Eradication of murine mammary adenocarcinoma through HSVtk expression directed by the glucose-starvation inducible grp78 promoter

Gene therapy strategies employing the HSVtk/ganciclovir (GCV) suicide gene offer promising approaches towards the treatment of metastatic breast cancer. These include bystander effects on non-transduced tumor cells, lower systemic toxicity, and the possibility of inducing immunity against the tumor. Previously we have demonstrated the ability of the grp78 stress-inducible promoter to stimulate expression of reporter genes within the tumor microenvironment. However, experimental evidence demonstrating the ability of this promoter to activate therapeutic agents within the breast cancer environment causing tumor eradication is needed prior to clinical trials. In this report, we test the efficacy of the grp78 promoter in a retroviral system to drive the expression of the HSVtk suicide gene in a murine mammary adenocarcinoma cell line (TSA) in syngeneic, immune-competent hosts. Our results show that under glucose-starvation conditions in vitro, the expression of HSVtk and GCV induced cell death are enhanced in tumor cells in which the HSVtk gene is driven by the internal grp78 promoter compared to cells in which the Moloney murine leukemia virus LTR drives HSVtk. In in vivo studies, in tumors in which the HSVtk gene is driven by the grp78 promoter, GCV treatment causes complete tumor eradication, whereas tumors persist when the HSVtk gene is driven by the retroviral LTR. Our study suggests that the grp78 promoter may be useful to enhance the effectivity of therapeutic agents within a breast tumor. In addition, it is shown that immune memory is induced in syngeneic, immune-competent hosts. This new retroviral vector might therefore be useful for breast cancer gene therapy.     

双效逆转录载体的构建和受控自杀基因在乳腺癌细胞中表达的研究

目的：构建含有Tet-On基因调节系统及自杀基因HSVtk的重组逆病毒载体，研究其在乳腺癌细胞中HSVtk基因的受控表达。方法：用PCR方法扩增Tet-On基因，将其插入pRevTRE／HSVtk，形成重组载体pRevTRE／HSVtk／Tet-On。用脂质体介导法将pRevTRE／HSVtk／Tet-On导入乳腺癌细胞株(MCF-7)。经过HygromycinB筛选建立了一株稳定的受四环素衍生物强力霉素(Doxcycline，Dox)调控表达HSVtk基因的乳腺癌细胞株MCF／TRE／HSVtk／Tet-On。用RT-PCR的方法检测不同Dox浓度下HSVtk基因的表达，以MTT法检测不同Dox浓度下Ganciclovir(GCV)对乳腺癌细胞的杀伤作用。结果：成功构建了pRevTRE／HSVtk／Tet-On逆病毒载体。筛选出MCF／TRE／HSVtk／Tet-On细胞株，该细胞能在Dox的诱导下表达HSVtk基因并被GCV杀伤。结论：HSVtk基因产物可以将无毒性的Ganciclovir(GCV)转变成一种有毒的代谢产物，杀死乳腺癌细胞。而该基因的表达受到Tet-On调控，由强力霉素调节HSVtk基因表达。     

可调控重组腺相关病毒对MCF-7细胞基因转染效率及表达的研究

 目的 探讨Tet调控下自杀基因HSVtk重组腺相关病毒载体（rAAV/HSVtk/Tet-On）对人乳腺癌细胞株（MCF-7）的作用。方法 将HSVtk和Tet-On基因分别定向克隆入腺相关病毒质粒pAAV MCS中,构建重组腺相关病毒载体pAAV/TRE/HSVtk/Tet-On,与辅助质粒pAAV-RC、pHelper和包装细胞293进行包装、纯化。用β半乳糖苷酶原位染色法检测报告基因rAAV/LacZ在MCF-7中的表达,计算其基因转染效率。采用斑点杂交、RT-PCR检测MCF-7细胞基因组中HSVtk基因整合、病毒滴度及其表达。结果 rAAV/HSVtk/Tet-On病毒滴度为2.38×10^11particle/ml,LacZ基因在感染的MCF-7中能持续表达,感染效率为20%～30%。纯化后的重组腺相关病毒感染MCF-7后,能将目的基因转移到靶细胞中,并在Dox诱导下,使GCV对rAAV感染的MCF-7细胞具有明显的杀伤作用。结论 HSVtk/Tet-On自杀基因调控系统可通过重组腺相关病毒载体成功转染人乳腺癌细胞株MCF-7,使其HSVtkmRNA表达增加,在Dox诱导下,GCV对rAAV（≥10⁴v.p/cell）感染的MCF-7细胞具有明显的杀伤作用。     

