Examination of the optimal condition on the in vitro sensitivity to telomelysin in head and neck cancer cell lines

Oncolytic Virotherapy: A New Paradigm in Cancer Immunotherapy

Oncolytic viruses (OVs) are emerging as potential treatment options for cancer. Natural and genetically engineered viruses exhibit various antitumor mechanisms. OVs act by direct cytolysis, the potentiation of the immune system through antigen release, and the activation of inflammatory responses or indirectly by interference with different types of elements in the tumor microenvironment, modification of energy metabolism in tumor cells, and antiangiogenic action. The action of OVs is pleiotropic, and they show varied interactions with the host and tumor cells. An important impediment in oncolytic virotherapy is the journey of the virus into the tumor cells and the possibility of its binding to different biological and nonbiological vectors. OVs have been demonstrated to eliminate cancer cells that are resistant to standard treatments in many clinical trials for various cancers (melanoma, lung, and hepatic); however, there are several elements of resistance to the action of viruses per se. Therefore, it is necessary to evaluate the combination of OVs with other standard treatment modalities, such as chemotherapy, immunotherapy, targeted therapies, and cellular therapies, to increase the response rate. This review provides a comprehensive update on OVs, their use in oncolytic virotherapy, and the future prospects of this therapy alongside the standard therapies currently used in cancer treatment.

Oncolytic virotherapy evolved into the fourth generation as tumor immunotherapy

BACKGROUND

Oncolytic virotherapy (OVT) is a promising anti-tumor modality that utilizes oncolytic viruses (OVs) to preferentially attack cancers rather than normal tissues. With the understanding particularly in the characteristics of viruses and tumor cells, numerous innovative OVs have been engineered to conquer cancers, such as Talimogene Laherparepvec (T-VEC) and tasadenoturev (DNX-2401). However, the therapeutic safety and efficacy must be further optimized and balanced to ensure the superior safe and efficient OVT in clinics, and reasonable combination therapy strategies are also important challenges worthy to be explored.

MAIN BODY

Here we provided a critical review of the development history and status of OVT, emphasizing the mechanisms of enhancing both safety and efficacy. We propose that oncolytic virotherapy has evolved into the fourth generation as tumor immunotherapy. Particularly, to arouse T cells by designing OVs expressing bi-specific T cell activator (BiTA) is a promising strategy of killing two birds with one stone. Amazing combination of therapeutic strategies of OVs and immune cells confers immense potential for managing cancers. Moreover, the attractive preclinical OVT addressed recently, and the OVT in clinical trials were systematically reviewed.

CONCLUSION

OVs, which are advancing into clinical trials, are being envisioned as the frontier clinical anti-tumor agents coming soon.

An oncolytic virus as a promising candidate for the treatment of radioresistant oral squamous cell carcinoma

We evaluated the usefulness of an oncolytic virus (Suratadenoturev; OBP-301) against radioresistant oral squamous cell carcinoma. We confirmed the expression of human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor in cell lines. Also, we examined the potential presence in a patient who has received existing therapy that is amenable to treatment with OBP-301. We evaluated: (1) the antitumor effects of OBP-301 alone and in combination with radiotherapy on radioresistant cell lines, (2) the molecular mechanism underlying the radiosensitizing effect and cell death increased by the combination therapy, and (3) the antitumor effect of the combination therapy in vivo using xenograft models (a radioresistant cell line-derived xenograft in mouse and a patient-derived xenograft). Human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor were expressed in all cell lines. OBP-301 decreased the proliferative activity of these cell lines in a concentration-dependent manner, and significantly enhanced the antitumor effect of irradiation. Phosphorylated STAT3 and its downstream molecules, which correlated with apoptosis and autophagy, showed significant changes in expression after treatment with OBP-301. The combination therapy exerted a significant antitumor effect versus radiotherapy alone in both xenograft models. Combination of OBP-301 with radiotherapy exerts a synergistic effect and may represent a promising treatment for radioresistant oral squamous cell carcinoma.

Natural and Designed Toxins for Precise Therapy: Modern Approaches in Experimental Oncology

Cancer cells frequently overexpress specific surface receptors providing tumor growth and survival which can be used for precise therapy. Targeting cancer cell receptors with protein toxins is an attractive approach widely used in contemporary experimental oncology and preclinical studies. Methods of targeted delivery of toxins to cancer cells, different drug carriers based on nanosized materials (liposomes, nanoparticles, polymers), the most promising designed light-activated toxins, as well as mechanisms of the cytotoxic action of the main natural toxins used in modern experimental oncology, are discussed in this review. The prospects of the combined therapy of tumors based on multimodal nanostructures are also discussed.

