Theaflavins target Fas/caspase-8 and Akt/pBad pathways to induce apoptosis in p53-mutated human breast cancer cells.
The most common alterations found in breast cancer are inactivation or mutation of tumor suppressor gene p53. The present study revealed that theaflavins induced p53-mutated human breast cancer cell apoptosis. Pharmacological inhibition of caspase-8 or expression of dominant-negative (Dn)-caspase-8/Fas-associated death domain (FADD) partially inhibited apoptosis, whereas caspase-9 inhibitor completely blocked the killing indicating involvement of parallel pathways that converged to mitochondria. Further studies demonstrated theaflavin-induced Fas upregulation through the activation of c-jun N-terminal kinase, Fas-FADD interaction in a Fas ligand-independent manner, caspase-8 activation and t-Bid formation. A search for the parallel pathway revealed theaflavin-induced inhibition of survival pathway, mediated by Akt deactivation and Bcl-xL/Bcl-2-associated death promoter dephosphorylation. These well-defined routes of growth control converged to a common process of mitochondrial transmembrane potential loss, cytochrome c release and activation of the executioner caspase-9 and -3. Overexpression of either constitutively active myristylated-Akt (Myr-Akt) or Dn-caspase-8 partially blocked theaflavin-induced mitochondrial permeability transition and apoptosis of p53-mutated cells, whereas cotransfection of Myr-Akt and Dn-caspase-8 completely abolished theaflavin effect thereby negating the possibility of existence of third pathways. These results and other biochemical correlates established the concept that two distinct signaling pathways were regulated by theaflavins to induce mitochondrial death cascade, eventually culminating to apoptosis of p53-mutated human breast cancer cells that are strongly resistant to conventional therapies.
Lahiry
Lakshmishri
L
Division of Molecular Medicine, Bose Institute, P-1/12, CIT, Scheme VIIM, Kolkata, India.
Saha
Baisakhi
B
Chakraborty
Juni
J
Adhikary
Arghya
A
Mohanty
Suchismita
S
Hossain
Dewan Md Sakib
DM
Banerjee
Shuvomoy
S
Das
Kaushik
K
Sa
Gaurisankar
G
Das
Tanya
T
D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D044946:Biflavonoids / Q000494:pharmacology*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D061945:Caspase Inhibitors; D002392:Catechin / Q000494:pharmacology*; D045304:Cytochromes c / Q000378:metabolism; D053200:Fas-Associated Death Domain Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D051025:bcl-Associated Death Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019014:fas Receptor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
D000975:Antioxidants; C494819:BAD protein, human; D044946:Biflavonoids; D061945:Caspase Inhibitors; C491901:FAS protein, human; D053200:Fas-Associated Death Domain Protein; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051025:bcl-Associated Death Protein; D019014:fas Receptor; C056068:theaflavin; D002392:Catechin; D045304:Cytochromes c; D051057:Proto-Oncogene Proteins c-akt; D053181:Caspase 8; D053453:Caspase 9