RESUMEN
Constitutive androstane receptor (CAR) is a nuclear hormone receptor that primarily functions in sensing and metabolizing xenobiotics. The basal activity of this receptor is relatively high, and CAR is deemed active in the absence of ligand. The (over)activation can promote drug toxicity and tumor growth. Thus, therapeutic treatments seek inverse agonists to inhibit or modulate CAR activities. To advance our understanding of the regulatory mechanisms of CAR, we used computational and experimental approaches to elucidate three aspects of CAR activation and inactivation: (1) ligand-dependent actions, (2) ligand-orthologue specificity, and (3) constitutive activity. For ligand-dependent actions, we examined the ligand-bound simulations and identified two sets of ligand-induced contacts promoting CAR activation via coactivator binding (H11-H12 contact) or inactivation via corepressor binding (H4-H11 contact). For orthologue specificity, we addressed a puzzling fact that murine CAR (mCAR) and human CAR (hCAR) respond differently to the same ligand (CITCO), despite their high sequence homology. We found that the helix H7 of hCAR is responsible for a stronger binding of the ligand CITCO compared to mCAR, hence a stronger CITCO-induced activation. For basal activity, we reported computer-generated unliganded CAR structures and critical mutagenesis (mCAR's V209A and N333D) results of a cell-based transcription assay. Our results reveal that the basal conformation of CAR shares prominent features with the agonist-bound form, and helix HX has an important contribution to the constitutive activity. These findings altogether can be useful for the understanding of constitutively active receptors and the design of drug molecules targeting them.
Asunto(s)
Modelos Moleculares , Receptores Citoplasmáticos y Nucleares/metabolismo , Secuencia de Aminoácidos , Animales , Receptor de Androstano Constitutivo , Humanos , Ligandos , Ratones , Unión Proteica , Dominios Proteicos , Receptores Citoplasmáticos y Nucleares/agonistas , Receptores Citoplasmáticos y Nucleares/química , TermodinámicaRESUMEN
Increased dermal mucin is a feature of lupus erythematosus (LE); however, its amount and distribution have not been well characterized. The differentiation of LE from other forms of dermatitis can be challenging when other features of LE are subtle or equivocal. One hundred and thirty-five skin specimens showing LE, graft vs. host disease, erythema multiforme/fixed drug eruption, lichen planus, polymorphous light eruption (PMLE), urticaria, eczematous dermatitis and psoriasis and normal skin with and without photodamage were collected. The amounts of mucin in the papillary, superficial reticular and deep reticular dermis were scored from 0 to 3 on hematoxylin-eosin (H&E) and alcian blue (AB) stains, and compared between groups. The mean scores in the reticular dermis were significantly higher in LE than in other categories except PMLE and eczematous dermatitis. A combined H&E + AB score of ≥5 in the superficial reticular dermis gave an overall specificity of 85.7% for LE. Mucin in the papillary dermis failed to distinguish among entities. Normal photodamaged skin showed significantly more mucin in the superficial reticular dermis compared to non-photodamaged skin. While LE is associated with increased mucin deposition, scant to moderate amount of mucin alone has limited specificity and is common in other dermatitides or photodamaged skin.
