Resistance to gefitinib and cross-resistance to irreversible EGFR-TKIs mediated by disruption of the Keap1-Nrf2 pathway in human lung cancer cells.

The development of resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) occurs by various mechanisms and appears to be almost inevitable, even in patients with lung cancer who initially respond well to EGFR-TKIs. Consequently, considerable efforts have been made to develop more effective EGFR-TKIs. Therefore, an understanding of the mechanisms behind TKI resistance is essential for improving EGFR-TKI therapeutic efficacy in non-small cell lung cancer (NSCLC) patients. In this study, we discovered that overexpression of antioxidant-responsive element (ARE)-containing Nrf2 target genes by increased transactivation of Nrf2 occurred because of an acquired Keap1 mutation in the gefitinib-resistant (GR) NSCLC cell line we established. These GR cells also acquired cross-resistance to the irreversible EGFR-TKIs, afatinib and osimertinib, and showed increased viability, invasiveness, proliferation, and tumorigenicity both in vitro and in vivo. These results were confirmed by the fact that inhibition of Nrf2 activity, either by treatment with brusatol or by inducing expression of exogenously introduced wild-type Keap1, suppressed tumor cell proliferation and tumorigenicity in vitro and in vivo. Our data suggest that disruption of the Keap1-Nrf2 pathway is one of the mechanisms by which EGFR-TKI resistance occurs, a fact that must be considered when treating patients with EGFR-TKI.-Park, S.-H., Kim, J. H., Ko, E., Kim, J.-Y., Park, M.-J., Kim, M. J., Seo, H., Li, S., Lee, J.-Y. Resistance to gefitinib and cross-resistance to irreversible EGFR-TKIs mediated by disruption of the Keap1-Nrf2 pathway in human lung cancer cells.

Nrf2 regulates cell motility through RhoA-ROCK1 signalling in non-small-cell lung cancer cells.

Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key transcriptional regulator of several antioxidant and anti-inflammatory enzymes. It binds to its endogenous inhibitor Kelch-like ECH-associated protein 1 (Keap1) in the cytoplasm under normal conditions. Various endogenous or environmental oxidative stresses can disrupt the Nrf2/Keap1 complex, allowing Nrf2 to translocate into the nucleus, where it induces the transcription of various cytoprotective enzymes by binding to antioxidant responsive elements. These enzymes have been reported to play a role in regulating tumour growth, angiogenesis, and chemoprevention. Invasion and migration are the most harmful aspects of cancer; they directly impacts the patients' survival. Although the roles of Keap1/Nrf2 and their downstream genes in various cancers have been widely documented, their role in regulating cell motility still remains unclear, particularly in cancer cells. We observed that Nrf2 suppression following treatment with brusatol in non-small-cell lung cancer (NSCLC) cells with either exogenously introduced Keap1 or siNrf2 resulted in the inhibition of cell migration and invasion, with shrinking cell morphology due to decreased focal adhesions via inhibition of the RhoA-ROCK1 pathway. Nrf2 overexpression showed opposite results. Thus, the Nrf2/Keap1 pathway may affect cell motility by dysregulating the RhoA-ROCK1 signalling pathway in NSCLC.

Glucose-stimulated insulin secretion of various mesenchymal stem cells after insulin-producing cell differentiation.

Mesenchymal stem cells (MSCs) are capable of crossing germinative layer borders and are obtainable in high numbers via in vitro cultures. Therefore, many researchers have searched for diverse sources of MSCs. Recently the generation of glucose-responsive insulin-producing cells (IPCs) from MSCs has shown immense potential for the treatment of type 1 diabetes mellitus (T1DM) due to a lack of pancreas donors. In this study, we compared the growth potency of four kinds of MSCs derived from bone marrow, Wharton's jelly, adipose tissue, and the periosteum. In addition, in vitro differentiation of these MSCs into IPCs was also investigated. After 2weeks of IPCs differentiation, we compared the expression of the insulin gene and protein using RT-qPCR and immunofluorescence staining. Only IPCs derived from periosteum-derived progenitor cells (PDPCs) showed a response to glucose concentration. Glucose stimulated insulin secretion was conclusive evidence of the potential functionality of IPCs. Therefore, PDPCs are a promising alternative stem cell source for IPCs differentiation.