Phase I/II adenoviral p53 gene therapy for chemoradiation resistant advanced esophageal squamous cell carcinoma

Gene Therapy Targeting p53 and KRAS for Colorectal Cancer Treatment: A Myth or the Way Forward?

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy worldwide and is responsible as one of the main causes of mortality in both men and women. Despite massive efforts to raise public awareness on early screening and significant advancements in the treatment for CRC, the majority of cases are still being diagnosed at the advanced stage. This contributes to low survivability due to this cancer. CRC patients present various genetic changes and epigenetic modifications. The most common genetic alterations associated with CRC are p53 and KRAS mutations. Gene therapy targeting defect genes such as TP53 (tumor suppressor gene encodes for p53) and KRAS (oncogene) in CRC potentially serves as an alternative treatment avenue for the disease in addition to the standard therapy. For the last decade, significant developments have been seen in gene therapy for translational purposes in treating various cancers. This includes the development of vectors as delivery vehicles. Despite the optimism revolving around targeted gene therapy for cancer treatment, it also has various limitations, such as a lack of availability of related technology, high cost of the involved procedures, and ethical issues. This article will provide a review on the potentials and challenges of gene therapy targeting p53 and KRAS for the treatment of CRC.

Differential p53-Mediated Cellular Responses to DNA-Damaging Therapeutic Agents

The gene TP53, which encodes the tumor suppressor protein p53, is mutated in about 50% of cancers. In response to cell stressors like DNA damage and after treatment with DNA-damaging therapeutic agents, p53 acts as a transcription factor to activate subsets of target genes which carry out cell fates such as apoptosis, cell cycle arrest, and DNA repair. Target gene selection by p53 is controlled by a complex regulatory network whose response varies across contexts including treatment type, cell type, and tissue type. The molecular basis of target selection across these contexts is not well understood. Knowledge gained from examining p53 regulatory network profiles across different DNA-damaging agents in different cell types and tissue types may inform logical ways to optimally manipulate the network to encourage p53-mediated tumor suppression and anti-tumor immunity in cancer patients. This may be achieved with combination therapies or with p53-reactivating targeted therapies. Here, we review the basics of the p53 regulatory network in the context of differential responses to DNA-damaging agents; discuss recent efforts to characterize differential p53 responses across treatment types, cell types, and tissue types; and examine the relevance of evaluating these responses in the tumor microenvironment. Finally, we address open questions including the potential relevance of alternative p53 transcriptional functions, p53 transcription-independent functions, and p53-independent functions in the response to DNA-damaging therapeutics.

Combination of rAd-p53 in situ gene therapy and anti-PD-1 antibody immunotherapy induced anti-tumor activity in mouse syngeneic urogenital cancer models

In this study we undertook a novel combination therapy using rAd-p53 in situ gene therapy and immunotherapy with immune checkpoint inhibitor (ICI) anti-PD-1 antibody for urogenital cancers. Three mouse syngeneic tumor cell lines, TRAMP-C2 (prostate cancer derived from C57BL/6 mice), MBT-2 (bladder cancer derived from C3H mice) and Renca (kidney cancer derived from BALB/c mice) were used in this study. The highest coxsackie and adenovirus receptor (CAR) mRNA expression was observed in TRAMP-C2 cells, followed by Renca and then MBT-2 cells. Consistent with the CAR expressions, rAd-p53 at 160 multiplicity of infection (MOI) significantly inhibited the cell proliferation of TRAMP-C2 and Renca cells, but not MBT-2 cells. In in vivo experiments, the combination of intratumoral injections of rAd-p53 (1 × 10⁹ plaque-forming units) every other day and intraperitoneal injections of anti-mouse PD-1 antibody (200 μg) twice a week suppressed tumor growth and prolonged survival compared to rAd-p53 or anti-PD-1 antibody monotherapy in both the TRAMP-C2 and Renca models. Our results encourage the clinical development of combination therapy comprised of in situ gene therapy with rAd-p53 and immunotherapy with an ICI anti-PD-1 antibody for urogenital cancers.

The changing face of gastric cancer: epidemiologic trends and advances in novel therapies

Gastric cancer is an aggressive solid-tumor malignancy with poor prognosis. The epidemiologic face of gastric cancer is changing and further insight into its heterogenous immunohistopathologic nature is needed to develop personalized therapies for specific patient populations. In this review, we highlight changes in gastric cancer epidemiology with a special emphasis on racial and ethnic variations and discuss the implications of current clinical and preclinical treatment advances.

The Evolving Landscape of Gene Therapy in Plastic Surgery

With the rapid rise of personalized genomic sequencing and clustered regularly interspaced short palindromic repeat (CRISPR) technology, previous gaps in gene therapy are beginning to be bridged, paving the way for increasing clinical applicability. This article aims to provide an overview of the fundamentals of gene therapy and discuss future potential interventions relevant to plastic surgeons. These interventions include enhancing tissue regeneration and healing, as well as modifying disease processes in congenital anomalies. Though clinical applications are still on the horizon, a deeper understanding of these new advances will help plastic surgeons understand the current landscape of gene therapy and stay abreast of future opportunities.

Multidisciplinary oncolytic virotherapy for gastrointestinal cancer

Replication-selective tumor-specific viruses represent a novel approach for treating neoplastic diseases. These vectors are designed to induce virus-mediated lysis of tumor cells after selective intracellular virus propagation. For targeting cancer cells, the use of tissue- or cell-specific promoters that are expressed in diverse tumor types but silent in normal cells is required. Human telomerase is highly active in more than 85% of primary cancers, regardless of tissue origin, and its activity is closely correlated with human telomerase reverse transcriptase (hTERT) expression. We constructed an attenuated adenovirus 5 vector (telomelysin, OBP-301) in which the hTERT promoter element drives expression of E1 genes. As only tumor cells that express the telomerase can activate this promoter, the hTERT proximal promoter allows for preferential expression of viral genes in tumor cells, leading to selective viral replication and oncolytic cell death. Upon US Food and Drug Administration approval, a phase 1 dose-escalation study of intratumoral injection of telomelysin for various solid tumors has been completed to confirm the safety, tolerability, and feasibility of the agent. Moreover, we found that adenoviral E1B 55-kDa protein in telomelysin inhibits the radiation-induced DNA repair machinery. Thus, tumor cells infected with telomelysin could be rendered sensitive to ionizing radiation. Recently, we assessed the safety and efficacy of intratumoral injection of telomelysin with radiotherapy in esophageal cancer patients not suited for standard treatments. This review highlights some very promising clinical advances in cancer therapeutic technologies using telomerase-specific oncolytic virotherapy.

Prostate Cancer Gene Regulatory Network Inferred from RNA-Seq Data

BACKGROUND

Cancer is a complex disease with a lucid etiology and in understanding the causation, we need to appreciate this complexity.

OBJECTIVE

Here we are aiming to gain insights into the genetic associations of prostate cancer through a network-based systems approach using the BC3Net algorithm.

METHODS

Specifically, we infer a prostate cancer Gene Regulatory Network (GRN) from a large-scale gene expression data set of 333 patient RNA-seq profiles obtained from The Cancer Genome Atlas (TCGA) database.

RESULTS

We analyze the functional components of the inferred network by extracting subnetworks based on biological process information and interpret the role of known cancer genes within each process. Fur-thermore, we investigate the local landscape of prostate cancer genes and discuss pathological associa-tions that may be relevant in the development of new targeted cancer therapies.

CONCLUSION

Our network-based analysis provides a practical systems biology approach to reveal the collective gene-interactions of prostate cancer. This allows a close interpretation of biological activity in terms of the hallmarks of cancer.

Gene Therapy in Head and Neck Cancer

Although overall cancer death rates are decreasing, comparative improvements in head and neck squamous cell cancer are modest. Although new advances targeting immune checkpoints may soon improve these numbers, additional research for new therapeutic options is vital. One potential treatment avenue is the use of gene therapy. This article provides insight into some gene therapy targets and varied techniques being evaluated for patients with head and neck cancer. Techniques include corrective gene therapy, cytoreductive gene therapy, and gene editing, in addition to a discussion on gene therapy vectors.

Recombinant adenovirus p53 combined with radiotherapy improves efficacy and safety in the treatment of head and neck lymphoma

OBJECTIVE

Lymphoma is considered to be a kind of malignant tumour. Gene therapy and radiotherapy have been reported as treatment methods for head and neck lymphoma. This study aims to evaluate the efficacy and safety for the treatment of head and neck lymphoma by a combination of recombinant adenovirus p53 (rAd-p53) and radiotherapy.

