The tumor growth inhibition (TGI) measured on day 56 confirmed the potentiation of trastuzumab antitumor activity when co-injected with pegfilgrastim. Co-treatment with pegfilgrastim and trastuzumab significantly decreased A549 growth when compared to untreated, trastuzumab alone and filgrastim plus trastuzumab groups according to one way ANOVA (p<0,001). In this experiment three mice were used for each group.
ARTICLE ABSTRACTTherapeutic mAbs exert antitumor activity through various mechanisms, including apoptotic signalization, complement-dependent cytotoxicity, and antibody-dependent cellular cytotoxicity (ADCC) or phagocytosis (ADCP). G-CSF and GM-CSF have been reported to increase the activity of antibodies in preclinical models and in clinical trials. To determine the potential role of pegfilgrastim as an enhancer of anticancer antibodies, we performed a comparative study of filgrastim and pegfilgrastim. We found that pegfilgrastim was significantly more potent than filgrastim in murine xenograft models treated with mAbs. This was observed with rituximab in CD20+ models and with trastuzumab in HER2+ models. Stimulation with pegfilgrastim was associated with significant enhancement of leukocyte content in spleen as well as mobilization of activated monocytes/granulocytes from the spleen to the tumor bed. These results suggest that pegfilgrastim could constitute a potent adjuvant for immunotherapy with mAbs possessing ADCC/ADCP properties. Mol Cancer Ther; 15(6); 1238–47. ©2016 AACR.