ABSTRACT
Meridianin C is a marine natural product with anticancer activity. Several meridianin C derivatives (compounds 7aj) were recently synthesized, and their inhibitory effects on proviral integration site for Moloney murine leukemia virus (PIM) kinases, as well as their antiproliferative effects on human leukemia cells, were reported. However, the antileukemic effects and mechanisms of action of meridianin C and its derivatives remain largely unknown. The aim of the present study was to investigate the effects of meridianin C and its derivatives on MV411 human acute myeloid leukemia cell growth. The parent compound meridianin C did not markedly affect the viability and survival of MV411 cells. By contrast, MV411 cell viability and survival were reduced by meridianin C derivatives, with compound 7a achieving the most prominent reduction. Compound 7a notably inhibited the expression and activity of PIM kinases, as evidenced by reduced Bcell lymphoma2 (Bcl2)associated death promoter phosphorylation at Ser112. However, meridianin C also suppressed PIM kinase expression and activity, and the panPIM kinase inhibitor AZD1208 only slightly suppressed the survival of MV411 cells. Thus, the antisurvival effect of compound 7a on MV411 cells was unrelated to PIM kinase inhibition. Moreover, compound 7a induced apoptosis, caspase9 and 3 activation and poly(ADPribose) polymerase (PARP) cleavage, but did not affect death receptor (DR)4 or DR5 expression in MV411 cells. Compound 7a also induced the generation of cleaved Bcl2, and the downregulation of myeloid cell leukemia (Mcl)1 and Xlinked inhibitor of apoptosis (XIAP) in MV411 cells. Furthermore, compound 7a increased eukaryotic initiation factor (eIF)2α phosphorylation and decreased S6 phosphorylation, whereas GRP78 expression was unaffected. Importantly, treatment with a pancaspase inhibitor (zVADfmk) significantly attenuated compound 7ainduced apoptosis, caspase9 and 3 activation, PARP cleavage, generation of cleaved Bcl2 and downregulation of Mcl1 and XIAP in MV411 cells. Collectively, these findings demonstrated the strong antisurvival and proapoptotic effects of compound 7a on MV411 cells through regulation of caspase9 and 3, Bcl2, Mcl1, XIAP, eIF2α and S6 molecules.
Subject(s)
Apoptosis Regulatory Proteins/metabolism , Apoptosis , Cell Proliferation , Indoles/chemistry , Indoles/pharmacology , Leukemia, Myeloid, Acute/drug therapy , Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins c-pim-1/antagonists & inhibitors , Pyrimidines/chemistry , Pyrimidines/pharmacology , Apoptosis Regulatory Proteins/genetics , Caspase 9/genetics , Caspase 9/metabolism , Endoplasmic Reticulum Chaperone BiP , Humans , Leukemia, Myeloid, Acute/metabolism , Leukemia, Myeloid, Acute/pathology , Phosphorylation , Protein Kinase Inhibitors/chemistry , Tumor Cells, Cultured , X-Linked Inhibitor of Apoptosis Protein/genetics , X-Linked Inhibitor of Apoptosis Protein/metabolismABSTRACT
Meridianin C is a marine natural product known for its anti-cancer activity. At present, the anti-tumour effects of meridianin C on oral squamous cell carcinoma are unknown. Here, we investigated the effect of meridianin C on the proliferation of four different human tongue cancer cells, YD-8, YD-10B, YD-38 and HSC-3. Among the cells tested, meridianin C most strongly reduced the growth of YD-10B cells; the most aggressive and tumorigenic of the cell lines tested. Strikingly, meridianin C induced a significant accumulation of macropinosomes in the YD-10B cells; confirmed by the microscopic and TEM analysis as well as the entry of FITC-dextran, which was sensitive to the macropinocytosis inhibitor amiloride. SEM data also revealed abundant long and thin membrane extensions that resemble lamellipodia on the surface of YD-10B cells treated with meridianin C, pointing out that meridianin C-induced macropinosomes was the result of macropinocytosis. In addition, meridianin C reduced cellular levels of Dickkopf-related protein-3 (DKK-3), a known negative regulator of macropinocytosis. A role for DKK-3 in regulating macropinocytosis in the YD-10B cells was confirmed by siRNA knockdown of endogenous DKK-3, which led to a partial accumulation of vacuoles and a reduction in cell proliferation, and by exogenous DKK-3 overexpression, which resulted in a considerable inhibition of the meridianin C-induced vacuole formation and decrease in cell survival. In summary, this is the first study reporting meridianin C has novel anti-proliferative effects via macropinocytosis in the highly tumorigenic YD-10B cell line and the effects are mediated in part through down-regulation of DKK-3.
Subject(s)
Down-Regulation/drug effects , Indole Alkaloids/pharmacology , Indoles/pharmacology , Intercellular Signaling Peptides and Proteins/metabolism , Pinocytosis/drug effects , Pyrimidines/pharmacology , Tongue Neoplasms/metabolism , Tongue Neoplasms/pathology , Adaptor Proteins, Signal Transducing , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Chemokines , Humans , Indole Alkaloids/chemistry , Indoles/chemistry , Pyrimidines/chemistry , Tongue Neoplasms/ultrastructure , Vacuoles/drug effects , Vacuoles/metabolismABSTRACT
Mongolia has a high incidence of brucellosis in human and animals due to livestock husbandry. To investigate the genetic characteristics of Mongolian B. melitensis, an MLVA (multi-locus variable-number tandem-repeat analysis)-16 assay was performed with 94 B. melitensis isolates. They were identified as B. melitensis biovar (bv.) 1 (67), 3 (10) and Rev. 1 vaccine strains (17) using a classical biotyping and multiplex PCR. In genotyping, three human isolates were grouped at 2 genotypes with sheep isolates, and it implies that B. melitensis are cross-infected between human and livestock. In the parsimony analysis, Mongolian B. melitensis isolates had high genetic similarity with Chinese strains, likely due to the geographical proximity, clustered distinctively as compared with other foreign isolates. B. melitensis Rev. 1 vaccine strains were divided into 4 genotypes with 92% similarity. In the analysis of Rev.1 strains, the risk of mutation of vaccine strain might not be overlooked. Animal quarantines should be strengthened to prevent the spread of Brucella species among adjacent countries.
