Panoply™ Human FOLR1 Over-expressing Stable Cell Line

Sorafenib is commonly used to treat advanced hepatocellular carcinoma (HCC). However, its clinical efficacy is limited by drug resistance. This study systematically explored the potential mechanisms of sorafenib resistance in HCC cells using label-free quantitative proteomics analysis. A total of 1709 proteins were quantified. Of these, 89 proteins were differentially expressed and highly enriched in cell-cell adhesion, negative regulation of apoptosis, drug response, and metabolic processes associated with sorafenib resistance. Notably, folate receptor α (FOLR1) was significantly upregulated in resistant HCC cells. Furthermore, in vitro studies demonstrated that FOLR1 overexpression reduced the sensitivity of HCC cells to sorafenib, while siRNA-targeted knockdown of FOLR1 increased its sensitivity. Immunoprecipitation-mass spectrometry analysis revealed a close association between FOLR1 and autophagy-related proteins. Further biological experiments revealed that FOLR1-induced sorafenib resistance was accompanied by activation of autophagy, while inhibition of autophagy significantly attenuated FOLR1-induced cell resistance. These results suggest that FOLR1 plays a driving role in sorafenib resistance in HCC, possibly through FOLR1-induced autophagy.

Here, researchers investigated whether FOLR1 could directly induce autophagy, ultimately promoting sorafenib resistance. In the presence of sorafenib, LC3-II/I levels were increased in FOLR1 overexpressing Huh7 cells, whereas these levels were decreased in FOLR1 knockdown Huh7-R cells (Figure 1D). Similarly, LC3-II/I levels were increased in FOLR1 overexpressing HepG2 cells, whereas these levels were decreased in FOLR1 knockdown HepG2 cells. Transmission electron microscopy revealed that more autophagic vacuoles (AVs) were observed in FOLR1 overexpressing Huh7 cells compared with the control group. In contrast, fewer AVs were observed in FOLR1 knockdown Huh7-R cells (Figure 1E). Autophagic flux analysis also demonstrated that FOLR1 overexpression led to increased autophagic flux, whereas FOLR1 knockdown led to decreased autophagic flux (Figure 1F). In FOLR1 overexpressing Huh7 cells, the presence of the autophagy inhibitor 3-MA significantly reversed the improved survival, which was also confirmed in HepG2 cells. These results suggest that FOLR1 enhances autophagy in the presence of sorafenib, thereby promoting sorafenib resistance.

Figure 1. Autophagy is involved in FOLR1-induced sorafenib resistance. (Chu H, et al., 2021)