Fullerenols boosting the therapeutic effect of anti-CD47 antibody to trigger robust anti-tumor immunity by inducing calreticulin exposure

Phagocyte-mediated programmed cell removal (PrCR) plays an important role in the immunosurveillance and elimination of cancer cells. The induction of PrCR is elevated by exposed calreticulin (CRT) on cell surface as a "eat me" signal, and countered by "don't eat me" signal, CD47. Thus, well-tolerated CRT exposure inducers are benefit for the outcome of anti-CD47 therapy. Herein, fullerenol nanoparticle (fNP) with special surface property is found to trigger CRT exposure in 7 out of 12 human cancer cell lines by inducing basal ER stress without the occurrence of immunogenic cell death. Increased CRT exposure by fNP elicits efficient PrCR, which is further enhanced by the combination of fNP and anti-CD47 mAb in vivo. Moreover, the combined therapy shows significantly increased anti-tumor efficiency compared with anti-CD47 mAb alone in both U87MG subcutaneous glioblastoma model and 143B orthotopic osteosarcoma model. Even in combination with half dose of anti-CD47 mAbs shows a similar anti-tumor efficiency with full-dose anti-CD47 mAbs alone, suggesting the role of fNP in reducing the amount of anti-CD47 mAbs. Moreover, the combination treatment promotes M2-to-M1 repolarization of macrophage within the tumor microenvironment. These findings validate our strategy as an effective platform for combining fNP with anti-CD47 therapy. (C) 2020 Elsevier Ltd. All rights reserved.