CCKBR+ cancer cells contribute to the intertumor heterogeneity of gastric cancer and confer sensitivity to FOXO inhibition

Background: The presence of heterogeneity and poor diagnosis in gastric adenocarcinoma poses a significant challenge to cancer treatment. To address the limited therapeutic options and enhance complex clinical management, we investigated the effects of targeting FOXO to inhibit CCKBR+ cancer cells in vitro and in vivo. Methods: We conducted single-cell sequencing (scRNA-seq) analysis on malignant epithelial cells from five gastric adenocarcinoma patients, revealing the notable heterogeneity within gastric adenocarcinoma (GA). We identified the oncological features of CCKBR+ tumors through immunohistochemistry and clinical statistical analysis. To validate the biological similarity of CCKBR+ tumors, we performed single-cell sequencing on datasets GSE183904 and TCGA. The mutational hallmarks of CCKBR+ tumors were detected using OncoDriveFML and GISTIC 2.0. To further investigate the potential target of CCKBR+ tumors, we utilized organoids and tumor xenograft mouse models, assessing the impact of FOXO inhibition. Finally, we employed CUT&Tag and flow cytometry to determine the genes regulated by FOXO in CCKBR+ tumors. Results: We identified a subset of CCKBR+ stem cell-like cancer cells associated with poorly differentiated features and a worse prognosis in gastric adenocarcinoma. This finding was validated through additional single-cell RNA sequencing (scRNA-seq), TCGA analysis, and histopathology, underscoring the heterogeneity of GA. The unique propensity for gene mutations, such as TP53, APC, SMAD4, and GLI3, was observed in CCKBR+ tumors. Mechanistically, our investigation revealed that FOXOs serve as key transcription factors in maintaining the homeostasis of CCKBR+ tumors. Inhibition of FOXO was found to suppress the growth of CCKBR+ organoids and xenograft tumors. Notably, FOXOs were identified as regulators of α2,3 sialylation levels in CCKBR+ tumor cells, shedding light on a crucial aspect of their homeostasis. Conclusions: CCKBR+ tumor cells significantly contribute to the intertumor heterogeneity of gastric cancer, leading to lower differentiation potential and a poorer prognosis. FOXO plays a crucial role in maintaining the homeostasis of CCKBR+ tumors by upregulating sialylation levels mediated by ST3GAL3/4/5 and ST6GALNAC6. Targeting FOXO effectively suppresses the progression of CCKBR+ tumors. This insight opens new avenues for developing targeted therapeutic strategies aimed at treating cancers associated with CCKBR, providing a novel perspective for precision medicine in this context.