Inositol hexaphosphate inhibits constitutive activation of NF- kappa B in androgen-independent human prostate carcinoma DU145 cells.
BACKGROUND
One practical and translational approach to control prostate cancer (PCA) and associated death could be its preventive intervention by dietary agents. Several studies in recent years have shown both preventive and interventive efficacy of inositol hexaphosphate (IP6) in different animal tumor models, however, its effects in PCA and associated mechanisms have not been assessed in detail. Since transcription factor NF-kappa B is constitutively active in advanced and androgen-independent human PCA DU145 cells, here we assessed whether IP6 inhibits this constitutively active NF-kappa B and associated upstream effectors and whether such an affect of IP6 has biological relevance in causing inhibition of proliferation and induction of apoptosis in DU145 cells.


METHODS
We used DU145 cells and assessed NF-kappa B activation by gel shift assay. Western immunoblot and in-beads kinase assay were used for protein levels and enzyme activity. Proliferation was measured by BrdU labeling and apoptosis by annexin V/PI staining followed by FACS analysis.


RESULTS
Treatment of cells with 1 and 2 mM doses of IP6 resulted in a strong inhibition of NF-kappa B activation, which was consistent with a decrease in nuclear levels of NF-kappa B sub-unit proteins p65 and p50. IP6-treated cells also showed a strong inhibition in phospho-I kappa B alpha protein levels concomitant with a significant increase in total I kappa B alpha levels. This effect of IP6 also corroborated with a significant inhibition in IKK alpha kinase activity. In other studies, IP6-treated cells showed strong inhibition in cell proliferation and induction of apoptosis.


CONCLUSIONS
Our results suggest that IP6 could be a potent dietary agent in controlling the growth of advanced PCA cells and inducing their apoptotic death, in part, by its inhibitory effect on constitutively active NF-kappa B signaling pathway.
Agarwal
Chapla
C
Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
Dhanalakshmi
Sivanandhan
S
Singh
Rana P
RP
Agarwal
Rajesh
R
D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000378:metabolism; D008297:Male; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000502:physiology; D010833:Phytic Acid / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha; D010833:Phytic Acid; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human