Background aims. TissueGene-C (TG-C) represents a cell-mediated gene therapy for localized delivery of allogeneic chondrocytes expressing transforming growth factor (TGF)-β1 directly to the damaged knee joint. Untransduced human chondrocytes (hChonJ cells) have also been incorporated into the TG-C product at a 3:1 ratio with TGF-β1-expressing chondrocytes (hChonJb#7) in order to help fill in the defect and as target cells for the actions of the expressed TGF-β1.Methods.A phase I dose-escalating clinical trial was performed to evaluate the safety and biologic activity of TG-C in patients with advanced osteoarthritis of the knee joint (full thickness cartilage defect) that was refractory to existing non-operative therapies. Following a single intra-articular injection into the joint space of the damaged knee, patients were monitored for safety, and an evaluation was performed to assess the pharmacokinetics and biologic activity of TG-C.Results.There were no treatment-related serious adverse events. Swelling, effusion and minor localized reactions such as warming sensation or itching were observed in a dose-dependent manner at the injection site. Knee evaluation scores seemed to indicate a dose-dependent trend toward efficacy; however, patient numbers were not sufficient to determine statistical significance.Conclusions.Overall, there were no significant safety issues related to the administration of TG-C, with only some minor injection site reactions observed. Additionally, knee scoring analyzes indicated a possibility that TG-C may contribute to improvement of arthritic symptoms. More study is warranted to evaluate further the safety and determine the potential efficacy of TG-C.

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There have been major changes since the incidents of leukemia development in X-SCID patients after the treatments using retroviral gene therapy. Due to the risk of oncogenesis caused by retroviral insertional activation of host genes, most of the efforts focused on the lentiviral therapies. However, a relative clonal dominance was detected in a patient with β-thalassemia Major, two years after the subject received genetically modified hematopoietic stem cells using lentiviral vectors. This disappointing result of the recent clinical trial using lentiviral vector tells us that the current and most advanced vector systems does not have enough safety. In this review, various safety features that have been tried for the retroviral gene therapy are introduced and the possible new ways of improvements are discussed. Additional feature of chromatin insulators, co-transduction of a suicidal gene under the control of an inducible promoter, conditional expression of the transgene only in appropriate target cells, targeted transduction, cell type-specific expression, targeted local administration, splitting of the viral genome, and site specific insertion of retroviral vector are discussed here.

The recent incidents of leukemia development in X-SCID patients after a successful treatment of the disease with retroviral gene therapy raised concerns regarding the safety of the use of retroviral vectors in clinical gene therapy. In this review, we have tried to re-evaluate the safety issues related to the use of retroviral vectors in human clinical trials and to suggest possible appropriate solutions to the issues. As revealed by the X-SCID incident, oncogenesis caused by retroviral insertional activation of host genes is one of the most prominent risks. An ultimate solution to this problem will be in re-engineering retroviral vectors so that the retroviral insertion takes place only at the desired specific sites of the host cell chromosome. This is, however, a technically demanding tasks, and it will take years to develop retroviral vectors with targeted insertion capability. In the mean time, the use of chromatin insulators can reduce chances for retrovirus-mediated oncogenesis by inhibiting non-specific activation of nearby cellular proto-oncogenes. Co-transduction of a suicidal gene under the control of an inducible promoter could also be one of the important safety features, since destruction of transduced cells can be triggered if abnormal growth is observed. Additionally, conditional expression of the transgene only in appropriate target cells via the combination of targeted transduction, cell type-specific expression, and targeted local administration will increase the overall safety of the retroviral systems. Finally, splitting of the viral genome, use of self-inactivating (SIN) retroviral vectors, or complete removal of the coding sequences for gag, pol, and env genes is desirable to virtually eliminate the possibility of generation of replication competent retroviruses (RCR).

