An oncogenomics-based in vivo RNAi screen identifies tumor suppressors in liver cancer.

Cancers are highly heterogeneous and contain many passenger and driver mutations. To functionally identify tumor suppressor genes relevant to human cancer, we compiled pools of short hairpin RNAs (shRNAs) targeting the mouse orthologs of genes recurrently deleted in a series of human hepatocellular carcinomas and tested their ability to promote tumorigenesis in a mosaic mouse model. In contrast to randomly selected shRNA pools, many deletion-specific pools accelerated hepatocarcinogenesis in mice. Through further analysis, we identified and validated 13 tumor suppressor genes, 12 of which had not been linked to cancer before. One gene, XPO4, encodes a nuclear export protein whose substrate, EIF5A2, is amplified in human tumors, is required for proliferation of XPO4-deficient tumor cells, and promotes hepatocellular carcinoma in mice. Our results establish the feasibility of in vivo RNAi screens and illustrate how combining cancer genomics, RNA interference, and mosaic mouse models can facilitate the functional annotation of the cancer genome.

Endoscopic Submucosal Dissection of a Giant Rectal Adenoma Manifesting as McKittrick-Wheelock Syndrome.

McKittrick-Wheelock syndrome (MKWS) is an uncommon clinical manifestation of large, villous, epithelial lesions of the distal colon and rectum. Excessive secretion of electrolyte-rich mucus from these lesions leads to secretory diarrhea, electrolyte disorders and acute renal failure. Several cases of MKWS have been reported since its initial description in 1954. The definitive treatment for the great majority of MKWS cases has consisted of surgical resection of the affected part of the colorectum, usually in the form of a low anterior resection or an abdominoperineal resection with the formation of an ostomy. Recent developments in endoscopic resection techniques now offer new, minimally invasive treatment alternatives for MKWS patients. We present the first reported case in the Western world of MKWS caused by a rectal adenoma with a size of 19 × 10 cm, treated through endoscopic submucosal dissection. Through the lessons learned by this case, as well as by a thorough review of the literature, we discuss this uncommon syndrome, focusing on treatment alternatives.

Administration of Gemcitabine After Pancreatic Tumor Resection in Mice Induces an Antitumor Immune Response Mediated by Natural Killer Cells.

BACKGROUND & AIMS: Even after potentially curative R0 resection, patients with pancreatic ductal adenocarcinoma (PDAC) have a poor prognosis owing to high rates of local recurrence and metastasis to distant organs. However, we have no suitable transgenic animal models for surgical interventions. METHODS: To induce formation of pancreatic tumor foci, we electroporated oncogenic plasmids into pancreata of LSL-KrasG12D × p53fl/fl mice; mutant Kras was expressed in p53fl/fl mice using a sleeping beauty transposon. We co-delivered a transposon encoding a constitutively active form of Akt2 (myrAkt2). Carcinogenesis and histopathologic features of tumors were examined. Metastasis was monitored by bioluminescence imaging. Tumors were resected and mice were given gemcitabine, and tumor recurrence patterns and survival were determined. Immune cells were collected from resection sites and analyzed by flow cytometry and in depletion experiments. RESULTS: After electroporation of oncogenic plasmids, mice developed a single pancreatic tumor nodule with histopathologic features of human PDAC. Pancreatic tumors that expressed myrAkt2 infiltrated the surrounding pancreatic tissue and neurons and became widely metastatic, reflecting the aggressive clinical features of PDAC in patients. Despite early tumor resection, mice died from locally recurring and distant tumors, but adjuvant administration of gemcitabine after tumor resection prolonged survival. In mice given adjuvant gemcitabine or vehicle, gemcitabine significantly inhibited local recurrence of tumors, but not metastasis to distant organs, similar to observations in clinical trials. Gemcitabine inhibited accumulation of CD11b+Gr1intF4/80int myeloid-derived suppressor cells at the resection margin and increased the number of natural killer (NK) cells at this location. NK cells but not T cells were required for gemcitabine-mediated antitumor responses. CONCLUSIONS: Gemcitabine administration after resection of pancreatic tumors in mice activates NK cell-mediated antitumor responses and inhibits local recurrence of tumors, consistent with observations from patients with PDAC. Transgenic mice with resectable pancreatic tumors might be promising tools to study adjuvant therapy strategies for patients.

