Tumor-specific apoptosis caused by deletion of the ERBB3 pseudo-kinase in mouse intestinal epithelium

Neuregulin 1 (NRG1) and its receptors in the enteric nervous system and other parts of the gastrointestinal wall

Neuregulin 1 (NRG1) belonging to the transmembrane growth factors family is widespread in living organisms. It acts through ErbB family receptors and first of all takes part in embryogenesis, as well as in developmental, regenerative and adaptive processes occurring in various internal organs and systems. It is known that NRG1 and its receptors are present in various parts of the gastrointestinal (GI) tract. First of all NRG1 and ErbB receptors have been detected in the enteric nervous system (ENS) localized in the wall of the esophagus, stomach and intestine and regulating the majority of the GI tract functions, but also in the mucosal and muscular layers of the GI tract. The NRG1/ErbB pathway is involved in the development and differentiation of the ENS and regulation of the intestinal epithelium functions. Moreover, dysregulation of this pathway results in a wide range of gastrointestinal diseases. However, till now there are no summarizations of previous studies concerning distribution and functions of NRG1 and its receptors in the GI tract. The present review fills this gap.

ERBB3 targeting: A promising approach to overcoming cancer therapeutic resistance

Human epidermal growth factor receptor-3 (ERBB3) is a member of the ERBB receptor tyrosine kinases (RTKs) and is expressed in many malignancies. Along with other ERBB receptors, ERBB3 is associated with regulating normal cell proliferation, apoptosis, differentiation, and survival, and has received increased research attention for its involvement in cancer therapies. ERBB3 expression or co-expression levels have been investigated as predictive factors for cancer prognosis and drug sensitivity. Additionally, the association between the elevated expression of ERBB3 and treatment failure in cancer therapy further established ERBB3-targeting therapy as a crucial therapeutic approach. This review delves into the molecular mechanisms of ERBB3-driven resistance to targeted therapeutics against ERBB2 and EGFR and other signal transduction inhibitors, endocrine therapy, chemotherapy, and radiotherapy. Using preclinical and clinical evidence, we synthesise and explicate how various aspects of aberrant ERBB3 activities-such as compensatory activation, signal crosstalk interactions, dysregulation in the endocytic pathway, mutations, ligand-independent activation, intrinsic kinase activity, and homodimerisation-can lead to resistance development and/or treatment failures. Several ERBB3-directed monoclonal antibodies, bispecific antibodies, and the emerging antibody-drug conjugate demonstrate encouraging clinical outcomes for improving therapeutic efficacy and overcoming resistance, especially when combined with other anti-cancer approaches. More research efforts are needed to identify appropriate biomarkers tailored for ERBB3-targeted therapies.

Inhibiting HER3 Hyperphosphorylation in HER2-Overexpressing Breast Cancer through Multimodal Therapy with Branched Gold Nanoshells

Treatment failure in breast cancers overexpressing human epidermal growth factor receptor 2 (HER2) is associated mainly to the upregulation of human epidermal growth factor receptor 3 (HER3) oncoprotein linked to chemoresitence. Therefore, to increase patient survival, here a multimodal theranostic nanoplatform targeting both HER2 and HER3 is developed. This consists of doxorubicin-loaded branched gold nanoshells functionalized with the near-infrared (NIR) fluorescent dye indocyanine green, a small interfering RNA (siRNA) against HER3, and the HER2-specific antibody Transtuzumab, able to provide a combined therapeutic outcome (chemo- and photothermal activities, RNA silencing, and immune response). In vitro assays in HER2+ /HER3+ SKBR-3 breast cancer cells have shown an effective silencing of HER3 by the released siRNA and an inhibition of HER2 oncoproteins provided by Trastuzumab, along with a decrease of the serine/threonine protein kinase Akt (p-AKT) typically associated with cell survival and proliferation, which helps to overcome doxorubicin chemoresistance. Conversely, adding the NIR light therapy, an increment in p-AKT concentration is observed, although HER2/HER3 inhibitions are maintained for 72 h. Finally, in vivo studies in a tumor-bearing mice model display a significant progressively decrease of the tumor volume after nanoparticle administration and subsequent NIR light irradiation, confirming the potential efficacy of the hybrid nanocarrier.