METHODS

A total of 156 patients with head and neck lymphoma were selected. All patients received an intratumor injection of rAd-p53 of four different doses, namely, 0, 1 × 1010 VP, 1 × 1011 VP and 1 × 1012 VP, once a week for 8 weeks, and radiotherapy was administered 3 days after the rAd-p53 injection using the same dosage and method. Four, eight and twelve weeks after treatment, tumor reduction and complete response (CR) rates, special laboratory examination and adverse reaction assessment were detected to evaluate the efficacy and safety of combined treatment with rAd-p53 injection and radiotherapy for head and neck lymphoma.

RESULTS

At week 4, 8 and 12 of treatment with rAd-p53 at the 1 × 1010 VP, 1 × 1011 VP and 1 × 1012 VP doses, the average tumour reduction and CR rates were evidently elevated, the anti rAd-p53 antibody in the serum of patients was expressed positively, and the T cell subsets (CD3/CD4/CD8) increased and interleukin 2 receptor (IL-2R) level decreased markedly. Additionally, rAd-p53 was proven to be clinically safe in the treatment.

CONCLUSION

Altogether, we conclude that rAd-p53 combined with radiotherapy improves the efficacy and safety in treating head and neck lymphoma, which has a broad scope in future clinical application.

Recombinant adenovirus-p53 enhances the therapeutic effect of surgery and chemoradiotherapy combination in hypopharyngeal squamous cell carcinomas patients

The purpose of our study was to assess the safety and efficacy of recombinant adenovirus-p53 (rAd-p53) combined with surgery and chemoradiotherapy (CRT) for patients with hypopharyngeal squamous cell carcinomas (HPSCC). This study retrospectively and consecutively collected clinical data of 102 patients with primary HPSCC who were admitted to the Department of Otolaryngology of West China Hospital, Sichuan University in China between March 2010 and December 2015. A retrospective clinical study of 102 patients with HPSCC was carried out from March 2010 to December 2015. All patients were male and were divided into 3 groups based on the treatments they received, including Single Surgery, Surgery + CRT, and Surgery + CRT + rAd-p53. In the Surgery + CRT + rAd-p53 group, rAd-p53 was intratumorally injected on the 1st day preoperatively; peritumorally injected on the 7th day intraoperatively, and on the 21st, 28th, and 35th days postoperatively. Their clinical data were retrospectively collected and analyzed. In our study, for all 102 patients with HPSCC, 16 patients received Single Surgery, 44 patients received Surgery + CRT therapy, and 42 patients received Surgery + CRT + rAd-p53 therapy. In the Surgery + CRT + rAd-p53 group, all patients could tolerate rAd-p53 treatment and no serious side effect was observed. In addition, rAd-p53 application did not increase the side reactions caused by surgery and CRT. Compared with the 3-year overall survival rates of Single Surgery group and Surgery + CRT group, the 3-year overall survival rates of Surgery + CRT + rAd-p53 group was significantly enhanced (P < .05). Similar results were also observed for the 3-year disease-free survival rates. Our results indicate that rAd-p53 therapy may improve the therapeutic effect of patients with HPSCC, and is a safe and effective treatment method for patients with HPSCC. However, further prospective studies with larger sample sizes are needed to validate our findings.

p53 molecular approach to diagnosis and treatment of esophageal squamous cell carcinoma

We reviewed our research concerning p53 molecules in esophageal squamous cell carcinoma by focusing on the p53 molecular diagnosis and treatment of esophageal squamous cell carcinoma. First, we developed diagnostic tools to analyze serum p53 autoantibodies to detect esophageal squamous cell carcinoma. Positive rate was around 25% to 30% in all patients and around 20% even in stage I patients. Presence of serum p53 antibodies was significantly associated with overexpression of p53 protein in tumor cells. Seropositive patients were more likely than seronegative patients to be resistant to chemotherapy. Monitoring of the titer of serum p53 autoantibodies was useful in predicting patients at high risk of recurrence and/or treatment response. Second, using Ad5CMV-p53 for 10 patients with advanced esophageal squamous cell carcinoma, we carried out a phase I/II study of adenoviral-mediated p53 gene therapy. Although no complete response was observed, local tumor was stabilized in nine patients. No serious adverse events related to Ad5CMV-p53 were observed in these patients. One patient survived for over 5 years after the start of p53 gene therapy. Intratumoral injection of Ad5CMV-p53 is therefore safe, feasible, and biologically active when given in multiple doses to patients with esophageal squamous cell carcinoma. Our observations from these clinical studies indicate that p53 is a useful molecular target both in the diagnosis and in the treatment of esophageal squamous cell carcinoma.

TP53 Mutation in Correlation to Immunohistochemical Expression of P53 Protein in Patients with Hepatocellular Carcinoma

BACKGROUND:

Mutations causing p53 inactivation are among the most common genetic alterations in human malignant tumours including hepatocellular carcinoma. Detection of p53 gene mutations in patients with hepatocellular carcinoma (HCC) should provide relevant data for the patients from the Republic of Macedonia and should allow the survivals additional therapeutic option as is gene therapy.

AIM:

We aimed to detect p53 gene mutations in HCC tissue, and to correlate them with the immunoexpression of p53 protein and multiple clinicopathologic characteristics of a tumour.

MATERIAL AND METHODS:

We analysed thirty patients with HCC for multiple clinic-pathological characteristics. Tumour tissue samples were immunostained for p53 and detection of p53 gene mutations was performed by polymerase chain reaction followed by Sanger sequencing.

RESULTS:

Changes in p53 gene sequence were detected in four patients (13.33%), one of them a polymorphism and the other three were missense point mutations with p53 immunoexpression of 50%, 0%, 0% and 90%, respectively. All patients with p53 mutations had cirrhosis. Two of them had Hepatitis B infection, moderately differentiated tumour and T2 status. There was one case with a well-differentiated tumour and one with T4 status. All of them were with vascular invasion. The size of the tumours was in the range of 2.5 cm to 16 cm. All 3 mutations were located in exon 7.

CONCLUSION:

Mutations in p53 gene are not always associated with obviously altered immunoexpression of p53 protein. Detection of p53 gene mutations is necessary in each case because the new therapeutic modalities offer to apply gene therapy.

When the guardian sleeps: Reactivation of the p53 pathway in cancer

The p53 tumor suppressor is inactivated in most cancers, thus suggesting that loss of p53 is a prerequisite for tumor growth. Therefore, its reintroduction through different means bears great clinical potential. After a brief introduction to current knowledge of p53 and its regulation by the ubiquitin-ligases MDM2/MDMX and post-translational modifications, we will discuss small molecules that are able to reactivate specific, frequently observed mutant forms of p53 and their applicability for clinical purposes. Many malignancies display amplification of MDM genes encoding negative regulators of p53 and therefore much effort to date has concentrated on the development of molecules that inhibit MDM2, the most advanced of which are being tested in clinical trials for sarcoma, glioblastoma, bladder cancer and lung adenocarcinoma. These will be discussed as will recent findings of MDMX inhibitors: these are of special importance as it has been shown that cancers that become resistant to MDM2 inhibitors often amplify MDM4. Finally, we will also touch on gene therapy and vaccination approaches; the former of which aims to replace mutated TP53 and the latter whose goal is to activate the body's immune system toward mutant p53 expressing cells. Besides the obvious importance of MDM2 and MDMX expression for regulation of p53, other regulatory factors should not be underestimated and are also described. Despite the beauty of the concept, the past years have shown that many obstacles have to be overcome to bring p53 reactivation to the clinic on a broad scale, and it is likely that in most cases it will be part of a combined therapeutic approach. However, improving current p53 targeted molecules and finding the best therapy partners will clearly impact the future of cancer therapy.

Genomic characterization of esophageal squamous cell carcinoma: Insights from next-generation sequencing

Two major types of cancer occur in the esophagus: squamous cell carcinoma, which is associated with chronic smoking and alcohol consumption, and adenocarcinoma, which typically arises in gastric reflux-associated Barrett’s esophagus. Although there is increasing incidence of esophageal adenocarcinoma in Western counties, esophageal squamous cell carcinoma (ESCC) accounts for most esophageal malignancies in East Asia, including China and Japan. Technological advances allowing for massively parallel, high-throughput next-generation sequencing (NGS) of DNA have enabled comprehensive characterization of somatic mutations in large numbers of tumor samples. Recently, several studies were published in which whole exome or whole genome sequencing was performed in ESCC tumors and compared with matched normal DNA. Mutations were validated in several genes, including in TP53, CDKN2A, FAT1, NOTCH1, PIK3CA, KMT2D and NFE2L2, which had been previously implicated in ESCC. Several new recurrent alterations have also been identified in ESCC. Combining the clinicopathological characteristics of patients with information obtained from NGS studies may lead to the development of effective diagnostic and therapeutic approaches for ESCC. As this research becomes more prominent, it is important that gastroenterologist become familiar with the various NGS technologies and the results generated using these methods. In the present study, we describe recent research approaches using NGS in ESCC.

