Establishment of three cisplatin-resistant endometrial cancer cell lines using two methods of cisplatin exposure

Spontaneous Cell Detachment and Reattachment in Cancer Cell Lines: An In Vitro Model of Metastasis and Malignancy

There is an unmet need for simplified in vitro models of malignancy and metastasis that facilitate fast, affordable and scalable gene and compound analysis. "Adherent" cancer cell lines frequently release "free-floating" cells into suspension that are viable and can reattach. This, in a simplistic way, mimics the metastatic process. We compared the gene expression profiles of naturally co-existing populations of floating and adherent cells in SW620 (colon), C33a (cervix) and HeLa (cervix) cancer cells. We found that 1227, 1367 and 1333 genes were at least 2-fold differentially expressed in the respective cell lines, of which 122 were shared among the three cell lines. As proof of principle, we focused on the anti-metastatic gene NM23-H1, which was downregulated both at the RNA and protein level in the floating cell populations of all three cell lines. Knockdown of NM23-H1 significantly increased the number of floating (and viable) cells, whereas overexpression of NM23-H1 significantly reduced the proportion of floating cells. Other potential regulators of these cellular states were identified through pathway analysis, including hypoxia, mTOR (mechanistic target of rapamycin), cell adhesion and cell polarity signal transduction pathways. Hypoxia, a condition linked to malignancy and metastasis, reduced NM23-H1 expression and significantly increased the number of free-floating cells. Inhibition of mTOR or Rho-associated protein kinase (ROCK) significantly increased cell death specifically in the floating and not the adherent cell population. In conclusion, our study suggests that dynamic subpopulations of free-floating and adherent cells is a useful model to screen and identify genes, drugs and pathways that regulate the process of cancer metastasis, such as cell detachment and anoikis.

Activation of AXL as a Preclinical Acquired Resistance Mechanism Against Osimertinib Treatment in EGFR-Mutant Non-Small Cell Lung Cancer Cells

Osimertinib (AZD9291) has an efficacy superior to that of standard EGFR-tyrosine kinase inhibitors for the first-line treatment of patients with EGFR-mutant advanced non-small cell lung cancer (NSCLC). However, patients treated with osimertinib eventually acquire drug resistance, and novel therapeutic strategies to overcome acquired resistance are needed. In clinical or preclinical models, several mechanisms of acquired resistance to osimertinib have been elucidated. However, the acquired resistance mechanisms when osimertinib is initially used for EGFR-mutant NSCLC remain unclear. In this study, we experimentally established acquired osimertinib-resistant cell lines from EGFR-mutant NSCLC cell lines and investigated the molecular profiles of resistant cells to uncover the mechanisms of acquired resistance. Various resistance mechanisms were identified, including the acquisition of MET amplification, EMT induction, and the upregulation of AXL. Using targeted next-generation sequencing with a multigene panel, no secondary mutations were detected in our resistant cell lines. Among three MET-amplified cell lines, one cell line was sensitive to a combination of osimertinib and crizotinib. Acquired resistance cell lines derived from H1975 harboring the T790M mutation showed AXL upregulation, and the cell growth of these cell lines was suppressed by a combination of osimertinib and cabozantinib, an inhibitor of multiple tyrosine kinases including AXL, both in vitro and in vivo. Our results suggest that AXL might be a therapeutic target for overcoming acquired resistance to osimertinib. IMPLICATIONS: Upregulation of AXL is one of the mechanisms of acquired resistance to osimertinib, and combination of osimertinib and cabozantinib might be a key treatment for overcoming osimertinib resistance.

Establishing Dual Resistance to EGFR-TKI and MET-TKI in Lung Adenocarcinoma Cells In Vitro with a 2-step Dose-escalation Procedure

