Inhibition of mutant EGFR in lung cancer cells triggers SOX2-FOXO6-dependent survival pathways

Methods for assessing the effect of microRNA on stemness genes

According to the latest concepts, for micrometastasis to develop into macrometastasis, differentiated cancer cells must revert to a dedifferentiated state. Activation of stemness genes plays a key role in this transition. Suppression of stemness gene expression using microRNAs can become the basis for the development of effective anti-metastatic drugs. This article provides an overview of the existing methods for assessing the effect of microRNAs on stemness genes and cancer cell dedifferentiation.

Exosomes derived from MDR cells induce cetuximab resistance in CRC via PI3K/AKT signaling‑mediated Sox2 and PD‑L1 expression

The anti-EGFR antibody cetuximab is used as a first-line targeted therapeutic drug in colorectal cancer. It has previously been reported that the efficacy of the EGFR antibody cetuximab is limited by the emergence of acquired drug resistance. In our previous study the transmissibility effect of exosomes from drug resistant tumor cells to sensitive tumor cells was identified. It can therefore be hypothesized that drug resistant cells might affect neighboring and distant cells via regulation of exosome composition and behavior. However, the mechanism of exosomes in KRAS-wild-type colorectal cancer (CRC) remains unknown. In the present study, functional analysis of overall survival post-diagnosis in patients with KRAS wild-type and those with mutant CRC was performed using human CRC specimens. Furthermore, it was demonstrated that multidrug resistance (MDR) cancer cell-derived exosomes were potentially a key factor, which promoted cetuximab-resistance in CRC cells and reduced the inhibitory effect of cetuximab in CRC xenograft models. The Cell Counting Kit-8 and colony formation assays were performed to assess the effects of exosomes derived from CRC/MDR cells on cetuximab resistance. Sphere formation assay results demonstrated that exosomes derived from CRC/MDR cells altered the self-renewal and multipotential ability of stem-cell-associated markers and facilitated resistance to cetuximab in cetuximab-sensitive cells. Furthermore, exosomes derived from CRC/MDR cells decreased sensitivity to cetuximab via the activation of PI3K/AKT signaling, which promoted Sox2 and programmed death-ligand 1 (PD-L1) mRNA and protein expression according to reverse transcription-quantitative PCR, western blotting and immunohistochemistry analyses, as well as apoptosis resistance both in vitro and in vivo according to a TUNEL assay. In conclusion, the results of the present study demonstrated that exosomes derived from CRC/MDR cells may promote cetuximab resistance in KRAS wild-type cells via activation of the PI3K/AKT signaling pathway-mediated expression of Sox2 and PD-L1, which will be useful for investigating a potential clinical target in predicting cetuximab resistance.

From targeted therapy to a novel way: Immunogenic cell death in lung cancer

Lung cancer (LC) is one of the most incident malignancies and a leading cause of cancer mortality worldwide. Common tumorigenic drivers of LC mainly include genetic alterations of EGFR, ALK, KRAS, BRAF, ROS1, and MET. Small inhibitory molecules and antibodies selectively targeting these alterations or/and their downstream signaling pathways have been approved for treatment of LC. Unfortunately, following initial positive responses to these targeted therapies, a large number of patients show dismal prognosis due to the occurrence of resistance mechanisms, such as novel mutations of these genes and activation of alternative signaling pathways. Over the past decade, it has become clear that there is no possible cure for LC unless potent antitumor immune responses are induced by therapeutic intervention. Immunogenic cell death (ICD) is a newly emerged concept, a form of regulated cell death that is sufficient to activate adaptive immune responses against tumor cells. It transforms dying cancer cells into a therapeutic vaccine and stimulates long-lasting protective antitumor immunity. In this review, we discuss the key targetable genetic aberrations and the underlying mechanism of ICD in LC. Various agents inducing ICD are summarized and the possibility of harnessing ICD in LC immunotherapy is further explored.

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.

Epigenetic Alterations and Mechanisms That Drive Resistance to Targeted Cancer Therapies

Cancer is a complex disease and cancer cells typically harbor multiple genetic and epigenetic alterations. Large-scale sequencing of patient-derived cancer samples has identified several druggable driver oncogenes. Many of these oncogenes can be pharmacologically targeted to provide effective therapies for breast cancer, leukemia, lung cancer, melanoma, lymphoma, and other cancer types. Initial responses to these agents can be robust in many cancer types and some patients with cancer experience sustained tumor inhibition. However, resistance to these targeted therapeutics frequently emerges, either from intrinsic or acquired mechanisms, posing a major clinical hurdle for effective treatment. Several resistance mechanisms, both cell autonomous and cell nonautonomous, have been identified in different cancer types. Here we describe how alterations of the transcriptome, transcription factors, DNA, and chromatin regulatory proteins confer resistance to targeted therapeutic agents. We also elaborate on how these studies have identified underlying epigenetic factors that drive drug resistance and oncogenic pathways, with direct implications for the prevention and treatment of drug-resistant cancer.

