Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The antitumor activity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in mice previously was shown to be markedly enhanced by co-administration of thymidine. We have examined the cellular mechanisms underlying the augmentation effect of thymidine. It was found that thymidine did not increase the cytotoxicity of BCNU for B16/F10 melanoma or L1210 leukemia cells in vitro. Instead, thymidine appeared to augment the activity of tumor-specific cytotoxic T-cells in tumor-bearing mice, which specifically rejected a secondary challenge with the B16/F10 tumor. Thus, development of an antitumor immune response is facilitated by thymidine in BCNU-induced immunosuppressed mice. These preclinical studies suggested that combination therapy with alkylating agents and thymidine may be a more efficacious and less toxic anticancer therapy. The potential efficacy of the sequential administration of dacarbazine (DTIC), BCNU, and thymidine in patients with advanced malignant melanoma was investigated. As predicted from animal studies, sequential administration of DTIC, BCNU, and thymidine is a relatively nontoxic therapy for metastatic melanoma. This treatment induced durable responses in up to 35% of patients, and hence is superior to many commonly used toxic combination chemotherapies. The mechanism of action, although not well characterized, is thought to be mediated through protection of the cellular immune process, as well as organ function, from alkylating agent toxicity through modulation of DNA repair enzymes such as O(6)-alkylguanine-DNA alkyltransferase in normal tissue. Thus, thymidine is a biomodulator, which not only protects patients from hematologic, pulmonary, and hepatic toxicities associated with DTIC and BCNU chemotherapy, but also potentiates therapeutic efficacy.
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PMID:Molecular basis for thymidine modulation of the efficacy and toxicity of alkylating agents. 953 72

Primary effusion lymphoma (PEL) represents a peculiar type of B cell lymphoma which associates with HHV-8 infection and preferentially grows in liquid phase in the serous body cavities. In this report, we provide the detailed characterization of a newly established PEL cell line, termed CRO-AP/6. The cell line was obtained from the pleural effusion of a HIV-positive patient with PEL. Its derivation from the tumor clone was established by immunogenotypic analysis. Detailed phenotypic investigations defined that CRO-AP/6 reflects pre-terminally differentiated B cells expressing the CD138/syndecan-1 antigen. Karyotypic studies of CRO-AP/6 identified several chromosomal abnormalities, whereas genotypic studies ruled out the involvement of molecular lesions associated with other types of B cell lymphoma. Both CRO-AP/6 and the parental tumor sample harbored infection by HHV-8. Conversely, EBV infection was present in the parental tumor sample although not in CROAP/6, indicating that CRO-AP/6 originated from the selection of an EBV-negative tumor subclone. The pattern of viral (HHV-8 v-cyclin) and cellular (p27Kip1) regulators of cell cycle expressed by CRO-AP/6, together with the results of growth fraction analysis, point to abrogation of the physiological inverse relationship between proliferation and p27Kip1 expression. Also, both CRO-AP/6 and the parental tumor sample display biallelic inactivation of the DNA repair enzyme gene O6-methylguanine-DNA methyltransferase (MGMT) by promoter methylation. Overall, the CRO-AP/6 cell line may help understand cell cycle control of PEL cells, may clarify the relative contribution of HHV-8 and EBV to the disease growth and development and may facilitate the identification of recurrent cytogenetic abnormalities highlighting putative novel cancer related loci relevant to PEL.
Leukemia 2000 Jul
PMID:Characterization of a novel HHV-8-positive cell line reveals implications for the pathogenesis and cell cycle control of primary effusion lymphoma. 1091 56

