Inhibition of DNA‑PK by gefitinib causes synergism between gefitinib and cisplatin in NSCLC

Lung cancer has the highest incidence and mortality rates among the malignant tumor types worldwide. Platinum‑based chemotherapy is the main treatment for advanced non‑small‑cell lung cancer (NSCLC), and epidermal growth factor receptor‑tyrosine kinase inhibitors (EGFR‑TKIs) have greatly improved the survival of patients with EGFR‑sensitive mutations. However, there is no standard therapy for treating patients who are EGFR‑TKI resistant. Combining EGFR‑TKIs and platinum‑based chemotherapy is the most popular strategy in the clinical practice. However, the synergistic mechanism between EGFR‑TKIs and platinum remains unknown. Therefore, the aim of the present study was to determine the synergistic mechanism of gefitinib (an EGFR‑TKI) and cisplatin (a main platinum‑based drug). MTT assay, apoptosis analysis, tumorsphere formation and an orthotropic xenograft mouse model were used to examine the combination effects of gefitinib and cisplatin on NSCLC. Co‑immunoprecipitation and immunofluorescence were used to identify the underlying mechanism. It was found that gefitinib could selectively inhibit EGFR from entering the nucleus, decrease DNA‑PK activity and enhance the cytotoxicity of cisplatin on NSCLC. Collectively, the results suggested that inhibition of DNA‑dependent protein kinase by gefitinib may be due to the synergistic mechanism between gefitinib and cisplatin. Thus, the present study provides a novel insight into potential biomarkers for the selection of combination therapy of gefitinib and cisplatin.

Selection of Non-small Cell Lung Cancer Patients for Intercalated Chemotherapy and Tyrosine Kinase Inhibitors

BACKGROUND

When treating patients with advanced non-small cell lung cancer (NSCLC) with tyrosine kinase inhibitors and chemotherapy, intercalated schedule with time separation between the two classes of drugs should avoid their mutual antagonism. In a survey of published trials, we focus on relation between eligibility criteria and effectiveness of intercalated treatment.

METHODS

Published documents were identified using major medical databases, conference proceedings and references of published trials. Median progression-free survival (PFS) was taken as the basic parameter of treatment efficacy. Correlation between characteristics of patients and median PFS was assessed through the Pearson's correlation coefficient and the coefficient of determination, separately for first-line and second-line setting.

RESULTS

The series includes 11 single-arm trials and 18 randomized phase II or phase III trials with a total of 2903 patients. Treatment-naive patients or those in progression after first-line treatment were included in 16 and 13 trials, respectively. In 14 trials, only patients with non-squamous histology were eligible. Proportion of patients with non-squamous carcinoma (in first-line setting), proportion of never-smokers (both in first- and second-line setting) and proportion of epidermal growth factor receptor (EGFR) mutant patients (both in first- and second-line setting) showed a moderate or strong correlation with median PFS. In six trials of intercalated treatment applied to treatment-naive EGFR-mutant patients, objective response was confirmed in 83.1% of cases and median PFS was 18.6 months.

CONCLUSIONS

Most suitable candidates for intercalated treatment are treatment-naive patients with EGFR-mutant tumors, as determined from biopsy or liquid biopsy. For these patients, experience with intercalated treatment is most promising and randomized trials with comparison to the best standard treatment are warranted.

Intercalated Chemotherapy and Epidermal Growth Factor Receptor Inhibitors for Patients With Advanced Non-Small-cell Lung Cancer: A Systematic Review and Meta-analysis

Randomized clinical trials (RCTs) of concurrent epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) plus chemotherapy for unselected patients with advanced non-small-cell lung cancer (NSCLC) produced negative results. Intercalated administration could avoid the reduction of chemotherapy activity due to G₁ cell-cycle arrest from EGFR-TKIs. A PubMed search was performed in December 2015 and updated in February 2016. The references from the selected studies were also checked to identify additional eligible trials. Furthermore, the proceedings of the main international meetings were searched from 2010 onward. We included RCTs comparing chemotherapy intercalated with an EGFR-TKI versus chemotherapy alone for patients with advanced NSCLC. Ten RCTs were eligible (6 with erlotinib, 4 with gefitinib): 39% of patients had a known EGFR mutational status, 43% of whom EGFR mutation positive. The intercalated combination was associated with a significant improvement in overall survival (OS; hazard ratio [HR], 0.82; 95% confidence interval [CI], 0.71-0.95; P = .01), progression-free survival (PFS; HR, 0.60; 95% CI, 0.53-0.68; P < .00001), and objective response rate (ORR; odds ratio [OR], 2.70; 95% CI, 2.08-3.49; P < .00001). Considering only first-line trials, similar differences were found in OS (HR, 0.85; 95% CI, 0.72-1.00; P = .05), PFS (HR, 0.63; 95% CI, 0.55-0.73; P < .00001), and ORR (OR, 2.21; 95% CI, 1.65-2.95; P < .00001). In EGFR mutation-positive patients, the addition of an intercalated EGFR-TKI produced a significant benefit in PFS (129 patients; HR, 0.24; 95% CI, 0.16-0.37; P < .00001) and ORR (168 patients; OR, 11.59; 95% CI, 5.54-24.25; P < .00001). In patients with advanced NSCLC, chemotherapy plus intercalated EGFR-TKIs was superior to chemotherapy alone, although a definitive interpretation was jeopardized by the variable proportion of patients with EGFR mutation-positive tumors included.