Antisense expression of PKCα improved sensitivity of SGC7901/VCR cells to doxorubicin

AIM:To explore whether antisense blocking of protein kinase C alpha(PKCα)would reverse multi-drug resistance(MDR)in the vincristine(VCR)-resistant human gastric cancer cell line SGC7901/VCR. METHODS:SGC7901/VCR cells expressing antisense PKCα,SGC7901/VCR/aPKC,were established by transfection with a recombinant plasmid reversely inserted with PKCαcDNA.Empty vector(PCI-neo)transfected cell clones,SGC7901/VCR/neo,served as the control.Western blot method was used to detect PKCαcontent in SGC7901,SGC7901/VCR,SGC7901/ VCR/neo and SGC7901/VCR/aPKC cells,using PKCα-specific antibody.The sensitivity of SGC7901,SGC7901/ VCR,SGC7901/VCR/neo and SGC7901/VCR/aPKC cells to doxorubicin(DOX)in vitro was determined by MTT assay.The uptake of DOX in these cells was detected with fluorescence spectrophotometer.RESULTS:Western blot analysis showed that the PKCαprotein level was about 8.7-fold higher in SGC7901/ VCR cells than that in SGC7901 cells,whereas the protein expression of PKCαwas reduced by 78%in SGC7901/VCR/aPKC cells when compared with the SGC7901/VCR cells.SGC7901/VCR/aPKC cells had a 4.2-fold increase in DOX cytotoxicity,accompanied by a 1.7-fold increase of DOX accumulation in comparison with SGC7901/VCR cells. CONCLUSION:PKCαpositively regulates MDR in SGC7901 cells,and inhibition of PKCαcan partially attenuate MDR in human gastric cancer cells.

Microstructure and corrosion behaviors of friction stir-welded Q235 low-carbon steel joint

Friction stir welding(FSW)was used to prepare Q235 low-carbon steel joint,and the microstructure of different zones of the joint was characterized.The electrochemical corrosion behavior of different macroscopic zones of the joint was evaluated in 3.5 wt.%NaCl solution.The results showed that the retreated-side heat-affected zone(HAZRS)and the advanced-side heat-affected zone(HAZAS)did not undergo phase transformation during FSW,and their microstructures were similar to those of the base material(BM),which was mainly composed of blocky ferrite and pearlite.The retreated-side thermo-mechanical affected zone(TMAZRS),the stirring zone(SZ),and the advanced-side thermo-mechanical affected zone(TMAZAS)underwent phase transformation,and the microstructure was mainly composed of proeutectoid ferrite and pearlite.The order of the corrosion resistance of different micro-zones from high to low was:HAZRS>BM>HAZAS>TMAZRS>SZ>TMAZAS.The corrosion mechanism for BM,HAZRS,and HAZAS was mainly the dissolution of ferrite.By contrast,the corrosion mechanism for TMAZRS,SZ,and TMAZAS was mainly galvanic corrosion between proeutectoid ferrite and pearlite.