Ectopic expression of herpes simplex virus-thymidine kinase gene in human non-small cell lung cancer cells conferred caspase-activated apoptosis sensitized by ganciclovir

Oncolytic viruses in lung cancer treatment: a review article

Lung cancer has a high morbidity rate worldwide due to its resistance to therapy. So new treatment options are needed to improve the outcomes of lung cancer treatment. This study aimed to evaluate the effectiveness of oncolytic viruses (OVs) as a new type of cancer treatment. In this study, 158 articles from PubMed and Scopus from 1994 to 2022 were reviewed on the effectiveness of OVs in the treatment of lung cancer. The oncolytic properties of eight categories of OVs and their interactions with treatment options were investigated. OVs can be applied as a promising immunotherapy option, as they are reproduced selectively in different types of cancer cells, cause tumor cell lysis and trigger efficient immune responses.

Fluoxetine enhances the antitumor effect of olfactory ensheathing cell-thymidine kinase/ganciclovir gene therapy in human glioblastoma multiforme cells through upregulation of Connexin43 levels

Glioblastoma multiforme (GBM) is the most invasive form of primary brain astrocytoma, resulting in poor clinical outcomes. Herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) gene therapy is considered a promising strategy for GBM treatment. Since Connexin43 (Cx43) expression is reduced in GBM cells, increasing Cx43 levels could enhance the effectiveness of gene therapy. The present study aims to examine the impact of fluoxetine on HSV-TK/GCV gene therapy in human GBM cells using human olfactory ensheathing cells (OECs) as vectors. The effect of fluoxetine on Cx43 levels was assessed using the western blot technique. GBM-derived astrocytes and OECs-TK were Cocultured, and the effect of fluoxetine on the Antitumor effect of OEC-TK/GCV gene therapy was evaluated using MTT assay and flow cytometry. Our results showed that fluoxetine increased Cx43 levels in OECs and GBM cells and augmented the killing effect of OECs-TK on GBM cells. Western blot data revealed that fluoxetine enhanced the Bax/Bcl2 ratio and the levels of cleaved caspase-3 in the coculture of OECs-TK and GBM cells. Moreover, flow cytometry data indicated that fluoxetine increased the percentage of apoptotic cells in the coculture system. This study suggests that fluoxetine, by upregulating Cx43 levels, could strengthen the Antitumor effect of OEC-TK/GCV gene therapy on GBM cells.

β2-Adrenergic receptor agonist enhances the bystander effect of HSV-TK/GCV gene therapy in glioblastoma multiforme via upregulation of connexin 43 expression

Glioblastoma multiforme (GBM) is the most invasive form of primary brain astrocytoma. Gene therapy using the herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) is a new strategy for GBM treatment. As the connexin 43 (Cx43) levels are downregulated in GBM cells, it seems that the upregulation of Cx43 could improve the efficacy of the gene therapy. This study aims to evaluate the effect of clenbuterol hydrochloride (Cln) as a β2-adrenergic receptor agonist on HSV-TK/GCV gene therapy efficacy in human GBM cells using olfactory ensheathing cells (OECs) as vectors. The lentivirus containing the thymidine kinase gene was transduced to OECs and the effective dose of GCV on cells was measured by MTT assay. We found that Cln upregulated Cx43 expression in human GBM cells and OECs and promoted the cytotoxic effect of GCV on the co-culture cells. Western blot results showed that Cln increased the cleaved caspase-3 expression and the Bax/Bcl2 ratio in the co-culture of GBM cells and OEC-TK. Also, the flow cytometry results revealed that Cln increased apoptosis in the co-culture of GBM cells and OEC-TK cells. This study showed that Cln via upregulation of Cx43 expression could enhance the bystander effect of HSVTK-GCV gene therapy in human GBM cells.

