MMP9 and T-cell acute lymphoblastic leukemia: In patients with T-cell acute lymphoblastic leukemia (T-ALL), HIF-1α is overexpressed, and HIF-1α can promote the activation of Notch1 signaling, increase the expression of cyclin D1, CDK2, p21, MMP2, and MMP9 proteins, thereby leading to cell proliferation, invasion, and resistance [86,87].