MRC1 and nonpapillary renal cell carcinoma: THP-1 was initially converted into M0 macrophages using PMA, and then co-cultured with ccRCC cell lines Caki-1 and ACHN to produce M2 macrophages, which were detected by flow cytometry (Fig. 2A, B), and CD206 positive rates increased substantially, demonstrating that macrophages and ccRCC cell lines may differentiate into M2 macrophages when co-cultured.