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At least 343 records · Page 19Linked to original sources
PubMed1997

Current challenges in cancer gene therapy.

The ability to transfer novel genes into mammalian cells has allowed us to conceive of novel strategies towards cancer therapy. Since the initial gene-transfer clinical trial in 1989, over 300 cancer patients have been enrolled in gene therapy trials. Despite this, an NIH-sponsored panel concluded that 'clinical efficacy has not been definitively demonstrated at this time in any gene therapy protocol'. However, the first 8 years of gene therapy research have provided us with insights regarding the areas that require further scientific progress. For example, it is now clear that while in vitro assays of gene-modified haemotopoietic progenitor cells suggest high transduction efficiencies, once these cells are infused in vivo, only a small percentage of circulating transduced cells can be detected. While the initial clinical studies have demonstrated that gene transfer in patients can be safe and feasible, they have also indicated that future research is necessary towards the development of improved gene transfer techniques for these approaches to be successful.

Animals↗
PubMed2000

The prospects for cancer gene therapy.

Gene therapy is a flexible technology with which to look for new ways of inhibiting cancer. However, the marginal success achieved has made it clear that direct engineering of cancer cells is more complex than had been supposed. The main barriers are raised by the difficulty of securing gene delivery into cancer cells in vivo and the selective advantages of those against which it is ineffective. These drawbacks do not arise when an immunological approach is adopted. Genes coding for tumor-associated peptides are used to engineer professional antigen presenting cells (APC). Alternatively APC pulsed with tumor antigens are engineered to overexpress costimulatory molecules or release cytokines. A more conservative approach is to engineer whole tumor cells with costimulatory and MHC molecules. Tumor cells can also be engineered to secrete cytokines and chemokines. The sustained presence of these factors in the tumor microenvironment recruits and activates distinct repertoires of APC and skews the antitumor response towards Th1 or Th2 reactivity. Engineered tumor cells are quickly rejected while mice acquire an immune memory against subsequent challenges, even when the tumor involved is poorly immunogenic. They also cure mice bearing incipient tumors and small metastases. This efficacy, however, vanishes as the tumor progresses. Even the best-induced specific immunity, therefore, is of no avail against advanced tumors. By contrast, the experimental data endorse the rational expectation that cancer vaccines will soon be both an established treatment of minimal disease after conventional management and a way of securing preventive antitumor vaccination.

Animals↗
PubMedDate not supplied

Exogenous wt-p53 protein is active in transformed cells but not in their non-transformed counterparts: implications for cancer gene therapy without tumor targeting.

BACKGROUND: Expression of exogenous wild-type p53 (wt-p53) protein in tumor cells can suppress the transformed phenotype whereas it does not apparently induce detrimental effects in non-transformed cells. This observation may provide a molecular basis for p53-mediated gene therapy of p53-sensitive cancers without the need for tumor targeting. METHODS: To understand the molecular mechanisms responsible for this different behavior in tumor versus normal cells, biochemical and functional analyses of exogenous wt-p53 protein were performed on non-transformed C2C12 myoblasts and their transformed counterparts, the C2-ras cells. RESULTS: The exogenous wt-p53 protein, which induced persistent growth arrest only in transformed C2-ras cells, was shown to be significantly more stable in transformed than in non-transformed cells. This different stability was due to different p53 proteolytic degradation. Moreover, constitutively, exogenous wt-p53 protein was found to be transcriptionally active only in C2-ras cells but it could also be activated in C2C12 cells by genotoxic damage. CONCLUSIONS: Non-transformed C2C12 cells present regulatory system(s) which control the expression and the activity of exogenously expressed wt-p53 protein probably through degradation and maintenance in a latent form. This regulatory system is lost/inactivated upon transformation.

Adenoviridae↗
PubMed1998

An evaluation of common breast cancer gene mutations in a population of Ashkenazi Jews.

