Integrin α6 Mediates 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 alpha6 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 alpha6-blocking antibody P5G10 induces apoptosis in primary ALL 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 alpha6-associated apoptosis using a conditional knockout model of alpha6 in murine BCR-ABL1+ B-ALL cells and showed that alpha6-deficient ALL cells underwent apoptosis. In vivo deletion of alpha6 in combination with tyrosine kinase inhibitor (TKI) treatment was more effective in eradicating ALL than treatment with a TKI (nilotinib) alone. Proteomic analysis revealed that alpha6 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 alpha6 as a novel therapeutic target for ALL.