Oct4 plays a crucial role in the maintenance of gefitinib-resistant lung cancer stem cells

Inhibitory Effect and Mechanism of Ursolic Acid on Cisplatin-Induced Resistance and Stemness in Human Lung Cancer A549 Cells

The survival rate of lung cancer patients remains low largely due to chemotherapy resistance during treatment, and cancer stem cells (CSCs) may hold the key to targeting this resistance. Cisplatin is a chemotherapy drug commonly used in cancer treatment, yet the mechanisms of intrinsic cisplatin resistance have not yet been determined because lung CSCs are hard to identify. In this paper, we proposed a mechanism relating to the function of ursolic acid (UA), a new drug, in reversing the cisplatin resistance of lung cancer cells regulated by CSCs. Human lung cancer cell line A549 was selected as the model cell and treated to become a cisplatin-resistant lung cancer cell line (A549-CisR), which was less sensitive to cisplatin and showed an enhanced capability of tumor sphere formation. Furthermore, in the A549-CisR cell line expression, levels of pluripotent stem cell transcription factors Oct-4, Sox-2, and c-Myc were increased, and activation of the Jak2/Stat3 signaling pathway was promoted. When UA was applied to the cisplatin-resistant cells, levels of the pluripotent stem cell transcription factors were restrained by the inhibition of the Jak2/Stat3 signaling pathway, which reduced the enrichment of tumor stem cells, and in turn, reversed cisplatin resistance in lung cancer cells. Hence, as a potential antitumor drug, UA may be able to inhibit the enrichment of the lung CSC population by inhibiting the activation of the Jak2-Stat3 pathway and preventing the resistance of lung cancer cells to cisplatin.

Inside the stemness engine: Mechanistic links between deregulated transcription factors and stemness in cancer

Cell identity is largely determined by its transcriptional profile. In tumour, deregulation of transcription factor expression and/or activity enables cancer cell to acquire a stem-like state characterised by capacity to self-renew, differentiate and form tumours in vivo. These stem-like cancer cells are highly metastatic and therapy resistant, thus warranting a more complete understanding of the molecular mechanisms downstream of the transcription factors that mediate the establishment of stemness state. Here, we review recent research findings that provide a mechanistic link between the commonly deregulated transcription factors and stemness in cancer. In particular, we describe the role of master transcription factors (SOX, OCT4, NANOG, KLF, BRACHYURY, SALL, HOX, FOX and RUNX), signalling-regulated transcription factors (SMAD, β-catenin, YAP, TAZ, AP-1, NOTCH, STAT, GLI, ETS and NF-κB) and unclassified transcription factors (c-MYC, HIF, EMT transcription factors and P53) across diverse tumour types, thereby yielding a comprehensive overview identifying shared downstream targets, highlighting unique mechanisms and discussing complexities.

Overview of the multifaceted resistances toward EGFR-TKIs and new chemotherapeutic strategies in non-small cell lung cancer

The role of epidermal growth factor receptor (EGFR) in non-small cell lung cancer (NSCLC) has been vastly studied over the last decade. This has led to the rapid development of many generations of EGFR tyrosine kinase inhibitors (EGFR-TKIs). However, patients treated with third-generation TKIs (osimertinib, avitinib and rociletinib) targeting the EGFR T790M mutation have shown emerging resistances and relapses. Therefore, further molecular understanding of NSCLC mutations, bypass signalling, tumour microenvironment and the existence of cancer stem cells to overcome such resistances is warranted. This will pave the way for designing novel and effective chemotherapies to improve patients' overall survival. In this review, we provide an overview of the multifaceted mechanism of resistances towards EGFR-TKIs, as well as the challenges and perspectives that should be addressed in strategising chemotherapeutic treatments to overcome the ever evolving and adaptive nature of NSCLC.

An experimental model for ovarian cancer: propagation of ovarian cancer initiating cells and generation of ovarian cancer organoids

Background

Ovarian cancer (OC) is the most lethal gynecological cancer due to the recurrence of drug-resistance. Cancer initiating cells (CICs) are proposed to be responsible for the aggressiveness of OC. The rarity and difficulty of in vitro long-term cultivation of CICs challenge the development of CIC-targeting therapeutics. Reprogramming cancer cells into induced cancer initiating cell (iCICs) could be an approach to solve these. Several inducible CICs have been acquired by activating the expression of stemness genes in different cancer cells. However, few reports have demonstrated the feasibility in OC.

Methods

Patients with primary OC receiving surgery were enrolled. Tumor tissue were collected, and OCT4, SOX2, and NANOG expressions were assessed by immunohistochemistry (IHC) staining to investigate the association of stemness markers with overall survival (OS). An high-grade serous ovarian cancer (HGSOC) cell line, OVCAR-3 was reprogrammed by transducing Yamanaka four factors OCT4, SOX2, KLF4 and MYC (OSKM) to establish an iOCIC model, iOVCAR-3-OSKM. CIC characteristics of iOVCAR-3-OSKM were evaluated by RT-PCR, sphere formation assay and animal experiments. Drug-resistance and migration ability were accessed by dye-efflux activity assay, MTT assay and migration assay. Gene profile was presented through RNA-sequencing. Lineage differentiation ability and organoid culture were determined by in vitro differentiation assays.

Results

In OC patients, the co-expression of multiple stem-related transcription factors (OCT4, SOX2, and NANOG) was associated with worse OS. iOVCAR-3-OSKM cells generated by reprogramming successfully exhibited stemness characteristics with strong sphere-forming and tumorigenesis ability. iOVCAR-3-OSKM cells also showed malignant potential with higher drug resistance to chemodrug, Paclitaxel (PTX) and migration ability. iOVCAR-3-OSKM was maintainable and expandable on feeder-dependent culture condition, it also preserved ovarian lineage differentiation abilities, which could well differentiate into OC cells with CK-7 and CA125 expressions and develop into an organoid mimic poor prognostic OC histological feature.

Conclusions

The establishment of iOVCAR-3-OSKM not only allows us to fill the gap in the information on induced CICs in OC but also provides a potential strategy to develop personalized CICs and organoid models for treating OC in the near future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10042-3.

