WT1 modulates apoptosis by transcriptionally upregulating the bcl-2 proto-oncogene.
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The Wilms' tumor suppressor gene, WT1, encodes a zinc finger transcription factor that has been demonstrated to negatively regulate several growth factor and cognate receptor genes. However, inconsistent with its tumor suppressor function, WT1 has also been demonstrated to be required to inhibit programmed cell death in vitro and in vivo. Moreover, anaplastic Wilms' tumors, which typically express wild-type WT1, display extreme resistance to chemotherapeutic agents that kill tumor cells through the induction of apoptosis. Although p53 mutations in anaplastic Wilms' tumors have been associated with chemoresistance, this event is believed to occur late during tumor progression. Therefore, since dysregulated WT1 expression occurs relatively early in Wilms' tumors, we hypothesized that WT1 was required to transcriptionally upregulate genes that provide a cell survival advantage to tumor cells. Here we demonstrate that sporadic Wilms' tumors coexpress WT1 and the anti-apoptotic Bcl-2 protein. Using rhabdoid cell lines overexpressing WT1, we show that WT1 activates the endogenous bcl-2 gene through a transcriptional mechanism. Transient transfections and electromobility shift assays demonstrate that WT1 positively stimulates the bcl-2 promoter through a direct interaction. Moreover, WT1 expressing cells displaying upregulated Bcl-2 were found to be resistant to apoptosis induced by staurosporine, vincristine and doxorubicine. These data suggest that in certain cellular contexts, WT1 exhibits oncogenic potential through the transcriptional upregulation of anti-apoptotic genes such as bcl-2. (+info)
Successful treatment of advanced natural killer cell lymphoma with high-dose chemotherapy and syngeneic peripheral blood stem cell transplantation.
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CD56+ angiocentric lymphoma has currently been recognized as a distinct clinical entity which is the prototype of the putative NK cell lymphomas. A 16-year-old Japanese girl with advanced CD56+ angiocentric lymphoma received high-dose chemotherapy supported with syngeneic peripheral blood stem cell transplantation (PBSCT). Prior to syngeneic PBSCT, she received six cycles of conventional chemotherapy before transplantation, resulting in a partial response. PBSC were mobilized with granulocyte colony-stimulating factor (G-CSF) and collected from her identical twin. High-dose cyclophosphamide, MCNU, etoposide, and carboplatin were used for pretransplant conditioning. Syngeneic PBSCT was well tolerated. She achieved complete remission and is now surviving in continuous complete remission for more than 30 months after syngeneic PBSCT. Thus, marrow-ablative chemotherapy facilitated by autologous or allogeneic PBSCT should be considered as part of the primary therapy for poor prognosis NK cell lymphomas. (+info)
Dose-escalation of CHOP in non-Hodgkin's lymphoma.
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BACKGROUND: CHOP is considered to be the gold standard for patients with histologically aggressive non-Hodgkin's lymphoma both in limited and advanced stages. In order to determine the maximum tolerable dose of an intensified CHOP regimen, a dose-escalation study of CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) in patients with non-Hodgkin's lymphoma (NHL) was started. PATIENTS AND METHODS: With an increased fixed dose of doxorubicin at 75 mg/m2 instead of 50 mg/m2 on day 1 and standard doses of vincristine (1.4 mg/m2 on day 1) and prednisone (100 mg day 1 through 5), cyclophosphamide dose was escalated by increments of 250 mg/m2 in consecutive cohorts of at least three patients starting from 1000 mg/m2. Granulocyte-colony stimulating factor (G-CSF) support was added to the regimen starting from the dose-level inducing grade 4 neutropenia lasting more than five days in two patients. Dose limiting toxicity was defined as either the dose inducing grade 4 neutropenia lasting more than seven days despite the use of G-CSF, or grade 3-4 thrombocytopenia lasting more than seven days, or any grade 4 non-hematological toxicity other than alopecia. The dose-level below the one inducing dose-limiting toxicity was defined as maximum tolerable dose. All patients were treated on an outpatient basis. Dose-intensity parameters for single agent doxorubicin and cyclophosphamide as well as for the whole regimen were evaluated. RESULTS: Eighty-seven patients are evaluable over a four-year study period. At 1750 mg/m2 dose-level, G-CSF was added to the regimen according to described criteria. At the cyclophosphamide dose of 3000 mg/m2, dose-limiting hematological toxicity occurred in two patients, with one grade 4 thrombocytopenia and neutropenia and one grade 4 neutropenia lasting more than seven days. Thus, cyclophosphamide dose of 2750 mg/m2 was defined as maximum tolerable dose. CONCLUSIONS: CHOP intensification of approximately 1.8 times that of the standard regimen is feasible and safely administered on an outpatient basis with G-CSF support. Further investigation on the role of dose-intensity in the outcome of NHL should focus on the comparison of intensified CHOP regimen and standard CHOP or high-dose chemotherapy. (+info)
Localization of a substrate specificity domain in the multidrug resistance protein.
