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p21^WAF1 modulates drug-induced apoptosis and cell cycle arrest in B-cell precursor acute lymphoblastic leukemia

Lookup NU author(s): Dr Linda Hogarth, Dr Andrew Hall

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Abstract

p21(WAF1) is a well-characterized mediator of cell cycle arrest and may also modulate chemotherapy-induced cell death. The role of p21(WAF1) in drug-induced cell cycle arrest and apoptosis of acute lymphoblastic leukemia (ALL) cells was investigated using p53-functional patient-derived xenografts (PDXs), in which p21(WAF1) was epigenetically silenced in T-cell ALL (T-ALL), but not in B-cell precursor (BCP)-ALL PDXs. Upon exposure to diverse cytotoxic drugs, T-ALL PDX cells exhibited markedly increased caspase-3/7 activity and phosphatidylserine (PS) externalization on the plasma membrane compared with BCP-ALL cells. Despite dramatic differences in apoptotic characteristics between T-ALL and BCP-ALL PDXs, both ALL subtypes exhibited similar cell death kinetics and were equally sensitive to p53-inducing drugs in vitro, although T-ALL PDXs were significantly more sensitive to the histone deacetylase inhibitor vorinostat. Transient siRNA suppression of p21(WAF1) in the BCP-ALL 697 cell line resulted in a moderate depletion of the cell fraction in G1 phase and marked increase in PS externalization following exposure to etoposide. Furthermore, stable lentiviral p21(WAF1) silencing in the BCP-ALL Nalm-6 cell line accelerated PS externalization and cell death following exposure to etoposide and vorinostat, supporting previous findings. Finally, the Sp1 inhibitor, terameprocol, inhibited p21(WAF1) expression in Nalm-6 cells exposed to vorinostat and also partially augmented vorinostat-induced cell death. Taken together, these findings demonstrate that p21(WAF1) regulates the early stages of drug-induced apoptosis in ALL cells and significantly modulates their sensitivity to vorinostat.

Publication metadata

Author(s): Davies C, Hogarth LA, Mackenzie KL, Hall AG, Lock RB

Publication type: Article

Publication status: Published

Journal: Cell Cycle

Year: 2015

Volume: 14

Issue: 22

Pages: 3602-3612

Acceptance date: 22/09/2015

ISSN (print): 1538-4101

ISSN (electronic): 1551-4005

Publisher: Taylor & Francis Inc.

URL: http://dx.doi.org/10.1080/15384101.2015.1100774

DOI: 10.1080/15384101.2015.1100774

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