Aims
Emerging evidence suggests that highly treatment-resistant tumour-initiating cells (TICs) play a central role in the pathogenesis of pancreatic cancer. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to be a novel anticancer agent; however, recent studies have shown that many pancreatic cancer cells are resistant to apoptosis induction by TRAIL due to TRAIL-activated nuclear factor-kappaB (NF-kappaB) signalling. Several chemopreventive agents are able to inhibit NF-kappaB, and favourable
Background and aims
Emerging evidence suggests that highly treatment-resistant tumour-initiating cells (TICs) play a central role in the pathogenesis of pancreatic cancer. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to be a novel anticancer agent; however, recent studies have shown that many pancreatic cancer cells are resistant to apoptosis induction by TRAIL due to TRAIL-activated nuclear factor-kappaB (NF-kappaB) signalling. Several chemopreventive agents are able to inhibit NF-kappaB, and favourable
Conclusion
The data provide new insights into resistance mechanisms of TICs and suggest the combination of sulforaphane with TRAIL as a promising strategy for targeting of pancreatic TICs.
Methods
TICs were defined by expression patterns of a CD44(+)/CD24(-), CD44(+)/CD24(+) or CD44(+)/CD133(+) phenotype and correlation to growth in immunodeficient mice, differentiation grade, clonogenic growth, sphere formation, aldehyde dehydrogenase (ALDH) activity and therapy resistance.
Results
Mechanistically, specific binding of transcriptionally active cRel-containing NF-kappaB complexes in TICs was observed. Sulforaphane prevented NF-kappaB binding, downregulated apoptosis inhibitors and induced apoptosis, together with prevention of clonogenicity. Gemcitabine, the chemopreventive agents resveratrol and wogonin, and the death ligand TRAIL were less effective. In a xenograft model, sulforaphane strongly blocked tumour growth and angiogenesis, while combination with TRAIL had an additive effect without obvious cytotoxicity in normal cells. Freshly isolated patient tumour cells expressing markers for TICs could be sensitised by sulforaphane for TRAIL-induced cytotoxicity.