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886 Combined allogeneic NK cell and Herzuma® is effective in HER2-low breast cancer preclinical model by enhancing antibody-dependent cellular cytotoxicity
  1. Yong Moon1,
  2. Mithun Gosh2,
  3. Hee-Jung An1,
  4. Tae Hoen Kim1,
  5. Sa Deok Hong2,
  6. Nar Bahadur Katuwal2 and
  7. Minsil Kang1
  1. 1CHA Bundang Medical Center, Seongnam, Republic of Korea
  2. 2The Graduate School, CHA University, Seongnam, Republic of Korea


Background Trastzumab has shown significant improvements in the overall survival in patients with HER2-positive breast cancer. But HER2 is expressed at varying levels in breast cancer patients, therefore, only a fraction with robust HER2 overexpression is beneficial from trastzumab therapy. However, the efficacy of trastzumab in HER2-low expressing breast cancer, which is defined as immunohistochemistry 1+ or 2+ and lack of HER2 amplification by in situ hybridization, is not reported yet. Therefore, to enhance the effects of trastzumab in HER2-low expressing breast cancers, we investigated a novel combination of Herzuma® (a trastzumab biosimilar), paclitaxel and allogeneic Natural Killer (NK) cells in the HER2-low breast cancer preclinical models.

Methods Two breast cancer cell lines, BT-474 (HER2-low, by western blot) and SKBR3 (HER2-high, by western blot) were used for in-vitro study. Cytotoxicity was analyzed by flow cytometry (CFSE, 7AAD) after co-culture, where cancer cells were used as target (T) cell and allogeneic NK cells as effector (E) cell at various E:T ratio in the presence or absence of Herzuma®. Antibody-dependent cellular cytotoxicity (ADCC) activity was analyzed by evaluating interaction of Herzuma® and FCϒIII (CD16) of NK cells. Lastly, HER2-low breast cancer patients-derived tumor xenograft (PDTX) model was used for in vivo efficacy test. When tumor size reached to 100mm3, mice were randomly divided in 4 groups (control, Herzuma® + paclitaxel, NK, Herzuma® + paclitaxel + NK) and treated.

Results Cytotoxicity assay demonstrated that dead target cells were only increased in the combined Herzuma® and NK therapy as compared to NK monotherapy in both cell lines (BT474, SKBR3) at various E:T ratio. To confirm the above-mentioned cytotoxic effect of the combination therapy is an ADCC effect, we conducted co-culture using HER2-low BT474 cells after blocking the CD16 of NK cells. Dead target cells were not increased in the combined Herzuma® and NK therapy group after CD16 blocking, whereas similar cytotoxic effects were observed in NK monotherapy and combination therapy respectively, suggesting the above-mentioned cytotoxic effect resulted from ADCC. Finally, the in-vivo study using HER2-low breast cancer PDTX model showed that the NK therapy in combination with Herzuma® and paclitaxel group significantly inhibited the tumor growth as compared to combined Herzuma® and paclitaxel group or control (p=0.003, vs control; p=0.01, vs Herzuma® + paclitaxel).

Conclusions The combination of allogeneic NK therapy, Herzuma® and paclitaxel showed synergistic anticancer activity in HER2-low breast cancer preclinical model. This combination merits further clinical investigation in HER2-low breast cancer patients.

Acknowledgements The study was funded by CELLTRION PHARM, Inc. (Chungcheongbuk-do, Republic of Korea)

Ethics Approval IACUC190139

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