Nuclear trafficking of EGFR by Vps34 represses Arf expression to promote lung tumor cell survival

Exploring Retrograde Trafficking: Mechanisms and Consequences in Cancer and Disease

Retrograde trafficking (RT) orchestrates the intracellular movement of cargo from the plasma membrane, endosomes, Golgi or endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC) in an inward/ER-directed manner. RT works as the opposing movement to anterograde trafficking (outward secretion), and the two work together to maintain cellular homeostasis. This is achieved through maintaining cell polarity, retrieving proteins responsible for anterograde trafficking and redirecting proteins that become mis-localised. However, aberrant RT can alter the correct location of key proteins, and thus inhibit or indeed change their canonical function, potentially causing disease. This review highlights the recent advances in the understanding of how upregulation, downregulation or hijacking of RT impacts the localisation of key proteins in cancer and disease to drive progression. Cargoes impacted by aberrant RT are varied amongst maladies including neurodegenerative diseases, autoimmune diseases, bacterial and viral infections (including SARS-CoV-2), and cancer. As we explore the intricacies of RT, it becomes increasingly apparent that it holds significant potential as a target for future therapies to offer more effective interventions in a wide range of pathological conditions.

Targeting Class I-II-III PI3Ks in Cancer Therapy: Recent Advances in Tumor Biology and Preclinical Research

Phosphatidylinositol-3-kinase (PI3K) enzymes, producing signaling phosphoinositides at plasma and intracellular membranes, are key in intracellular signaling and vesicular trafficking pathways. PI3K is a family of eight enzymes divided into three classes with various functions in physiology and largely deregulated in cancer. Here, we will review the recent evidence obtained during the last 5 years on the roles of PI3K class I, II and III isoforms in tumor biology and on the anti-tumoral action of PI3K inhibitors in preclinical cancer models. The dependency of tumors to PI3K isoforms is dictated by both genetics and context (e.g., the microenvironment). The understanding of class II/III isoforms in cancer development and progression remains scarce. Nonetheless, the limited available data are consistent and reveal that there is an interdependency between the pathways controlled by all PI3K class members in their role to promote cancer cell proliferation, survival, growth, migration and metabolism. It is unknown whether this feature contributes to partial treatment failure with isoform-selective PI3K inhibitors. Hence, a better understanding of class II/III functions to efficiently inhibit their positive and negative interactions with class I PI3Ks is needed. This research will provide the proof-of-concept to develop combination treatment strategies targeting several PI3K isoforms simultaneously.

Altered splicing of ATG16-L1 mediates acquired resistance to tyrosine kinase inhibitors of EGFR by blocking autophagy in non-small cell lung cancer

Despite the initial efficacy of using tyrosine kinase inhibitors of epidermal growth factor receptor (EGFR-TKIs) for treating patients with non-small cell lung cancer (NSCLC), resistance inevitably develops. Recent studies highlight a link between alternative splicing and cancer drug response. Therefore, we aimed to identify deregulated splicing events that play a role in resistance to EGFR-TKI. By using RNA sequencing, reverse transcription PCR (RT-PCR) and RNA interference, we showed that overexpression of a splice variant of the autophagic gene ATG16-L1 that retains exon 8 and encodes the β-isoform of autophagy-related protein 16-1 (ATG16-L1-β) concurs acquired resistance to EGFR-TKI in NSCLC cells. Using matched biopsies, we found increased levels of ATG16-L1-β at the time of progression in 3 of 11 NSCLC patients treated with EGFR-TKI. Mechanistically, gefitinib-induced autophagy was impaired in resistant cells that accumulated ATG16-L1-β. Neutralization of ATG16-L1-β restored autophagy in response to gefitinib, induced apoptosis and inhibited the growth of in ovo tumor xenografts. Conversely, overexpression of ATG16-L1-β in parental sensitive cells prevented gefitinib-induced autophagy and increased cell survival. These results support a role for defective autophagy in acquired resistance to EGFR-TKIs and identify splicing regulation of ATG16-L1 as a therapeutic vulnerability that could be explored for improving EGFR-targeted cancer therapy.