Chemotherapeutic agents used in the treatment of cancer often lead to dose-limiting bone marrow suppression and may initiate secondary leukemia. N,N',N"-triethylenethiophosphoramide (thiotepa), a polyfunctional alkylating agent, is used in the treatment of breast, ovarian, and bladder carcinomas and is also being tested for efficacy in the treatment of central nervous system tumors. Thiotepa produces ring-opened bases such as formamidopyrimidine and 7-methyl-formamidopyrimidine, which can be recognized and repaired by the formamidopyrimidine glycosylase/AP lyase (Fpg) enzyme of Escherichia coli. Using this background information, we have created constructs using the E. coli fpg gene along with the functional equivalent human ortholog alpha-hOgg1. Although protection with the Fpg protein has been previously observed in Chinese hamster ovary cells, we demonstrate significant (100-fold) protection against thiotepa using the E. coli Fpg or the human alpha-hOgg1 cDNA in NIH3T3 cells. We have also observed a 10-fold protection by both the Fpg and alpha-hOgg1 transgenes against 1,3-N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) and, to a lesser extent, mafosfamide (2-fold), an active form of the clinical agent cyclophosphamide. These latter two findings are novel and are particularly significant since the added protection was in an O(6)-methylguanine-DNA methyltransferase-positive background. These results support our general approach of using DNA base excision repair genes in gene therapy for cellular protection of normal cells during chemotherapy, particularly against the severe myelosuppressive effect of agents such as thiotepa, BCNU, and cyclophosphamide.
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PMID:Protection of mammalian cells against chemotherapeutic agents thiotepa, 1,3-N,N'-bis(2-chloroethyl)-N-nitrosourea, and mafosfamide using the DNA base excision repair genes Fpg and alpha-hOgg1: implications for protective gene therapy applications. 1118 13

Methylation profile was analyzed in eleven cases of therapy-related leukemia (t-leukemia) for p14, p15, p16, Rb, hMLH1, hMSH2, MGMT, APC, RAR beta, DAPK, RIZ1, FHIT, and SOCS-1 genes by using methylation specific polymerase chain reaction (MSP) analysis. Six (55%) of eleven cases showed methylation of at least one gene. The average time to the development of t-leukemia after the treatment of the primary tumor was significantly shorter in patients with methylation than those without methylation (49.3 months vs. 133.2 months, P=0.044). These results suggest that hypermethylation might be involved in the development of t-leukemia.
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PMID:Aberrant methylation in promoter-associated CpG islands of multiple genes in therapy-related leukemia. 1288 5

Multiple genes have been shown to be independently hypermethylated in lymphoid malignancies. We report here on the extent of concurrent methylation of E-cadherin, Dap-kinase, O(6)MGMT, p73, p16, p15 and p14 in 129 pediatric ALL cases. While most of these genes demonstrated methylation in a proportion of cases, O(6)MGMT, p16 and p14 were infrequently methylated (11, 7 and 3%, respectively). Methylation of at least one gene was found in the vast majority (83%) of cases. To determine the extent and concordance of methylation we calculated a methylation index (MI=number of methylated genes/number of studied genes) for each sample. The average MI was 0.28, corresponding to 2/7 methylated genes. MI was correlated with standard prognostic factors, including immunophenotype, age, sex, WBC and presence of specific translocations (TEL-AML1, BCR-ABL, E2A-PBX1 or MLL-AF4). We determined that children >/=10 years old and children presenting with high WBC (>/=50 x 10(9)/l) both associated with a higher MI (P<0.01 and <0.05, respectively). T-ALLs demonstrated a lower MI (median=0.17) than precursor B ALLs (median=0.28). Among the different molecular subgroups, MLL-ALLs had the highest MI (mean=0.35), while ALLs carrying the t(1;19) had the lowest MI (mean=0.07). The most common epigenetic lesion in childhood ALL was methylation of E-cadherin (72%) independent of the molecular subtype or other clinicopathological factors.
Leukemia 2003 Sep
PMID:Concurrent methylation of multiple genes in childhood ALL: Correlation with phenotype and molecular subgroup. 1297 Jul 85

