Integrin signaling is critical for myeloid-mediated support of T-cell acute lymphoblastic leukemia

We previously found that T-cell acute lymphoblastic leukemia (T-ALL) requires support from tumor-associated myeloid cells, which activate IGF1R signaling in the leukemic blasts. However, IGF1 is not sufficient to sustain T-ALL survival in vitro, implicating additional myeloid-mediated signals in T-ALL progression. Here, we find that T-ALL cells require close contact with myeloid cells to survive. Transcriptional profiling and in vitro assays demonstrate that integrin-mediated cell adhesion and activation of the downstream FAK/PYK2 kinases are required for myeloid-mediated support of T-ALL cells and promote IGF1R activation. Consistent with these findings, inhibition of integrins or FAK/PYK2 signaling diminishes leukemia burden in multiple organs and confers a survival advantage in a mouse model of T-ALL. Inhibiting integrin-mediated cell adhesion or FAK/PYK2 also diminishes survival of primary patient T-ALL cells co-cultured with myeloid cells. Furthermore, elevated integrin pathway gene signatures correlate significantly with myeloid enrichment and an inferior prognosis in pediatric T-ALL patients. Statement of significance Although tumor-associated myeloid cells provide critical support for T-ALL, our understanding of the underlying mechanisms remains limited. This study reveals that integrin-mediated adhesion and signaling are key mechanisms by which myeloid cells promote survival and progression of T-ALL blasts in the leukemic microenvironment. ### Competing Interest Statement The authors have declared no competing interest.