OBJECTIVES: In view of the recent reports of recurrent mutations in BRCA1 and BRCA2 in the Ashkenazi Jewish population, we have undertaken to assess the frequency of these mutations in this population attending for genetic counselling and risk assessment of familial breast cancer. DESIGN: Mutation screening for the 185delAG and the 5382insC mutations in BRCA1 and the 6174delT mutation in BRCA2 was performed on DNA samples from either subjects affected by breast or ovarian cancer or obligate gene carriers. The likelihood of the cancers being hereditary in each family was calculated. SUBJECTS: Blood samples were obtained from 26 affected subjects or obligate gene carriers from 23 Ashkenazi Jewish families, all with a history of either early onset breast or ovarian cancers, or multiple cases of breast or ovarian cancer. RESULTS: Twelve mutations have been identified in the 23 families (52%) of which eight (67%) were the 185delAG mutation, three (25%) were the 6174delT mutation, and one (8%) was the 5382insC mutation. While the majority of these mutations were identified in families with a greater than 50% probability of being hereditary under the CASH segregation model, three mutations were identified in families with a 35% or less probability. CONCLUSIONS: Genetic screening of the recurrent mutations in Ashkenazi Jewish families will lead to the availability of predictive testing in a reasonably large proportion, even if the family history of breast/ovarian cancer is not particularly strong. In our view it is possible to reassure high risk unaffected members of these families, if the screening is negative for these mutations, even if a sample from an affected member of the family is unavailable for previous screening.

Adult↗
PubMed1999

Public health aspects of breast cancer gene testing in Canada. Part 1: risks and interventions.

The risks (penetrance) of breast and ovarian cancer in carriers of the BRCA1 or BRCA2 genes are high, but it is likely that estimates based on selected large multicase families are inflated by selection bias. Estimates based on a population survey of Ashkenazi Jews are lower, but other population-based estimates are still not available. The proportion of breast or ovarian cancers related to the genes is similarly lower in population-based samples than in referred selected families, and, even for subjects with cancer onset at young ages or with a family history, it is quite small. Other genes with lower prevalence are also important, and there is evidence of some gene environmental interactions. The management of female BRCA gene carriers includes intensive surveillance, prophylactic surgery and the use of tamoxifen. Apart from screening justified by randomized trials in the general community, such as mammography, recommendations for surveillance and prophylactic surgery are based only on expert opinion, and there has been little consideration of risk-benefit or cost-benefit comparisons. Tamoxifen reduced breast cancer incidence in one trial of high-risk women, but not in two other smaller trials, and the effect on mortality has not been determined. The limitations of genetic testing, and particularly of intervention strategies, deserve close scrutiny.

Adult↗
PubMed2006

p51/p63, a novel p53 homologue, potentiates p53 activity and is a human cancer gene therapy candidate.

BACKGROUND: p51 (p73L/p63/p40/KET), a recently isolated novel p53 homologue, binds to p53-responsive elements to upregulate some p53 target genes and has been suggested to share partially overlapping functions with p53. p51 may be a promising candidate target molecule for anti-cancer therapy. METHODS: In this study, we adenovirally transduced p51A cDNA into human lung, gastric and pancreatic cancer cells and analyzed the intracellular function of p51 in anti-oncogenesis in vitro and in vivo. RESULTS: Overexpression of p51A revealed an anti-proliferative effect in vitro in all the cancer cells examined in this study. The anchorage-dependent and -independent cell growth of EBC1 cells carrying mutations in both p51 and p53 was suppressed and significant apoptosis following adenoviral transduction with p51 and/or p53 was seen. This growth suppression was cooperatively enhanced by the combined infection with adenoviral vectors encoding both p51 and p53. Furthermore, p51 activated several, but not all, p53-inducible genes, indicating that the mechanisms controlling p51- and p53-mediated tumor suppression differed. CONCLUSIONS: Our observations indicate that, although p51 exhibited reduced anti-oncogenetic effects compared with p53, it cooperatively enhanced the anti-tumor effects of p53. Our results suggest that p51 functions as a tumor suppressor in human cancer cells in vitro and in vivo and may be useful as a potential tool for cancer gene therapy.

