Wei-dong Wang

CYP1A1 and GSTM1 polymorphisms and oral cancer risk: association studies via evidence-based meta-analyses.

Previous studies have implicated CYP1A1 and GSTM1 polymorphisms as risk factors for various cancers. A number of studies have been devoted to the association of CYP1A1 or GSTM1 polymorphism with susceptibility to oral carcinoma and have yielded conflicting results. The aim of the present study was to assess the possible associations of oral cancer risk with CYP1A1 genetic variation and GSTM1 null genotype respectively via systematic meta-analyses. The data suggest that variant genotypes of CYP1A1 might not be risk factors for oral cancer, whereas GSTM1 null genotype significantly increases susceptibility to oral cancer in Asians but not Caucasians.

Correlation between DNA Repair Capacity in Lymphocytes and Acute Side Effects to Skin during Radiotherapy in Nasopharyngeal Cancer Patients

Purpose: Repair of radiation-induced DNA damage plays a critical role for both the susceptibility of patients to side effects after radiotherapy and their subsequent cancer risk. The study objective was to evaluate whether DNA repair data determined in vitro are correlated with the occurrence of acute side effects during radiotherapy. Experimental Design: Nasopharyngeal cancer patients receiving radiation therapy were recruited in a prospective epidemiologic study. As an indicator for clinical radiosensitivity, adverse reactions of the skin were recorded. Cryopreserved lymphocytes from 100 study participants were γ-irradiated with 5 Gy in vitro and analyzed using the alkaline comet assay. Reproducibility of the assay was determined by repeated analysis (n = 22) of cells from a healthy donor. A coefficient of variation of 0.24 was calculated. Results: The various parameters determined to characterize the individual DNA repair capacity showed large differences between patients. Twenty-one patients were identified with considerably enhanced DNA damage induction, and 19 patients exhibited severely reduced DNA repair capacity after 15 and 30 minutes. Eight patients were considered as clinically radiosensitive, indicated by moist desquamation of the skin after a total radiation dose of 70 Gy. Conclusions: Using the alkaline comet assay as described here, nasopharyngeal cancer patients were identified showing abnormal cellular radiation effects, but this repair deficiency corresponded only at a very limited extent to the acute radiation sensitivity of the skin.

Enhanced efficacy of radiation‐induced gene therapy in mice bearing lung adenocarcinoma xenografts using hypoxia responsive elements

The aim of the present study was to investigate whether the hypoxia responsive element (HRE) could be used to enhance suicide gene (HSV‐tk) expression and tumoricidal activity in radiation‐controlled gene therapy of human lung adenocarcinoma xenografts. A chimeric promoter, HRE–Egr, was generated by directly linking a 0.3‐kb fragment of HRE to a 0.6‐kb human Egr‐1 promoter. Retroviral vectors containing luciferase or the HSV‐tk gene driven by Egr‐1 or HRE–Egr were constructed. A human adenocarcinoma cell line (A549) was stably transfected with the above vectors using the lipofectamine method. The sensitivity of transfected cells to prodrug ganciclovir (GCV) and cell survival rates were analyzed after exposure to a dose of 2 Gy radiation and hypoxia (1%). In vivo, tumor xenografts in BALB/c mice were transfected with the constructed retroviruses and irradiated to a total dose of 6 Gy, followed by GCV treatment (20 mg/kg for 14 days). When the HSV‐tk gene controlled by the HRE–Egr promoter was introduced into A549 cells by a retroviral vector, the exposure to 1% O2 and 2 Gy radiation induced significant enhancement of GCV cytotoxicity to the cells. Moreover, in nude mice bearing solid tumor xenografts, only the tumors infected with the hybrid promoter‐containing virus gradually disappeared after GCV administration and radiation. These results indicate that HRE can enhance transgene expression and tumoricidal activity in HSV‐tk gene therapy controlled by ionizing radiation in hypoxic human lung adenocarcinoma. (Cancer Sci 2005; 96: 918–924)

Cisplatin-controlled p53 gene therapy for human non-small cell lung cancer xenografts in athymic nude mice via the CArG elements.

Cisplatin, a commonly used chemotherapeutic agent, causes tumor cell death by producing DNA damage and generating reactive oxygen intermediates, which have been reported to activate the early growth response‐1 (Egr‐1) promoter through specific cis‐acting sequences, termed CArG elements. The aim of this study was to construct an adenoviral vector containing CArG elements cloned upstream of the cDNA for human wt‐p53, and to observe the effect of this vector on human non‐small cell lung cancer (NSCLC) xenografts in athymic nude mice when combined with cisplatin treatment. The adenoviral vector AdEgr–p53 was generated by inserting CArG elements upstream of human wt‐p53 cDNA. Two human NSCLC cell lines of varying p53 gene status, A549 (containing wild‐type p53) and H358 (containing an internal homozygous deletion of the p53 gene) were used for in vitro and in vivo experiments. Wt‐p53 production in cultured tumor cells and xenografts treated with the combination of AdEgr–p53 and cisplatin were detected by enzyme‐linked immunosorbent assays. The antitumor responses in nude mice with the A549 or H358 xenografts following treatment with AdEgr–p53 and cisplatin were observed. We found that p53 was produced in tumor cells and xenografts treated with a combination of AdEgr–p53 and cisplatin. Furthermore, the Egr‐1 promoter is induced by cisplatin, and this induction is mediated in part through the CArG elements. There was an enhanced antitumor response without an increase in toxicity following treatment with AdEgr–p53 and cisplatin, compared with either agent alone. Cisplatin‐inducible p53 gene therapy may provide a means to control transgene expression while enhancing the effectiveness of commonly used chemotherapeutic agents. This is a novel treatment for human NSCLC. (Cancer Sci 2005; 96: 706 – 712)

