The clinical efficacy of conditionally replicative oncolytic adenoviruses (CRAd) is still limited by the inefficient infection of the tumor mass. Since tumor growth is essentially the result of a continuous cross-talk between malignant and tumor-associated stromal cells, targeting both cell compartments may profoundly influence viral efficacy. Therefore, we developed SPARC promoter-based CRAds since the SPARC gene is expressed both in malignant cells and in tumor-associated stromal cells. These CRAds, expressing or not the Herpes Simplex thymidine kinase gene (Ad-F512 and Ad(I)-F512-TK, respectively) exerted a lytic effect on a panel of human melanoma cells expressing SPARC; but they were completely attenuated in normal cells of different origins, including fresh melanocytes, regardless of whether cells expressed or not SPARC. Interestingly, both CRAds displayed cytotoxic activity on SPARC positive-transformed human microendothelial HMEC-1 cells and WI-38 fetal fibroblasts. Both CRAds were therapeutically effective on SPARC positive-human melanoma tumors growing in nude mice but exhibited restricted efficacy in the presence of co-administered HMEC-1 or WI-38 cells. Conversely, co-administration of HMEC-1 cells enhanced the oncolytic efficacy of Ad(I)-F512-TK on SPARC-negative MIA PaCa-2 pancreatic cancer cells in vivo. Moreover, conditioned media produced by stromal cells pre-infected with the CRAds enhanced the in vitro viral oncolytic activity on pancreatic cancer cells, but not on melanoma cells. The whole data indicate that stromal cells might play an important role on the outcome of the oncolytic efficacy of conditionally replicative adenoviruses.

BackgroundPleiotrophin is known to promote the survival and differentiation of dopaminergic neurons in vitro and is up-regulated in the substantia nigra of Parkinson's disease patients. To establish whether pleiotrophin has a trophic effect on nigrostriatal dopaminergic neurons in vivo, we injected a recombinant adenovirus expressing pleiotrophin in the substantia nigra of 6-hydroxydopamine lesioned rats.ResultsThe viral vector induced pleiotrophin over-expression by astrocytes in the substantia nigra pars compacta, without modifying endogenous neuronal expression. The percentage of tyrosine hydroxylase-immunoreactive cells as well as the area of their projections in the lesioned striatum was higher in pleiotrophin-treated animals than in controls.ConclusionsThese results indicate that pleiotrophin over-expression partially rescues tyrosine hydroxylase-immunoreactive cell bodies and terminals of dopaminergic neurons undergoing 6-hydroxydopamine-induced degeneration.

Purpose: A33 antigen is a membrane-bound protein expressed in intestinal epithelium that is overexpressed in 95% of primary and metastatic colorectal carcinomas but is absent in most epithelial tissues and tumor types. We hypothesized that A33 promoter might be useful in the design of a conditionally replicative adenovirus for the treatment of colorectal cancer (CRC). Experimental Design: We cloned an A33 promoter fragment (A33Pr) that extends from -105 to +307 bp. Using luciferase activity as a reporter gene, we showed that A33Pr was active in CRC cell lines. We next constructed a conditionally replicative adenovirus named AV22EL where E1A was placed under the control of A33Pr. The tumor-specific oncolytic effect of AV22EL was investigated both in vitro and in vivo. Results: AV22EL induced specific in vitro lysis of human CRC cell lines that expressed A33 and have negligible lytic capacity on cells that lacked or had minimal A33 expression, including normal human colonic cells. In vivo, a marked reduction of tumor growth and increased long-term survival rates were observed in nude mice xenografted with s.c. CRC tumors. Combination with 5-fluorouracil induced an additive effect in vitro with no toxic effects in vivo. Remarkably, AV22EL completely eliminated established hepatic metastases in >90% of mice and restored hepatic function according to biochemical parameters. Its systemic administration induced E1A expression only in the hepatic metastasis but not in normal organs. Conclusions: These data show that AV22EL is a stringently regulated and potent oncolytic agent for the treatment of CRC.Colorectal cancer (CRC) is the second most common cause of cancer mortality in Western countries and claimed >50,000 lives a year only in the United States. 4 Close to 70% of patients that are affected by colorectal carcinoma undergo surgical resection and 30% to 40% of them develop a recurrent disease (1). The liver is the most common site of metastatic CRC and complete resection of hepatic metastases is the only curative option; however, surgery can be done only in 20% of patients at the time of diagnosis and 5-year survival rates average 25% to 40% despite adjuvant chemotherapy (2). Among patients with metastatic colorectal carcinoma receiving as first-line chemotherapy 5-fluorouracil (5-FU) and new medications, such as irinotecan, Xeloda, oxaliplatin, Erbitux, and Avastin, the median time to progression is 8 to 9 months and their mean survival is 15 to 20.5 months (3 -6). It seems therefore that current CRC treatments are rather ineffective on advanced disease, showing the need for more effective and specific therapeutics to significantly increase patients' survival.Conditionally replicative oncolytic adenoviruses (CRAd) have shown promising applications in cancer gene therapy (7,8). One strategy to achieve specific elimination of the tumor mass, avoiding negative undesired effects in contiguous normal tissue, is the use of tumor-selective transcriptional regulation to control the essential early E1 genes, whic...

