RESUMEN
We have recently demonstrated that a 4-in-1 gene therapy strategy that contains two anti-angiogenic genes [endostatin and pigment epithelium-derived factor] and two cytokine genes [granulocyte macrophage colony-stimulating factor and interleukin 12] has a considerable antitumor effect on large tumors in a woodchuck hepatoma model. The current study further investigates the underlying mechanisms for the antitumor effect observed by using small rodent models. We found that immunotherapy alone increased immunosuppressive cells in large tumors over time, whereas the anti-angiogenic therapy contained in the 4-in-1 strategy alleviated immunosuppression and made tumors vulnerable to immunotherapy, thus resulting in a synergistic antitumor effect.
Asunto(s)
Endostatinas/genética , Endostatinas/inmunología , Proteínas del Ojo/genética , Proteínas del Ojo/inmunología , Terapia Genética/métodos , Inmunoterapia/métodos , Neoplasias Hepáticas Experimentales/terapia , Factores de Crecimiento Nervioso/genética , Factores de Crecimiento Nervioso/inmunología , Serpinas/genética , Serpinas/inmunología , Adenoviridae/genética , Animales , Apoptosis/genética , Apoptosis/inmunología , Línea Celular Tumoral , Terapia Combinada , Endostatinas/biosíntesis , Proteínas del Ojo/biosíntesis , Humanos , Neoplasias Hepáticas Experimentales/irrigación sanguínea , Neoplasias Hepáticas Experimentales/genética , Neoplasias Hepáticas Experimentales/inmunología , Linfocitos Infiltrantes de Tumor/inmunología , Ratones , Ratones Endogámicos BALB C , Neovascularización Patológica/genética , Neovascularización Patológica/inmunología , Neovascularización Patológica/terapia , Factores de Crecimiento Nervioso/biosíntesis , Serpinas/biosíntesis , Linfocitos T Reguladores/inmunología , Microambiente Tumoral/inmunologíaRESUMEN
Tumor-induced angiogenesis has been shown to suppress immune responses. One mechanism is to suppress leukocyte-endothelial cell interaction by down-regulating the expression of adhesion molecules, such as intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1 and E-selectin on the tumor endothelium, which enables tumor cells to escape immune surveillance. Calreticulin (CRT), a chaperone protein mainly located in the endoplasmic reticulum, has been shown to exert anti-angiogenic activity and inhibit tumor growth. Here, we demonstrate that in addition to inhibiting angiogenesis, CRT also enhances the expression of both ICAM-1 and VCAM-1 on tumor endothelial cells. This expression results in enhanced leukocyte-endothelial cell interactions and increased lymphocyte infiltration into tumors. Therefore, combining intramuscular CRT gene transfer with intratumoral cytokine gene therapies significantly improves the antitumor effects of immunotherapy by markedly increasing the levels of tumor-infiltrating lymphocytes. This combined treatment increased the levels of infiltrating lymphocytes to those achieved using four times the cytokine dosage. The combined therapy also resulted in lower levels of immunosuppressive molecules and higher levels of activated T-cells in the tumor microenvironment than immunotherapy alone. In conclusion, this study describes a new antitumor mechanism of CRT that involves the up-regulation of tumor endothelial adhesion molecules and the enhanced infiltration of tumor-specific lymphocytes. Thus, CRT treatment can make tumor cells more vulnerable to immunotherapy and improve the therapeutic efficacy of immunotherapy.