Senescence surveillance of pre-malignant hepatocytes limits liver cancer development.

Upon the aberrant activation of oncogenes, normal cells can enter the cellular senescence program, a state of stable cell-cycle arrest, which represents an important barrier against tumour development in vivo. Senescent cells communicate with their environment by secreting various cytokines and growth factors, and it was reported that this 'secretory phenotype' can have pro- as well as anti-tumorigenic effects. Here we show that oncogene-induced senescence occurs in otherwise normal murine hepatocytes in vivo. Pre-malignant senescent hepatocytes secrete chemo- and cytokines and are subject to immune-mediated clearance (designated as 'senescence surveillance'), which depends on an intact CD4(+) T-cell-mediated adaptive immune response. Impaired immune surveillance of pre-malignant senescent hepatocytes results in the development of murine hepatocellular carcinomas (HCCs), thus showing that senescence surveillance is important for tumour suppression in vivo. In accordance with these observations, ras-specific Th1 lymphocytes could be detected in mice, in which oncogene-induced senescence had been triggered by hepatic expression of Nras(G12V). We also found that CD4(+) T cells require monocytes/macrophages to execute the clearance of senescent hepatocytes. Our study indicates that senescence surveillance represents an important extrinsic component of the senescence anti-tumour barrier, and illustrates how the cellular senescence program is involved in tumour immune surveillance by mounting specific immune responses against antigens expressed in pre-malignant senescent cells.

Viral Infection of Tumors Overcomes Resistance to PD-1-immunotherapy by Broadening Neoantigenome-directed T-cell Responses.

There is evidence that viral oncolysis is synergistic with immune checkpoint inhibition in cancer therapy but the underlying mechanisms are unclear. Here, we investigated whether local viral infection of malignant tumors is capable of overcoming systemic resistance to PD-1-immunotherapy by modulating the spectrum of tumor-directed CD8 T-cells. To focus on neoantigen-specific CD8 T-cell responses, we performed transcriptomic sequencing of PD-1-resistant CMT64 lung adenocarcinoma cells followed by algorithm-based neoepitope prediction. Investigations on neoepitope-specific T-cell responses in tumor-bearing mice demonstrated that PD-1 immunotherapy was insufficient whereas viral oncolysis elicited cytotoxic T-cell responses to a conserved panel of neoepitopes. After combined treatment, we observed that PD-1-blockade did not affect the magnitude of oncolysis-mediated antitumoral immune responses but a broader spectrum of T-cell responses including additional neoepitopes was observed. Oncolysis of the primary tumor significantly abrogated systemic resistance to PD-1-immunotherapy leading to improved elimination of disseminated lung tumors. Our observations were confirmed in a transgenic murine model of liver cancer where viral oncolysis strongly induced PD-L1 expression in primary liver tumors and lung metastasis. Furthermore, we demonstrated that combined treatment completely inhibited dissemination in a CD8 T-cell-dependent manner. Therefore, our results strongly recommend further evaluation of virotherapy and concomitant PD-1 immunotherapy in clinical studies.

Microsphere priming facilitates induction of potent therapeutic T-cell immune responses against autochthonous liver cancers.

