TY - JOUR
T1 - Yet another function of p53 - The switch that determines whether radiation-induced autophagy will be cytoprotective or nonprotective
T2 - Implications for autophagy inhibition as a therapeutic strategy
AU - Chakradeo, Shweta
AU - Sharma, Khushboo
AU - Alhaddad, Aisha
AU - Bakhshwin, Duaa
AU - Le, Ngoc
AU - Harada, Hisashi
AU - Nakajima, Wataru
AU - Yeudall, W. Andrew
AU - Torti, Suzy V.
AU - Torti, Frank M.
AU - Gewirtz, David A.
N1 - Publisher Copyright:
Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.
PY - 2015/5/1
Y1 - 2015/5/1
N2 - The influence of autophagy inhibition on radiation sensitivity was studied in human breast, head and neck, and non-small cell lung cancer cell lines, in cell lines that were either wild type or mutant/null in p53, and in cells where p53 was inducible or silenced. Whereas ionizing radiation promoted autophagy in all tumor cell lines studied, pharmacological inhibition of autophagy and/or genetic silencing of autophagy genes failed to influence sensitivity to radiation in p53 mutant Hs578t breast tumor cells, HN6 head and neck tumor cells, and H358 non-small cell lung cancer cells. The requirement for functional p53 in the promotion of cytoprotective autophagy by radiation was confirmed by the observation that radiation-induced autophagy was nonprotective in p53 null H1299 cells but was converted to the cytoprotective form with induction of p53. Conversely, whereas p53 wild-type HN30 head and neck cancer cells did show sensitization to radiation upon autophagy inhibition, HN30 cells in which p53 was knocked down using small hairpin RNA failed to be sensitized by pharmacological autophagy inhibition. Taken together, these findings indicate that radiation-induced autophagy can be either cytoprotective or nonprotective, a functional difference related to the presence or absence of function p53. Alternatively, these findings could be interpreted to suggest that whereas radiation can induce autophagy independent of p53 status, inhibition of autophagy promotes enhanced radiation sensitivity through a mechanism that requires functional p53. These observations are likely to have direct implications with respect to clinical efforts to modulate the response of malignancies to radiation through autophagy inhibition.
AB - The influence of autophagy inhibition on radiation sensitivity was studied in human breast, head and neck, and non-small cell lung cancer cell lines, in cell lines that were either wild type or mutant/null in p53, and in cells where p53 was inducible or silenced. Whereas ionizing radiation promoted autophagy in all tumor cell lines studied, pharmacological inhibition of autophagy and/or genetic silencing of autophagy genes failed to influence sensitivity to radiation in p53 mutant Hs578t breast tumor cells, HN6 head and neck tumor cells, and H358 non-small cell lung cancer cells. The requirement for functional p53 in the promotion of cytoprotective autophagy by radiation was confirmed by the observation that radiation-induced autophagy was nonprotective in p53 null H1299 cells but was converted to the cytoprotective form with induction of p53. Conversely, whereas p53 wild-type HN30 head and neck cancer cells did show sensitization to radiation upon autophagy inhibition, HN30 cells in which p53 was knocked down using small hairpin RNA failed to be sensitized by pharmacological autophagy inhibition. Taken together, these findings indicate that radiation-induced autophagy can be either cytoprotective or nonprotective, a functional difference related to the presence or absence of function p53. Alternatively, these findings could be interpreted to suggest that whereas radiation can induce autophagy independent of p53 status, inhibition of autophagy promotes enhanced radiation sensitivity through a mechanism that requires functional p53. These observations are likely to have direct implications with respect to clinical efforts to modulate the response of malignancies to radiation through autophagy inhibition.
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U2 - 10.1124/mol.114.095273
DO - 10.1124/mol.114.095273
M3 - Article
C2 - 25667224
AN - SCOPUS:84929287314
SN - 0026-895X
VL - 87
SP - 803
EP - 814
JO - Molecular pharmacology
JF - Molecular pharmacology
IS - 5
ER -