Dexamethasone inhibits the HSV-<Emphasis Type="Italic">tk</Emphasis>/ ganciclovir bystander effect in malignant glioma cells

Background  

HSV-tk/ganciclovir (GCV) gene therapy has been extensively studied in the setting of brain tumors and largely relies on the bystander effect. Large studies have however failed to demonstrate any significant benefit of this strategy in the treatment of human brain tumors. Since dexamethasone is a frequently used symptomatic treatment for malignant gliomas, its interaction with the bystander effect and the overall efficacy of HSV-TK gene therapy ought to be assessed.     

人乳腺癌裸鼠移植瘤的体外抗生素诱导基因治疗

目的探讨Tet调控下体外抗生素诱导基因治疗人乳腺癌裸鼠移植瘤的可行性。方法构建人乳腺癌BALB/C裸鼠移植瘤模型,制备有感染活性的重组逆转录病毒RevTRE/HSVtk与RevTet-On。观察体外强力霉素(Dox)诱导,丙氧鸟苷(GCV)和逆转录病毒作用后移植瘤生长的变化及组织病理改变,分析其对乳腺癌裸鼠移植瘤的调控性治疗作用。结果乳腺癌裸鼠治疗后,肿瘤体积明显减小,生长受抑,生存周期延长,组间比较有显著性差异(P<0.05)。瘤体HE染色显示治疗组肿瘤局部有炎性细胞浸润和强嗜酸性细胞。RT-PCR结果显示Dox诱导后瘤体组织HSVtk表达较明显。结论通过逆转录病毒介导Tet调控,可以在体外抗生素Dox诱导下对人乳腺癌裸鼠移植瘤模型进行基因治疗,杀伤肿瘤细胞。     

可调控自杀基因的SCID小鼠乳腺癌基因治疗的研究

目的：探讨经强力霉素（Dox)诱导后，丙氧鸟苷（GCV）对SCID小鼠乳腺癌的调控性治疗作用。方法：重组逆转录病毒载体pRevTRE/HSVtk与pRevTet-On共转染乳腺癌细胞MCF－7，接种SCID小鼠成瘤后，腹腔内分别注射生理盐水（NS），GCV及Dox GCV治疗15d。观测肿瘤体积和组织病理改变及用RT－PCR分析肿瘤组织有无HSVtk的表达。结果：乳腺癌SCID小鼠Dox GCV治疗15d后，肿瘤体积明显减小，生长受抑，组间比较有显著性差异（P＜0．05）；HE染色发现治疗组肿瘤有局部坏死，炎性细胞浸润。RT－PCR结果显示Dox诱导后肿瘤组织HSVtk表达较明显。结论：在Dox的诱导作用下，GCV对可调控性自杀基因乳腺癌SCID小鼠有显著治疗作用。     

HDAC inhibitor valproic acid enhances tumor cell kill in adenovirus‐HSVtk mediated suicide gene therapy in HNSCC xenograft mouse model

Safety, efficacy and enhanced transgene expression are the primary concerns while using any vector for gene therapy. One of the widely used vectors in clinical trials is adenovirus which provides a safe way to deliver the therapeutic gene. However, adenovirus has poor transduction efficiency in vivo since most tumor cells express low coxsackie and adenovirus receptors. Similarly transgene expression remains low, possibly because of the chromatization of adenoviral genome upon infection in eukaryotic cells, an effect mediated by histone deacetylases (HDACs). Using a recombinant adenovirus (Ad‐HSVtk) carrying the herpes simplex thymidine kinase (HSVtk) and GFP genes we demonstrate that HDAC inhibitor valproic acid can bring about an increase in CAR expression on host cells and thereby enhanced Ad‐HSVtk infectivity. It also resulted in an increase in transgene (HSVtk and GFP) expression. This, in turn, resulted in increased cell kill of HNSCC cells, following ganciclovir treatment in vitro as well as in vivo in a xenograft nude mouse model.     

