Telomerase-dependent oncolytic adenovirus sensitizes human cancer cells to ionizing radiation via inhibition of DNA repair machinery

Natural oncolytic activity of live-attenuated measles virus against human lung and colorectal adenocarcinomas

Lung and colorectal cancers are responsible for approximately 2 million deaths each year worldwide. Despite continual improvements, clinical management of these diseases remains challenging and development of novel therapies with increased efficacy is critical to address these major public health issues. Oncolytic viruses have shown promising results against cancers that are resistant to conventional anticancer therapies. Vaccine strains of measles virus (MV) exhibit such natural antitumor properties by preferentially targeting cancer cells. We tested the ability of live-attenuated Schwarz strain of MV to specifically infect tumor cells derived from human lung and colorectal adenocarcinomas and demonstrated that live-attenuated MV exhibits oncolytic properties against these two aggressive neoplasms. We also showed that Schwarz MV was able to prevent uncontrollable growth of large, established lung and colorectal adenocarcinoma xenografts in nude mice. Moreover, MV oncolysis is associated with in vivo activation of caspase-3 in colorectal cancer model, as shown by immunohistochemical staining. Our results provide new arguments for the use of MV as an antitumor therapy against aggressive human malignancies.

Enhanced antitumor efficacy of telomerase-specific oncolytic adenovirus with valproic acid against human cancer cells

Replication-selective oncolytic viruses are being developed for human cancer therapy. We previously developed an attenuated adenovirus (OBP-301, Telomelysin), in which the human telomerase reverse transcriptase promoter element drives expression of E1A and E1B genes linked with an internal ribosome entry site. OBP-301 can replicate in, and causes selective lysis of, human cancer cells. Valproic acid (VPA), which is an effective antiepileptic drug, is known to inhibit the histone deacetylase activities. We determined whether the antitumor effect of OBP-301 could be enhanced by VPA in human lung cancer cells. In an in vitro cell viability assay, OBP-301 infection killed four human lung cancer cell lines, H1299, H1299-R5 (a subline of H1299 with a low level of the coxsackievirus and adenovirus receptor (CAR) expression), H460, and A549, more efficiently in the presence of VPA than in its absence. VPA treatment increased CAR expression in all the four lung cancer cells. Consistent with their CAR upregulation, the infection efficiency of adenoviruses in the presence of VPA was significantly higher than that in its absence. The molecular mechanism of this combined effect could be explained by an increase in adenovirus infectivity via VPA-mediated upregulation of CAR. These results suggest that treatment with OBP-301 in combination with VPA is a promising strategy for human lung cancer.

Role of MRE11 in cell proliferation, tumor invasion, and DNA repair in breast cancer

BACKGROUND

Previous studies have shown that altered forms of MRE11, a protein known to play a vital role in DNA double-strand break repair, DNA replication, and telomere maintenance are associated with cancer outcomes. We investigated the role of MRE11 in breast cancer in both clinical and in vitro settings.

METHODS

We examined MRE11 expression in tumor tissues from invasive ductal carcinoma breast cancer patients (n = 254) by immunohistochemistry, and associations with clinicopathological characteristics and overall survival were assessed using Cox proportional hazards regression models and Kaplan-Meier survival curves. Effect of MRE11 overexpression and knockdown on cell proliferation, invasion, and radioresistance was assessed in vitro using breast cancer cell lines (MCF-7 and MDA-MB-231). We also investigated the mechanisms involved. Effect of MRE11 overexpression on tumor growth was assessed in an orthotopic xenograft model (n = 8 mice per group). All statistical tests were two-sided.

RESULTS

Of the 254 tissue samples, 69.3% and 30.7% showed high and low MRE11 expression, respectively. High MRE11 expression was statistically significantly associated with malignant cancer behavior compared with low MRE11 expression (eg, stages III and IV vs stage I, P = .004; poor overall survival, P = .005). MRE11 overexpression in breast cancer cell lines promoted cell proliferation through STAT3, cell cycle entry, invasion and migration, and radioresistance via enhanced DNA repair activity and also inhibited apoptosis; knockdown of MRE11 had the opposite effect. In xenograft tumor-bearing mice (n = 8 per group), increased tumor growth was observed in the MRE11-overexpressing group compared with the control group (tumor volume at week 8, control vs MRE11-overexpressing tumor originating from MCF-7 cells, mean = 280.4 mm(3), 95% confidence interval [CI] = 62.4 to 498.4 mm(3) vs mean = 631.0 mm(3), 95% CI = 296.9 to 965.0 mm(3), P = .043).

CONCLUSION

High MRE11 expression was associated with a more malignant behavior in breast cancer. MRE11 may be a novel oncoprotein and may therefore serve as a new therapeutic intervention against breast cancer.