The Role of Phosphatidylinositol 3-Kinase Catalytic Subunit Type 3 in the Pathogenesis of Human Cancer

Phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3), the mammalian ortholog of yeast vesicular protein sorting 34 (Vps34), belongs to the phosphoinositide 3-kinase (PI3K) family. PIK3C3 can phosphorylate phosphatidylinositol (PtdIns) to generate phosphatidylinositol 3-phosphate (PI3P), a phospholipid central to autophagy. Inhibition of PIK3C3 successfully inhibits autophagy. Autophagy maintains cell survival when modifications occur in the cellular environment and helps tumor cells resist metabolic stress and cancer treatment. In addition, PIK3C3 could induce oncogenic transformation and enhance tumor cell proliferation, growth, and invasion through mechanisms independent of autophagy. This review addresses the structural and functional features, tissue distribution, and expression pattern of PIK3C3 in a variety of human tumors and highlights the underlying mechanisms involved in carcinogenesis. The implications in cancer biology, patient prognosis prediction, and cancer therapy are discussed. Altogether, the discovery of pharmacological inhibitors of PIK3C3 could reveal novel strategies for improving treatment outcomes for PIK3C3-mediated human diseases.

Casein kinase TbCK1.2 regulates division of kinetoplast DNA, and movement of basal bodies in the African trypanosome

The single mitochondrial nucleoid (kinetoplast) of Trypanosoma brucei is found proximal to a basal body (mature (mBB)/probasal body (pBB) pair). Kinetoplast inheritance requires synthesis of, and scission of kinetoplast DNA (kDNA) generating two kinetoplasts that segregate with basal bodies into daughter cells. Molecular details of kinetoplast scission and the extent to which basal body separation influences the process are unavailable. To address this topic, we followed basal body movements in bloodstream trypanosomes following depletion of protein kinase TbCK1.2 which promotes kinetoplast division. In control cells we found that pBBs are positioned 0.4 um from mBBs in G1, and they mature after separating from mBBs by at least 0.8 um: mBB separation reaches ~2.2 um. These data indicate that current models of basal body biogenesis in which pBBs mature in close proximity to mBBs may need to be revisited. Knockdown of TbCK1.2 produced trypanosomes containing one kinetoplast and two nuclei (1K2N), increased the percentage of cells with uncleaved kDNA 400%, decreased mBB spacing by 15%, and inhibited cytokinesis 300%. We conclude that (a) separation of mBBs beyond a threshold of 1.8 um correlates with division of kDNA, and (b) TbCK1.2 regulates kDNA scission. We propose a Kinetoplast Division Factor hypothesis that integrates these data into a pathway for biogenesis of two daughter mitochondrial nucleoids.

Time series expression pattern of key genes reveals the molecular process of esophageal cancer

Background: Esophageal cancer is one of the most poorly diagnosed and fatal cancers in the world. Although a series of studies on esophageal cancer have been reported, the molecular pathogenesis of the disease is still elusive. Aim: To investigate the molecular process of esophageal cancer comprehensively and deeply. Methods: Differential expression analysis was performed to identify differentially expressed genes (DEGs) in different stages of esophageal cancer. Then exacting gene interaction modules and hub genes were identified in module interaction network. Further, though survival analysis, methylation analysis, pivot analysis, and enrichment analysis, some important molecules and related function or pathway were identified to elucidate potential mechanism in esophageal cancer. Results: A total of 7457 DEGs and 14 gene interaction modules were identified. These module genes were significantly involved in the positive regulation of protein transport, gastric acid secretion, insulin-like growth factor receptor binding and other biological processes (BPs), as well as p53 signaling pathway, ERBB signaling pathway and epidermal growth factor receptor (EGFR) signaling pathway. Then, transcription factors (TFs) (including HIF1A) and ncRNAs (including CRNDE and hsa-mir-330-3p) significantly regulate dysfunction modules were identified. Further, survival analysis showed that GNGT2 was closely related to survival of esophageal cancer. And DEGs with strong methylation regulation ability were identified, including SST and SH3GL2. Conclusion: These works not only help us to reveal the potential regulatory factors in the development of disease, but also deepen our understanding of its deterioration mechanism.

Roles of ARF tumour suppressor protein in lung cancer: time to hit the nail on the head!

