Comparison of prostate-specific promoters and the use of PSP-driven virotherapy for prostate cancer

MRI detection of the malignant transformation of stem cells through reporter gene expression driven by a tumor-specific promoter

Background

Existing evidence has shown that mesenchymal stem cells (MSCs) can undergo malignant transformation, which is a serious limitation of MSC-based therapies. Therefore, it is necessary to monitor malignant transformation of MSCs via a noninvasive imaging method. Although reporter gene-based magnetic resonance imaging (MRI) has been successfully applied to longitudinally monitor MSCs, this technique cannot distinguish the cells before and after malignant transformation. Herein, we investigated the feasibility of using a tumor-specific promoter to drive reporter gene expression for MRI detection of the malignant transformation of MSCs.

Methods

The reporter gene ferritin heavy chain (FTH1) was modified by adding a promoter from the tumor-specific gene progression elevated gene-3 (PEG3) and transduced into MSCs to obtain MSCs-PEG3-FTH1. Cells were induced to undergo malignant transformation via indirect coculture with C6 glioma cells, and these transformed cells were named MTMSCs-PEG3-FTH1. Western blot analysis of FTH1 expression, Prussian blue staining and transmission electron microscopy (TEM) to detect intracellular iron, and MRI to detect signal changes were performed before and after malignant transformation. Then, the cells before and after malignant transformation were inoculated subcutaneously into nude mice, and MRI was performed to observe the signal changes in the xenografts.

Results

After induction of malignant transformation, MTMSCs demonstrated tumor-like features in morphology, proliferation, migration, and invasion. FTH1 expression was significantly increased in MTMSCs-PEG3-FTH1 compared with MSCs-PEG3-FTH1. Prussian blue staining and TEM showed a large amount of iron particles in MTMSCs-PEG3-FTH1 but a minimal amount in MSCs-PEG3-FTH1. MRI demonstrated that the T2 value was significantly decreased in MTMSCs-PEG3-FTH1 compared with MSCs-PEG3-FTH1. In vivo, mass formation was observed in the MTMSCs-PEG3-FTH1 group but not the MSCs-PEG3-FTH1 group. T2-weighted MRI showed a significant signal decrease, which was correlated with iron accumulation in the tissue mass.

Conclusions

We developed a novel MRI model based on FTH1 reporter gene expression driven by the tumor-specific PEG3 promoter. This approach could be applied to sensitively detect the occurrence of MSC malignant transformation.

Oncolytic Virotherapy in Solid Tumors: The Challenges and Achievements

Oncolytic virotherapy (OVT) is a promising approach in cancer immunotherapy. Oncolytic viruses (OVs) could be applied in cancer immunotherapy without in-depth knowledge of tumor antigens. The capability of genetic modification makes OVs exciting therapeutic tools with a high potential for manipulation. Improving efficacy, employing immunostimulatory elements, changing the immunosuppressive tumor microenvironment (TME) to inflammatory TME, optimizing their delivery system, and increasing the safety are the main areas of OVs manipulations. Recently, the reciprocal interaction of OVs and TME has become a hot topic for investigators to enhance the efficacy of OVT with less off-target adverse events. Current investigations suggest that the main application of OVT is to provoke the antitumor immune response in the TME, which synergize the effects of other immunotherapies such as immune-checkpoint blockers and adoptive cell therapy. In this review, we focused on the effects of OVs on the TME and antitumor immune responses. Furthermore, OVT challenges, including its moderate efficiency, safety concerns, and delivery strategies, along with recent achievements to overcome challenges, are thoroughly discussed.

Combination of NDRG2 overexpression, X-ray radiation and docetaxel enhances apoptosis and inhibits invasiveness properties of LNCaP cells

OBJECTIVE

N-myc downstream regulated gene 2 (NDRG2) is identified as a promising candidate tumor suppressor in several human malignancies including prostate cancer (PCa). Here, we investigated the effect of combined NDRG2 overexpression, x-ray radiation (RTX), and docetaxel (DTX) against viability and invasiveness properties of LNCaP cells.

MATERIAL AND METHODS

A plasmid harboring NDRG2 gene under transcriptional control of prostate-specific enhancing sequence regulatory element was constructed to overexpress NDRG2 in PCa cell lines. The effects of NDRG2 overexpression in combination with RTX and DTX on viability, proliferation, and apoptosis of LNCaP cells were evaluated using MTT, colony formation, and annexin V flowcytometirc assays. Migration and invasion of NDRG2-overexpressed cells as well as expression of matrix metalloproteinses-2 (MMP2) and -9 (MMP9) were also assessed using transwell chamber assay and real-time PCR.

RESULTS

The results of fluorescence microscopy and real-time PCR showed a high and specific overexpression of NDRG2 in LNCaP cells. Overexpression of NDRG2 significantly reduced cell viability and increased apoptosis of LNCaP cell. Migration, invasion, as well as the expression of MMP2 and MMP9, was decreased following NDRG2 overexpression. Combination of NDRG2 overexpression with RTX and DTX decreased the viability, invasion, and migration of LNCaP cells synergistically.

CONCLUSION

These results indicate that a combination of NDRG2 overexpression with chemotherapy and radiotherapy can be considered for effective treatment of PCa.