Cancer is also an epigenetic disease. The main epigenetic modification in humans is DNA methylation. Transformed cells undergo a dramatic change in their DNA methylation patterns: certain CpG islands located in the promoter regions of tumor-suppressor genes become hypermethylated and the contiguous gene rests silenced and this phenomenon occurs in an overall genomic environment of DNA hypomethylation. The profile of CpG island hypermethylation in hematologic malignancies is an epigenetic signature unique for each subtype of leukemia or lymphoma. Although the most widely studied genes are the cell-cycle inhibitors p15INK4b and p16INK4a (specially in AML and ALL), the list of methylation-repressed genes in these neoplasms is expanding very rapidly, including MGMT, RARB2, CRBP1, SOCS-1, CDH1, DAPK1, and others. A necessary cross-talk between genetic alterations and DNA methylation exists: certain chromosomal translocations may induce hypermethylation, such as the PML-RARa, or attract methylation, such as BCR-ABL, but DNA hypomethylation can be the culprit behind the genesis of certain abnormal recombination events. From a translational standpoint, hypermethylation can be used as a marker of recurrent disease or progression, for example, in MDS, or response to chemotherapy, such as MGMT methylation in B-cell non-Hodgkin's lymphoma. Furthermore, promising studies using DNA demethylating agents and histone deacetylase inhibitors are underway to awake these dormant tumor-suppressor genes for a better treatment of the patient with a hematologic malignancy.
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PMID:Profiling aberrant DNA methylation in hematologic neoplasms: a view from the tip of the iceberg. 1458 79

The human O(6)-methylguanine-DNA methyltransferase (MGMT) gene and its mutants have been used for in vivo selection of transduced hematopoietic stem cells with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) alone or in combination with O(6)-benzylguanine (BG). To allow similar in vivo selection in dogs, without the risk of inducing an immune response, we have cloned the canine MGMT drug resistance gene. Comparison of canine and human MGMT-coding regions indicates that there is about 62% amino acid identity and 78% similarity between the two MGMTs. The canine MGMT is also longer, by nine amino acids. Proline at position 140 and the surrounding amino acids of the human MGMT are highly conserved in the canine sequence. To determine whether mutation of the proline residue at position 144 to lysine in the canine MGMT would provide a similar advantage for selection of transduced cells as the human mutant, Moloney murine leukemia virus and human immunodeficiency type 1 vectors encoding the corresponding mutant MGMT were created and used to express separately canine and human MGMTs in cultured cells. Drug resistance assays using BCNU alone or BCNU with BG demonstrated that the wild-type and mutant canine MGMTs provided resistance to the selection agents that was comparable to the human MGMT counterparts.
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PMID:Cloning and expression of canine O6-methylguanine-DNA methyltransferase in target cells, using gammaretroviral and lentiviral vectors. 1505 63

Using a candidate gene approach, we analyzed the methylation status of the promoter-associated CpG islands of 11 well-characterized tumor suppressor genes by methylation-specific polymerase chain reaction in five multiple myeloma (MM) cell lines and 56 patients with malignant plasma cell disorders. The frequency of aberrant methylation among the patient samples was 46.4% for SOCS-1, 35.7% for p16, 21.4% for E-cadherin, 12.5% for DAP kinase and p73, 1.8% for p15, MGMT as well as RARbeta, and 0% for TIMP-3, RASSF1A and hMLH1. We found at least one hypermethylated gene in 80.4% of the primary patient samples, while 33.9% harbored two or more hypermethylated genes. For the first time, we show that p73 may be hypermethylated in MM and thus be involved in the pathogenesis of plasma cell disorders. Hypermethylation of p16 at diagnosis was associated with a poorer prognosis. In patients with plasma cell leukemia, we found frequent simultaneous hypermethylation of p16, E-cadherin and DAP kinase. We conclude that aberrant methylation of tumor suppressor genes is a common event in malignant plasma cell disorders and that there is a correlation between methylation patterns and clinical characteristics in MM patients.
Leukemia 2004 Oct
PMID:DNA methylation changes in multiple myeloma. 1531 45

