SPP1 and cancer: Also, breast CAF‐secreted CXCL12 was shown to promote the growth of xenograft tumors formed by patient‐derived CAFs and cancer cells [3] and osteopontin‐activated fibroblast‐derived CXCL12 was proposed to play a role in inducing epithelial‐mesenchymal‐transition and angiogenesis using in vitro assays [7].