Bilateral blockade of MEK- and PI3K-mediated pathways downstream of mutant KRAS as a treatment approach for peritoneal mucinous malignancies - Fig 4

<p><b>A.</b> Resistance to PI3Ki is correlated to increased pERK. Western blots of proteins isolated from LS174T cells treated with either MEKi, PI3Ki or both were probed with anti-phosphoERK1/2 (pERK1/2), anti-total ERK1/2, anti-phosphoAKT (pAKT) or anti-total AKT. Elevated levels of pERK1/2 (A, green arrow) and pAKT (A, green arrow) were seen 72 hours after exposure to PI3Ki coincident with the development of resistance to this inhibitor. <b>B.</b> Increased receptor tyrosine kinase (RTK) phosphorylation upon prolonged exposure to PI3K inhibitors. Protein lysates from PI3Ki-treated LS174T or RW7213 cells (72 hours) were incubated with human phospho-RTK array containing 49 RTKs, washed and probed with anti-phospho-tyrosine antibodies. Antigen-antibody complexes were detected by chemiluminescence and the results were quantified by densitometry. Numbers within brackets indicate fold increase in RTKs in PI3Ki-treated MCA cells relative to vehicle-treated controls. <b>C.</b> Synergistic reduction in viability of MCA cells treated with PI3K inhibitor and Linsitinib (inhibitor of IR and IGFR1). LS174T and RW7213 cells were treated with Linsitinib (blue) and PI3Ki (red) as single agents or in combination (green) in a fixed ratio for 72 hours. Each data point is the average of an n = 6. Error bars indicate standard error of the mean.