Anti-tumour activity of triazene compounds of clinical interest [i.e. dacarbazine and temozolomide (TMZ)] relies mainly on the generation of methyl adducts to purine bases of DNA. Two DNA repair enzyme systems, i.e. the O6-guanine-alkyl-transferase (MGMT) and mismatch repair (MMR), play a predominant role in conditioning the cytotoxic effects of triazenes. In particular, high levels of MGMT associated with target cells are responsible of resistance to triazenes. On the contrary, the presence of MMR is required for the cytotoxic effects of these compounds. Previous studies performed by our group and a more recent clinical investigation reported by Karen Seiter, pointed out that triazene compounds could play an important role in the treatment of refractory acute leukaemia. Leukaemia blasts, especially of lymphoblastic leukaemia, show frequently high levels of MGMT activity. Therefore, it reasonable to hypothesize that combined treatment of leukaemia patients with triazene compounds along with MGMT inhibitors could lead to a better control of the disease. PaTrin-2 (O6-(4-bromothenyl)guanine, PAT) is a potent and scarcely toxic MGMT inhibitor recently introduced in clinical trials. This drug is used in combination with triazene compounds in order to augment their anti-tumour efficacy against neoplastic cells endowed with high MGMT activity. The present report describes, for the first time, pre-clinical in vitro studies on the cytotoxic activity of combined treatment with PAT+TMZ against long-term cultured leukaemia cells and primary leukaemia blasts obtained from patients with acute lymphoblastic leukaemia or acute myeloblastic leukaemia. The results point out that, both in long-term cultured leukaemia cell lines and in primary blast samples, PAT could improve dramatically the sensitivity of malignant cells to the cytotoxic effects of TMZ. This sensitizing effect is detectable when leukaemia cells show resistance mechanisms based on a MGMT-proficient phenotype. On the contrary, when resistance to TMZ is dependent on MMR deficiency, no influence of PAT can be detected in various experimental conditions. In conclusion, these results appear to provide disease-oriented rational basis to design novel clinical protocols for the treatment of acute leukaemia with combined administration of PAT and triazene compounds.
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PMID:O6-(4-bromothenyl)guanine (PaTrin-2), a novel inhibitor of O6-alkylguanine DNA alkyl-transferase, increases the inhibitory activity of temozolomide against human acute leukaemia cells in vitro. 1641 62

An acquired autoactivating mutation with a V617F amino-acid substitution in the JAK2 tyrosine kinase is frequently found in BCR/ABL-negative myeloproliferative disorders (MPD). Hypermethylation of CpG islands within gene promoter regions is associated with transcriptional inactivation and represents an important mechanism of gene silencing in the pathogenesis of hematopoietic malignancies. In this study, we determined the DNA methylation status of 13 cancer-related genes in the context of JAK2 mutations in 39 patients with MPD. Genes analyzed for hypermethylation were SOCS-1, SHP-1, E-cadherin, MGMT, TIMP-2, TIMP-3, p15, p16, p73, DAPK1, RASSF1A, RARbeta2 and hMLH1. We found at least one hypermethylated gene in 15/39 MPD patient specimens, and in 6/39 samples aberrant methylation of the negative cytokine regulator SOCS-1 was present. The JAK2V617F mutation was found in 21/39 patients as determined by allele-specific polymerase chain reaction. Hypermethylation of SOCS-1 was observed in 3/21 patients with an autoactivating JAK2 mutation and in 3/18 patients with wild-type JAK2. Our results suggest that epigenetic inactivation of SOCS-1 may be a complementary mechanism to the JAK2V617F mutation in the pathogenesis of MPD that leads to dysregulation of JAK-STAT signal transduction and thus contributes to growth factor hypersensitivity.
Leukemia 2007 Mar
PMID:Epigenetic alterations complement mutation of JAK2 tyrosine kinase in patients with BCR/ABL-negative myeloproliferative disorders. 1723 Feb 31


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