ABCG2 protein expression in tumors of patients with non-resectable pancreatic cancer treated with gemcitabine and nab-paclitaxel

We found indications of upregulation of ABCG2 expression in tumors of patients previously exposed to gemcitabine, and ABCG2 expression correlated with efficacy of GemNab as assessed by PFS and OS in patients previously exposed to CTx, but not in those naïve to CTx. These findings diverge from the prevailing assumption that ABCG2 confers chemoresistance and suggest that in certain contexts, ABCG2 expression may reflect tumor adaptation or selection. Given the unexpected direction of this association, our findings should be interpreted as hypothesis-generating, and further studies are needed to elucidate underlying biological mechanisms and validate ABCG2 as a potential predictive biomarker in this setting.