Development and characterization of reference materials for MTHFR, SERPINA1, RET, BRCA1, and BRCA2 genetic testing.

Well-characterized reference materials (RMs) are integral in maintaining clinical laboratory quality assurance for genetic testing. These RMs can be used for quality control, monitoring of test performance, test validation, and proficiency testing of DNA-based genetic tests. To address the need for such materials, the Centers for Disease Control and Prevention established the Genetic Testing Reference Material Coordination Program (GeT-RM), which works with the genetics community to improve public availability of characterized RMs for genetic testing. To date, the GeT-RM program has coordinated the characterization of publicly available genomic DNA RMs for a number of disorders, including cystic fibrosis, Huntington disease, fragile X, and several genetic conditions with relatively high prevalence in the Ashkenazi Jewish population. Genotypic information about a number of other cell lines has been collected and is also available. The present study includes the development and commutability/genotype characterization of 10 DNA samples for clinically relevant mutations or sequence variants in the following genes: MTHFR; SERPINA1; RET; BRCA1; and BRCA2. DNA samples were analyzed by 19 clinical genetic laboratories using a variety of assays and technology platforms. Concordance was 100% for all samples, with no differences observed between laboratories using different methods. All DNA samples are available from Coriell Cell Repositories and characterization information can be found on the GeT-RM website.

Development of genomic reference materials for cystic fibrosis genetic testing.

The number of different laboratories that perform genetic testing for cystic fibrosis is increasing. However, there are a limited number of quality control and other reference materials available, none of which cover all of the alleles included in commercially available reagents or platforms. The alleles in many publicly available cell lines that could serve as reference materials have neither been confirmed nor characterized. The Centers for Disease Control and Prevention-based Genetic Testing Reference Material Coordination Program, in collaboration with members of the genetic testing community as well as Coriell Cell Repositories, have characterized an extended panel of publicly available genomic DNA samples that could serve as reference materials for cystic fibrosis testing. Six cell lines [containing the following mutations: E60X (c.178G>T), 444delA (c.312delA), G178R (c.532G>C), 1812-1G>A (c.1680-1G>A), P574H (c.1721C>A), Y1092X (c.3277C>A), and M1101K (c.3302T>A)] were selected from those existing at Coriell, and seven [containing the following mutations: R75X (c.223C>T), R347H (c.1040G>A), 3876delA (c.3744delA), S549R (c.1646A>C), S549N (c.1647G>A), 3905insT (c.3773_3774insT), and I507V (c.1519A>G)] were created. The alleles in these materials were confirmed by testing in six different volunteer laboratories. These genomic DNA reference materials will be useful for quality assurance, proficiency testing, test development, and research and should help to assure the accuracy of cystic fibrosis genetic testing in the future. The reference materials described in this study are all currently available from Coriell Cell Repositories.

Promoter-controlled infectivity-enhanced conditionally replicative adenoviral vectors for the treatment of gastric cancer.

BACKGROUND: Gastric cancer is the fourth most common malignancy worldwide. Adenoviral vectors (Ads) have been applied for gene therapy of various cancers because of their high transduction efficiency. However, the infectivity of gastrointestinal cancer cells is poor due to the limited expression of the Coxsackie-adenovirus receptor (CAR). In addition, few tumor-specific promoters (TSPs) have been characterized for this type of cancer. To overcome these problems, we proposed TSP-driven conditionally replicating adenoviruses (CRAds) with fiber modification for virotherapy of gastric cancer. METHODS: We assessed the expression profile of eight TSPs in gastric cancer cell lines and evaluated promising candidates in the context of CRAd cytocidal effect. Next, infectivity enhancement by fiber modifications was analyzed in the gastric cancer cell lines. Finally, we combined the TSP-driven CRAds of choice with the fiber modifications to augment the killing effect. RESULTS: Out of the eight TSPs, the midkine (MK) and cyclooxygenase-2 (Cox-2M and Cox-2L) promoters showed high transcriptional activity in gastric cancer cells. When these promoters were used in a CRAd context, Cox-2 CRAds elicited the strongest cytocidal effect. The greatest infectivity enhancement was observed with adenoviral vectors displaying 5/3 chimeric fibers. Likewise, Cox-2 CRAds with 5/3 chimeric fibers showed the strongest cytocidal effect in gastric cancer cell lines. Therefore, Cox-2 CRAds with 5/3 chimeric fiber modification showed good selectivity and infectivity in gastric cancer cells to yield enhanced oncolysis. CONCLUSIONS: Cox-2 CRAds with 5/3 chimeric fiber modification are promising for virotherapy of gastric cancer.

The secretory leukoprotease inhibitor (SLPI) promoter for ovarian cancer gene therapy.

BACKGROUND: Adenoviruses allow efficient transduction of dividing and non-dividing cells and their safety for the treatment of cancer has been established in clinical trials. However, one disadvantage is their promiscuous tropism. In this regard, tissue-specific promoters (TSPs) could be useful for directing transgene expression to target tissues and for reducing adverse effects in non-target tissues. We hypothesize that selective adenovirus-mediated transgene expression could be achieved through the use of the secretory leukoprotease inhibitor (SLPI) promoter in the context of ovarian cancer. METHODS: Adenoviruses containing the SLPI promoter driving reporter and suicide gene expression were created and tested in ovarian cancer cell lines and primary tumor cells isolated from patients. To evaluate the in vivo activation of the SLPI promoter in comparison to a ubiquitous promoter, intraperitoneal delivery was performed in tumor-bearing mice, followed by analysis of survival or gene expression in normal organs and tumor. RESULTS: The SLPI promoter retained its fidelity in an adenoviral context and was activated in both cell lines and primary cancer cells. The SLPI promoter was induced to a high degree in ovarian cancer cells while showing significantly reduced activity in normal tissues. The therapeutic efficacy of SLPI promoter-controlled gene expression was similar to the ubiquitous promoter in vitro and in an orthotopic murine model of peritoneally disseminated ovarian cancer, with higher activity than controls. CONCLUSIONS: The SLPI promoter is a potentially useful TSP for ovarian cancer and facilitates further development of targeting strategies for improved gene therapy of ovarian carcinomas.