Detecting Normal Cell Radiosensitivity via Assay of DNA Damage in Lymphocytes for Individualizing Radiotherapy in Head and Neck Cancer Patients

PURPOSE The purpose of this study was to determine whether the distribution of radiosensitivities in normal tissues of head and neck cancer patients, measured using a DNA damage assay on lymphocytes, is likely to provide sufficient discrimination to enable reliable identification of patients with abnormal sensitivities. MATERIAL AND METHODS Radiosensitivity was assessed in 307 lymphocyte samples from unselected head and neck cancer patients and was quantified as the initial number of DNA double-strand breaks (dsb) induced per Gray and per DNA unit (200 Mbp). RESULTS The existence of an inter-individual variation in the radiosensitivity parameter is described by the range (0.41--9.38 dsb/Gy/DNA unit) of the values found. We detected 37 patients who developed severe skin reactions during radiotherapy treatment and we compared their radiosensitivity values with the remaining patients treated. Radiosensitivity values of >7.20 dsb/Gy/DNA unit should theoretically correspond to highly radiosensitive patients. CONCLUSIONS Our results suggest that initial DNA damage measured on lymphocytes offers an approach to predict the acute response of human normal tissues prior to radiotherapy. .

Construction and identification of synchronous nitric oxide-amplified gene circuits controlled by radiation

BACKGROUND It has been proven that the positive feedback gene circuits can increase the expression level of interested genes, and the synchronization of genetic circuits can further enhance the efficacy of gene therapy. In order to obtain an enhanced and prolonged gene expression in target cells, a radiation controlled positive feedback genetic circuit is constructed via linking the c-fos promoter with the inducible nitric oxide synthase (iNOS) cDNA, which can be synchronized by nitric oxide (NO) intercellular messenger. Ultimately, the efficacy of radiogenetic therapy for cancer will be improved. METHODS Using the gene recombination techniques, the vector pfos-iNOS/green fluorescent protein (GFP) was generated by cloning the radiation-responsive c-fos promoter into the plasmid vector pIRES2-EGFP to replace the primary CMV promoter, and then inserting human iNOS cDNA downstream of c-fos promoter in the vector pIRES2-EGFP. The constructed plasmids were then downloaded into A549 cells with lipofectamine. With exposure of various doses of ionizing radiation, outputs of GFP and iNOS in the treated cells were observed and analyzed. RESULTS The interested plasmid was successfully constructed, proved by restriction enzyme digestion analysis. The outputs of GFP and iNOS in the transfected cells were markedly increased compared with the control cells after radiation, the peak level was seen in 16 hours after radiation. CONCLUSIONS A positive feedback genetic circuit is successfully developed, composed by c-fos promoter and iNOS cDNA, which can be synchronized by secreting the intercellular messenger NO. This genetic circuit will be utilized in further study.

Retraction: Correlation between DNA Repair Capacity in Lymphocytes and Acute Side Effects to Skin during Radiotherapy in Nasopharyngeal Cancer Patients

To the Editor: The authors withdraw the article titled, “Correlation between DNA repair capacity in lymphocytes and acute side effects to skin during radiotherapy in nasopharyngeal cancer patients,” which appeared in the [ July 15, 2005][1], issue of Clinical Cancer Research ([1][2]). The first

[Experimental study on lung cancer-targeted oncostatin M gene therapy induced by ionizing radiation].

BACKGROUND To improve the efficacy and selectivity of gene therapy for lung cancer through inducing oncostatin M (OSM) gene expression by radiation via the early growth response gene-1 (Egr-1) promoter. METHODS The radio-inducible OSM gene was constructed by insertion of Egr-1 promoter into upstream of the OSM gene. The expression of OSM in lung adenocarcinoma cell line A549 which was transfected with pEO and exposed to different doses of γ-ray irradiation was analyzed, and the relative survival fraction of cells and cell survival curve were observed. To examine the efficacy of this pEO gene therapy in vivo, the tumor supression effects were investigated in 40 nude mice bearing lung tumors. RESULTS Expression of OSM gene in A549 cells transfected with pEO plasmids was markedly upregulated in a radiation dose-dependent manner. A gene therapy experiment in vitro showed that pEO transfected A549 cells became highly sensitive to ionizing radiation. pEO transfected tumors regressed significantly after a combination therapy with irradiation in all mice (n=10), and three tumors disappeared in 3 weeks without any side effect. CONCLUSIONS The results indicate that tumor targeted expression of OSM gene under the control of a radio-inducible promoter represents a novel strategy for safe and effective gene therapy for lung cancer and might be widely applied in the future.