association was observed between WT1 mRNA levels and clinicopathological parameters such as menopausal status, tumor size, lymph node status, histological grade, and estrogen receptor status. Five-year disease-free survival rate of patients with high WT1 mRNA levels (62.6%) was significantly (P < 0.05) poorer than those with low WT1 mRNA levels (77.2%). Lymph node metastasis (P < 0.05), high histological grade (P < 0.01), and estrogen receptor negativity (P < 0.05) were also significantly associated with poor prognosis, respectively. Multivariate analysis revealed that WT1 mRNA levels were a significant prognostic factor, independent of the other conventional prognostic factors.
Conclusions: These results suggest that measurement of WT1 mRNA levels in tumor tissues might be useful as a new prognostic factor in breast cancer patients.
| INTRODUCTION |
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Recent studies have shown that WT1 plays an important role in the pathogenesis and progression of leukemia (11, 12, 13) . Inoue et al. (11) reported that the WT1 mRNA expression was significantly up-regulated in leukemia as compared with the normal hematopoietic cells, and that leukemia with high WT1 mRNA expression showed a significantly lower CR rate and a significantly worse overall survival than that with a low WT1 expression. These observations, however, seem to be inconsistent with the thesis derived from the studies on Wilms tumors that WT1 is a tumor suppressor gene. Rather, these observations seem to suggest that WT1 is an oncogene in leukemia. This speculation is further substantiated by the in vitro experiments, which showed that WT1 mRNA expression was down-regulated during differentiation in leukemia cell lines, and that treatment with antisense oligonucleotides for WT1 mRNA resulted in the growth inhibition in these cell lines (14) . In addition, growth of myeloid progenitor cells is stimulated, and differentiation of these cells is inhibited by inducing WT1 expression in these cells (12) . These results strongly indicate an oncogenic function of WT1 in leukemia.
WT1 expression has rarely been studied in breast cancers. Recently, Loeb et al. (15) have demonstrated that WT1 mRNA and protein are expressed in nearly 90% of breast cancers but not in most normal breast tissues. These results suggest that WT1 plays a certain role in the pathogenesis of breast cancer as an oncogene but not a tumor suppressor gene in analogy to leukemia. Silberstein et al. (16) studied the WT1 expression by immunohistochemistry and demonstrated an association of WT1 protein expression with a biologically aggressive phenotype of breast cancer such as ER negativity. Their observation suggests a possibility that WT1 expression can serve as a risk factor for developing recurrences in breast cancer patients. Therefore, in the present study, we have studied the relationship between WT1 mRNA levels and various clinicopathological parameters as well as prognosis to clarify the prognostic significance of WT1 mRNA expression in breast cancer patients.
| MATERIALS AND METHODS |
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The median follow-up period of the 99 patients was 48 months (range, 3960 months), and DFS of these patients was 73.1%. Twenty-one of 99 (21.2%) patients developed recurrences, i.e., 5 developed liver metastases, 4 developed lung metastases, 3 developed bone metastases, and 9 developed soft tissue metastases. Ipsilateral breast recurrences after breast-conserving surgery were not counted as recurrences.
RNA Extraction and Reverse Transcription.
Total cellular RNA was extracted from the frozen tumor specimens using TRIzol reagent according to the protocol provided by the manufacturer (Molecular Research Center, Cincinnati, OH). The 3 µg each of total RNA were used for synthesis of cDNA by Superscript II (Life Technologies, Inc., Rockville, MD) priming with oligo-(dT)15 primer under the condition at 42°C for 90 min, followed by heating at 70°C for 10 min.
Primers, Probes, and Real-Time PCR.
A real-time PCR amplification was carried out according to the method described previously (20)
. Briefly, primer pairs for amplification were 5'-GATAACCACACAACGCCCATC-3' and 5'-CACACGTCGCACATCCTGAAT-3'. The sequence of the probe, labeled with 6-carboxyfluorescein and 6-carboxy-N,N,N',N'-tetramethylrhodamine at the 5' and 3' sides, respectively, was 5'-ACACCGTGCGTGTGTATTCTGTATTGG-3'. PCR reactions were carried out using ABI Prism 7700 Sequence Detection System (Perkin-Elmer Applied Biosystems, Foster City, CA) under the condition of 95°C 10 min, followed by 50 cycles of 95°C for 30 s and 63°C for 1 min. To quantify gene transcripts precisely, the ß-glucuronidase transcripts were monitored as the quantitative control, and each sample was normalized on the basis of its ß-glucuronidase transcript content. The primer probe mixture for ß-glucuronidase was purchased from Perkin-Elmer Applied Biosystems, and the method of PCR was followed by the manufacturers protocol.
The standard curves for WT1 and ß-glucuronidase mRNA were generated using the serially diluted solutions of plasmid clones with either WT1 (10-5 to 10-1 µg) or ß-glucuronidase (10-8 to 10-4 µg) cDNA inserted by a part of each cDNA as templates. The amount of target gene expression was calculated from the standard curve, and quantitative normalization of cDNA in each sample was performed using the expression of ß-glucuronidase gene as an internal control. Finally, WT1 mRNA levels were shown as ratios to ß-glucuronidase mRNA levels when 10-5 µg and 10-8 µg of plasmid control defined as 1. Real-time PCR assays were conducted in duplicate for each sample, and the mean value was used for the calculation of mRNA expression levels.
