Hypoxia drives dihydropyrimidine dehydrogenase expression in macrophages and confers chemoresistance in colorectal cancer.

Abstract

Colorectal adenocarcinoma is a leading cause of death worldwide, and immune infiltration in colorectal tumors has been recognized recently as an important pathophysiological event. In this context, tumor-associated macrophages (TAM) have been related to chemoresistance to 5-fluorouracil (5-FU), the first-line chemotherapeutic agent used in treating colorectal cancers. Nevertheless, the details of this chemoresistance mechanism are still poorly elucidated. In the present study, we report that macrophages specifically overexpress dihydropyrimidine dehydrogenase (DPD) in hypoxia, leading to macrophage-induced chemoresistance to 5-FU via inactivation of the drug. Hypoxia-induced macrophage DPD expression was controlled by HIF-2α. TAMs constituted the main contributors to DPD activity in human colorectal primary or secondary tumors while cancer cells did not express significant levels of DPD. Additionally, contrary to humans, macrophages in mice do not express DPD. Together, these findings shed light on the role of TAMs in promoting chemoresistance in colorectal cancers and identify potential new therapeutic targets.