Fig. 5: Inhibition of the PDR triggers cell death.

a MDA-MB-231 cells were treated with CIS alone or in combination with CHX, and K48 polyUB and cleaved caspase 3 were detected by western blotting. b MDA-MB-231-C3 cells were treated with CIS alone or in combination with CHX, and caspase 3 activation was monitored by CFP fluorescence. c MDA-MB-231 cells were treated with LAP alone or in combination with BTZ or TAK-243, and K48 polyUB and protein aggregation were detected by immunofluorescence and PROTEOSTAT staining, respectively. MDA-MB-231-C3 cells were treated with LAP alone or in combination with BTZ or TAK-243, and caspase 3 activation was monitored by CFP fluorescence. d Representative Giemsa staining was used to observe clonogenic cell growth in 4T1 cells treated with indicated drugs, either alone or in combination with BTZ or TAK-243, and clones were quantified. e Five breast cancer cell lines were treated with LAP alone or in combination with BTZ treatment, and K48 polyUB was detected by western blotting. f MDA-MB-231 cells were treated with indicated drugs; representative images and quantification of PROTEOSTAT were shown. g, h Five breast cancer cell lines were treated with increasing doses of LAP alone or in combination with a single dose of BTZ, achieving 10%–16% killing effect in different cell lines, and cell viability was detected by alamar blue assay. IC₅₀ of LAP treatment and LAP + BTZ treatment for 5 cell lines were calculated (g). Additive curves for LAP-resistant cell lines were shown, and additivity = E1 + E2 – E1 × E2, where E1 is the inhibitory effect of LAP and E2 is that of BTZ treatment (h). i A summary of the PDR. All values are presented as mean value (at least three replicates) ± SD, and P value was calculated by comparison with the Ctr group or indicated separately (two-tailed Student’s t-test, *P < 0.05, **P < 0.01, ***P < 0.001).