Polymeric Nanovectors Incorporated with Ganciclovir and HSV-tk Encoding Plasmid for Gene-Directed Enzyme Prodrug Therapy

In the area of gene-directed enzyme prodrug therapy (GDEPT), using herpes simplex virus thymidine kinase (HSV-tk) paired with prodrug ganciclovir (GCV) for cancer treatment has been extensively studied. It is a process involved with two steps whereby the gene (HSV-tk) is first delivered to malignant cells. Afterward, non-toxic GCV is administered to that site and activated to cytotoxic ganciclovir triphosphate by HSV-tk enzyme expressed exogenously. In this study, we presented a one-step approach that both gene and prodrug were delivered at the same time by incorporating them with polymeric micellar nanovectors. GCV was employed as an initiator in the ring-opening polymerization of ε-caprolactone (ε-CL) to synthesize hydrophobic GCV-poly(caprolactone) (GCV-PCL), which was furthered grafted with hydrophilic chitosan to obtain amphiphilic polymer (GCV-PCL-chitosan) for the fabrication of self-assembled micellar nanoparticles. The synthesized amphiphilic polymer was characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Micellar prodrug nanoparticles were analyzed by dynamic light scattering, zeta potential, critical micelle concentration, and transmission electron microscopy. Polymeric prodrug micelles with optimal features incorporated with HSV-tk encoding plasmids were cultivated with HT29 colorectal cancer cells and anticancer effectiveness was determined. Our results showed that prodrug GCV and HSV-tk cDNA encoded plasmid incorporated in GCV-PCL-chitosan polymeric nanocarriers could be delivered in a one-step manner to HT-29 cells and triggered high cytotoxicity.

From basic researches to new achievements in therapeutic strategies of KRAS-driven cancers

Among the numerous oncogenes involved in human cancers, KRAS represents the most studied and best characterized cancer-related genes. Several therapeutic strategies targeting oncogenic KRAS (KRAS onc ) signaling pathways have been suggested, including the inhibition of synthetic lethal interactions, direct inhibition of KRAS onc itself, blockade of downstream KRAS onc effectors, prevention of post-translational KRAS onc modifications, inhibition of the induced stem cell-like program, targeting of metabolic peculiarities, stimulation of the immune system, inhibition of inflammation, blockade of upstream signaling pathways, targeted RNA replacement, and oncogene-induced senescence. Despite intensive and continuous efforts, KRAS onc remains an elusive target for cancer therapy. To highlight the progress to date, this review covers a collection of studies on therapeutic strategies for KRAS published from 1995 to date. An overview of the path of progress from earlier to more recent insights highlight novel opportunities for clinical development towards KRASonc-signaling targeted therapeutics.

Adenovirus-mediated herpes simplex virus thymidine kinase gene therapy combined with ganciclovir induces hepatoma cell apoptosis

The present study aimed to examine the apoptotic effects of adenovirus (ADV)-mediated herpes simplex virus thymidine kinase (ADV-TK) combined with ganciclovir (GCV) in tissues obtained from patients with hepatocellular carcinoma in order to provide a theoretical basis for the development of this gene therapy program. Apoptosis detection was conducted using the terminal deoxynucleotidyl-transferase-mediated dUTP nick end labelling assay and the apoptosis index was compared between the experimental; and control groups. Furthermore, the protein expression levels of caspase-3, B-cell lymphoma-2 (Bcl-2), Bcl-2-assoicated protein X (Bax) and nuclear factor (NF)-κB were examined in pathological specimens using immunohistochemical staining. The Bax/Bcl-2 ratio and the release of cytochrome c were examined using western blot analysis. Results indicated that combined ADV-TK and GCV treatment significantly increased the number of apoptotic cells compared with the control group (P<0.05). Immunohistological analysis revealed that ADV-TK and GCV treatment significantly increased the number of caspase-3-positive cells, reduced the Bax/Bcl-2 ratio and NF-κB expression levels and promoted the release of cytochrome c compared with the control group (P<0.01). In conclusion, the present results suggest that combined ADV-TK and GCV treatment exerts its effect through the apoptotic signaling pathway.

A novel sulfonyl chromen-4-ones (CHW09) preferentially kills oral cancer cells showing apoptosis, oxidative stress, and DNA damage