Owing to its poor prognosis, the World Health Organization (WHO) lists lung cancer on top of the list when it comes to growing mortality rates and incidence. Usually, there are two types of lung cancer, small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC), which also includes adenocarcinoma, squamous cell carcinoma and large cell carcinomas. ARF, also known in humans as p14ARF and in the mouse as p19ARF, is a nucleolar protein and a member of INK4, a family of cyclin-independent kinase inhibitors (CKI). These genes are clustered on chromosome number 9p21 within the locus of CDKN2A. NSCLC has reported the role of p14ARF as a potential target. p14ARF has a basic mechanism to inhibit mouse double minute 2 protein that exhibits inhibitory action on p53, a phosphoprotein tumour suppressor, thus playing a role in various tumour-related activities such as growth inhibition, DNA damage, autophagy, apoptosis, cell cycle arrest and others. Extensive cancer research is ongoing and updated reports regarding the role of ARF in lung cancer are available. This article summarizes the available lung cancer ARF data, its molecular mechanisms and its associated signalling pathways. Attempts have been made to show how p14ARF functions in different types of lung cancer providing a thought to look upon ARF as a new target for treating the debilitating condition of lung cancer.

An iron-dependent metabolic vulnerability underlies VPS34-dependence in RKO cancer cells

VPS34 is a key regulator of endomembrane dynamics and cargo trafficking, and is essential in cultured cell lines and in mice. To better characterize the role of VPS34 in cell growth, we performed unbiased cell line profiling studies with the selective VPS34 inhibitor PIK-III and identified RKO as a VPS34-dependent cellular model. Pooled CRISPR screen in the presence of PIK-III revealed endolysosomal genes as genetic suppressors. Dissecting VPS34-dependent alterations with transcriptional profiling, we found the induction of hypoxia response and cholesterol biosynthesis as key signatures. Mechanistically, acute VPS34 inhibition enhanced lysosomal degradation of transferrin and low-density lipoprotein receptors leading to impaired iron and cholesterol uptake. Excess soluble iron, but not cholesterol, was sufficient to partially rescue the effects of VPS34 inhibition on mitochondrial respiration and cell growth, indicating that iron limitation is the primary driver of VPS34-dependency in RKO cells. Loss of RAB7A, an endolysosomal marker and top suppressor in our genetic screen, blocked transferrin receptor degradation, restored iron homeostasis and reversed the growth defect as well as metabolic alterations due to VPS34 inhibition. Altogether, our findings suggest that impaired iron mobilization via the VPS34-RAB7A axis drive VPS34-dependence in certain cancer cells.

How microplastic components influence the immune system and impact on children health: Focus on cancer

BACKGROUND

As a result of human socioeconomic activity, industrial wastes have increased distressingly. Plastic pollution is globally distributed across the world due to its properties of buoyancy and durability. A big health hazard is the sorption of toxicants to plastic while traveling through the environment. Two broad classes of plastic-related chemicals are of critical concern for human health-bisphenols and phthalates. Bisphenol A (BPA) is an endocrine-disruptor compound (EDC) with estrogenic activity. It is used in the production of materials that are used daily. The endocrine modulating activity of BPA and its effects on reproductive health has been widely studied. BPA also has effects on the immune system; however, they are poorly investigated and the available data are inconclusive. Phthalates are also EDCs used as plasticizers in a wide array of daily-use products. Since these compounds are not covalently bound to the plastic matrix, they easily leach out from it, leading to high human exposure. These compounds exert several cell effects through modulating different endocrine pathways, such as estrogen, androgen, peroxisome proliferator-activated receptor gamma, and arylhydrocarbon receptor pathways. The exposure to both classes of plastic derivatives during critical periods has detrimental effects on human health.

METHODS

In this review, we have compiled the most important of their perinatal effects on the function of the immune system and their relationship to the development of different types of cancer.

RESULTS/CONCLUSION

The administration of bisphenols and phthalates during critical stages of development affects important immune system components, and the immune function; which might be related to the development of different diseases including cancer.

