MMP9 and acute lymphoblastic leukemia: In these assays, inhibition of Notch1 signalling attenuated the up-regulation of MMP2 and MMP9 observed during hypoxia (Figure 6), and higher invasiveness was also abrogated, providing additional evidence that hypoxia/HIF-1α-induced MMP2/9 up-regulation in T-ALL cells requires Notch1 signalling.