RESUMO
STATEMENT: Rapid-cycle deliberate practice (RCDP) is a learner-centered simulation instructional strategy that identifies performance gaps and targets feedback to improve individual or team deficiencies. Learners have multiple opportunities to practice observational, deductive, decision-making, psychomotor, and crisis resource management skills. As its implementation grows, simulationists need to have a shared mental model of RCDP to build high-quality RCDP-based initiatives. To compare and make general inferences from RCDP data, each training needs to follow a similar structure. This article seeks to describe the fundamentals of RCDP, including essential components and potential variants. We also summarize the current published evidence regarding RCDP's effectiveness. This article serves to create a shared understanding of RCDP, provide clear definitions and classifications for RCDP research, and provide options for future RCDP investigation.
Assuntos
Feedback Formativo , Modelos Educacionais , Treinamento por Simulação/organização & administração , Competência Clínica , Avaliação Educacional , Humanos , AprendizagemRESUMO
In the present study, we have taken the novel approach of using an in vitro model representative of tamoxifen-withdrawal subsequent to clinical relapse to achieve a greater understanding of the mechanisms that serve to maintain the resistant-cell phenotype, independent of any agonistic impact of tamoxifen, to identify potential novel therapeutic approaches for this disease state. Following tamoxifen withdrawal, tamoxifen-resistant MCF-7 cells conserved both drug resistance and an increased basal rate of proliferation in an oestrogen deprived environment, despite reduced epidermal growth-factor receptor expression and reduced sensitivity to gefitinib challenge. Although tamoxifen-withdrawn cells retained ER expression, a sub-set of ER-responsive genes, including pS2 and progesterone receptor (PgR), were down-regulated by promoter DNA methylation, as confirmed by clonal bisulphite sequencing experiments. Following promoter demethylation with 5-Azacytidine (5-Aza), the co-addition of oestradiol (E2) restored gene expression in these cells. In addition, 5-Aza/E2 co-treatment induced a significant anti-proliferative effect in the tamoxifen-withdrawn cells, in-contrast to either agent used alone. Microarray analysis was undertaken to identify genes specifically up regulated by this co-treatment. Several anti-proliferative gene candidates were identified and their promoters were confirmed as more heavily methylated in the tamoxifen resistant vs sensitive cells. One such gene candidate, growth differentiation factor 15 (GDF15), was carried forward for functional analysis. The addition of 5-Aza/E2 was sufficient to de-methylate and activate GDF15 expression in the tamoxifen resistant cell-lines, whilst in parallel, treatment with recombinant GDF15 protein decreased cell survival. These data provide evidence to support a novel concept that long-term tamoxifen exposure induces epigenetic silencing of a cohort of oestrogen-responsive genes whose function is associated with negative proliferation control. Furthermore, reactivation of such genes using epigenetic drugs could provide a potential therapeutic avenue for the management of tamoxifen-resistant breast cancer.
Assuntos
Neoplasias da Mama/genética , Resistencia a Medicamentos Antineoplásicos/genética , Estrogênios/farmacologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Inativação Gênica/efeitos dos fármacos , Tamoxifeno/farmacologia , Apoptose/efeitos dos fármacos , Apoptose/genética , Azacitidina/farmacologia , Neoplasias da Mama/patologia , Proliferação de Células/efeitos dos fármacos , Metilação de DNA/efeitos dos fármacos , Metilação de DNA/genética , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Receptores ErbB/metabolismo , Feminino , Gefitinibe , Genes Neoplásicos/genética , Fator 15 de Diferenciação de Crescimento/farmacologia , Humanos , Células MCF-7 , Quinazolinas/farmacologia , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/genética , Receptores de Progesterona/metabolismo , Proteínas Recombinantes/farmacologia , Fator Trefoil-1 , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismoRESUMO
Activated Src kinase may contribute to the progression and spread of breast cancers and recent in vitro evidence suggests a role for Src in acquired endocrine resistance. The purpose of this study was to investigate whether modulation of Src activity in endocrine-sensitive and endocrine-resistant breast cancer cells directly affected their phenotype and sensitivity to 4-hydroxy Tamoxifen (tamoxifen) and to determine whether Src activity in breast cancer tissue affected patient outcome. Expression of constitutively active Src in ER-positive, endocrine-sensitive MCF7 breast cancer cells resulted in the development of an aggressive phenotype, akin to that previously observed in cell models of Tamoxifen resistance, and, significantly, attenuated their response to tamoxifen. Conversely, expression of dominant negative-Src in tamoxifen-resistant MCF7 cells resensitized them to tamoxifen. An exploratory immunohistochemical study of an archival primary breast tumor series (n = 75) with parallel clinicopathological data and in normal breast tissues (n = 19) revealed higher levels of activated Src in the cytoplasm (p < 0.01) and lower levels of nuclear Src (p < 0.01) in tumor tissue compared with normal tissue. Whereas elevated levels of activated-Src in the cytoplasm of tumors was significantly associated with reduced survival in ER+ patients (p = 0.031), elevated levels of activated Src within the nucleus appeared to associate with an improved hormonal response. Together these data are further suggestive of a role for Src in breast cancer where it may alter response to endocrine therapy.