Relationship between P53 status and prognosis and clinicopathologic characteristics in esophagus squamous cell carcinoma: A systematic review

AIM: To evaluate the prognostic role of p53 status and its relationship with clinicopathologic characteristics in esophagus squamous cell carcinoma (ESCC).

METHODS: A systematic search of PubMed, SCI-Ex-panded, EMBASE, the Cochrane library, China National Knowledge Infrastructure (CNKI), Chinese Biomedical Database (CBM), and science and technology periodical database (VIP) was performed. Related references were also searched for additional clinical studies. Two reviewers independently performed screening of identified studies and data extracting according to inclusion and exclusion criteria. The quality assessment was conducted on the basis of the Newcastle-Ottawa Quality Assessment Scale (NOS). The evaluation of the publication bias of the included studies and data synthesis were performed with RevMan 5.3. A fixed-effect or random effects model was adopted according to heterogeneity.

RESULTS: A total of 85 studies involing 8825 cases met the inclusion criteria. The experimental group (4608 cases) was positive for either p53 gene mutation or protein expression, and the control group (4217 cases) was negative for either p53 gene mutation or protein expression. The pooled hazard ratio (HR) for OS was 1.35 (95%CI: 1.23-1.47, P < 0.00001; heterogeneity: P = 0.39, I² = 5%). The pooled risk ratio (RR) for the 5-year and 3-year survival rates was 0.73 (95%CI: 0.62-0.87, P = 0.0003; heterogeneity: P = 0.001, I² = 50%) and 0.87 (95%CI: 0.74-1.02, P = 0.09; heterogeneity: P = 0.28, I² = 18%). p53 gene mutation or protein expression was significantly associated with poorer T stage (RR = 1.09, P = 0.004), N stage (RR = 1.24, P < 0.00001), M stage (RR = 1.65, P < 0.00001), TNM stage (RR = 1.25, P < 0.00001) and differentiation degree (RR = 1.06, P = 0.03). However, there were no association between P53 status and vascular invasion, tumor location, size, age or gender in ESCC (P>0.05).

CONCLUSION: p53 gene mutation or protein expression abnormality is a marker of poor prognosis in patients with ESCC. Meantime, patients with P53 abnormalities are associated with higher depth of invasion, higher rate of lymph node metastasis and distant metastasis, later TNM stage, and poorer grade of differentiation.

Functional repair of p53 mutation in colorectal cancer cells using trans-splicing

Mutation in the p53 gene is arguably the most frequent type of gene-specific alterations in human cancers. Current p53-based gene therapy contains the administration of wt-p53 or the suppression of mutant p53 expression in p53-defective cancer cells. We hypothesized that trans-splicing could be exploited as a tool for the correction of mutant p53 transcripts in p53-mutated human colorectal cancer (CRC) cells. In this study, the plasmids encoding p53 pre-trans-splicing molecules (PTM) were transfected into human CRC cells carrying p53 mutation. The plasmids carrying p53-PTM repaired mutant p53 transcripts in p53-mutated CRC cells, which resulted in a reduction in mutant p53 transcripts and an induction of wt-p53 simultaneously. Intratumoral administration of adenovirus vectors carrying p53 trans-splicing cassettes suppressed the growth of tumor xenografts. Repair of mutant p53 transcripts by trans-splicing induced cell-cycle arrest and apoptosis in p53-defective colorectal cancer cells in vitro and in vivo. In conclusion, the present study demonstrated for the first time that trans-splicing was exploited as a strategy for the repair of mutant p53 transcripts, which revealed that trans-splicing would be developed as a new therapeutic approach for human colorectal cancers carrying p53 mutation.

Targeting tumor suppressor genes for cancer therapy

Cancer drugs are broadly classified into two categories: cytotoxic chemotherapies and targeted therapies that specifically modulate the activity of one or more proteins involved in cancer. Major advances have been achieved in targeted cancer therapies in the past few decades, which is ascribed to the increasing understanding of molecular mechanisms for cancer initiation and progression. Consequently, monoclonal antibodies and small molecules have been developed to interfere with a specific molecular oncogenic target. Targeting gain-of-function mutations, in general, has been productive. However, it has been a major challenge to use standard pharmacologic approaches to target loss-of-function mutations of tumor suppressor genes. Novel approaches, including synthetic lethality and collateral vulnerability screens, are now being developed to target gene defects in p53, PTEN, and BRCA1/2. Here, we review and summarize the recent findings in cancer genomics, drug development, and molecular cancer biology, which show promise in targeting tumor suppressors in cancer therapeutics.

Replication-competent adenoviruses with the type 35-derived fiber-knob region achieve reactive oxygen species-dependent cytotoxicity and produce greater toxicity than those with the type 5-derived region in pancreatic carcinoma

Pancreatic carcinoma is relatively resistant to chemotherapy and cell death induced by replication of adenoviruses (Ad) can be one of the therapeutic options. Transduction efficacy of conventional type 5 Ad (Ad5) is however low and the cytotoxic mechanism by replication-competent Ad was not well understood. We constructed replication-competent Ad5 of which the E1A promoter region was replaced with a transcriptional regulatory region of the midkine, the survivin or the cyclooxygenase-2 gene, all of which were expressed at a high level in human tumors. We also prepared replication-competent Ad5 that were activated with the same region but had the type 35 Ad-derived fiber-knob region (AdF35) to convert the major cellular receptor for Ad infection from the coxsackie adenovirus receptor to CD46 molecules. Replication-competent AdF35 that were activated with the exogenous region produced cytotoxic effects on human pancreatic carcinoma cells greater than the corresponding Ad5 bearing with the same regulatory region. Cells infected with the AdF35 showed cytopathic effects and increased sub-G1 fractions. Caspase-9, less significantly caspase-8 and poly (ADP-ribose) polymerase, but not caspase-3 was cleaved and expression of molecules involved in autophagy and caspase-independent cell death pathways remained unchanged. Nevertheless, H2A histone family member X molecules were phosphorylated, and N-acetyl-L-cystein, an inhibitor for reactive oxygen species, suppressed the AdF35-mediated cytotoxicity. These data indicated a novel mechanism of Ad-mediated cell death and suggest a possible clinical application of the fiber-knob modified Ad.

Adenovirus-mediated FIR demonstrated TP53-independent cell-killing effect and enhanced antitumor activity of carbon-ion beams

Combination therapy of carbon-ion beam with the far upstream element-binding protein (FBP)-interacting repressor, FIR, which interferes with DNA damage repair proteins, was proposed as an approach for esophageal cancer treatment with low side effects regardless of TP53 status. In vivo therapeutic antitumor efficacy of replication-defective adenovirus (E1 and E3 deleted adenovirus serotype 5) encoding human FIR cDNA (Ad-FIR) was demonstrated in the tumor xenograft model of human esophageal squamous cancer cells, TE-2. Bleomycin (BLM) is an anticancer agent that introduces DNA breaks. The authors reported that Ad-FIR involved in the BLM-induced DNA damage repair response and thus applicable for other DNA damaging agents. To examine the effect of Ad-FIR on DNA damage repair, BLM, X-ray and carbon-ion irradiation were used as DNA damaging agents. The biological effects of high linear energy transfer (LET) radiotherapy used with carbon-ion irradiation are more expansive than low-LET conventional radiotherapy, such as X-rays or γ rays. High LET radiotherapy is suitable for the local control of tumors because of its high relative biological effectiveness. Ad-FIR enhanced BLM-induced DNA damage indicated by γH2AX in vitro. BLM treatment increased endogenous nuclear FIR expression in TE-2 cells, and P27Kip1 expression was suppressed by TP53 siRNA and BLM treatment. Further, Ad-FIRΔexon2, a dominant-negative form of FIR that lacks exon2 transcriptional repression domain, decreased Ku86 expression. The combination of Ad-FIR and BLM in TP53 siRNA increased DNA damage. Additionally, Ad-FIR showed synergistic cell toxicity with X-ray in vitro and significantly increased the antitumor efficacy of carbon-ion irradiation in the xenograft mouse model of TE-2 cells (P=0.03, Mann-Whitney's U-test) and was synergistic with the sensitization enhancement ratio (SER) value of 1.15. Therefore, Ad-FIR increased the cell-killing activity of the carbon-ion beam that avoids late-phase severe adverse effects independently of the TP53 status in vitro. Our findings indicated the feasibility of the combination of Ad-FIR with DNA damaging agents for future esophageal cancer treatment.