EGFR Regulates the Hippo pathway by promoting the tyrosine phosphorylation of MOB1

The Hippo pathway is frequently dysregulated in cancer, leading to the unrestrained activity of its downstream targets, YAP/TAZ, and aberrant tumor growth. However, the precise mechanisms leading to YAP/TAZ activation in most cancers is still poorly understood. Analysis of large tissue collections revealed YAP activation in most head and neck squamous cell carcinoma (HNSCC), but only 29.8% of HNSCC cases present genetic alterations in the FAT1 tumor suppressor gene that may underlie persistent YAP signaling. EGFR is overexpressed in HNSCC and many other cancers, but whether EGFR controls YAP activation is still poorly understood. Here, we discover that EGFR activates YAP/TAZ in HNSCC cells, but independently of its typical signaling targets, including PI3K. Mechanistically, we find that EGFR promotes the phosphorylation of MOB1, a core Hippo pathway component, and the inactivation of LATS1/2 independently of MST1/2. Transcriptomic analysis reveals that erlotinib, a clinical EGFR inhibitor, inactivates YAP/TAZ. Remarkably, loss of LATS1/2, resulting in aberrant YAP/TAZ activity, confers erlotinib resistance on HNSCC and lung cancer cells. Our findings suggest that EGFR-YAP/TAZ signaling plays a growth-promoting role in cancers harboring EGFR alterations, and that inhibition of YAP/TAZ in combination with EGFR might be beneficial to prevent treatment resistance and cancer recurrence.

Ando et al show in head and neck squamous cell carcinoma cells that EGFR activation leads to the phosphorylation of the Hippo pathway component, MOB1 to inhibit LATS1/2 function resulting in YAP/TAZ activation. Further, EGFR-targeting therapies suppress YAP/TAZ, and loss of LATS1/2-mediated YAP/TAZ activation confers therapy resistance, thus offering insights into potential drug resistance mechanisms in cancers with activated EGFR.

Caveolin-1 and Sox-2 are predictive biomarkers of cetuximab response in head and neck cancer

The epidermal growth factor receptor (EGFR) inhibitor cetuximab is the only FDA-approved oncogene-targeting therapy for head and neck squamous cell carcinoma (HNSCC). Despite variable treatment response, no biomarkers exist to stratify patients for cetuximab therapy in HNSCC. Here, we applied unbiased hierarchical clustering to reverse-phase protein array molecular profiles from patient-derived xenograft (PDX) tumors and revealed 2 PDX clusters defined by protein networks associated with EGFR inhibitor resistance. In vivo validation revealed unbiased clustering to classify PDX tumors according to cetuximab response with 88% accuracy. Next, a support vector machine classifier algorithm identified a minimalist biomarker signature consisting of 8 proteins — caveolin-1, Sox-2, AXL, STING, Brd4, claudin-7, connexin-43, and fibronectin — with expression that strongly predicted cetuximab response in PDXs using either protein or mRNA. A combination of caveolin-1 and Sox-2 protein levels was sufficient to maintain high predictive accuracy, which we validated in tumor samples from patients with HNSCC with known clinical response to cetuximab. These results support further investigation into the combined use of caveolin-1 and Sox-2 as predictive biomarkers for cetuximab response in the clinic.

Gene Expression Profiling as a Potential Tool for Precision Oncology in Non-Small Cell Lung Cancer

Recent technological advances and the application of high-throughput mutation and transcriptome analyses have improved our understanding of cancer diseases, including non-small cell lung cancer. For instance, genomic profiling has allowed the identification of mutational events which can be treated with specific agents. However, detection of DNA alterations does not fully recapitulate the complexity of the disease and it does not allow selection of patients that benefit from chemo- or immunotherapy. In this context, transcriptional profiling has emerged as a promising tool for patient stratification and treatment guidance. For instance, transcriptional profiling has proven to be especially useful in the context of acquired resistance to targeted therapies and patients lacking targetable genomic alterations. Moreover, the comprehensive characterization of the expression level of the different pathways and genes involved in tumor progression is likely to better predict clinical benefit from different treatments than single biomarkers such as PD-L1 or tumor mutational burden in the case of immunotherapy. However, intrinsic technical and analytical limitations have hindered the use of these expression signatures in the clinical setting. In this review, we will focus on the data reported on molecular classification of non-small cell lung cancer and discuss the potential of transcriptional profiling as a predictor of survival and as a patient stratification tool to further personalize treatments.

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.

