Immunotherapy and gene therapy as novel treatments for cancer / Inmunoterapia y terapia génica como nuevos tratamientos contra el cáncer

Abstract The immune system interacts closely with tumors during the disease development and progression to metastasis. The complex communication between the immune system and the tumor cells can prevent or promote tumor growth. New therapeutic approaches harnessing protective immunological mechanisms have recently shown very promising results. This is performed by blocking inhibitory signals or by activating immunological effector cells directly. Immune checkpoint blockade with monoclonal antibodies directed against the inhibitory immune receptors CTLA-4 and PD-1 has emerged as a successful treatment approach for patients with advanced melanoma. Ipilimumab is an anti-CTLA-4 antibody which demonstrated good results when administered to patients with melanoma. Gene therapy has also shown promising results in clinical trials. Particularly, Herpes simplex virus (HSV)-mediated delivery of the HSV thymidine kinase (TK) gene to tumor cells in combination with ganciclovir (GCV) may provide an effective suicide gene therapy for destruction of glioblastomas, prostate tumors and other neoplasias by recruiting tumor-infiltrating lymphocytes into the tumor. The development of new treatment strategies or combination of available innovative therapies to improve cell cytotoxic T lymphocytes trafficking into the tumor mass and the production of inhibitory molecules blocking tumor tissue immune-tolerance are crucial to improve the efficacy of cancer therapy.

Resumen El sistema inmune interactúa íntimamente con los tumores durante el proceso del desarrollo de la enfermedad y su progresión a metástasis. Esta compleja comunicación entre el sistema inmune y las células tumorales puede prevenir o promover el crecimiento del tumor. Los nuevos enfoques terapéuticos que aprovechan los mecanismos inmunológicos, ya sea por el bloqueo de señales inhibitorias o por la activación directa de células efectoras, han mostrado resultados prometedores. El bloqueo de puntos de control inmunológicos (immune-checkpoints) con anticuerpos monoclonales dirigidos contra receptores que normalmente inhiben el sistema inmune, como CTLA-4 o PD-1, ha resultado ser un tratamiento exitoso para pacientes con melanoma avanzado. El fármaco ipilimumab es un anticuerpo anti-CTLA-4 que ha demostrado buenos resultados terapéuticos en pacientes con melanoma. Por otro lado, la terapia génica también ha mostrado resultados prometedores en ensayos clínicos. En especial, la administración de la enzima timidina quinasa del virus Herpes simplex (HSV-TK) en combinación con el fármaco ganciclovir (GCV) ha mostrado ser una terapia suicida muy efectiva para la destrucción de diferentes neoplasias incluyendo glioblastomas y tumores prostáticos, por un mecanismo que involucra el reclutamiento de linfocitos infiltrantes de tumor. Es importante la búsqueda de nuevas estrategias o la combinación de terapias innovadoras, con el fin de involucrar tanto la atracción de linfocitos citotóxicos así como el empleo de moléculas que inhiban la inmunotolerancia del tejido tumoral para mejorar la eficiencia de los tratamientos contra el cáncer.

Terapia génica del cáncer / Genetic therapy of cancer

Gene therapy is a new modality of treatment in which a gene is used to modify or add new biochemical properties to a patient's target cells with therapeutics purposes. Currently, this experimental therapy is under intensive development as an alternative to treat cancer, because it is possible that this therapy may generate a higher antineoplastic activity, more tissue selectivity and less contralateral effects than conventional therapy. After a decade of preclinical and clinical assays, still there are several obstacles that impose limits to the antineoplastic efficacy of this therapy. However, with the advances in molecular biology and related fields, there is a promise to improve, expand and strength the powerful antineoplastic arsenal of gene therapy.