Several functionalized chromones, the key components of naturally occurring oxygenated heterocycles, have anticancer effects but their sulfone compounds are rarely investigated. In this study, we installed a sulfonyl substituent to chromen-4-one skeleton and synthesized CHW09 to evaluate its antioral cancer effect in terms of cell viability, cell cycle, apoptosis, oxidative stress, and DNA damage. In cell viability assay, CHW09 preferentially kills two oral cancer cells (Ca9-22 and CAL 27), less affecting normal oral cells (HGF-1). Although CHW09 does not change the cell cycle distribution significantly, CHW09 induces apoptosis validated by flow cytometry for annexin V and by western blotting for cleaved poly(ADP-ribose) polymerase (PARP), and caspases 3/8/9. These apoptosis signaling expressions are partly decreased by apoptosis inhibitor (Z-VAD-FMK) or free radical scavenger (N-acetylcysteine). Furthermore, CHW09 induces oxidative stress validated by flow cytometry for the generations of reactive oxygen species (ROS) and mitochondrial superoxide (MitoSOX), and the suppression of mitochondrial membrane potential (MMP). CHW09 also induces DNA damage validated by flow cytometry for the increases of DNA double strand break marker γH2AX and oxidative DNA damage marker 8-oxo-2'-deoxyguanosine (8-oxodG). Therefore, our newly synthesized CHW09 induces apoptosis, oxidative stress, and DNA damage, which may lead to preferential killing of oral cancer cells compared with normal oral cells.

Withaferin A Induces Oxidative Stress-Mediated Apoptosis and DNA Damage in Oral Cancer Cells

Withaferin A (WFA) is one of the most active steroidal lactones with reactive oxygen species (ROS) modulating effects against several types of cancer. ROS regulation involves selective killing. However, the anticancer and selective killing effects of WFA against oral cancer cells remain unclear. We evaluated whether the killing ability of WFA is selective, and we explored its mechanism against oral cancer cells. An MTS tetrazolium cell proliferation assay confirmed that WFA selectively killed two oral cancer cells (Ca9-22 and CAL 27) rather than normal oral cells (HGF-1). WFA also induced apoptosis of Ca9-22 cells, which was measured by flow cytometry for subG1 percentage, annexin V expression, and pan-caspase activity, as well as western blotting for caspases 1, 8, and 9 activations. Flow cytometry analysis shows that WFA-treated Ca9-22 oral cancer cells induced G2/M cell cycle arrest, ROS production, mitochondrial membrane depolarization, and phosphorylated histone H2A.X (γH2AX)-based DNA damage. Moreover, pretreating Ca9-22 cells with N-acetylcysteine (NAC) rescued WFA-induced selective killing, apoptosis, G2/M arrest, oxidative stress, and DNA damage. We conclude that WFA induced oxidative stress-mediated selective killing of oral cancer cells.

Age-related cataracts: Role of unfolded protein response, Ca2+ mobilization, epigenetic DNA modifications, and loss of Nrf2/Keap1 dependent cytoprotection

Age-related cataracts are closely associated with lens chronological aging, oxidation, calcium imbalance, hydration and crystallin modifications. Accumulating evidence indicates that misfolded proteins are generated in the endoplasmic reticulum (ER) by most cataractogenic stresses. To eliminate misfolded proteins from cells before they can induce senescence, the cells activate a clean-up machinery called the ER stress/unfolded protein response (UPR). The UPR also activates the nuclear factor-erythroid-2-related factor 2 (Nrf2), a central transcriptional factor for cytoprotection against stress. Nrf2 activates nearly 600 cytoprotective target genes. However, if ER stress reaches critically high levels, the UPR activates destructive outputs to trigger programmed cell death. The UPR activates mobilization of ER-Ca2+ to the cytoplasm and results in activation of Ca2+-dependent proteases to cleave various enzymes and proteins which cause the loss of normal lens function. The UPR also enhances the overproduction of reactive oxygen species (ROS), which damage lens constituents and induce failure of the Nrf2 dependent cytoprotection. Kelch-like ECH-associated protein 1 (Keap1) is an oxygen sensor protein and regulates the levels of Nrf2 by the proteasomal degradation. A significant loss of DNA methylation in diabetic cataracts was found in the Keap1 promoter, which overexpresses the Keap1 protein. Overexpressed Keap1 significantly decreases the levels of Nrf2. Lower levels of Nrf2 induces loss of the redox balance toward to oxidative stress thereby leading to failure of lens cytoprotection. Here, this review summarizes the overall view of ER stress, increases in Ca2+ levels, protein cleavage, and loss of the well-established stress protection in somatic lens cells.

