Fig. 10: Bortezomib potentiates the efficacy of ERK-targeted therapies by upregulating PHLDA1/2 expression.

a, b HEK293 cells were treated with thapsigargin (6 h), heat-shock (1 h), MG132 (6 h), or bortezomib (6 h) in the presence or absence of trametinib as indicated. PHLDA1/2 protein and mRNA expression levels were analyzed by immunoblotting (a) and qRT-PCR (b), respectively. c Retention of PHLDA1/2 expression by bortezomib prevents trametinib-induced AKT activation. H1299 cells that were transfected with siRNAs targeting PHLDA1/2 or control siRNA were treated with trametinib alone or in combination with bortezomib for 9 h. Expression levels of PHLDA1/2, the phosphorylation states of AKT and ERK, and cleaved PARP were monitored by immunoblotting. d, e MEK and proteasome inhibitors synergistically inhibit cancer cell growth. d H1299 cells were treated with various concentrations of bortezomib or trametinib alone or in combination for 72 h. The cells were then stained with crystal violet (left), and their survival rates were analyzed by CCK8 assay (right). e H1299 or Panc1 cells were transfected with siRNAs targeting PHLDA1/2 or with control siRNA, were treated with trametinib (10 μM) and/or bortezomib (10 nM) for 72 h, and their survival rates were then analyzed as in d. b, e Data are mean ± SEM from three independent experiments. P-values were assessed using one-way ANOVA followed by Tukey’s multiple comparisons test. Source data are provided as a Source Data file.