Purpose Melanoma, the most aggressive form of skin cancer, accounts for 75% of all skin cancer-related deaths and current therapeutic strategies are not effective in advanced disease. In the current study, we have investigated the efficacy of orally active small-molecule antagonist targeting CXCR2/CXCR1. Experimental Design Human A375SM melanoma cells were treated with SCH-479833 or SCH-527123, and their effect on proliferation, motility, and invasion was evaluated in vitro. We examined the downstream signaling events in the cells following treatment with antagonists. For in vivo studies, A375SM cells were implanted subcutaneously into athymic nude mice followed by administration of SCH-479833, SCH-527123, or hydroxypropyl-β-cyclodextrin (20%) orally for 21days and their effect on tumor growth and angiogenesis was evaluated. Results Our data show that SCH-479833 or SCH-527123 inhibited the melanoma cell proliferation, chemotaxis, and invasive potential in vitro.Treatment of melanoma cells with SCH-479833 or SCH-527123 also inhibited tumor growth. Histologic and histochemical analyses showed significant (P < 0.05) decreases in tumor cell proliferation and microvessel density in tumors. Moreover, we observed a significant increase in melanoma cell apoptosis in SCH-479833- or SCH-527123-treated animals compared with controls. Conclusion Together, these studies show that selectively targeting CXCR2/CXCR1 with orally active small-molecule inhibitors is a promising therapeutic approach for inhibiting melanoma growth and angiogenesis.

CXCR1 and CXCR2 are G-protein coupled receptors, that have been shown to play important role in tumor growth and metastasis, and are prime targets for the development of novel therapeutics. Here, we report that targeting CXCR2 and CXCR1 activity using orally active small molecule antagonist (SCH-527123, SCH-479833) inhibits human colon cancer liver metastasis mediated by decreased neovascularization and enhanced malignant cell apoptosis. There were no differences in primary tumor growth. These studies demonstrate the important role of CXCR2/1 in colon cancer metastasis and that inhibition of CXCR2 and CXCR1, small molecule antagonists provides a novel therapeutic strategy.

Multiple integrins have been implicated in modulating renal function. Modulation of integrin function can lead to pathophysiological processes associated with diabetic nephropathy such as alterations in the glomerular filtration barrier and kidney fibrosis. The complexity of these pathophysiological changes implies that multiple integrin subtypes might need to be targeted to ameliorate the progression of renal disease. To address this hypothesis, we investigated the effects of MK‐0429, a compound that was originally developed as an αvβ3 inhibitor for the treatment of osteoporosis, on renal function and fibrosis. We demonstrated that MK‐0429 is an equipotent pan‐inhibitor of multiple av integrins. MK‐0429 dose‐dependently inhibited podocyte motility and also suppressed TGF‐β‐induced fibrosis marker gene expression in kidney fibroblasts. Moreover, in the obese ZSF1 rat model of diabetic nephropathy, chronic treatment with MK‐0429 resulted in significant reduction in proteinuria, kidney fibrosis, and collagen accumulation. In summary, our results suggest that inhibition of multiple integrin subtypes might lead to meaningful impact on proteinuria and renal fibrosis in diabetic nephropathy.

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To evaluate the role of protein kinase C (PKC) in regulation of cellular responsiveness to mitogens, we used rat 6 (R6) fibroblasts that stably overexpress the beta 1 isoenzyme of protein kinase C (PKC-beta 1). The potent vasoconstrictor and mitogen endothelin-1 (ET-1; 100 nM) was substantially more effective in stimulating InsP3 accumulation in PKC-beta 1-overexpressing fibroblasts (PKC3 cells) than in control fibroblasts lacking the PKC-beta 1 cDNA insert. PKC3 cells were found to express a 7-fold greater number of endothelin receptors than did control cells, whereas both cell lines showed equivalent Kd values. These receptors were of the ETA subtype, as defined by a 1000-fold greater affinity for ET-1 than for ET-3. Changes in intracellular free Ca2+ levels ([Ca2+]i) in response to ET-1 measured with the fluorescent Ca2+ indicator fura-2 showed that ET-1 was more potent and efficacious in stimulating [Ca2+]i in PKC3 cells than in control fibroblasts. The ET-1-induced Ca2+ rise was completely blocked by the selective ETA antagonist BQ123, but only slightly diminished by extracellular application of 2 mM EGTA. In contrast with the effects of PKC-beta 1 overexpression on responsiveness to ET-1, alpha-thrombin, which was previously found to have a weaker effect on InsP3 accumulation in PKC-beta 1-overexpressing cells, was also a less effective stimulator of [Ca2+]i in PKC3 cells than in control cells. These results demonstrate that, although the Ca2+ response to alpha-thrombin is diminished by PKC-beta 1 overexpression, ETA receptor number and cellular responsiveness to ET-1 are increased in PKC-beta 1-overexpressing cells.