Oncofetal proteins and cancer stem cells

Cancer stem cells (CSCs) are considered as a small population of cells with stem-like properties within the tumor bulk, and are largely responsible for tumor recurrence, metastasis, and therapy resistance. CSCs share critical features with embryonic stem cells (ESCs). The pluripotent transcription factors (TFs) and developmental signaling pathways of ESCs are invariably hijacked by CSCs termed ‘oncofetal drivers’ in many cancers, which are rarely detectable in adult tissues. The unique expression pattern makes oncofetal proteins ideal therapeutic targets in cancer treatment. Therefore, elucidation of oncofetal drivers in cancers is critical for the development of effective CSCs-directed therapy. In this review, we summarize the common pluripotent TFs such as OCT4, SOX2, NANOG, KLF4, MYC, SALL4, and FOXM1, as well as the development signaling including Wnt/β-catenin, Hedgehog (Hh), Hippo, Notch, and TGF-β pathways of ESCs and CSCs. We also describe the newly identified oncofetal proteins that drive the self-renewal, plasticity, and therapy-resistance of CSCs. Finally, we explore how the clinical implementation of targeting oncofetal drivers, including small-molecule inhibitors, vaccines, antibodies, and CAR-T (chimeric antigen receptor T cell) can facilitate the development of CSCs-directed therapy.

Ferroptosis and Tumor Drug Resistance: Current Status and Major Challenges

Ferroptosis is a novel type of regulated cell death, whose unique metabolic characteristics are commonly used to evaluate the conditions of various diseases especially in tumors. Accumulating evidence supports that ferroptosis can regulate tumor development, metastasis, and therapeutic responses. Considering to the important role of chemotherapy in tumor treatment, drug resistance has become the most serious challenge. Revealing the molecular mechanism of ferroptosis is expected to solve tumor drug resistance and find new therapies to treat cancers. In this review, we discuss the relationship between ferroptosis and tumor drug resistance, summarize the abnormal ferroptosis in tissues of different cancer types and current research progress and challenges in overcoming treatment resistance, and explore the concept of targeting ferroptosis to improve tumor treatment outcomes.

OCT4 and SOX2 Specific Cytotoxic T Cells Exhibit Not Only Good Efficiency but Also Synergize PD-1 Inhibitor (Nivolumab) in Treating Breast Cancer Stem-Like Cells and Drug-Resistant Breast Cancer Mice

Purpose

This study aimed to investigate the effect of OCT4&SOX2 specific cytotoxic T lymphocytes (CTLs) plus programmed cell death protein-1 (PD-1) inhibitor (nivolumab) on treating breast cancer stem-like cells (BCSCs) in vitro and drug-resistance breast cancer (DRBC) mice in vivo.

Methods

In total, 160 breast cancer patients were enrolled following the immunofluorescence assay to detect tumor OCT4 and SOX2 expressions. CD154-activated B cells were co-cultured with CD8⁺ T cells (from breast cancer patients) in the presence of OCT4&SOX2 peptides, CMV pp65 peptides (negative control), and no peptides (normal control). MCF7-BCSCs were constructed by drug-resistance experiment and sphere-formation assay, then DRBC mice were constructed by planting MCF7-BCSCs. Subsequently, different doses of OCT4&SOX2 CTLs and PD-1 inhibitor (nivolumab) were used to treat MCF7-BCSCs and DRBC mice.

Results

OCT4 and SOX2 correlated with poor differentiation, more advanced stage, and worse prognosis in breast cancer patients. In vitro, OCT4&SOX2 CTLs with effector-target ratio (ETR) 5:1, 10:1 and 20:1 presented with increased cytotoxic activity compared to CMV pp65 CTLs with ETR 20:1 (negative control) and Control CTLs with ETR 20:1 (normal control) on killing MCF7-BCSCs. Besides, PD-1 inhibitor (nivolumab) improved the cytotoxic activity of OCT4&SOX2 CTLs against MCF7-BCSCs in a dose-dependent manner. In vivo, OCT4&SOX2 CTLs plus PD-1 inhibitor (nivolumab) decreased tumor volume and tumor weight while increased tumor apoptosis rate compared to OCT4&SOX2 CTLs alone, PD-1 inhibitor (nivolumab) alone, and control.

Conclusion

OCT4&SOX2 CTLs exhibit good efficiency and synergize PD-1 inhibitor (nivolumab) in treating BCSCs and DRBC.

Role, molecular mechanism and the potential target of breast cancer stem cells in breast cancer development

Breast cancer (BC) is one of the most common malignant tumors in women globally, and its occurrence has surpassed lung cancer and become the biggest threat for women. At present, breast cancer treatment includes surgical resection or postoperative chemotherapy and radiotherapy. However, tumor relapse and metastasis usually lead to current therapy failure thanks to breast cancer stem cells (BCSCs)-mediated tumorigenicity and drug resistance. Drug resistance is mainly due to the long-term quiescent G0 phase, strong DNA repairability, and high expression of ABC transporter, and the tumorigenicity is reflected in the activation of various proliferation pathways related to BCSCs. Therefore, understanding the characteristics of BCSCs and their intracellular and extracellular molecular mechanisms is crucial for the development of targeted drugs for BCSCs. To this end, we discussed the latest developments in BCSCs research, focusing on the analysis of specific markers, critical signaling pathways that maintain the stemness of BCSCs，such as NOTCH, Wnt/β-catenin, STAT3, Hedgehog, and Hippo-YAP signaling, immunomicroenviroment and summarizes targeting therapy strategies for stemness maintenance and differentiation, which provides a theoretical basis for further exploration of treating breast cancer and preventing relapse derived from BCSCs.

Impact of Cancer Stem Cells and Cancer Stem Cell-Driven Drug Resiliency in Lung Tumor: Options in Sight

Causing a high mortality rate worldwide, lung cancer remains an incurable malignancy resistant to conventional therapy. Despite the discovery of specific molecular targets and new treatment strategies, there remains a pressing need to develop more efficient therapy to further improve the management of this disease. Cancer stem cells (CSCs) are considered the root of sustained tumor growth. This consensus corroborates the CSC model asserting that a distinct subpopulation of malignant cells within a tumor drives and maintains tumor progression with high heterogeneity. Besides being highly tumorigenic, CSCs are highly refractory to standard drugs; therefore, cancer treatment should be focused on eliminating these cells. Herein, we present the current knowledge of the existence of CSCs, CSC-associated mechanisms of chemoresistance, the ability of CSCs to evade immune surveillance, and potential CSC inhibitors in lung cancer, to provide a wider insight to drive a more efficient elimination of this pro-oncogenic and treatment-resistant cell fraction.