Adenoviridae↗
PubMed2005

Enhanced efficiency and specificity of ovarian cancer gene therapy in rats with a novel nonviral gene delivery system (GE7) via intraovarian artery perfusion approach.

Transfer of the herpes simplex virus type I-thymidine kinase gene, followed by the administration of ganciclovir (HSV1-tk/GCV) into ovarian cancer-derived cell line either in vitro or transplanted into nude mice has been shown to provide a potential strategy for the gene therapy of ovarian cancer. We investigated the antitumor effects of HSV1-tk/GCV strategy with a chemically induced rat ovarian cancer model and a tumor-selective gene delivery by a novel nonviral gene delivery system (GE7) through the ovarian artery and tail vein. We demonstrated the expression of a reporter gene, beta-gal gene, as well as HSV1-tk gene in tumors and other organs, evaluated the overall antitumor effects after the GCV treatment and analyzed the tumor cell cycle phase distribution. Via the ovarian artery route, the expressions of beta-gal and HSV1-tk in tumors were significantly stronger than those expressed in such organs as the hearts, livers, spleens, lungs and kidneys. However, no beta-gal and HSV1-tk were detected in the tumor tissues when administrated via the tail vein, and little was found in other organs. The cell cycle analysis showed that the total S-phase of tumor cells in the test intra-arterial treatment group was considerably higher than that of the controls. The weight of the tumor tissues in the group treated by the intra-arterial route (4.06+/-2.12 g) was much less than the group treated intravenously (18.25+/-8.34 g) (P<.01). These findings indicated that the administration of GE7/HSV1-tk complex via the ovarian artery route could be a promising avenue of future human ovarian cancer treatment.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1983

Cancer genes in man.

We may conclude, from all of these considerations, that the burden of cancer falls unequally upon a population of individuals. Some normal persons develop cancer as a result of bad luck; they are victims of spontaneous processes or background processes such as gene mutation or chromosomal rearrangement. Others are susceptible because they are exposed to environmental agents that increase these background rates. But there are individuals who are predisposed to cancer because they carry mutations that are already on the path to cancer or carry genes that increase the prospect that such mutation will occur, either spontaneously or in response to an environmental agent. It is even possible that most environmental cancer also involves genetic predisposition.

Ataxia Telangiectasia↗
PubMed2002

Prostate cancer gene therapy: past experiences and future promise.

Gene therapy has been used to target prostate cancer with excellent pre-clinical efficacy but limited clinical efficacy. The concept of delivering genetic material to prostate cancer cells to alter their phenotype and ultimately their behavior has been demonstrated in the laboratory over the last decade. Translating those pre-clinical findings into novel therapies for prostate cancer has been difficult. The stigma of gene therapy and the aggressive regulation of clinical trials involving transfer of genetic material to patients are two major impediments to clinical successes in gene therapy. This review hopes to provide a snapshot of prior gene transfer protocol findings and forecast the exciting future directions investigators are heading.

Animals↗
PubMed2005

Short interfering RNAs as a tool for cancer gene therapy.

There are mainly two types of short RNAs that target complementary messengers in animals: small interfering RNAs and micro-RNAs. Both are produced by the cleavage of double-stranded RNA precursors by Dicer, a member of the Rnase III family of double-stranded specific endonucleases, and both guide the RNA-induced silencing complex to cleave specifically RNAs sharing sequence identity with them. In designing a particular RNA interference (RNAi), it is important to identify the sense/antisense combination that provides the most potent suppression of the target mRNA, and several rules have been established to give >90% gene expression inhibition. RNAi technology can be directed against cancer using a variety of strategies. These include the inhibition of overexpressed oncogenes, blocking cell division by interfering with cyclin E and related genes or promoting apoptosis by suppressing antiapoptotic genes. RNAi against multidrug resistance genes or chemoresistance targets may also provide useful cancer treatments. Studies investigating these approaches in preclinical models are also reviewed.