To evaluate contribution of polymorphisms of the XRCC1 gene to the risk of colorectal cancer, we conducted a case-control study of 209 colorectal cancer cases and 209 age-and gender-matched controls in the Korean population. We tested the hypothesis by constructing allele combinations with known SNP. Allelic variants of the XRCC1 gene at codons 194, 280 and 399 were analyzed in lymphocyte DNA by PCR-RFLP. We observed an increased risk of colorectal cancer associated with the 399Gln allele. The odds ratio (OR) was 1.61 (95% confidence interval [CI] 1.09-2.39) for the 399Gln allele. When combined allele-specific OR were calculated after estimating frequencies, 3 common allele combinations were found to be associated with an increased risk of colorectal cancer. The OR for the 194Trp-280Arg-399Arg was 1.48 (95% CI 5 1.06-2.07) using 194Arg-280Arg-399Arg as the reference. The OR for the 194Arg-280His-399Arg and the 194Arg-280Arg-399Gln were 1.78 (95% CI 5 1.09-2.89) and 1.78 (95% CI 5 1.23-2.59), respectively. Analysis after controlling for smoking, exercise and dietary habits indicated that alcohol consumption ( 80 g/week) is a significant risk factor of colorectal cancer (OR 5 2.60, 95% CI 5 1. 46-4.62). An increased risk for colorectal cancer was identified in alcohol drinkers with the risky allele combinations. Our results suggest that polymorphisms in the XRCC1 genes may contribute to colorectal cancer susceptibility, and some evidence was obtained of a genetic modification for the relationship between alcohol intake and colorectal cancer. ' 2005 Wiley-Liss, Inc.Key words: polymorphisms; XRCC1; genotype; allele; colorectal cancer; alcohol Colorectal cancer is one of the most commonly diagnosed cancers in North America and Western Europe, 1 and is the fourth most common cause of cancer in South Korea. 2 Inherited deficiencies in DNA repair have been associated with an individual's susceptibility to cancer. 3 Therefore, polymorphisms of DNA repair genes may increase the risk of colorectal cancer.The human XRCC1 gene, one of the DNA repair genes, was identified because of its ability to restore DNA repair activity in a Chinese hamster ovary mutant cell line EM9. 4 The XRCC1 protein is involved in base-excision repair, and interacts with DNA ligase III, DNA polymerase b, poly(ADP-ribose)polymerase (PARP), polynucleotide kinase and AP endonuclease I. 5-8 The base-excision repair pathway is designed to remove non-bulky base adducts, which are produced by methylation, oxidation or reduction by ionizing radiation or oxidative damage. 9,10 Three coding polymorphisms of the DNA repair gene XRCC1 (Arg194Trp, Arg280His and Arg399Gln) have been identified in man, suggesting altered efficiency due to amino acid substitutions. 11,12 Alcohol consumption has been associated with the production of reactive oxygen species, which are known to cause DNA lesions that can be removed by the DNA base-excision repair pathway. 13 Meta-analyses of alcohol consumption in relation to colorectal cancer have reported a small or moderate addit...

The purpose of this study was to investigate the efficacy of cartilage regeneration when using a mixture of transforming growth factor-beta1 (TGF-beta1)-producing human chondrocytes (hChon-TGF-beta1) and primary human chondrocytes (hChon) ("mixed cells"), compared with either hChon-TGF-beta1 or hChon cells alone. Specifically, mixed cells or hChon cells were first injected intradermally into the backs of immune-deficient nude mice to test the feasibility of cartilage formation in vivo. Both the mixed cells and the hChon-TGF-beta1 cells alone induced cartilage formation in nude mice, whereas hChon cells alone did not. To further test the efficacy of the cells in generating cartilage, an artificially induced partial thickness defect of the femoral condyle of a rabbit knee joint was loaded with hChon-TGF-beta1 cells with or without mixing additional untransduced hChon cells, and hyaline cartilage regeneration was observed at 4 or 6 weeks. The efficiency of complete filling of the defect and the quality of tissue generated after implanting were evaluated on the basis of a histological grading system modified from O'Driscoll et al. (J. Bone Joint Surg. 70A, 595, 1988). Significantly, mixed cells (14.2 +/- 0.9) produced significantly better results than hChon-TGF-beta1 (9.0 +/- 1.7) or hChon (8.0 +/- 1.8) cells alone. Histological and immunohistochemical staining of the newly repaired tissues produced after treatment with either mixed cells or hChon-TGF-beta1 cells alone showed hyaline cartilage- like characteristics. These results suggest that the implantation of mixed cells may be a clinically efficient method of regenerating hyaline articular cartilage.

The purpose of the investigation was to determine whether genetic polymorphisms in enzymes that metabolize exogenous chemicals modulate the effects of environmental tobacco smoke (ETS) exposure on birth weight. A survey was conducted from 2000 to 2001 among 266 pregnant women who were hospitalized for delivery and on their singleton live births. We determined maternal GSTM1 and GSTT1 polymorphisms by polymerase chain reaction and measured the urinary cotinine of pregnant women at delivery by radioimmunoassay. Birth weight was found to decrease significantly with increasing concentrations of maternal urinary cotinine (P < 0.05). The interactive effect of exposure to ETS and the presence of the GSTT1 polymorphism was found to be significant by multivariate analysis (P < 0.01), whereas the interactive effect of exposure to ETS and the presence of GSTM1 polymorphism did not reach statistical significance (P = 0.21). A combination of the GSTM1-null and the GSTT1 null-genotypes was found to exacerbate the effect of maternal exposure to ETS on birth weight more than the presence of either genotype alone. Our data indicate that maternal exposure to ETS negatively affects neonatal birth weight, and the adverse effect of maternal exposure to ETS on neonatal birth weight could be modified by the maternal metabolic genotypes, GSTM1 and GSTT1.

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