The Killing Effect Of Trastuzumab Combined With NK Cells On Breast Cancer Cells In Vitro

Purpose: To study the cytotoxicity of NK cells combined with trastuzumab to breastcancer cells and to investigate the potential mechanisms. Meanwhile, we compared thekilling effect of NK cells from peripheral blood with NK-92MI cell line.Methods: Three breast cancer cell lines were chosen, HER2positive breast cancer celllines--BT-474, MDA-MB-453and HER2negative breast cancer cell line--MDA-MB-231.For each cell line, control group, trastuzumab group, NK cell group and combination groupwere set up, both primary NK cells and NK-92MI cells were included. The effects oftrastuzumab on proliferation of breast cancer cells, primary NK cells, NK-92MI cells werestudied by MTT assays. Calcein-AM release assays were performed to detect thecytotoxicity of primary NK cells or NK-92MI cells to breast cancer cells in the presence orabsence of trastuzumab. The secretion of IFN-γ and TNF-α by primary NK cells orNK-92MI cells were examined by ELISA assays. NKG2D ligands (ULBP1, ULBP2andMICA) on breast cancer cells were evaluated with flow cytometry.Results:1. The proliferation of HER2positive breast cancer cells could be inhibited bytrastuzumab, the inhibition rates were dose and time dependent. And the inhibition was moreobvious in HER2(+++) breast cancer cells. While trastuzumab had no effect on theproliferation of HER2negative breast cancer cells.2. Both primary NK cells and NK-92MIcells could kill breast cancer cells ex vivo. Primary NK cells showed higher killing.3. Asynergistic cytotoxicity of both primary NK cells and NK-92MI cells against HER2positivebreast cancer cells was observed when combined with trastuzumab. The synergy wasstronger in HER2(+++) breast cancer cells.4. Trastuzumab enhanced the secretion of IFN-γand TNF-α by primary NK cells or NK-92MI cells. Trastuzumab with NK cells up-regulatedthe expression of NKG2D ligands (ULBP1, ULBP2and MICA) on HER2positive breastcancer cells.Conclusion: The inhibition of trastuzumab to HER2positive breast cancer cells was observed. The synergistic antitumor effect achieved when using primary NK cells orNK-92MI cells in combination with trastuzumab against HER2positive breast cancer cells.The increased secretion of IFN-γ, TNF-α by NK cells and up-regulated expression ofNKG2D ligands (ULBP1, ULBP2, MICA) on HER2positive breast cancer cells might bethe reasons. Therefore combination of trastuzumab with NK cells would be a rational andpromising method for HER2positive breast cancer patients.