Immunotherapy of solid tumors is often hampered by the low frequency of tumor-specific T cells elicited by current vaccination strategies. Here, we describe a prime-boost vaccination protocol based on the administration of antigen conjugated to poly-lactic-co-glycolic acid (PLGA) microspheres followed by booster vaccination with Listeria monocytogenes vectors, which rapidly generates potent immune responses within two weeks. Compared with conventional vaccination with antigen-pulsed dendritic cells, the use of PLGA microspheres resulted in immune responses of significantly higher magnitude, which could be further enhanced via coinjection of TLR 3 agonists. In an immunocompetent model of subcutaneous hepatocellular carcinoma, PLGA/Listeria vaccination resulted in complete remission of established tumors and prolonged survival. To further test the efficacy of the novel vaccination for the treatment of solid tumors, we developed an orthotopic liver cancer model based on the injection of transposon-flanked plasmids expressing oncogenes and model antigens. In this transgenic mouse model of liver cancer, PLGA/Listeria vaccination resulted in eradication of liver tumors, long-term survival of animals and establishment of stable cancer-specific memory CD8(+) T-cell populations. Therefore, combined PLGA/Listeria vaccination holds promise as a novel immunotherapeutic option for the treatment of solid cancers and as a means to boost the therapeutic efficacy of established cancer vaccines.

Endocavitary contrast-enhanced ultrasound: a technique whose time has come?

Endocavitary use of contrast agents in sonography (US) is a relatively new method in diagnostic imaging, competing against gray-scale US, fluoroscopy, and endoscopy. This article describes established indications, demonstrates the techniques of evolving applications, and discusses their potential benefits. These benefits include the ability to obtain precise information about the placement of drains and the extent of fluid collections, and to accurately identify the location and features of strictures in various organs, and those of complications of fluid collections or abscesses, without resorting to ionizing radiation.

Targeted therapies in metastatic colorectal cancer: a systematic review and assessment of currently available data.

BACKGROUND: Survival of patients with metastatic colorectal cancer (mCRC) has been significantly improved with the introduction of the monoclonal antibodies targeting the vascular endothelial growth factor (VEGF) and the epidermal growth factor receptor (EGFR). Novel molecular-targeted agents such as aflibercept and regorafenib have recently been approved. The aim of this review is to summarize and assess the effects of molecular agents in mCRC based on the available phase II and III trials, pooled analyses, and meta-analyses/systematic reviews. METHODS: A systematic literature search was conducted using the meta-database of the German Institute of Medical Documentation and Information. Criteria of the Scottish Intercollegiate Guidelines Network were used to assess the quality of the controlled trials and systematic reviews/meta-analyses. RESULTS: Of the 806 retrieved records, 40 publications were included. For bevacizumab, efficacy in combination with fluoropyrimidine-based chemotherapy in first- and subsequent-line settings has been shown. The benefit of continued VEGF targeting has also been demonstrated with aflibercept and regorafenib. Cetuximab is effective with fluoropyrimidine, leucovorin, and irinotecan (FOLFIRI) in first-line settings and as a single agent in last-line settings. Efficacy for panitumumab has been shown with oxaliplatin with fluoropyrimidine in first-line settings, with FOLFIRI in second-line settings, and as monotherapy in last-line settings. Treatment of anti-EGFR antibodies is restricted to patients with tumors that do not harbor mutations in Kirsten rat sarcoma and in neuroblastoma RAS. CONCLUSION: Among various therapeutic options, the future challenge will be a better selection of the population that will benefit the most from specific anti-VEGF or anti- EGFR treatment and a careful consideration of therapy sequence.

Adjuvant gemcitabine therapy improves survival in a locally induced, R0-resectable model of metastatic intrahepatic cholangiocarcinoma.

