RESUMO
Our laboratory has investigated replicating adenovirus-human sodium iodide symporter (Ad-hNIS) vectors in a combinatorial oncolytic approach known as radiovirotherapy. However, hNIS-mediated iodide sequestration requires an intact cell membrane, and the enhancement of infectivity may alter the radioiodide accumulation in vivo. To assess these effects, we constructed Ad-NIS vectors expressing NIS from the major late promoter. Viral tropism was altered using a hybrid Ad5/3 fiber, and rates of viral spread altered through expression of the Ad death protein (ADP). The hybrid 5/3 fiber enhanced Ad-mediated cytolysis and radioisotope uptake in vitro. Replicating ADP-lacking viral vectors showed levels of uptake similar to non-replicating vectors that declined as cells lysed. ADP expression enhanced the rate of cell lysis and viral release, but reduced the peak and duration of radioiodide uptake. SPECT-computed tomography imaging showed the Ad5/3-noADP-hNIS vector induced significantly more isotope uptake than other vector structures, indicating that viral spread may not always make up for the reduced NIS expression as in our work with prostate cancer. These results indicate that replicating, infectivity-enhanced Ad-NIS vectors provide superior overall efficacy, but also indicate that the effect of replication speed requires tumor and model-specific testing.
Assuntos
Adenovírus Humanos/genética , Vetores Genéticos/genética , Radioisótopos do Iodo/metabolismo , Simportadores/genética , Replicação Viral , Linhagem Celular Tumoral , Efeito Citopatogênico Viral , Expressão Gênica , Ordem dos Genes , Vetores Genéticos/administração & dosagem , Humanos , Vírus Oncolíticos/genética , Simportadores/metabolismo , Transplante HeterólogoRESUMO
We have constructed a prostate tumor-specific conditionally replicating adenovirus (CRAd), named Ad5PB_RSV-NIS, which expresses the human sodium iodine symporter (NIS) gene. LNCaP tumors were established in nude mice and infected with this CRAd to study tumor viral spread, NIS expression, and efficacy. Using quantitative PCR, we found a linear correlation between the viral dose and viral genome copy numbers recovered after tumor infection. Confocal microscopy showed a linear correlation between adenovirus density and NIS expression. Radioiodide uptake vs virus dose-response curves revealed that the dose response curve was not linear and displayed a lower threshold of detection at 10(7) vp (virus particles) and an upper plateau of uptake at 10(11) vp. The outcome of radiovirotherapy was highly dependent upon viral dose. At 10(10) vp, no significant differences were observed between virotherapy alone or radiovirotherapy. However, when radioiodide therapy was combined with virotherapy at a dose of 10(11) vp, significant improvement in survival was observed, indicating a relationship between viral dose-response uptake and the efficacy of radiovirotherapy. The reasons behind the differences in radioiodide therapy efficacy can be ascribed to more efficient viral tumor spread and a decrease in the rate of radioisotope efflux. Our results have important implications regarding the desirable and undesirable characteristics of vectors for clinical translation of virus-mediated NIS transfer therapy.
Assuntos
Radioisótopos do Iodo , Terapia Viral Oncolítica , Neoplasias da Próstata/radioterapia , Neoplasias da Próstata/virologia , Simportadores/genética , Adenoviridae/genética , Proteína de Ligação a Androgênios/genética , Animais , Linhagem Celular Tumoral , Terapia Combinada , Vetores Genéticos , Humanos , Masculino , Camundongos , Neoplasias da Próstata/patologia , Transfecção , Resultado do Tratamento , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The sodium-iodide symporter (NIS) directs the uptake and concentration of iodide in thyroid cells. We have extended the use of NIS-mediated radioiodine therapy to prostate cancer. We have developed a prostate tumor specific conditionally replicating adenovirus that expresses hNIS (Ad5PB_RSV-NIS). For radiovirotherapy to be effective in humans, the radioiodine dose administered in the pre-clinical animal model should scale to the range of acceptable doses in humans. We performed (131)I dose-response experiments aiming to determine the dose required in mice to achieve efficient radiovirotherapy. Efficacy was determined by measuring tumor growth and survival times. We observed that individual tumors display disparate growth rates that preclude averaging within a treatment modality indicating heterogeneity of growth rate. We further show that a statistic and stochastic approach must be used when comparing the effect of an anti-cancer therapy on a cohort of tumors. Radiovirotherapy improves therapeutic value over virotherapy alone by slowing the rate of tumor growth in a more substantial manner leading to an increase in survival time. We also show that the radioiodine doses needed to achieve this increase scaled well within the current doses used for treatment of thyroid cancer in humans.
Assuntos
Adenoviridae/fisiologia , Radioisótopos do Iodo/administração & dosagem , Terapia Viral Oncolítica/métodos , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/terapia , Simportadores/genética , Adenoviridae/genética , Adenoviridae/metabolismo , Animais , Processos de Crescimento Celular/efeitos da radiação , Linhagem Celular Tumoral , Relação Dose-Resposta à Radiação , Vetores Genéticos/genética , Humanos , Masculino , Camundongos , Camundongos Nus , Neoplasias da Próstata/genética , Neoplasias da Próstata/virologia , Taxa de Sobrevida , Simportadores/biossíntese , Simportadores/metabolismo , Transfecção , Replicação Viral , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The sodium iodide symporter (NIS) directs the uptake and concentration of iodide in thyroid cells. We have extended the use of NIS-mediated radioiodine therapy to other types of cancer, we transferred and expressed the NIS gene into prostate, colon and breast cancer cells using adenoviral vectors. To improve vector efficiency we have developed a conditionally replicating adenovirus (CRAd) in which the E1a gene is driven by the prostate-specific promoter, Probasin and the cassette RSV promoter human NIScDNA-bGH polyA replaces the E3 region (CRAd Ad5PB_RSV-NIS). In vitro infection of the prostate cancer cell line LnCaP resulted in virus replication, cytolysis and release of infective viral particles. Conversely, the prostate cancer cell line PC-3 (androgen receptor negative) and the pancreatic cancer cell line Panc-1 were refractory to the viral cytopathic effect and did not support viral replication. Radioiodine uptake was readily measurable in LnCaP cells infected with Ad5PB_RSV-NIS 24 h post-infection, confirming NIS expression. In vivo, LnCaP tumor xenografts in nude-mice injected intratumorally with Ad5PB_RSV_NIS CRAd expressed NIS actively as evidenced by 99Tc uptake and imaging. Administration of therapeutic ¹³¹I after virus injection significantly increased survival probability in mice carrying xenografted LnCaP tumors compared with virotherapy alone. These data indicate that Ad5PB_RSV_NIS replication is stringently restricted to androgen-positive prostate cancer cells and results in effective NIS expression and uptake of radioiodine. This construct may allow multimodal therapy, combining cytolytic virotherapy with radioiodine treatment, to be developed as a novel treatment for prostate cancer.