Asunto(s)
Lupus Eritematoso Cutáneo/metabolismo , Lupus Eritematoso Sistémico/metabolismo , Mucinas/análisis , Piel/metabolismo , Colorantes/química , Dermis/metabolismo , Dermis/patología , Diagnóstico Diferencial , Erupciones por Medicamentos/metabolismo , Erupciones por Medicamentos/patología , Eccema/metabolismo , Eccema/patología , Eritema Multiforme/metabolismo , Eritema Multiforme/patología , Humanos , Liquen Plano/metabolismo , Liquen Plano/patología , Lupus Eritematoso Cutáneo/patología , Lupus Eritematoso Sistémico/patología , Mucinas/metabolismo , Trastornos por Fotosensibilidad/metabolismo , Trastornos por Fotosensibilidad/patología , Estudios Retrospectivos , Sensibilidad y Especificidad , Piel/patología , Rayos Ultravioleta/efectos adversosRESUMEN
Merkel cell carcinoma (MCC) is a lethal, virus-associated cancer that lacks effective therapies for advanced disease. Agents blocking the PD-1/PD-L1 pathway have demonstrated objective, durable tumor regressions in patients with advanced solid malignancies and efficacy has been linked to PD-L1 expression in the tumor microenvironment. To investigate whether MCC might be a target for PD-1/PD-L1 blockade, we examined MCC PD-L1 expression, its association with tumor-infiltrating lymphocytes (TILs), Merkel cell polyomavirus (MCPyV), and overall survival. Sixty-seven MCC specimens from 49 patients were assessed with immunohistochemistry for PD-L1 expression by tumor cells and TILs, and immune infiltrates were characterized phenotypically. Tumor cell and TIL PD-L1 expression were observed in 49% and 55% of patients, respectively. In specimens with PD-L1(+) tumor cells, 97% (28/29) demonstrated a geographic association with immune infiltrates. Among specimens with moderate-severe TIL intensities, 100% (29/29) demonstrated PD-L1 expression by tumor cells. Significant associations were also observed between the presence of MCPyV DNA, a brisk inflammatory response, and tumor cell PD-L1 expression: MCPyV(-) tumor cells were uniformly PD-L1(-). Taken together, these findings suggest that a local tumor-specific and potentially MCPyV-specific immune response drives tumor PD-L1 expression, similar to previous observations in melanoma and head and neck squamous cell carcinomas. In multivariate analyses, PD-L1(-) MCCs were independently associated with worse overall survival (hazard ratio 3.12; 95% CI, 1.28-7.61; p=0.012). These findings suggest that an endogenous immune response promotes PD-L1 expression in the MCC microenvironment when MCPyV is present, and provide a rationale for investigating therapies blocking PD-1/PD-L1 for patients with MCC.
Asunto(s)
Antígeno B7-H1/biosíntesis , Carcinoma de Células de Merkel/metabolismo , Inflamación/metabolismo , Poliomavirus de Células de Merkel/aislamiento & purificación , Neoplasias Cutáneas/metabolismo , Anciano , Antígeno B7-H1/antagonistas & inhibidores , Antígeno B7-H1/genética , Antígeno B7-H1/metabolismo , Carcinoma de Células de Merkel/inmunología , Carcinoma de Células de Merkel/virología , Femenino , Humanos , Inmunohistoquímica , Inflamación/inmunología , Inflamación/virología , Linfocitos Infiltrantes de Tumor/inmunología , Masculino , Estadificación de Neoplasias , Neoplasias Cutáneas/inmunología , Neoplasias Cutáneas/virología , Análisis de SupervivenciaRESUMEN
BACKGROUND: Sox10 is a transcription factor associated with neural crest development. Its expression has been reported in melanocytes and peripheral nerve sheath cells and their associated tumors. OBJECTIVE: To assess Sox10 sensitivity in benign and malignant melanocytic neoplasms of various histologic subtypes and to discern the specificity of Sox10 in distinguishing between melanocytic neoplasms and fibrohistiocytic and histiocytic mimickers. METHODS: Sox10 expression was examined by immunohistochemistry in 145 cases of formalin-fixed paraffin-embedded tissue, including benign and malignant melanocytic lesions of various histologies and stages (n = 83), fibrohistiocytic and histiocytic lesions (n = 33), and peripheral nerve sheath tumors (n = 19), among others (n = 10). RESULTS: Immunoreactivity with Sox10 was observed in 100% (83/83) of benign and malignant melanocytic lesions of various subtypes, as well as in 100% (19/19) of benign and malignant peripheral nerve sheath lesions. Among the fibrohistiocytic proliferations and histiocytoses examined, Sox10 was negative in all cases (0/33). Sox10 expression did not vary by histologic subtype in nevi or melanoma; however, both the percentage of tumor nuclei demonstrating Sox10 expression and the intensity of expression were inversely correlated with malignant potential (nevi, melanoma in situ, invasive and metastatic melanoma) (P < .001, P = .016, respectively). Malignant peripheral nerve sheath tumors also showed decreased mean Sox10 expression and decreased intensity of expression when compared with benign counterparts (P < .001, P = .021, respectively). LIMITATIONS: This is a retrospective study with 145 cases included. CONCLUSIONS: Sox10 is a highly sensitive marker for melanocytic proliferations and may be useful diagnostically when the differential diagnosis includes fibrohistiocytic and histiocytic proliferations demonstrating S100 expression.