Notably, the expression of SPP1, associated with chemotherapy resistance in various cancer types (48) and poor response to cisplatin-based chemotherapy in muscle-invasive bladder cancer (MIBC) (49), was significantly elevated in UTUC tissues-derived M1 macrophages compared to normal ureter samples, shedding light on the underlying mechanism between UTUC chemotherapy resistance and M1 macrophages. This evidence concerns the gene SPP1 and cancer.