BAK overexpression mediates p53-independent apoptosis inducing effects on human gastric cancer cells

Background  

BAK (Bcl-2 homologous antagonist/killer) is a novel pro-apoptotic gene of the Bcl-2 family. It has been reported that gastric tumors have reduced BAK levels when compared with the normal mucosa. Moreover, mutations of the BAK gene have been identified in human gastrointestinal cancers, suggesting that a perturbation of BAK-mediated apoptosis may contribute to the pathogenesis of gastric cancer. In this study, we explored the therapeutic effects of gene transfer mediated elevations in BAK expression on human gastric cancer cells in vitro.     

Tumor-directed gene therapy in mice using a composite nonviral gene delivery system consisting of the piggyBac transposon and polyethylenimine

Background  

Compared with viral vectors, nonviral vectors are less immunogenic, more stable, safer and easier to replication for application in cancer gene therapy. However, nonviral gene delivery system has not been extensively used because of the low transfection efficiency and the short transgene expression, especially in vivo. It is desirable to develop a nonviral gene delivery system that can support stable genomic integration and persistent gene expression in vivo. Here, we used a composite nonviral gene delivery system consisting of the piggyBac (PB) transposon and polyethylenimine (PEI) for long-term transgene expression in mouse ovarian tumors.     

Photochemically enhanced gene transfection increases the cytotoxicity of the herpes simplex virus thymidine kinase gene combined with ganciclovir

Tumor targeting is an important issue in cancer gene therapy. We have developed a gene transfection method, based on light-inducible photochemical internalization (PCI) of a transgene, to improve gene delivery and expression selectively in illuminated areas, for example, in tumors. In the present work, we demonstrate that PCI improved the nonviral vector polyethylenimine (PEI)-mediated transfection of a therapeutic gene, the 'suicide' gene encoding herpes simplex virus thymidine kinase (HSVtk). In U87MG glioblastoma cells in vitro, the photochemical treatment stimulated expression of the HSVtk transgene, and, consequently, enhanced cell killing by the subsequent treatment with the prodrug ganciclovir (GCV). When relatively low doses of DNA (1 microg/ml) and the PEI vector (N/P 4) were used, HSVtk gene transfection followed by the GCV treatment did not have an effect on cell survival unless the photochemical treatment was performed, which potentiated the cytotoxicity to 90%. These findings indicate that photochemical transfection allows: (i) selective enhancement in gene expression and gene-mediated biological effects (cell killing by the Hsvtk/GCV approach) in response to illumination; (ii) the use of low, suboptimal for the nonviral transfection methods without PCI, doses of both DNA and the vector, which may be relevant and advantageous for therapeutic gene transfer in vivo.     

Suppression of murine mammary carcinoma growth and metastasis by HSVtk/GCV gene therapy using in vivo electroporation

The effectiveness of electroporation as a means of gene transfection, both in vitro and in vivo, was tested using the herpes simplex virus 1 thymidine kinase (HSVtk) gene in combination with ganciclovir (GCV) administration as therapy against murine mammary cancer. Approximately 80% of BJMC3879 metastatic mammary carcinoma cells, derived from MMTV-infected BALB/c mice, died as a result of HSVtk/GCV treatment 72 hours after the transfection; decreased DNA synthesis was also seen. Mammary tumors induced by inoculation of syngeneic mice with BJMC3879 cells were subsequently treated by direct injection of vector containing HSVtk (pHSVtk) alone, empty vector or saline alone twice a week. After each injection, the tumors were subjected to in vivo electroporation. Mice treated with pHSVtk or saline were intraperitoneally injected with GCV at 40 mg/kg five times a week. Significantly reduced tumor volumes were observed for the pHSVtk+GCV group in experimental week 2 and thereafter throughout the 2-month study. DNA synthesis was significantly decreased as well in the pHSVtk+GCV group compared with all other groups. Furthermore, metastasis to lymph nodes and lungs was significantly suppressed by HSVtk/GCV treatment. Expression of HSVtk in the tumors was confirmed by RT-PCR. Macrophage accumulations were frequently observed in the peripheries of necrotic regions in HSVtk/GCV-treated tumors, where levels of apoptosis were significantly higher than those observed in other groups. We therefore conclude that in vivo electroporation can result in efficient gene transfer and that the HSVtk/GCV prodrug system strongly suppresses tumor growth and metastases in this model.     