Specific and Efficient Regression of Cancers Harboring KRAS Mutation by Targeted RNA Replacement

Mutations in the KRAS gene, which persistently activate RAS function, are most frequently found in many types of human cancers. Here, we proposed and verified a new approach against cancers harboring the KRAS mutation with high cancer selectivity and efficient anti-cancer effects based on targeted RNA replacement. To this end, trans-splicing ribozymes from Tetrahymena group I intron were developed, which can specifically target and reprogram the mutant KRAS G12V transcript to induce therapeutic gene activity in cells. Adenoviral vectors containing the specific ribozymes with downstream suicide gene were constructed and then infection with the adenoviruses specifically downregulated KRAS G12V expression and killed KRAS G12V-harboring cancer cells additively upon pro-drug treatment, but it did not affect the growth of wild-type KRAS-expressing cells. Minimal liver toxicity was noted when the adenoviruses were administered systemically in vivo. Importantly, intratumoral injection of the adenoviruses with pro-drug treatment specifically and significantly impeded the growth of xenografted tumors harboring KRAS G12V through a trans-splicing reaction with the target RNA. In contrast, xenografted tumors harboring wild-type KRAS were not affected by the adenoviruses. Therefore, RNA replacement with a mutant KRAS-targeting trans-splicing ribozyme is a potentially useful therapeutic strategy to combat tumors harboring KRAS mutation.

Effects of HSV-TK+GFP/GCV suicide gene therapy system on mouse pancreatic cancer cells

AIM: To study in vitro therapeutic effect on mouse pancreatic cancer, as well as the bystander effect with HSV-TK suicide gene in combination with prodrug GCV.

METHODS: HSV-TK and GFP were inserted into pcDNA3.1 (+) to construct pcDNA3.1+/HSV-TK+GFP, and pcDNA3.1+/HSV-TK+GFP was transferred into mouse pancreatic cancer cell MPC by Lipofectin. We then added GCV to these gene-modified cells and studied the sensitivity of the cells to GCV as well as the bystander effect.

RESULTS: The gene modified pancreatic cancer cells MPC/HSV-TK+GFP were successfully developed. In vitro experiments showed that when the MPC/HSV-TK+GFP cells accounted for 10% of hybrid cells, the low concentration (20 mg/L) of GCV was about 50% of tumor cell killing. In vivo results showed that the low concentration of GCV killed the cells. And tumor growth of the mouse model was inhibited.

CONCLUSION: Our data demonstrate MPC/HSV-TK+GFP cells are sensitive to the treatment of GCV compared with unmodified tumor cells, and remarkable bystander effect is seen.

NT-polyplex: a new tool for therapeutic gene delivery to neuroblastoma tumors

Neurotensin (NT)-polyplex is a nonviral system for the targeted gene delivery to cells that express and internalize the high-affinity NT receptor (NTSR1). In hemiparkinsonian rats, we previously demonstrated the morphological and functional recovery from dopaminergic neurodegeneration using the NT-polyplex as a vehicle to transfect a neurotrophic gene. The main objective of this work was to demonstrate the feasibility of NT-polyplex to transfect reporter or therapeutic genes into neuroblastoma tumors through the blood stream or by intratumoral injection. N1E-115 cells known to express NTSR1 were allografted into athymic mice to generate the neuroblastoma tumor model. Both routes of administration allowed the NT-polyplex to reach and transfect tumoral cells. A low transgene expression was also detected in intestinal tract cells only after the injection into the blood stream. The transfection of the thymidine kinase (HSVTK) suicide gene followed by ganciclovir (GCV) treatment decreased the size and weight of neuroblastoma tumors by 30-50% and increased apoptosis compared to controls. This study shows the potential of the NT-polyplex as specific gene-transfer system for NTSR1 cancer cells.

Activation of caspase-3 noninvolved in the bystander effect of the herpes simplex virus thymidine kinase gene/ganciclovir (HSV-tk/GCV) system

