Human endogenous retroviral syncytin exerts inhibitory effect on invasive phenotype of B16F10 melanoma cells

Objective; Fusogenic endogenous retroviral syncytin plays an important role in the formation of syncytiotrophoblasts in human placenta.Apart from its expression in placenta,brain and testis,syncytin has also been found in many cancers.Although syncytin has been proposed to serve as a positive prognostic marker in some cancers,the underlying mechanism is unclear.The aim of this study is to evaluate the effects of syncytin expression on the invasive phenotype of melanoma cells.Methods：The eukaryotic expression plasmid for syncytin-EGFP was constructed and transfected into B16F10 melanoma cells.The effect of syncytin on the invasion potential of rumor cells was evaluated in B16F10 subline cells that stably expressed syncytin-EGFP fusion protein or EGFP alone.Results：The B16F10 sublines that stably expressed syncytin-EGFP or EGFP alone were established respectively and confirmed by immunofluorescent and immtmoblotting assay.Syncytin expression in B16F10 cells was associated with decreased cell proliferation,migration and invasion.Multinucleated giant cells that contained as many as five nuclei were induced in syncytin-expressing cells.In addition,syncytin expression did not alter the sensitivity of B16F10 cells to trichosanthin,a toxin that damages syncytiotrophoblasts more efficiently than other tissues.Conclusions：These results suggest that syncytin expression in some cancers may confine their invasion potential and thus serve as a positive prognostic factor.

Scutellarin inhibits caspase-11 activation and pyroptosis in macrophages via regulating PKA signaling

Inflammatory caspase-11 senses and is activated by intracellular lipopolysaccharide(LPS)leading to pyroptosis that has critical role in defensing against bacterial infection,whereas its excess activation under pathogenic circumstances may cause various inflammatory diseases.However,there are few known drugs that can control caspase-11 activation.We report here that scutellarin,a flavonoid from Erigeron breviscapus,acted as an inhibitor for caspase-11 activation in macrophages.Scutellarin dosedependently inhibited intracellular LPS-induced release of caspase-11 p26(indicative of caspase-11 activation)and generation of N-terminal fragment of gasdermin D(GSDMD-NT),leading to reduced pyroptosis.It also suppressed the activation of non-canonical nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3(NLRP3)inflammasome as evidenced by reduced apoptosisassociated speck-like protein containing a CARD(ASC)speck formation and decreased interleukin-1 beta(IL-1 b)and caspase-1 p10 secretion,whereas the NLRP3-specific inhibitor MCC950 only inhibited IL-1 b and caspase-1 p10 release and ASC speck formation but not pyroptosis.Scutellarin also suppressed LPS-induced caspase-11 activation and pyroptosis in RAW 264.7 cells lacking ASC expression.Moreover,scutellarin treatment increased Ser/Thr phosphorylation of caspase-11 at protein kinase A(PKA)-specific sites,and its inhibitory action on caspase-11 activation was largely abrogated by PKAinhibitor H89 or by adenylyl cyclase inhibitor MDL12330 A.Collectively,our data indicate that scutellarin inhibited caspase-11 activation and pyroptosis in macrophages at least partly via regulating the PKA signaling pathway.

Construction of Soluble Mamu-B~*1703,a Class I Major Histocompatibility Complex of Chinese Rhesus Macaques,Monomer and Tetramer Loaded with a Simian Immunodeficiency Virus Peptide

Chinese-descent rhesus macaques have become more prevalent for HIV infection and vaccine investigation than Indian-origin macaques. Most of the currently available data and reagents such as major histocompatibility complex （MHC） class I tetramers, however, were derived from Indian-origin macaques due to the dominant use of these animals in history. Although there are significant differences in the immunogenetic background between the two macaque populations, they share a few of common MHC class I alleles. We reported in this study the procedure for preparation of a soluble Mamu-B＊1703 （a MHC class I molecule of Chinese macaques） monomer and tetramer loaded with a dominant simian immunodeficiency virus （SIV） epitope IW9 （IRYPKTFGW） that was identified to be Mamu-B＊1701-restricted in Indian macaques. The DNA fragment encoding the Mamu-B＊1703 extracellular domain fused with a BirA substrate peptide （BSP） was amplified from a previously cloned cDNA and inserted into a prokaratic expression vector. In the presence of the antigenic peptide IW9 and light chain β2-microglobulin, the expressed heavy chain was refolded into a soluble monomer. After biotinylation, four monomers were polymerized as a tetramer by phycoerythrin-conjugated streptavidin. The tetramer, having been confirmed to have the right conformation, was a potential tool for investigation of antigen-specific CD8^＋ T-lymphocytes in SIV vaccine models of Chinese macaques. And our results also suggested that some antigenic peptides reported in Indian-origin macaques could be directly recruited as ligands for construction of Chinese macaque MHC tetramers.