Experimental studies on the inhibition of adenovirus-ING4-OSM therapy on nasopharyngeal carcinoma proliferation in vitro and in vivo

In the present study, the effects of the co-transfer of the tumor growth inhibitor 4 gene (ING4) together with the Oncostatin M (OSM) were investigated on tumor regression and subsequent tumor recurrence. We constructed a recombinant adenovirus carrying ING4 and OSM, which could induce high-level expression of these three genes in NPC CNE-1 cells. Ad-ING4, Ad-OSM and Ad-ING4-OSM infection all inhibited the growth of CNE-1 cells in vitro, while the Ad-ING4-OSM exerted the strongest inhibitory effect. In CNE-1 xenograft tumor models mice, an intratumoral injection of Ad-ING4, Ad-OSM and Ad-ING4-OSM resulted in a reduced tumor burden, compared to normal saline controls. Therefore, we suggested that the introduction of adenovirus-mediated ING4 and OSM genes could synergistically decrease the recurrence or metastases and develop a control of NPC tumors, which advocate a promising therapeutic future in NPC treatment.

Cytotoxic effects of replication-competent adenoviruses on human esophageal carcinoma are enhanced by forced p53 expression

Background

Improvement of transduction and augmentation of cytotoxicity are crucial for adenoviruses (Ad)-mediated gene therapy for cancer. Down-regulated expression of type 5 Ad (Ad5) receptors on human tumors hampered Ad-mediated transduction. Furthermore, a role of the p53 pathways in cytotoxicity mediated by replication-competent Ad remained uncharacterized.

Methods

We constructed replication-competent Ad5 of which the E1 region genes were activated by a transcriptional regulatory region of the midkine or the survivin gene, which is expressed preferentially in human tumors. We also prepared replication-competent Ad5 which were regulated by the same region but had a fiber-knob region derived from serotype 35 (AdF35). We examined the cytotoxicity of these Ad and a possible combinatory use of the replication-competent AdF35 and Ad5 expressing the wild-type p53 gene (Ad5/p53) in esophageal carcinoma cells. Expression levels of molecules involved in cell death, anti-tumor effects in vivo and production of viral progenies were also investigated.

Results

Replication-competent AdF35 in general achieved greater cytotoxic effects to esophageal carcinoma cells than the corresponding replication-competent Ad5. Infection with the AdF35 induced cleavages of caspases and increased sub-G1 fractions, but did not activate the autophagy pathway. Transduction with Ad5/p53 in combination with the replication-competent AdF35 further enhanced the cytotoxicity in a synergistic manner. We also demonstrated the combinatory effects in an animal model. Transduction with Ad5/p53 however suppressed production of replication-competent AdF35 progenies, but the combination augmented Ad5/p53-mediated p53 expression levels and the downstream pathways.

Conclusions

Combination of replication-competent AdF35 and Ad5/p53 achieved synergistic cytotoxicity due to enhanced p53-mediated apoptotic pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1482-8) contains supplementary material, which is available to authorized users.

Adenoviral-based immunotherapy provides local disease control in an orthotopic murine model of esophageal cancer

Despite recent advances in the development of novel therapies, esophageal carcinoma remains an aggressive cancer associated with a poor prognosis. The lack of a high throughput, reproducible syngeneic animal model that replicates human disease is partly responsible for the paucity of novel therapeutic approaches. In this report, we present the first successful syngeneic, orthotopic model for esophageal cancer. This model was used to test an established adenoviral-based tumor vaccine. We utilized a murine esophageal cancer cell line established from the ED-L2-cyclin D1;p53 mouse that was transduced to express a viral tumor antigen, the Human Papilloma Virus (HPV) E7 protein. The tumor was established in its natural microenvironment at the gastroesophageal junction. Tumor growth was consistent and reproducible. An adenoviral vaccine to E7 (Ad.E7) induced an E7-specific population of functionally active CD8 T cells that trafficked into the tumors and retained cytotoxicity. Ad.E7 vaccination reduced local tumor growth and prolonged overall survival. These findings suggest that orthotopic tumor growth is a reasonable preclinical model to validate novel therapies.

Trans-splicing repair of mutant p53 suppresses the growth of hepatocellular carcinoma cells in vitro and in vivo

Reactivation of wild-type p53 (wt-p53) function is an attractive therapeutic approach to p53-defective cancers. An ideal p53-based gene therapy should restore wt-p53 production and reduces mutant p53 transcripts simultaneously. In this study, we described an alternative strategy named as trans-splicing that repaired mutant p53 transcripts in hepatocellular carcinoma (HCC) cells. The plasmids which encoded a pre-trans-splicing molecule (PTM) targeting intron 6 of p53 were constructed and then transfected into HCC cells carrying p53 mutation. Phenotypic changes of HCC cells induced by p53-PTM were analyzed through cell cycle, cell apoptosis and the expression of p53 downstream target genes. Spliceosome mediated RNA trans-splicing (SMaRT) reduced mutant p53 transcripts and produced functional wt-p53 protein after the delivery of p53-PTM plasmids, which resulted in phenotype correction of HCC cells. In tumor xenografts established by p53-mutated HCC cells, adenovirus encoding p53-PTM induced cell cycle arrest and apoptosis and then blocked the growth of tumors in mice. Collectively, our results demonstrated for the first time that mutant p53 transcripts were functionally corrected in p53-defective HCC cells and xenografts using trans-splicing, which indicated the feasibility of using trans-splicing to repair p53 mutation in p53-defective cancers.

Downregulation of p53 promotes in vitro perineural invasive activity of human salivary adenoid cystic carcinoma cells through epithelial-mesenchymal transition-like changes

Salivary adenoid cystic carcinoma (SACC) is a malignant tumor that is characterized by perineural invasion (PNI). p53 is an essential tumor-suppressor gene and p53 mutations play a critical role in tumor occurrence and progression (e.g., pancreatic, prostate and head and neck cancer). However, the regulatory role of the p53 gene in SACC and the PNI process remains unknown. In the present study, we employed RNA interference technique to downregulate p53 gene expression in SACC-83 cells to explore the role of p53 in the PNI process. Our results showed that the downregulation of the p53 gene induced significant 'epithelial-mesenchymal transition (EMT)-like changes' in SACC-83 cells, including decreased expression levels of epithelial markers (E-cadherin, EMA and CK5) and increased expression levels of mesenchymal markers (vimentin, N-cadherin and C-cadherin). The downregulation of p53 also caused a lower apoptotic index of Annexin V-FITC/PI and a lower number of SACC-83 cells in the second G0/G1 phase of the cell cycle. Furthermore, the downregulation of the p53 gene resulted in a significant increase in PNI activity in the SACC-83 cells. Thus, our findings revealed that downregulation of p53 promoted in vitro PNI activity through 'EMT-like changes' in SACC-83 cells. The present study suggests the essential regulatory role of p53 in the PNI activity of SACC cells, and implies that p53 may be a new target gene for the clinical treatment of SACC.

Clinical utility of recombinant adenoviral human p53 gene therapy: current perspectives

Gene therapy has promised to be a highly effective antitumor treatment by introducing a tumor suppressor gene or the abrogation of an oncogene. Among the potential therapeutic transgenes, the tumor suppressor gene p53 serves as an attractive target. Restoration of wild-type p53 function in tumors can be achieved by introduction of an intact complementary deoxyribonucleic acid copy of the p53 gene using a suitable viral vector, in most cases an adenoviral vector (Adp53). Preclinical in vitro and in vivo studies have shown that Adp53 triggers a dramatic tumor regression response in various cancers. These viruses are engineered to lack certain early proteins and are thus replication defective, including Gendicine, SCH-58500, and Advexin. Several types of tumor-specific p53-expressing conditionally replicating adenovirus vectors (known as replication-competent CRAdp53 vectors) have been developed, such as ONYX 015, AdDelta24-p53, SG600-p53, OBP-702, and H101. Various clinical trials have been conducted to investigate the safety and efficiency of these adenoviral vectors. In this review we will talk about the biological mechanisms, clinical utility, and therapeutic potentials of the replication-deficient Adp53-based and replication-competent CRAdp53-based gene therapy.