Personalized drug testing in a patient with non-small-cell lung cancer using cultured cancer cells from pleural effusion

Objective

Patients with non-small-cell lung cancer (NSCLC) and primary or acquired resistance do not respond to targeted drugs. We explored whether cancer cells can be cultured from liquid biopsies from patients with primary resistance to tyrosine kinase inhibitors (TKIs). We aimed to predict patients’ responses to drugs according to in vitro drug testing results.

Methods

Cancer cell cultures were established from the pleural effusion of a patient with TKI-resistant NSCLC using a conditional reprogramming technique. Phenotypic drug sensitivity tests were performed using the Cell Counting Kit-8 assay. We tested individual drugs and compared the synergistic and inhibitory effects of drug combinations.

Results

The results of our in vitro sensitivity test using the combination of cisplatin and pemetrexed were correlated with the patient’s response.

Conclusion

This represents the first successful report of predictive testing for combination therapy in patients with epidermal growth factor receptor-mutant NSCLC and primary TKI resistance. This strategy should be applicable to both chemotherapies and targeted therapies, and it will significantly improve the clinical treatment and management of patients with NSCLC and primary or acquired resistance to targeted therapies, as well as patients lacking targetable mutations.

SOX2 in cancer stemness: tumor malignancy and therapeutic potentials

Cancer stem cells (CSCs), a minor subpopulation of tumor bulks with self-renewal and seeding capacity to generate new tumors, posit a significant challenge to develop effective and long-lasting anti-cancer therapies. The emergence of drug resistance appears upon failure of chemo-/radiation therapy to eradicate the CSCs, thereby leading to CSC-mediated clinical relapse. Accumulating evidence suggests that transcription factor SOX2, a master regulator of embryonic and induced pluripotent stem cells, drives cancer stemness, fuels tumor initiation, and contributes to tumor aggressiveness through major drug resistance mechanisms like epithelial-to-mesenchymal transition, ATP-binding cassette drug transporters, anti-apoptotic and/or pro-survival signaling, lineage plasticity, and evasion of immune surveillance. Gaining a better insight and comprehensive interrogation into the mechanistic basis of SOX2-mediated generation of CSCs and treatment failure might therefore lead to new therapeutic targets involving CSC-specific anti-cancer strategies.

Upregulation of deubiquitinase USP7 by transcription factor FOXO6 promotes EC progression via targeting the JMJD3/CLU axis

Esophageal carcinoma (EC) is recognized as one of the most frequently occurring malignancies worldwide, and its high morbidity rate motivates efforts to identify potential therapeutic targets. Notably, forkhead box (FOX) family genes are highlighted as possible biomarkers for diagnostics, prognostics, and therapeutics of various malignancies, including EC. Our present study was performed to investigate the underlying mechanism of FOXO6 on the development of EC. We observed a significant upregulation of FOXO6 in EC tissues, contributing to the migration and proliferation in EC cells through gain- and loss-of-function assays. FOXO6 directly interacted with the ubiquitin-specific processing protease 7 (USP7) gene promoter and enhanced its transcriptional activity, which resulted in suppressed cancer cell apoptosis as revealed by chromatin immunoprecipitation (ChIP)-qPCR. USP7 enhanced the ubiquitination of Jumonji domain-containing protein D3 (JMJD3), elevated JMJD3-promoted growth of EC cells, and transcriptionally activated clusterin (CLU) expression at the promoter region via histone H3 lysine 27 tri-methyl (H3K27me3) demethylation, according to immunoprecipitation and ubiquitination assays. Finally, we verified that FOXO6 mediated effects on the USP7/JMJD3/CLU axis to exert an oncogenic role in vivo, which was blocked by USP7 and JMJD3 inhibitor. Our findings demonstrate an important role of the FOXO6/USP7/JMJD3/CLU pathway in EC progression and thus provide attractive potential therapeutic targets for EC patients.

Downregulation of FOXO6 alleviates hypoxia-induced apoptosis and oxidative stress in cardiomyocytes by enhancing Nrf2 activation via upregulation of SIRT6

