[The CK2 inhibitor quninalizarin enhances the anti-proliferative effect of icotinib on EGFR-TKIs-resistant cell lines and its underlying mechanisms].

OBJECTIVE: To explore whether quninalizarin, an specific inhibitor of protein kinase CK2, could sensitize icotinib in EGFR-TKIs (epithelial growth factor receptor-tyrosine kinase inhibitor)-resistant cell lines and uncover the underlying mechanisms. METHODS: MTT assay was performed to evaluate the inhibitory effect of quninalizarin, icotinib or the combination of both on cell proliferation in several lung adenocarcinoma cell lines. Western blot assay was used to assess if combined inhibition of EGFR and protein kinase CK2 by icotinib and quninalizarin, exerts effect on the expression and phosphorylation of major proteins of EGFR signaling pathways. RESULTS: The IC50 of HCC827, H1650, H1975 and A549 cells for icotinib were (8.07±2.00)µmol/L, (66.01±6.64)µmol/L, (265.60±9.47)µmol/L and (87.88±6.8)µmol/L, respectively, indicating that HCC827 cells are sensitive to icotinib, and the H1650, H1975 and A549 cells are relatively resistant to icotinib. When treated with both quninalizarin and icotinib in the concentration of 50 µmol/L, the viability of H1650, H1975 and A549 cells was (40.64±3.73)%, (65.74±3.27)% and (44.96±0.48)%, respectively, significantly lower than that of H1650, H1975 and A549 cells treated with 50 µmol/L icotinib alone (55.05±1.22)%, (71.98±1.60)% and (61.74±6.18)%, respectively (P<0.01 for all). When treated with both 100 µmol/L quninalizarin and 100 µmol/L icotinib, the viability of H1650, H1975 and A549 ells were (23.35±0.81)%, (55.70±1.03)%, (33.42±1.33)%, respectively, significantly lower than the viability of H1650, H1975 and A549 cells treated with 100 µmol/L icotinib alone (40.57±2.65)%, (62.40±2.05)% and (44.97±8.20)%, respectively, (P<0.01 for all). The two-way ANOVA analysis showed that compared with the viability of EGFR-TKIs-resistant cells (H1650, H1975, A549) treated with 50 µmol/L and 100 µmol/L icotinib alone, the viability of cells treated with icotinib and quinalizarin were significantly suppressed, and the differences were statistically significant (P<0.01). In addition, the phosphorylation form of Akt and ERK (namely p-Akt and p-ERK) were significantly down-regulated by treating with quninalizarin and icotinib together in the H1650 cells while the expression of Akt and ERK changed little. CONCLUSIONS: Quinalizarin, as a specific CK2 inhibitor, may overcome icotinib resistance by inhibiting proliferation mediated by Akt and ERK in human lung adenocarcinoma cell lines, and enhances the suppressive effect of icotinib on the proliferation of EGFR-TKIs-resistant human lung adenocarcinoma cells.