The cyclin-dependent kinase inhibitor p57 KIP2 is thought to be a potential tumor suppressor gene (TSG). The present study examines this possibility. We found that the expression of p57 KIP2 gene is absent in various hematological cell lines. Exposing cell lines to the DNA demethylating agent 5-aza-2-deoxycytidine restored p57 KIP2 gene expression. Bisulfite sequencing analysis of its promoter region showed that p57 KIP2 DNA was completely methylated in cell lines that did not express the p57 KIP2 gene. Thus, DNA methylation of its promoter might lead to inactivation of the p57 KIP2 gene. DNA methylation of this region is thought to be an aberrant alteration, since DNA was not methylated in normal peripheral blood mononuclear cells or in reactive lymphadenitis. Methylation-specific polymerase chain reaction analysis found frequent DNA methylation of the p57 KIP2 gene in primary diffuse large B-cell lymphoma (54.9%) and in follicular lymphoma (44.0%), but methylation was infrequent in myelodysplastic syndrome and adult T-cell leukemia (3.0% and 2.0%, respectively). These findings directly indicate that the profile of the p57 KIP2 gene corresponds to that of a TSG. IntroductionCell cycle progression is promoted by cyclins and cyclindependent kinases (CDKs) and is counterbalanced by CDK inhibitors. 1 These components are regulated in the normal cell cycle, and disrupted regulation is closely related to tumorigenesis. For example, activation of cyclin D1 by bcl-1 translocation (t(11; 14)(q13;q23)) is a critical genetic alteration in mantle cell lymphoma, 2,3 and the CDK inhibitor p16 INK4A is genetically lost or mutated in many malignancies. 4 CDK inhibitors have been categorized into 2 families. One family, inhibitors of CDK4 (INK4s), includes p16 and p15, has repeated ankyrinlike sequences, and is a specific inhibitor of CDK4 and CDK6, resulting in competing cyclin D. 5,6 The other family, kinase inhibitor proteins (KIPs), includes p21 CIP1 , p27 KIP1 , and p57 KIP2 , 7-10 and this family potently inhibits the binding of several cyclin/CDK complexes. The presence of mutations and deletions in INK4s indicates that they are tumor suppressor genes (TSGs) 4 and that their function as negative regulators of cell proliferation fits the profile of TSGs. Because the KIP family also consists of CDK inhibitors, genetic alterations of the p21 CIP1 gene 11 and p57 KIP2 genes 12-14 have been extensively studied. In particular, the p57 KIP2 gene is located at chromosome 11p15.5, a region implicated in sporadic cancers, including those of the breast, 15 liver, 16 and bladder. 17 Beckwith-Wiedemann syndrome (BWS), 18 which is characterized by the somatic overgrowth of various tissues, including the kidneys, liver, and skeletal muscle, and by a predisposition to embryonal tumors of these organs (Wilms tumor, hepatoblastoma, and embryonal rhabdomyosarcoma), is linked to this region. 19 Although germ line point mutations of the p57 KIP2 gene resulting in protein truncation have been identified in some patients with BWS, 20,21 so...

The homeobox gene PROX1 is related to the Drosophila prospero gene, which is expressed in the developing central nervous system and lens-secreting cone cells. We found that the PROX1 gene had missense and nonsense mutations in 4 of 29 hematologic cell lines analyzed. Decreased mRNA expression was also observed in half of these cell lines by RT-PCR. The restoration of PROX1 gene expression after treatment with the demethylating agent 5-aza-2'-deoxycytidine, as well as bisulfite sequencing analysis, indicated that gene silencing is caused by DNA hypermethylation at intron 1. Such hypermethylation was also seen in primary lymphomas (56.3%, 18/32) in a tumor-specific manner. These findings indicate that the profile of the PROX1 gene corresponds to that of a candidate tumor-suppressor gene.

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Although aberrant promoter hypermethylation of O6-methylguanine-DNA methyltransferase (MGMT) is a favorable prognostic marker in patients with diffuse large B-cell lymphoma (DLBCL), MGMT protein expression has not been thoroughly examined. The aim of this study was to evaluate the clinical implication of MGMT protein expression and its correlation with promoter hypermethylation of the gene. We investigated MGMT protein expression by immunohistochemical analysis of 63 DLBCL patients who received cyclophosphamide as part of multidrug regimens. In addition, promoter methylation of the MGMT gene was analyzed by a methylation-specific polymerase chain reaction assay, and correlations with chemotherapeutic effect and prognosis were statistically evaluated. Immunohistochemical assay results for MGMT protein were negative in 30.2% of patients with newly diagnosed DLBCL. Immunostaining results were closely correlated with the methylation status of the promoter. Promoter DNA methylation of the gene was not detected in 34 (81.0%) of 42 tumor samples determined to be MGMT-positive DLBCL by immunostaining and was detected in 15 (88.2%) of 17 cases of MGMT-negative DLBCL. Overall survival (OS) and disease-free survival (DFS) rates were significantly higher in MGMT-negative patients than in MGMT-positive patients (5-year OS, 81.3% versus 56.6% [P = .0375]; 5-year DFS, 66.3% versus 39.9% [P = .0121]). The combined rate for complete response (CR) plus unconfirmed CR was significantly higher in MGMT-negative patients (15/19, 79.0%) than in MGMT-positive patients (25/44, 56.8%) (P = .0488). A multivariate analysis showed that absence of MGMT expression was an independent prognostic factor for OS (relative risk, 4.09; P = .0258). Lack of MGMT protein expression is associated with aberrant promoter DNA methylation and appears to be a useful marker for predicting the survival of DLBCL patients.

