RESUMEN
The activity of the tumor suppressor p53 has to be timed and balanced closely to prevent untimely induction of cell death. The stability of p53 depends on the ubiquitin ligase Mdm2 but also on Hsp70 and Hsp90 chaperones that interact with its DNA binding domain (DBD). Using hydrogen exchange mass spectrometry and biochemical methods, we analyzed conformational states of wild-type p53-DBD at physiological temperatures and conformational perturbations in three frequent p53 cancer mutants. We demonstrate that the Hsp70/Hdj1 system shifts the conformational equilibrium of p53 toward a flexible, more mutant-like, DNA binding inactive state by binding to the DNA binding loop. The analyzed cancer mutants are likewise destabilized by interaction with the Hsp70/Hdj1 system. In contrast, Hsp90 protects the DBD of p53 wild-type and mutant proteins from unfolding. We propose that the Hsp70 and Hsp90 chaperone systems assume complementary functions to optimally balance conformational plasticity with conformational stability.
Asunto(s)
Proteínas del Choque Térmico HSP40/química , Neoplasias/genética , Conformación Proteica , Proteína p53 Supresora de Tumor/química , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Proteínas del Choque Térmico HSP40/genética , Proteínas HSP70 de Choque Térmico/química , Proteínas HSP70 de Choque Térmico/genética , Proteínas HSP90 de Choque Térmico/química , Proteínas HSP90 de Choque Térmico/genética , Humanos , Espectrometría de Masas , Chaperonas Moleculares , Neoplasias/patología , Dominios Proteicos/genética , Desplegamiento Proteico , Proteína p53 Supresora de Tumor/genéticaRESUMEN
The tumor suppressor p53 is the most frequently mutated gene in human cancers. Most of the mutations are missense leading to loss of p53 function in inducing apoptosis and senescence. In addition to these autonomous effects of p53 inactivation/dysfunction on tumorigenesis, compelling evidence suggests that p53 mutation/inactivation also leads to gain-of-function or activation of non-autonomous pathways, which either directly or indirectly promote tumorigenesis. Experimental and clinical results suggest that p53 dysfunction fuels pro-tumor inflammation and serves as an immunological gain-of-function driver of tumorigenesis via skewing immune landscape of the tumor microenvironment (TME). It is now increasingly appreciated that p53 dysfunction in various cellular compartments of the TME leads to immunosuppression and immune evasion. Although our understanding of the cellular and molecular processes that link p53 activity to host immune regulation is still incomplete, it is clear that activating/reactivating the p53 pathway in the TME also represents a compelling immunological strategy to reverse immunosuppression and enhance antitumor immunity. Here, we review our current understanding of the potential cellular and molecular mechanisms by which p53 participates in immune regulation and discuss how targeting the p53 pathway can be exploited to alter the immunological landscape of tumors for maximizing therapeutic outcome.
Asunto(s)
Antineoplásicos/uso terapéutico , Regulación Neoplásica de la Expresión Génica , Imidazoles/uso terapéutico , Neoplasias/tratamiento farmacológico , Piperazinas/uso terapéutico , Microambiente Tumoral/efectos de los fármacos , Proteína p53 Supresora de Tumor/agonistas , Apoptosis , Carcinogénesis/efectos de los fármacos , Carcinogénesis/genética , Carcinogénesis/inmunología , Carcinogénesis/patología , Citocinas/genética , Citocinas/inmunología , Humanos , Evasión Inmune , Mutación , FN-kappa B/genética , FN-kappa B/inmunología , Neoplasias/genética , Neoplasias/inmunología , Neoplasias/patología , Proteínas Proto-Oncogénicas c-mdm2/antagonistas & inhibidores , Proteínas Proto-Oncogénicas c-mdm2/genética , Proteínas Proto-Oncogénicas c-mdm2/inmunología , Transducción de Señal , Receptores Toll-Like/genética , Receptores Toll-Like/inmunología , Microambiente Tumoral/genética , Microambiente Tumoral/inmunología , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/inmunologíaRESUMEN
The Hsp70 family protein mortalin is an essential chaperone that is frequently enriched in cancer cells and exists in various subcellular sites, including the mitochondrion, plasma membrane, endoplasmic reticulum, and cytosol. Although the molecular mechanisms underlying its multiple subcellular localizations are not yet clear, their functional significance has been revealed by several studies. In this study, we examined the nuclear fractions of human cells and found that the malignantly transformed cells have more mortalin than the normal cells. We then generated a mortalin mutant that lacked a mitochondrial targeting signal peptide. It was largely localized in the nucleus, and, hence, is called nuclear mortalin (mot-N). Functional characterization of mot-N revealed that it efficiently protects cancer cells against endogenous and exogenous oxidative stress. Furthermore, compared with the full-length mortalin overexpressing cancer cells, mot-N derivatives showed increased malignant properties, including higher proliferation rate, colony forming efficacy, motility, and tumor forming capacity both in in vitro and in vivo assays. We demonstrate that mot-N promotes carcinogenesis and cancer cell metastasis by inactivation of tumor suppressor protein p53 functions and by interaction and functional activation of telomerase and heterogeneous ribonucleoprotein K (hnRNP-K) proteins.
Asunto(s)
Núcleo Celular/metabolismo , Transformación Celular Neoplásica/metabolismo , Proteínas HSP70 de Choque Térmico/metabolismo , Neoplasias/metabolismo , Animales , Western Blotting , Línea Celular , Proliferación Celular , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/patología , Células HCT116 , Proteínas HSP70 de Choque Térmico/genética , Células HeLa , Ribonucleoproteína Heterogénea-Nuclear Grupo K/metabolismo , Humanos , Inmunohistoquímica , Células MCF-7 , Ratones Endogámicos BALB C , Ratones Desnudos , Mutación , Metástasis de la Neoplasia , Neoplasias/genética , Neoplasias/patología , Estrés Oxidativo , Telomerasa/genética , Telomerasa/metabolismo , Trasplante Heterólogo , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
About 50% of human cancers harbor somatic mutations of the tumor suppressor p53 (p53 or Trp53) gene. Many of those mutations result in the inactivation of the p53 pathway and are often associated with the stabilization and accumulation of mutant p53 proteins. Therefore, increased p53 expression in tumors is frequently used as a surrogate marker for p53 mutation and inactivation. Moreover, this elevated p53 expression also makes it an ideal tumor associated antigen (TAA) for cancer vaccines. Recent advances in our understanding of p53 as a crucial transcription factor reveal that p53 is an important sensor of cellular stress under genotoxic, chemotoxic, pathological, and even normal physiological conditions. Experimental and clinical observations by our laboratory and others have demonstrated that p53 also participates in immune regulation as p53 dysfunction skews host immune responses towards pro-inflammation, which further promotes tumor progression. Furthermore, recent studies using a genetic approach revealed that p53-restoration or re-activation led to tumor regression and clearance, which were at least partially caused by the activation of innate antitumor immunity. Since many of the currently used cancer therapeutics, including radiotherapy and chemotherapy, disrupt tumor growth by inducing DNA damage via genotoxic or chemotoxic stress, which activates the p53 pathway in the tumor microenvironment, we postulate that some of those observed therapeutic benefits might also be partially mediated through their immune stimulatory effects. Here, we briefly review our current understanding of the potential cellular and molecular mechanisms by which p53 participates in immune regulation and, subsequently, extend our discussion to the immunostimulatory potential of existing and new approaches of targeting the p53-pathway to alter the immunological landscape of tumors for maximizing immunotherapy outcome.