UNLABELLED: Complete surgical tumor resection (R0) for treatment of intrahepatic cholangiocarcinoma (ICC) is potentially curative, but the prognosis remains dismal due to frequent tumor recurrence and metastasis after surgery. Adjuvant therapies may improve the outcome, but clinical studies for an adjuvant approach are difficult and time-consuming for rare tumor entities. Therefore, animal models reflecting the clinical situation are urgently needed to investigate novel adjuvant therapies. To establish a mouse model of resectable cholangiocarcinoma including the most frequent genetic alterations of human ICC, we electroporated Sleeping Beauty-based oncogenic transposon plasmids into the left liver lobe of mice. KRas-activation in combination with p53-knockout in hepatocytes resulted in formation of a single ICC nodule within 3-5 weeks. Lineage tracing analyses confirmed the development of ICC by transdifferentiation of hepatocytes. Histologic examination demonstrated that no extrahepatic metastases were detectable during primary tumor progression. However, formation of tumor satellites close to the primary tumor and vascular invasion were observed, indicating early invasion into normal tissue adjacent to the tumor. After R0-resection of the primary tumor, we were able to prolong median survival, thereby observing tumor stage-dependent local recurrence, peritoneal carcinomatosis, and lung metastasis. Adjuvant gemcitabine chemotherapy after R0-resection significantly improved median survival of treated animals. CONCLUSION: We have developed a murine model of single, R0-resectable ICC with favorable characteristics for the study of recurrence patterns and mechanisms of metastasis after resection. This model holds great promise for preclinical evaluation of novel multimodal or adjuvant therapies to prevent recurrence and metastasis after R0-resection.

Meganuclease-mediated virus self-cleavage facilitates tumor-specific virus replication.

Meganucleases can specifically cleave long DNA sequence motifs, a feature that makes them an ideal tool for gene engineering in living cells. In a proof-of-concept study, we investigated the use of the meganuclease I-Sce I for targeted virus self-disruption to generate high-specific oncolytic viruses. For this purpose, we provided oncolytic adenoviruses with a molecular circuit that selectively responds to p53 activation by expression of I-Sce I subsequently leading to self-disruption of the viral DNA via heterologous I-Sce I recognition sites within the virus genome. We observed that virus replication and cell lysis was effectively impaired in p53-normal cells, but not in p53-dysfunctional tumor cells. I-Sce I activity led to effective intracellular processing of viral DNA as confirmed by detection of specific cleavage products. Virus disruption did not interfere with E1A levels indicating that reduction of functional virus genomes was the predominant cause for conditional replication. Consequently, tumor-specific replication was further enhanced when E1A expression was additionally inhibited by targeted transcriptional repression. Finally, we demonstrated p53-dependent oncolysis by I-Sce I-expressing viruses in vitro and in vivo, and demonstrated effective inhibition of tumor growth. In summary, meganuclease-mediated virus cleavage represents a promising approach to provide oncolytic viruses with attractive safety profiles.

Continuation of bevacizumab after first progression in metastatic colorectal cancer (ML18147): a randomised phase 3 trial.