Post-Translational Regulation of ARF: Perspective in Cancer

Tumorigenesis can be induced by various stresses that cause aberrant DNA mutations and unhindered cell proliferation. Under such conditions, normal cells autonomously induce defense mechanisms, thereby stimulating tumor suppressor activation. ARF, encoded by the CDKN2a locus, is one of the most frequently mutated or deleted tumor suppressors in human cancer. The safeguard roles of ARF in tumorigenesis are mainly mediated via the MDM2-p53 axis, which plays a prominent role in tumor suppression. Under normal conditions, low p53 expression is stringently regulated by its target gene, MDM2 E3 ligase, which induces p53 degradation in a ubiquitin-proteasome-dependent manner. Oncogenic signals induced by MYC, RAS, and E2Fs trap MDM2 in the inhibited state by inducing ARF expression as a safeguard measure, thereby activating the tumor-suppressive function of p53. In addition to the MDM2-p53 axis, ARF can also interact with diverse proteins and regulate various cellular functions, such as cellular senescence, apoptosis, and anoikis, in a p53-independent manner. As the evidence indicating ARF as a key tumor suppressor has been accumulated, there is growing evidence that ARF is sophisticatedly fine-tuned by the diverse factors through transcriptional and post-translational regulatory mechanisms. In this review, we mainly focused on how cancer cells employ transcriptional and post-translational regulatory mechanisms to manipulate ARF activities to circumvent the tumor-suppressive function of ARF. We further discussed the clinical implications of ARF in human cancer.

Coexisting EGFR and TP53 Mutations in Lung Adenocarcinoma Patients Are Associated With COMP and ITGB8 Upregulation and Poor Prognosis

The heterogeneity of lung adenocarcinoma is driven by key mutations in oncogenes. To determine the gene expression, single nucleotide polymorphisms, and co-mutations participating in the initiation and progression of lung adenocarcinoma, we comprehensively analyzed the data of 491 patients from The Cancer Genome Atlas. Using log-rank and Kruskal-Wallis analysis, Oncoprint, Kaplan-Meier survival plots, and a nomogram, we found that EGFR^L858R with co-mutation TP53 was significant prognostic determinant versus that with co-wild TP53 (hazard ratio, 2.77, P = 0.012). Further gene co-expression network and functional enrichment analysis indicated that co-mutation of EGFR^L858R/TP53 increases the expression of COMP and ITGB8, which are involved in extracellular matrix organization and cell surface receptor signaling pathways, thus contributing to poor prognosis in lung adenocarcinoma. Validation was performed using three GEO profiles along with colony formation and CCK-8 assays for proliferation, transwell and wound-healing for migration in transfected H1299 and A549 cell lines. To the best of our knowledge, these results are the first to indicate that patients harboring the co-mutation of EGFR^L858R/TP53 show increased expression of COMP and ITGB8, which participate in extracellular matrix dysfunction and can be used as prognostic biomarkers in patients with lung adenocarcinoma.

Transketolase (TKT) activity and nuclear localization promote hepatocellular carcinoma in a metabolic and a non-metabolic manner

BACKGROUND

Metabolic reprogramming is one of the hallmarks of cancer cells. The pentose phosphate pathway (PPP), a branch of glycolysis, is an important metabolic pathway for the survival and biosynthesis of cancer cells. Transketolase (TKT) is a key enzyme in the non-oxidative phase of PPP. The mechanistic details of TKT in hepatocellular carcinoma (HCC) development remain unclear.

METHODS

TKT level and subcellular location were examined in HCC cell lines and tissue samples. We established the TKT overexpression and knocking-down stable cells in HCC cell lines. Proliferation, migration, viability and enzyme activity assays in vitro, tumor growth and metastasis assays in vivo were employed to test the effects of TKT on HCC development. GFP-tagged TKT truncations and mutants were used to locate the nuclear localization sequence (NLSs) of TKT. Cross-linking co-IP/MS was applied to identify the interaction proteins of nuclear TKT.