Biodistribution and safety assessment of bladder cancer specific recombinant oncolytic adenovirus in subcutaneous xenografts tumor model in nude mice

BACKGROUND

The previous works about safety evaluation for constructed bladder tissue specific adenovirus are poorly documented. Thus, we investigated the biodistribution and body toxicity of bladder specific oncolytic adenovirus Ad-PSCAE-UPII-E1A (APU-E1A) and Ad-PSCAE-UPII-E1A-AR (APU-E1A-AR), providing meaningful information prior to embarking on human clinical trials.

MATERIALS AND METHOD

Conditionally replicate recombinant adenovirus (CRADs) APU-E1A, APU-EIA-AR were constructed with bladder tissue specific UroplakinII(UPII) promoter to induce the expression of Ad5E1A gene and E1A-AR fusing gene, and PSCAE was inserted at upstream of promoter to enhance the function of promoter. Based on the cytopathic and anti-tumor effect of bladder cancer, these CRADs were intratumorally injected into subcutaneous xenografts tumor in nude mice. We then determined the toxicity through general health and behavioral assessment, hepatic and hematological toxicity evaluation, macroscopic and microscopic postmortem analyses. The spread of the transgene E1A of adenovirus was detected with RT-PCR and Western blot. Virus replication and distribution were examined with APU-LUC administration and Luciferase Assay.

RESULTS

General assessment and body weight of the animals did not reveal any alteration in general behavior. The hematological alterations of groups which were injected with 5x10(8) pfu or higher dose (5x10(9) pfu) of APU-E1A and APU-E1A-AR showed no difference in comparison with PBS group, and only slight increased transaminases in contrast to PBS group at 5x10(9) pfu of APU-E1A and APU-E1A-AR were observed. E1A transgene did not disseminate to organs outside of xenograft tumor. Virus replication was not detected in other organs beside tumor according to Luciferase Assay.

CONCLUSIONS

Our study showed that recombinant adenovirus APU-E1A-AR and APU-E1A appear safe with 5x10(7) pfu and 5x10(8) pfu intratumorally injection in mice, without any discernable effects on general health and behavior.

Is telomerase a viable target in cancer?

The ideal cancer treatment would specifically target cancer cells yet have minimal or no adverse effects on normal somatic cells. Telomerase, the ribonucleoprotein reverse transcriptase that maintains the ends of human chromosome, is an attractive cancer therapeutic target for exactly this reason [1]. Telomerase is expressed in more than 85% of cancer cells, making it a nearly universal cancer marker, while the majority of normal somatic cells are telomerase negative. Telomerase activity confers limitless replicative potential to cancer cells, a hallmark of cancer which must be attained for the continued growth that characterizes almost all advanced neoplasms [2]. In this review we will summarize the role of telomeres and telomerase in cancer cells, and how properties of telomerase are being exploited to create targeted cancer therapies including telomerase inhibitors, telomerase-targeted immunotherapies and telomerase-driven virotherapies. A frank and balanced assessment of the current state of telomerase inhibitors with caveats and potential limitations will be included.

Oncolytic adenovirus expressing soluble TGFβ receptor II-Fc-mediated inhibition of established bone metastases: a safe and effective systemic therapeutic approach for breast cancer

In recent years, oncolytic adenoviruses have shown some promise as a novel class of antitumor agents. However, their utility in targeting bone metastases is relatively less studied. We have examined whether the systemic therapy of oncolytic adenoviruses expressing the soluble form of transforming growth factor-β (TGFβ) receptor II fused with human immunoglobulin G1 can be developed for the treatment of established breast cancer bone metastases. MDA-MB-231-luc2 human breast cancer cells were injected in the left heart ventricle of nude mice to establish bone metastasis. Mice with hind limb tumors were administered (on days 8 and 11) oncolytic adenoviruses-Ad.sTβRFc or mhTERTAd.sTβRFc. Skeletal tumor growth was monitored weekly by bioluminescence imaging (BLI) and radiography. At the termination time on day 28, hind limb bones were analyzed for tumor burden, synchrotron micro-computed tomography, and osteoclast activation. Intravenous delivery of Ad.sTβRFc and mhTERTAd.sTβRFc induced significant inhibition of tumor growth, reduction of tumor burden, osteoclast activation, and increased animals' survival. Oncolytic adenoviruses were safer than dl309, a wild-type virus. A slight elevation of liver enzyme activity was observed after Ad.sTβRFc administration; this subsided with time. Based on these studies, we believe that Ad.sTβRFc and mhTERTAd.sTβRFc can be developed as a safe and effective approach for the treatment of established bone metastasis.