Advances in adenovirus-mediated p53 cancer gene therapy

INTRODUCTION

The tumor suppressor p53 gene regulates diverse cellular processes, such as cell-cycle arrest, senescence, apoptosis and autophagy, and it is frequently inactivated by genetic alterations in ∼ 50% of all types of human cancers. To restore wild-type p53 function in p53-inactivated tumors, adenovirus-mediated p53 gene therapy has been developed as a promising antitumor strategy in preclinical experiments and clinical studies.

AREAS COVERED

This review focuses on the clinical relevance of replication-deficient adenovirus vectors that carry the wild-type p53 gene (Ad-p53; Advexin, Gendicine and SCH-58500) in clinical studies of patients with various cancers and the future perspectives regarding conditionally replicating adenovirus vectors expressing the wild-type p53 gene (CRAd-p53; AdDelta24-p53, SG600-p53, OBP-702) in preclinical experiments. Moreover, the recent advances in our understanding of the molecular basis for the p53-mediated tumor suppression network induced by Ad-p53 and CRAd-p53 vectors and the combination therapies for promoting the therapeutic potential of adenovirus-mediated p53 gene therapy are discussed.

EXPERT OPINION

Exploration of the molecular mechanism underlying the p53-mediated tumor suppression network and the effective strategy for enhancing the p53-mediated cell death signaling pathway would provide novel insights into the improvement of clinical outcome in p53-based cancer gene therapy.

Combination of adenoviruses expressing melanoma differentiation-associated gene-7 and chemotherapeutic agents produces enhanced cytotoxicity on esophageal carcinoma

We examined the combinatory antitumor effects of adenoviruses expressing human mda-7/IL-24 gene (Ad-mda-7) and chemotherapeutic agents on nine kinds of human esophageal carcinoma cells. All the carcinoma cells expressed the melanoma differentiation-associated gene-7/interleukin-24 (MDA-7/IL-24) receptor complexes, IL-20R2 and either IL-20R1 or IL-22R1, and were susceptible to Ad-mda-7, whereas fibroblasts were positive only for IL-20R2 gene and resistant to Ad-mda-7-mediated cytotoxicity. Sensitivity of these esophageal carcinoma cells to Ad-mda-7 was however lower than that to Ad expressing the wild-type p53 gene. We thereby investigated a possible combination of Ad-mda-7 and anticancer agents and found that Ad-mda-7 with 5-fluorouracil (5-FU), cisplatin, mitomycin C or etoposide produced greater cytotoxic effects than those by Ad-mda-7 or the agent alone. Half-maximal inhibitory concentration values of the agents in respective cells were decreased by the combination with Ad-mda-7. Cell cycle analyses showed that Ad-mda-7 and 5-FU increased G2/M-phase and S-phase populations, respectively, and the combination augmented sub-G1 populations. Ad-mda-7-treated cells showed cleavages of caspase-8, -9 and -3 and poly (ADP-ribose) polymerase, but the cleavage levels were not different from those of the combination-treated cells. Ad-mda-7 treatments upregulated Akt phosphorylation but suppressed IκB-α levels, whereas 5-FU treatments induced phosphorylation of p53 and extracellular signal-regulated protein kinases 1 and 2. Molecular changes caused by the combination were similar to those by Ad-mda-7 treatments, but the Ad-mda-7-mediated upregulation of Akt phosphorylation decreased with the combination. These data collectively suggest that Ad-mda-7 induced apoptosis despite Akt activation and that the combinatory antitumor effects with 5-FU were produced partly by downregulating the Ad-mda-7-induced Akt activation.

Clinical antiangiogenic effect of recombinant adenovirus-p53 combined with hyperthermia for advanced cancer

OBJECTIVE

To assess the safety and clinical antiangiogenic effect of recombinant adenovirus-p53 (rAd-p53) combined with hyperthermia plus or not plus radiotherapy in advanced cancer.

METHODS

Expression of Vascular epithelial growth factor (VEGF) after intratumoral injection of rAd-p53 was assayed by immunohistochemistry (IHC) imaging. Forty-four patients with advanced cancer were enrolled into this clinical study. The patients were intratumorally injected with rAd-p53 (Gendicine) at a dose of 1×10(12) vp once a week, with a total of 4-54 (mean 7.7) times. Total of 4-29 (mean 8.5) times of hyperthermia was given to the patients. Among the 44 patients, 30 patients were concurrently added with radiotherapy of a total dose 30-76 Gy/15-38 f/3-8 w (mean 58 Gy).

RESULTS

Before and after intratumoral injection of rAd-p53, the VEGF IHC positive cell scores were 2.80 and 1.50, respectively (P=0.031). The treatment of rAd-p53 combined with hyperthermia plus or not plus radiotherapy in advanced cancer achieved CR rate of 13.60% (6/44), and PR rate of 29.6% (13/44), and thus the effective rate was 43.2%. In addition to 6 patients with CR, 19 patients (19/38, 50.0%) had low density area (LDA) of more than 50% area on CT image within tumor indicating tumor tissue necrosis.

CONCLUSIONS

Our data indicate that rAd-p53 inhibits VEGF expression and angiogenesis, and promotes tumor necrosis and shrinkage induced by hyperthermia plus or not plus radiotherapy in advanced cancer.

Recombinant adenovirus-p53 (Gendicine) sensitizes a pancreatic carcinoma cell line to radiation

OBJECTIVE

In this study, we examine the effects of recombinant adenovirus-p53 (rAd-p53) on the pancreatic carcinoma cell line SW1990. Specifically, we determine if expression of rAd-p53 sensitizes these cells to radiation.

METHODS

Following transfection of SW1990 cells with rAd-p53, we measured expression of P53, P21 and Bax by immunocytochemistry. Both transfected and control cell lines were irradiated with a range of doses, and the survival fractions (SF) were calculated. Dose survival curves were constructed and modeled for comparison.

RESULTS

Transfection of SW1990 cells with rAd-p53 resulted in increased expression of P53, P21 and Bax in a time-dependent manner. At 96 h after transfection, 89.92% of cells expressed P53, 56.8% expressed P21, and 76.50% expressed Bax. The SF following radiation was lower in the rAd-p53 transfected cells compared to the control cells, suggesting that rAd-p53 sensitizes SW1990 cells to radiation (D0 for the experimental and control groups was 2.199 and 2.462, respectively).

CONCLUSIONS

Use of the adenoviral vector is an effective means of transfecting SW1990 cells with wild-type P53, and this sensitizes the cell line to irradiation. This work suggests that combining rAd-p53 with radiation therapy in pancreatic cancer may be therapeutically beneficial.

Nano delivers big: designing molecular missiles for cancer therapeutics

Current first-line treatments for most cancers feature a short-list of highly potent and often target-blind interventions, including chemotherapy, radiation, and surgical excision. These treatments wreak considerable havoc upon non-cancerous tissue and organs, resulting in deleterious and sometimes fatal side effects for the patient. In response, this past decade has witnessed the robust emergence of nanoparticles and, more relevantly, nanoparticle drug delivery systems (DDS), widely touted as the panacea of cancer therapeutics. While not a cure, nanoparticle DDS can successfully negotiate the clinical payoff between drug dosage and side effects by encompassing target-specific drug delivery strategies. The expanding library of nanoparticles includes lipoproteins, liposomes, dendrimers, polymers, metal and metal oxide nano-spheres and -rods, and carbon nanotubes, so do the modes of delivery. Importantly, however, the pharmaco-dynamics and –kinetics of these nano-complexes remain an urgent issue and a serious bottleneck in the transition from bench to bedside. This review addresses the rise of nanoparticle DDS platforms for cancer and explores concepts of gene/drug delivery and cytotoxicity in pre-clinical and clinical contexts.