Systemic Management for Advanced Hepatocellular Carcinoma: A Review of the Molecular Pathways of Carcinogenesis, Current and Emerging Therapies, and Novel Treatment Strategies

Hepatocellular carcinoma (HCC) arises from a number of cirrhosis-related and non-cirrhosis-related exposures and is one of the leading causes of cancer-related deaths worldwide. Achieving a durable cure currently relies on either resection or transplantation, but since most patients will be diagnosed with inoperable disease, there is great interest in achieving more effective systemic therapies. At a molecular level, HCC is heterogeneous, but initial treatment strategies, including the use of multi-targeted tyrosine kinase inhibitors and checkpoint inhibitors, have been fairly homogenous, depending on general host factors and overall tumor burden rather than specific molecular signatures. Over the past 2 decades, however, there has been significant success in identifying key molecular targets, including driver mutations involving the telomerase reverse transcriptase, p53, and beta-catenin genes, and significant work is now being devoted to translating these discoveries into the development of robust and well-tolerated targeted therapies. Furthermore, multi-modal therapies have also begun to emerge, harnessing possible synergism amongst a variety of different treatment classes. As the findings of these landmark trials become available over the next several years, the landscape of the systemic management of advanced HCC will change significantly.

Disassembling a cancer puzzle: Cell junctions and plasma membrane as targets for anticancer therapy

Despite an enhanced permeability and retention effect typical of many solid tumors, drug penetration is not always sufficient. Possible strategies for the drug delivery improvement are a modification of the tumor cell-to-cell junctions and usage of cell membrane permeabilization proteins. In this review we discuss epithelial cell junctions as targets for a combined anticancer therapy and propose new possible sources of such agents. We suggest considering viral and bacterial pathogens disrupting epithelial layers as plentiful sources of new therapeutic agents for increasing tumor permeability for other effector agents. We also observe the application of pore forming proteins and peptides of different origin for cytoplasmic delivery of anti-cancer agents and consider the main obstacles of their use in vivo.

Antitumor effects of telomerase-specific replication-selective oncolytic viruses for adenoid cystic carcinoma cell lines

We evaluated the antitumor effect of a telomerase-specific replication-selective adenovirus (Telomelysin, OBP-301) for adenoid cystic carcinoma (ACC) in vitro and in vivo. Adenovirus E1 gene expression was controlled by human telomerase reverse transcription (hTERT). Infection of ACC cells by OBP-301 induced high E1A mRNA expression and subsequent oncolytic cell death in a dose-dependent manner. Using OBP-401 (TelomeScan), a genetically engineered adenovirus that carries the GFP gene under the control of the cytomegalovirus (CMV) promoter at the deleted E3 region of OBP-301, ACC cells expressed bright GFP fluorescence as early as 12 h after OBP-401 infection. The fluorescence intensity gradually increased in a time-dependent manner, followed by rapid cell death due to the cytopathic effect of OBP-401, as evidenced by the floating, highly light-refractive cells using phase-contrast microscopy. Effects of intratumorally injected OBP-401 against established Acc2 xenograft tumors were seen in BALB/c nu/nu mice. The levels of GFP expression following ex vivo infection of OBP-401 may be of value as a positive predictive marker for the outcome of telomerase-specific virotherapy. Our data clearly indicated that telomerase-specific oncolytic adenoviruses have significant therapeutic potential against human ACC in vitro and in vivo. These results suggest that treatment with OBP-301 and OBP-401 may improve the quality of life of oral cancer patients.

Telomerase-specific oncolytic adenovirus: antitumor effects on radiation-resistant head and neck squamous cell carcinoma cells

BACKGROUND

Radioresistance remains a critical issue in the use of radiotherapy for the treatment of head and neck squamous cell carcinoma (HNSCC). This study evaluated the efficacy of combination treatment with OBP-301, a telomerase-specific replication-selective adenovirus, and radiotherapy in overcoming radioresistance by examining its effect on radiation-resistant HNSCC cells.

METHODS

Radiation-resistant HNSCC cells were treated with OBP-301 and radiation in vitro and in an orthotopic nude mouse model in vivo and synergism was assessed. Apoptosis and expression of MRN complex, which plays a key role in DNA repair machinery, were also analyzed.

RESULTS

Infection with OBP-301 was found to enhance the antitumor efficacy of radiation both in vitro and in vivo by inhibiting MRN complex expression and increasing apoptosis induction.

CONCLUSION

Combined OBP-301 and radiation therapy seems to overcome radioresistance in HNSCC cells by inhibiting DNA repair machinery, and may thus be a novel therapeutic strategy for treating HNSCC.