CXCR4 and B-cell acute lymphoblastic leukemia: More importantly, high CXCR4 cell surface expression is a common hallmark of malignant proliferation and invasion, and mediates the generation of drug resistance and disease progression in B-cell acute lymphoblastic leukemia (B-ALL) and T-cell lymphoblastic leukemia (T-ALL); in addition, targeting Notch/CXCR4 therapy may provide beneficial therapeutic effects for ALL patients.