De-zhi Li

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.

Microarray-based analysis of microRNA expression in breast cancer stem cells

BackgroundThis study aimed to determine the miRNA profile in breast cancer stem cells (BCSCs) and to explore the functions of characteristic BCSC miRNAs.MethodsWe isolated ESA+CD44+CD24-/low BCSCs from MCF-7 cells using fluorescence-activated cell sorting (FACS). A human breast cancer xenograft assay was performed to validate the stem cell properties of the isolated cells, and microarray analysis was performed to screen for BCSC-related miRNAs. These BCSC-related miRNAs were selected for bioinformatic analysis and target prediction using online software programs.ResultsThe ESA+CD44+CD24-/low cells had up to 100- to 1000-fold greater tumor-initiating capability than the MCF-7 cells. Tumors initiated from the ESA+CD44+CD24-/low cells were included of luminal epithelial and myoepithelial cells, indicating stem cell properties. We also obtained miRNA profiles of ESA+CD44+CD24-/low BCSCs. Most of the possible targets of potential tumorigenesis-related miRNAs were oncogenes, anti-oncogenes or regulatory genes.ConclusionsWe identified a subset of miRNAs that were differentially expressed in BCSCs, providing a starting point to explore the functions of these miRNAs. Evaluating characteristic BCSC miRNAs represents a new method for studying breast cancer-initiating cells and developing therapeutic strategies aimed at eradicating the tumorigenic subpopulation of cells in breast cancer.

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.

Role of inhibitor of apoptosis protein Livin in radiation resistance in nonsmall cell lung cancer.

OBJECTIVE The objective of the present study was to explore the role of the inhibitor of apoptosis protein (IAP) Livin in radioresistance in nonsmall cell lung cancer (NSCLC). METHODS Lung adenocarcinoma cell lines A549 and SPC-A1 were used for this study. Using the technique of molecular cloning and gene transfection, two Livin isoforms, Livinα and β, respectively, were expressed in A549 cells with the purpose of exploring the role of Livin in radiation resistance of A549 cells. Moreover, a Livin-specific gene-silencing system was developed using SPC-A1 cell line with the purpose of increasing radiosensitivity of SPC-A1 cells. RESULTS A549 cells were induced by radiation to express Livin isoforms, Livinα and β. A549 cells expressed Livin isoforms stably after gene transfection and the transfected cells demonstrated characteristics of antiradiation. However, Livin gene-silenced SPC-A1 cells exhibited remarkably enhanced radiation sensitivity. CONCLUSION The IAP Livin is an important molecule in antiradiotherapy of NSCLC. Livin-specific gene silencing is likely to be an effective means to enhance radiation sensitivity of lung cancer.

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)

Induced cancer stem cells generated by radiochemotherapy and their therapeutic implications

Local and distant recurrence of malignant tumors following radio- and/or chemotherapy correlates with poor prognosis of patients. Among the reasons for cancer recurrence, preexisting cancer stem cells (CSCs) are considered the most likely cause due to their properties of self-renewal, pluripotency, plasticity and tumorigenicity. It has been demonstrated that preexisting cancer stem cells derive from normal stem cells and differentiated somatic cells that undergo transformation and dedifferentiation respectively under certain conditions. However, recent studies have revealed that cancer stem cells can also be induced from non-stem cancer cells by radiochemotherapy, constituting the subpopulation of induced cancer stem cells (iCSCs). These findings suggest that radiochemotherapy has the side effect of directly transforming non-stem cancer cells into induced cancer stem cells, possibly contributing to tumor recurrence and metastasis. Therefore, drugs targeting cancer stem cells or preventing dedifferentiation of non-stem cancer cells can be combined with radiochemotherapy to improve its antitumor efficacy. The current review is to investigate the mechanisms by which induced cancer stem cells are generated by radiochemotherapy and hence provide new strategies for cancer treatment.