Improving adenoviral vectors and strategies for prostate cancer gene therapy

Gene therapy has been evaluated for the treatment of prostate cancer and includes the application of adenoviral vectors encoding a suicide gene or oncolytic adenoviruses that may be armed with a functional transgene. In parallel, versions of adenoviral vector expressing the p53 gene (Ad-p53) have been tested as treatments for head and neck squamous cell carcinoma and non-small cell lung cancer. Although Ad-p53 gene therapy has yielded some interesting results when applied to prostate cancer, it has not been widely explored, perhaps due to current limitations of the approach. To achieve better functionality, improvements in the gene transfer system and the therapeutic regimen may be required. We have developed adenoviral vectors whose transgene expression is controlled by a p53-responsive promoter, which creates a positive feedback mechanism when used to drive the expression of p53. Together with improvements that permit efficient transduction, this new approach was more effective than the use of traditional versions of Ad-p53 in killing prostate cancer cell lines and inhibiting tumor progression. Even so, gene therapy is not expected to replace traditional chemotherapy but should complement the standard of care. In fact, chemotherapy has been shown to assist in viral transduction and transgene expression. The cooperation between gene therapy and chemotherapy is expected to effectively kill tumor cells while permitting the use of reduced chemotherapy drug concentrations and, thus, lowering side effects. Therefore, the combination of gene therapy and chemotherapy may prove essential for the success of both approaches.

Safety of an Oncolytic Myxoma Virus in Dogs with Soft Tissue Sarcoma

Many oncolytic viruses that are efficacious in murine cancer models are ineffective in humans. The outcomes of oncolytic virus treatment in dogs with spontaneous tumors may better predict human cancer response and improve treatment options for dogs with cancer. The objectives of this study were to evaluate the safety of treatment with myxoma virus lacking the serp2 gene (MYXVΔserp2) and determine its immunogenicity in dogs. To achieve these objectives, dogs with spontaneous soft tissue sarcomas were treated with MYXVΔserp2 intratumorally (n = 5) or post-operatively (n = 5). In dogs treated intratumorally, clinical scores were recorded and tumor biopsies and swabs (from the mouth and virus injection site) were analyzed for viral DNA at multiple time-points. In all dogs, blood, urine, and feces were frequently collected to evaluate organ function, virus distribution, and immune response. No detrimental effects of MYXVΔserp2 treatment were observed in any canine cancer patients. No clinically significant changes in complete blood profiles, serum chemistry analyses, or urinalyses were measured. Viral DNA was isolated from one tumor swab, but viral dissemination was not observed. Anti-MYXV antibodies were occasionally detected. These findings provide needed safety information to advance clinical trials using MYXVΔserp2 to treat patients with cancer.

Advances in the mechanisms of action of cancer-targeting oncolytic viruses

Cancer virotherapy mediated by oncolytic viruses (OV), has emerged as a novel and effective strategy in cancer therapeutics. Preclinical models have demonstrated anticancer activity against numerous types of cancer. Currently, a number of recombinant viruses are in late phase clinical trials, many of which have demonstrated promising results regarding the safety and reliability of the treatments, particularly when combined with standard antineoplastic therapies. In addition to molecular-targeted therapeutics, genetic engineering of the viruses allows functional complementation to chemotherapy or radiotherapy agents. Co-administration of chemotherapy or radiotherapy is imperative for an effective treatment regime. Additionally, these approaches may be used in combination with current treatments to assist in cancer management. The near future may reveal whether this renewed interest in oncological virotherapy will result in meaningful therapeutic effects in patients. The aim of the present review was to highlight how the knowledge of oncolytic viral specificity and cytotoxicity has advanced in recent years, with a view to discuss OV in clinical application and the future directions of this field.

Targeting strategies of adenovirus‑mediated gene therapy and virotherapy for prostate cancer (Review)

Prostate cancer (PCa) poses a high risk to older men and it is the second most common type of male malignant tumor in western developed countries. Additionally, there is a lack of effective therapies for PCa at advanced stages. Novel treatment strategies such as adenovirus-mediated gene therapy and virotherapy involve the expression of a specific therapeutic gene to induce death in cancer cells, however, wild-type adenoviruses are also able to infect normal human cells, which leads to undesirable toxicity. Various PCa-targeting strategies in adenovirus-mediated therapy have been developed to improve tumor-targeting effects and human safety. The present review summarizes the relevant knowledge regarding available adenoviruses and PCa-targeting strategies. In addition, future directions in this area are also discussed. In conclusion, although they remain in the early stages of basic research, adenovirus-mediated gene therapy and virotherapy are expected to become important therapies for tumors in the future due to their potential targeting strategies.

On the potential of oncolytic virotherapy for the treatment of canine cancers

Over 6 million dogs are diagnosed with cancer in the USA each year. Treatment options for many of these patients are limited. It is important that the veterinary and scientific communities begin to explore novel treatment protocols for dogs with cancer. Oncolytic viral therapy is a promising treatment option that may prove to be relatively inexpensive and effective against several types of cancer. The efficacy of oncolytic virus therapies has been clearly demonstrated in murine cancer models, but the positive outcomes observed in mice are not always seen in human cancer patients. These therapies should be thoroughly evaluated in dogs with spontaneously arising cancers to provide needed information about the potential effectiveness of virus treatment for human cancers and to promote the health of our companion animals. This article provides a review of the results of oncolytic virus treatment of canine cancers.