Therapeutic Targeting of Cancer Stem Cells in Lung, Head and Neck, and Bladder Cancers

Simple Summary

Effective cancer treatment hinges upon overcoming therapeutic resistance mechanisms that allow for the continued proliferation of cancer cell subpopulations. Exposure to pharmacotherapy invariably leads to resistance as tumor cells with selected advantageous features evade destruction and alter the tumor composition. Cancer stem cells (CSCs) with features of plasticity that allow for regeneration and differentiation are particularly responsible for this phenomenon. Advances in tumor biology and molecular signaling have highlighted their role in neoplastic initiation, invasion, and maintenance. Novel strategies to direct therapy against these tumor cell subpopulations have the potential to dramatically alter tumor response and change the course of cancer care.

Abstract

Resistance to cancer therapy remains a significant obstacle in treating patients with various solid malignancies. Exposure to current chemotherapeutics and targeted agents invariably leads to therapy resistance, heralding the need for novel agents. Cancer stem cells (CSCs)—a subpopulation of tumor cells with capacities for self-renewal and multi-lineage differentiation—represent a pool of therapeutically resistant cells. CSCs often share physical and molecular characteristics with the stem cell population of the human body. It remains challenging to selectively target CSCs in therapeutically resistant tumors. The generation of CSCs and induction of therapeutic resistance can be attributed to several deregulated critical growth regulatory signaling pathways such as WNT/β-catenin, Notch, Hippo, and Hedgehog. Beyond growth regulatory pathways, CSCs also change the tumor microenvironment and resist endogenous immune attack. Thus, CSCs can interfere with each stage of carcinogenesis from malignant transformation to the onset of metastasis to tumor recurrence. A thorough review of novel targeted agents to act against CSCs is fundamental for advancing cancer treatment in the setting of both intrinsic and acquired resistance.

Emerging Insights into Targeted Therapy-Tolerant Persister Cells in Cancer

Drug resistance is perhaps the greatest challenge in improving outcomes for cancer patients undergoing treatment with targeted therapies. It is becoming clear that "persisters," a subpopulation of drug-tolerant cells found in cancer populations, play a critical role in the development of drug resistance. Persisters are able to maintain viability under therapy but are typically slow cycling or dormant. These cells do not harbor classic drug resistance driver alterations, and their partial resistance phenotype is transient and reversible upon removal of the drug. In the clinic, the persister state most closely corresponds to minimal residual disease from which relapse can occur if treatment is discontinued or if acquired drug resistance develops in response to continuous therapy. Thus, eliminating persister cells will be crucial to improve outcomes for cancer patients. Using lung cancer targeted therapies as a primary paradigm, this review will give an overview of the characteristics of drug-tolerant persister cells, mechanisms associated with drug tolerance, and potential therapeutic opportunities to target this persister cell population in tumors.

When to wake up? The optimal waking-up strategies for starvation-induced persistence

Prolonged lag time can be induced by starvation contributing to the antibiotic tolerance of bacteria. We analyze the optimal lag time to survive and grow the iterative and stochastic application of antibiotics. A simple model shows that the optimal lag time can exhibit a discontinuous transition when the severeness of the antibiotic application, such as the probability to be exposed the antibiotic, the death rate under the exposure, and the duration of the exposure, is increased. This suggests the possibility of reducing tolerant bacteria by controlled usage of antibiotics application. When the bacterial populations are able to have two phenotypes with different lag times, the fraction of the second phenotype that has different lag time shows a continuous transition. We then present a generic framework to investigate the optimal lag time distribution for total population fitness for a given distribution of the antibiotic application duration. The obtained optimal distributions have multiple peaks for a wide range of the antibiotic application duration distributions, including the case where the latter is monotonically decreasing. The analysis supports the advantage in evolving multiple, possibly discrete phenotypes in lag time for bacterial long-term fitness.

Inhibition of Wnt/β-catenin pathway reverses multi-drug resistance and EMT in Oct4+/Nanog+ NSCLC cells

Cancer drug resistance and epithelial-mesenchymal transition (EMT), a critical process of cancer invasion and metastasis, have recently been associated with the existence of cancer stem cells (CSCs). However, there are no appropriate CSC-markers of non-small cell lung cancer (NSCLC)-associated drug resistance and EMT. It is unknown if and how the drug-resistant and EMT phenotypes in NSCLC cells link to specific stemness-related pathways. Here, we found a significant elevated expression of both Oct4 and Nanog in gefitinib-resistant NSCLC cells, which displayed multi-drug resistance (MDR) properties and exhibited EMT phenotype. Ectopic co-expression of Oct4/Nanog empowered NSCLC cells with cancer stem cell properties, including self-renewal, drug resistance, EMT and high tumorigenic capacity. Following molecular mechanism investigation indicated Oct4/Nanog-regulated drug resistance and EMT change through Wnt/β-catenin signaling activation. Moreover, silencing β-catenin abrogated Oct4/Nanog-mediated MDR and EMT process in NSCLC cells. Our findings propose Wnt/β-catenin pathway as a promising therapeutic target for the treatment of progression and metastasis of NSCLC with CSC-like signatures and epithelial-mesenchymal transition phenotype.

The Dark Side of Gefitinib: Reflectance Confocal Microscopy Applied to Hair Hyperpigmentation

Gefitinib is a multi-target tyrosine kinase inhibitor used for the treatment of non-small cell lung cancer. Papulo-pustular and/or paronychia, abnormalities in hair growth, itching, and dryness due to epidermal growth factor inhibitors - i.e., PRIDE Complex - are a common effect of tyrosine kinase inhibitors. We report a case of hair and eyebrow hyperpigmentation after 7 months of treatment with gefitinib. In the literature, we found no data regarding rapid pigmentation of hair due to treatment with any multi-target tyrosine kinase inhibitors. To our knowledge, this is the first case reporting both hair and eyebrow hyperpigmentation. We hypothesize the role of different mechanisms linked to rapid hair hyperpigmentation.

