Effect Of NK Cells Plus Cetuximab Treatment On Colon Cancer Cells In Vitro

Objectives: To investigate inhibitory effect of NK cells and combiniton effect of NKcells with cetuximab on three colon cancer cells (LoVo、SW480、SW620) in vitro.Toexplore the antibody dependent cell cytotoxicity(ADCC) mechanisms underlyingcetuximab’s inhibitory effect on colon cancer cells. To make use of the FcγRIII ofNK cell and (epidermal growth factor receptor）EGFR of tumor cell,we may providethe experimental data for cetuximab combined with NK cell cell for biologicaltreatment plan.Methods:We check EGFR expression levels of three different colon cancer cells(LoVo, SW480, SW620) by immunohistochemistry,flow cytometry,then six differentconcentrations of cetuximab (5μg/ml、10μg/ml、20μg/ml、50μg/ml、100μg/ml、200μg/ml)was applied to these tumor cells, the inhibition rates were detected byMTT assay after24、48and72hours;Human NK were cultured from Peripheral bloodmononuclear cell(PBMC),and then we used three different groups for these threecells,NK cells,cetuximab,NK cells and cetuximab combined,ADCC activity wereassessed by LDH assay.Results: Imunohistochemistry showed the EGFR expression of three cell lines: LoVo(+++), SW480(+), SW620(-); flow cytometry analysis showed the EGFR expressionof three cell lines (the EGFR expression level were shown by mean fluorescenceintensity MFI):LoVo MFI55.33±2.78，SW480MFI26.26±2.24，SW620MFI0.97±0.10.The inhibition rates and cetuximab concentration on LoVo cells and SW480cells was positively correlated,while the inhibition rates and cetuximab concentrationon SW620cells was no correlated;all of three colon cells, the inhibition rates andeffector-target ratio (NK cells-colon cells)was positively correlated;The combined useof cetuximab and NK cells showed a synergistic inhibitory effect on LoVo cells and SW480cells,but the combined use of cetuximab and NK cells showed a additiveinhibitory effect on SW620cells.Conclusions:1.Cetuximab could inhibit EGFR positive the LoVo cell lines andSW480cell lines, the inhibition rates on LoVo cells and SW480cells was positivelycorrelated while the inhibition rates on EGFR-negative SW620cell lines waslittle,the inhibition rates on SW620cells was no correlated.2.The combined use ofcetuximab and NK cells showed a synergistic inhibitory effect on LoVo cells andSW480cells which was related to the ADCC activity of NK cells.3.NK-mediatedADCC was affect by surface EGFR expression levels of the colon cells, the highEGFR expression in colon cells the more sensitive to the NK-mediated ADCC.