Clinical responses observed with imatinib or sorafenib in melanoma patients expressing mutations in KIT.

BACKGROUND: Mutations in KIT are more frequent in specific melanoma subtypes, and response to KIT inhibition is likely to depend on the identified mutation. METHODS: A total of 32 patients with metastatic acral or mucosal melanoma were screened for mutations in KIT exons 11, 13 and 17. RESULTS: KIT mutations were found in 38% of mucosal and in 6% of acral melanomas. Three patients were treated with imatinib and one with sorafenib. All four patients responded to treatment, but three have since progressed within the brain. CONCLUSION: The observed clinical responses support further investigation of KIT inhibitors in metastatic melanoma, selected according to KIT mutation status.

Local inhibition of nitric oxide temporarily stimulates aldosterone secretion in conscious sheep in vivo.

The effect of localized blockage of endogenous nitric oxide (NO) on basal aldosterone secretion was studied in conscious sheep with autotransplanted adrenal glands. We have shown that infusion of the NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 130 microg/l blood flow) significantly stimulated basal aldosterone secretion rate (ASR). This stimulatory effect was seen up to 4 h of infusion. Beyond this time point, however, the elevated ASR level was not sustained, and it was seen to drop markedly to lower than control values at 5 h. L-NAME had no effect on cortisol secretion rate (FSR) during the first 4 h of infusion, but a significant reduction in FSR was seen by the 8-h time point. Adrenal blood flow was consistently decreased in association with long L-NAME infusion. Additionally, L-NAME was shown to have no effect on aldosterone secretion when infused systemically. We conclude that the relationship between NO and aldosterone secretion is an inhibitory one, in which NO seems to have a negative effect on basal aldosterone secretion.

Functional glucocorticoid receptors in the mesonephros of the ovine fetus.

BACKGROUND: At 27 days of gestation in the ovine fetus (term = 145 to 150 days), the only kidney is the mesonephros, and allantoic fluid represents fetal urine. The hypothesis tested in this study was that functional glucocorticoid receptors (GRs) are present in this early mesonephric kidney. METHODS: Pregnant ewes, between 26 and 30 days, were infused with saline, dexamethasone (0.48 mg/hour), cortisol (5 mg/hour), or aldosterone (10 microg/hour) for 48 hours and were then killed for collection of fetuses and fetal fluids. GR mRNA was measured by real-time polymerase chain reaction in whole fetuses, and the location of gene expression was determined by hybridization histochemistry. RESULTS: Significant changes in allantoic fluid composition were produced by the exposure of the fetus to maternally infused synthetic (dexamethasone) and natural (cortisol) glucocorticoids, over a period of two days, compared with fetuses of ewes infused with vehicle (isotonic saline; N = 8) or aldosterone (N = 8). Volume of fluid was unchanged by any treatment, but both dexamethasone (N = 10) and cortisol (N = 8) caused significant (P < 0.05) decreases in sodium and chloride concentrations and increases in concentrations of potassium, urea, glucose, and fructose. GR mRNA was detected in equivalent concentrations in the whole fetuses of saline, dexamethasone, and cortisol treatments. The GR mRNA levels were significantly decreased in the aldosterone group. By hybridization histochemistry, GR mRNA was detected in most of the tubular cells of the mesonephros. CONCLUSION: These results suggest that functional GRs are present in the early ovine mesonephros.

Effect of adrenomedullin infusion on basal and stimulated aldosterone secretion in conscious sheep with cervical adrenal autotransplants.

In vivo and in vitro studies have shown conflicting effects of adrenomedullin (ADM) on the secretion of steroid hormones from the adrenal gland. While some investigators report no effect of this peptide on the output of various hormones, others have reported both stimulatory and inhibitory roles for ADM. We have shown that basal aldosterone secretion rate (ASR), in conscious sheep with cervical adrenal autotransplants, did not change when ADM was infused directly into the adrenal arterial supply. While not affecting basal ASR, ADM did produce pronounced increases in adrenal blood flow (BF). This elevation of BF in association with ADM infusion was seen in all subsequent experiments. When aldosterone output was acutely stimulated by angiotensin II (AngII), potassium chloride (KCl) and adrenocorticotrophic hormone (ACTH), ADM was seen to drastically reduce the secretion of aldosterone with all agonists studied. After pre-exposure to ADM, all three agonists increased ASR but the magnitude of the responses were somewhat blunted. ADM did not have the same effect on cortisol secretion stimulated by ACTH, suggesting that the ability of this peptide to influence adrenal gland function is limited to the zona glomerulosa. In conditions of chronic elevation of aldosterone levels, such as in Na deficiency, ADM did not display the same inhibitory abilities seen in the acute stimulation experiments. Hence, ADM has been shown to have a direct, inhibitory role on the acute stimulation of aldosterone by AngII, KCl and ACTH while not affecting basal or chronic aldosterone secretion or cortisol secretion stimulated by ACTH.

Roles of insulin-like growth factor (IGF) receptors and IGF-binding proteins in IGF-II-induced proliferation and differentiation of L6A1 rat myoblasts.

Insulin-like growth factor II (IGF-II) stimulates the proliferation and differentiation of rat myoblasts. Previous studies suggest that these response are mediated by the IGF-I receptor, but the IGF-II/mannose 6-phosphate receptor was recently implicated in differentiation of mouse myoblasts. L6A1 myoblasts synthesize IGF-binding protein-4 (IGFBP-4), IGFBP-5, and IGFBP-6, which modulate IGF action. We studied the roles of IGF receptors and IGFBPs in L6A1 myoblast proliferation and differentiation by comparing the effects of IGF-II and a number of IGF-II mutants with decreased affinities for IGF receptors and/or IGFBPs. IGF-II induced concentration-dependent proliferation with a maximum increase of 47%; half-maximal proliferation was seen with approximately 50 ng/ml. [Arg54, Arg55]IGF-II bound to the IGF-I receptor with slightly lower affinity than IGF-II, did not bind to the IGF-II/mannose 6-phosphate receptor, and bound to IGFBPs secreted by myoblasts with approximately 16-fold decreased affinity. It induced proliferation with equal potency to IGF-II. [Leu27]IGF-II, which did not bind to the IGF-I receptor but bound to the IGF-II/mannose 6-phosphate receptor and IGFBPs with slightly lower affinity than IGF-II, had a markedly impaired proliferative effect, inducing proliferation only at high concentrations. [Thr48, Ser49, Ile50]IGF-II, which bound to the IGF-I receptor with slightly lower affinity than IGF-II but did not substantially bind to the IGF-II/mannose 6-phosphate receptor or IGFBPs, induced proliferation with approximately 5-fold greater potency than IGF-II. The order of potency in inducing myoblast differentiation was the same, although there was less difference in the relative potencies of IGF-II and mutants. Coincubation of recombinant human (rh) IGFBP-6 in molar excess with IGF-II inhibited myoblast proliferation and differentiation. rhIGFBP-6 was slightly less potent did not inhibit proliferation or proliferation or differentiation induced by [Thr48,Ser49,Ile50]IGF-II. These results suggest that 1) IGF-II-induced proliferation and differentiation of L6A1 myoblasts are predominantly mediated by the IGF-I receptor; 2) the IGF-II/mannose 6-phosphate receptor is not required for these actions of IGF-II; 3) nevertheless, the IGF-II/mannose 6-phosphate receptor may be capable of mediating these actions; and 4) IGFBPs secreted by myoblasts inhibit IGF actions.