Adhesion of MCL cells to stromal cells in the tumor microenvironment activates the PI3K pathway, which transmits signals from cell membrane receptors, such as the B-cell receptor and CXCR4 (chemokine receptor), to the nucleus, leading to transcriptional regulation of genes involved in migration, proliferation and survival [45,127,132,133]. The gene discussed is CXCR4; the disease is mantle cell lymphoma.