ABSTRACT
CXCR1 and CXCR2 chemokine receptors and their ligands (CXCL1/2/3/7/8) play an important role in tumor progression. Tested to date CXCR1/2 antagonists and chemokine-targeted antibodies were reported to affect malignant cells in vitro and in animal models. Yet, redundancy of chemotactic signals and toxicity hinder further clinical development of these approaches. In this pre-clinical study we investigated the capacity of a novel small molecule dual CXCR1/2 inhibitor, Ladarixin (LDX), to attenuate progression of experimental human melanomas. Our data showed that LDX-mediated inhibition of CXCR1/2 abrogated motility and induced apoptosis in cultured cutaneous and uveal melanoma cells and xenografts independently of the molecular defects associated with the malignant phenotype. These effects were mediated by the inhibition of AKT and NF-kB signaling pathways. Moreover, systemic treatment of melanoma-bearing mice with LDX also polarized intratumoral macrophages to M1 phenotype, abrogated intratumoral de novo angiogenesis and inhibited melanoma self-renewal. Collectively, these studies outlined the pre-requisites of the successful CXCR1/2 inhibition on malignant cells and demonstrated multifactorial effects of Ladarixin on cutaneous and uveal melanomas, suggesting therapeutic utility of LDX in treatment of various melanoma types.
Subject(s)
Antineoplastic Agents/pharmacology , Melanoma, Experimental/drug therapy , Receptors, Interleukin-8A/antagonists & inhibitors , Receptors, Interleukin-8B/antagonists & inhibitors , Sulfonamides/pharmacology , Tumor Microenvironment/drug effects , Animals , Apoptosis/drug effects , Blotting, Western , Cell Adhesion/drug effects , Cell Movement/drug effects , Cell Proliferation/drug effects , Chemotaxis , Humans , Interleukin-8/metabolism , Melanoma, Experimental/metabolism , Melanoma, Experimental/pathology , Mice , Mice, Nude , NF-kappa B , Neovascularization, Pathologic/drug therapy , Neovascularization, Pathologic/metabolism , Neovascularization, Pathologic/pathology , RNA, Messenger/genetics , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction , Tumor Cells, Cultured , Xenograft Model Antitumor AssaysABSTRACT
Bone marrow suppression due to exposure to ionizing radiation is a significant clinical problem associated with radiation therapy as well as with nonmedical radiation exposure. Currently, there are no small molecule agents available that can enhance hematopoietic regeneration after radiation exposure. Here, we report on the effective mitigation of acute hematopoietic radiation syndrome in mice by the synthetic triterpenoid, RTA 408. The administration of a brief course of RTA 408 treatment, beginning 24 h after lethal doses of radiation to bone marrow, significantly increased overall survival. Importantly, treatment with RTA 408 led to the full recovery of steady state hematopoiesis with normalization of the frequency of hematopoietic stem and progenitor cells. Moreover, hematopoietic stem cells from RTA 408-mitigated mice showed lineage-balanced, long-term, multilineage potential in serial transplantation assays, indicative of their normal self-renewal activity. The potency of RTA 408 in mitigating radiation-induced bone marrow suppression makes it an attractive candidate for potential clinical use in treating both therapy-related and unanticipated radiation exposure.
Subject(s)
Acute Radiation Syndrome/drug therapy , Hematopoiesis/drug effects , Hematopoietic Stem Cells/drug effects , Triterpenes/administration & dosage , Acute Radiation Syndrome/pathology , Animals , Bone Marrow Cells/drug effects , Bone Marrow Cells/radiation effects , Dose-Response Relationship, Radiation , Hematopoiesis/radiation effects , Hematopoietic Stem Cells/radiation effects , Mice , Radiation, Ionizing , Radiotherapy/adverse effects , Whole-Body IrradiationABSTRACT
Normal tissue toxicity markedly reduces the therapeutic index of genotoxic anticancer agents, including ionizing radiation. Countermeasures against tissue damage caused by radiation are limited by their potential to also protect malignant cells and tissues. Here, we tested a panel of signal transduction modifiers for selective radioprotection of normal but not tumor tissues. These included three inhibitors of GSK3 (LiCl, SB216763, and SB415286) and two inhibitors of NF-κB (ethyl pyruvate and RTA 408). Among these, the thiol-reactive triterpenoid RTA 408 emerged as a robust and effective protector of multiple organ systems (gastrointestinal, skin, and hemopoietic) against lethal doses of radiation. RTA 408 preserved survival and proliferation of intestinal crypt cells in lethally irradiated mice while reducing apoptosis incidence in crypts and villi. In contrast, RTA 408 uniformly inhibited growth of established CWR22Rv1, LNCaP/C4-2B, PC3, and DU145 xenografts either alone or combined with radiation. Antitumor effects in vivo were associated with reduced proliferation and intratumoral apoptosis and with inhibition of NF-κB-dependent transcription in PC3 cells. Selective protection of normal tissue compartments by RTA 408 critically depended on tissue context and could not be replicated in vitro. Collectively, these data highlight the potential of RTA 408 as a cytoprotective agent that may be safely used in chemoradiation approaches.