Long-term follow-up of patients with malignant pleural mesothelioma receiving high-dose adenovirus herpes simplex thymidine kinase/ganciclovir suicide gene therapy.

PURPOSE: Delineation of the long-term follow-up data on a series of patients with malignant mesothelioma, who received a single intrapleural dose of a nonreplicative adenoviral (Ad) vector encoding the herpes simplex virus thymidine kinase "suicide gene" (Ad.HSVtk) in combination with systemic ganciclovir. EXPERIMENTAL DESIGN: This report focuses on the 21 patients receiving "high-dose" therapy, defined by an intrapleural dose of vector (> or =1.6 x 10(13) viral particles), where transgene-encoded tk protein was reliably identified on immunohistochemical staining. In 13 patients, the vector was deleted in the E1 and E3 regions of the Ad; in the other eight patients, the vector had deletions in the Ad genes E1 and E4. Safety, immunologic responses, transgene expression, and clinical responses were evaluated. RESULTS: Both the E1/E3-deleted vector and the E1/E4-deleted vector were well tolerated and safe, although production of the E1/E4 vector was more difficult. Posttreatment antibody responses against the tumors were consistently seen. Interestingly, we observed a number of clinical responses in our patients, including two long-term (>6.5 year) survivors, both of whom were treated with the E1/E4-deleted vector. CONCLUSIONS: Intrapleural Ad.HSVtk/ganciclovir is safe and well tolerated in mesothelioma patients and resulted in long-term durable responses in two patients. Given the limited amount of gene transfer observed, we postulate that Ad.HSVtk may have been effective due to induction of antitumor immune responses. We hypothesize that approaches aiming to augment the immune effects of Ad gene transfer (i.e., with the use of cytokines) may lead to increased numbers of therapeutic responses in otherwise untreatable pleural malignancies.     

Antimetastatic gene expression profiles mediated by retinoic acid receptor beta 2 in MDA-MB-435 breast cancer cells

Background  

The retinoic acid receptor beta 2 (RARβ2) gene modulates proliferation and survival of cultured human breast cancer cells. Previously we showed that ectopic expression of RARβ2 in a mouse xenograft model prevented metastasis, even in the absence of the ligand, all- trans retinoic acid. We investigated both cultured cells and xenograft tumors in order to delineate the gene expression profiles responsible for an antimetastatic phenotype.     

A novel prostate cancer subtyping classifier based on luminal and basal phenotypes

Background

Prostate cancer (PCa) is a clinically heterogeneous disease. The creation of an expression-based subtyping model based on prostate-specific biological processes was sought.

Methods

Unsupervised machine learning of gene expression profiles from prospectively collected primary prostate tumors (training, n = 32,000; evaluation, n = 68,547) was used to create a prostate subtyping classifier (PSC) based on basal versus luminal cell expression patterns and other gene signatures relevant to PCa biology. Subtype molecular pathways and clinical characteristics were explored in five other clinical cohorts.

Results

Clustering derived four subtypes: luminal differentiated (LD), luminal proliferating (LP), basal immune (BI), and basal neuroendocrine (BN). LP and LD tumors both had higher androgen receptor activity. LP tumors also had a higher expression of cell proliferation genes, MYC activity, and characteristics of homologous recombination deficiency. BI tumors possessed significant interferon γactivity and immune infiltration on immunohistochemistry. BN tumors were characterized by lower androgen receptor activity expression, lower immune infiltration, and enrichment with neuroendocrine expression patterns. Patients with LD tumors had less aggressive tumor characteristics and the longest time to metastasis after surgery. Only patients with BI tumors derived benefit from radiotherapy after surgery in terms of time to metastasis (hazard ratio [HR], 0.09; 95% CI, 0.01–0.71; n = 855). In a phase 3 trial that randomized patients with metastatic PCa to androgen deprivation with or without docetaxel (n = 108), only patients with LP tumors derived survival benefit from docetaxel (HR, 0.21; 95% CI, 0.09–0.51).