Replication of an integrin targeted conditionally replicating adenovirus on primary ovarian cancer spheroids.

Replication competent viruses hold promise for treatment of advanced cancers resistant to available therapeutic modalities. Although preliminary clinical results have substantiated their efficacy, preclinical development of these novel approaches is limited by assay substrates. The evaluation of candidate agents could be confounded by differences between primary tumor cells and tumor cell lines, as discordance in the levels of surface receptors relevant for viral entry has been reported. Since primary tumor cells are difficult to analyze ex vivo for longitudinal observation of virus replication, we developed three-dimensional aggregates or spheroids of unpassaged and purified ovarian cancer cells as a means for prolonging primary tumor cell viability and as a three-dimensional in vitro model for replicative viral infection. Ovarian cancer cells purified from ascites samples were sustained for 30 days while retaining the infection profile with tropism modified and unmodified adenoviruses (Ads). Cell line and primary cell spheroids were used to quantitate the replication and oncolytic potency of replicative Ads in preclinical testing for human ovarian cancer trials. Therefore, spheroids provide a method to sustain purified unpassaged primary ovarian cancer cells for extended periods and to allow evaluation of replicative viruses in a three-dimensional model.

CD40 is expressed on ovarian cancer cells and can be utilized for targeting adenoviruses.

PURPOSE: CD40, a member of the tumor necrosis factor receptor superfamily, is widely expressed on various cell types in addition to hematopoietic cells. Recent studies show that CD40 expression is related to several carcinomas, although its role in cancer pathobiology is unknown. In this study, we demonstrate the expression of CD40 on several ovarian carcinoma cell lines and the ability of CD40 to mediate targeted adenoviral infection in vitro. EXPERIMENTAL DESIGN: CD40 expression on ovarian cancer cell lines and clinical patient samples was examined by reverse transcription-PCR and flow cytometry. To study the utilization of CD40 for gene delivery, we precomplexed a luciferase coding adenovirus (Ad), Ad5luc1, with a CD40-targeting molecule (CAR/G28). RESULTS: According to our studies, all of the examined ovarian cancer cell lines are expressing CD40. In addition, mRNA for CD40 was detected in every primary tumor sample, suggesting that CD40 is also expressed in vivo. Compared with nontargeted Ad, gene transfer was increased up to 40-fold in CD40+ cells when CD40-targeted Ad was used. Supporting the relation of targeted system to CD40, increasing the amount of targeting fusion protein results in dose response. Furthermore, blockade of CD40 receptors on cell surface decreases the infectability of CD40+ cells with CD40-targeted virus, indicating the specificity of the targeting system for CD40. CONCLUSIONS: These results suggest that CD40 is present in ovarian cancer cells and can be used for targeted gene delivery in a CAR-independent manner, circumventing the problem of the low expression levels of CAR in various cancer cells.

Adenoviral gene therapy for cancer: from vectors to targeted and replication competent agents (review).

Gene therapy is an exciting novel approach for treating cancers resistant to currently available modalities. Treatment approaches are based on taking advantage of molecular differences between normal and tumor cells. Various strategies are currently in clinical development, with some promising early results reported with mutation compensation, molecular chemotherapy and replication competent viruses. Adenoviruses are among the most popular vehicles and there is a wealth of clinical data suggesting excellent safety for treatment of cancer patients. Current developments include improving targeting strategies for gene delivery to tumor cells with tumor specific promoters. Another rapidly developing field is replication competent agents, which allow improved tumor penetration and local amplification of the anti-tumor effect. Further, infectivity enhancement strategies can overcome variable expression of the primary adenovirus receptor on tumor cells, which may have reduced the clinical efficacy of previous strategies. Adenoviral cancer gene therapy approaches lack cross-resistance with other treatment options and frequently synergistic effects can be observed. Therefore, the first routine clinical applications are likely to be combination treatments.

Targeting adenovirus to the serotype 3 receptor increases gene transfer efficiency to ovarian cancer cells.

Gene delivery efficiency in clinical cancer gene therapy trials with recombinant adenoviruses (Ads) based on serotype 5 (Ad5) has been limited partly because of variable expression of the primary Ad5 receptor, the coxsackie and adenovirus receptor (CAR), on human primary cancer cells. As a means of circumventing CAR deficiency, Ad vectors have been retargeted by creating chimeric fibers possessing knob domains of alternate Ad serotypes. In this study, we have constructed an Ad5-based vector, Ad5/3luc1, with a chimeric fiber protein featuring a knob domain derived from Ad3. This virus is retargeted to the Ad3 receptor and, therefore, has different tissue tropism. A novel knob binding assay was used to measure expression of CAR and the Ad3 receptor. Further, to evaluate the correlation of receptor expression and infectivity by Ad, a panel of ovarian cancer cell lines and purified primary cancer cells were infected with Ad5luc1 and Ad5/3luc1 at 50, 200, and 1000 viral particles/cell. Our results confirm that Ad5/3luc1 is retargeted to the Ad3 receptor. Furthermore, the Ad3 receptor is present at higher levels than CAR on ovarian adenocarcinoma cells. Also, the amount of binding to primary receptor appears to be the major factor determining the efficiency of transgene expression. The Ad5/3 chimera displays enhanced infectivity for ovarian cancer cell lines and purified primary tumor cells, which could translate into increased efficacy in clinical trials.