Drug resistance is a major challenge in cancer therapy. The generation of resistant sublines in vitro is necessary for discovering novel mechanisms to overcome this challenge. Here, a 2-step dose-escalation method for establishing dual-resistance to an epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI), gefitinib, and a MET-TKI, PHA665752, is described. This method is based on simple stepwise dose-escalation of inhibitors for inducing acquired resistance in cell lines. The alternate method for generating resistant sublines involves exposing the cells to high concentrations of the inhibitor in one step. The stepwise dose-escalation method has a higher possibility of successfully inducing acquired resistance than this method. Activating EGFR mutations are biomarkers of a response to treatment with EGFR-TKI, which is an applied first-line treatment for non-small cell lung cancers (NSCLC) that harbor these mutations. However, despite reports of effective responses, the use of EGFR-TKI is limited because tumors inevitably acquire resistance. The major mechanisms behind EGFR-TKI resistance include a secondary mutation at the gatekeeper site, T790M in exon 20 of EGFR, and a bypass signal of MET. Thus, a potential solution for this issue would be a combination of EGFR-TKI and MET-TKI. This combined treatment has been shown to be effective in an in vitro study model. Acquired gefitinib-resistance was established through MET-amplification by stepwise dose-escalation of gefitinib for 12 months, and a cell line named PC-9MET1000 was generated in a previous study. To further investigate the mechanisms of acquired MET-TKI and EGFR-TKI resistance, a MET-TKI, PHA665752, was administered to these cells with stepwise dose-escalation in the presence of gefitinib for 12 months. This protocol has also been successfully applied for a number of combination therapies to establish acquired resistance to other inhibitor molecules.

Hematologic malignancies: newer strategies to counter the BCL-2 protein

INTRODUCTION

BCL-2 is the founding member of the BCL-2 family of apoptosis regulatory proteins that either induce (pro-apoptotic) or inhibit (anti-apoptotic) apoptosis. The anti-apoptotic BCL-2 is classified as an oncogene, as damage to the BCL-2 gene has been shown to cause a number of cancers, including lymphoma. Ongoing research has demonstrated that disruption of BCL-2 leads to cell death. BCL-2 is also known to be involved in the development of resistance to chemotherapeutic agents, further underscoring the importance of targeting the BCL-2 gene in cancer therapeutics. Thus, numerous approaches have been developed to block or modulate the production of BCL-2 at the RNA level using antisense oligonucleotides or at the protein level with BCL-2 inhibitors, such as the novel ABT737.

METHODS

In this article, we briefly review previous strategies to target the BCL-2 gene and focus on a new approach to silence DNA, DNA interference (DNAi).

RESULTS AND CONCLUSION

DNA interference is aimed at blocking BCL-2 gene transcription. Evaluations of this technology in preclinical and early clinical studies are very encouraging and strongly support further development of DNAi as cancer therapeutics. A pilot phase II clinical trial in patients with relapsed or refractory non-Hodgkin lymphoma, PNT2258 demonstrated clinical benefit in 11 of 13 patients with notable responses in diffuse large B cell lymphoma and follicular lymphoma. By targeting the DNA directly, the DNAi technology promises to be more effective compared with other gene-interference strategies that target the RNA or protein but leaves the dysregulated DNA functional.

TALEN-mediated Nanog disruption results in less invasiveness, more chemosensitivity and reversal of EMT in Hela cells

Emerging evidence suggests that Nanog is involved in cervical tumorigenesis. However, the regulating role of Nanog in tumorigenesis and chemosensitivity are still poorly understood. In this study, Nanog was disrupted by transcription activatorlike effector nucleases (TALEN) in Hela cells and its expression was significantly decreased in a single-cell derived sub-clone with biallelic mutations. The disruption of Nanog not only induced down regulation of some other core transcription factor genes for cell self-renewal, such as Oct4, Sox2 and FoxD3, but also led to the down regulation of some mesenchymal representative genes, vimentin and N-adherin, and up regulation of the epithelial gene, E-cadherin. In addition, the invasiveness and clonogenicity of the Hela cells were obviously affected, and surprisingly their sensitivities to anti-cancer drugs were also significantly increased in vitro. After Xenograft into nude mice, the growth volumes of the neoplasms from the Nanog disrupted Hela cells were significantly smaller compared with those from wild type ones. In conclusion, these results suggest that disruption of Nanog may reverse the status of epithelial-mesenchymal transition, which is critical in tumorigenesis, and alleviate chemoresistance, as well as their invasiveness, in cervical cancer cells.

