RESUMEN
Abnormal accumulation of defective mitochondria is the hallmark of oncocytes, which are frequently observed in thyroid Hürthle cell lesions. Autophagy is an essential cellular catabolic mechanism for the degradation of dysfunctional organelles and has been implicated in several human diseases. It is yet unknown how autophagic turnover of defective mitochondria in Hürthle cell tumors is regulated. We characterized the expression patterns of molecular markers including Beclin1, LC3, PINK1 and Parkin, which are required for autophagy or mitophagy, in human oncocytic lesions of the thyroid. To undertake mechanistic studies, we investigated autophagy and mitophagy using XTC.UC1 cells, the only in vitro model of Hürthle cell tumors. Beclin1 and LC3 were highly expressed in oncocytes of Hürthle cell tumors. XTC.UC1 showed autophagic responses to starvation and rapamycin treatment, whereas they displayed ineffective activation of mitophagy, which is triggered by the coordinated action of PINK1 and Parkin in response to CCCP. This resulted in a decreased turnover of abnormal mitochondria. The mechanisms underlying defective mitophagy and mitochondrial turnover were investigated by genetic analysis of the PARK2 gene in XTC.UC1 and Hürthle cell tumor tissues. XTC.UC1 and several tumors harbored the V380L mutation, resulting in dysfunctional autoubiquitination and decreased E3 ligase activity. Consistently, oncocytes in Hürthle cell tumors displayed comparable expression of PINK1 but decreased Parkin expression in comparison to normal thyrocytes. The introduction of wild-type Parkin sensitized XTC.UC1 to death induced by CCCP. This study provides a possible etiological basis for oncocytic formation in heterogeneous Hürthle cell tumors through insufficient mitophagy leading to ineffective turnover of aberrant mitochondria caused by dysfunctional Parkin-mediated pathways of mitochondria quality control.
Asunto(s)
Mitofagia , Neoplasias de la Tiroides/enzimología , Ubiquitina-Proteína Ligasas/genética , Adenoma Oxifílico , Adulto , Anciano , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Autofagia , Beclina-1 , Línea Celular Tumoral , Análisis Mutacional de ADN , Femenino , Expresión Génica , Regulación Neoplásica de la Expresión Génica , Estudios de Asociación Genética , Células HEK293 , Humanos , Masculino , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Persona de Mediana Edad , Mutación Missense , Consumo de Oxígeno , Estudios Retrospectivos , Glándula Tiroides/metabolismo , Glándula Tiroides/patología , Neoplasias de la Tiroides/genética , Ubiquitina-Proteína Ligasas/metabolismo , Adulto JovenRESUMEN
Development of resistance to TNF-related apoptosis-inducing ligand (TRAIL) in tumor cells is one of the important problems in cancer treatment. Despite the previous report demonstrating that oligomycin suppressed TNF-induced apoptosis, in our screening of small molecules enhancing cancer cell death to TRAIL, oligomycin A (OMA) was found to enhance TRAIL-induced apoptosis in HeLa cells. CCAAT/enhancer-binding protein homologous protein (CHOP) was found to directly bind to death receptor 5 (DR5) promoter through endoplasmic reticulum stress (ER-stress) signaling and sensitize the cells to TRAIL. Among ER-stress associated proteins, OMA triggered the inositol-requiring enzyme 1 (IRE1) signaling pathway, leading to X-binding protein 1 (XBP1) splicing, CHOP expression and DR5 upregulation. In contrast, small-interfering RNA (siRNA) of CHOP reduced the number of apoptotic cells in response to the co-treatment of TRAIL and OMA. Collectively, our data suggest that OMA enhances apoptotic death of cervical cancer cells to TRAIL through upregulation of CHOP-mediated DR5 expression following ER-stress.
Asunto(s)
Apoptosis/efectos de los fármacos , Oligomicinas/farmacología , Receptores del Ligando Inductor de Apoptosis Relacionado con TNF/metabolismo , Ligando Inductor de Apoptosis Relacionado con TNF/metabolismo , Factor de Transcripción CHOP/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Estrés del Retículo Endoplásmico , Endorribonucleasas/metabolismo , Células HeLa/efectos de los fármacos , Humanos , Mitocondrias/efectos de los fármacos , Regiones Promotoras Genéticas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Empalme de Proteína , ARN Interferente Pequeño/genética , Factores de Transcripción del Factor Regulador X , Transducción de Señal/efectos de los fármacos , Ligando Inductor de Apoptosis Relacionado con TNF/farmacología , Factor de Transcripción CHOP/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Regulación hacia Arriba/efectos de los fármacos , Proteína 1 de Unión a la X-BoxRESUMEN
Patulin is a fungal mycotoxin of Aspergilus and Penicillium that is commonly found in rotting fruits and exerts its potential toxic effect mainly by reactive oxygen species (ROS) generation. However, the effect of patulin on cancer cells as well as its intracellular mechanism has been controversial and not clearly defined yet. In this study, patulin was found to induce G1/S accumulation and cell growth arrest accompanied by caspase-3 activation, PARP cleavage and ATF3 expression in human colon cancer cell line HCT116. Ser/Thr phosphorylation of a transcription factor, EGR-1, was increased while its expression did not change upon patulin treatment to the cells. Knockdown of ATF3 and EGR-1 using their respective siRNAs showed EGR-1 dependent ATF3 expression. Moreover, treatment of the cells with antioxidants N-acetylcysteine (NAC) and glutathione (GSH) revealed that patulin induced ATF3 expression and apoptosis were dependent on ROS generation. ATF3 expression was also increased by patulin in other colorectal cancer cell types, Caco2 and SW620. Collectively, our data present a new anti-cancer molecular mechanism of patulin, suggesting EGR-1 and ATF3 as critical targets for the development of anti-cancer chemotherapeutics. In this regard, patulin could be a candidate for the treatment of colorectal cancers.