Epithelial-mesenchymal transition (EMT): A biological process in the development, stem cell differentiation, and tumorigenesis

Reverse epithelial-mesenchymal transition contributes to the regain of drug sensitivity in tyrosine kinase inhibitor-resistant non-small cell lung cancer cells

Tyrosine kinase inhibitors (TKIs) are currently the first-line treatment for non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations. These patients receive platinum-based chemotherapy as the second-line treatment after they develop resistance to TKIs. Many patients regain sensitivity to the TKIs used in the first-line treatment after the failure of chemotherapy. However, the molecular mechanism for the regain of TKI sensitivity is largely unknown. In this study, we established gefitinib-resistant PC9 and HCC827 cell lines, which did not harbor the EGFR T790M mutation and MET amplification but exhibited the epithelial-mesenchymal transition (EMT) phenotype. Overexpression of EMT inducers, Snail or Slug, in the parental lines promoted their resistance to gefitinib. The gefitinib-resistant cell lines regained their sensitivity to gefitinib and displayed reverse EMT phenotypes after long-term culture in gefitinib-free culture medium. Blockage of reverse EMT by stable expression of Snail or Slug prevented the regain of TKI sensitivity. In conclusion, reverse EMT is one of the major mechanisms for the regain of TKI sensitivity in TKI-resistant NSCLC cells, suggesting that the development of small molecules targeting the EMT process may prolong the efficacy of TKIs in NSCLC patients with EGFR mutations.

Breast Cancer Stem Cell Therapeutics, Multiple Strategies Versus Using Engineered Mesenchymal Stem Cells With Notch Inhibitory Properties: Possibilities and Perspectives

Relapse cases of cancers are more vigorous and difficult to control due to the preponderance of cancer stem cells (CSCs). Such CSCs that had been otherwise dormant during the first incidence of cancer gradually appear as radiochemoresistant cancer cells. Hence, cancer therapeutics aimed at CSCs would be an effective strategy for mitigating the cancers during relapse. Alternatively, CSC therapy can also be proposed as an adjuvant therapy, along-with the conventional therapies. As regenerative stem cells (RSCs) are known for their trophic effects, anti-tumorogenicity, and better migration toward an injury site, this review aims to address the use of adult stem cells such as dental pulp derived; cord blood derived pure populations of regenerative stem cells for targeting CSCs. Indeed, pro-tumorogenicity of RSCs is of concern and hence has also been dealt with in relation to breast CSC therapeutics. Furthermore, as notch signaling pathways are upregulated in breast cancers, and anti-notch antibody based and sh-RNA based therapies are already in the market, this review focuses the possibilities of engineering RSCs to express notch inhibitory proteins for breast CSC therapeutics. Also, we have drawn a comparison among various possibilities of breast CSC therapeutics, about, notch1 inhibition. J. Cell. Biochem. 119: 141-149, 2018. © 2017 Wiley Periodicals, Inc.

HO-1 Induction in Cancer Progression: A Matter of Cell Adaptation

The upregulation of heme oxygenase-1 (HO-1) is one of the most important mechanisms of cell adaptation to stress. Indeed, the redox sensitive transcription factor Nrf2 is the pivotal regulator of HO-1 induction. Through the antioxidant, antiapoptotic, and antinflammatory properties of its metabolic products, HO-1 plays a key role in healthy cells in maintaining redox homeostasis and in preventing carcinogenesis. Nevertheless, several lines of evidence have highlighted the role of HO-1 in cancer progression and its expression correlates with tumor growth, aggressiveness, metastatic and angiogenetic potential, resistance to therapy, tumor escape, and poor prognosis, even though a tumor- and tissue-specific activity has been observed. In this review, we summarize the current literature regarding the pro-tumorigenic role of HO-1 dependent tumor progression as a promising target in anticancer strategy.

Soil Primes the Seed: Epigenetic Landscape Drives Tumor Behavior

Whether invasive tumor phenotypes like EMT arise from oncogenic drivers or from priming of the pre-tumor cell of origin remains unknown. In this issue of Cell Stem Cell, Latil et al. (2017) show that the pre-tumor niche establishes a chromatin state predisposing squamous cell carcinomas to undergo EMT and metastasis, suggesting that the pre-tumor epigenome has prognostic value.