O6-Alkylguanine-DNA alkyltransferase: influence on susceptibility to the genetic effects of alkylating agents

Mammalian cis-reporting plasmid may alter activities due to the derivation of host Escherichia coli strains

Methylation status of CpG dinucleotides in the promoter/regulatory region contributes to regulation of transcriptional activities of downstream genes. Nearly all plasmid vectors used in mammalian cells are generated from transformed Escherichia coli. However, these E. coli hosts may have different DNA methylation activities. For instance E. coli JM109 and DH5alpha contain Dam and Dcm methylases, which are absent in E. coli JM110 and GM2163. It has not been determined whether plasmids propagated from E. coli of different methylation activities result in altered expression in mammalian cells when transient transfection is conducted. In this report, cis-reporting plasmids were tested. When promoter/enhancer of tested plasmids contained several Dam/Dcm sites, the cis-reporting activity was 2 to 3 fold lower for those plasmids isolated from JM109 than from JM110. In contrast, the E. coli-derived methylation had little effect on transcription when the sites of methylation resided in the coding region. These findings suggest that cis-reporting plasmids used in comparative or successive experiments are required to be derived from the E. coli strain of the same methylation status. The plasmid for promoter-transcription factor studies should be Dam/Dcm negative E. coli strain.

Lack of association between Caucasian lung cancer risk and O6-methylguanine-DNA methyltransferase-codon 178 genetic polymorphism

The formation of DNA adducts is thought to be a critical step for the induction of chemically induced cancer. O(6)-Methylguanine-DNA methyltransferase (MGMT) is a ubiquitously expressed enzyme that repairs DNA adducts formed by alkylating carcinogens. Thus, genetic polymorphisms of the MGMT that could result in differences in MGMT activity are potential risk factors for cancer. In the present study, we established a convenient and reliable genotyping method for the MGMT codon 178 polymorphism, a Lys (AAG) to Arg (AGG) substitution, using restriction fragment length polymorphism (RFLP), and studied differences in the distribution of this polymorphism in 92 Caucasian lung cancer patients and 85 controls. Frequencies of the "A" and "G" alleles (MGMT codon 178, AAG and AGG, respectively) were 0.91 and 0.09, respectively. The genetic polymorphism of the MGMT codon 178 was linked with that of the MGMT codon 143 (P < 0.05). The distribution of the MGMT codon 178 genetic polymorphism was not significantly different between lung cancer patients and controls. Thus, our study suggests that the MGMT codon 178 (and possibly 143) polymorphisms do not appear to markedly affect lung cancer risk for this population. In addition, we found an apparent 10bp-deletion in the intron before exon 5 by DNA sequencing. Because this "deletion" was observed in all sequenced samples (N = 20), the previously reported human (Caucasian) MGMT gene sequence should be revised to exclude this 10bp segment.

Cutaneous T-cell lymphomas: a review with emphasis on new treatment approaches

Primary cutaneous T-cell lymphomas represent a wide variety of non-Hodgkin lymphomas that are characterized by a distinct clinical presentation. Advanced molecular and biological techniques have enhanced the recognition of cutaneous T-cell lymphomas. The most common subtypes of cutaneous T-cell lymphomas are the epidermotropic variants mycosis fungoides and Sézary syndrome. At present, a stage-adjusted therapy is the best concept available, since early aggressive treatment options did not improve the prognosis of patients with cutaneous T-cell lymphomas. Accurate diagnostic and clinical assessment as well as identification of prognostic factors provides a helpful basis for treatment strategies. Current medical literature on diagnosis, prognosis, and treatment is reviewed with emphasis on new biologic response-modifying treatment options.

Primary cutaneous lymphomas: a review with current treatment options

Primary cutaneous T- and B-cell lymphomas are a heterogenous group of diseases with varied clinical presentations and prognosis. The use of new molecular, histological, and clinical criteria have enhanced the recognition of primary cutaneous T- and B-cell lymphomas. Compared to their nodal counterpart they have a different clinical behavior and therefore require a different treatment approach. Independent predictive factors identified clinically, histologically, and by immunopheno- and immunogenotyping are essential to assess the appropriate treatment for each subtype. The European Organization for Research and Treatment of Cancer (EORTC) Cutaneous Lymphoma Study Group provide a classification of cutaneous lymphomas taking into account of the histological and molecular features. Based on this classification we will provide a summary of the current medical literature in diagnosis, treatment, and prognosis for primary cutaneous lymphomas with emphasis on new treatment strategies.