ER Assay.
ER levels in breast cancers were measured by enzyme immunoassay using the kit provided by Abbott Research Laboratories (Chicago, IL). The cutoff value for ER was defined as 10 fmol/mg protein.
Statistical Methods.
The relationship between WT1 mRNA expression levels and clinicopathological characteristics was assessed by the Mann-Whitney test. DFS curves were calculated by the Kaplan-Meier method, and the log-rank test was used to evaluate the difference in DFS among the various patient subgroups. The proportional hazards model was used for the multivariate analysis. Statistical significance was assumed for P < 0.05.
| RESULTS |
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2 cm. There was no statistically significant association between WT1 mRNA expression and any other clinicopathological parameters such as menopausal status, lymph node status, histological grade, and ER status.
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| DISCUSSION |
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WT1 mRNA levels showed a trend toward an increase in patients with recurrence than those without it, suggesting that WT1 mRNA levels can be useful as a prognostic factor. In fact, we have been able to demonstrate that patients with high WT1 mRNA levels showed a significantly poorer prognosis than those with low WT1 mRNA levels. Furthermore, multivariate analysis has revealed that WT1 mRNA levels are a significant prognostic factor, independent of the conventional prognostic factors such as lymph node status, histological grade, and ER status. This is the first report that demonstrates the prognostic significance of WT1 mRNA levels in breast cancer patients. Although we used the mean + 2 SD of the WT1 mRNA levels in the normal breast tissues as the cutoff value for the WT1 mRNA high and low expression groups, an optimal cutoff value needs to be determined by a future study including a larger number patients.
It is suggested in acute leukemia that WT1 mRNA levels are useful in the prediction of chemosensitivity because it is based on the observation that patients with low WT1 mRNA levels achieve >90% CR rates, but those with intermediate and high WT1 mRNA levels achieve lower CR rates, i.e., 50 and 0%, respectively (11) . It is unknown, at present, whether there is a significant relationship between WT1 mRNA levels and response to chemotherapy or endocrine therapy in breast cancer. But if this is the case, the difference in treatment efficacy between the WT1 mRNA high and low expression groups could influence the prognosis, because all patients but five had been treated with adjuvant therapy in the present study. Ideally, a new prognostic factor is to be tested in the patients without adjuvant therapy. However, almost all breast cancer patients are treated with adjuvant therapy, according to the recommendation of the consensus meeting of St. Gallen (18 , 19 , 21) and NIH (22) . Thus, at present, it is nearly infeasible to evaluate a new prognostic factor among the patients without adjuvant therapy. Thus, strictly speaking, it is currently unknown whether the WT1 mRNA expression is a prognostic factor or a predictive factor or both. This problem, however, can be clarified, at least in part, by studying the significance of the WT1 mRNA expression as a predictive factor for endocrine treatment and/or chemotherapy in the neoadjuvant or metastatic setting.
The mechanism of up-regulation of WT1 mRNA expression has yet to be established. Although aberrant methylation of CpG islands in the promoter and the first intron of the WT1 gene has been reported in primary breast cancers (23) , Loeb et al. (15) have shown no association between the methylation status and WT1 mRNA expression in breast cancers. Thus, other transcriptional regulatory mechanisms seem to be implicated in the up-regulation of WT1 mRNA during carcinogenesis. Laux et al. (23) reported a novel 2.5-kb WT1 transcript lacking the first exon in the breast cancer cell line MDA-MB-231. Similarly, Dechsukhum et al. (24) detected a 2.1-kb transcript in prostate cancer cell line, leukemia cell line (K562), breast cancer cell line (MCF7), and acute leukemia. This 2.1-kb transcript consists of exons 610, together with a portion of intron 5 at the 5' end of the transcript. The function of this short transcript is unknown at present, but the gene product possibly affects the function because it appears to contain the zinc-finger domain but lacks the transactivation region of WT1 (24) . Furthermore, the other two splicing variants of WT1, which lack the fifth exon or nine bases between exons 9 and 10, have been reported (1 , 25) . These results suggest that the WT1 function can be different according to the various isoforms. Because the real-time PCR method used in the present study could not differentiate the wild type WT1 mRNA from its splicing variants, the prognostic significance of these splicing variants still remains to be studied.
In conclusion, we have suggested that the WT1 mRNA levels can serve as a significant prognostic factor in breast cancer patients, independent of the conventional prognostic factors such as lymph node status, histological grade, and ER status. Our preliminary results need to be confirmed by a future study including a larger number of patients with a longer follow-up period.
| FOOTNOTES |
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1 Supported in part by grants from Ministry of Education, Culture, Sports, Science and Technology, Japan. ![]()
2 To whom requests for reprints should be addressed, at Department of Surgical Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan. Phone: 81-6-6879-3772; Fax: 81-6-6879-3779; E-mail: noguchi{at}onsurg.med.osaka-u.ac.jp ![]()
3 The abbreviations used are: WT1, Wilms tumor suppressor 1; IGF, insulin-like growth factor; CR, complete remission; ER, estrogen receptor; DFS, disease-free survival. ![]()
Received 11/ 6/01; revised 2/15/02; accepted 2/25/02.
| REFERENCES |
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and -ß messenger RNA expression in breast carcinoma by real-time polymerase chain reaction. Cancer (Phila.), 89: 1732-1738, 2000.[CrossRef][Medline]
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