Epidermal growth factor signals regulate dihydropyrimidine dehydrogenase expression in EGFR-mutated non-small-cell lung cancer

BACKGROUND

It has been shown that epidermal growth factor receptor (EGFR) mutation status is associated with 5-fluorouracil (5-FU) sensitivity in non-small-cell lung cancer (NSCLC). However, the relationship between EGFR mutation status and dihydropyrimidine dehydrogenase (DPD), a 5-FU degrading enzyme, is unknown.

METHODS

We elucidated the crosstalk among the EGFR signal cascade, the DPD gene (DPYD), and DPD protein expression via the transcription factor Sp1 and the effect of EGFR mutation status on the crosstalk.

RESULTS

In the PC9 (exon19 E746-A750) study, EGF treatment induced up-regulation of both Sp1 and DPD; gefitinib, an EGFR-tyrosine kinase inhibitor (EGFR-TKI), and mithramycin A, a specific Sp-1 inhibitor, suppressed them. Among EGFR-mutated (PC9, HCC827; exon19 E746-A750 and H1975; exon21 L858R, T790M, gefitinib resistant) and -non-mutated (H1437, H1299) cell lines, EGF administration increased DPYD mRNA expression only in mutated cells (p < 0.05). Accordingly, gefitinib inhibited DPD protein expression only in PC9 and HCC827 cells, and mithramycin A inhibited it in EGFR-mutated cell lines, but not in wild-type. FU treatment decreased the level of cell viability more in gefitinib-treated EGFR-TKI sensitive cell lines. Further, combination treatment of FU and mithramycin A suppressed cell viability even in a gefitinib resistant cell line.

CONCLUSIONS

The EGFR signal cascade regulates DPD expression via Sp1 in EGFR mutant cells. These results might be a step towards new therapies targeting Sp1 and DPD in NSCLC with different EGFR mutant status.

Reciprocal and complementary role of MET amplification and EGFR T790M mutation in acquired resistance to kinase inhibitors in lung cancer

PURPOSE

In epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapy for lung cancer patients, acquired resistance develops almost inevitably and this limits the improvement in patient outcomes. EGFR T790M mutation and MET amplification are the two main mechanisms underlying this resistance, but the relationship between these two mechanisms is unclear. In this study, we explored their relationship using in vitro models and autopsy specimens.

EXPERIMENTAL DESIGN

Erlotinib-resistant HCC827 (HCC827ER) cells were developed by chronic exposure to erlotinib at increasing concentrations. HCC827EPR cells were also developed by chronic exposure to erlotinib in the presence of PHA-665,752 (a MET TKI). The erlotinib-resistant mechanisms of these cells were analyzed. In addition, 33 autopsy tumor samples from 6 lung adenocarcinoma patients harboring multiple gefitinib-refractory tumors were analyzed.

RESULTS

HCC827ER developed MET amplification, and clinically relevant resistance occurred at ≥4-fold MET gene copy number gain (CNG). By contrast, HCC827EPR developed T790M without MET CNG. Of six patients harboring gefitinib-refractory tumors, three exhibited T790M only, one exhibited MET amplification only, and the other two exhibited T790M and/or MET amplification depending on the lesion sites. In these gefitinib-refractory tumors, T790M developed in 93% (14 of 15) of tumors without MET gene CNGs, in 80% (4 of 5) of tumors with moderate MET gene CNGs (<4-fold), and in only 8% (1 of 13) of tumors with MET amplification (≥4-fold).

CONCLUSIONS

These results indicate a reciprocal and complementary relationship between T790M and MET amplification and the necessity of concurrent inhibition of both for further improving patient outcomes.

Recent development of molecular-targeted drugs in lung cancer

Numerous molecular target drugs have been introduced for the treatment of advanced malignancies. In the treatment of lung cancer, epidermoid growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) demonstrate striking antitumor activity in selected EGFR mutation positive patients. Patient selection by biomarker is extremely important to obtain successful results. The anti-vascular endothelial growth factor (VEGF) antibody, bevacizumab, shows a markedly increased response rate, progression free survival of advanced non-squamous cell lung cancer when combined with cytotoxic drugs. The classification of lung cancer is rapidly changing based on the advances in molecular biology. Here, the recent development of new molecular target drugs against lung cancer is thoroughly reviewed in addition to EGFR-TKIs and bevacizumab with special emphasis on the clinical application.