Use of the herpes simplex virus thymidine kinase gene/ganciclovir (HSV-tk/GCV) system is one of the promising approaches in the rapidly growing area of gene therapy. The "bystander effect," a phenomenon in which HSV-tk+ cells exposed to GCV are toxic to adjacent HSV-tk- cells, was reported to play an important role in suicide gene therapy. However, the mechanism by which HSV-tk/GCV induces the bystander effect is poorly understood. We monitored the activation of caspase-3 in living cells induced by the HSV-tk/GCV system using a genetically encoded fluorescence resonance energy transfer (FRET) probe CD3, , a caspase-3 recognition site fused with a cyan fluorescent protien (CFP) and a red fluorescent protein (DsRed) which we reported and named in a previous paper. Fluorescence protein (FP)-based multicolor cellular labeling, combined with the multichannel fluorescence imaging and FRET imaging techniques, provides a novel and improved approach to directly determine whether the activation of caspase-3 involved in the HSV-tk/GCV system induces cell apoptosis in tk gene-expressing cells and their neighboring cells. FRET ratio images of CD3, and fluorescence images of the fusion protein of thymidine kinase linked with green fluorescent protein (TK-GFP), indicated that HSV-tk/GCV system-induced apoptosis in human adenoid cystic carcinoma (ACC-M) cells was via a caspase-3 pathway, and the activation of caspase-3 was not involved in the bystander effect of HSV-tk/GCV system.

Specific Regression of Human Cancer Cells by Ribozyme-Mediated Targeted Replacement of Tumor-Specific Transcript

In this study, we describe a novel approach to human cancer therapy that is based upon trans-splicing ribozyme-mediated replacement of cancer-specific RNAs with new transcripts that exert therapeutic activities. We have developed a specific ribozyme that can reprogram human telomerase reverse transcriptase (hTERT) RNA to induce transgene activity selectively in cancer cells that express the RNA. The ribozyme-mediated triggering of the transgene expression was accomplished via a high-fidelity trans-splicing reaction with the targeted residue in the hTERT-expressing cells. The ribozyme also induced cytotoxic activity in various hTERT-expressing cancer cells, hence selectively retarding the growth of those cells. Efficient and specific cell regression was also detected with ganciclovir (GCV) treatment only in hTERT-positive cancer cells, which were established to express stably the specific ribozyme that contains the herpes simplex virus thymidine kinase (HSV-tk) gene. Tissue-specific expression of the ribozyme could further augment the target specificity of the ribozyme. Importantly, we observed efficient regression of tumors with GCV treatment in mice that had been inoculated subcutaneously with hTERT-positive cancer cells that stably expressed the specific ribozyme that contains HSV-tk. These results suggest that the hTERT RNA-targeting trans-splicing ribozyme could be a powerful agent for tumor-targeted specific gene therapy.

The suppressed proliferation and premature senescence by ganciclovir in p53-mutated human non-small-lung cancer cells acquiring herpes simplex virus-thymidine kinase cDNA

The concerted actions of molecular networks determine how cells undergo proliferation, death or aging. Here we show that the highly invasive, tumorigenic human non-small-cell-lung cancer (NSCLC) cells carrying mutated p53 alleles were transfected with herpes simplex virus-thymidine kinase (HSV-tk) cDNA and the selected clone was susceptible to exogenous ganciclovir (GCV). The work further indicated that, in the stable HSV-tk transfectants, GCV suppressed cell proliferation by inducing G(2)/M cell cycle arrest and premature senescence and the potency can be amplified through bystander effect. The growth suppression of the established tumor xenografts in nude mice can be successfully targeted by GCV. These data showed that the GCV-suppressed tumor cell proliferation can be coordinated by cell cycle arrest and cellular senescence in HSV-tk transfectant lacking wild-type p53.

Replacement and Suicide Gene Therapy for Targeted Treatment of Lung Cancer

Lung cancer is the leading cause of cancer-related death in the developed world; consequently, novel therapeutic strategies are in high demand. A major problem with the present treatment modalities is the lack of tumor specificity giving rise to dose-limiting toxicity and side effects. Gene therapy constitutes an experimental approach gaining increased attention as a putative future cancer therapeutic strategy. Using this strategy, cancer cytotoxicity can be obtained by replacing mutated genes with functional analogues or introducing a suicide gene into the malignant cells. Insight into the molecular biology of cancer cells has identified a number of regulatory gene sequences, which can be used to selectively activate the therapeutic gene specifically in cancer cells, thereby reducing nonspecific toxicity. Although further improvements are necessary, recent encouraging results have shown promise for future clinical application of gene therapy. This article presents an update on the experimental and clinical results obtained within the field of lung cancer gene therapy, concentrating on strategies to specifically activate expression of the therapeutic gene in cancer cells. Furthermore, status of the development of delivery vector constructs for lung cancer gene therapy will be presented.