Integrin a6 mediates the drug resistance of acute lymphoblastic B-cell leukemia

Resistance to multimodal chemotherapy continues to limit the prognosis of acute lymphoblastic leukemia (ALL). This occurs in part through a process called adhesion-mediated drug resistance, which depends on ALL cell adhesion to the stroma through adhesion molecules, including integrins. Integrin a6 has been implicated in minimal residual disease in ALL and in the migration of ALL cells to the central nervous system. However, it has not been evaluated in the context of chemotherapeutic resistance. Here, we show that the anti-human a6-blocking Ab P5G10 induces apoptosis in primary ALL cells in vitro and sensitizes primary ALL cells to chemotherapy or tyrosine kinase inhibition in vitro and in vivo. We further analyzed the underlying mechanism of a6-associated apoptosis using a conditional knockout model of a6 inmurine BCRABL11 B-cell ALL cells and showed that a6-deficient ALL cells underwent apoptosis. In vivo deletion of a6 in combination with tyrosine kinase inhibitor (TKI) treatment wasmore effective in eradicating ALL than treatment with a TKI (nilotinib) alone. Proteomic analysis revealed that a6 deletion in murine ALL was associated with changes in Src signaling, including the upregulation of phosphorylated Lyn (pTyr507) and Fyn (pTyr530). Thus, our data support a6 as a novel therapeutic target for ALL. (Blood. 2020;136(2):210-223).