Apoptosis↗
PubMed1997

Frequency of germline hereditary non-polyposis colorectal cancer gene mutations in patients with multiple or early onset colorectal adenomas.

BACKGROUND: The hereditary non-polyposis colorectal cancer (HNPCC) syndrome is caused by germline mutations in mismatch repair genes and predisposes individuals to cancers of the colon and other specific sites. On theoretical grounds, it is expected that patients with HNPCC also develop more colorectal adenomas than the general population. In essence, if the mutation rate is raised owing to mutations at a mismatch repair locus, more mutations are expected at loci such as APC (adenomatous polyposis coli) and more adenomas will start to grow. Not all data support this expectation, however. AIM: To search for germline mutations at HNPCC loci in patients with multiple adenomas. SUBJECTS: Twenty five patients (without known APC mutations) who have developed colorectal adenomas in unusually large numbers and, in some cases, at an early age. METHODS: Germline APC mutations were excluded using the protein truction test for exon 15 and mismatch chemical cleavage analysis for remaining exons. Germline HNPCC mutations were detected by using PCR and single strand conformation polymorphism analysis. RESULTS: Just one germline HNPCC mutation was found (4% of cases) and this was of uncertain functional effect. CONCLUSIONS: In general, germline HNPCC mutations are not responsible for the phenotype of patients with multiple colonic adenomas. It is possible that patients with HNPCC tend to develop adenomas more frequently and earlier than the general population, but that this effect is relatively subtle. These results suggest that individuals with colorectal adenomas only should not strictly be classified as "affected" in HNPCC families (although they should certainly not be classified as "unaffected" either and may warrant intensive screening). In the absence of a personal or strong family history of colorectal cancer, it is probably not worthwhile performing diagnostic or predictive genetic testing for HNPCC mutations in subjects with colorectal adenomas. Although undetected APC mutations may be responsible for some of the phenotypes in this sample, as yet uncharacterised adenoma predisposing genes probably exist.

Adenoma↗
PubMed2003

Watching the race to find the breast cancer genes.

This article focuses on a crucial development in genetic research that occurred in the 1990s: the identification of the first two of the genes responsible for hereditary breast and ovarian cancer (BRCA1 and BRCA2). Issues addressed touch on the evolution of the subfield, its potential impact on cancer treatment, and industry involvement. The article follows the activities of the various research groups competing in the race to identify the genes and depicts the frequent conflicts between them. Data are derived chiefly from a bibliometric database. The results show a diversity of research practices. Industrial researchers interacted within far more tightly knit networks than their counterparts working in public organizations. The patenting and commercial exploitation of results led to fierce battles, with one group capturing most of the benefits.

Bibliometrics↗
PubMed2005

Adeno-associated virus 2-mediated intratumoral prostate cancer gene therapy: long-term maspin expression efficiently suppresses tumor growth.

Maspin is a member of the serine protease inhibitors and the maspin gene, a tumor suppressor gene, is down-regulated in a large fraction of prostate cancers. We evaluated the use of adeno-associated virus (AAV, serotype 2) vector encoding maspin as a means for in vivo gene therapy for human prostate cancer. TUNEL assay of subcutaneously formed LNCaP or DU145 tumors in nude mice showed that intratumoral AAV-mediated maspin expression significantly upregulated the number of apoptotic cells compared with AAV-LacZ treatment. Immunofluorescence double staining for maspin protein and apoptosis in LNCaP tumors showed that the percentage of apoptotic cells in AAV-maspin-mediated maspin-expressing cells was significantly high compared with that in AAV-GFP-mediated GFP-expressing cells. Moreover, significantly fewer CD31-positive microvessels were observed in AAV-maspin-treated tumors compared with the control tumors. These therapeutic responses were highly correlated to persistent maspin expression in tumors, confirmed by Western blot analysis until at least day 56 after treatment. Finally, intratumoral delivery of AAV-maspin significantly suppressed growth of LNCaP and DU145 tumors and improved survival of mice. We conclude that AAV-mediated prolonged maspin expression efficiently suppresses human prostate tumor growth in vivo by apoptosis induction and inhibition of angiogenesis.

