PURPOSE: Pancreatic cancer is one of the most lethal solid tumors, mainly because of its intrinsic chemoresistance. We identified TAK1 as a central hub sustaining this resistance. Nanoliposomal irinotecan (nal-IRI) is a novel treatment for metastatic gemcitabine-refractory pancreatic cancer. We endeavored to identify circulating markers for TAK1 activation predicting chemoresistance in this setting.
EXPERIMENTAL DESIGN: In vivo activity of nal-IRI was validated in an orthotopic nude murine model expressing TAK1-specific shRNA. Plasma concentration of 20 different cytokines were measured by a multiplex xMAP/Luminex technology in patients prospectively enrolled to receive nal-IRI plus 5-fluorouracil/leucovorin (5-FU/LV). The optimal cutoff thresholds able to significantly predict patients' outcome were obtained on the basis of the maximization of the Youden's statistics.
RESULTS: Differential expression profiling revealed the gene coding for IL8 as the most significantly downregulated in shTAK1 pancreatic cancer cell lines. Mice bearing shTAK1 tumors had significantly lower plasma levels of IL8 and experienced a significant reduction in tumor growth if treated with nal-IRI, whereas those bearing TAK1-proficient tumors were resistant to this agent. In a discovery cohort of 77 patients, IL8 was the circulating factor most significantly correlated with survival (plasma levels lower vs higher than cutoff: mPFS 3.4 months vs 2.8 months; hazard ratio [HR], 2.55; 95% CI, 1.39-4.67; P = 0.0017; median overall survival 8.9 months vs 5.3 months; HR, 3.51; 95% CI, 0.84-6.68; P = 4.9e-05). These results were confirmed in a validation cohort of 50 patients.
CONCLUSIONS: Our study identified IL8 as the most significant circulating factor for TAK1 pathway activation and candidates IL8 as a potential predictive biomarker of resistance to nal-IRI in gemcitabine-refractory patients with pancreatic cancer.