MUCL1 and neoplasm: Intriguingly, tumor in state 1 exhibited an activation of immune-related signatures (IGLC2, IGHG4, IGHG1 and IGKC; Fig. 3E, Additional file 4: Fig. S4), while the tumor cells in state 3 which were mostly contributed by HER2low cells possessed the characteristics of metabolic biological function with the highly expression of PTN, SCGB2A2, MUCL1, PIP, etc. (Fig. 3E, Additional file 4: Fig. S4).