Cytotoxicity Of Antigen Specific Chimeric Antigen Receptor Modified NK-92MI Cells Against HER2+ Breast Carcinoma Cells

Overexpression of HER2 in breast cancer cells is well known to be associated with high recurrence rate and poor outcome. Breast cancer patients with HER2 gene amplification and protein overexpression have an inferior prognosis manifested by shorter disease-free and overall survival. Chimeric antigen receptors modified T cells in which expression of chimeric antigen receptors on the surface of T cells result in the ability to overcome the tumor immune escape and the sustainable activity of T cells is currently the most popular cell therapy technique targeting tumors and reveals great therapeutic efficacy especially in the treatment of blood malignancies. However, due to its potential toxicity of on-target/off-tumor, the safety of its applications in the treatment with solid tumor, including breast cancer, becomes primary bottleneck. The first lethal side-effect was observed in a HER2 positive colon cancer patient who was treated with HER2-CAR-T cells, due to the attacking of HER2-CAR-T cells to HER2 positive normal lung tissue. In our research, CAR was expressed on NK-92 MI cells to improve therapeutic safety because NK cells do not produce interleukin-6(IL-6) and have shorter persistence capability in the body. Therefore, our study has made attempts to improve the safety of CAR in order to lay a foundation for the future clinical application.In order to confront with HER2+ breast carcinoma, HER2-CAR has been constructed by PCR, then the HER2-CAR fragment was cloned into a new generation of lentiviral vector. After recombinant lentivirus was prepared, NK-92 MI cells was transduced by HER2-CAR lentivirus. Then, we investigated whether the HER2 chimeric antigen receptor(HER2-CAR) modified NK-92 MI cells can improve the killing efficacy to HER2+ breast carcinoma cells, comparing to the non-genetically modified NK-92 MI cells. First, the HER2-CAR expression in the transduced NK-92 MI cells was detected by flow cytometry. Then, the variant secretion of IFN-? and Granzyme B between NK-92 MI and HER2-CAR-NK92 MI were detected. Finally, cytotoxicity assay was performed to examine whether the HER2-CAR-NK92 MI cells can kill breast carcinoma cells effectively. The results showed that HER2-CAR-NK92 MI cells could significantly kill HER2-positive breast carcinoma cells comparing with non-genetically modified NK-92 MI cells in vitro. We also observed moderate killing effect in vivo, which might be due to lower transduction efficiency of NK-92 MI cells by HER2-CAR. In conclusion, HER2-CAR-NK92 MI cells can improve cytotoxicity efficiency against HER2 positive tumor cells comparing with non-genetically modified NK-92 MI cells, suggesting the potential of HER2-CAR in breast carcinoma cells immunotherapy clinically.