Intensive efforts have been made in the area of identifying drug resistance modulators from traditional Chinese medicine. Various natural plant extracts have been reported for their reversal effect of drug resistance in cancers. This study was to assess the reversal potential of Curcumae longae Rhizoma extract (CLRE) in 5-Fluorouracil (5-Fu) resistance to colon cancer and explore its underly mechanism.

Increased concentrations of 5-Fu were used to culture SW480. A series of concentrations of CLRE were used to treat the 5-Fu resistant SW480 cells. WST-8 assay was used to detect the cell viability. Cell apoptosis was assessed by SuperView™ 488 Caspase-3 Assay Kit. The quantification of mentioned factors was archived by RT-qPCR. Network pharmacology analysis was used to explore the target of CLRE.

5-Fu resistant cell line (SW480/5-FuR) was established. The IC50 value of CLRE against SW480/5-FuR was 181.0 ± 14.12 µg/ml. CLRE can resensitize the SW480/5-FuR to 5-Fu by inhibiting cell growth. The combination treatment (CLRE+5-Fu) induced cell apoptosis via inhibition of bcl-2 and activation of caspase-3 and bax. Three active ingredients from CLRE were identified. TLR4 was targeted by these three ingredients and linked these ingredients to PI3K/Akt/mTOR pathway. The levels of TLR4, PI3K, AKT1, and mTORC1 mRNA were decreased when 5-Fu was combined with CLRE.

CLRE could reverse 5-Fu resistance in colon cancer by inactivating TLR4/PI3K/AKT/mTORC1 pathway. This finding might provide a molecular basis and a valuable direction for further clinical applications and research for treating 5-Fu resistant colon cancer.