Forkhead box protein O6 (FOXO6) has been recently identified as a novel regulator of oxidative stress in multiple pathological processes. However, whether FOXO6 participates in the regulation of oxidative stress of myocardial infarction is unclear. The present study was performed to evaluate the potential role of FOXO6 in regulating hypoxia-induced apoptosis and oxidative stress in cardiomyocytes in vitro. Our results demonstrated that FOXO6 expression was highly elevated in cardiomyocytes exposed to hypoxia. Downregulation of FOXO6 expression by the siRNA-mediated gene knockdown in hypoxia-exposed cardiomyocytes increased cell viability, while repressing apoptosis and reactive oxygen species (ROS) production. In contrast, overexpression of FOXO6 enhanced the sensitivity of cardiomyocytes to hypoxia-induced injury. Further, in-depth research revealed that knockdown of FOXO6 promoted the expression of sirtuin6 (SIRT6) and enhanced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant signaling. Moreover, SIRT6 inhibition markedly blocked the FOXO6 knockdown-induced promotion effect on Nrf2 activation. In addition, Nrf2 inhibition partially reversed the FOXO6 knockdown-mediated protective effect against hypoxia-induced cardiomyocyte injury. Taken together, the findings of our study demonstrate that knockdown of FOXO6 is capable of protecting cardiomyocytes from hypoxia-induced apoptosis and oxidative stress by enhancing Nrf2 activation via upregulation of SIRT6. Our study highlights a potential role of FOXO6 in myocardial infarction and suggests it as an attractive target for cardioprotection.

Mining a human transcriptome database for chemical modulators of NRF2

Nuclear factor erythroid-2 related factor 2 (NRF2) encoded by the NFE2L2 gene is a transcription factor critical for protecting cells from chemically-induced oxidative stress. We developed computational procedures to identify chemical modulators of NRF2 in a large database of human microarray data. A gene expression biomarker was built from statistically-filtered gene lists derived from microarray experiments in primary human hepatocytes and cancer cell lines exposed to NRF2-activating chemicals (oltipraz, sulforaphane, CDDO-Im) or in which the NRF2 suppressor Keap1 was knocked down by siRNA. Directionally consistent biomarker genes were further filtered for those dependent on NRF2 using a microarray dataset from cells after NFE2L2 siRNA knockdown. The resulting 143-gene biomarker was evaluated as a predictive tool using the correlation-based Running Fisher algorithm. Using 59 gene expression comparisons from chemically-treated cells with known NRF2 activating potential, the biomarker gave a balanced accuracy of 93%. The biomarker was comprised of many well-known NRF2 target genes (AKR1B10, AKR1C1, NQO1, TXNRD1, SRXN1, GCLC, GCLM), 69% of which were found to be bound directly by NRF2 using ChIP-Seq. NRF2 activity was assessed across ~9840 microarray comparisons from ~1460 studies examining the effects of ~2260 chemicals in human cell lines. A total of 260 and 43 chemicals were found to activate or suppress NRF2, respectively, most of which have not been previously reported to modulate NRF2 activity. Using a NRF2-responsive reporter gene in HepG2 cells, we confirmed the activity of a set of chemicals predicted using the biomarker. The biomarker will be useful for future gene expression screening studies of environmentally-relevant chemicals.

Comprehensive characterization of functional eRNAs in lung adenocarcinoma reveals novel regulators and a prognosis-related molecular subtype

Rationale: As the transcriptional products of active enhancers, enhancer RNAs (eRNAs) are essential for the initiation of tumorigenesis. However, the landscape and functional characteristics of eRNAs in Chinese lung adenocarcinoma, and the clinical utility of eRNA-based molecular subtypes remain largely unknown. Methods: A genome-wide profiling of eRNAs was performed in 80 Chinese lung adenocarcinoma patients with RNA-seq data. Functional eRNAs and associated genes were identified between paired adenocarcinoma and adjacent samples. Unsupervised clustering of functional eRNAs was conducted and the associations with molecular characteristics and clinical outcomes were accessed by integrating whole-genome sequencing data and clinical data. Additionally, 481 lung adenocarcinoma patients were used for the validation based on The Cancer Genome Atlas (TCGA) dataset. Results: A total of 3297 eRNAs with sufficient expression were identified, which were globally upregulated in adenocarcinoma samples compared to matched-adjacent pairs (P = 7.61×10^-3). Further analyses indicated that these upregulated eRNAs were correlated with copy number amplification (CNA) status (Cor = 0.22, P = 0.045), and eRNA-correlated genes were primarily involved in cell cycle and immune system-related pathways. Based on the co-expression analysis of eRNAs with protein-coding genes, we defined 188 functional eRNAs and their correlated genes were overrepresented in cancer driver genes (ER = 1.98, P = 5.95×10^-12) and clinically-actionable genes (ER = 2.19, P = 3.44×10^-4). The eRNA-based consensus clustering further identified a novel molecular subtype with immune deficiency and a high-level of genomic alterations, which was associated with poor clinical outcomes of lung adenocarcinoma patients (OS: HR = 1.91, P = 0.015; PFI: HR = 1.64, P = 0.034). Conclusions: The genome-wide identification and characterization of eRNAs reveal novel regulators for the development of lung cancer, which provides a new biological dimension for the understanding of eRNAs during lung carcinogenesis and emphasize the clinical utility of eRNA-based molecular subtypes in the treatment of lung adenocarcinoma.

