COL4A1 and cancer: At the same time, multiple collagen-related genes (COL6A2, COL3A1, COL4A1, and COL4A2) in the MSC-2 cluster were upregulated in bone metastases, which is consistent with our observation of IGFBP3, TAGLN, LUM, COL6A1, COL6A2, and COL3A1 in pan-cancer in Fig. (1d).