CXCR4 and pituitary gland adenoma: Moreover, interactions between CSCs and tumor microenvironment through secreted CKs (e.g., CXCL12) [13], possibly occurring also in pituitary adenomas, may act as chemoattractant to recruit fibroblasts, endothelial, mesenchymal, and inflammatory cells to the tumor, via CXCR4.