RESUMEN
Aberrant activation of phosphatidylinosito-4,5-bisphosphate 3-kinase/protein kinase B (PI3K/AKT) signaling in cancer has led to pursuit of inhibitors for targeting this pathway. However, inhibitors of PI3K and AKT have failed to yield efficacious results without adverse effects. Here, we screened a library containing 441 authenticated traditional chinese medicine (TCM) plant extracts by examining their effect on cell viability of a human mammary epithelial cell line HMEC-PIK3CAH1047R, which expresses mutant PIK3CAH1047R and has constitutively active AKT signaling. We found that Oridonin, an extract from Rabdosia rubescens, reduced cell viability to the greatest extent. Oridonin binds to AKT1 and potentially functions as an ATP-competitive AKT inhibitor. Importantly, Oridonin selectively impaired tumor growth of human breast cancer cells with hyperactivation of PI3K/AKT signaling. Moreover, Oridonin prevented the initiation of mouse mammary tumors driven by PIK3CAH1047R. Our results suggest that Oridonin may serve as a potent and durable therapeutic agent for the treatment of breast cancers with hyperactivation of PI3K/AKT signaling.
RESUMEN
2-Oxoglutarate-dependent dioxygenases, including the EglN prolyl hydroxylases that regulate HIF, can be inhibited with drug-like molecules. EglN2 is estrogen inducible in breast carcinoma cells and the lone Drosophila EglN interacts genetically with Cyclin D1. Although EglN2 is a nonessential gene, we found that EglN2 inactivation decreases Cyclin D1 levels and suppresses mammary gland proliferation in vivo. Regulation of Cyclin D1 is a specific attribute of EglN2 among the EglN proteins and is HIF independent. Loss of EglN2 catalytic activity inhibits estrogen-dependent breast cancer tumorigenesis and can be rescued by exogenous Cyclin D1. EglN2 depletion also impairs the fitness of lung, brain, and hematopoietic cancer lines. These findings support the exploration of EglN2 inhibitors as therapeutics for estrogen-dependent breast cancer and other malignancies.
Asunto(s)
Ciclina D1/metabolismo , Procolágeno-Prolina Dioxigenasa/metabolismo , Animales , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Técnicas de Cultivo de Célula , Línea Celular Tumoral , Ciclina D1/genética , Dioxigenasas/genética , Dioxigenasas/metabolismo , Regulación hacia Abajo , Femenino , Regulación Neoplásica de la Expresión Génica , Células HeLa , Humanos , Immunoblotting , Ratones , Ratones Transgénicos , Procolágeno-Prolina Dioxigenasa/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , TransfecciónRESUMEN
Chromosomal instability (CIN) is a common characteristic in testicular germ cell tumour (TGCT). A functional mitotic checkpoint control is important for accurate chromosome segregation during mitosis. Mitotic arrest deficient 2 (MAD2) is a key component of this checkpoint and inactivation of MAD2 is correlated with checkpoint impairment. The aim of this study was to investigate the function of mitotic checkpoint control in TGCT cells and to study its association with MAD2 expression using 8 TGCT cell lines as well as 23 TGCT tissue samples. We found that in response to microtubule disruption, 6 of 8 TGCT cell lines (75%) failed to arrest in mitosis demonstrated by the decreased mitotic index and aberrant expression of mitosis regulators, indicating that mitotic checkpoint defect is a common event in TGCT cells. This loss of mitotic checkpoint control was correlated with reduced MAD2 protein expression in TGCT cell lines implicating that downregulation of MAD2 may play a critical role in an impaired mitotic checkpoint control in these cells. In addition, immunohistochemistry studies on 23 seminomas and 12 normal testis tissues demonstrated that nuclear expression of MAD2 was much lower in seminomas (p<0.0001) but cytoplasmic MAD2 expression was higher in seminomas (p=0.06) than normal samples. Our results suggest that aberrant MAD2 expression may play an essential role in a defective mitotic checkpoint in TGCT cells, which may contribute to CIN commonly observed in TGCT tumours.