Maintenance of the Expression of c-FLIP by Hsp70 to Resist Licochalcone A-Induced Anti-Colorectal Cancer Effect through ERK-Mediated Autophagy Induction.

Background: The mortality rate of colorectal cancer (CRC) ranks second worldwide. Previous research had indicated that licochalcone A (LA) was a flavonoid in licorice with diverse anticancer effects. We explored the underlying mechanisms of LA-triggered anticancer activity in CRC.

Methods: Thiazolyl Blue (MTT) experiment and EdU staining were utilized to evaluate cell proliferation. Meanwhile, cells were stained by Annexin V/PI to investigate apoptosis through flow cytometry assay. Moreover, expressions of proteins were detected by immunoblotting, and the level of related mRNA was investigated using real-time quantitative PCR.

Results: LA selectively suppressed the proliferation and triggered apoptosis of CRC cells. Strikingly, LA induced cytoprotective autophagic activities since the suppression of autophagy significantly strengthened LA-induced cytotoxicity and FLICE inhibitory protein (c-FLIPL) degradation, meanwhile reversing LA-mediated heat shock protein 70 (Hsp70) upregulation. Moreover, autophagy-mediated Hsp70 upregulation resisted LA-induced anticancer effects since the suppression of Hsp70 strengthened LA-triggered cytotoxicity and c-FLIPL degradation. Furthermore, LA greatly activated extracellular signal-regulated protein kinases (ERK) and p38. However, blocking of ERK, but not p38, significantly boosted LA-triggered cell death and c-FLIPL downregulation. Suppression of ERK also reversed LA-mediated autophagic induction.

Conclusions: LA increased Hsp70 expression depending on ERK-mediated autophagy, which protected CRC cells from LA-induced anticancer activities.