RESULTS

We showed that TKT increased the proliferation and migration of HCC cells, as well as the viability under oxidative stress in vitro and accelerated the growth and metastasis of HCC cells in vivo. We found as a key enzyme of PPP, TKT could promote the proliferation, cell cycle, migration and viability by regulating the metabolic flux. Moreover, it was firstly reported that unlike other key enzymes in PPP, TKT showed a strong nuclear localization in HCC cells. We found not only high TKT expression, but also its nuclear localization was a prediction for poor prognosis of HCC patients. We further identified the nuclear localization sequences (NLS) for TKT and demonstrated the NLS mutations decreased the pro-tumor function of TKT independent of the enzyme activity. Cross-linking Co-IP/MS showed that nuclear TKT interacted with kinases and transcriptional coregulators such as EGFR and MAPK3, which are associated with cell activation or stress response processes. EGF treatment significantly increased the viability and proliferation of HCC cells in the enzyme-inactivating mutation TKT-D155A overexpression cells but not in the NLS-D155A double mutant group, which could be blocked by EGFR inhibitor erlotinib treatment.

CONCLUSIONS

Our research suggests that in addition to the metabolic manner, TKT can promote the development of HCC in a non-metabolic manner via its nuclear localization and EGFR pathway.

[Nuclear EGFR: a new mode of oncogenic signalling in cancer]

EGFR (Epidermal Growth Factor Receptor) is one of the most studied molecules in biology. From its early identification and cloning to the discovery of its role in cancer, it has been at the forefront of our understanding of Receptor Tyrosine Kinase (RTK) and cell signals that induce homeostasis, but when overexpressed, facilitate tumorigenesis. While the biological functions of EGFR traditionally involve the activation of a signaling network from the plasma membrane that includes activation of the RAS/MAPK/ERK, PI3K/AKT and STATS pathways, a new mode of EGFR signaling has been progressively decoded in which membrane-associated EGFR is transported after endocytosis from cell surface to the nucleus through endocytosis, retrograde trafficking to the Golgi, the endoplasmic reticulum and the inner nuclear membrane through a series of proteic interactions. In the nucleus, EGFR acts as a transcriptional regulator, a kinase and a physical interactor, transmits signals and is involved in multiple biological functions, including cell proliferation, tumor progression, DNA repair and replication, and resistance to cancer therapies. In this review, we will summarize current knowledge of the EGFR nuclear signaling network, including how it is delivered to the nucleus, the functions it serves in the nucleus and how these functions affect cancer progression, survival and the response to treatment.

ARF promotes the degradation of the Epidermal Growth Factor Receptor by the lysosome

Epidermal Growth Factor Receptor (EGFR) signaling regulates multiple cellular processes including proliferation, survival and apoptosis, and is attenuated by lysosomal receptor degradation. EGFR is a potent oncogene and activating mutations of EGFR are critical determinants of oncogenic transformation as well as therapeutic targets in non-small cell lung cancer. We previously demonstrated that wild type and mutant EGFRs repress the expression of the ARF tumor suppressor to promote the survival of lung tumor cells. In this study, using transient transfection systems in CHO EGFR-null cells as well as in various lung tumor cell lines carrying wild type or activated mutant EGFR, we show that ARF downregulates the expression of EGFR protein by reducing its half life. In wild type EGFR cells, ARF promotes canonical lysosomal degradation of the receptor through enhanced phosphorylation of EGFR-Y1045 and Cbl-Y731. In contrast, in mutant EGFR cells, ARF induces EGFR degradation by activating a non-canonical AKT-dependent lysosomal pathway. Taken together, these results uncover a feedback loop by which ARF may control EGFR turnover to restrain oncogenic signaling. They also highlight distinct degradation promoting pathways between wild type and mutant EGFRs in response to ARF.

Regulatory Network of ARF in Cancer Development

ARF is a tumor suppressor protein that has a pivotal role in the prevention of cancer development through regulating cell proliferation, senescence, and apoptosis. As a factor that induces senescence, the role of ARF as a tumor suppressor is closely linked to the p53-MDM2 axis, which is a key process that restrains tumor formation. Thus, many cancer cells either lack a functional ARF or p53, which enables them to evade cell oncogenic stress-mediated cycle arrest, senescence, or apoptosis. In particular, the ARF gene is a frequent target of genetic and epigenetic alterations including promoter hyper-methylation or gene deletion. However, as many cancer cells still express ARF, pathways that negatively modulate transcriptional or post-translational regulation of ARF could be potentially important means for cancer cells to induce cellular proliferation. These recent findings of regulators affecting ARF protein stability along with its low levels in numerous human cancers indicate the significance of an ARF post-translational mechanism in cancers. Novel findings of regulators stimulating or suppressing ARF function would provide new therapeutic targets to manage cancer- and senescence-related diseases. In this review, we present the current knowledge on the regulation and alterations of ARF expression in human cancers, and indicate the importance of regulators of ARF as a prognostic marker and in potential therapeutic strategies.

