ABSTRACT
Quiescin sulfhydryl oxidase 1 (QSOX1) is an enzyme overexpressed by many different tumor types. QSOX1 catalyzes the formation of disulfide bonds in proteins. Because short hairpin knockdowns (KD) of QSOX1 have been shown to suppress tumor growth and invasion in vitro and in vivo, we hypothesized that chemical compounds inhibiting QSOX1 enzymatic activity would also suppress tumor growth, invasion, and metastasis. High throughput screening using a QSOX1-based enzymatic assay revealed multiple potential QSOX1 inhibitors. One of the inhibitors, known as "SBI-183," suppresses tumor cell growth in a Matrigel-based spheroid assay and inhibits invasion in a modified Boyden chamber, but does not affect viability of nonmalignant cells. Oral administration of SBI-183 inhibits tumor growth in 2 independent human xenograft mouse models of renal cell carcinoma. We conclude that SBI-183 warrants further exploration as a useful tool for understanding QSOX1 biology and as a potential novel anticancer agent in tumors that overexpress QSOX1.
Subject(s)
Gene Expression Regulation, Neoplastic/genetics , Kidney Neoplasms/drug therapy , Oxidoreductases Acting on Sulfur Group Donors/therapeutic use , Animals , Female , Humans , Mice , Mice, SCIDABSTRACT
Augmenter of liver regeneration (ALR), produced and released by hepatocytes, has cytoprotective and immunoregulatory effects on liver injury, and has been used in many experimental applications. However, little attention has been paid to the effects of ALR on concanavalin A (Con A)-induced hepatitis. The purpose of this paper is to explore the protective effect of ALR on Con A-induced hepatitis and elucidate potential mechanisms. We found that the ALR pretreatment evidently reduced the amount of ALT and AST in serum. In addition, pro-inflammatory cytokines, chemokines and iNOS were suppressed. ALR pretreatment also decreased CD4(+), CD8(+) T cell infiltration in liver. Besides, we observed that ALR pretreatment was capable of suppressing the activation of several signaling pathways in Con A-induced hepatitis. These findings suggest that ALR can obviously weaken Con A-induced hepatitis and ALR has some certain immune regulation function.
Subject(s)
CD4-Positive T-Lymphocytes/drug effects , CD8-Positive T-Lymphocytes/drug effects , Hepatitis, Animal/drug therapy , Oxidoreductases Acting on Sulfur Group Donors/therapeutic use , Alanine Transaminase/blood , Animals , Aspartate Aminotransferases/blood , CD4-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/immunology , Cells, Cultured , Concanavalin A/immunology , Extracellular Signal-Regulated MAP Kinases/metabolism , Inflammation Mediators/metabolism , Lymphocyte Activation/drug effects , Male , Mice , Mice, Inbred BALB C , NF-kappa B/metabolism , Nitric Oxide Synthase Type II/metabolism , Signal Transduction/drug effectsABSTRACT
Mammalian sulfite oxidase (SO) is a dimeric enzyme consisting of a molybdenum cofactor- (Moco) and haem-containing domain and catalyses the oxidation of toxic sulfite to sulfate. Following sulfite oxidation, electrons are passed from Moco via the haem cofactor to cytochrome c, the terminal electron acceptor. In contrast, plant SO (PSO) lacks the haem domain and electrons shuttle from Moco to molecular oxygen. Given the high similarity between plant and mammalian SO Moco domains, factors that determine the reactivity of PSO towards oxygen, remained unknown. In the present study, we generated mammalian haem-deficient and truncated SO variants and demonstrated their oxygen reactivity by hydrogen peroxide formation and oxygen-consumption studies. We found that intramolecular electron transfer between Moco and haem showed an inverse correlation to SO oxygen reactivity. Haem-deficient SO variants exhibited oxygen-dependent sulfite oxidation similar to PSO, which was confirmed further using haem-deficient human SO in a cell-based assay. This finding suggests the possibility to use oxygen-reactive SO variants in sulfite detoxification, as the loss of SO activity is causing severe neurodegeneration. Therefore we evaluated the potential use of PEG attachment (PEGylation) as a modification method for future enzyme substitution therapies using oxygen-reactive SO variants, which might use blood-dissolved oxygen as the electron acceptor. PEGylation has been shown to increase the half-life of other therapeutic proteins. PEGylation resulted in the modification of up to eight surface-exposed lysine residues of SO, an increased conformational stability and similar kinetic properties compared with wild-type SO.
