CXCL12 and neoplasm: Using RNA hybridization technique, we confirmed that fibroblasts are a critical source of CXCL12 and that fibroblast specific deletion of CXCL12 abrogates CXCL12 protein expression in the TME suggesting that stromal fibroblasts-secreted chemokine CXCL12 shapes the TME in favor of tumor growth and metastases.