The nuclear transportation routes of membrane-bound transcription factors

Membrane-bound transcription factors (MTFs) are transcription factors (TFs) that are anchored in membranes in a dormant state. Activated by external or internal stimuli, MTFs are released from parent membranes and are transported to the nucleus. Existing research indicates that some plasma membrane (PM)-bound proteins and some endoplasmic reticulum (ER) membrane-bound proteins have the ability to enter the nucleus. Upon specific signal recognition cues, some PM-bound TFs undergo proteolytic cleavage to liberate the intracellular fragments that enter the nucleus to control gene transcription. However, lipid-anchored PM-bound proteins enter the nucleus in their full length for depalmitoylation. In addition, some PM-bound TFs exist as full-length proteins in cell nucleus via trafficking to the Golgi and the ER, where membrane-releasing mechanisms rely on endocytosis. In contrast, the ER membrane-bound TFs relocate to the nucleus directly or by trafficking to the Golgi. In both of these pathways, only the fragments of the ER membrane-bound TFs transit to the nucleus. Several different nuclear trafficking modes of MTFs are summarized in this review, providing an effective supplement to the mechanisms of signal transduction and gene regulation. Moreover, targeting intracellular movement pathways of disease-associated MTFs may significantly improve the survival of patients.

Nuclear translocation of IGF1R by intracellular amphiregulin contributes to the resistance of lung tumour cells to EGFR-TKI

Many Receptor Tyrosine Kinases translocate from the cell surface to the nucleus in normal and pathological conditions, including cancer. Here we report the nuclear expression of insulin-like growth factor-1 receptor (IGF1R) in primary human lung tumours. Using lung cancer cell lines and lung tumour xenografts, we demonstrate that the epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) gefitinib induces the nuclear accumulation of IGF1R in mucinous lung adenocarcinoma by a mechanism involving the intracellular re-localization of the growth factor amphiregulin. Amphiregulin allows the binding of IGF1R to importin-β1 and promotes its nuclear transport. The nuclear accumulation of IGF1R by amphiregulin induces cell cycle arrest through p21^WAF1/CIP1 upregulation, and prevents the induction of apoptosis in response to gefitinib. These results identify amphiregulin as the first nuclear localization signal-containing protein that interacts with IGF1R and allows its nuclear translocation. Furthermore they indicate that nuclear expression of IGF1R contributes to EGFR-TKI resistance in lung cancer.

The molecular mechanisms of action of the endocrine disrupting chemical bisphenol A in the development of cancer

The endocrine disrupting chemical (EDC) is an exogenous substance or mixture that alters the function of the endocrine system and consequently causes adverse effects in intact organisms. Bisphenol A (BPA), one of the most common endocrine disrupting chemicals is a carbon-based synthetic compound used in the production of water bottles, cans, and teeth suture materials. It is known to be a xenoestrogen as it interacts with estrogen receptors and acts as agonist or antagonist via estrogen receptor-dependent signaling pathways. BPA has been associated with serious health effects in humans and wildlife. It elicits several endocrine disorders and plays a role in the pathogenesis of several hormone-dependent tumors such as breast, ovarian, prostate cancer and others. More complicate to this picture, its effects rely on several and diverse molecular and epigenetic mechanisms that converge upon endocrine and reproductive systems. The present review gives an overview of general hazards of BPA, its epigenetic modifications and the molecular mechanisms of BPA action in different types of cancers as the increase in information about responses and action mechanisms of BPA may bring a better understanding of the risks of BPA exposure in humans and provide an important platform on which human health can be improved.

