Pretreatment with anti-oxidants sensitizes oxidatively stressed human cancer cells to growth inhibitory effect of suberoylanilide hydroxamic acid (SAHA).
OBJECTIVE
Most prostate, colon and breast cancer cells are resistant to growth inhibitory effects of suberoylanilide hydroxamic acid (SAHA). We have examined whether the high oxidative stress in these cells causes a loss of SAHA activity and if so, whether pretreatment with an anti-oxidant can sensitize these cells to SAHA.


METHODS
A DNA-Hoechst dye fluorescence measured cell growth and dichlorfluorescein-diacetate (DCF-DA) dye fluorescence measured reactive oxygen species (ROS). Growth inhibitory and ROS-generating activities of SAHA in androgen-treated or untreated LNCaP cells and PC-3 prostate cancer cells, HT-29 and HCT-115 colon cancer cells, MDA-MB231 breast cancer cells and A549 and NCI-H460 lung cancer cells with or without pretreatment with an anti-oxidant Vitamin E was determined. SAHA activity against LNCaP cells treated with another anti-oxidant N-acetyl cysteine (NAC) was also determined. Liquid chromatography-mass spectrometry (LC-MS) was used to determine intracellular SAHA level.


RESULTS
SAHA treatment markedly inhibits LNCaP cell growth, when the cells are at a low ROS level. SAHA is, however, inactive against the same cell line, when the cells are at a high ROS level. A significant decrease in SAHA level was observed in LNCaP cells with high ROS after 24- and 72-h treatment when compared to cells with low ROS. Vitamin E pretreatment that reduces cellular ROS, synergistically sensitizes oxidatively stressed LNCaP, PC-3, HT-29, HCT-115 and MDA-MB231 cells, but not the A-549 and NCI-H460 cells with low ROS to SAHA. NAC treatment also sensitized androgen-treated LNCaP cells to the growth inhibitory effects of SAHA.


CONCLUSIONS
Response to SAHA could be improved by combining anti-oxidants such as Vitamin E with SAHA for the treatment of oxidatively stressed human malignancies that are otherwise resistant to SAHA.
Wisconsin Institutes for Medical Research, University of Wisconsin Carbone Comprehensive Cancer Center, Madison, WI 53705, USA. hsb@medicine.wisc.edu
Hirak S
HS
Basu
Amy
A
Mahlum
Farideh
F
Mehraein-Ghomi
Stacy J
SJ
Kegel
Song
S
Guo
Noel R
NR
Peters
George
G
Wilding
D000975:Antioxidants / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology; D045744:Cell Line, Tumor; D002853:Chromatography, Liquid; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D005260:Female; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D008297:Male; D013058:Mass Spectrometry; D018384:Oxidative Stress / Q000187:drug effects*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D014810:Vitamin E / Q000494:pharmacology*; D000077337:Vorinostat
D000975:Antioxidants; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D017382:Reactive Oxygen Species; D014810:Vitamin E; D000077337:Vorinostat