Sulforaphane sensitizes tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis through downregulation of ERK and Akt in lung adenocarcinoma A549 cells.
The cytotoxic effect of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is limited in some cancer cells, including A549 lung adenocarcinoma cells. However, treatment with TRAIL in combination with subtoxic concentrations of sulforaphane (SFN) sensitizes TRAIL-resistant A549 cells to TRAIL-mediated apoptosis. Combined treatment with SFN and TRAIL induced chromatin condensation, DNA fragmentation, annexin V staining and sub-G(1) phase DNA content. These indicators of apoptosis correlate with the induction of caspase-3 activity that results in the cleavage of poly(ADP-ribose) polymerase and the release of lactate dehydrogenase. Both the cytotoxic effect and apoptotic characteristics induced by combined treatment were significantly inhibited by z-DEVD-fmk, a caspase-3 inhibitor, demonstrating the important role of caspase-3 in the observed cytotoxic effect. Combined treatment also triggered the activation of p38 MAPK and JNK, and downregulation of ERK and Akt. Inhibitors of ERK (PD98059) or Akt (LY294002), but not p38 MAPK, resulted in significantly decreased cell viability. Although the activation of JNK was increased in response to combined treatment, inhibition of the JNK pathway significantly attenuated cell viability. These results indicate that caspase-3 is a key regulator of apoptosis in response to combined SFN and TRAIL in human lung adenocarcinoma A549 cells through downregulation of ERK and Akt.
Jin
Cheung-Yun
CY
Department of Microbiology, Pusan National University, Busan 614-052, South Korea.
Moon
Dong-Oh
DO
Lee
Jae-Dong
JD
Heo
Moon-Soo
MS
Choi
Yung Hyun
YH
Lee
Chang-Min
CM
Park
Yeong-Min
YM
Kim
Gi-Young
GY
D000230:Adenocarcinoma / Q000378:metabolism*; D016588:Anticarcinogenic Agents / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D006801:Humans; D017879:Isothiocyanates; D008175:Lung Neoplasms / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D013454:Sulfoxides; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage / Q000494:pharmacology*; D013861:Thiocyanates / Q000008:administration & dosage / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha
D016588:Anticarcinogenic Agents; D017879:Isothiocyanates; D013454:Sulfoxides; D053221:TNF-Related Apoptosis-Inducing Ligand; D013861:Thiocyanates; D014409:Tumor Necrosis Factor-alpha; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3; C016766:sulforaphane