Retinoides (RARβ y CRBP1) en carcinoma de pulmón a células no pequeñas / Retinoid expression (RARβ and CRBP1) in non-small-cell lung carcinoma

Aunque los pacientes con cáncer de pulmón a células no pequeñas en estadios tempranos (NSCLC) tienen buen pronóstico, el 20-30% recae, siendo relevante la identificación de biomarcadores pronósticos. Los retinoides regulan crecimiento y diferenciación, y pueden antagonizar la progresión tumoral. Su efecto depende del transporte citosólico mediado por moléculas como CRBP1, y de la unión a receptores específicos (RARβ). Alteraciones en esta vía se asociaron con cáncer. Nuestro objetivo fue estudiar la expresión, mediante inmunohistoquímica, de RARβ y CRBP1 en el tejido tumoral de 49 pacientes NSCLC Estadio I/II, obtenido durante la cirugía. La supervivencia se analizó mediante los test Log Rank y multivariado de Cox. El 44.9% de los tumores fueron positivos para RARβ con expresión a nivel citoplasmático, mientras que el 34.7% lo expresó a nivel nuclear. La tinción para CRBP1 se observó en el 61.2% de los tumores. No se encontró asociación entre la expresión de ambas moléculas y las características clinicopatológicas (sexo, tamaño tumoral, nódulos línfáticos comprometidos, histopatología y p53). Tampoco se encontró asociación con el hábito de fu-mar. La presencia de células tumorales en el lavado pleural se asoció significativamente con la expresión de CRBP1. Por otro lado, se demostró asociación entre la expresión elevada de RARβ citoplasmático y menor supervivencia global (LR 4.17, p=0.0412). El análisis multivariado no mostró asociación con otras variables de pronóstico en NSCLC. En conclusión, en este grupo de pacientes NSCLC Estadio I/II, RARβ pareciera predecir la supervivencia global en forma independiente.

Although early-stage non-small-cell lung carcinoma (NSCLC) patients have a relative by favorable prognosis, the risk of a bad outcome remains substantial. Identification of reliable prognostic markers for disease recurrence and death has meaningful clinical application. Retinoids are involved in cell growth and differentiation and may antagonize cancer progression. Their effects are mediated through nuclear receptors called Retinoic Acid Receptor (RAR) and regulated by molecules such as Cellular Retinol-Binding Protein 1 (CRBP1) that function in retinol storage. The aim of this work was to analyze by immunohistochemistry the expression patterns of RARβ and CRBP1, involved in retinoid-mediated signaling, in the tumoral tissue of a cohort of stage I/II NSCLC patients (n=49) who underwent a successful surgical resection. Prognostic evaluation was performed with the multivariate Cox proportional hazard model: 44.9% of tumors were positive for RARβ staining at cytoplasmic level, while 34.7% showed nuclear staining. CRBP1 staining was observed in 61.2% of the lung tumors. No relationship was found between the number of cells expressing the studied molecules and clinical pathological features, including sex, T and N (stage), histopathology and p53 expression. Univariate analysis showed a significant association between positive cytoplasmatic expression of RARβ with shorter overall survival (Log-rank test 4.17, p=0.0412). Multivariate studies indicated that RARβ expression was not influenced by other clinical pathological parameters. In conclusion, in this cohort of stage I and II NSCLC, only the expression of RARβ at cytoplasmatic level is a significant independent unfavorable prognostic factor.

Nuevos receptores nucleares heterodiméricos: reguladores metabólicos con impacto en fisiopatología y su proyección terapéutica en dislipidemias y diabetes mellitus / New heterodimeric nuclear receptors: key metabolic regulators with relevance in the pathophysiology and therapy of dyslipidemias and diabetes mellitus

The regulation of gene expression is crucial for the normal development and the homeostatic maintenance of body tissues. Thus, its malfunction may determine a variety of human disease conditions. A growing body of evidence has shown the overwhelming relevance of a new class of gene expression regulators: the heterodimeric nuclear receptors, a family of structurally related proteins involved in multiple biological functions. In response to activating ligands, these molecules bind to specific genomic regulatory regions where they can coordinately modify the transcriptional activity of several genes involved in the main metabolic pathways of lipids and carbohydrates in cells. These functional properties have stimulated the study of the relationships between heterodimeric nuclear receptors and various disease conditions, such as dyslipidemias and diabetes mellitus. Here we review the experimental, clinical and epidemiological evidences that support the relevance of these transcriptional regulators in the pathophysiology of the most prevalent and lethal diseases in Western countries. We also explore the potential therapeutic impact of new strategies based in the pharmacological modulation of the heterodimeric nuclear receptors.

