MYC and acute lymphoblastic leukemia: Growth arrest‐specific (GAS2) interacts with C‐X‐C motif chemokine receptor 4 (CXCR4) and enhances the stability of CXCR4 in T‐cell acute lymphoblastic leukemia (T‐ALL) cells, and the GAS2/CXCR4 axis activates the expression of NOTCH/c‐MYC and promotes T‐cell leukemogenesis.