Role of FBXW7 in the quiescence of gefitinib-resistant lung cancer stem cells in EGFR-mutant non-small cell lung cancer

Several recent studies suggest that cancer stem cells (CSCs) are involved in intrinsic resistance to cancer treatment. Maintenance of quiescence is crucial for establishing resistance of CSCs to cancer therapeutics. F-box/WD repeat-containing protein 7 (FBXW7) is a ubiquitin ligase that regulates quiescence by targeting the c-MYC protein for ubiquitination. We previously reported that gefitinib-resistant persisters (GRPs) in EGFR-mutant non-small cell lung cancer (NSCLC) cells highly expressed octamer-binding transcription factor 4 (Oct-4) as well as the lung CSC marker CD133, and they exhibited distinctive features of the CSC phenotype. However, the role of FBXW7 in lung CSCs and their resistance to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors in NSCLC is not fully understood. In this study, we developed GRPs from the two NSCLC cell lines PC9 and HCC827, which express an EGFR exon 19 deletion mutation, by treatment with a high concentration of gefitinib. The GRPs from both PC9 and HCC827 cells expressed high levels of CD133 and FBXW7, but low levels of c-MYC. Cell cycle analysis demonstrated that the majority of GRPs existed in the G0/G1 phase. Knockdown of the FBXW7 gene significantly reduced the cell number of CD133-positive GRPs and reversed the cell population in the G0/G1-phase. We also found that FBXW7 expression in CD133-positive cells was increased and c-MYC expression was decreased in gefitinib-resistant tumors of PC9 cells in mice and in 9 out of 14 tumor specimens from EGFR-mutant NSCLC patients with acquired resistance to gefitinib. These findings suggest that FBXW7 plays a pivotal role in the maintenance of quiescence in gefitinib-resistant lung CSCs in EGFR mutation-positive NSCLC.

Hypoxia inducible factors in the tumor microenvironment as therapeutic targets of cancer stem cells

Cancer stem cells (CSC) constitute a small area of the tumor mass and are characterized by self-renewal, differentiation and the ability to promote the development of secondary chemo-resistant tumors. Self-renewal of CSCs is regulated through various signaling pathways including Hedgehog, Notch, and Wnt/β-catenin pathways. A few surface markers have been identified, which provide a means of targeting CSCs according to tumor type. Depending on the proximity of CSCs to the tumor hypoxic niche, hypoxia-inducible factors (HIFs) can play a critical role in modulating several CSC-related characteristics. For instance, the upregulation of HIF-1 and HIF-2 at tumor sites, which correlates with the expansion of CSCs and poor cancer prognosis, has been demonstrated. In this review, we will discuss the mechanisms by which hypoxia enhances the development of CSCs in the tumor microenvironment. Targeting HIFs in combination with other common therapeutics is pre-requisite for effective eradication of CSCs.

Why Be One Protein When You Can Affect Many? The Multiple Roles of YB-1 in Lung Cancer and Mesothelioma

Lung cancers and malignant pleural mesothelioma (MPM) have some of the worst 5-year survival rates of all cancer types, primarily due to a lack of effective treatment options for most patients. Targeted therapies have shown some promise in thoracic cancers, although efficacy is limited only to patients harboring specific mutations or target expression. Although a number of actionable mutations have now been identified, a large population of thoracic cancer patients have no therapeutic options outside of first-line chemotherapy. It is therefore crucial to identify alternative targets that might lead to the development of new ways of treating patients diagnosed with these diseases. The multifunctional oncoprotein Y-box binding protein-1 (YB-1) could serve as one such target. Recent studies also link this protein to many inherent behaviors of thoracic cancer cells such as proliferation, invasion, metastasis and involvement in cancer stem-like cells. Here, we review the regulation of YB-1 at the transcriptional, translational, post-translational and sub-cellular levels in thoracic cancer and discuss its potential use as a biomarker and therapeutic target.

Downregulation of microRNA-196a inhibits stem cell self-renewal ability and stemness in non-small-cell lung cancer through upregulating GPX3 expression

Studies have reported a high expression profile of microRNA-196a (miR-196a) in many cancers, which potently plays important roles in carcinogenesis. However, the involvement of miR-196a in affecting non-small cell lung cancer (NSCLC) carcinogenesis still remains uncertain. NSCLC-related differentially expressed genes were retrieved for this study according to the microarray-based analysis, which demonstrated that miR-196a may be involved in NSCLC progression via regulation of the Jun N-terminal kinase (JNK) pathway by targeting glutathione peroxidase 3 (GPX3). Hence, this study aimed to explore the relationship among miR-196a, GPX3, and the JNK pathway and to investigate its functional regulations in NSCLC. Initially, highly-expressed miR-196a and lowly-expressed GPX3 were determined in NSCLC tissues and cells. Next, the NSCLC cells were manipulated with a series of mimic, inhibitor or shRNA to investigate the impact of miR-196a and GPX3 on CSC viability, proliferation, self-renewal ability and stemness. The in vivo effect of miR-196a was measured in nude mice xenografted with NSCLC cells. The results demonstrated that downregulation of miR-196a and restoration of GPX3 inhibited CSC viability, proliferation, self-renewal ability, stemness and tumorigenicity. Meanwhile, the underlying relationship among miR-196a, GPX3 and JNK pathway was explored by treatment with the JNK pathway inhibitor (SP600125), or sh-GPX3. Downregulated miR-196a and upregulated GPX3 could elevate the GPX3 protein expression and reduce the extent of JNK and c-Jun phosphorylation. Taken together, miR-196a promotes the development of NSCLC via activation of the JNK pathway through down-regulation of GPX3 and serve as a potential therapeutic target in NSCLC.