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)

Regulation of miRNAs Affects Radiobiological Response of Lung Cancer Stem Cells

Radiotherapy (RT) is a key therapeutic strategy for lung cancer, the most common cause of cancer-related deaths worldwide, but radioresistance often occurs and leads to failure of RT. It is therefore important to clarify the mechanism underlying radioresistance in lung cancer. Cancer stem cells (CSCs) are considered the fundamental reason for radioresistance. MicroRNAs (miRNAs) have been regarded as important regulatory molecules of CSCs, carcinogenesis, and treatment response of cancers. It is crucial to clarify how regulation of miRNAs affects repair of DNA damage, redistribution, repopulation, reoxygenation, and radiosensitivity (5R) of lung cancer stem cells (LCSCs). A thorough understanding of the regulation of miRNAs affecting 5R of LCSCs has potential impact on identifying novel targets and thus may improve the efficacy of lung cancer radiotherapy.

Comparison of Total Body Irradiation Before and After Chemotherapy in Pretreatment for Hematopoietic Stem Cell Transplantation

OBJECTIVE To explore the best time to carry out total body irradiation (TBI) in hematopoietic stem cell transplantation (HSCT) pretreatment. METHODS Retrospective analysis was applied in 88 cases of HSCT using TBI as pretreatment from March 2001 to June 2009 in our hospital. Using 8 MV X-ray, all the patients were irradiated by linear accelerator in 2 consecutive days, with a total dose of 7-11 Gy and an instantaneous dose rate ranging between 4.0 and 5.0 cGy/min. Of the 88 cases, 40 cases were given traditional high-dose chemotherapy before TBI (Group CT/TBI), and 48 cases were given TBI before chemotherapy (Group TBI/CT) instead. RESULTS Eighty-seven cases of transplantation were successful, with no serious complications, including radiation pneumonia. Compared with Group CT/TBI, Group TBI/CT showed similar incidence of complications (p=0.08), similar recent chemotherapy toxicity (p=0.833), and significantly lower recent radiation toxicity (p=0.000). CONCLUSIONS TBI in the pretreatment of HSCT is safe and effective. Using TBI before the high-dose chemotherapy can maintain the same pretreatment effect, effectively reduce apparent immediate reaction/discomfort during TBI, reduce preparation workload of radiotherapy, and lower radiation side-effects. Further research is needed to expand its clinical application.

Effects of Berberine Against Radiation-Induced Intestinal Injury in Mice

PURPOSE Radiation-induced intestinal injury is a significant clinical problem in patients undergoing abdominal radiotherapy (RT). Berberine has been used as an antimicrobial, anti-inflammatory, and antimotility agent. The present study investigated the protective effect of berberine against radiation-induced intestinal injury. METHODS AND MATERIALS The mice were administrated berberine or distilled water. A total of 144 mice underwent 0, 3, 6, 12, or 16 Gy single session whole-abdominal RT and 16 mice underwent 3 Gy/fraction/d for four fractions of fractionated abdominal RT. Tumor necrosis factor-alpha, interleukin-10, diamine oxidase, intestinal fatty acid-binding protein, malonaldehyde, and apoptosis were assayed in the mice after RT. The body weight and food intake of the mice receiving fractionated RT were recorded. Another 72 mice who had undergone 12, 16, or 20 Gy abdominal RT were monitored for mortality every 12 h. RESULTS The body weight and food intake of the mice administered with distilled water decreased significantly compared with before RT. After the same dose of abdominal RT, tumor necrosis factor-alpha, diamine oxidase, intestinal fatty acid-binding protein in plasma and malonaldehyde and apoptosis of the intestine were significantly greater in the control group than in the mice administered berberine (p < .05-.01). In contrast, interleukin-10 in the mice with berberine treatment was significantly greater than in the control group (p < .01). A similar result was found in the fractionated RT experiment and at different points after 16 Gy abdominal RT (p < .05-.01). Berberine treatment significantly delayed the point of death after 20 Gy, but not 16 Gy, abdominal RT (p < .01). CONCLUSION Treatment with berberine can delay mortality and attenuated intestinal injury in mice undergoing whole abdominal RT. These findings could provide a useful therapeutic strategy for radiation-induced intestinal injury.