RESUMEN
Chemotherapy-induced emergence of drug resistant cells is frequently observed and is exemplified by the expression of family of drug resistance proteins including, multidrug resistance protein 1 (MDR1). However, a concise mechanism for chemotherapy-induced MDR1 expression is unclear. Mechanistically, mutational selection, epigenetic alteration, activation of the Wnt pathway or impaired p53 function have been implicated. The present study describes that the surviving fraction of cisplatin resistant cells co- upregulate MDR1, BMI1 and acetyl transferase activity of TIP60. Using complementary gain and loss of function approaches, we demonstrate that the expression of MDR1 is positively regulated by BMI1, a stem-cell factor classically known as a transcriptional repressor. Our study establishes a functional interaction between TIP60 and BMI-1 resulting in upregulation of MDR1 expression. Chromatin immunoprecipitation (ChIP) assays further establish that the proximal MDR1 promoter responds to cisplatin in a BMI1 dependent manner. BMI1 interacts with a cluster of E-box elements on the MDR1 promoter and recruits TIP60 resulting in acetylation of histone H2A and H3. Collectively, our data establish a hitherto unknown liaison among MDR1, BMI1 and TIP60 and provide mechanistic insights into cisplatin-induced MDR1 expression resulting in acquired cross-resistance against paclitaxel, doxorubicin and likely other drugs. In conclusion, our results advocate utilizing anti-BMI1 strategies to alleviate acquired resistance to chemotherapy.
Asunto(s)
Antineoplásicos/farmacología , Resistencia a Múltiples Medicamentos/efectos de los fármacos , Resistencia a Antineoplásicos/efectos de los fármacos , Regulación Neoplásica de la Expresión Génica , Histona Acetiltransferasas/genética , Complejo Represivo Polycomb 1/genética , Subfamilia B de Transportador de Casetes de Unión a ATP/agonistas , Subfamilia B de Transportador de Casetes de Unión a ATP/genética , Subfamilia B de Transportador de Casetes de Unión a ATP/metabolismo , Acetilación/efectos de los fármacos , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Cisplatino/farmacología , Doxorrubicina/farmacología , Resistencia a Múltiples Medicamentos/genética , Resistencia a Antineoplásicos/genética , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Células Epiteliales/patología , Femenino , Histona Acetiltransferasas/metabolismo , Histonas/genética , Histonas/metabolismo , Humanos , Lisina Acetiltransferasa 5 , Paclitaxel/farmacología , Complejo Represivo Polycomb 1/agonistas , Complejo Represivo Polycomb 1/metabolismo , Regiones Promotoras Genéticas , Unión Proteica , Transducción de SeñalRESUMEN
Bmi-1 is a member of the Polycomb Repressor Complex1 that mediates gene silencing by regulating chromatin structure and is indispensable for self-renewal of both normal and cancer stem cells. Despite three decades of research that have elucidated the transcriptional regulation, post-translational modifications and functions of Bmi-1 in regulating the DNA damage response, cellular bioenergetics, and pathologies, the entire potential of a protein with such varied function remains to be realized. This review attempts to synthesize the current knowledge on Bmi-1 with an emphasis on its role in both normal physiology and cancer. Additionally, since cancer stem cells are emerging as a new paradigm for therapy resistance, the role of Bmi-1 in this perspective is also highlighted. The wide spectrum of malignancies that implicate Bmi-1 as a signature for stemness and oncogenesis also make it a suitable candidate for therapy. Nonetheless new approaches are vitally needed to further characterize physiological roles of Bmi-1 with the long-term goal of using Bmi-1 as a prognostic marker and a therapeutic target.
RESUMEN
[This corrects the article DOI: 10.1016/j.gendis.2015.04.001.].
RESUMEN
A comparison of IgE recognition by cognate receptors expressed on the C2 canine mastocytoma cell line with analogous events in a rat basophilic leukemia cell line transfected with the alpha-chain subunit of the canine high-affinity IgE receptor using flow cytometry show that canine IgE recognizes the alpha-chain of its cognate receptor on both cell lines. Our study confirms the expression of functional IgE receptors in both cell lines, but receptor-mediated signaling in the C2 line only supports the early stages of downstream signaling as shown by the phosphorylation of the gamma-chain and the failure to effect the phosphorylation of Syk. In contrast RBL-2H3 cells respond to sensitization with IgE and challenge with cognate antigen with tyrosine phosphorylation of the gamma-subunits of the receptor complex followed by downstream phosphorylation of Syk and Ca(2+) mobilization, culminating in beta-hexosaminidase release. We propose that the identification of the precise signaling defect in C2 cells will yield useful information regarding the pathway leading to mast cell exocytosis and facilitate the restoration of the complete signaling cascade through complementation of the missing/defective signal transducer since signaling events downstream of Ca(2+) mobilization are intact as demonstrated by beta-hexosaminidase release following non-immunologic stimulation with the calcium ionophore, A23187.