Intrinsic resistance to EGFR-Tyrosine Kinase Inhibitors in EGFR-Mutant Non-Small Cell Lung Cancer: Differences and Similarities with Acquired Resistance

Activating mutations in the epidermal growth factor receptor gene occur as early cancer-driving clonal events in a subset of patients with non-small cell lung cancer (NSCLC) and result in increased sensitivity to EGFR-tyrosine-kinase-inhibitors (EGFR-TKIs). Despite very frequent and often prolonged clinical response to EGFR-TKIs, virtually all advanced EGFR-mutated (EGFRM+) NSCLCs inevitably acquire resistance mechanisms and progress at some point during treatment. Additionally, 20-30% of patients do not respond or respond for a very short time (<3 months) because of intrinsic resistance. While several mechanisms of acquired EGFR-TKI-resistance have been determined by analyzing tumor specimens obtained at disease progression, the factors causing intrinsic TKI-resistance are less understood. However, recent comprehensive molecular-pathological profiling of advanced EGFRM+ NSCLC at baseline has illustrated the co-existence of multiple genetic, phenotypic, and functional mechanisms that may contribute to tumor progression and cause intrinsic TKI-resistance. Several of these mechanisms have been further corroborated by preclinical experiments. Intrinsic resistance can be caused by mechanisms inherent in EGFR or by EGFR-independent processes, including genetic, phenotypic or functional tumor changes. This comprehensive review describes the identified mechanisms connected with intrinsic EGFR-TKI-resistance and differences and similarities with acquired resistance and among clinically implemented EGFR-TKIs of different generations. Additionally, the review highlights the need for extensive pre-treatment molecular profiling of advanced NSCLC for identifying inherently TKI-resistant cases and designing potential combinatorial targeted strategies to treat them.

Biomaterial substrate-derived compact cellular spheroids mimicking the behavior of pancreatic cancer and microenvironment

Pancreatic stromal cells especially pancreatic stellate cells (PSCs) play a critical role in the progression of human pancreatic ductal adenocarcinoma (PDAC). However, the exact interaction between cancer cells and PSCs remains to be elucidated in order to develop more effective therapeutic approaches to treat PDAC. The microenvironment of PDAC shows higher hyaluronan (HA) levels, which is associated with poor prognosis of PDAC patients. In the current study, an efficient three-dimensional tumor spheroid model for PDAC was established. The pancreatic cancer cells and PSCs were co-cultured on hyaluronan grafted chitosan (CS-HA) coated plates to generate 3D tumor-like co-spheroids. The pancreatic cancer cells and PSCs (1:9 ratio) co-cultured on CS-HA coated plates were assembled into tumor-like co-spheroids with 3D core-shell structure in 48 h. These spheroids displayed potent in vitro tumorigenicity such as up-regulated expression of stemness and migration markers. The migration rate of cancer cells in spheroids (from 1:9 cell ratio) was much faster (3.2-fold) than that of cancer cells alone. Meanwhile, this unique co-spheroidal cancer cell structure with the outer wrap of PSCs contributed to the chemo-resistance of pancreatic cancer cells to gemcitabine as well as sensitivity to the combined gemcitabine and Abraxane treatment in vitro. The metastatic nature of the spheroids was confirmed by the zebrafish xenograft model in vivo. The compact and dynamic pancreatic cancer-PSC co-spheroids generated by the unique 3D co-culture platform on CS-HA biomaterials can mimic the PSC-constituting microenvironment of PDAC and demonstrate the chemo-resistant, invasive, and metastatic phenotypes. They have potential applications in personalized and high-throughput drug screening.

Cancer Stem Cell Biomarkers in EGFR-Mutation-Positive Non-Small-Cell Lung Cancer

INTRODUCTION

Epidermal growth factor receptor (EGFR) pathway deregulation promotes the acquisition of stemlike properties in non-small-cell lung cancer. EGFR inhibition through NOTCH enriches lung cancer stem cells (CSCs). Src through Yes-associated protein 1 (YAP1) activates NOTCH. Signal transduction and activator of transcription 3 (STAT3) activation occurs upon EGFR blockade and regulates the generation of CSCs.

PATIENTS AND METHODS

Using the Aldefluor assay kit, we investigated the enrichment of aldehyde dehydrogenase (ALDH)-positive cells in EGFR-mutation-positive cells treated with gefitinib, afatinib, and osimertinib. Western blot analysis was performed to evaluate changes in CSC marker expression upon EGFR blockade. We performed gene expression analysis in a cohort of EGFR-mutation-positive non-small-cell lung cancer patients. We evaluated the association of gene expression with treatment outcomes.

RESULTS

The cell subpopulation surviving EGFR inhibition had high ALDH activity and elevated CSC marker expression. Concurrent inhibition of EGFR, STAT3, and Src diminished the CSC subpopulation in an EGFR-mutation-positive cellular model. In a cohort of 64 EGFR-mutation-positive patients, 2 ALDH1 isoforms and the NOTCH target hairy and enhancer of split 1 (HES1), when highly expressed, were predictive of worse outcome to EGFR blockade. The gene expression of B-cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) that maintains the self-renewal of stem cells was also related to treatment outcome.

CONCLUSION

Single EGFR inhibitors increase the population of CSCs. Combinatory therapy targeting STAT3 and Src may be of potential benefit. ALDH1, HES1, and Bmi-1 are essential biomarkers in the initial assessment of EGFR-mutation-positive patients.

Nr5a2 promotes cancer stem cell properties and tumorigenesis in nonsmall cell lung cancer by regulating Nanog

Lung cancer has the highest mortality rate due to late diagnosis and high incidence of metastasis. Cancer stem cells (CSCs) are a subgroup of cancer cells with self‐renewal capability similar to that of normal stem cells (NSCs). While CSCs may play an important role in cancer progression, mechanisms underlying CSC self‐renewal and the relationship between self‐renewal of the NSCs and CSCs remain elusive. The orphan nuclear receptor Nr5a2 is a transcriptional factor, and a regulator of stemness of embryonic stem cells and induced pluripotent stem cells. However, whether Nr5a2 regulates the self‐renewal of lung CSCs is unknown. Here, we showed the diagnostic and prognostic values of elevated Nr5a2 expression in human lung cancer. We generated the mouse LLC‐SD lung carcinoma CSC cellular model in which Nr5a2 expression was enhanced. Using the LLC‐SD model, through transient and stable siRNA interference of Nr5a2 expression, we provided convincing evidence for a regulatory role of Nr5a2 in the maintenance of lung CSC self‐renewal and stem cell properties in vitro. Further, using the syngeneic and orthotopic lung transplantation model, we elucidated augmented cancer biological properties associated with Nr5a2 promotion of LLC‐SD self‐renewal. More importantly, we revealed that Nr5a2’s regulatory role in promoting LLC‐SD self‐renewal is mediated by transcriptional activation of its direct target Nanog. Taken together, in this study, we have provided convincing evidence in vitro and in vivo demonstrating that Nr5a2 can induce lung CSC properties and promote tumorigenesis and progression through transcriptional up‐regulation of Nanog.

