Differential effects of garcinol and curcumin on histone and p53 modifications in tumour cells.
BACKGROUND
Post-translational modifications (PTMs) of histones and other proteins are perturbed in tumours. For example, reduced levels of acetylated H4K16 and trimethylated H4K20 are associated with high tumour grade and poor survival in breast cancer. Drug-like molecules that can reprogram selected histone PTMs in tumour cells are therefore of interest as potential cancer chemopreventive agents. In this study we assessed the effects of the phytocompounds garcinol and curcumin on histone and p53 modification in cancer cells, focussing on the breast tumour cell line MCF7.


METHODS
Cell viability/proliferation assays, cell cycle analysis by flow cytometry, immunodetection of specific histone and p53 acetylation marks, western blotting, siRNA and RT-qPCR.


RESULTS
Although treatment with curcumin, garcinol or the garcinol derivative LTK-14 hampered MCF7 cell proliferation, differential effects of these compounds on histone modifications were observed. Garcinol treatment resulted in a strong reduction in H3K18 acetylation, which is required for S phase progression. Similar effects of garcinol on H3K18 acetylation were observed in the osteosarcoma cells lines U2OS and SaOS2. In contrast, global levels of acetylated H4K16 and trimethylated H4K20 in MCF7 cells were elevated after garcinol treatment. This was accompanied by upregulation of DNA damage signalling markers such as γH2A.X, H3K56Ac, p53 and TIP60. In contrast, exposure of MCF7 cells to curcumin resulted in increased global levels of acetylated H3K18 and H4K16, and was less effective in inducing DNA damage markers. In addition to its effects on histone modifications, garcinol was found to block CBP/p300-mediated acetylation of the C-terminal activation domain of p53, but resulted in enhanced acetylation of p53K120, and accumulation of p53 in the cytoplasmic compartment. Finally, we show that the elevation of H4K20Me3 levels by garcinol correlated with increased expression of SUV420H2, and was prevented by siRNA targeting of SUV420H2.


CONCLUSIONS
In summary, although garcinol and curcumin can both inhibit histone acetyltransferase activities, our results show that these compounds have differential effects on cancer cells in culture. Garcinol treatment alters expression of chromatin modifying enzymes in MCF7 cells, resulting in reprogramming of key histone and p53 PTMs and growth arrest, underscoring its potential as a cancer chemopreventive agent.
Gene Regulation Group, Centre for Biomolecular Sciences, School of Pharmacy, University of Nottingham, University Park, NG7 2RD, Nottingham. United Kingdom.
Hilary M
HM
Collins
Magdy K
MK
Abdelghany
Marie
M
Messmer
Baigong
B
Yue
Sian E
SE
Deeves
Karin B
KB
Kindle
Kempegowda
K
Mantelingu
Akhmed
A
Aslam
G Sebastiaan
GS
Winkler
Tapas K
TK
Kundu
David M
DM
Heery
D000107:Acetylation; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D050882:CREB-Binding Protein / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003474:Curcumin / Q000494:pharmacology*; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D051548:Histone Acetyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011495:Histone-Lysine N-Methyltransferase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D000074443:Lysine Acetyltransferase 5; D061986:MCF-7 Cells; D008745:Methylation; D016133:Polymerase Chain Reaction; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D034622:RNA Interference; D013729:Terpenes / Q000494:pharmacology*; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; C468783:H2AX protein, human; D006657:Histones; C495901:TP53 protein, human; D013729:Terpenes; D016159:Tumor Suppressor Protein p53; D011495:Histone-Lysine N-Methyltransferase; C542918:KMT5C protein, human; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D051548:Histone Acetyltransferases; C098489:KAT5 protein, human; D000074443:Lysine Acetyltransferase 5; D003474:Curcumin; C054597:garcinol