Curcumin effectively inhibits oncogenic NF-κB signaling and restrains stemness features in liver cancer.
OBJECTIVE
The cancer stem cells (CSCs) have important therapeutic implications for multi-resistant cancers including hepatocellular carcinoma (HCC). Among the key pathways frequently activated in liver CSCs is NF-κB signaling.


METHODS
We evaluated the CSCs-depleting potential of NF-κB inhibition in liver cancer achieved by the IKK inhibitor curcumin, RNAi and specific peptide SN50. The effects on CSCs were assessed by analysis of side population (SP), sphere formation and tumorigenicity. Molecular changes were determined by RT-qPCR, global gene expression microarray, EMSA, and Western blotting.


RESULTS
HCC cell lines exposed to curcumin exhibited differential responses to curcumin and were classified as sensitive and resistant. In sensitive lines, curcumin-mediated induction of cell death was directly related to the extent of NF-κB inhibition. The treatment also led to a selective CSC-depletion as evidenced by a reduced SP size, decreased sphere formation, down-regulation of CSC markers and suppressed tumorigenicity. Similarly, NF-κB inhibition by SN50 and siRNA against p65 suppressed tumor cell growth. In contrast, curcumin-resistant cells displayed a paradoxical increase in proliferation and expression of CSC markers. Mechanistically, an important component of the CSC-depleting activity of curcumin could be attributed to a NF-κB-mediated HDAC inhibition. Co-administration of the class I/II HDAC inhibitor trichostatine sensitized resistant cells to curcumin. Further, integration of a predictive signature of curcumin sensitivity with human HCC database indicated that HCCs with poor prognosis and progenitor features are most likely to benefit from NF-κB inhibition.


CONCLUSIONS
These results demonstrate that blocking NF-κB can specifically target CSC populations and suggest a potential for combined inhibition of NF-κB and HDAC signaling for treatment of liver cancer patients with poor prognosis.
Laboratory of Experimental Carcinogenesis, National Cancer Institute, NIH, Bethesda, USA; Department of Medicine I, Johannes Gutenberg University, Mainz, Germany. Electronic address: marquarj@uni-mainz.de.
Jens U
JU
Marquardt
Departamento de Ciencias de la Salud, División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana-Iztapalapa, Mexico.
Luis
L
Gomez-Quiroz
Department of Medicine I, Johannes Gutenberg University, Mainz, Germany.
Lucrecia O
LO
Arreguin Camacho
Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
Federico
F
Pinna
Laboratory of Experimental Carcinogenesis, National Cancer Institute, NIH, Bethesda, USA.
Yun-Han
YH
Lee
Laboratory of Experimental Carcinogenesis, National Cancer Institute, NIH, Bethesda, USA.
Mitsuteru
M
Kitade
Departamento de Ciencias de la Salud, División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana-Iztapalapa, Mexico.
Mayrel Palestino
MP
Domínguez
Department of Medicine I, Johannes Gutenberg University, Mainz, Germany.
Darko
D
Castven
Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany.
Kai
K
Breuhahn
Laboratory of Experimental Carcinogenesis, National Cancer Institute, NIH, Bethesda, USA.
Elizabeth A
EA
Conner
Department of Medicine I, Johannes Gutenberg University, Mainz, Germany.
Peter R
PR
Galle
Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark.
Jesper B
JB
Andersen
Laboratory of Experimental Carcinogenesis, National Cancer Institute, NIH, Bethesda, USA.
Valentina M
VM
Factor
Laboratory of Experimental Carcinogenesis, National Cancer Institute, NIH, Bethesda, USA.
Snorri S
SS
Thorgeirsson
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D003474:Curcumin / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000502:physiology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000502:physiology; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects*
D000970:Antineoplastic Agents; D006877:Hydroxamic Acids; D016328:NF-kappa B; C012589:trichostatin A; D006655:Histone Deacetylases; D003474:Curcumin
Cancer stem cells; Hepatocarcinogenesis; Histone deacetylases; Liver cancer; NF-κB