BACKGROUND: Bevacizumab plus fluoropyrimidine-based chemotherapy is standard treatment for first-line and bevacizumab-naive second-line metastatic colorectal cancer. We assessed continued use of bevacizumab plus standard second-line chemotherapy in patients with metastatic colorectal cancer progressing after standard first-line bevacizumab-based treatment. METHODS: In an open-label, phase 3 study in 220 centres in Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, the Netherlands, Norway, Portugal, Saudi Arabia, Spain, Sweden, and Switzerland, patients (aged ≥18 years) with unresectable, histologically confirmed metastatic colorectal cancer progressing up to 3 months after discontinuing first-line bevacizumab plus chemotherapy were randomly assigned in a 1:1 ratio to second-line chemotherapy with or without bevacizumab 2·5 mg/kg per week equivalent (either 5 mg/kg every 2 weeks or 7·5 mg/kg every 3 weeks, intravenously). The choice between oxaliplatin-based or irinotecan-based second-line chemotherapy depended on the first-line regimen (switch of chemotherapy). A combination of a permuted block design and the Pocock and Simon minimisation algorithm was used for the randomisation. The primary endpoint was overall survival, analysed by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00700102. FINDINGS: Between Feb 1, 2006, and June 9, 2010, 409 (50%) patients were assigned to bevacizumab plus chemotherapy and 411 (50%) to chemotherapy alone. Median follow-up was 11·1 months (IQR 6·4-15·6) in the bevacizumab plus chemotherapy group and 9·6 months (5·4-13·9) in the chemotherapy alone group. Median overall survival was 11·2 months (95% CI 10·4-12·2) for bevacizumab plus chemotherapy and 9·8 months (8·9-10·7) for chemotherapy alone (hazard ratio 0·81, 95% CI 0·69-0·94; unstratified log-rank test p=0·0062). Grade 3-5 bleeding or haemorrhage (eight [2%] vs one [<1%]), gastrointestinal perforation (seven [2%] vs three [<1%]), and venous thromboembolisms (19 [5%] vs 12 [3%]) were more common in the bevacizumab plus chemotherapy group than in the chemotherapy alone group. The most frequently reported grade 3-5 adverse events were neutropenia (65 [16%] in the bevacizumab and chemotherapy group vs 52 [13%] in the chemotherapy alone group), diarrhoea (40 [10%] vs 34 [8%], respectively), and asthenia (23 [6%] vs 17 [4%], respectively). Treatment-related deaths were reported for four patients in the bevacizumab plus chemotherapy group and three in the chemotherapy alone group. INTERPRETATION: Maintenance of VEGF inhibition with bevacizumab plus standard second-line chemotherapy beyond disease progression has clinical benefits in patients with metastatic colorectal cancer. This approach is also being investigated in other tumour types, including metastatic breast and non-small cell lung cancers. FUNDING: F Hoffmann-La Roche.

Prediction of resistance to bevacizumab plus FOLFOX in metastatic colorectal cancer-Results of the prospective multicenter PERMAD trial.

BACKGROUND: Anti-vascular endothelial growth factor (VEGF) monoclonal antibodies (mAbs) are widely used for tumor treatment, including metastatic colorectal cancer (mCRC). So far, there are no biomarkers that reliably predict resistance to anti-VEGF mAbs like bevacizumab. A biomarker-guided strategy for early and accurate assessment of resistance could avoid the use of non-effective treatment and improve patient outcomes. We hypothesized that repeated analysis of multiple cytokines and angiogenic growth factors (CAFs) before and during treatment using machine learning could provide an accurate and earlier, i.e., 100 days before conventional radiologic staging, prediction of resistance to first-line mCRC treatment with FOLFOX plus bevacizumab. PATIENTS AND METHODS: 15 German and Austrian centers prospectively recruited 50 mCRC patients receiving FOLFOX plus bevacizumab as first-line treatment. Plasma samples were collected every two weeks until radiologic progression (RECIST 1.1) as determined by CT scans performed every 2 months. 102 pre-selected CAFs were centrally analyzed using a cytokine multiplex assay (Luminex, Myriad RBM). RESULTS: Using random forests, we developed a predictive machine learning model that discriminated between the situations of "no progress within 100 days before radiological progress" and "progress within 100 days before radiological progress". We could further identify a combination of ten out of the 102 CAF markers, which fulfilled this task with 78.2% accuracy, 71.8% sensitivity, and 82.5% specificity. CONCLUSIONS: We identified a CAF marker combination that indicates treatment resistance to FOLFOX plus bevacizumab in patients with mCRC within 100 days prior to radiologic progress.

Transgastrically placed endoscopic vacuum-assisted closure system as an addition to transgastric necrosectomy in necrotizing pancreatitis (with video).