Dual programmed cell death pathways induced by p53 transactivation overcome resistance to oncolytic adenovirus in human osteosarcoma cells

Tumor suppressor p53 is a multifunctional transcription factor that regulates diverse cell fates, including apoptosis and autophagy in tumor biology. p53 overexpression enhances the antitumor activity of oncolytic adenoviruses; however, the molecular mechanism of this occurrence remains unclear. We previously developed a tumor-specific replication-competent oncolytic adenovirus, OBP-301, that kills human osteosarcoma cells, but some human osteosarcoma cells were OBP-301-resistant. In this study, we investigated the antitumor activity of a p53-expressing oncolytic adenovirus, OBP-702, and the molecular mechanism of the p53-mediated cell death pathway in OBP-301-resistant human osteosarcoma cells. The cytopathic activity of OBP-702 was examined in OBP-301-sensitive (U2OS and HOS) and OBP-301-resistant (SaOS-2 and MNNG/HOS) human osteosarcoma cells. The molecular mechanism in the OBP-702-mediated induction of two cell death pathways, apoptosis and autophagy, was investigated in OBP-301-resistant osteosarcoma cells. The antitumor effect of OBP-702 was further assessed using an orthotopic OBP-301-resistant MNNG/HOS osteosarcoma xenograft tumor model. OBP-702 suppressed the viability of OBP-301-sensitive and -resistant osteosarcoma cells more efficiently than OBP-301 or a replication-deficient p53-expressing adenovirus (Ad-p53). OBP-702 induced more profound apoptosis and autophagy when compared with OBP-301 or Ad-p53. E1A-mediated miR-93/106b upregulation induced p21 suppression, leading to p53-mediated apoptosis and autophagy in OBP-702-infected cells. p53 overexpression enhanced adenovirus-mediated autophagy through activation of damage-regulated autophagy modulator (DRAM). Moreover, OBP-702 suppressed tumor growth in an orthotopic OBP-301-resistant MNNG/HOS xenograft tumor model. These results suggest that OBP-702-mediated p53 transactivation is a promising antitumor strategy to induce dual apoptotic and autophagic cell death pathways via regulation of miRNA and DRAM in human osteosarcoma cells.

Visualization and targeted disruption of protein interactions in living cells

Protein-protein interactions are the basis of all processes in living cells, but most studies of these interactions rely on biochemical in vitro assays. Here we present a simple and versatile fluorescent-three-hybrid (F3H) strategy to visualize and target protein-protein interactions. A high-affinity nanobody anchors a GFP-fusion protein of interest at a defined cellular structure and the enrichment of red-labelled interacting proteins is measured at these sites. With this approach, we visualize the p53-HDM2 interaction in living cells and directly monitor the disruption of this interaction by Nutlin 3, a drug developed to boost p53 activity in cancer therapy. We further use this approach to develop a cell-permeable vector that releases a highly specific peptide disrupting the p53 and HDM2 interaction. The availability of multiple anchor sites and the simple optical readout of this nanobody-based capture assay enable systematic and versatile analyses of protein-protein interactions in practically any cell type and species.

Synergistic anticancer effect of rAd/P53 combined with 5-fluorouracil or iodized oil in the early therapeutic response of human colon cancer in vivo

Exogenous wild-type p53 (wt-p53) tumor suppression increases the sensitivity of tumor cells to radiotherapy and chemotherapy. An iodized oil emulsion was used as a p53 vector for intra-arterial gene delivery to treat hepatic tumors. Whether the chemotherapeutic agent or the iodized oil affects exogenous wt-p53 activity remains poorly understood. In the present study, the early therapeutic response of rAd/p53, combined with 5-fluorouracil (5-FU) or with iodized oil, was observed in a human colon cancer model. Allograft models in 82 nude mice with human colon carcinoma SW480 were divided randomly into four groups and administered with physiologic saline, rAd/p53, rAd/p53+5-FU, and rAd/p53+iodized oil by intratumoral injection. At 24, 48, 72, 120, and 168 h after treatment, p53 expression, the Ki-67 index (KI), and the degree of tumor necrosis were assessed. The p53 expression and tumor necrosis in the therapeutic groups were higher than those in the control group. p53 expression reached its peak at 120 h in the rAd/p53 group, at 72 h in the rAd/p53+5-FU group, and at 48 h in the rAd/p53+iodized oil group. The p53 expression in the rAd/P53+5-FU group and the iodized oil group was significantly higher than those in the rAd/P53 group at 24 and 48 h. The results revealed that tumor necrosis is positively correlated with p53 expression. The KI of the rAd/p53+5-FU group increased significantly at 24 h. 5-FU and iodized oil increase the anticancer effect of rAd/p53, and 5-FU combined with rAd/p53 has a synergistic anticancer effect.

A novel apoptotic mechanism of genetically engineered adenovirus-mediated tumour-specific p53 overexpression through E1A-dependent p21 and MDM2 suppression

Oncolytic viruses engineered to replicate in tumour cells but not in normal cells could be used as tumour-specific vectors carrying the therapeutic genes. We previously developed a telomerase-specific oncolytic adenovirus, OBP-301, that causes cell death in human cancer cells with telomerase activities. Here, we further modified OBP-301 to express the wild-type p53 tumour suppressor gene (OBP-702), and investigated whether OBP-702 induces stronger antitumour activity than OBP-301. The antitumour effect of OBP-702 was compared to that of OBP-301 on OBP-301-sensitive (H358 and H460) and OBP-301-resistant (T.Tn and HSC4) human cancer cells. OBP-702 suppressed the viability of both OBP-301-sensitive and OBP-301-resistant cancer cells more efficiently than OBP-301. OBP-702 caused increased apoptosis compared to OBP-301 or a replication-deficient adenovirus expressing the p53 gene (Ad-p53) in H358 and T.Tn cells. Adenovirus E1A-mediated p21 and MDM2 downregulation was involved in the apoptosis caused by OBP-702. Moreover, OBP-702 significantly suppressed tumour growth in subcutaneous tumour xenograft models compared to monotherapy with OBP-301 or Ad-p53. Our data demonstrated that OBP-702 infection expressed adenovirus E1A and then inhibited p21 and MDM2 expression, which in turn efficiently induced apoptotic cell death. This novel apoptotic mechanism suggests that the p53-expressing OBP-702 is a promising antitumour reagent for human cancer and could improve the clinical outcome.

A simple detection system for adenovirus receptor expression using a telomerase-specific replication-competent adenovirus

Adenovirus serotype 5 (Ad5) is frequently used as an effective vector for induction of therapeutic transgenes in cancer gene therapy or of tumor cell lysis in oncolytic virotherapy. Ad5 can infect target cells through binding with the coxsackie and adenovirus receptor (CAR). Thus, the infectious ability of Ad5-based vectors depends on the CAR expression level in target cells. There are conventional methods to evaluate the CAR expression level in human target cells, including flow cytometry, western blotting and immunohistochemistry. Here, we show a simple system for detection and assessment of functional CAR expression in human tumor cells, using the green fluorescent protein (GFP)-expressing telomerase-specific replication-competent adenovirus OBP-401. OBP-401 infection induced detectable GFP expression in CAR-expressing tumor cells, but not in CAR-negative tumor cells, nor in CAR-positive normal fibroblasts, 24 h after infection. OBP-401-mediated GFP expression was significantly associated with CAR expression in tumor cells. OBP-401 infection detected tumor cells with low CAR expression more efficiently than conventional methods. OBP-401 also distinguished CAR-positive tumor tissues from CAR-negative tumor and normal tissues in biopsy samples. These results suggest that GFP-expressing telomerase-specific replication-competent adenovirus is a very potent diagnostic tool for assessment of functional CAR expression in tumor cells for Ad5-based antitumor therapy.

Antitumor activity of a combination of rAd2p53 adenoviral gene therapy and radiotherapy in esophageal carcinoma

The objective of this study was to determine if a combination of recombinant adenovirus 2 p53 (rAd2p53) gene therapy and radiotherapy would have significantly improved outcome from esophageal carcinoma when compared to radiotherapy (RT) alone. Forty-five patients diagnosed with esophageal carcinoma (confirmed squamous cell carcinoma) were randomly assigned to one of two study arms: treatment group: rAd2p53 gene therapy + RT (n = 22); and control group: radiotherapy (n = 23). For the treatment group, rAd2p53 was injected into multiple areas of the lesion once a week for 6 weeks avoiding deep ulcers points. RT was administered after 3 days of injection of rAd2p53. Patients in the control group only received radiotherapy. The overall response rate was significantly higher in the treatment group than in control group (P < 0.05). Furthermore, the complete response rate was 3 times higher in the treatment group than in the control group (P < 0.05). Transient fever and pain at injection site were the only side effects mentioned in the treatment group. In conclusion, this recombinant virus-RT combination is significantly more beneficial in palliation than RT alone, with minor side affects. However, its role as neoadjuvant therapy prior to surgical resection needs to be further investigated.

Recent advances in p53 research and cancer treatment

TP53, encoding p53, is one of the most famous tumor suppressor genes. The majority of human cancers demonstrate the inactivation of the p53 pathway. Mutant p53 not only, no longer, functions as a tumor suppressor but can also exert tumor-promoting effects. The basic function of p53 is to respond to cellular stress. We herein review the recent advances in p53 research and focus on apoptosis, cell cycle arrest, and senescence in response to stress. We also review the clinical applications of p53-based therapy for human cancer.

