Fig. 8: Knockdown of KRT8 increased chemosensitivity of chordoma cells in vivo.

NOD/SCID mice bearing CM319 cell xenografts were divided into four groups: three mice for each group—(1) control group (Con), (2) siKRT8 group (siKRT8), (3) doxorubicin group (Doxo, 2 mg/kg), and (4) siKRT8 and doxorubicin group (si + Doxo 2 mg/kg). a siKRT8 combined with doxorubicin exerted a more significant anti-tumor effect as shown by tumor weights and volume. b Western blotting analysis and quantification of KRT8, BiP, CHOP, Caspase 4, SQSTM1, and LC3B protein expression of tumor xenograft tissues (normalized to GAPDH expression). c Immunofluorescence staining of BiP of tumor xenograft sections (scale bar = 100 μm). d Representative TEM image of tumor tissues, ER was evidently distended in si + Doxo-treated groups (arrowhead, scale bar = 1μm). e Proposed mechanism of KRT8 in chordoma drug resistance. KRT8 of chordoma cells is upregulated after chemotherapy, accompanied by increased autophagy activity and ER stress. Knockdown of KRT8 sensitizes chordoma cells to chemotherapy by blocking late-stage autophagy and aggravating ER stress through PERK/eIF2α arm of UPR (n = 3, *p < 0.05 vs. indicated group, **p < 0.01 vs. indicated group, NS: not statistically significant vs. indicated group, Con: control group, Doxo: doxorubicin-treated group. For all the above-mentioned statistical analyses, significance was determined by one-way ANOVA followed by Tukey’s multiple comparisons test and the results were shown as mean ± SD).