Expression of the ET(A) and ET(B) endothelin receptor subtype mRNA in human detrusor cultured smooth muscle cells

Endothelin-1 overexpression: a potential biomarker of unfavorable prognosis in non-metastatic muscle-invasive bladder cancer

Endothelin-1 (ET-1) is a multifunctional peptide exerting its effects via receptors A and B. ET-1 and its receptors, endothelin axis (ET axis), play a promoting role in cancer biology. Alterations of proteins of ET axis have been detected in non-metastatic muscle-invasive bladder cancer (NMMIBC). The objective of this study is to investigate the potential role of ET-1 tumor expression as a biomarker of prognosis, compared to other prognostic parameters (epidemiologic and pathologic), in NMMIBC. We prospectively included 40 consecutive, primary, high-grade NMMIBC patients. Tumor specimens after initial transurethral resection were stained immunohistochemically for ET-1. The ET-1 evaluation of expression was based on staining intensity (SI) of ET-1. SI was classified according to an arbitrary four-tiered scale (negative = 0, mild = 1, moderate = 2, strong = 3). Epidemiologic and pathologic parameters were analyzed, using univariate and multivariate statistics, for disease progression, progression-free survival (PFS), and overall survival (OS). ET-1 overexpression (SI = 3) was the unique parameter which associated significantly, both in univariate (log-rank test, p = 0.033) and multivariate (Cox regression analysis, p = 0.045, HR = 4.849, 95 % CI: 1.039-22.624) analysis, with an increased hazard ratio of progression. ET-1 overexpression (SI = 3) was also the unique parameter which associated, marginally significantly in univariate analysis (log-rank test, p = 0.056) and highly significantly in multivariate analysis (Cox regression analysis, p = 0.005, HR = 7.001, 95 % CI: 1.782-27.501), with an increased hazard ratio of death. Overexpression of ET-1 may be a potential biomarker of unfavorable prognosis in NMMIBC patients.

The endothelin axis in urologic tumors: mechanisms of tumor biology and therapeutic implications

Endothelin (ET)-1 and its receptors ET-A and ET-B, referred to commonly as the endothelin axis, have been identified in various human cancers, especially gynecologic tumors, such as breast cancer or ovarian cancer, but also including urologic tumor entities. They play a key role in tumor growth and progression by influencing critical cancer pathways, such as apoptosis, angiogenesis and proliferation. In prostate cancer, overexpression of the ET-A receptor increases with tumor progression, and clinical trials with selective ET-A receptor antagonists, such as atrasentan (ABT-627), have shown promising early results. In preclinical models of bladder cancer, overexpression of the ET axis has been demonstrated and ET-targeting agents are under investigation. This paper reviews the role of the ET axis in human cancers and focuses on preclinical and clinical studies in urologic tumor entities to further define the role of ET-targeting agents as targeted molecular therapy.

Inward current oscillation underlying tonic contraction caused via ETA receptors in pig detrusor smooth muscle

Endothelin-1 (ET-1) is a powerful vasoconstricting peptide. Recent studies showed synthesis of ET-1 and the presence of ET receptors in urinary bladder smooth muscle cells. In the present study, we investigated the possible role of ET-1 in detrusor contraction and its underlying mechanisms in terms of electrical activity. ET-1 caused dose-dependent tonic contraction of bladder smooth muscle strips. Whole cell patch-clamp experiments revealed that ET-1 induced a single transient inward current in the majority of detrusor cells and that additional inward current oscillations were induced in one-third of the cells. The inward current oscillation and tonic contraction shared several characteristic features: 1) both activities lasted for a considerable time after ET-1 washout and 2) only prior application of ETA receptor antagonists, not ETB receptor antagonists, significantly suppressed ET-1-induced contractions and the oscillating inward currents. It was concluded that the inward current oscillation underlies ET-1-induced tonic contraction. Experiments with ion substitution and channel blockers suggested that periodic activation of Ca2+-activated Cl- channels caused the oscillating inward currents.