Biological relevance of Hsp90-binding immunophilins in cancer development and treatment

Immunophilins are a family of intracellular receptors for immunosuppressive drugs. Those immunophilins that are related to immunosuppression are the smallest proteins of the family, i.e., FKBP12 and CyPA, whereas the other members of the family have higher molecular weight because the show additional domains to the drug-binding site. Among these extra domains, the TPR-domain is perhaps the most relevant because it permits the interaction of high molecular weight immunophilins with the 90-kDa heat-shock protein, Hsp90. This essential molecular chaperone regulates the biological function of several protein-kinases, oncogenes, protein phosphatases, transcription factors and cofactors . Hsp90-binding immunophilins where first characterized due to their association with steroid receptors. They regulate the cytoplasmic transport and the subcellular localization of these and other Hsp90 client proteins, as well as transcriptional activity, cell proliferation, cell differentiation and apoptosis. Hsp90-binding immunophilins are frequently overexpressed in several types of cancers and play a key role in cell survival. In this article we analyze the most important biological actions of the best characterized Hsp90-binding immunophilins in both steroid receptor function and cancer development and discuss the potential use of these immunophilins for therapeutic purposes as potential targets of specific small molecules.

Metadherin confers chemoresistance of cervical cancer cells by inducing autophagy and activating ERK/NF-κB pathway

Overexpression of metadherin (MTDH) has been reported in many solid tumors and implicated in chemoresistance. This study aimed to examine MTDH expression in cervical cancer tissues and explore its role in chemoresistance of cervical cancer. MTDH expression in cervical cancer biopsies and several cervical cancer cell lines was detected by immunoblotting and immunohistochemisty. MTDH expression level was experimentally modulated in HeLa cells to determine the effects on chemoresistance to cisplatin. The results showed that MTDH expression was higher in tissues from both cervical squamous carcinoma and cervical adenocarcinoma, compared to normal cervical tissues. MTDH expression was not correlated to patient age or cervical cancer grade, although nuclear MTDH expression was correlated with poor differentiation of cervical cancer. In SiHa, HeLa, CasKi, and C33A cells, MTDH expression level was positively correlated with chemoresistance to cisplatin. MTDH increased autophagy in HeLa cells, which was associated with decreased cleavage of Caspase-3 and the activation of EER/NF-κB pathway. In conclusion, MTDH expression is high in cervical cancer, and it contributes to chemoresistance of cervical cancer. MTDH could be utilized as a therapeutic target to overcome chemoresistance of cervical cancer.

Acquired resistance to EGFR inhibitors is associated with a manifestation of stem cell-like properties in cancer cells

Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI) is a critical problem in the treatment of lung cancer. Although several mechanisms have been shown to be responsible for acquired resistance, all mechanisms have not been uncovered. In this study, we investigated the molecular and cellular profiles of the acquired resistant cells to EGFR-TKI in EGFR-mutant lung cancers. Four EGFR-mutant cell lines were exposed to gefitinib by stepwise escalation and high-concentration exposure methods, and resistant sublines to gefitinib were established. The molecular profiles and cellular phenotypes of these resistant sublines were characterized. Although previously reported, alterations including secondary EGFR T790M mutation, MET amplification, and appearance of epithelial-to-mesenchymal transition (EMT) features were observed, these 2 drug-exposure methods revealed different resistance mechanisms. The resistant cells with EMT features exhibited downregulation of miRNA-200c by DNA methylation. Furthermore, the HCC827-derived subline characterized by the high-concentration exposure method exhibited not only EMT features but also stem cell-like properties, including aldehyde dehydrogenase isoform 1 (ALDH1A1) overexpression, increase of side-population, and self-renewal capability. Resistant sublines with stem cell-like properties were resistant to conventional chemotherapeutic agents but equally sensitive to histone deacetylase and proteasome inhibitors, compared with their parental cells. ALDH1A1 was upregulated in clinical samples with acquired resistance to gefitinib. In conclusion, our study indicates that the manner of EGFR-TKI exposure influences the mechanism of acquired resistance and the appearance of stem cell-like property with EGFR-TKI treatment.

FKBP38-Bcl-2 interaction: a novel link to chemoresistance

FKBP38, a noncanonical member of the immunosuppressive drug FK506 binding protein (FKBP) family members, possesses an inducible rotamase. FKBP38 interacts with several proteins and regulates multiple signaling pathways such as cell survival, apoptosis, proliferation, and metastasis. Deregulation of apoptosis is associated with chemoresistance and tumor relapse. The antiapoptotic protein Bcl-2 is a key player for increasing the apoptotic threshold in response to various cytotoxic drugs. The molecular interaction of Bcl-2 with FKBP38 potentiates the biological function of Bcl-2 and contributes to tumorigenesis and chemoresistance. Here, we discuss recent advances in the role of FKBP38 in connection with Bcl-2 and its possible link to chemotherapeutic resistance.