Intravesical Ad-IFNα Causes Marked Regression of Human Bladder Cancer Growing Orthotopically in Nude Mice and Overcomes Resistance to IFN-α Protein

Abstract

We have produced prolonged, high local concentrations of interferon in vivo by intravesical instillation of adenoviruses encoding interferon-alpha (Ad-IFNalpha) together with the gene transfer-enhancing agent Syn3. We found sustained interferon protein levels for days, both in normal mouse urothelium and in human bladder cancer cells growing as superficial bladder tumors in nude mice using an orthotopic bladder model developed by us. Tumor burden in the bladder was determined utilizing cancer cells containing the green fluorescent protein. Marked tumor regression was observed following two 1-h exposures of Ad-IFNalpha/Syn3 and little or no cytotoxicity was detected in normal cells. Similar intravesical instillation of clinically relevant concentrations of IFN protein alone or Ad-IFNalpha without Syn3 was ineffective. Surprisingly, in vitro, Ad-IFNalpha also caused caspase-dependent death of bladder cancer cell lines that were resistant to high concentrations of IFN-alpha protein, including the cell line used in vivo. These findings demonstrate that Ad-IFNalpha can overcome resistance to IFN-alpha protein both in vitro and in vivo and support evaluation of intravesical Ad-IFNalpha/Syn3 for the treatment of superficial bladder cancer.

Efficacy of a single intravesical treatment with Ad-IFN/Syn 3 is dependent on dose and urine IFN concentration obtained: implications for clinical investigation

“…7,8 In our initial study, we found that two daily 1 h intravesical administrations of Ad-IFNa at a concentration of 1 Â 10 11 particles/ml (P/ml), together with Syn3, produced a marked tumor regression in superficial human bladder tumors. 9 All other treatments including Syn3 alone, Ad-bgal/Syn3, Ad-IFN without Syn3, or the IFN protein alone at high concentration showed no effect on tumor growth. 9 In addition, these studies indicated that Ad-IFNa produced a strong bystander effect and surprisingly was effective in bladder cancer cells which were resistant to the IFN protein.…”

“…9 All other treatments including Syn3 alone, Ad-bgal/Syn3, Ad-IFN without Syn3, or the IFN protein alone at high concentration showed no effect on tumor growth. 9 In addition, these studies indicated that Ad-IFNa produced a strong bystander effect and surprisingly was effective in bladder cancer cells which were resistant to the IFN protein. 9 The protocol for our initial studies, 9 that is, to instill the Ad-IFN/Syn3 for 1 h on two consecutive days was based on optimization studies using Ad-bgal as a marker.…”

“…We used fewer mice as controls since we had previously found that two daily treatments had no effect using our model. 9 At 21 days after the IFNa2a1/Syn3 treatment, the bladders were reimaged.…”

“…9 In addition, these studies indicated that Ad-IFNa produced a strong bystander effect and surprisingly was effective in bladder cancer cells which were resistant to the IFN protein. 9 The protocol for our initial studies, 9 that is, to instill the Ad-IFN/Syn3 for 1 h on two consecutive days was based on optimization studies using Ad-bgal as a marker. 6 These studies showed that highest gene transfer occurred after 1 h treatment on two consecutive days rather than one treatment or an instillation on day 1 and day 4 as well as indicating that a Syn3 concentration of 1 mg/ml also appeared optimal.…”

“…6 These studies showed that highest gene transfer occurred after 1 h treatment on two consecutive days rather than one treatment or an instillation on day 1 and day 4 as well as indicating that a Syn3 concentration of 1 mg/ml also appeared optimal. 6 Nevertheless, because clinical studies were being planned based primarily on our intial findings, 9 certain practical considerations became important. Since intravesical administration is more complicated than intravenous or subcutaneous therapy as well as the fact that large volumes of the reagent are required (approximately 75 ml/treatment), it became an important practical issue to determine if one exposure of Ad-IFN at 1 Â 10 11 P/ml would be as effective as two treatments using our superficial bladder tumor model.…”