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Multidrug resistance protein (MRP) confers resistance to a number of natural product chemotherapeutic agents. It is also a high affinity transporter of some physiological conjugated organic anions such as cysteinyl leukotriene C(4) and the cholestatic estrogen, 17beta-estradiol 17(beta-D-glucuronide) (E(2)17betaG). We have shown that the murine orthologue of MRP (mrp), unlike the human protein, does not confer resistance to common anthracyclines and is a relatively poor transporter of E(2)17betaG. We have taken advantage of these functional differences to identify region(s) of MRP involved in mediating anthracycline resistance and E(2)17betaG transport by generating mrp/MRP hybrid proteins. All hybrid proteins conferred resistance to the Vinca alkaloid, vincristine, when transfected into human embryonic kidney cells. However, only those in which the COOH-terminal third of mrp had been replaced with the corresponding region of MRP-conferred resistance to the anthracyclines, doxorubicin, and epirubicin. Exchange of smaller segments of the COOH-terminal third of the mouse protein by replacement of either amino acids 959-1187 or 1188-1531 with those of MRP produced proteins capable of conferring some level of resistance to the anthracyclines tested. All hybrid proteins transported cysteinyl leukotriene C(4) with similar efficiencies. In contrast, only those containing the COOH-terminal third of MRP transported E(2)17betaG with an efficiency comparable with that of the intact human protein. The results demonstrate that differences in primary structure of the highly conserved COOH-terminal third of mrp and MRP are important determinants of the inability of the murine protein to confer anthracycline resistance and its relatively poor ability to transport E(2)17betaG. (+info)
Synergistic anticancer effects of tetrandrine combined with doxorubicin or vincristine in vitro.
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AIM: To study the interaction between tetrandrine (Tet) and doxorubicin (Dox) or vincristine (Vin) against human breast cancer cell lines MCF-7 and MCF-7/Dox or human nasopharyngeal cancer cell lines KB and KBV200 in vitro. METHODS: Anticancer activities of a drug alone and a drug combination of Tet and Dox or Vin were determined by tetrazolium (MTT) method. The interaction between Tet and Dox or Vin was evaluated by both a value of a sum of fractional inhibitory concentration (SFIC) and an isobologram method. RESULTS: The SFIC values of the three-different-ratio combinations between Tet and Dox ranged from 0.14 to 0.38 for MCF-7, and 0.10 to 0.29 for MCF-7/Dox; those of Tet-Vin combinations ranged from 0.21 to 0.37 for KB, and 0.32 to 0.63 for KBV200. All the SFIC values of the combination between Tet and Dox or Vin were less than 1.0 when the 3 ratios of the 2 drugs in combination were used, and the shapes of isobolic curves obtained from the combination were concave. CONCLUSION: The interaction between Tet and Dox or Vin against the human cancer cells was markedly synergistic. (+info)
Sixty percent salvage rate for germ-cell tumours using sequential m-BOP, surgery and ifosfamide-based chemotherapy.
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BACKGROUND: In germ-cell tumours (GCT), there is continuing controversy over the relative merits of dose dense therapy (increased frequency over a given time) versus vertical intensification (increased dose per fraction). The value of using a cisplatin-based dose dense approach in the salvage setting has not been documented and in addition the role of methotrexate remains uncertain. This paper reviews results from our investigations of these issues. PATIENTS AND METHODS: Between 1987 and 1996, 65 patients with relapsing or refractory germ-cell tumour received weekly m-BOP (methotrexate, bleomycin, vincristine and cisplatin) as salvage therapy. Residual masses were excised if possible and patients progressing after this received cisplatin and ifosfamide based chemotheraphy with or without high dose chemotherapy (HDCT) consolidation. RESULTS: With a median follow-up of 33 months, 34% are progression free following m-BOP, 11% who had surgery for residual masses which showed viable cancers are progression free. A further 15% who progressed following m-BOP with or without surgery were rendered progression free by third-line therapy. CONCLUSIONS: The use of m-BOP as second line therapy with deferment of cisplatin and ifosfamide based treatment to third line therapy with consolidation of third line responses with HDCT, leads to an overall progression-free survival of 60%. It does not appear that M-BOP prejudiced the response to third line therapy suggesting a lack of cross resistance. The potentially lower risk of leukaemia and infertility from m-BOP requires further evaluation. (+info)
Defective G1-S cell cycle checkpoint function sensitizes cells to microtubule inhibitor-induced apoptosis.
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Defective cell cycle checkpoint function has been linked to enhanced sensitivity of tumor cells to certain genotoxic agents. To determine whether loss of the G1-S checkpoint function would sensitize tumor cells to microtubule inhibitor (MTI)-induced apoptosis, we examined the effect of the MTIs, Taxol and vincristine, on the cell cycle kinetics and survival of two isogenic cell lines, HCT116 p21+/+ and HCT116 p21-/-, which differ only at the p21 locus. p21-deficient cells displayed a dose-dependent, enhanced chemosensitivity to MTIs in both monolayer and soft agar assays as well as in mice xenograft tumors. The increased sensitivity of the p21-deficient cells to MTIs correlated with prolonged cyclin B1/Cdc2 activity and the occurrence of endoreduplication. Furthermore, sensitivity of p53-deficient cells to MTI-induced apoptosis was significantly reduced by induction of ectopic p21 protein. The results suggest that the status of G1-S checkpoint function in tumor cells may be an important determinant in the efficacy of MTIs used clinically. (+info)
Intravascular lymphomatosis presenting as an ascending cauda equina: conus medullaris syndrome: remission after biweekly CHOP therapy.
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A 63 year old man developed dysaesthesia in the legs followed by a subacute ascending flaccid paraparesis with sacral sensory and autonomic involvement. Intravascular lymphomatosis (IVL) was favoured by the presence of low grade fever and raised serum C reactive protein, CSF pleocytosis, raised lymphoma markers (serum LDH, soluble IL-2 receptor), and steroid responsiveness. Only muscle, among several organ biopsies, confirmed IVL. A cytogenetic study of the bone marrow showed chromosome 6 monosomy, as previously reported. The monosomy of chromosome 19, which bears the intercellular cell adhesion molecule-1, newly found in this case, may be related to the unique tumour embolisation of IVL. The CHOP regimen (six courses in 12 weeks) using granulocyte colony stimulating factor (G-CSF) led to gradual resolution of myeloradiculopathy and laboratory supported remission lasting for more than 13 months. The biweekly CHOP with G-CSF support may be a choice of chemotherapy in averting rapidly fatal IVL. (+info)