Multiple treatment cycles of liposome-encapsulated adenoviral RIP-TK gene therapy effectively ablate human pancreatic cancer cells in SCID mice

BACKGROUND

Adenoviral gene therapy has been applied widely for cancer therapy; however, transient gene expression as result of humoral immunoneutralization response to adenovirus limits its effect. The purpose of this study is to determine whether DOTAP:cholesterol liposome could shield adenovirus from neutralizing antibody and permit the use of multiple cycles of intravenous liposome encapsulated serotype 5 adenoviral rat insulin promoter directed thymidine kinase (L-A-5-RIP-TK) with ganciclovir (GCV) to enhance its effect.

METHODS

The effect of multiple cycles of systemic L-A-5-RIP-TK/GCV therapy was evaluated in grouped PANC-1 SCID mice treated with different numbers of cycles. Humoral immune response to A-5-RIP-TK or L-A-5-RIP-TK was assessed using C57/B6J mice challenged with adenovirus or liposome adenovirus complex.

RESULTS

The minimal residual tumor burden (3.2 ± 0.6 mm(3)) and greatest survival time (153.0 ± 6 days) were obtained in the mice receiving 4 and 3 cycles of therapy, respectively. Toxicity to islet cells associated with RIP-TK/GCV therapy was observed after 4 cycles. DOTAP:chol-encapsulated adenovectors were able to protect adenovectors from the neutralization of high titer of anti-adenoviral antibodies induced by itself.

CONCLUSION

Multiple treatment cycles of L-A-5-RIP-TK/GCV ablate human PANC-1 cells effectively in SCID mice; however, the mice become diabetic and have substantial mortality after the 4th cycle. Liposome-encapsulated adenovirus is functionally resistant to the neutralizing effects of anti-adenoviral antibodies, suggesting feasibility of multiple cycles of therapy. Liposome encapsulation of the adenovirus may be a promising strategy for repeated delivery of systemic adenoviral gene therapy.

The emerging role of viruses in the treatment of solid tumours

There is increasing optimism for the use of non-pathogenic viruses in the treatment of many cancers. Initial interest in oncolytic virotherapy was based on the observation of an occasional clinical resolution of a lymphoma after a systemic viral infection. In many cancers, by comparison with normal tissues, the competency of the cellular anti-viral mechanism is impaired, thus creating an exploitable difference between the tumour and normal cells, as an unimpeded viral proliferation in cancer cells is eventually cytocidal. In addition to their oncolytic capability, these particular viruses may be engineered to facilitate gene delivery to tumour cells to produce therapeutic effects such as cytokine secretion and anti -tumour immune responses prior to the eventual cytolysis. There is now promising clinical experience with these viral strategies, particularly as part of multimodal studies, and already several clinical trials are in progress. The limitations of standard cancer chemotherapies, including their lack of specificity with consequent collateral toxicity and the development of cross-resistance, do not appear to apply to viral-based therapies. Furthermore, virotherapy frequently restores chemoradiosensitivity to resistant tumours and has also demonstrated efficacy against cancers that historically have a dismal prognosis. While there is cause for optimism, through continued improvements in the efficiency and safety of systemic delivery, through the emergence of alternative viral agents and through favourable clinical experiences, clinical trials as part of multimodal protocols will be necessary to define clinical utility. Significant progress has been made and this is now a major research area with an increasing annual bibliography.

Carrier cell-mediated cell lysis of squamous cell carcinoma cells by squamous cell carcinoma antigen 1 promoter-driven oncolytic adenovirus

BACKGROUND

The squamous cell carcinoma antigen (SCCA) serves as a serological marker for squamous cell carcinomas. Molecular cloning of the SCCA genomic region has revealed the presence of two tandemly arrayed genes: SCCA1 and SCCA2. SCCA1 gene is up-regulated in squamous cell carcinoma cells. We analyzed the proximal region of the SCCA1 promoter and the antitumor effect of oncolytic adenovirus driven by the SCCA1 promoter in squamous cell carcinoma cells.

METHODS

The SCCA1 promoter was analyzed by dual luciferase assay and substituted with the E1A promoter to construct the oncolytic adenovirus to determine the squamous cell carcinoma-specific cell lysis.

RESULTS

Deletion analysis of SCCA1 promoter identified a 175-bp core promoter region and an enhancer region at -525 to -475 bp upstream of the transcription start site. The transcriptional activity of the SCCA1 promoter was up-regulated in squamous cell carcinoma cells. Five tandem repeats of enhancer increased SCCA1 promoter activity by four-fold. Oncolytic adenovirus driven by this SCCA1 enhancer-promoter complex specifically killed squamous cell carcinoma cells in vitro and in vivo. A549 carrier cells infected with the oncolytic adenovirus induced complete regression of syngeneic squamous cell carcinoma cell tumor by overcoming immunogenicity and adenovirus-mGM-CSF augmented the antitumor effect of carrier cells.

CONCLUSIONS

SCCA1 was up-regulated in squamous cell carcinoma cells and oncolytic adenovirus driven by SCCA1 promoter specifically killed these cells. These findings suggest that SCCA1 promoter is a potential target of gene therapy for squamous cell carcinoma.

Small-animal PET/CT for monitoring the development and response to chemotherapy of thymic lymphoma in Trp53-/- mice

Transgenic mouse models of human cancers represent one of the most promising approaches to elucidate clinically relevant mechanisms of action and provide insights into the treatment efficacy of new antitumor drugs. The use of Trp53 transgenic mice (Trp53 knockout [Trp53(-/-)] mice) for these kinds of studies is, so far, restricted by limitations in detecting developing tumors and the lack of noninvasive tools for monitoring tumor growth, progression, and treatment response.

METHODS

We hypothesized that quantitative small-animal PET with (18)F-FDG was able to detect the onset and location of tumor development, follow tumor progression, and monitor response to chemotherapy. To test these hypotheses, C57BL/6J Trp53(-/-) mice underwent longitudinal small-animal PET during lymphoma development and gemcitabine treatment. Trp53 wild-type (Trp53(+/+)) mice were used as controls, and histology after full necropsy served as the gold standard.

RESULTS

In Trp53(+/+) mice, the thymic standardized uptake value (SUV) did not exceed 1.0 g/mL, with decreasing (18)F-FDG uptake over time. Conversely, all Trp53(-/-) mice that developed thymic lymphoma showed increasing thymic glucose metabolism, with a mean SUV doubling time of 9.0 wk (range, 6.0-17.5 wk). Using an SUV of 3.0 g/mL as a criterion provided a sensitivity of 78% and a specificity of 100% for the detection of thymic lymphoma. Treatment monitoring with (18)F-FDG PET correctly identified all histologic responses and relapses to gemcitabine.

CONCLUSION

(18)F-FDG small-animal PET can be used to visualize onset and progression of thymic lymphomas in Trp53(-/-) mice and monitor response to chemotherapy. Thus, (18)F-FDG small-animal PET provides an in vivo means to assess intervention studies in the Trp53 transgenic mouse model.

Adenovirus Ad-p53AIP1-mediated gene therapy and its regulation of p53-MDM2 interactions

We generated replication-defective adenovirus Ad-p53AIP1 and studied its anti-tumor efficacy both in vitro and in vivo. We demonstrated that Ad-p53AIP1 infection elicited high levels of p53AIP1 expression in cancer cells. We also found that Ad-p53AIP1 expression induced marked apoptosis and cell cycle arrest in HepG2 cells. Moreover, Ad-p53AIP1 infection significantly inhibited the tumorigenesis of 4T1 mouse mammary cancer cells in vivo. In particular, we discovered that p53AIP1 overexpression up-regulated the protein levels of p53 in HepG2 cells, which was accompanied by down-regulation of MDM2 mRNA and protein, suggesting an interaction between MDM2 and p53 in p53AIP1-induced apoptosis and cell cycle arrest. Our data demonstrated the feasibility of Ad-p53AIP1-mediated cancer gene therapy. p53AIP1-induced up-regulation of p53 protein through MDM2 suggests that p53AIP1 gene therapy may be more advantageous in tumors expressing high levels of oncoprotein MDM2 or having a mutation in MDM2 inhibitor p16INK4.

Viral shedding after p53 adenoviral gene therapy in 10 cases of esophageal cancer

We detected adenoviral DNA fragments in excretions of 10 esophageal cancer patients by DNA-PCR after tumor injection of Ad-CMV-vector. A total of 220 samples consisting of feces, gargling saliva, urine, and blood plasma were assessed. A total of 29.7% of feces samples and 13.2% of gargling saliva samples were positive for adenoviral DNA fragments, but 89.7% of the positive feces samples and all of the positive gargling saliva samples turned negative on day 12 after tumor injection. Although adenoviral DNA fragments may be pathogen-free, patients' feces and gargling saliva contain adenoviral DNA fragments for 12 days after injection.

