Figure 4 | Cell Death & Disease

Figure 4

From: Low levels of Caspase-3 predict favourable response to 5FU-based chemotherapy in advanced colorectal cancer: Caspase-3 inhibition as a therapeutic approach

Figure 4

Chemotherapy-induced Caspase-3 activation increases expression of proliferation markers, and inhibition of Caspase-3 and its downstream effectors antagonises this proliferation signature. (a) Fresh patient colon tumour tissue was treated with 5FU-based CT alone and in combination with specific Caspase-3 inhibitor (DNLD) and COX-2 inhibitors (Aspirin and Celecoxib). Tissue was sectioned and stained for COX-2, β-Catenin, Ki-67, and ZEB1 (a) and scored based on the extent and intensity of staining (scale bar=100 μm). (b) COX-2 levels were significantly increased following CT when compared with untreated tissue (P=0.00017). Expression of COX-2 was reduced when Caspase-3 was inhibited during CT (P=0.000443) and celecoxib co-treatment also significantly antagonised COX-2 expression (P=0.000242). (c) CT significantly increased β-Catenin levels when compared with untreated tissue (P=0.00237). Specific Caspase-3 inhibition reduced β-Catenin expression significantly (P=0.001), and inhibition of downstream Caspase-3 effectors via aspirin and celecoxib resulted in reduction in β-Catenin expression (P=0.0003 and P=0.003, respectively). (d) Expression of Ki-67 was not significantly increased following CT when compared with untreated tissue. Inhibition of Caspase-3 in concert with CT (P=0.008) and its downstream effectors alongside 5FU-based CT reduced Ki-67 expression (5FU/Oxali versus 5FU/Oxali+Celecoxib, P=0.021, 5FU/Oxali versus 5FU/Oxali+Aspirin, P=0.003). (e) Expression of ZEB1 was not altered across treatment groups, suggesting that the EMT does not accompany Caspase-3-driven proliferation. (f) 5FU-based regimen caused a significant increase in PGE2 release (Untreated versus 5FU/Oxali, P=0.034), while specific Caspase-3 and COX-2 inhibition reduced PGE2 media levels (5FU/Oxali versus 5FU/Oxali+DNLD, P=0.033; 5FU/Oxali versus 5FU/Oxali+Aspirin, P=0.021; 5FU/Oxali versus 5FU/Oxali+Celecoxib, P=0.045; n=4–6 explants evaluated per treatment; ANOVA and post hoc Tukey). *Denotes statistically significant difference, P-values⩽0.05.

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