RESUMEN
Evolutionary forces that shape regulatory networks remain poorly understood. In mammals, the Rb pathway is a classic example of species-specific gene regulation, as a germline mutation in one Rb allele promotes retinoblastoma in humans, but not in mice. Here we show that p53 transactivates the Retinoblastoma-like 2 (Rbl2) gene to produce p130 in murine, but not human, cells. We found intronic fuzzy tandem repeats containing perfect p53 response elements to be important for this regulation. We next identified two other murine genes regulated by p53 via fuzzy tandem repeats: Ncoa1 and Klhl26. The repeats are poorly conserved in evolution, and the p53-dependent regulation of the murine genes is lost in humans. Our results indicate a role for the rapid evolution of tandem repeats in shaping differences in p53 regulatory networks between mammalian species.
Asunto(s)
Regulación de la Expresión Génica , Proteína p130 Similar a la del Retinoblastoma , Retinoblastoma/genética , Secuencias Repetidas en Tándem/genética , Proteína p53 Supresora de Tumor , Animales , Células Cultivadas , Evolución Molecular , Fibroblastos/citología , Fibroblastos/metabolismo , Humanos , Intrones/genética , Ratones , Mutación , Coactivador 1 de Receptor Nuclear/genética , Coactivador 1 de Receptor Nuclear/metabolismo , Elementos de Respuesta/genética , Proteína p130 Similar a la del Retinoblastoma/genética , Proteína p130 Similar a la del Retinoblastoma/metabolismo , Especificidad de la Especie , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
PURPOSE: Addition of alpelisib to fulvestrant significantly extended progression-free survival in PIK3CA-mutant, hormone receptor-positive (HR+) advanced/metastatic breast cancer in the phase III SOLAR-1 study. The combination of alpelisib and letrozole also had promising activity in phase I studies of HR+ advanced/metastatic breast cancer. NEO-ORB aimed to determine whether addition of alpelisib to letrozole could increase response rates in the neoadjuvant setting.Patients and Methods: Postmenopausal women with HR+, human epidermal growth factor receptor 2-negative, T1c-T3 breast cancer were assigned to the PIK3CA-wild-type or PIK3CA-mutant cohort according to their tumor PIK3CA status, and randomized (1:1) to 2.5 mg/day letrozole with 300 mg/day alpelisib or placebo for 24 weeks. Primary endpoints were objective response rate (ORR) and pathologic complete response (pCR) rate for both PIK3CA cohorts. RESULTS: In total, 257 patients were assigned to letrozole plus alpelisib (131 patients) or placebo (126 patients). Grade ≥3 adverse events (≥5% of patients) in the alpelisib arm were hyperglycemia (27%), rash (12%), and maculo-papular rash (8%). The primary objective was not met; ORR in the alpelisib versus placebo arm was 43% versus 45% and 63% versus 61% in the PIK3CA-mutant and wild-type cohorts, respectively. pCR rates were low in all groups. Decreases in Ki-67 were similar across treatment arms and cohorts. In PIK3CA-mutant tumors, alpelisib plus letrozole treatment induced a greater decrease in phosphorylated AKT versus placebo plus letrozole. CONCLUSIONS: In contrast to initial results in advanced/metastatic disease, addition of alpelisib to 24-week neoadjuvant letrozole treatment did not improve response in patients with HR+ early breast cancer.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/metabolismo , Receptor ErbB-2/metabolismo , Receptores de Estrógenos/metabolismo , Receptores de Progesterona/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Biomarcadores de Tumor , Neoplasias de la Mama/diagnóstico , Neoplasias de la Mama/mortalidad , Proliferación Celular , Fosfatidilinositol 3-Quinasa Clase I/antagonistas & inhibidores , Fosfatidilinositol 3-Quinasa Clase I/genética , Fosfatidilinositol 3-Quinasa Clase I/metabolismo , Femenino , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Letrozol/administración & dosificación , Persona de Mediana Edad , Mutación , Terapia Neoadyuvante , Receptor ErbB-2/genética , Receptores de Estrógenos/genética , Receptores de Progesterona/genética , Transducción de Señal , Tiazoles/administración & dosificación , Resultado del TratamientoRESUMEN
Mutations in p53, although frequent in human cancers, have not been implicated in telomere-related syndromes. Here, we show that homozygous mutant mice expressing p53Δ31, a p53 lacking the C-terminal domain, exhibit increased p53 activity and suffer from aplastic anemia and pulmonary fibrosis, hallmarks of syndromes caused by short telomeres. Indeed, p53Δ31/Δ31 mice had short telomeres and other phenotypic traits associated with the telomere disease dyskeratosis congenita and its severe variant the Hoyeraal-Hreidarsson syndrome. Heterozygous p53+/Δ31 mice were only mildly affected, but decreased levels of Mdm4, a negative regulator of p53, led to a dramatic aggravation of their symptoms. Importantly, several genes involved in telomere metabolism were downregulated in p53Δ31/Δ31 cells, including Dyskerin, Rtel1, and Tinf2, which are mutated in dyskeratosis congenita, and Terf1, which is implicated in aplastic anemia. Together, these data reveal that a truncating mutation can activate p53 and that p53 plays a major role in the regulation of telomere metabolism.