Conclusions

With the use of expression profiles from over 100,000 tumors, a PSC was developed that identified four subtypes with distinct biological and clinical features.

Plain language summary

• Prostate cancer can behave in an indolent or aggressive manner and vary in how it responds to certain treatments.
• To differentiate prostate cancer on the basis of biological features, we developed a novel RNA signature by using data from over 100,000 prostate tumors—the largest data set of its kind.
• This signature can inform patients and physicians on tumor aggressiveness and susceptibilities to treatments to help personalize cancer management.

     

Expression of estrogen receptor beta in the breast carcinoma of BRCA1 mutation carriers

Background  

Breast cancers (BC) in women carrying mutations in BRCA1 gene are more frequently estrogen receptor negative than the nonhereditary BC. Nevertheless, tamoxifen has been found to have a protective effect in preventing contralateral tumors in BRCA1 mutation carriers. The identification of the second human estrogen receptor, ERβ, raised a question of its role in hereditary breast cancer. The aim of this study was to assess the frequency of ERα, ERβ, PgR (progesterone receptor) and HER-2 expression in breast cancer patients with mutated BRCA1 gene and in the control group.     

Use of immunohistochemical markers can refine prognosis in triple negative breast cancer

Background  

Basal-like breast cancer has been extensively characterized on the basis of gene expression profiles, but it is becoming increasingly common for these tumors to be defined on the basis of immunohistochemical (IHC) staining patterns, particularly in retrospective studies where material for expression profiling may not be available. The IHC pattern that best defines basal-like tumors is under investigation and various combinations of ER, PR, HER2-, CK5/6+ and EGFR+ have been tested.     

Breast tumors from <Emphasis Type="Italic">CHEK2 1100delC-</Emphasis> mutation carriers: genomic landscape and clinical implications

Introduction  

Checkpoint kinase 2 (CHEK2) is a moderate penetrance breast cancer risk gene, whose truncating mutation 1100delC increases the risk about twofold. We investigated gene copy-number aberrations and gene-expression profiles that are typical for breast tumors of CHEK2 1100delC-mutation carriers.     

Combined enzyme/prodrug treatment by genetically engineered AT-MSC exerts synergy and inhibits growth of MDA-MB-231 induced lung metastases

Background

Metastatic spread of tumor cells remains a serious problem in cancer treatment. Gene-directed enzyme/prodrug therapy mediated by tumor-homing genetically engineered mesenchymal stromal cells (MSC) represents a promising therapeutic modality for elimination of disseminated cells. Efficacy of gene-directed enzyme/prodrug therapy can be improved by combination of individual systems. We aimed to define the combination effect of two systems of gene therapy mediated by MSC, and evaluate the ability of systemically administered genetically engineered mesenchymal stromal cells to inhibit the growth of experimental metastases derived from human breast adenocarcinoma cells MDA-MB-231/EGFP.

Methods

Human adipose tissue-derived mesenchymal stromal cells (AT-MSC) were retrovirally transduced with fusion yeast cytosine deaminase::uracil phosphoribosyltransferase (CD::UPRT) or with Herpes simplex virus thymidine kinase (HSVtk). Engineered MSC were cocultured with tumor cells in the presence of prodrugs 5-fluorocytosin (5-FC) and ganciclovir (GCV). Combination effect of these enzyme/prodrug approaches was calculated. SCID/bg mice bearing experimental lung metastases were treated with CD::UPRT-MSC, HSVtk-MSC or both in combination in the presence of respective prodrug(s). Treatment efficiency was evaluated by EGFP-positive cell detection by flow cytometry combined with real-time PCR quantification of human cells in mouse organs. Results were confirmed by histological and immunohistochemical examination.

Results

We demonstrated various extent of synergy depending on tested cell line and experimental setup. The strongest synergism was observed on breast cancer-derived cell line MDA-MB-231/EGFP. Systemic administration of CD::UPRT-MSC and HSVtk-MSC in combination with 5-FC and GCV inhibited growth of MDA-MB-231 induced lung metastases.

Conclusions

Combined gene-directed enzyme/prodrug therapy mediated by MSC exerted synergic cytotoxic effect and resulted in high therapeutic efficacy in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0149-2) contains supplementary material, which is available to authorized users.