Abstract
Exposure of MCF-7 breast tumor cells or HCT-116 colon carcinoma cells to clinically relevant concentrations of doxorubicin (Adriamycin; Farmitalia Research Laboratories, Milan, Italy) or camptothecin results in both autophagy and senescence. To determine whether autophagy is required for chemotherapy-induced senescence, reactive oxygen generation induced by Adriamycin was suppressed by N-acetyl cysteine and glutathione, and the induction of ataxia telangiectasia mutated, p53, and p21 was modulated pharmacologically and/or genetically. In all cases, autophagy and senescence were collaterally suppressed. The close association between autophagy and senescence indicated by these experiments reflects their collateral regulation via common signaling pathways. The potential relationship between autophagy and senescence was further examined through pharmacologic inhibition of autophagy with chloroquine and 3-methyl-adenine and genetic ablation of the autophagy-related genes ATG5 and ATG7. However, inhibition of autophagy by pharmacological and genetic approaches could not entirely abrogate the senescence response, which was only reduced and/or delayed. Taken together, our findings suggest that autophagy and senescence tend to occur in parallel, and furthermore that autophagy accelerates the development of the senescent phenotype. However, these responses are not inexorably linked or interdependent, as senescence can occur when autophagy is abrogated.
Footnotes
R.W.G. and X.D. contributed equally to this work.
The Virginia Commonwealth University Flow Cytometry and Imaging Shared Resource Facility is supported in part by the National Institutes of Health National Cancer Institute [Grant P30CA16059]. R.W.G. was supported by the National Institutes of Health National Cancer Institute [Grant T32 CA113277-04]. KV was supported in part by the National Institutes of Health [Grants R01-NS064593, R21-CA156995].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
↵
The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
ABBREVIATIONS:
- SA-β-gal
- senescence-associated β-galactosidase
- ADR
- Adriamycin
- AOS
- acridine orange staining
- ATM
- ataxia telangiectasia mutated
- AVO
- acidic vesicular organelle
- CPT
- camptothecin
- CQ
- chloroquine
- DCF
- 2′,7′-dichlorofluorescin
- FACS
- fluorescence-activated cell sorting
- GSH
- glutathione
- KU-55933
- 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one
- 3-MA
- 3-methyl-adenine
- NAC
- N-acetyl cysteine
- PBS
- phosphate-buffered saline
- pRb
- retinoblastoma protein
- Rb
- retinoblastoma
- ROS
- reactive oxygen species
- shControl
- shRNA against a scramble control
- shRNA
- short-haired RNA
- shATM
- shRNA against ATM
- shp21
- shRNA against p21
- shATG
- shRNA against ATG.
- Received July 13, 2012.
- Accepted August 24, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|