Silencing the OCT4-PG1 pseudogene reduces OCT-4 protein levels and changes characteristics of the multidrug resistance phenotype in chronic myeloid leukemia

Cancer stem cells show epigenetic plasticity and intrinsic resistance to anti-cancer therapy, rendering capable of initiating cancer relapse and progression. Transcription factor OCT-4 regulates various pathways in stem cells, but its expression can be regulated by pseudogenes. This work evaluated how OCT4-PG1 pseudogene can affect OCT-4 expression and mechanisms related to the multidrug resistance (MDR) phenotype in FEPS cells. Considering that OCT-4 protein is a transcription factor that regulates expression of ABC transporters, level of gene expression, activity of ABC proteins and cell sensitivity to chemotherapy were evaluated after OCT4-PG1 silencing. Besides we set up a STRING network. Results showed that after OCT4-PG1 silencing, cells expressed OCT-4 gene and protein to a lesser extent than mock cells. The gene and protein expression of ABCB1, as well as its activity were reduced. On the other hand, ALOX5 and ABCC1 genes was increased even as the activity of this transporter. Moreover, the silencing cells become sensitive to two chemotherapics tested. The network structure demonstrated that OCT4-PG1 protein interacts directly with OCT-4, SOX2, and NANOG and indirectly with ABC transporters. We conclude that OCT4-PG1 pseudogene plays a key role in the regulation OCT-4 transcription factor, which alters MDR phenotype in the FEPS cell line.

Somatic Pluripotent Genes in Tissue Repair, Developmental Disease, and Cancer

Embryonic stem cells possess the ability to differentiate into all cell types of the body. This pliable developmental state is achieved by the function of a series of pluripotency factors, classically identified as OCT4, SOX2, and NANOG. These pluripotency factors are responsible for activating the larger pluripotency networks and the self-renewal programs which give ES cells their unique characteristics. However, during differentiation pluripotency networks become downregulated as cells achieve greater lineage specification and exit the cell cycle. Typically the repression of pluripotency is viewed as a positive factor to ensure the fidelity of cellular identity by restricting cellular pliancy. Consistent with this view, the expression of pluripotency factors is greatly restricted in somatic cells. However, there are examples whereby cells either maintain or reactivate pluripotency factors to preserve the increased potential for the healing of wounds or tissue homeostasis. Additionally there are many examples where these pluripotency factors become reactivated in a variety of human pathologies, particularly cancer. In this review, we will summarize the somatic repression of pluripotency factors, their role in tissue homeostasis and wound repair, and the human diseases that are associated with pluripotency factor misregulation with an emphasis on their role in the etiology of multiple cancers.

MicroRNA-122 negatively associates with peroxiredoxin-II expression in human gefitinib-resistant lung cancer stem cells

Previously, we demonstrated that Prx II is important for survival of the gefitinib-resistant A549 (A549/GR) cell line, an NSCLC cell line derived by repeated exposure to gefitinib. Therefore, in this study, we used A549/GR cells to investigate the role of Prx II in GR NSCLC stemness. Initially, to explore the stemness characteristics and investigate the association of Prx II with those stemness characteristics, we successfully isolated a stem cell-like population from A549/GR cells. A549/GR CD133⁺ cells possessed important cancer stemness characteristics, including the abilities to undergo metastasis, angiogenesis, self-renewal, and to express stemness genes and epithelial–mesenchymal transition (EMT) markers. However, those characteristics were abolished by knocking down Prx II expression. MicroRNA 122 (miR-122) targets Prx II in A549/GR cancer stem cells (CSCs), thereby inhibiting the stemness characteristics in vitro and in vivo. Next, we investigate whether miR-122 overexpression was associated with Prx II expression and Prx-II-induced stemness characteristics, we transfected miR-122 into A549/GR CSCs. MiR-122 inhibited A549/GR stemness by downregulating the Hedgehog, Notch, and Wnt/β-catenin pathways. Taken together, our data suggest that Prx II promotes A549/GR stemness, and that targeting Prx II and miR-122 is a potentially viable strategy for anti-cancer-stem cell therapy in GR NSCLCs.

Nitric oxide promotes cancer cell dedifferentiation by disrupting an Oct4:caveolin-1 complex: A new regulatory mechanism for cancer stem cell formation

Cancer stem cells (CSCs) are unique populations of cells that can self-renew and generate different cancer cell lineages. Although CSCs are believed to be a promising target for novel therapies, the specific mechanisms by which these putative therapeutics could intervene are less clear. Nitric oxide (NO) is a biological mediator frequently up-regulated in tumors and has been linked to cancer aggressiveness. Here, we search for targets of NO that could explain its activity. We find that it directly affects the stability and function of octamer-binding transcription factor 4 (Oct4), known to drive the stemness of lung cancer cells. We demonstrated that NO promotes the CSC-regulatory activity of Oct4 through a mechanism that involves complex formation between Oct4 and the scaffolding protein caveolin-1 (Cav-1). In the absence of NO, Oct4 forms a molecular complex with Cav-1, which promotes the ubiquitin-mediated proteasomal degradation of Oct4. NO promotes Akt-dependent phosphorylation of Cav-1 at tyrosine 14, disrupting the Cav-1:Oct4 complex. Site-directed mutagenesis and computational modeling studies revealed that the hydroxyl moiety at tyrosine 14 of Cav-1 is crucial for its interaction with Oct4. Both removal of the hydroxyl via mutation to phenylalanine and phosphorylation lead to an increase in binding free energy (ΔG_bind) between Oct4 and Cav-1, destabilizing the complex. Together, these results unveiled a novel mechanism of CSC regulation through NO-mediated stabilization of Oct4, a key stem cell transcription factor, and point to new opportunities to design CSC-related therapeutics.

