The anti-B7-H4 checkpoint synergizes trastuzumab treatment to promote phagocytosis and eradicate breast cancer.

Trastuzumab is a humanized mAb used to treat HER2-overexpressing breast cancer; however its mechanisms remain to be fully elucidated. Previous studies suggest a role for immunity in mediating trastuzumab-specific antitumor effects. This study evaluated the role(s) of trastuzumab and other antibodies on macrophage activation and Ab-dependent cell-mediated phagocytosis (ADCP) of HER2+ breast cancer cells in vitro and in vivo. We employed orthotopic implantation of HER2+ murine breast cancer (BC) cells in immunocompetent mouse models, a human HER2+ BC xenograft in an immune humanized mouse model, and human PDXs involving adoptive transfer of autologous macrophages to simulate an endogenous mammary tumor-immune microenvironment. Our study demonstrated that trastuzumab greatly and consistently increased macrophage frequency and tumor-cell phagocytosis, and that concurrent knockdown of B7-H4 by a neutralizing antibody increased immune cell infiltration and promoted an antitumor phenotype. Furthermore, neoadjuvant trastuzumab therapy significantly upregulated B7-H4 in the cancer-infiltrating macrophages of HER2+ BC patients, which predicted poor trastuzumab response. We suggest that strategies to specifically enhance ADCP activity might be critical to overcoming resistance to HER2 mAb therapies by inhibiting tumor growth and potentially enhance antigen presentation. Furthermore, these results advance the understanding of macrophage plasticity by uncovering a dual role for ADCP in macrophages involving elimination of tumors by engulfing cancer cells while causing a concomitant undesired effect by upregulating immunosuppressive checkpoints.

Hu X ，Liu Y ，Zhang X ，Kong D ，Kong J ，Zhao D ，Guo Y ，Sun L ，Chu L ，Liu S ，Hou X ，Ren F ，Zhao Y ，Lu C ，Zhai D ，Yuan X ... -  《NEOPLASIA》

CD47 blockade augmentation of trastuzumab antitumor efficacy dependent on antibody-dependent cellular phagocytosis.

Tsao LC ，Crosby EJ ，Trotter TN ，Agarwal P ，Hwang BJ ，Acharya C ，Shuptrine CW ，Wang T ，Wei J ，Yang X ，Lei G ，Liu CX ，Rabiola CA ，Chodosh LA ，Muller WJ ，Lyerly HK ，Hartman ZC ... -  《JCI Insight》

Development and evaluation of a human CD47/HER2 bispecific antibody for Trastuzumab-resistant breast cancer immunotherapy.

The treatment for trastuzumab-resistant breast cancer (BC) remains a challenge in clinical settings. It was known that CD47 is preferentially upregulated in HER2+ BC cells, which is correlated with drug resistance to trastuzumab. Here, we developed a novel anti-CD47/HER2 bispecific antibody (BsAb) against trastuzumab-resistant BC, named IMM2902. IMM2902 demonstrated high binding affinity, blocking activity, antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), and internalization degradation effects against both trastuzumab-sensitive and trastuzumab-resistant BC cells in vitro. The in vivo experimental data indicated that IMM2902 was more effective than their respective controls in inhibiting tumor growth in a trastuzumab-sensitive BT474 mouse model, a trastuzumab-resistant HCC1954 mouse model, two trastuzumab-resistant patient-derived xenograft (PDX) mouse models and a cord blood (CB)-humanized HCC1954 mouse model. Through spatial transcriptome assays, multiplex immunofluorescence (mIFC) and in vitro assays, our findings provided evidence that IMM2902 effectively stimulates macrophages to generate C-X-C motif chemokine ligand (CXCL) 9 and CXCL10, thereby facilitating the recruitment of T cells and NK cells to the tumor site. Moreover, IMM2902 demonstrated a high safety profile regarding anemia and non-specific cytokines release. Collectively, our results highlighted a novel therapeutic approach for the treatment of HER2+ BCs and this approach exhibits significant anti-tumor efficacy without causing off-target toxicity in trastuzumab-resistant BC cells.

Zhang B ，Shi J ，Shi X ，Xu X ，Gao L ，Li S ，Liu M ，Gao M ，Jin S ，Zhou J ，Fan D ，Wang F ，Ji Z ，Bian Z ，Song Y ，Tian W ，Zheng Y ，Xu L ，Li W ... -  《-》

Anti-HER2 induced myeloid cell alterations correspond with increasing vascular maturation in a murine model of HER2+ breast cancer.

Bloom MJ ，Jarrett AM ，Triplett TA ，Syed AK ，Davis T ，Yankeelov TE ，Sorace AG ... -  《BMC CANCER》

Histone deacetylase inhibitors valproic acid and vorinostat enhance trastuzumab-mediated antibody-dependent cell-mediated phagocytosis.

The monoclonal antibody (mAb) trastuzumab is part of the standard of care for patients with human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer. Antibody-dependent cell-mediated phagocytosis (ADCP) and cytotoxicity (ADCC) are major mechanisms of action of the mAb trastuzumab. Histone deacetylase inhibitors (HDACi), such as valproic acid (VPA) or vorinostat (SAHA), exert several immunostimulatory properties, which contribute at least in part to their anticancer effect. However, the impact of HDACi-induced immunostimulatory effects on trastuzumab-mediated anti-tumor immune response is not well characterized. We analyzed the ADCP and ADCC activity of peripheral blood mononuclear cells (PBMCs) from age and gender-matched healthy volunteers (n=5) against HDACi-treated HER2-overexpressing breast cancer cells (SKBR3), using a well-established in vitro three-color imaging flow cytometry and flow cytometry approach. VPA and SAHA enhanced trastuzumab-mediated ADCP and trastuzumab-independent cytotoxicity. Mechanistically, VPA upregulated the activating antibody-binding receptor Fc-gamma receptor (FcγR) IIA (CD32A) on monocytes (CD14+). Moreover, VPA and SAHA downregulated the anti-apoptotic protein myeloid leukemia cell differentiation 1 (MCL1) in breast cancer cells. Additionally, VPA and SAHA induced an immunogenic cell death, characterized by the exposure of calreticulin (CALR), as well as decreased the "do not eat me" signal CD47 on tumor cells. HDACi VPA and SAHA increase trastuzumab-mediated phagocytosis and trastuzumab-independent cytotoxicity. The immunomodulatory activities of those HDACi support a rationale combined treatment approach with mAb for cancer treatment.

Laengle J ，Kabiljo J ，Hunter L ，Homola J ，Prodinger S ，Egger G ，Bergmann M ... -  《Journal for ImmunoTherapy of Cancer》