Sanguisorba officinalis L synergistically enhanced 5-fluorouracil cytotoxicity in colorectal cancer cells by promoting a reactive oxygen species-mediated, mitochondria-caspase-dependent apoptotic pathway.

Sanguisorba officinalis L. radix is a widely used herb called DiYu (DY) in China and has an extensive range of bioactivities, including anti-cancer, anti-inflammatory, and anti-oxidative activities. However, there is little evidence to support its anti-cancer effects against colorectal cancer (CRC). The first-line chemotherapeutic agent 5-fluorouracil (5-FU) is used to treat CRC, but its efficiency is hampered by acquired drug resistance. This study found that a water extract of DY exerted anti-proliferative effects against two CRC cell lines (HCT-116 and RKO), and it sensitized CRC cells to 5-FU therapy by activating a reactive oxygen species (ROS)-mediated, mitochondria-caspase-dependent apoptotic pathway. Co-treatment of DY and 5-FU significantly elevated ROS levels, up-regulated Bax/Bcl-2 ratio and triggered mitochondrial dysfunction, followed by a release of cytochrome c and up-regulation of proteins such as cleaved-caspase-9/3 and cleaved-PARP. Additionally, the induction of autophagy may be involved in mediating synergism of DY in HCT-116 cells. Gallic acid (GA), catechinic acid (CA) and ellagic acid (EA) were identified as the potential chief constituents responsible for the synergistic effects of DY. In conclusion, co-treatment of DY, specifically GA, CA and EA, with 5-FU may be a potential alternative therapeutic strategy for CRC by enhancing an intrinsic apoptotic pathway.