The involvement of mitochondria and the caspase-9 activation pathway in rituximab-induced apoptosis in FL cells.

Despite the wide use of anti-CD20 antibody rituximab in the cancer treatment of B cell malignancies, the signalling pathways of CD20-induced apoptosis are still not understood. By using dominant negative (DN)-caspase-9 overexpressing follicular lymphoma cells we demonstrated that the activation of caspase-9 was essential for rituximab-mediated apoptosis. The death receptor pathway mediated by caspase-8 activation was not involved in rituximab-mediated apoptosis since overexpression of FLIP(short) or FLIP(long) proteins, inhibitors of caspase-8 activation, could not inhibit rituximab-induced apoptosis. However, the death receptor pathway activation by anti-Fas antibodies showed an additive effect on rituximab-induced apoptosis. The stabilisation of the mitochondrial outer membrane by Bcl-x(L) overexpression inhibited cell death, showing the important role of mitochondria in rituximab-induced apoptosis. Interestingly, the rituximab-induced release of cytochrome c and collapse of mitochondrial membrane potential were regulated by caspase-9. We suggest that caspase-9 and downstream caspases may feed back to mitochondria to amplify mitochondrial disruption during intrinsic apoptosis.

Replication competent Semliki Forest virus prolongs survival in experimental lung cancer.

We evaluated the therapeutic potential of the replication competent vector VA7-EGFP, which is based on the avirulent Semliki Forest virus (SFV) strain A7 (74) carrying the EGFP marker gene in an orthotopic lung cancer tumor model in nude mice. We have previously shown that this oncolytic vector destroys tumor cells efficiently in vitro and in vivo (in subcutaneous tumor model). Tumor growth in animals with orthotopically implanted adenocarcinoma cells (A549) were monitored during the study with small animal CT. We show that locally administered virotherapy with VA7-EGFP increased survival rate in experimental lung cancer significantly (p < 0.001) comparable to results obtained with the second generation conditionally replicating adenoviral vector Ad5-Delta24TK-GFP, used for comparison. The limited efficacy in systemically administered oncolytic viruses is the essential problem in oncolytic virotherapy and also in this study we were not able to elicit significant response with systemic administration route. Despite the fact that tumor microenvironment in orthotopic lung cancer is more optimal, viruses failed to home to the tumors and were unable to initiate efficient intratumoral replication. Clearly, the efficacy of virotherapy is influenced by many factors such as the route of virus administration, immunological and physiological barriers and cancer cell-specific features (IFN-responsiveness).

HOX-GFP and WOX-GFP lentivirus vectors for inner ear gene transfer.

CONCLUSION: GFP transgene was expressed in the lining cells of the perilymphatic space. Lentivirus vectors are safe and cause only minimal inflammatory reaction. Transgene products can be delivered into the perilymph by utilizing lentivirus vectors. OBJECTIVES: To analyze the efficiency and safety of lentiviral vectors HOX-GFP and WOX-GFP in intracochlear gene transfer. MATERIALS AND METHODS: Lentivirus vectors were tested for their transduction efficiency in vivo in CD-1 mice. Half of the animals were pretreated with kanamycin. Lentivirus vector or saline (1 microl) was injected into the inner ear. All the animals were sacrificed 14 days after the surgery and the cochleae and selected organs were analyzed immunohistochemically. RESULTS: HOX-GFP and WOX-GFP expression was restricted to the lining cells of the scala tympani and scala vestibuli. No GFP expression was seen in the organ of Corti or the spiral ganglion. Aminoglycoside treatment had no effect on the expression of these vectors. The distant spread of lentivirus vectors was minimal; only the liver of one animal showed some GFP expression. Inflammatory reaction caused by these vectors was mild. Few inflammatory cells were found in the perilymphatic space of the cochlea and in the vestibular organ.

Polyamine depletion and cell cycle manipulation in combination with HSV thymidine kinase/ganciclovir cancer gene therapy.

