CD47 agonist peptide pkhb1 induces immunogenic cell death in T‐cell acute lymphoblastic leukemia cells

Abstract

T‐cell acute lymphoblastic leukemia (T‐ALL) has a poor prognosis derived from its genetic heterogeneity, which translates to a high chemoresistance. Recently, our workgroup designed TSP1‐derived CD47 agonist peptides and demonstrated their ability to induce cell death in chronic lymphocytic leukemia. Encouraged by these promising results, we evaluated cell death induced by PKHB1 (the first‐described serum‐stable CD47‐agonist peptide) on CEM and MOLT‐4 human cell lines (T‐ALL) and on one T‐murine tumor lymphoblast cell‐line (L5178Y‐R), also assessing caspase and calcium dependency and mitochondrial membrane potential. Additionally, we evaluated selectivity for cancer cell lines by analyzing cell death and viability of human and murine non‐tumor cells after CD47 activation. In vivo, we determined that PKHB1‐treatment in mice bearing L5178Y‐R cell line, increased leukocyte cell count in peripheral blood and lymphoid organs while recruiting leukocytes to the tumor site. To analyze if CD47 activation induced immunogenic cell death (ICD), we evaluated damage‐associated molecular patterns (DAMPs) exposure (Calreticulin, CRT) and release (ATP, HSP70, HSP90, HMGB1, CRT). Furthermore, we administered a prophylactic antitumor vaccination, determining immunologic memory. Our data indicate that PKHB1 induces caspase‐independent and calcium‐dependent cell death in leukemic cells while sparing non‐tumor murine and human cells. Moreover, our results show that PKHB1 can induce ICD in leukemic cells as it induces CRT exposure and DAMPs release in vitro, and prophylactic vaccinations inhibit tumor establishment in vivo. Altogether our results improve the knowledge of CD47 agonist peptides potential as therapeutic tools to treat leukemia.

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