BACKGROUND: Endoscopic transluminal débridement of infected pancreatic necrosis has been proved to be an important alternative to surgical débridement. Recently, endoscopic vacuum-assisted closure (EVAC) has been described as a new effective treatment option in upper intestinal anastomotic leaks. OBJECTIVE: To test whether the EVAC can be applied to transgastrically accessible infected cavities. DESIGN: Single-center case study. SETTING: Academic medical center. PATIENTS: Two patients with necrotizing pancreatitis. MAIN OUTCOME MEASUREMENT: Successful closure of leak. RESULTS: We successfully applied EVAC to treat transgastrically accessible necrotic cavities. LIMITATIONS: Small case number. CONCLUSIONS: EVAC might be an important additional endoscopic treatment option for infected pancreatic necrosis, especially if established endoscopic treatment options fail.

Biliary tract cancer: a survey regarding the current oncological daily care practice in Germany.

BACKGROUND: The low incidence and the variable presentation complicate clinical investigations on biliary tract cancer. The results of Valle et al. in 2009 provided, for the first time, an evidence-based palliative treatment for this rare tumor type. So far no data are available in Germany regarding the current daily care practice. METHODS: We started this national survey in May 2011, including about 3,400 members of the AIO (Working Group Medical Oncology), DGHO (German Society of Hematology and Oncology) and GGHBB (Society of Gastroenterology and Hepatology in Berlin and Brandenburg). The standardized online form contained questions concerning field of action and diagnostic and therapeutic procedures. Evaluation was conducted anonymously. RESULTS: 162 responses could be obtained, corresponding to a response rate of about 5%. 70.4% of the respondents were physicians in hospitals, 23.5% stated to work in private practices. 61.7% of the respondents were medical oncologists and 27.2% gastroenterologists. 52.5% of the participants pointed out to use the standard regimen of gemcitabine and cisplatin. For second-line regimen, the most frequent answer (29%) specified the administration of oxaliplatin in combination with 5-fluorouracil (5-FU) or capecitabine. CONCLUSIONS: This survey may help to clarify the current oncologic daily care procedures for patients with biliary tract cancer in Germany. The results can be helpful for further clinical investigations or the implementation of a tumor-specific register.

Efficacy of Ipilimumab vs FOLFOX in Combination With Nivolumab and Trastuzumab in Patients With Previously Untreated ERBB2-Positive Esophagogastric Adenocarcinoma: The AIO INTEGA Randomized Clinical Trial.

Importance: In metastatic esophagogastric adenocarcinoma (EGA), the addition of programmed cell death 1 (PD-1) inhibitors to chemotherapy has improved outcomes in selected patient populations. Objective: To investigate the efficacy of trastuzumab and PD-1 inhibitors with cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) inhibitors or FOLFOX in first-line treatment of advanced ERBB2-positive EGA. Design, Setting, and Participants: This phase 2 multicenter, outpatient, randomized clinical trial with 2 experimental arms compared with historical control individually was conducted between March 2018 and May 2020 across 21 German sites. The reported results are based on a median follow-up of 14.3 months. Patients with previously untreated, metastatic ERBB2-positive (local immunohistochemistry score of 3+ or 2+/in situ hybridization amplification positive) EGA, adequate organ function, and eligibility for immunotherapy were included. Data analysis was performed from June to September 2021. Interventions: Patients were randomized to trastuzumab and nivolumab (1 mg/kg × 4/240 mg for up to 12 months) in combination with mFOLFOX6 (FOLFOX arm) or ipilimumab (3 mg/kg × 4 for up to 12 weeks) (ipilimumab arm). Main Outcomes and Measures: The primary end point was survival improvement with a targeted increase of the 12-month overall survival rate from 55% (trastuzumab/chemotherapy-ToGA regimen) to 70% in each arm. Results: A total of 97 patients were enrolled, and 88 were randomized (18 women, 70 men; median [range] age, 61 [41-80] years). Baseline Eastern Cooperative Oncology Group performance status was 0 in 54 patients (61%) and 1 in 34 patients (39%); 66 patients (75%) had EGA localized in the esophagogastric junction and 22 in the stomach (25%). Central post hoc biomarker analysis (84 patients) showed PD-1 ligand 1 (PD-L1) combined positive score of 1 or greater in 59 patients (72%) and 5 or greater in 46 patients (56%) and confirmed ERBB2 positivity in 76 patients. The observed overall survival rate at 12 months was 70% (95% CI, 54%-81%) with FOLFOX and 57% (95% CI, 41%-71%) with ipilimumab. Treatment-related grade 3 or greater adverse events (AEs) and serious AEs occurred in 29 and 15 patients in the FOLFOX arm and in 20 and 17 patients in the ipilimumab arm, respectively, with a higher incidence of autoimmune-related AEs in the ipilimumab arm and neuropathy in the FOLFOX arm. Liquid biopsy analyses showed strong correlation of early cell-free DNA increase with shorter progression-free and overall survival and emergence of truncating and epitope-loss ERBB2 resistance sequence variations with trastuzumab treatment. Conclusions and Relevance: In this randomized clinical trial, trastuzumab, nivolumab, and FOLFOX showed favorable efficacy compared with historical data and trastuzumab, nivolumab, and ipilimumab in ERBB2-positive EGA. The ipilimumab arm yielded similar OS compared with the ToGA regimen. Trial Registration: ClinicalTrials.gov Identifier: NCT03409848.

