Glutamine metabolic microenvironment drives M2 macrophage polarization to mediate trastuzumab resistance in HER2‐positive gastric cancer

BACKGROUND: Trastuzumab is a first‐line targeted therapy for human epidermal growth factor receptor‐2 (HER2)‐positive gastric cancer. However, the inevitable occurrence of acquired trastuzumab resistance limits the drug benefit, and there is currently no effective reversal measure. Existing researches on the mechanism of trastuzumab resistance mainly focused on tumor cells themselves, while the understanding of the mechanisms of environment‐mediated drug resistance is relatively lacking. This study aimed to further explore the mechanisms of trastuzumab resistance to identify strategies to promote survival in these patients. METHODS: Trastuzumab‐sensitive and trastuzumab‐resistant HER2‐positive tumor tissues and cells were collected for transcriptome sequencing. Bioinformatics were used to analyze cell subtypes, metabolic pathways, and molecular signaling pathways. Changes in microenvironmental indicators (such as macrophage, angiogenesis, and metabolism) were verified by immunofluorescence (IF) and immunohistochemical (IHC) analyses. Finally, a multi‐scale agent‐based model (ABM) was constructed. The effects of combination treatment were further validated in nude mice to verify these effects predicted by the ABM. RESULTS: Based on transcriptome sequencing, molecular biology, and in vivo experiments, we found that the level of glutamine metabolism in trastuzumab‐resistant HER2‐positive cells was increased, and glutaminase 1 (GLS1) was significantly overexpressed. Meanwhile, tumor‐derived GLS1 microvesicles drove M2 macrophage polarization. Furthermore, angiogenesis promoted trastuzumab resistance. IHC showed high glutamine metabolism, M2 macrophage polarization, and angiogenesis in trastuzumab‐resistant HER2‐positive tumor tissues from patients and nude mice. Mechanistically, the cell division cycle 42 (CDC42) promoted GLS1 expression in tumor cells by activating nuclear factor kappa‐B (NF‐κB) p65 and drove GLS1 microvesicle secretion through IQ motif‐containing GTPase‐activating protein 1 (IQGAP1). Based on the ABM and in vivo experiments, we confirmed that the combination of anti‐glutamine metabolism, anti‐angiogenesis, and pro‐M1 polarization therapy had the best effect in reversing trastuzumab resistance in HER2‐positive gastric cancer. CONCLUSIONS: This study revealed that tumor cells secrete GLS1 microvesicles via CDC42 to promote glutamine metabolism, M2 macrophage polarization, and pro‐angiogenic function of macrophages, leading to acquired trastuzumab resistance in HER2‐positive gastric cancer. A combination of anti‐glutamine metabolism, anti‐angiogenesis, and pro‐M1 polarization therapy may provide a new insight into reversing trastuzumab resistance.