SOX2 and squamous cancers

SOX2 is a pleiotropic nuclear transcription factor with major roles in stem cell biology and in development. Over the last 10 years SOX2 has also been implicated as a lineage-specific oncogene, notably in squamous carcinomas but also neurological tumours, particularly glioblastoma. Squamous carcinomas (SQCs) comprise a common group of malignancies for which there are no targeted therapeutic interventions. In this article we review the molecular epidemiological and laboratory evidence linking SOX2 with squamous carcinogenesis, explore in detail the multifaceted impact of SOX2 in SQC, describe areas of uncertainty and highlight areas for potential future research.

FOXO transcription factor family in cancer and metastasis

Forkhead box O (FOXO) transcription factors regulate diverse biological processes, affecting development, metabolism, stem cell maintenance and longevity. They have also been increasingly recognised as tumour suppressors through their ability to regulate genes essential for cell proliferation, cell death, senescence, angiogenesis, cell migration and metastasis. Mechanistically, FOXO proteins serve as key connection points to allow diverse proliferative, nutrient and stress signals to converge and integrate with distinct gene networks to control cell fate, metabolism and cancer development. In consequence, deregulation of FOXO expression and function can promote genetic disorders, metabolic diseases, deregulated ageing and cancer. Metastasis is the process by which cancer cells spread from the primary tumour often via the bloodstream or the lymphatic system and is the major cause of cancer death. The regulation and deregulation of FOXO transcription factors occur predominantly at the post-transcriptional and post-translational levels mediated by regulatory non-coding RNAs, their interactions with other protein partners and co-factors and a combination of post-translational modifications (PTMs), including phosphorylation, acetylation, methylation and ubiquitination. This review discusses the role and regulation of FOXO proteins in tumour initiation and progression, with a particular emphasis on cancer metastasis. An understanding of how signalling networks integrate with the FOXO transcription factors to modulate their developmental, metabolic and tumour-suppressive functions in normal tissues and in cancer will offer a new perspective on tumorigenesis and metastasis, and open up therapeutic opportunities for malignant diseases.

Cross-talk between SOX2 and TGFβ Signaling Regulates EGFR-TKI Tolerance and Lung Cancer Dissemination

Regulation of the stemness factor, SOX2, by cytokine stimuli controls self-renewal and differentiation in cells. Activating mutations in EGFR are proven therapeutic targets for tyrosine kinase inhibitors (TKI) in lung adenocarcinoma, but acquired resistance to TKIs inevitably occurs. The mechanism by which stemness and differentiation signaling emerge in lung cancers to affect TKI tolerance and lung cancer dissemination has yet to be elucidated. Here, we report that cross-talk between SOX2 and TGFβ signaling affects lung cancer cell plasticity and TKI tolerance. TKI treatment favored selection of lung cancer cells displaying mesenchymal morphology with deficient SOX2 expression, whereas SOX2 expression promoted TKI sensitivity and inhibited the mesenchymal phenotype. Preselection of EGFR-mutant lung cancer cells with the mesenchymal phenotype diminished SOX2 expression and TKI sensitivity, whereas SOX2 silencing induced vimentin, but suppressed BCL2L11, expression and promoted TKI tolerance. TGFβ stimulation downregulated SOX2 and induced epithelial-to-mesenchymal transdifferentiation accompanied by increased TKI tolerance, which can interfere with ectopic SOX2 expression. SOX2-positive lung cancer cells exhibited a lower dissemination capacity than their SOX2-negative counterparts. Tumors expressing low SOX2 and high vimentin signature were associated with worse survival outcomes in patients with EGFR mutations. These findings provide insights into how cancer cell plasticity regulated by SOX2 and TGFβ signaling affects EGFR-TKI tolerance and lung cancer dissemination. SIGNIFICANCE: These findings suggest the potential of SOX2 as a prognostic marker in EGFR-mutant lung cancer, as SOX2-mediated cell plasticity regulated by TGFβ stimulation and epigenetic control affects EGFR-TKI tolerance and cancer dissemination.

Functional characterization of SOX2 as an anticancer target

SOX2 is a well-characterized pluripotent factor that is essential for stem cell self-renewal, reprogramming, and homeostasis. The cellular levels of SOX2 are precisely regulated by a complicated network at the levels of transcription, post-transcription, and post-translation. In many types of human cancer, SOX2 is dysregulated due to gene amplification and protein overexpression. SOX2 overexpression is associated with poor survival of cancer patients. Mechanistically, SOX2 promotes proliferation, survival, invasion/metastasis, cancer stemness, and drug resistance. SOX2 is, therefore, an attractive anticancer target. However, little progress has been made in the efforts to discover SOX2 inhibitors, largely due to undruggable nature of SOX2 as a transcription factor. In this review, we first briefly introduced SOX2 as a transcription factor, its domain structure, normal physiological functions, and its involvement in human cancers. We next discussed its role in embryonic development and stem cell-renewal. We then mainly focused on three aspects of SOX2: (a) the regulatory mechanisms of SOX2, including how SOX2 level is regulated, and how SOX2 cross-talks with multiple signaling pathways to control growth and survival; (b) the role of SOX2 in tumorigenesis and drug resistance; and (c) current drug discovery efforts on targeting SOX2, and the future perspectives to discover specific SOX2 inhibitors for effective cancer therapy.