We have shown earlier that polyamine biosynthesis inhibition is accompanied by cell cycle alterations that can be utilized to enhance the efficacy of herpes simplex virus thymidine kinase - ganciclovir (HSV-TK/GCV) cancer gene therapy. In the present study, we asked 1) can the activated polyamine catabolism instead of biosynthesis inhibition be utilized to enhance the efficacy of HSV-TK/GCV gene therapy, and 2) can other known cell cycle inhibitors be used to make tumor cells more sensitive to this form of gene therapy? We show, using rat (9L) and human (U251-MG) glioma cell populations with 15% of HSV-TK-positive cells that DENSPM-induced activation of polyamine catabolism caused a profound polyamine deprivation in U251-MG cells, but there were no associated cell cycle effects in these cells. Consequently, we did not see any enhancement of the HSV-TK/GCV system. Aphidicolin, hydroxyurea, mimosine and resveratrol, but not lovastatin induced an apparent cell cycle arrest, followed by an intense but transient increase of the S phase cells after removal of the drug. This effect was shown to potentiate the HSV-TK/GCV cytotoxicity to some extent, especially in 9L cells and when the GCV treatment was started 0-24 h before the drug treatment. However, the enhancement was weaker than observed earlier with DFMO-induced cell cycle arrest and a considerable degree of the effect appeared to result from the growth-inhibitory actions of the drugs. In summary, we demonstrate that polyamine deprivation via DENSPM action is not associated with cell cycle effects and is not sufficient to cause enhancement of the HSV-TK/GCV system. Also, drugs with a rapid effect to the cell cycle are weak boosters of the HSVTK/GCV gene therapy, thus being less useful than DFMO for enhancement of this gene therapy form in animal studies and clinical trials.

A conditionally replicative adenovirus that codes for a TK-GFP fusion protein (Ad5Delta24TK-GFP) for evaluation of the potency of oncolytic virotherapy combined with molecular chemotherapy.

The utility of conditionally replicative adenoviruses (CRAds) in cancer gene therapy is based on their ability to destroy tumor cells by oncolysis. However, in order to achieve adequate therapeutic response, CRAds have to spread through the tumor tissue by replication. Thus, to study the potency of these viruses to replicate and penetrate in tumors, we created a herpes simplex virus type 1 thymidine kinase-green fluorescent protein fusion gene (TK-GFP) encompassing CRAd (Ad5Delta24TK-GFP), whose tumor selectivity is mediated by a retinoblastoma (Rb)-binding site mutation. In addition, we evaluated the oncolytic efficacy of Ad5Delta24TK-GFP in combination with the TK/ganciclovir (GCV) system. Based on our results, Ad5Delta24TK-GFP replicates in cancer cells resulting in oncolysis and can efficiently penetrate into tumors. Additionally, the combination of GCV with Ad5Delta24TK-GFP augmented cell death in vitro but this was not observed in vivo: tumor growth was significantly reduced by oncolysis when compared to non-replicative virus (p<0.001), but administration of GCV did not significantly enhance oncolysis. This suggests that in certain conditions, TK/GCV-mediated cell killing may be counterproductive to replication and oncolysis, which on the other hand might be useful feature for clinical trials in case of replication-associated toxicity.

hCAR-EGFP fusion receptor in human follicular lymphoma B cells - a model for adenoviral gene therapy for B cell malignancies.

Adenovirus-mediated gene therapy for hematopoietic malignancies, especially those derived from B cells, is difficult due to systemic nature of these diseases. More importantly, most tumor cells derived from B cell lineage express a very low level of the adenovirus receptor hCAR; thus, warranting the design of adenoviral vectors with high affinity to abundant B cell surface molecules. To mimic this approach and to test the validity of adenoviral vectors in gene therapy of disseminated malignancies, we created an hCAR-expressing follicular lymphoma B cell line. The cell line was generated with the aid of a lentivirus vector carrying a novel fusion gene with EGFP replacing the cytoplasmic domain of hCAR. After verifying that this cell line was expressing the hybrid receptor in a correct manner and enrichment of the bright EGFP positive population, the cells were transduced with adenoviruses expressing the red fluorescent protein DsRed2. It was shown that regular transduction with a low viral dose (1 pfu/cell) increased the gene transfer rate by a factor of 5. Furthermore, experiments with adenovirus vector carrying the HSV-TK-GFP transgene demonstrated that the modified follicular lymphoma B cells became sensitive to ganciclovir while the parental cells remained virtually resistant to this form of gene therapy. In summary, we show here with this simple model system that adenoviral gene therapy of B cell malignancies is possible provided that correct receptors for adenovirus attachment are present on the surface of the target cells. Thus, our results warrant further modifications of adenovirus capsid to obtain vectors with specific affinity to B cell epitopes.

Transcriptional targeting of virus-mediated gene transfer by the human hexokinase II promoter.

