The maintenance of highly proliferative capacity and full differentiation potential is a necessary step in the initiation of stem cell-based regenerative medicine. Our recent study showed that epidermal growth factor (EGF) significantly enhanced hair follicle-derived mesenchymal stem cell (HF-MSC) proliferation while maintaining the multilineage differentiation potentials. However, the underlying mechanism remains unclear. Herein, we investigated the role of EGF in HF-MSC proliferation. HF-MSCs were isolated and cultured with or without EGF. Immunofluorescence staining, flow cytometry, cytochemistry, and western blotting were used to assess proliferation, cell signaling pathways related to the EGF receptor (EGFR), and cell cycle progression. HF-MSCs exhibited surface markers of mesenchymal stem cells and displayed trilineage differentiation potentials toward adipocytes, chondrocytes, and osteoblasts. EGF significantly increased HF-MSC proliferation as well as EGFR, ERK1/2, and AKT phosphorylation (p-EGFR, p-ERK1/2, and p-AKT) in a time- and dose-dependent manner, but not STAT3 phosphorylation. EGFR inhibitor (AG1478), PI3K-AKT inhibitor (LY294002), ERK inhibitor (U0126), and STAT3 inhibitor (STA-21) significantly blocked EGF-induced HF-MSC proliferation. Moreover, AG1478, LY294002, and U0126 significantly decreased p-EGFR, p-AKT, and p-ERK1/2 expression. EGF shifted HF-MSCs at the G1 phase to the S and G2 phase. Concomitantly, cyclinD1, phosphorylated Rb, and E2F1expression increased, while that of p16 decreased. In conclusion, EGF induces HF-MSC proliferation through the EGFR/ERK and AKT pathways, but not through STAT-3. The G1/S transition was stimulated by upregulation of cyclinD1 and inhibition of p16 expression.

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Background: The efficacy of next-generation epidermal growth factor receptor-tyrosine kinase inhibitors in patients with advanced non-small cell lung cancer who have failed first-generation epidermal growth factor receptor-tyrosine kinase inhibitors still remains under investigation. Objective: The aim of this meta-analysis was to systematically assess the efficacy and safety profiles of next-generation epidermal growth factor receptor-tyrosine kinase inhibitors in patients with advanced non-small cell lung cancer who failed first-generation epidermal growth factor receptor-tyrosine kinase inhibitors. Methods: We performed a comprehensive search of several electronic databases up to September 2018 to identify clinical trials. The primary end point was overall survival, progression-free survival, disease controlled rate, objective response rate, and adverse events. Epidermal growth factor receptor-tyrosine kinase inhibitor emergent severe adverse events (grade ≥ 3) were analyzed. Odds ratio along with 95% confidence interval were utilized for main outcome analysis. Results: In total, we had 3 randomized controlled trials in this analysis. The group of next-generation epidermal growth factor receptor-tyrosine kinase inhibitors had significantly improved progression-free survival (odds ratio = 0.34, 95% confidence interval = 0.29-0.40, P < .00001), as well as objective response rate (odds ratio = 10.48, 95% confidence interval = 3.87-28.34, P < .00001) and disease controlled rate (odds ratio = 6.03, 95% confidence interval = 4.41-8.25, P < .00001). However, there was no significant difference in overall survival with next-generation epidermal growth factor receptor-tyrosine kinase inhibitors (odds ratio = 1.05, 95% confidence interval = 0.85-1.31, P = .66). Meanwhile, the odds ratio for treatment-emergent severe adverse events (diarrhea, rash/acne, nausea, vomiting, anemia) between patients who received next-generation epidermal growth factor receptor-tyrosine kinase inhibitors and those who received first-generation epidermal growth factor receptor-tyrosine kinase inhibitors did not show safety benefit ( P > .05). Conclusions: Next-generation epidermal growth factor receptor-tyrosine kinase inhibitors were shown to be the better agent to achieve higher response rate and longer progression-free survival in patients with non-small cell lung cancer as the later-line therapy for previously treated patients with first-generation epidermal growth factor receptor-tyrosine kinase inhibitors. Meanwhile, they did not achieve benefit in overall survival and safety compared with the chemotherapy group. Further research is needed to develop a database of all EGFR mutations and their individual impacts on the various treatments.