Nuclear EGFR-PKM2 axis induces cancer stem cell-like characteristics in irradiation-resistant cells

Radiation therapy has become an important tool in the treatment of cancer patients, but most patients relapse within 5 years. Relapse is due to the presence of cancer stem cells (CSCs), but the molecular mechanism of radioresistance in CSCs remains largely elusive. Here, we found that irradiation-resistant (IR) cells exhibited increased stem cell-like properties together with elevated anchorage-independent growth and metastasis ability. EGFR not only leads to increased acquisition of endometrial cancer stem cell markers in radioresistant sublines but is critical for the cancer stem-cell phenotype and tumorigenicity. Moreover, PKM2 functions as an interacting partner of EGFR, which induces the EMT phenotype and stem cell-like properties in IR cells. Finally, we found that the regulatory function of the EGFR-PKM2 axis is dependent on nuclear EGFR. In sum, our study indicated that EGFR and PKM2 directly interact and bind with each other to regulate the transcription of stemness-related genes and promote the stem-like phenotype, thus promoting invasion and metastasis.

Drug persistence - from antibiotics to cancer therapies

Drug-insensitive tumor subpopulations remain a significant barrier to effective cancer treatment. Recent works suggest that within isogenic drug-sensitive cancer populations, subsets of cells can enter a 'persister' state allowing them to survive prolonged drug treatment. Such persisters are well-described in antibiotic-treated bacterial populations. In this review, we compare mechanisms of drug persistence in bacteria and cancer. Both bacterial and cancer persisters are associated with slow-growing phenotypes, are metabolically distinct from non-persisters, and depend on the activation of specific regulatory programs. Moreover, evidence suggests that bacterial and cancer persisters are an important reservoir for the emergence of drug-resistant mutants. The emerging parallels between persistence in bacteria and cancer can guide efforts to untangle mechanistic links between growth, metabolism, and cellular regulation, and reveal exploitable therapeutic vulnerabilities.

EGFR-TKI resistance and MAP17 are associated with cancer stem cell like properties

Patients with non-small-cell lung cancer (NSCLC) with sensitive epidermal growth factor receptor (EGFR) mutations generally react well to tyrosine kinase inhibitors (TKIs). However acquired resistance eventually occurs. Several mechanisms contribute to the resistance including T790M mutation, c-Met amplification and PIK3CA mutation. In recent years, cancer stem cells (CSCs) have been suggested to be involved in TKI resistance. MAP17 is aberrantly overexpressed in a number of malignancies. However, the expression pattern and function of MAP17 in CSCs are still unclear. The aim the present study was to illustrate the effect of CSC-like cells on the resistance to TKIs in EGFR mutant NSCLC cells and explore the possible role of MAP17 in CSCs. The EGFR mutant cell line PC9 was cultured under serum-deprived undifferentiated conditions. The CSC properties including expression of stem cell markers CD133, CD44, Oct-4 and ABCG2, ability of self-renewal, invasion, proliferation and tumorigenesis were examined. The expression of MAP17 was compared in sphere and parent cells. Sphere cells displayed stem cells phenotypes and were resistant to erlotinib. Sphere cells expressed higher levels of MAP17, and MAP17 was associated with self-renewal and TKI resistance. The function of MAP17 demonstrated to be partially dependent on Na-dependent glucose transporter 1. Collectively these findings suggest that MAP17 serves a role in TKI resistance through regulation of CSCs in lung cancer.

MiR-128 reverses the gefitinib resistance of the lung cancer stem cells by inhibiting the c-met/PI3K/AKT pathway

Gefitinib is a first line anti-tumor drug used for the treatment of patients with non-small cell lung cancer (NSCLC) harboring EGFR mutations. However, the drug resistance to gefitinib limits its clinical application. Here, we observed the CSCs of PC9 are obviously resistant to gefitinib compared with the non-CSCs. Furthermore, we found the gefitinib failed to suppress the PI3K/AKT pathway in the PC9-CSCs. Mechanically, we showed significant down-regulation of miR-128 in the PC9-CSCs compared with the non-CSCs. Overexpression of miR-128 significantly increased the sensitivity of PC9-CSCs to gefitinib-induced apoptosis. In addition, the gene of c-met was proved to be directly inhibited by miR-128. Enforced expression of c-met could "rescue" the miR-128 promoted apoptosis and cleavage of caspases in PC9-CSCs treated with gefitinib. Thus, these results indicate that the miR-128/c-met pathway enhances the gefitinib sensitivity of the lung cancer stem cells by suppressing the PI3K/AKT pathway.

The prognostic value of CSCs biomarker CD133 in NSCLC: a meta-analysis

The prognostic value of cancer stem cells (CSCs) marker CD133 in non-small-cell lung cancer (NSCLC) remains controversial. We performed this meta-analysis of 32 eligible studies to clarify the prognostic value of CD133 and provide evidence for CSCs hypothesis. We calculated pooled hazard ratio (HR) for survival outcomes and pooled odds ratio (OR) for clinical parameters associated with CD133 in total 3595 NSCLC patients by STATA. Our results showed that NSCLC patients with higher CD133 expression had shorter overall survival time only in Asian patients (HR = 3.80, 95% CI: 3.12-4.04, p < 0.001; I2 = 32%) but not in Caucasian patients (HR = 1.15, 95% CI: 0.88-1.52, p = 0.307; I2 = 0%), suggesting that differential prognostic value of CD133 in distinct ethnic group. We speculated that the intrinsic EGFR gene status of CSCs might be responsible for this racial difference. Additionally, we found that higher expression of CD133 was associated with poor differentiation (OR = 2.03, 95% CI: 1.32-3.14, p = 0.001) and lymph node metastasis (OR = 2.39, 95% CI: 1.62-3.52, p < 0.001) but there was no significant difference of CD133 expression between adenocarcinoma and squamous carcinoma (OR = 1.13, 95% CI: 0.93-1.38, p = 0.3) in NSCLC patients. These results may provide a new therapeutic perspective on the treatment of NSCLC patients according to the expression of CD133 in distinct ethnic group.

