Anti­survival and pro­apoptotic effects of meridianin C derivatives on MV4­11 human acute myeloid leukemia cells.

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.

Meridianin C inhibits the growth of YD-10B human tongue cancer cells through macropinocytosis and the down-regulation of Dickkopf-related protein-3.

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.

Molecular epidemiological investigation of Brucella melitensis circulating in Mongolia by MLVA16.

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.