The efficacy of the most commonly used form of suicide gene therapy, the HSV-TK/GCV method, utilizing herpes simplex virus thymidine kinase (HSV-TK) and antiviral drug ganciclovir (GCV) has been demonstrated in clinical trials. However, safer delivery of the therapeutic gene and more controlled regulation of the transgene expression, the essential prerequisites for successful therapeutic use, are still needed. We describe improved suicide gene therapy against cancer through transcripitional targeting by a strong and selective tumor-specific human hexokinase II promoter (hHKII). We examined the targeting properties of the human hHKII promoter in different human non-small cell lung cancer (NSCLC) and other human cancer cell lines using self-inactivating, VSV-G pseudotyped lentiviral vector. To confirm accurate transcriptional targeting of the hHKII promoter, the lack of transgene expression was verified in human primary bronchial epithelial and bronchial fibroblast cells. Furthermore, tissue-specific expression of the promoter was confirmed using transgenic mouse lines carrying the hHKII promoter driven luciferase reporter gene. We also tested the efficacy of the HSV-TK/GCV suicide gene therapy with the hHKII targeted lentiviral vector to NSCLC cells. Our results show that the hHKII promoter is strongly expressed in cancer cells. The targeted vector with the shortest hHKII promoter fragment (352 bp) appeared to have the best targeting properties because it efficiently governed the expression of the therapeutic gene in cancer cell lines, especially in certain non-small cell lung cancer cell lines, the transgene expression in human primary cells was virtually undetectable, and expression of the proximal hHKII promoter in transgenic mice was very low in most tissues. Also, the anti-cancer efficacy of HSV-TK/GCV therapy with the hHKII-targeted vector was comparable to that obtained with the control vector that utilized a commonly used constitutive promoter from the human elongation factor 1 alpha (hEF1alpha) gene. In conclusion, the transcriptionally targeted lentivirus vector with hHKII promoter can successfully direct HSV-TK/GCV suicide gene therapy to non-small cell lung cancer and other tumor cell types. These results warrant further studies with orthotopic animal tumor models and primary human cancer material.

HIV-1 TAT protein transduction domain mediates enhancement of enzyme prodrug cancer gene therapy in vitro: a study with TAT-TK-GFP triple fusion construct.

Protein transduction domain (PTD) from HIV-1 TAT protein has been reported to translocate across the mammalian cell membrane, also as a part of fusion proteins. However, the true nature of TAT-mediated intercellular spreading is still under debate because it has been claimed to be a fixation artifact. To study the spreading of TAT fusion proteins and their potency to enhance thymidine kinase/ ganciclovir (HSV-TK/GCV) cancer gene therapy, we constructed a novel triple fusion protein containing TAT PTD, HSV-TK and green fluorescent protein (TAT-TK-GFP). This fusion protein has three functional domains in the same polypeptide, allowing reliable determination of the relationship between transduction rate and cell killing efficiency. TAT-TK-GFP was cloned into a lentivirus vector and used for analyses of TAT-mediated protein translocation and enhancement of HSV-TK/GCV cytotoxicity. The triple fusion protein was expressed correctly in vitro, but cell-to-cell translocation was not observed in rat glioma cells (BT4C). However, TAT-TK-GFP made BT4C and SKOV3.ip1 (human ovarian carcinoma) cells significantly more sensitive to ganciclovir than TK-GFP, whereas the effect in PC-3 human prostate carcinoma cells was more subtle. It was also observed that growth in lower serum concentration (2.5-5%) abolished the enhancement in BT4C cells, suggesting that high proliferation rate is one of the factors that contribute to TAT PTD-mediated enhancement of cytotoxicity. In summary, our results indicate that TAT PTD fusion proteins do not translocate intercellularly at detectable levels, but enhancement of the HSV-TK/GCV cytotoxicity can be detected in rat and human tumor cell lines in vitro.

Properties of Sindbis virus vectors produced with a chimeric split helper system.

We have evaluated a chimeric, two-component Sindbis virus packaging system. As expected, use of this combination of two modified helper RNA species prevented formation of infection competent Sindbis viruses as analyzed by serial passaging. We observed, however, that vectors produced using this method were able to spread in BHK cell cultures and formed clusters of transgene positive cells that did not display cytopathic effects for up to 3 days post-transduction. Formation of spreading Sindbis virus vectors required only one of the helper components--the chimera with a deleted Ross River virus capsid and the Sindbis virus envelope glycoproteins. Spreading was also demonstrated in two rat glioma cell lines, 9L and BT4C, showing that this phenomenon was not limited to BHK cells. Our results warrant further characterization of split helper Sindbis virus vectors and imply their utility in gene therapy approaches where spreading of transgene expression and consequently high gene transfer rate could be beneficial.

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.

Production of an EGFR targeting molecule from a conditionally replicating adenovirus impairs its oncolytic potential.

