Naringenin up-regulates the expression of death receptor 5 and enhances TRAIL-induced apoptosis in human lung cancer A549 cells.
METHODS
While TRAIL is relatively non-toxic to normal cells, it can selectively induce apoptosis in many types of transformed cells. Nevertheless, some non-small cell lung cancer (NSCLC) cells are particularly resistant to the effects of TRAIL. Here, we report that in combination with naringenin exposure to TRAIL induced apoptosis in TRAIL-resistant NSCLC A549 cells with no detectable inhibitory effects on cell proliferation of normal lung fibroblast cells.


RESULTS
Cytotoxicity was evaluated by MTT assay. Apoptosis was detected using DAPI staining, and flow cytometry. The protein levels were determined by Western blot analysis. Caspase activity was measured using a colorimetric assay. For knockdown of Bid and DR5 expression, Bid and DR5 siRNAs were transfected into cells via lipofection. We could show that following exposure to naringenin, DR5 proteins were up-regulated and knockdown of DR5 expression by siRNA attenuated naringenin plus TRAIL-induced apoptosis. Naringenin and TRAIL effectively induced Bid cleavage and siRNA-mediated silencing of Bid reduced the sensitizing effect of naringenin. Furthermore, co-treatment with naringenin and TRAIL resulted in reduction of the clonogenic capacity of A549 cells, and surviving clones could be re-sensitized for repeated TRAIL treatment.


CONCLUSIONS
Our results indicate that treatment with a combination of TRAIL and naringenin may be a safe strategy for treatment of resistant NSCLC.
Jin
Cheng-Yun
CY
Department of Biomaterial Control (BK21 program), Dongeui University Graduate School, Busan, Republic of Korea.
Park
Cheol
C
Hwang
Hye Jin
HJ
Kim
Gi-Young
GY
Choi
Byung Tae
BT
Kim
Wun-Jae
WJ
Choi
Yung Hyun
YH
D000970:Antineoplastic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D051544:Cytochrome P-450 CYP3A; D065692:Cytochrome P-450 CYP3A Inhibitors; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D004965:Estrogen Antagonists / Q000494:pharmacology; D044950:Flavanones / Q000494:pharmacology*; D020868:Gene Silencing; D006801:Humans; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*
D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D065692:Cytochrome P-450 CYP3A Inhibitors; D004965:Estrogen Antagonists; D044950:Flavanones; D034741:RNA, Small Interfering; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; C005273:naringenin