Selectivity of oncolytic viral replication prevents antiviral immune response and toxicity, but does not improve antitumoral immunity.

Oncolytic infection elicits antitumoral immunity, but the impact of tumor-selective replication on the balance between antiviral and antitumoral immune responses has not yet been investigated. To address this question, we constructed the highly tumor-selective adenovirus Ad-p53T whose replication in target tumor cells is governed by aberrant telomerase activity and transcriptional p53 dysfunction. Telomerase-dependent or nonselective adenoviruses were constructed as isogenic controls. Following infection of mice with the nonselective adenovirus, viral DNA and mRNA levels correlated with strong stimulation of innate immune response genes and severe liver toxicity, whereas telomerase-/p53-specific replication did not trigger innate immunity and prevented liver damage. Compared to telomerase-dependent or unselective viral replication, telomerase-/p53-specific virotherapy significantly decreased antiviral CD8-specific immune responses and antiviral cytotoxicity in vivo. Consistent with our hypothesis, telomerase-selective replication led to intermediate results in these experiments. Remarkably, all viruses efficiently lysed tumors and induced a therapeutically effective tumor-directed CD8 cytotoxicity. In immunocompetent mice with extended lung metastases burden, treatment of subcutaneous primary tumors with Ad-p53T significantly prolonged survival by inhibition of lung metastases, whereas unselective viral replication resulted in death by liver failure. In summary, the degree of tumor selectivity of viral replication marginally influences antitumoral immune responses, but is a major determinant of antivector immunity and systemic toxicity.

Targeting of p53-transcriptional dysfunction by conditionally replicating adenovirus is not limited by p53-homologues.

A hallmark of human tumors is the loss of p53 or its transcriptional functions. In this study, we describe the generation of the conditionally replicating adenovirus Adp53sensor for the treatment of p53-dysfunctional tumors. p53-selective attenuation of viral replication was achieved by using p53-dependent expression of the transcriptional repressor Gal4-KRAB that was directed against the adenoviral E1A locus. Adp53sensor shows efficient replication in p53-dysfunctional, but not in p53-active cells. In p53-dysfunctional cells, p53-analogous transcriptional activity by other p53 family members was not sufficient to compromise replication of Adp53sensor. In comparison with a genetically similar, but p53-insensitive virus, Adp53sensor replication was inhibited after systemic infection of p53-wt-mice, but not in p53-ko-mice thus confirming the correct function of the chosen approach. Adp53sensor showed efficient lytic and replicative properties in all investigated cells with p53-dysfunction and successfully inhibited the growth of subcutaneous xenotransplants in vivo. We further demonstrated that intravenous injection of Adp53sensor lead to significantly reduced liver damage compared to the control virus. Together, our data show that Adp53sensor is an oncolytic, p53-selective adenovirus for efficient treatment of p53-dysfunctional tumors with a favorable toxicity profile. Moreover, Adp53sensor provides a strategy that should be applicable to other transcriptionally regulated DNA viruses.

p53-dependent antiviral RNA-interference facilitates tumor-selective viral replication.

