Degradation of MCL-1 by bufalin reverses acquired resistance to osimertinib in EGFR-mutant lung cancer.

Although osimertinib, an EGFR tyrosine kinase inhibitor, has become the standard therapy for treating non-small cell lung cancer (NSCLC) patients with EGFR-activating mutation, upregulation of MCL-1 induces acquired resistance to osimertinib. Bufalin, a natural digoxin-like ingredient isolated from a traditional Chinese medicine Chan Su, has been shown to downregulate MCL-1 in NSCLC cells. However, whether bufalin reverses this acquired resistance to osimertinib in NSCLC cells remains unclear. In this study, bufalin reduced cell viability and promoted apoptosis in osimertinib-resistant cells. Moreover, co-treatment with bufalin and osimertinib restored the sensitivity of osimertinib-resistant cells to osimertinib-induced growth regression and apoptosis in vitro and in vivo. Mechanistically, MEK/ERK-dependent MCL-1 phosphorylation and Ku70-mediated MCL-1 overexpression confer osimertinib resistance in EGFR-mutant NSCLC cells. In osimertinib-resistant cells, bufalin modulates Ku70-mediated MCL-1 degradation, but not MEK/ERK/MCL-1 signaling. In conclusion, our study suggests that bufalin eliminates resistance to osimertinib by inhibiting Ku70-mediated MCL-1 overexpression, indicating that a combination of osimertinib and bufalin could be an effective additional treatment to overcome acquired resistance to osimertinib in NSCLC cells.

Degradation of Mcl-1 through GSK-3ß Activation Regulates Apoptosis Induced by Bufalin in Non-Small Cell Lung Cancer H1975 Cells.

BACKGROUND/AIMS: Mcl-1, an anti-apoptotic Bcl-2 family member, is often overexpressed in non-small cell lung cancer (NSCLC). Bufalin has been reported to induce apoptosis in various tumor cells. However, there is no report showing that bufalin could downregulate Mcl-1 expression in NSCLC. METHODS: Cell proliferation was analyzed by cell counting kit-8 (CCK-8) assay in H1975 cells. Cell apoptosis was detected by flow cytometry. Mcl-1 mRNA was detected by RT-PCR. The expression of apoptosis-associated proteins in H1975 cells was detected by western blotting. The levels of Mcl-1 ubiquitination and NOXA were analyzed by Immunoprecipitation assay. RESULTS: Cell growth was inhibited by bufalin in a time and dose-dependent manner. Bufalin induced apoptosis in NSCLC cells by activating caspase cascades and downregulating Mcl-1 expression. However, overexpression of Mcl-1 diminished bufalin-induced apoptosis. Furthermore, bufalin did not reduce Mcl-1 mRNA expression in H1975 cells, but strongly promoted Mcl-1 protein degradation. Proteasome inhibitor MG132 markedly prevented the degradation of Mcl-1 and blocked bufalin-induced Mcl-1 reduction. Bufalin did not significantly affect NOXA protein levels, but downregulated the expression of p-GSK-3ß. GSK-3 inhibitor and GSK-3ß siRNA resulted in increased levels of Mcl-1 and reversed the bufalin-induced Mcl-1 degradation. CONCLUSION: Bufalin induced cell apoptosis in H1975 cells may be through downregulation of Mcl-1. Proteasomal degradation of Mcl-1 via GSK-3ß activation was involved in bufalin-induced apoptosis.

Effect and mechanism of ginsenoside Rg3 on postoperative life span of patients with non-small cell lung cancer.

OBJECTIVE: To explore the effect and mechanism of ginsenoside Rg3 (Shenyi Capsule) on the postoperative life span of patients with non-small cell lung cancer (NSCLC). METHODS: The prospective, randomized, controlled method was adopted. One hundred and thirty-three patients with NSCLC were randomly assigned to 3 groups: Shenyi Capsule group (43 cases), combined therapy group (Shenyi Capsule plus chemotherapy, 46 cases), and chemotherapy group (44 cases). The survival rates, immune function and the correlation between vascular endothelial growth factor (VEGF) expression and clinical effect were analyzed in the three groups. RESULTS: (1) The 1-year survival rate in the Shenyi group, the combined group and the chemotherapy group was 76.7% (33/43), 82.6% (38/46), and 79.5% (35/44), respectively; the 2-year survival rate was 67.4% (29/43), 71.7% (33/46), and 70.5% (31/44), respectively; and the 3-year survival rate was 46.5% (20/43), 54.3% (25/46), and 47.7% (21/44), respectively. There was no significant difference among the 3 groups (P>0.05). (2) NK cells were increased to different degrees and the ratio of CD4/CD8 was normal in the Shenyi Capsule group and the combined group, while the ratio of CD4/CD8 was disproportional in the chemotherapy group. (3) In the chemotherapy group, the 3-year survival rate was lower in patients with positive expression of VEGF than in patients with negative expression (37.0% vs 64.7%, chi2=17.9, P<0.01), but no signifi cant statistical difference was shown in the other two groups (53.6% vs 55.6%, P>0.05; 44.4% vs 50.0%, P>0.05). CONCLUSION: Shenyi Capsule, especially in combination with chemotherapy, can improve the life span of patients with NSCLC after operation. The mechanism might be correlated with improving the immune function and anti-tumor angiogenesis

Radiosensitivity enhancement by arsenic trioxide in conjunction with hyperthermia in the EC-1 esophageal carcinoma cell line.

OBJECTIVE: To explore the effect on radiosensitivity of arsenic trioxide (As203) in conjunction with hyperthermia on the esophageal carcinoma EC-1 cell line. METHOD: Inhibition of EC-1 cell proliferation at different concentrations of As203 was assessed using the methyl thiazolyl blue colorimetric method (MTT method), with calculation of IC50 value and choice of 20% of the IC50 as the experimental drug concentration. Blank control, As203, hyperthermia, radiotherapy group, As203 + hyperthermia, As203 + radiotherapy, hyperthermia + radiotherapy and As203 + hyperthermia + radiotherapy groups were established, and the cell survival fraction (SF) was calculated from flat panel colony forming analysis, and fitted by the 'multitarget click mathematical model'. Flow cytometry (FCM) was used to detect changes in cell apoptosis and the cell cycle. RESULTS: As203 exerted inhibitory effects on proliferation of esophageal carcinoma EC-1 cells, with an IC50 of 18.7 µmol/L. After joint therapy of As203 + hyperthermia + radiotherapy, the results of FCM showed that cells could be arrested in the G2/M phase, and as the ratio of cells in G0/G1 and S phases decreased, cell death became more pronounced. CONCLUSION: As203 and hyperthermia exert radiosensitivity effects on esophageal carcinoma EC-1 cells, with synergy in combination. Mechanistically, As203 and hyperthermia mainly influence the cell cycle distribution of EC-1 esophageal carcinoma cells, decreasing the repair of sublethal damage and inducing apoptosis, thereby enhancing the killing effects of radioactive rays.