Toxic responses of Sox2 gene in the regeneration of the earthworm Eisenia foetida exposed to Retnoic acid

Exogenous retinoic acid delays and disturbs the regeneration of Eisenia foetida. The stem cell pluripotency factor, Sox2, can play a crucial role in cell reprogramming and dedifferentiation. In this study, we compared the regeneration of Eisenia foetida in different segments after amputation and the effects of retinoic acid on the regeneration of different segments. The results showed that the regeneration speed of the head and tail was slightly faster than the middle part, and retinoic acid disrupted and delayed the regeneration of the earthworm. The qRT-PCR and Western blot analysis showed that the expression of the Sox2 gene and Sox2 protein was highest on the seventh day in different segments (p<0.05). After treatment with retinoic acid, the expression level of the Sox2 gene and Sox2 protein was significantly reduced (p<0.05). The results indicated that the regeneration of earthworms and the formation of blastema are related to the expression of the Sox2 gene and protein. Retinoic acid delays and interferes with the regeneration of the earthworm by affecting the expression levels of the Sox2 gene and protein.

Correlation of cancer stem cell markers and immune cell markers in resected non-small cell lung cancer

Background: Recent studies confirmed that immunotherapy showed prominent efficacy in non-small cell lung cancer (NSCLC). Cancer stem cells/cancer initiating cells are resistant to anticancer treatment. The purpose of the study was to analyze the correlation of cancer stem cells/cancer initiating cells and tumor-infiltrating immune cells in NSCLC.

Methods: CD133, octamer 4 (OCT-4), CD8, CD56, human leukocyte antigen (HLA) class I and programmed death ligand-1 (PD-L1) were assessed in 172 resected NSCLC samples. The staining was analyzed and scored by the pathologist who was blinded to the clinical pathological data of the patients.

Results: High CD8+ T cell infiltration was correlated significantly with squamous cell carcinoma histology (p=0.008). High PD-L1 expression (≥10%) was associated with high tumor status (p=0.043). Pearson's correlation test showed that CD56+ cells were negatively correlated with CD133 expression (r=-0.361, p<0.001) and weakly correlated with negative OCT-4 expression (r=-0.180, p=0.018). There was a strong positive correlation between CD8 and HLA class I (r=0.573, p<0.001). In the survival analysis, high CD8+ T cell infiltration is an independent predictor of improved disease-free survival and overall survival. Patients with low CD133 expression and high CD56 expression had a longer overall survival than those with high CD133 expression and/or low CD56 expression (p=0.013).

Conclusion: There is a negative correlation between CD56+ cells and cancer stem cell markers. This correlation may confirm the possibility that natural killer cells can target CD133+ cancer stem cells/cancer initiating cells in non-small cell lung cancer.

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

Epidermal growth factor receptor-targeted tyrosine kinase inhibitors (EGFR-TKIs) have become first-line drugs used for non-small cell lung cancer (NSCLC) treatment. However, drug resistance to EGFR-TKIs will be developed inevitably due to the repeated use of these drugs. In the present study, we isolated cancer stem cells (CSCs) from the PC9 NSCLC cell line. We then observed that the PC9 CSCs showed significant resistance to erlotinib compared with the PC9 non-CSCs. Erlotinib failed to suppress the phosphorylation of PI3K and AKT in PC9 CSCs, although the EGFR was inhibited sufficiently. Mechanically, we observed aberrant upregulation of microRNA-23a (miR-23a) and downregulation of PTEN in PC9 CSCs compared to PC9 non-CSCs. Luciferase reporter assays proved that PTEN was the target of miR-23a in PC9 CSCs. Furthermore, knockdown of miR-23a enhanced the antitumor effect of erlotinib by increasing the expression of PTEN. In addition, transfection with miR-23a inhibitors promoted the erlotinib-dependent inhibition of PI3K/AKT pathway, thus, suppressing the proliferation and inducing apoptosis in PC9 CSCs. These results propose that upregulation of miR-23a is a potential mechanism associated with resistance to EGFR-TKIs in lung cancer stem cells. Inhibition of miR-23a serves as a novel therapeutic strategy to eliminate the EGFR-TKIs resistance of lung cancer stem cells.

Identification of a novel 12-bp insertion/deletion (indel) of iPS-related Oct4 gene and its association with reproductive traits in male piglets

As a key factor of cellular reprogramming, Oct4 is one of vital transcription factors for induced pluripotent stem cells (iPSCs). Loss of its function or deletion causes apoptosis in primordial germ cells (PGCs), which affect reproductive traits in mammals. In this study, a novel 12-bp insertion/deletion (indel) polymorphism (NC_010449:g.2759-2760insGGTTTTTGTCTA) within the Oct4 gene was identified in 442 pigs of Large White (LW) and Landrace (LD) breeds, showing three genotypes designated as II, ID, and DD. The frequencies of allele "I" in LW and LD pigs were 0.587 and 0.648, respectively. The male piglets with homozygous II or DD genotypes of Oct4 gene exhibited better reproductive traits than those with heterozygous ID genotype. Moreover, there were two significant associations between this 12-bp indel polymorphism and testis long circumference (TLC) (P=0.005) and testis short girth (TSG) (P=0.003) as well as 15-day testis weight (TW) (P=0.013) in the LW male piglets. These findings suggest that the 12-bp indel polymorphism of the Oct4 gene might be a potential DNA marker for selecting preferred individuals in relation to reproductive traits in pig marker-assisted selection (MAS) breeding, which could contribute to the breeding and genetics in male piglets.

Primary cultures of human colon cancer as a model to study cancer stem cells

The principal cause of death in cancer involves tumor progression and metastasis. Since only a small proportion of the primary tumor cells, cancer stem cells (CSCs), which are the most aggressive, have the capacity to metastasize and display properties of stem cells, it is imperative to characterize the gene expression of diagnostic markers and to evaluate the drug sensitivity in the CSCs themselves. Here, we have examined the key genes that are involved in the progression of colorectal cancer and are expressed in cancer stem cells. Primary cultures of colorectal cancer cells from a patient's tumors were studied using the flow cytometry and cytological methods. We have evaluated the clinical and stem cell marker expression in these cells, their resistance to 5-fluorouracil and irinotecan, and the ability of cells to form tumors in mice. The data shows the role of stem cell marker Oct4 in the resistance of primary colorectal cancer tumor cells to 5-fluorouracil.