We have previously designed a conditionally replicative oncolytic adenovirus (CRAd) named Ad-F512 that can target both the stromal and the malignant melanoma cell compartments. The replication capacity of this CRAd is driven by a 0.5-Kb SPARC promoter fragment (named F512). To improve CRAd’s efficacy, we cloned into F512 motives responsive to hypoxia (hypoxia-responsive element (HRE)) and inflammation (nuclear factor kappa B) to obtain a chimeric promoter named κBF512HRE. Using luciferase as a reporter gene, we observed 10–15-fold increased activity under hypoxia and 10–80-fold induction upon tumor necrosis factor-α addition. We next constructed a CRAd (Ad-κBF512HRE) where E1A activity was under κBF512HRE regulation. Treatment of nude mice harboring established tumors made of a mix of SB2 melanoma cells and WI-38 fibroblasts with Ad-κBF512HRE led to the complete elimination of tumors in 100% of mice (8/8). Moreover, Ad-5/3-κBF512HRE, a viral variant pseudotyped with a chimeric 5/3 fiber, exerted a strong lytic effect on CAR-negative melanoma cells and was highly effective in vivo on established tumors made of melanoma cells and WI-38 fibroblasts, leading to the complete elimination of 4/5 tumors. These results indicate that this improved stroma-targeted oncolytic adenovirus can override the resistance of melanoma tumors and might become of significant importance for melanoma therapeutics.

The successful use of transcriptional targeting for cancer therapy depends on the activity of a given promoter inside the malignant cell. Because solid human tumors evolve as a ''cross-talk'' between the different cell types within the tumor, we hypothesized that targeting the entire tumor mass might have better therapeutic effect. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein overexpressed in different human cancers malignant melanomas both in the malignant cells compartment as in the stromal one (fibroblasts and endothelial cells). We have shown that expression of the herpes simplex virus -thymidine kinase (TK) gene driven by the SPARC promoter in combination with ganciclovir inhibited human melanoma cell growth in monolayer as well as in multicellular spheroids. This inhibitory effect was observed both in homotypic spheroids composed of melanoma cells alone as well as in spheroids made of melanoma cells and stromal cells. Expression of the TK gene was also efficient to inhibit the in vivo tumor growth of established melanomas when TK was expressed either by the malignant cells themselves or by coadministered endothelial cells. Our data suggest that the use of therapeutic genes driven by SPARC promoter could be a valuable strategy for cancer therapy aiming to target all the cellular components of the tumor mass.

Purpose: We decided to construct a novel oncolytic adenovirus whose replication was driven by the CDC25B promoter for its use in preclinical models of pancreatic cancer.Experimental Design: We placed the essential E1A gene under control of the CDC25B promoter. Based on preliminary data, we pseudotyped the adenovirus with a chimeric fiber of serotypes 5/3. We investigated the in vitro lytic effect and the in vivo therapeutic efficacy in combination with gemcitabine on human pancreatic tumor xenografts orthotopically growing in nude mice and in tumors growing in Syrian hamsters. We also assessed biochemical markers of hepatic toxicity and CA19.9 levels.Results: AV25CDC exhibited a strong in vitro lytic effect on pancreatic cancer cells. In vivo administration of AV25CDC combined with gemcitabine in mice harboring subcutaneously growing SW1990 pancreatic tumors almost abrogated tumor growth.Nude mice harboring 15-day-old orthotopic tumors, treated intratumorally or systemically with AV25CDC combined with gemcitabine, exhibited 70% to 80% reduction in tumor size compared with control mice that lasted for at least 60 days. Chemovirotherapy treatment induced a return to normal levels of biochemical parameters of hepatic toxicity; these mice exhibited more than 90% reduction in CA19.9 serum levels compared with control. Chemovirotherapy efficacy was confirmed in mice harboring Mia PaCa-2 tumors and in Syrian hamster harboring HaP-T1 tumors. We observed that viral treatment disrupted tumor architecture and induced an increase in MMP-9 activity that might facilitate gemcitabine penetrability.Conclusion: These data demonstrate that AV25CDC is an effective oncolytic agent candidate for pancreatic cancer chemovirotherapy combination.

Cancer development involves changes driven by the epigenetic machinery, including nucleosome positioning. Recently, the concept that adenoviral replication may be driven by tumor specific promoters (TSPs) gained support, and several conditionally replicative adenoviruses (CRAd) exhibited therapeutic efficacy in clinical trials. Here, we show for the first time that placing a nucleosome positioning sequence (NPS) upstream of a TSP combined with Wnt-responsive motifs (pART enhancer) enhanced the TSP transcriptional activity and increased the lytic activity of a CRAd. pART enhanced the transcriptional activity of the gastrointestinal cancer (GIC)-specific REG1A promoter (REG1A-pr); moreover, pART also increased the in vitro lytic activity of a CRAd whose replication was driven by REG1A-Pr. The pART enhancer effect in vitro and in vivo was strictly dependent on the presence of the NPS. Indeed, deletion of the NPS was strongly deleterious for the in vivo antitumor efficacy of the CRAd on orthotopically established pancreatic xenografts. pART also enhanced the specific activity of other heterologous promoters; moreover, the NPS was also able to enhance the responsiveness of hypoxia- and NFκB-response elements. We conclude that NPS could be useful for gene therapy approaches in cancer as well as other diseases.

No abstract