The gene for the DNA-repair enzyme O6-methylguanine-DNA methyltransferase (MGMT), which is closely related with cellular sensitivity to alkylating agents, is inactivated by promoter hypermethylation in several human cancers, including malignant lymphoma. Promoter hypermethylation of the MGMT gene is a favorable prognostic factor in diffuse large B-cell lymphoma (DLBCL). Although inactivation of the MGMT gene is closely related to p53 gene mutations in several cancers, the relationship between p53 gene mutation and MGMT inactivation in malignant lymphoma has not been thoroughly examined. We studied the correlation between MGMT hypermethylation and p53 mutation in DLBCL and their impacts on patient prognosis. In a retrospective cohort study, we used a methylation-specific polymerase chain reaction technique to analyze the methylation status of the promoter region of the MGMT gene in 116 DLBCL patients who received cyclophosphamide as part of multidrug combination chemotherapies. Denaturing high-performance liquid chromatography and direct sequencing were used to search for p53 gene mutations in exons 5 through 9 in 96 of the 116 samples. Disease-free survival and overall survival were estimated by the Kaplan-Meier method. Multivariate survival analyses were performed with the Cox proportional hazards model. Forty-five (38.8%) of 116 DLBCL patients showed MGMT promoter hypermethylation. The presence of MGMT hypermethylation was associated with better overall survival (P = .036). MGMT promoter hypermethylation was a prognostic factor that was independent of established prognostic factors, such as age, disease stage, serum lactic dehydrogenase level, and the number of extranodal disease sites (hazard ratio, 2.43; 95% confidence interval, 1.28-4.61; P = .007). p53 mutations were detected in 19 (19.8%) of 96 patients and were identified as a risk factor in the complete remission rate and overall survival (P = .0040, and P = .027, respectively). A correlation between MGMT hypermethylation and p53 mutation or p53 G:C-to-A:T mutation was not observed (P = .88, and P = .31, respectively). MGMT promoter hypermethylation and p53 mutation are useful prognostic markers in DLBCL. The impact of MGMT inactivation on p53 mutation in DLBCL is unclear.

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Various kinds of hyperthermic treatment for malignant glioma had been inhibited due to both their incomplete feverish action and strict cooling effect of the brain. The author shows an effective results of hyperthermia for the treatment of malignant glioma in an in vivo study using stick type carboxymethylcellulose (CMC)-magnetite, a newly manufactured magnetite-product. A stick type CMC-magnetite, containing magnetite particles, was inserted into the T-9 glioma in the rat brain stereotactically, and the rats were exposed to an alternative magnetic field (AMF). The application time of AMF, which measured 88.9 kHz and 380 Oe, was 30 min a day. The rats were divided into three groups: three AMF applications (group I), one AMF application (group II) and no application but only injection of CMC-magnetite (control). As a result, the mean survival in days of these three groups measured 44.2+/-10.9 (group I), 17.0+/-1.5 (group II) and 14.4+/-1.5 (control). This investigation showed both significant effectiveness in attacking malignant glioma and significant prolonging of the survival time in rats. It is also a characteristic feature of the magnetite particles to spread through the tumor diffusely after three applications of AMF. This feature seemed to be one of the main factors that caused greater hyperthermic effect on glioma in this study. This method of hyperthermic treatment could be a useful strategy in the treatment of malignant glioma.

Combined treatment with interferon-beta, MCNU (Ranimustine), and radiotherapy was assessed in patients with malignant glioma who had not received previous cytotoxic drug therapy. Forty-three patients up to 75 years old with histopathologically confirmed malignant glioma were studied. All patients had tumors measurable by neuroimaging, a Karnofsky performance score exceeding 40, and an expected survival exceeding 2 months. A response rate of 49% (21/45) was observed, including 6 complete remissions (14%) and 15 partial remissions (35%). Of the 43 patients who completed initial therapy, 19 were given sequential maintenance therapy. Survival time was much longer with than without maintenance therapy. Toxic side effects were moderate and did not substantially affect patients' general condition. We concluded that this combination therapy had a pronounced effect on untreated malignant glioma, particularly in patients whose initial therapy was followed up with maintenance therapy.