A Small Organic Molecule Blocks EGFR Transport into the Nucleus by the Nonclassical Pathway Resulting in Repression of Cancer Invasion

In addition to the traditional epidermal growth factor receptor (EGFR) signaling pathways, nuclear EGFR has been shown to control multiple cellular functions, including cell proliferation and invasion. It has been reported that EGFR is transported into the nucleus after forming a complex with KPNA/KPNB1 or KPNB1. Herein, it is shown that EGFR can interact with both KP and KPNA, but EGF-activated EGFR mostly binds with KPNB1 through the pull-down assay. Also, a small organic molecule (1), an effective binder of KPNB1, inhibits the interaction between EGFR and KPNB1 in the nonclassical transport pathway, but not KPNA. Furthermore, treatment of cancer cells with 1 noticeably blocks the nuclear entry of EGFR, which results in significant suppression of invasion by lung cancer H1299 cells. These findings show that 1 is an effective inhibitor of EGFR/KPNB1 interactions in vitro, it may be used in cellular studies as a tool to determine the role of nuclear EGFR, and it is a drug candidate.

Epigenetic silencing of tumor suppressor candidate 3 confers adverse prognosis in early colorectal cancer

Colorectal cancer (CRC) is a biologically and clinically heterogeneous disease. Even though many recurrent genomic alterations have been identified that may characterize distinct subgroups, their biological impact and clinical significance as prognostic indicators remain to be defined. The tumor suppressor candidate-3 (TUSC3/N33) locates to a genomic region frequently deleted or silenced in cancers. TUSC3 is a subunit of the oligosaccharyltransferase (OST) complex at the endoplasmic reticulum (ER) which catalyzes bulk N-glycosylation of membrane and secretory proteins. However, the consequences of TUSC3 loss are largely unknown. Thus, the aim of the study was to characterize the functional and clinical relevance of TUSC3 expression in CRC patients' tissues (n=306 cases) and cell lines. TUSC3 mRNA expression was silenced by promoter methylation in 85 % of benign adenomas (n=46 cases) and 35 % of CRCs (n =74 cases). Epidermal growth factor receptor (EGFR) was selected as one exemplary ER-derived target protein of TUSC3-mediated posttranslational modification. We found that TUSC3 inhibited EGFR-signaling and promoted apoptosis in human CRC cells, whereas TUSC3 siRNA knock-down increased EGFR-signaling. Accordingly, in stage I/II node negative CRC patients (n=156 cases) loss of TUSC3 protein expression was associated with poor overall survival. In sum, our data suggested that epigenetic silencing of TUSC3 may be useful as a molecular marker for progression of early CRC.

MUC1 induces acquired chemoresistance by upregulating ABCB1 in EGFR-dependent manner

Chemoresistance contributes to cancer relapse and increased mortality in a variety of cancer types, raising a pressing need to better understand the underlying mechanism. MUC1 is abnormally overexpressed in numerous carcinomas and associated with poor prognosis. However, the functional significance of MUC1 in chemoresistance has not been fully elucidated. Here, we showed that MUC1 expression was considerably induced in cells that had acquired chemoresistance at both transcriptional and post-translational levels. Using gain- and loss-of function approaches, we demonstrated a critical role of MUC1 in induction of drug resistance. Through stimulation of EGFR activation and nuclear translocation, MUC1 increased the expression of ATP-binding cassette transporter B1 (ABCB1). Remarkably, targeted suppression of EGFR or ABCB1 by both shRNAs and inhibitors effectively reversed chemoresistance. Moreover, co-administration of the inhibitors of MUC1-EGFR-ABCB1 with paclitaxel significantly blocked not only tumor growth but also relapse in xenograft mouse model. Our data collectively support a model in which MUC1 induces acquired chemotherapy resistance by upregulating ABCB1 in an EGFR-dependent manner, providing a novel molecular basis of using the EGFR inhibitor in MUC1-positive cancers to prevent chemotherapy resistance.

