The intrinsic oncolytic specificity of vesicular stomatitis virus (VSV) is currently being exploited to develop alternative therapeutic strategies for bladder cancer and other cancers. Previously we reported that oncolytic VSV is a potent agent for intravesical treatment of high risk bladder cancer. We observed that VSV preferentially targeted bladder cancer cells resistant to type I interferon (IFN) treatment. The goal of the current study was to further elucidate the nature of the molecular defect of IFN signaling by which bladder cancer cells become susceptible to VSV infection. Using a tissue microarray composed of human bladder cancer cores, we observed that expression of type I IFN receptor (IFNAR) was decreased relative to normal bladder tissue. Advanced bladder cancers had even lower expression of IFNAR. We found that bladder cancer cells susceptible to VSVinduced lysis had low expression of IFNAR as well. We hypothesized that down-regulation of IFNAR in bladder cancer cells may be a molecular mechanism responsible for resistance to type I IFN treatment and sensitivity to VSV oncolysis. SiRNA knockdown of IFNAR indeed facilitated replication of VSV in cells previously resistant to VSV treatment. Blocking IFNAR with a neutralizing antibody showed a similar effect. Hence down-regulation of IFNAR in bladder cancer may be one of the primary molecular mechanisms for clinical IFN resistance. However, this also facilitates VSV replication and oncolysis in high risk bladder cancers and provides a basis for selecting bladder cancer patients for IFN or oncolytic VSV therapy in future clinical trials.Bladder cancer is the second most common cancer of the urinary tract, and overall ranks among the top 10 cancers in men and women. 1-3 Transitional cell carcinoma (TCC), the most common type of bladder cancer, is associated with both high recurrence and progression rates. Despite initial success with intravesical bacillus Calmette-Guérin (BCG) immunotherapy, up to 80% of patients with high-risk superficial disease develop recurrent tumors, of which 20-30% evolve into more aggressive, potentially lethal cancers. 4 Although intravesical combination therapy of BCG and IFN-a demonstrated superiority over BCG alone, 5 as tumors progress they may acquire molecular defects in their ability to respond to IFN; 6 thus, the effects of combined IFN and BCG treatment may be compromised.VSV is an enveloped, negative-sense RNA virus that selectively replicates in IFN pathway defective cells, but is strongly suppressed in IFN-responsive normal tissues. 7 Indeed, we have previously shown that oncolytic VSV preferentially targeted bladder cancer cells resistant to type I interferon (IFN) treatment and that these viruses are potent agents for intravesical treatment of high risk bladder cancer. 8 VSV may potentially be used to treat bladder cancers refractory to BCG and IFN, if the nature of the impairment in IFN signaling in aggressive bladder cancer is elucidated.In this study, we assessed IFN signaling pathways in bladder cancer cells ...

Targeting HER-2 over-expressing breast cancer cells with trastuzumab has resulted in significant improvements in both disease-free and overall survival rates. However, despite a favorable initial response, some cancer cells become resistant and develop into fatal metastatic disease. Here we report that we can specifically target HER-2 over-expressing and trastuzumab-resistant breast cancer cells by using an engineered lentivirus which has trastuzumab bound to its envelope. In vitro, this lentiviral construct mediated both the expression of reporter genes, such as enhanced green fluorescent protein (EGFP) and firefly luciferase, as well as the therapeutic gene, herpes thymidine kinase (hTK), in HER-2 over-expressing cells. Subsequent application of the pro-drug ganciclovir selectively killed breast cancer cells in which lentivirus mediated expression of hTK. In vivo, we successfully targeted the expression of firefly luciferase to trastuzumab-resistant breast cancer tumors established in nude mice. Furthermore, we found that systemic administration of trastuzumab-bound lentivirus led to expression of EGFP in circulating trastuzumab-resistant breast cancer cells. In conclusion, HER-2 over-expressing breast cancer cells resistant to trastuzumab can be targeted for selective gene expression and destruction by viruses with envelope-proteins engineered to bind to this antibody.

Enabling the transduction of therapeutic gene expression exclusively in diseased sites is the key to developing more effective treatments for advanced prostate cancer using viral-based therapy. While prostate cancers that express high levels of HER-2 are resistant to the killing effects of trastuzumab, they can be targeted for selective gene expression and destruction by lentiviruses with envelope proteins engineered to bind to this therapeutic antibody. More importantly, after intravenous injection, this trastuzumab-bound lentivirus is able to target castration-resistant prostate tumor xenografts, albeit with low efficiency. This proof of principle opens up multiple possibilities for the prevention and treatment of prostate cancer using a viral-based therapy. However, to be safe and more effective, the viral vectors must target prostate cancer cells more selectively and efficiently. A higher degree of specificity and efficiency of cancer cell targeting can be achieved by engineering viral vectors to bind to a specific cell surface marker and by controlling the expression of the therapeutic payload at transcriptional level, with a tissue-specific promoter, and at the translational level, with a regulatory sequences inserted into either the 5'UTR or 3'UTR regions of the therapeutic gene(s). The latter would be designed to ensure that translation of this mRNA occurs exclusively in malignant cells. Furthermore, in order to obtain a potent anti-tumor effect, viral vectors would be engineered to express pro-apoptotic genes, intra-cellar antibodies/nucleotide aptamers to block critical proteins, or siRNAs to knockdown essential cellular mRNAs. Alternatively, controlled expression of an essential viral gene would restore replication competence to the virus and enable selective oncolysis of tumor cells. Successful delivery of such bioengineered viruses may provide a more effective way to treat advanced prostate cancer.

No abstract