RESUMO
Persistent activation of the transcription factor, signal transducer and activator of transcription 3 (Stat3) has been shown to mediate several oncogenic features in many types of cancers, including melanoma. In this study, we investigated whether lentiviral (LV) delivery of Stat3-targeting short hairpin RNA (shRNA; LV-shStat3) to K1735-C4 melanoma cells modulates antitumor immunity. Three shStat3 sequences, starting at the position 446, 830 and 1412, were cloned into a mir30 cassette. A shRNA with scrambled sequence served as a control. Transduction with LV-shStat3 resulted in downregulation of Stat3 in vitro. The latter coincided with low cell viability, a reduced expression of survivin and matrix metalloproteinase (MMP)-2. A single injection of LV-shStat3 in K1735-C4 tumors efficiently downregulated Stat3 in vivo and resulted in reduction of both vascular endothelial growth factor secretion and in myeloid-derived suppressor cell (MDSC) numbers. In contrast, we observed an increase in interleukin-6 and interferon-γ secretion, mature dendritic cells (DCs) and CD8(+) T cells. Both DCs and CD8(+) T cells displayed enhanced activity, whereas granulocytic MDSCs lost their suppressive capacity upon Stat3 downregulation. Importantly, a single injection of LV-shStat3 was sufficient to reduce tumor growth, hence prolong survival of tumor-bearing mice. These data demonstrate that Stat3 downregulation in melanoma reinvigorates existing antitumor immunity.
Assuntos
Melanoma Experimental/genética , Melanoma/genética , Fator de Transcrição STAT3/genética , Microambiente Tumoral/imunologia , Animais , Linhagem Celular Tumoral , Sobrevivência Celular , Regulação para Baixo , Feminino , Regulação Neoplásica da Expressão Gênica , Vetores Genéticos , Células HEK293 , Humanos , Proteínas Inibidoras de Apoptose/metabolismo , Lentivirus/genética , Metaloproteinase 2 da Matriz/metabolismo , Melanoma/imunologia , Melanoma/metabolismo , Melanoma/terapia , Melanoma Experimental/imunologia , Melanoma Experimental/metabolismo , Melanoma Experimental/terapia , Camundongos , Camundongos Endogâmicos C57BL , RNA Interferente Pequeno/administração & dosagem , Proteínas Repressoras/metabolismo , Fator de Transcrição STAT3/metabolismo , Survivina , Transdução Genética , Células Tumorais CultivadasRESUMO
Over the years, there has been an exponential increase in the number of gene therapy approaches that are under investigation for the treatment of cancer. This can be attributed to our growing understanding of the molecular mechanisms that contribute to the onset and maintenance of cancer as well as to the development of gene delivery vectors. In this review, we will focus on the use of lentiviral vectors (LVs) in immuno gene therapy of cancer, as these efficacious gene delivery vehicles have come to the fore front because of their many attractive features. LVs have been successfully applied to generate potent dendritic cell based anti-cancer vaccines and to deliver cancer-specific receptors to T-cells. Moreover, LVs are under investigation for the modulation of cancer cells. We will describe various strategies of this 'genuine' cancer gene therapy, amongst which transfer of suicide genes, modulation of pro- and anti-apoptotic molecules, strategies to optimize chemo- and radiotherapy, expression of molecules that affect angiogenesis or affect the immunogenicity of tumor cells. These will be discussed in view of our current knowledge of tumor immunology. Finally we will discuss some important issues and future directions to push the field forward.