5-Hydroxytryptamine Receptor 1D Aggravates Hepatocellular Carcinoma Progression Through FoxO6 in AKT-Dependent and Independent Manners

Serotonin and its receptors have been shown to play critical regulatory roles in cancer biology. Nevertheless, the contributions of 5-hydroxytryptamine 1D (5-HT1D), an indispensable member of the serotonergic system, to hepatocellular carcinoma (HCC) remain unknown. The present study demonstrated that the 5-HT1D expression level was significantly up-regulated in HCC tissues and cell lines. The 5-HT1D expression level was closely correlated with unfavorable clinicopathological characteristics. Survival analyses show that elevated 5-HT1D expression level predicts poor overall survival and high recurrence probability in HCC patients. Functional studies revealed that 5-HT1D significantly promoted HCC proliferation, epithelial-mesenchymal transition, and metastasis in vitro and in vivo. Mechanistically, 5-HT1D could stabilize PIK3R1 by inhibiting its ubiquitin-mediated degradation. The interaction between 5-HT1D and phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) enhanced the expression of FoxO6 through the PI3K/Akt signaling pathway; FoxO6 could also be directly transcriptionally activated by 5-HT1D in an Akt-independent manner. MicroRNA-599 was found to be an upstream suppressive modulator of 5-HT1D. Additionally, 5-HT1D could attenuate tryptophan hydroxylase 1 expression through the PI3K/Akt/cut-like homeobox 1 axis in HCC. Conclusion: Herein, we uncovered the potent oncogenic effect of 5-HT1D on HCC by interacting with PIK3R1 to activate the PI3K/Akt/FoxO6 pathway, and provided a potential therapeutic target for HCC.

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.

Non-canonical functions of the RB protein in cancer

The canonical model of RB-mediated tumour suppression developed over the past 30 years is based on the regulation of E2F transcription factors to restrict cell cycle progression. Several additional functions have been proposed for RB, on the basis of which a non-canonical RB pathway can be described. Mechanistically, the non-canonical RB pathway promotes histone modification and regulates chromosome structure in a manner distinct from cell cycle regulation. These functions have implications for chemotherapy response and resistance to targeted anticancer agents. This Opinion offers a framework to guide future studies of RB in basic and clinical research.

KIF5B-RET Oncoprotein Signals through a Multi-kinase Signaling Hub

Gene fusions are increasingly recognized as important cancer drivers. The KIF5B-RET gene has been identified as a primary driver in a subset of lung adenocarcinomas. Targeting human KIF5B-RET to epithelia in Drosophila directed multiple aspects of transformation, including hyperproliferation, epithelial-to-mesenchymal transition, invasion, and extension of striking invadopodia-like processes. The KIF5B-RET-transformed human bronchial cell line showed similar aspects of transformation, including invadopodia-like processes. Through a combination of genetic and biochemical studies, we demonstrate that the kinesin and kinase domains of KIF5B-RET act together to establish an emergent microtubule and RAB-vesicle-dependent RET-SRC-EGFR-FGFR signaling hub. We demonstrate that drugs designed to inhibit RET alone work poorly in KIF5B-RET-transformed cells. However, combining the RET inhibitor sorafenib with drugs that target EGFR, microtubules, or FGFR led to strong efficacy in both Drosophila and human cell line KIF5B-RET models. This work demonstrates the utility of exploring the full biology of fusions to identify rational therapeutic strategies.

Patient-derived conditionally reprogrammed cells maintain intra-tumor genetic heterogeneity

Preclinical in vitro models provide an essential tool to study cancer cell biology as well as aid in translational research, including drug target identification and drug discovery efforts. For any model to be clinically relevant, it needs to recapitulate the biology and cell heterogeneity of the primary tumor. We recently developed and described a conditional reprogramming (CR) cell technology that addresses many of these needs and avoids the deficiencies of most current cancer cell lines, which are usually clonal in origin. Here, we used the CR cell method to generate a collection of patient-derived cell cultures from non-small cell lung cancers (NSCLC). Whole exome sequencing and copy number variations are used for the first time to address the capability of CR cells to keep their tumor-derived heterogeneity. Our results indicated that these primary cultures largely maintained the molecular characteristics of the original tumors. Using a mutant-allele tumor heterogeneity (MATH) score, we showed that CR cells are able to keep and maintain most of the intra-tumoral heterogeneity, suggesting oligoclonality of these cultures. CR cultures therefore represent a pre-clinical lung cancer model for future basic and translational studies.

