This observation, together with our data showing that CXCR4 signalling in turn regulates HIF-1α expression and transcriptional activity, corroborate the hypothesis of a reciprocal interaction between CXCL12/CXCR4 axis and HIF-1α in regulating the interactions between CLL cells and SC. Here, CXCL12 is linked to B-cell chronic lymphocytic leukemia.