Oncolytic virotherapy with conditionally replicating viruses is a promising approach for treating advanced cancers. Promiscuous tropism and low tumor transduction have represented limiting issues, which targeting approaches seek to overcome. An approach utilizing a secretory targeting molecule for the epidermal growth factor pathway (sCAR-EGF) has previously been shown to be compatible with replicating adenoviruses, when an E1-deleted vector was used in a dual-virus system in conjunction with a replication-competent agent. Here, we constructed a virus that replicates in cancer cells and codes for sCAR-EGF. Interestingly, the oncolytic potency of the novel agent was not improved over nontargeted controls in vitro or in vivo. These results suggest that the expression of biologically active proteins can be counterproductive to virus replication.

Cancer cells as targets for lentivirus-mediated gene transfer and gene therapy.

Lentiviruses have been used as gene transfer vectors for almost 10 years and their utility has been demonstrated in a variety of different applications. However, their value in cancer gene therapy has not been studied thoroughly. Here we show that VSV-G pseudotyped HIV-1-based lentiviruses are efficient vectors for human tumor cells in vitro and in vivo. Lentiviral gene transfer efficiency was demonstrated by transducing 42 different cell lines, representing 10 different human tumor types. It was shown that most of the cell lines were good or excellent targets for lentiviral transduction, allowing 50-95% gene transfer efficiency. These results were comparable to those obtained with an E1/E3 deleted, serotype 5 adenovirus vector. Analysis of lentivirus vector structure revealed that virus particles devoid of HIV-1 accessory proteins appeared to be more efficient, but the presence of enhancing elements cPPT and WPRE did not play a major role in transduction efficiency to four different human tumor cell lines. However, their effect on the gene expression level in these cells was apparent. To examine the impact of lentiviral gene expression level on suicide gene therapy approach, human osteosarcoma cells were transduced with lentivirus- or adenovirus vectors carrying the fusion gene HSV-TK-GFP and exposed to ganciclovir. Cell viability analysis after the treatment revealed that both vector types induced similar level of cytotoxicity, suggesting that lentiviral expression of a suicide gene is adequate for tumor cell destruction. Finally, in vivo transduction studies with subcutaneous tumors showed that lentivirus vectors can yield similar gene transfer efficiency than adenovirus vector, despite three orders of magnitude lower titer of the lentiviral preparation. In conclusion, these data show that lentiviruses are efficient gene transfer vehicles for human tumor cells and justify their use in further preclinical cancer gene therapy studies.

Non-small cell lung cancer as a target disease for herpes simplex type 1 thymidine kinase-ganciclovir gene therapy.

Lung cancer is a group of diseases that are difficult to cure and new treatment modalities, like gene therapy are actively tested to find alternatives for currently used strategies. Herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) method is one of the most frequently utilized forms of gene therapy and it has been tested on lung cancer, but no systematic study with comparison of different lung cancer types has been published. In this study, we examined in vitro and in vivo how good targets non-small cell lung cancer (NSCLC) cell lines representing adenocarcinoma, squamous cell lung cancer and large cell lung cancer are for adenovirus-mediated HSV-TK/GCV gene therapy. By using an adenovirus vector carrying a fusion gene of HSV-TK and green fluorescent protein (GFP), we found that: a) adenoviruses were efficient gene transfer vehicles for all types of NSCLCs; b) all adenocarcinoma and large cell lung cancer cells were good targets for HSV-TK/GCV therapy, whereas one of the squamous cell carcinoma cell lines was not responsive to the treatment; c) bystander effect played a major role in the success of this gene therapy form; d) subcutaneous tumors representing all three NSCLC types were efficiently treated with adenovirus-mediated HSV-TK/GCV gene therapy. In summary, this form of gene therapy appeared to be efficient treatment for human NSCLC and these results warrant further studies with primary lung cancer cells and orthotopic lung tumor models.

Osteosarcoma and chondrosarcoma as targets for virus vectors and herpes simplex virus thymidine kinase/ganciclovir gene therapy.

Osteosarcoma and chondrosarcoma, the most prevalent primary malignant tumors of the bone, have been demonstrated to be potential target diseases for herpes simplex virus type 1 thymidine kinase (HSV-TK)/ganciclovir (GCV) suicide gene therapy. However, the utility of this gene therapy form for bone tumor cells has not been studied systematically. In this report we show, with the aid of three osteosarcoma cell lines (Saos-2, U-2-OS and MG-63) and one chondrosarcoma cell line (SW1353) that: i) these tumor cells were permissive for adenovirus- or lentivirus-mediated gene delivery; ii) the cell lines appeared to be good or excellent targets for HSV-TK/GCV gene therapy; and iii) the extent of HSV-TK/GCV cytotoxic effect correlated with the presence of the 'bystander effect' in these cells. Our results also suggest that lentiviruses are potential vectors for bone cancer gene therapy. They transduced all four cell lines with high efficiency and provided HSV-TK expression level that was sufficient for cytotoxicity and bystander effect comparable to that obtained with adenovirus vectors.