Animals↗
PubMed2003

Restoring apoptosis as a strategy for cancer gene therapy: focus on p53 and mda-7.

Understanding the molecular and genetic determinants of cancer will provide unique opportunities for developing rational and effective therapies. Malignant cells are frequently resistant to chemotherapy and radiation induced programmed cell death (apoptosis). This resistance can occur by mutations in the tumor suppressor gene p53. Strategies designed to replace this defective tumor suppressor protein, as well as forced expression of a novel cancer specific apoptosis inducing gene, melanoma differentiation associated gene-7 (mda-7), offer promise for restoring apoptosis in tumor cells. Conditional-replicating viruses that selectively induce cytolysis in tumor cells provides an additional means of targeting cancer cells for destruction. Although these approaches represent works in progress, future refinements will in all likelihood result in the next generation of cancer therapies.

Adenoviridae↗
PubMed1997

Mutation testing of early-onset breast cancer genes BRCA1 and BRCA2.

BRCA1 and BRCA2, genes predisposing to early-onset breast cancer, have been isolated and are characterized for mutation spectrum, risks of cancer, and function. The different methodologies to screen for mutations in BRCA1 and BRCA2 are briefly discussed including DNA-based methodologies and potential new assays. The numbers and types of mutations identified to date are described, including the problems of ascribing risk to missense mutations. Recurring, possibly founding mutations have been identified in several populations including Ashkenazi Jews, Icelanders, Swedes, and African Americans. From population-based studies, estimates are that 6%-10% of breast cancers are due to mutations in BRCA1 and BRCA2. Knowledge of mutation status raises additional questions including the interpretation of negative tests and the risks of breast and other cancers associated with positive test results.

Age of Onset↗
PubMedDate not supplied

Generation of expression plasmids for angiostatin, endostatin and TIMP-2 for cancer gene therapy.

Antiangiogenic therapy may represent a promising approach to cancer treatment. Indeed, the efficacy of endogenous angiogenesis inhibitors, including angiostatin, endostatin and TIMPs, has been demonstrated in many types of solid tumors in animal models. In view of the possible problems associated with long-term administration of inhibitors as recombinant proteins, we propose their delivery as nucleic acids through a gene therapy approach. To this end, eukaryotic expression constructs for murine angiostatin and endostatin as well as human TIMP-2 were generated, and characterized in vitro. All constructs carry the relevant cDNAs under the control of the strong HCMV promoter/enhancer, and cleavable leader signals to allow protein secretion. Expression of the angiogenesis inhibitors was detected by in vitro transcription/translation experiments as well as transfection of 293T cells, followed by Western blotting (WB) or radioimmunoprecipitation analysis of both cell lysates and supernatants (SNs). These constructs might be used for in vivo intramuscular delivery of plasmid DNA and as a set of reagents for the development of retroviral as well as adeno-associated viral (AAV) vectors expressing angiogenesis inhibitors.

Angiogenesis Inhibitors↗
PubMed1997

The breast cancer gene product TSG101: a regulator of ubiquitination?

Sequence analysis is a powerful tool to obtain structural and functional information about genes and their products. Here we show that TSG101, a gene subjected to somatic mutations in breast cancer, contains an amino terminal domain that is a homologue of ubiquitin conjugating enzymes (UBCs) and not, as previously proposed, DNA-binding domains. As the UBC active site residue is replaced in the TSG101 sequence in a similar manner to several other members of the UBC family, we propose a role for TSG101 in regulating the ubiquitination of short-lived gene products.

Amino Acid Sequence↗