RNA-interference (RNAi) is a potent tool for specific gene silencing. In this study, we developed an adenovirus for conditional replication in p53-dysfunctional tumor cells that uses p53-selective expression of a microRNA-network directed against essential adenoviral genes. Compared to a control virus that expressed a scrambled microRNA-network, antiviral RNAi selectively attenuated viral replication in cells with transcriptionally active p53, but not in p53-dysfunctional tumor cells where both viruses replicated equivalently. Since these results were confirmed by an in vivo comparison of both viruses after infection of p53-knockout and normal mice, we could demonstrate that attenuated replication was indeed a result of p53-selective exhibition of antiviral RNAi. Addressing the therapeutic applicability, we could show that the application of RNAi-controlled virus efficiently lysed p53-dysfunctional tumors in vitro and in vivo but resulted in drastically reduced load of virus-DNA in the liver of treated mice. We have generated a broadly applicable adenovirus for selective destruction of p53-dysfunctional tumors and thereby demonstrate that virus-encoded RNAi-networks represent an efficient and versatile tool to modify viral functions. RNAi-networks can be applied to all transcriptionally regulated DNA-viruses to remodulate viral tropism and thus provide means to generate specifically replicating vectors for clinical applications.

Antitumoural immunity by virus-mediated immunogenic apoptosis inhibits metastatic growth of hepatocellular carcinoma.

BACKGROUND AND AIMS: Viral infection of a dying cell dictates the immune response against intracellular antigens, suggesting that virotherapy may be an effective tool to induce immunogenic cell death during systemic cancer treatment. Since viruses and proteasome inhibitors both induce accumulation of misfolded proteins, endoplasmic reticulum (ER) stress and immune responses during treatment of hepatocellular carcinoma (HCC) with bortezomib and the tumour-specifically replicating virus hTert-Ad (human telomerase reverse transcriptase promoter-regulated adenovirus) were investigated. METHODS: Unfolded protein response (UPR) pathways and ER stress-mediated apoptosis were investigated by western blots, caspase-3 assays, 4',6-diamidino-2-phenylindole (DAPI) and Annexin V staining in HCC cells following hTert-Ad/bortezomib treatment. Oncolysis was assessed in subcutaneous HCC mouse models. Antiviral/antitumoural immune responses were characterised in immunocompetent HCC mouse models by ELISA, ELISpot assays and pentamer staining. Systemic efficacy of antitumoural immunity was investigated by determination of lung metastases burden. RESULTS: Bortezomib and hTert-Ad trigger complementary UPR pathways but negatively interfere with important recovery checkpoints, resulting in enhanced apoptosis of HCC cells in vitro and improved oncolysis in vivo. In immunocompetent mice, bortezomib inhibited antiviral immune responses, whereas ER stress-induced apoptosis of infected HCC resulted in caspase-dependent triggering of antitumoural immunity. In therapeutic settings in immunocompetent, but not in immunodeficient or CD8-depleted mice, virotherapy-induced antitumoural immunity efficiently inhibited outgrowth of non-infected lung metastases. Immunotherapeutic efficacy could be significantly improved by bortezomib in experiments with low viral doses. CONCLUSION: Proteasome inhibition during virotherapy disrupts the UPR, leading to enhanced ER stress-induced apoptosis, improved local oncolysis and antitumoural immunity. The results suggest that combining intratumoural virotherapy with adjuvant systemic therapies, which specifically support the function of the virotherapy as an antitumoural vaccine, is a promising immunotherapeutic strategy against HCC.