Inhibition of miR-23a increases the sensitivity of lung cancer stem cells to erlotinib through PTEN/PI3K/Akt pathway

Somatic mutations in the epidermal growth factor receptor (EGFR) correlate with increased response in patients with non-small-cell lung cancer (NSCLC) treated with EGFR tyrosine kinase inhibitors (TKIs). The multicenter iTARGET trial prospectively examined first-line gefitinib in advanced NSCLC patients harboring EGFR mutations and explored the significance of EGFR mutation subtypes and TKI resistance mechanisms. Chemotherapy-naïve patients with advanced NSCLC with >or= 1 clinical characteristic associated with EGFR mutations underwent direct DNA sequencing of tumor tissue EGFR exons 18 to 21. Patients found to harbor any EGFR mutation were treated with gefitinib 250 mg/d until progression or unacceptable toxicity. The primary outcome was response rate. Ninety-eight patients underwent EGFR screening and mutations were detected in 34 (35%). EGFR mutations were primarily exon 19 deletions (53%) and L858R (26%) though 21% of mutation-positive cases had less common subtypes including exon 20 insertions, T790M/L858R, G719A, and L861Q. Thirty-one patients received gefitinib. The response rate was 55% (95% CI, 33 to 70) and median progression-free survival was 9.2 months (95% CI, 6.2 to 11.8). Therapy was well tolerated; 13% of patients had grade 3 toxicities including one grade 3 pneumonitis. Two patients with classic activating mutations exhibited de novo gefitinib resistance and had concurrent genetic anomalies usually associated with acquired TKI resistance, specifically the T790M EGFR mutation and MET amplification. First-line therapy with gefitinib administered in a genotype-directed fashion to patients with advanced NSCLC harboring EGFR mutations results in very favorable clinical outcomes with good tolerance. This strategy should be compared with combination chemotherapy, the current standard of care.

In patients with non-small cell lung cancer (NSCLC), mutations in the epidermal growth factor receptor (EGFR) tyrosine kinase domain have been associated with sensitivity to erlotinib and gefitinib. We undertook this study to explore the relationship between EGFR mutation type and clinical variables, including treatment with gefitinib and erlotinib. In patients with NSCLC, EGFR exon 19 deletion mutations and EGFR L858R point mutations were analyzed by nonsequencing PCR-based methods from paraffin blocks of tissue obtained before treatment. The results were correlated with clinical information (sex, pathologic subtype, race/ethnicity, treatment, and overall survival). The two most common EGFR mutations were identified in 24% (70 of 291; 95% confidence interval, 26%-38%) of tumors from patients with NSCLC. EGFR mutation was associated with Asian ethnicity (P = 0.0023) and being a "never smoker" (P = 0.0001). Among patients with EGFR mutations, 39% (27 of 70) had EGFR L858R, whereas 61% (43 of 70) had an EGFR exon 19 deletion. After treatment with erlotinib (n = 12) or gefitinib (n = 22), patients with EGFR mutations had a median overall survival of 20 months. After treatment with erlotinib or gefitinib, patients with EGFR exon 19 deletions had significantly longer median survival than patients with EGFR L858R (34 versus 8 months; log-rank P = 0.01). EGFR mutations in exons 19 or 21 are correlated with clinical factors predictive of response to gefitinib and erlotinib. Those with EGFR exon 19 deletion mutations had a longer median survival than patients with EGFR L858R point mutation. These observations warrant confirmation in a prospective study and exploration of the biological mechanisms of the differences between the two major EGFR mutations.

Despite its prevalence, the molecular basis of squamous cell carcinoma (SCC) remains poorly understood. Here, we identify the developmental transcription factor Grhl3 as a potent tumor suppressor of SCC in mice, and demonstrate that targeting of Grhl3 by a miR-21-dependent proto-oncogenic network underpins SCC in humans. Deletion of Grhl3 in adult epidermis evokes loss of expression of PTEN, a direct GRHL3 target, resulting in aggressive SCC induced by activation of PI3K/AKT/mTOR signaling. Restoration of Pten expression completely abrogates SCC formation. Reduced levels of GRHL3 and PTEN are evident in human skin, and head and neck SCC, associated with increased expression of miR-21, which targets both tumor suppressors. Our data define the GRHL3-PTEN axis as a critical tumor suppressor pathway in SCC. 2011 Elsevier Inc. All rights reserved.