Salivary glands regenerate after radiation injury through SOX2-mediated secretory cell replacement

Salivary gland acinar cells are routinely destroyed during radiation treatment for head and neck cancer that results in a lifetime of hyposalivation and co-morbidities. A potential regenerative strategy for replacing injured tissue is the reactivation of endogenous stem cells by targeted therapeutics. However, the identity of these cells, whether they are capable of regenerating the tissue, and the mechanisms by which they are regulated are unknown. Using in vivo and ex vivo models, in combination with genetic lineage tracing and human tissue, we discover a SOX2+ stem cell population essential to acinar cell maintenance that is capable of replenishing acini after radiation. Furthermore, we show that acinar cell replacement is nerve dependent and that addition of a muscarinic mimetic is sufficient to drive regeneration. Moreover, we show that SOX2 is diminished in irradiated human salivary gland, along with parasympathetic nerves, suggesting that tissue degeneration is due to loss of progenitors and their regulators. Thus, we establish a new paradigm that salivary glands can regenerate after genotoxic shock and do so through a SOX2 nerve-dependent mechanism.

Leveraging and coping with uncertainty in the response of individual cells to therapy

Non-genetic heterogeneity fluctuates over diverse timescales, ranging from hours to months. In specific cases, such variability can profoundly impact the response of cell populations to therapy, in both antibiotic treatments in bacteria and chemotherapy in cancer. It is thus critical to understand the way phenotypes fluctuate in cell populations and the molecular sources of phenotypic diversity. Technical and analytical breakthroughs in the study of single cells have leveraged cellular heterogeneity to gain phenomenological and mechanistic insights of the phenotypic transitions that occur within isogenic cell populations over time. Such an understanding moves forward our ability to design therapeutic strategies with the explicit goal of preventing and controlling the selective expansion and stabilization of drug-tolerant phenotypic states.

Up-regulation of YPEL1 and YPEL5 and down-regulation of ITGA2 in erlotinib-treated EGFR-mutant non-small cell lung cancer: A bioinformatic analysis

PURPOSE

This study aimed to identify genes with significant alteration following treatment of epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) with tyrosine kinase inhibitors (TKIs).

METHODS

We downloaded microarray data of GSE67051 from the Gene Expression Omnibus (GEO) database. Genes with differential expression were identified in two groups: erlotinib-treated versus DMSO-treated PC9 cells and erlotinib-treated versus DMSO-treated HCC827 cells. Functional enrichment analysis and protein-protein interaction (PPI) network were performed on the overlapping differentially expressed genes (DEGs). Additionally, miRNAs that can regulate the DEGs were predicted. Small-molecule drugs, with possible synergistic or antagonistic actions with respect to erlotinib, were screened; data validation using another dataset was conducted.

RESULTS

In total, 1466 and 839 DEGs were identified in the aforementioned comparison groups, respectively, among which 267 overlapping up-regulated and 73 down-regulated were observed. The overlapping up- and down-regulated genes were significantly associated with different functions and pathways. ITGA2 had higher centrality scores in the PPI network. Seventy small-molecule drugs, with either possible synergistic or antagonistic roles with erlotinib, were identified. Moreover, up-regulated YPEL1, YPEL2, and YPEL5 were enriched in the miRNA-target regulatory network. Implementing data validation, we found YPEL1, YPEL5, and ITGA2 displayed similar expression profiles in the two datasets.

CONCLUSION

YPEL1 and YPEL5 may be related to the action of erlotinib, and down-regulation of ITGA2 may be associated with the development of acquired resistance to erlotinib in EGFR-mutant NSCLCs. Furthermore, several small-molecule drugs that may have synergistic and antagonistic roles with erlotinib were identified.