Retinoic Acid Receptor-beta Expression in Stage I Non-Small Cell Lung Cancer and Adjacent Normal Appearing Bronchial Epithelium

Retinoic acid receptor- (RAR-beta) is induced by and mediates the growth-inhibitory and apoptotic effects of retinoic acid (RA), suggesting that loss of RAR-betaexpression may be one of the critical events involved in the carcinogenesis/ progression of non-small cell lung cancer (NSCLC) and in the responsiveness to retinoid chemotherapy. However, recent contradictory reports that the expression of RAR-beta is associated with poor clinical outcome, and the fact that treatment of serum-deprived type 2 alveolar cells with RA leads to a stimulation of cell proliferation, require the verification of RAR-beta as a biomarker of chemoprevention or prognosis. The expression status of RAR-beta in cancer cells and adjacent normal appearing bronchial epithelium from 39 patients, diagnosed as stage I NSCLC and undergone a curative lung resection, was analyzed in paraffin-embedded tissue sections by IHC staining. The normal appearing bronchial epithelium of 14 out of 33 (42.4%) specimens expressed RAR-beta, whereas 22 out of the 39 (56.4%) stage I NSCLC specimens expressed RAR-beta. RAR-beta was more frequently expressed in the adenocarcinoma (72.7%) than in the squamous cell carcinoma (31.3%) (p=0.026). Neither the expression status in normal appearing adjacent tissue nor that in the tumor tissue had prognostic implications. The higher expression of RAR-beta in cancer tissue, the focal and uneven distribution in normal appearing adjacent bronchial epithelium, and inconsistency with the corresponding tumor tissue, suggest that the expression status of RAR-beta as a biomarker for chemoprevention/early diagnosis or the prognosis of NSCLC requires further consideration.

Atividade dos receptores nucleares dos hormônios tireoideanos e do ácido retinóico 9CIS em diferentes elementos responsivos do DNA / Activity of nuclear receptors of thyroid hormones and of retinoid acid 9CIS in differents elements responsives of DNA

O receptor de hormônio tireoidiano (TR) e o receptor do retinóide X (RXR) fazem parte de uma superfamília de receptores nucleares, que em resposta aos seus respectivos ligantes, atuam como fatores de transcriçäo no DNA. Os receptores nucleares possuem uma estrutura modular e a ligaçäo dos mesmos ao DNA se faz como monômeros ou dímeros através do módulo ligador ao DNA (DBD) que se liga a sequências nucleotídicas específicas do DNA, conhecidas como elementos responsivos hormonais (HRE). TR e RXR se ligam a HREs conhecidos como repetiçöes diretas (DRs) do hexâmero AGGTCA (AGGTCAnAGGTCA). t3 e o ácido 9cis-retinóico se ligam a porçäo carboxi-terminal do TR e RXR respectivamente, ativando a transcriçäo gênica. O TR atua principalmente como homodímero ou heterodímero, ligando-se no último caso ao RXR. Nosso estudo analisou a ligaçäo do TR e do RXR a im grupo de DRs separadas por um número variável de nucleotídeos, de 0 a 6, com o objetivo de estabelecer a importância desses HREs na transcriçäo gênica destes receptores nucleares. Confirmamos através de cultura de células e eletroforese em gel de poliacrilamida que o espaçamento ideal para a resposta do T3 medida pelo TR é de 4 nucleotídeos (DR4). A forscolina, um potencializador da proteína cinase A (PKA), foi capaz de potencializar a resposta transcricional do TR ao T3. O RXR pode atuar como parceiro silencioso de outros receptores nucleares, ou como homodímero em resposta ao ácido 9cis-retinóico. Nossos ensaios de eletroforese demonstraram que o RXR pode se ligar como homodímero näo só ao conhecido elemento responsivo DR1, mas também a DR2, DR3, DR4, DR5 e DR6, numa forma dependente de 9cisRA. Em cultura de células a forscolina demonstrou uma evidente açäo sinérgica do RXR nos elementos DR1 a DR5. Desta forma, demonstramos que homodímeros de RXR podem possuir uma atividade transcricional mais ampla do que se acreditava e verificamos a importância de mecanismos de conversa cruzada entre os receptores nucleares TR eRXR com o sistema de sinalizaçäo via AMP cíclico