Expression of Endothelin and ETB Receptors in the Megakaryoblastic MEG-01 Cell Line

Activation of the endothelin receptor B (ETRB) in cultured melanocyte precursors promotes cell proliferation while inhibiting differentiation, two hallmarks of malignant transformation. We therefore tested whether ETRB has a similar role in malignant transformation of melanoma. When tested in culture, we find that the selective ETRB antagonist BQ788 can inhibit the growth of seven human melanoma cell lines, but not a human kidney cell line. This inhibition often is associated with increases in pigmentation and in the dendritic shape that is characteristic of mature melanocytes. In three cell lines we also observe a major increase in cell death. In contrast, the endothelin receptor A (ETRA) antagonist BQ123 does not have these effects, although all the cell lines express both ETRA and ETRB mRNA. Extending these studies in vivo, we find that administration of BQ788 significantly slows human melanoma tumor growth in nude mice, including a complete growth arrest in half of the mice treated systemically. Histological examination of tumor sections suggests that BQ788 also enhances melanoma cell death in vivo. Thus, ETRB inhibitors may be beneficial for the treatment of melanoma.

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“…Two micrograms of cDNA was used for each PCR. Primers and conditions were as described previously (18).…”

Section: Methodsmentioning

confidence: 99%

“…To verify that the cells express ETRB, we performed reverse transcription-PCR by using published primer sequences (18). All of these cell lines, including the kidney cells, display a band of the size expected for authentic ETRB mRNA (Fig.…”

Section: Bq788 Induces Signs Of Differentiation and Reduces Thementioning

confidence: 99%

An endothelin receptor B antagonist inhibits growth and induces cell death in human melanoma cells in vitro and in vivo

Lahav

Heffner

Patterson

1999

Proc. Natl. Acad. Sci. U.S.A.

137

119

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“…The ability of ET-1 to promote collagen gel contraction was blocked by an endothelin receptor A/endothelin receptor B (ETA/ETB) receptor antagonist, bosentan (Veniant et al, 1994), and an ETA receptor antagonist, PD156707 (Maguire et al, 1997), but not an ETB antagonist, BQ788 (Hamroun et al, 1995; Figure 2A). Addition of inhibitor alone, in the absence of added ET-1 had no effect on the basal ability of the fibroblast to contract collagen (our unpublished data).…”

Section: Endothelin-1 Promotes the Ability Of Lung Fibroblasts To Conmentioning

confidence: 99%

“…Treatment of lung fibroblasts induces all three pathways tested. niant et al, 1994), the ETA receptor antagonist PD156707 (Maguire et al, 1997), or the ETB receptor antagonist BQ788 (Hamroun et al, 1995) to reduce the contractile phenotype of SSc lung fibroblasts. Because we had earlier determined that wortmannin and LY2494002 blocked the ability of exog- Figure 4.…”

Section: Ssc Lung Fibroblasts Show An Elevated Ability To Contract a mentioning

confidence: 99%

“…ET-1 was not able to further augment contraction of fixed gels ( Figure 1B). Collectively, the results are consistent with the notion that ET-1 does not directly promote ECM contraction, but rather it contributes to this process indirectly via the induction of expression of procontractile proteins.The ability of ET-1 to promote collagen gel contraction was blocked by an endothelin receptor A/endothelin receptor B (ETA/ETB) receptor antagonist, bosentan (Veniant et al, 1994), and an ETA receptor antagonist, PD156707 (Maguire et al, 1997), but not an ETB antagonist, BQ788 (Hamroun et al, 1995; Figure 2A). Addition of inhibitor alone, in the absence of added ET-1 had no effect on the basal ability of the fibroblast to contract collagen (our unpublished data).…”

mentioning

confidence: 99%

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Endothelin-1 Promotes Myofibroblast Induction through the ETA Receptor via a rac/Phosphoinositide 3-Kinase/Akt-dependent Pathway and Is Essential for the Enhanced Contractile Phenotype of Fibrotic Fibroblasts

Chen

Denton

et al. 2004

MBoC

326

307

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The endothelins are a family of endothelium-derived peptides that possess a variety of functions, including vasoconstriction. Endothelin-1 (ET-1) is up-regulated during tissue repair and promotes myofibroblast contraction and migration, hence contributing to matrix remodeling during tissue repair. Here, we show that addition of ET-1 to normal lung fibroblasts induces expression of proteins that contribute to a contractile phenotype, including ␣-smooth muscle actin (␣-SMA), ezrin, moesin, and paxillin. We confirm that ET-1 enhances the ability of lung fibroblasts to contract extracellular matrix, a function essential for tissue repair, through induction of de novo protein synthesis. Blockade of the Akt/ phosphoinositide 3-kinase (PI3-kinase) pathway with LY294002 and wortmannin prevents the ability of ET-1 to induce ␣-SMA, ezrin, paxillin, and moesin and to promote matrix contraction. Dominant negative rac and Akt blocked the ability of ET-1 to promote formation of ␣-SMA stress fibers. Using specific ET-1 receptor inhibitors, we show that ET-1 induces collagen matrix contraction through the ETA, but not the ETB, receptor. Relative to normal pulmonary fibroblasts, fibroblasts cultured from scars of patients with the fibrotic disease systemic sclerosis (scleroderma) show enhanced ET-1 expression and binding. Systemic sclerosis lung fibroblasts show increased ability to contract a collagen matrix and elevated expression of the procontractile proteins ␣-SMA, ezrin, paxillin, and moesin, which are greatly reduced by antagonizing endogenous ET-1 signaling. Thus, blocking ET-1 or the PI3-kinase/Akt cascades might be beneficial in reducing scar formation in pulmonary fibrosis. INTRODUCTIONA complex histological and architectural structure is a prerequisite for effective lung function. In the lung, specialized structures, the alveoli, increase the surface area of the lung, allowing for efficient gas exchange. The maintenance of these specialized structures is in turn dependent on the underlying connective tissue, comprised principally of fibroblasts and extracellular matrix (ECM; for review, see Gadek et al., 1984), which is essential for the mechanical and structural integrity of the lung. As a response to environmental insults, or as a consequence of local inflammatory processes, structural damage to the lung can occur, resulting in a wound healing response. This response consists of an integrated series of biochemical, immunological, and structural changes that result in the de novo synthesis of a new epithelium, blood vessels, and connective tissue (Razzaque and Taguchi, 2003). The proper repair of connective tissue requires synthesis of new ECM components, such as collagen and fibronectin (Badylak, 2002). In addition, repair of connective tissue requires the proper reconstitution of its support function; that is, an appropriate tensile strength must be recreated. This tensile strength results from the remodeling of the newly formed ECM through a combination of cell locomotion and translocation of the flexible collage...

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Expression of Endothelin and ETB Receptors in the Megakaryoblastic MEG-01 Cell Line

Cited by 2 publications

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An endothelin receptor B antagonist inhibits growth and induces cell death in human melanoma cells in vitro and in vivo

An endothelin receptor B antagonist inhibits growth and induces cell death in human melanoma cells in vitro and in vivo

Endothelin-1 Promotes Myofibroblast Induction through the ETA Receptor via a rac/Phosphoinositide 3-Kinase/Akt-dependent Pathway and Is Essential for the Enhanced Contractile Phenotype of Fibrotic Fibroblasts

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