Small-molecule inhibitors of MDM2 as new anticancer therapeutics

It has long been known that traditional anticancer radio- and chemotherapies in part work through direct or indirect activation of the p53 tumour suppressor pathway. However, many of these strategies are nonselective and genotoxic. The emerging understanding of the pathways that regulate p53 has led to the notion that it should be possible to activate the p53 pathway in ways that are inherently nongenotoxic. Important targets for pharmacological interference in this respect are MDM2 and MDMX, key negative regulators of p53. Genetic and pharmacologic studies suggest that blocking the physical interaction of these proteins with p53, or inhibiting the catalytic role of MDM2 in tagging p53 for proteasomal degradation, both of which lead to an increase in the transcriptional activity of p53, may indeed be an efficient and safe way to eradicate tumour cells that retain wild-type p53. Here we review the rationale for such strategies, as well as the current state in the discovery and development of drugs that reactivate p53 by inhibiting its inhibitors MDM2 and MDMX. The first compounds that have been shown in model systems to be able selectively to kill cancer cells in this way are now entering clinical trials and the promise of MDM2 inhibitors as a new therapeutic anticancer modality should therefore become clear in the not-too-distant future.

Integration of targeted agents in the neo-adjuvant treatment of gastro-esophageal cancers

Pre- and peri-operative strategies are becoming standard for the management of localized gastro-esophageal cancer. For localized gastric/gastro-esophageal junction (GEJ) cancer there are conflicting data that a peri-operative approach with cisplatin-based chemotherapy improves survival, with the benefits seen in esophageal cancer likely less than a 5-10% incremental improvement. Further trends toward improvement in local control and survival, when combined chemotherapy and radiation therapy are given pre-operatively, are suggested by recent phase III trials. In fit patients, a significant survival benefit with pre-operative chemoradiation is seen in those patients who achieve a pathologic complete response. In esophageal/GEJ cancer, definitive chemoradiation is now considered in medically inoperable patients. In squamous cell carcinoma of the esophagus, surgery after primary chemoradiation is not clearly associated with an improved overall survival, however, local control may be better. In localized gastric/GEJ cancer, the integration of bevacizumab with pre-operative chemotherapy is being explored in large randomized studies, and with chemoradiotherapy in pilot trials. The addition of anti-epidermal growth factor receptor and anti-human epidermal growth factor receptor-2 antibody treatment to pre-operative chemoradiation continues to be explored. Early results show the integration of targeted therapy is feasible. Metabolic imaging can predict early response to pre-operative chemotherapy and biomarkers may further predict response to pre-operative chemo-targeted therapy. A multimodality approach to localized gastro-esophageal cancer has resulted in better outcomes. For T3 or node-positive disease, surgery alone is no longer considered appropriate and neo-adjuvant therapy is recommended. The future of neo-adjuvant strategies in this disease will involve the individualization of therapy with the integration of molecular signatures, targeted therapy, metabolic imaging and predictive biomarkers.

Multiple hepatic arterial injections of recombinant adenovirus p53 and 5-fluorouracil after transcatheter arterial chemoembolization for unresectable hepatocellular carcinoma: a pilot phase II trial

This pilot phase II study was designed to determine the efficacy, toxicities, and biological activity of multiple hepatic arterial injections of recombinant adenovirus p53 (rAd-p53) and 5-fluorouracil (5-FU) after transcatheter arterial chemoembolization (TACE) when compared with TACE alone in patients with unresectable hepatocellular carcinoma (HCC). Forty-six patients with unresectable HCC were randomized in either group 1 [23 patients, multiple hepatic arterial injections of Ad-p53 (1x10 viral particles) and 5-FU (500-750 mg), after TACE] or group 2 (23 patients, TACE alone). In group 1, the number of Ad-p53/5-FU courses administered was 166 (median 7, range 3-12). In group 2, the number of TACE courses administered was 47 (median 2, range 1-3). Partial response and stable disease were 69.5% in group 1 and 65.2% in group 2. Times to progression were 9.6 months (range 2.1-21.7) in group 1 and 8.3 months (range 2.1-16.8) in group 2. Overall survivals were 12.8 months (range 2.7-26.2) in group 1 and 10.4 months (range 2.7-22.5) in group 2. Toxicities in both groups were generally mild and reversible. The most common Ad-p53-related toxicity was a transient fever. Specific p53 transgene expression was detected using reverse-transcriptase polymerase chain reaction in biopsied tumor tissues. Distribution studies revealed that the vector was detected in the plasma, but rarely in the gargle and urine. This study shows that multiple hepatic arterial injections of Ad-p53 and 5-FU after TACE can be active and safe as a treatment for patients with unresectable HCC.

Implications of endoplasmic reticulum stress, the unfolded protein response and apoptosis for molecular cancer therapy. Part I: targeting p53, Mdm2, GADD153/CHOP, GRP78/BiP and heat shock proteins

BACKGROUND

In eukaryotes, endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are coordinately regulated to maintain steady-state levels and activities of various cellular proteins to ensure cell survival.

OBJECTIVE

This review (Part I of II) focuses on specific ERS and UPR signalling regulators, their expression in the cancer phenotype and apoptosis, and proposes how their implication in these processes can be rationalised into proteasome inhibition, apoptosis induction and the development of more efficacious targeted molecular cancer therapies.

METHOD

In this review, we contextualise many ERS and UPR client proteins that are deregulated or mutated in cancers and show links between ERS and the UPR, their implication in oncogenic transformation, tumour progression and escape from immune surveillance, apoptosis inhibition, angiogenesis, metastasis, acquired drug resistance and poor cancer prognosis.

CONCLUSION

Evasion of programmed cell death or apoptosis is a hallmark of cancer that enables tumour cells to proliferate uncontrollably. Successful eradication of cancer cells through targeting ERS- and UPR-associated proteins to induce apoptosis is currently being pursued as a central tenet of anticancer drug discovery.

Adenoviral vector-based strategies for cancer therapy

Definitive treatment of cancer has eluded scientists for decades. Current therapeutic modalities like surgery, chemotherapy, radiotherapy and receptor-targeted antibodies have varied degree of success and generally have moderate to severe side effects. Gene therapy is one of the novel and promising approaches for therapeutic intervention of cancer. Viral vectors in general and adenoviral (Ad) vectors in particular are efficient natural gene delivery systems and are one of the obvious choices for cancer gene therapy. Clinical and preclinical findings with a wide variety of approaches like tumor suppressor and suicide gene therapy, oncolysis, immunotherapy, anti-angiogenesis and RNA interference using Ad vectors have been quite promising, but there are still many hurdles to overcome. Shortcomings like increased immunogenicity, prevalence of preexisting anti-Ad immunity in human population and lack of specific targeting limit the clinical usefulness of Ad vectors. In recent years, extensive research efforts have been made to overcome these limitations through a variety of approaches including the use of conditionally-replicating Ad and specific targeting of tumor cells. In this review, we discuss the potential strengths and limitations of Ad vectors for cancer therapy.

Cytotoxicity of adenoviruses expressing the wild-type p53 gene to esophageal carcinoma cells is linked with the CAR expression level and indirectly with the endogenous p53 status

We examined cytotoxic effects of adenoviruses (Ad) expressing the p53 gene (Ad-p53) in nine human esophageal carcinoma cell lines with respect to the Ad receptor expression and the endogenous p53 gene status. Ad-p53-mediated cytotoxicity was related with an expression level of the coxsackievirus adenovirus receptor (CAR) but not with that of CD51, both of which are type 5 Ad receptors. Contrary to earlier studies, we found that the cytotoxicity was greater in tumor cells with the wild-type p53 gene than in those with mutated p53. The cytotoxic activity of Ad defective of E1B55kDa molecules (Ad-delE1B55), however, was not linked with the CAR expression level or the endogenous p53 status. We noticed that the tumor cells with the wild-type p53 gene showed greater CAR expression levels, although transduction with Ad-p53 did not upregulate the CAR expression in the mutated cells. We also examined the Ad-53-mediated cytotoxicity in two kinds of paired fibroblasts, parent and immortalized with loss of the p53 functions, and showed that the CAR expression level was more influential than the endogenous p53 status in the cytotoxicity. These data suggest that CAR expression level is a better predictive marker than endogenous p53 status for Ad-p53-mediated cytotoxicity in esophageal carcinoma.