Wnt inhibition leads to improved chemosensitivity in paediatric acute lymphoblastic leukaemia

Abstract

Summary While childhood acute lymphoblastic leukemia (ALL) is now highly curable, the dismal prognosis for children who relapse warrants novel therapeutic approaches. Previously, using an integrated genomic analysis of matched diagnosis - relapse paired samples, we identified overactivation of the Wnt pathway as a possible mechanism of recurrence. To validate these findings and document whether Wnt inhibition may sensitize cells to chemotherapy, we analyzed the expression of Activated β-catenin (and its downstream target BIRC5) using multiparameter phosphoflow cytometry and tested the efficacy of a recently developed Wnt inhibitor, iCRT14, in ALL cell lines and patient samples. We observed increased activation of β-catenin at relapse in 6 /10 patients. Furthermore, treatment of leukemic cell lines with iCRT14 led to significant downregulation of Wnt target genes and combination with traditional chemotherapeutic drugs resulted in a synergistic decrease in viability as well as a significant increase in apoptotic cell death. Finally, pre-treatment of purified blasts from patients with relapsed leukemia with the Wnt inhibitor followed by exposure to prednisolone, restored chemosensitivity in these cells. Our results demonstrate that overactivation of the Wnt pathway may contribute to chemoresistance in relapsed childhood ALL and that Wnt-inhibition may be a promising therapeutic approach.

MAPK signaling cascades mediate distinct glucocorticoid resistance mechanisms in pediatric leukemia

“…Viral preparation, genome-wide shRNA screening, 17 real-time quantitative polymerase chain reaction, 18 apoptosis assays, 18 cell viability assays, 18 immunoblots, 18 phospho flow cytometry, 19 and xenograft models [20][21][22][23] were all performed as previously described with additional details and modifications available in the supplemental Methods, found on the Blood Web site.…”

Progress and Prospects in Pediatric Leukemia

“…33 A number of relapse-specific alterations have been shown to confer resistance to single agents (e.g., glucocorticoid resistance: TBLXR1 deletions and CREBBP mutations; 6 MP and 6 TG resistance-NT5C2 and PRPS1 mutations) or pan-resistance to all agents (e.g., Wnt and MAP kinase pathway activation Ϯ Ras mutations). [34][35][36] Genomics has also helped identify host characteristics, like single nucleotide polymorphisms in the host that affect the pharmacokinetics and associated side effects of multiple drugs such as methotrexate, vincristine, glucocorticoids, and asparaginase. 8 Relapse can occur in the bone marrow and/or in extramedullary sites (CNS or testes).…”

Therapies on the horizon for childhood acute lymphoblastic leukemia

“…Specific alterations are associated with pan-resistance to all conventional agents or may be associated with resistance to a single class (22). For example activation of both the Wnt and mitogen activated protein kinase pathways (MAPK) is commonly observed at relapse and is associated with resistance to all agents used in therapy (23, 24). Ras mutations in part drive MAPK activation and targeted agents are available that are attractive candidates for novel therapy (24, 25).…”