| Objective:To investigate anti-proliferation and apoptosis effects of histonedeacetylase inhibitor NaB on human small cell lung cancer cell lines H446 and study theinhibitory effect on human small cell lung cancer in nude mice and explore the mechanism.Methods:①The small cell lung cancer H446 cells were treated with variousconcentrations of NaB in different duration in vitro.Cell viability was analyzed by MTTassay.Apoptosis rate and cell cycle were analysed by flow cytometry (FCM) .Theexpression of p21WAFl mRNA was detected by semi-quantitative RT-PCR;②Humansmall cell lung cancer H446 was seeded in the subcutaneous layer of 12 nude mice tobuilt small cell lung cancer xenograft model.Then they were randomly and equallydivided into 2 groups.NaB was given in experimental group while phosphatic-bufferedsaline (PBS) was used in control group for 4 weeks.Tumor size and body weight of themice were measured at regular time-intervals.The specimens taken from the tumors wereexamined by light microscope and electronic microscopy,and were analyzed by themethod of terminal deoxynucleotidyl transferase mediated dUTP nick end labeling(TUNED .The heart,liver,lung and kidney sections were examined after HE staining forassessment of toxicity.Results:①MTT assay showed that the percentage of growth inhibiting cells treatedwith 2.5,5,10,20mmol/L NaB for 24hrs were 11.3%,14.5%,20.0%,22.5% and for48hrs were 14.5%,19.7%,28.2%,33.3%,and for 72hrs were 20.6%,27.2%,38.2%,45.4%.The results showed that NaB inhibited the proliferation of H446 cells indose-dependent and time-dependent manners;②Annexin V/PI assay showed that thepercentage of apoptosiss cells treated with 5mmol/L,10mmol/L NaB for 24hrs were (19.5±2.7)%,(25.6±2.1)% and for 48hrs were (26.2±1.8)%,(39.8±2.6)%.Comparedwith the control group which were 24h(5.3±1.6)% and 48hrs(9.1±2.0)%,the differenceswere significant(P<0.01 );③After H446 cell lines exposed to 10mmol/L NaB for 24hrs and48hrs,GO/Gl-phase content increased from (50.2±2.2) % to (70.6±1.8) % and (87.2±3.4)%.And S-phase content decreased from (31.7±2.8) % to (20.2±1.4) % and (7.3±1.6)%.And G2/M-phase content decreased from (18.1±1.5) % to (9.2±1.3) % and (5.5±0.9)%.The results showed that NaB could arrest H446 cells in GO/Gl phase;④RT-PCR resultsrevealed that the expression of p21WAF1 mRNA was upregulated in the H446 cellstreated with NaB for 12 hrs,as was remarkable particularly for 24 hrs;⑤The averageweight of transplant tumor of NaB-treated group was 753.4mg,significantly lower thanthat of the control group which was 1403.5mg (P<0.01) .Inhibitory rates of NaB againstxenograft tumor was 46.25%;⑥TUNEL assay showed positive cells in NaB-treated groupincreased significantly,scattered distribution.The apoptotic index was higher inNaB-treated group (3.62±0.54)%than in control group (20.47±1.68)%(P<0.01).Therewere no toxic reactions during treatment and all the nude mice grew in a good condition.Conclusions:①NaB can inhibit the proliferation of human small cell lung cancerH446 cells and induce apoptosis in a time and dos-dependent manner,which wereassociated with upregulation of the expression of p21 WAF1mRNA as well as arrest of theH446 cells in GO/Gl phase.②NaB can significantly inhibit the growth of human smallcell lung cancer xenograft in nude mice.Its mechanism may be related to inducingapoptosis in tumor cells.
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