YAP1 and COX2 Coordinately Regulate Urothelial Cancer Stem-like Cells

Overcoming acquired drug resistance remains a core challenge in the clinical management of human cancer, including in urothelial carcinoma of the bladder (UCB). Cancer stem-like cells (CSC) have been implicated in the emergence of drug resistance but mechanisms and intervention points are not completely understood. Here, we report that the proinflammatory COX2/PGE2 pathway and the YAP1 growth-regulatory pathway cooperate to recruit the stem cell factor SOX2 in expanding and sustaining the accumulation of urothelial CSCs. Mechanistically, COX2/PGE2 signaling induced promoter methylation of let-7, resulting in its downregulation and subsequent SOX2 upregulation. YAP1 induced SOX2 expression more directly by binding its enhancer region. In UCB clinical specimens, positive correlations in the expression of SOX2, COX2, and YAP1 were observed, with coexpression of COX2 and YAP1 particularly commonly observed. Additional investigations suggested that activation of the COX2/PGE2 and YAP1 pathways also promoted acquired resistance to EGFR inhibitors in basal-type UCB. In a mouse xenograft model of UCB, dual inhibition of COX2 and YAP1 elicited a long-lasting therapeutic response by limiting CSC expansion after chemotherapy and EGFR inhibition. Our findings provide a preclinical rationale to target these pathways concurrently with systemic chemotherapy as a strategy to improve the clinical management of UCB.Significance: These findings offer a preclinical rationale to target the COX2 and YAP1 pathways concurrently with systemic chemotherapy to improve the clinical management of UCB, based on evidence that these two pathways expand cancer stem-like cell populations that mediate resistance to chemotherapy. Cancer Res; 78(1); 168-81. ©2017 AACR.

Members of FOX family could be drug targets of cancers

FOX families play important roles in biological processes, including metabolism, development, differentiation, proliferation, apoptosis, migration, invasion and longevity. Here we are focusing on roles of FOX members in cancers, FOX members and drug resistance, FOX members and stem cells. Finally, FOX members as drug targets of cancer treatment were discussed. Future perspectives of FOXC1 research were described in the end.

Role of Forkhead Box Class O proteins in cancer progression and metastasis

It is now widely accepted that several gene alterations including transcription factors are critically involved in cancer progression and metastasis. Forkhead Box Class O proteins (FoxOs) including FoxO1/FKHR, FoxO3/FKHRL1, FoxO4/AFX and FoxO6 transcription factors are known to play key roles in proliferation, apoptosis, metastasis, cell metabolism, aging and cancer biology through their phosphorylation, ubiquitination, acetylation and methylation. Though FoxOs are proved to be mainly regulated by upstream phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3 K)/Akt signaling pathway, the role of FoxOs in cancer progression and metastasis still remains unclear so far. Thus, with previous experimental evidences, the present review discussed the role of FoxOs in association with metastasis related molecules including cannabinoid receptor 1 (CNR1), Cdc25A/Cdk2, Src, serum and glucocorticoid inducible kinases (SGKs), CXCR4, E-cadherin, annexin A8 (ANXA8), Zinc finger E-box-binding homeobox 2 (ZEB2), human epidermal growth factor receptor 2 (HER2) and mRNAs such as miR-182, miR-135b, miR-499-5p, miR-1274a, miR-150, miR-34b/c and miR-622, subsequently analyzed the molecular mechanism of some natural compounds targeting FoxOs and finally suggested future research directions in cancer progression and metastasis.

Cancer Cell Plasticity: Rapid Reversal of Chemosensitivity and Expression of Stemness Markers in Lung and Breast Cancer Tumorspheres

In cancer cells, the reversible nature of the stemness status in terms of chemoresistance has been poorly characterized. In this study, we have simulated one cycle of environmental conditions to study such reversibility by first generating floating tumorspheres (FTs) from lung and breast cancer cells by culturing them in serum-free media without the addition of any external mitogenic stimulation, and subsequently (after 2 weeks) re-incubating them back in serum-containing media to simulate routine culture conditions (RCCs). We found that cancer cells are extremely plastic: cells grown under RCCs become multidrug-resistant when grown as FTs, but upon re-incubation under RCCs quickly re-attach and lose the acquired resistance. These phenotypic changes are accompanied by concomitant changes in the expression of key proteins associated with multiple pathways important for chemoresistance, survival, and stemness maintenance. Therefore, our strategy provides an excellent experimental model to study environmental factors that modulate the plasticity of cancer cells. J. Cell. Physiol. 232: 2280-2286, 2017. © 2016 Wiley Periodicals, Inc.

Adaptive and Acquired Resistance to EGFR Inhibitors Converge on the MAPK Pathway

Both adaptive and acquired resistance significantly limits the efficacy of the epidermal growth factor receptor (EGFR) kinase inhibitors. However, the distinct or common mechanisms of adaptive and acquired resistance have not been fully characterized. Here, through systematic modeling of erlotinib resistance in lung cancer, we found that feedback reactivation of MAPK signaling following erlotinib treatment, which was dependent on the MET receptor, contributed to the adaptive resistance of EGFR inhibitors. Interestingly, acquired resistance to erlotinib was also associated with the MAPK pathway activation as a result of CRAF or NRAS amplification. Consequently, combined inhibition of EGFR and MAPK impeded the development of both adaptive and acquired resistance. These observations demonstrate that adaptive and acquired resistance to EGFR inhibitors can converge on the same pathway and credential cotargeting EGFR and MAPK as a promising therapeutic approach in EGFR mutant tumors.