Analysis of origin and protein-protein interaction maps suggests distinct oncogenic role of nuclear EGFR during cancer evolution

Receptor tyrosine kinase EGFR usually is localized on plasma membrane to induce progression of many cancers including cancers in children (Bodey et al. In Vivo. 2005, 19:931-41), but it contains a nuclear localization signal (NLS) that mediates EGFR nuclear translocation (Lin et al. Nat Cell Biol. 2001, 3:802-8). Here we report that NLS of EGFR has its old evolutionary origin. Protein-protein interaction maps suggests that nEGFR pathways are different from membrane EGFR and EGF is not found in nEGFR network while androgen receptor (AR) is found, which suggests the evolution of prostate cancer, a well-known AR driven cancer, through changes in androgen- or EGF-dependence. Database analysis suggests that nEGFR correlates with the tumor grades especially in prostate cancer patients. Structural predication analysis suggests that NLS can compromise the differential protein binding to EGFR through stretch linkers with evolutionary mutation from N to V. In experiment, elevation of nEGFR but not membrane EGFR was found in castration resistant prostate cancer cells. Finally, systems analysis of NLS and transmembrane domain (TM) suggests that NLS has old origin while NLS neighboring domain of TM has been undergone accelerated evolution. Thus nEGFR has an old origin resembling the cancer evolution but TM may interfere with NLS driven signaling for natural selection of survival to evade NLS induced aggressive cancers. Our data suggest NLS is a dynamic inducer of EGFR oncogenesis during evolution for advanced cancers. Our model provides novel insights into the evolutionary role of NLS of oncogenic kinases in cancers.

Induction of PD-L1 expression by epidermal growth factor receptor-mediated signaling in esophageal squamous cell carcinoma

Purpose

The purpose of this study was to investigate the potential effect of activation of epidermal growth factor receptor (EGFR) signaling pathway on the expression of programmed death-ligand 1 (PD-L1) in esophageal squamous cell carcinoma (ESCC) cells with EGFR overexpression.

Methods

Flow cytometry and Western blot methods were used to assess PD-L1 expression on ESCC cells when EGFR signaling pathway was activated by epidermal growth factor (EGF) with or without EGFR-specific inhibitor AG-1478, and then EGFR signaling array was applied to analyze the potential signaling pathways involved.

Results

This study found that PD-L1 expression increased significantly in an EGFR-dependent manner by the activation of EGFR signaling and decreased sharply when EGFR signaling was blocked. The upregulated expression of PD-L1 was not associated with EGFR-STAT3 signaling pathway, but may be affected by EGFR–PI3K–AKT, EGFR–Ras–Raf–Erk, and EGR–PLC-γ signaling pathways.

Conclusion

The expression of PD-L1 can be regulated by EGFR signaling activation in ESCC, which indicates an important role for EGFR-mediated immune escape and potential molecular pathways for EGFR-targeted therapy and immunotherapy.

Long-term exposure to bisphenol A or benzo(a)pyrene alters the fate of human mammary epithelial stem cells in response to BMP2 and BMP4, by pre-activating BMP signaling

Bone morphogenetic protein 2 (BMP2) and BMP4 are key regulators of the fate and differentiation of human mammary epithelial stem cells (SCs), as well as of their niches, and are involved in breast cancer development. We established that MCF10A immature mammary epithelial cells reliably reproduce the BMP response that we previously identified in human primary epithelial SCs. In this model, we observed that BMP2 promotes luminal progenitor commitment and expansion, whereas BMP4 prevents lineage differentiation. Environmental pollutants are known to promote cancer development, possibly by providing cells with stem-like features and by modifying their niches. Bisphenols, in particular, were shown to increase the risk of developing breast cancer. Here, we demonstrate that chronic exposure to low doses of bisphenol A (BPA) or benzo(a)pyrene (B(a)P) alone has little effect on SCs properties of MCF10A cells. Conversely, we show that this exposure affects the response of immature epithelial cells to BMP2 and BMP4. Furthermore, the modifications triggered in MCF10A cells on exposure to pollutants appeared to be predominantly mediated by altering the expression and localization of type-1 receptors and by pre-activating BMP signaling, through the phosphorylation of small mothers against decapentaplegic 1/5/8 (SMAD1/5/8). By analyzing stem and progenitor properties, we reveal that BPA prevents the maintenance of SC features prompted by BMP4, whereas promoting cell differentiation towards a myoepithelial phenotype. Inversely, B(a)P prevents BMP2-mediated luminal progenitor commitment and expansion, leading to the retention of stem-like properties. Overall, our data indicate that BPA and B(a)P distinctly alter the fate and differentiation potential of mammary epithelial SCs by modulating BMP signaling.