TK-GFP fusion gene virus vectors as tools for studying the features of HSV-TK/ganciclovir cancer gene therapy in vivo.

The fusion gene of herpes simplex virus thymidine kinase and green fluorescent protein (TK-GFP) was shown to be a versatile tool for examining the features of thymidine kinase/ganciclovir gene therapy in vitro. In this study, we used viral vectors carrying the fusion gene to characterize the aspects of this gene therapy form in rodent tumor models. Growth of subcutaneous 9L rat tumors transduced ex vivo with TK-GFP gene was prevented when ganciclovir (GCV) treatment was initiated immediately after tumor inoculation. Established tumors (>100 mm(3)), however, were untreatable despite the initial 55% proportion of TK-GFP positive cells. This was due to a rapid clearance of TK-GFP positive cells, but not GFP positive cells. Propidium iodide staining revealed that TK-GFP lentivirus vector was able to induce apoptosis/necrosis in 9L cells, as opposed to the respective GFP vector. Furthermore, when a subcutaneous nude mouse tumor model was used, the percentage of TK-GFP positive cells in vivo was maintained similarly as in cultured cells, suggesting contribution of a fully functional immune response to the disappearance of fusion gene positive cells. In vivo gene transfer studies: adenovirus TK-GFP vector injections resulted in about 25% gene transfer efficiency to 9L tumors and showed that their growth could be significantly reduced even when the tumor volumes were already >120 mm(3). Part of the effect was shown to be due to cytotoxicity of the vector. In summary, our results demonstrate the utility of TK-GFP fusion gene-carrying viral vectors in animal studies and show that readily detectable therapeutic genes can help us to understand the complicated nature of in vivo cancer gene therapy experiments.

Recombination of replicon and helper RNAs and the emergence of propagation-competent vectors upon Sindbis virus vector production.

Sindbis vectors have shown remarkable antitumor efficacy and tumor-targeting capacity in animal models and hold promise for cancer therapy. Different packaging systems are used to produce propagation-incompetent Sindbis vectors. However, the vectors produced using either DH-BB single helper RNA or split helper RNA can spread in permissive cell cultures. We investigated the mechanisms of vector spreading and show, here, that recombination occurs between the replicon and DH-BB helper RNA, leading to formation of the full-length virus genome. Split helper RNA may not completely prevent wild-type reversion, although the frequency is greatly reduced. Contrary to propagation of Sindbis DH-BB vectors, Sindbis split helper vectors were frequently able to spread without cytopathic effect (CPE), a feature that was linked to wild-type reversion. Our results support the hypothesis that the non-cytopathic local spreading constantly observed with Sindbis split helper vector results from unspecific packaging of helper RNAs into vector particles and co-infection with particles containing replicon and helper RNAs. Several malignant cell lines with defective interferon responses were found to be permissive for non-cytopathic spreading of the Sindbis split helper vector. Interferon-α suppressed the spreading providing a possible option to control the vector.

PDTC enables type I TRAIL signaling in type II follicular lymphoma cells.

Based on Bcl-X(L) overexpression studies we identified type I and type II follicular lymphoma cell lines in response to TRAIL. We demonstrate here that either amount of caspase-8 activation or Bid cleavage could not define the dependence on mitochondria. Furthermore, an inhibitor of NF-kappaB, PDTC, enabled TRAIL to activate type I apoptotic pathway in type II cells. However, an inhibitor of IKK did not switch apoptosis to type I pathway in type II cells, indicating that NF-kappaB might not be responsible for the switch.

Dexamethasone-induced apoptosis and up-regulation of Bim is dependent on glycogen synthase kinase-3.

Glucocorticoids are commonly used in the treatment of lymphoid malignancies. In this study, we show that apoptosis induced by dexamethasone (Dex), a synthetic glucocorticoid, was dependent on mitochondria, since overexpression of Bcl-X(L) prevented Dex-induced apoptotic changes. Dominant negative (DN) caspase-9 also prevented Dex-induced apoptotic changes including the loss of mitochondrial membrane potential indicating that caspase-9 controls mitochondrial changes. In addition, we evaluated the role of glycogen synthase kinase (GSK3) in Dex-induced apoptosis. Inhibition of GSK3 attenuated Dex-induced up-regulation of Bim, loss of mitochondrial membrane potential, release of cyt c and DNA fragmentation. These results indicate that GSK3 contributes to Dex-induced apoptosis by controlling up-regulation of Bim.