Targeting Epidermal Growth Factor Receptor for Cancer Treatment: Abolishing Both Kinase-Dependent and Kinase-Independent Functions of the Receptor

Epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, is activated by ligand binding, overexpression, or mutation. It is well known for its tyrosine kinase-dependent oncogenic activities in a variety of human cancers. A large number of EGFR inhibitors have been developed for cancer treatment, including monoclonal antibodies, tyrosine kinase inhibitors, and a vaccine. The EGFR inhibitors are aimed at inhibiting the activation or the activity of EGFR tyrosine kinase. However, these agents have shown efficacy in only a few types of cancers. Drug resistance, both intrinsic and acquired, is common even in cancers where the inhibitors have shown efficacy. The drug resistance mechanism is complex and not fully known. The key vulnerability of cancer cells that are resistant to EGFR inhibitors has not been identified. Nevertheless, it has been increasingly recognized in recent years that EGFR also possesses kinase-independent oncogenic functions and that these noncanonical functions may play a crucial role in cancer resistance to EGFR inhibitors. In this review, both kinase-dependent and -independent activities of EGFR are discussed. Also discussed are the mechanisms of actions and therapeutic activities of clinically used EGFR inhibitors and sustained EGFR overexpression and EGFR interaction with other receptor tyrosine kinases to counter the EGFR inhibitors. Moreover, this review discusses emerging experimental therapeutics that have shown potential for overcoming the limitation of the current EGFR inhibitors in preclinical studies. The findings underscore the importance and feasibility of targeting both kinase-dependent and -independent functions of EGFR to enhance therapeutic efficacy and minimize drug resistance. SIGNIFICANCE STATEMENT: EGFR is a major oncogenic driver and therapeutic target, but cancer resistance to current EGFR inhibitors remains a significant unmet clinical problem. This article reviews the cancer biology of EGFR as well as the mechanisms of actions and the therapeutic efficacies of current and emerging EGFR inhibitors. The findings could potentially lead to development of more effective treatments for EGFR-positive cancers.

An unanticipated discourse of HB-EGF with VANGL2 signaling during embryo implantation

Implantation is the first direct encounter between the embryo and uterus during pregnancy, and Hbegf is the earliest known molecular signaling for embryo-uterine crosstalk during implantation. The downstream effectors of heparin-binding EGF (HB-EGF) in implantation remain elusive due to the complexity of EGF receptor family. This study shows that the formation of implantation chamber (crypt) triggered by HB-EGF is disrupted by uterine deletion of Vangl2, a key planar cell polarity component (PCP). We found that HB-EGF binds to ERBB2 and ERBB3 to recruit VANGL2 for tyrosine phosphorylation. Using in vivo models, we show that uterine VAGL2 tyrosine phosphorylation is suppressed in Erbb2/Erbb3 double conditional knockout mice. In this context, severe implantation defects in these mice lend support to the critical role of HB-EGF-ERBB2/3-VANGL2 in establishing a two-way dialogue between the blastocyst and uterus. In addition, the result addresses an outstanding question how VANGL2 is activated during implantation. Taken together, these observations reveal that HB-EGF regulates the implantation process by influencing uterine epithelial cell polarity comprising VANGL2.

Andrographis Reverses Gemcitabine Resistance through Regulation of ERBB3 and Calcium Signaling Pathway in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, primarily due to intrinsic or acquired resistance to chemotherapy, such as Gemcitabine (Gem). Naturally occurring botanicals, including Andrographis (Andro), can help enhance the anti-tumorigenic therapeutic efficacy of conventional chemotherapy through time-tested safety and cost-effectiveness. Accordingly, we hypothesized that Andro might reverse Gem resistance in PDAC. The critical regulatory pathways associated with Gem resistance in PDAC were identified by analyzing publicly available transcriptomic profiling and PDAC tissue specimens. A series of systematic in vitro experiments were performed using Gem-resistant (Gem-R) PDAC cells and patient-derived 3D-organoids to evaluate the Andro-mediated reversal of Gem resistance in PDAC. Transcriptomic profiling identified the calcium signaling pathway as a critical regulator of Gem-resistance (Fold enrichment: 2.8, p = 0.002). Within this pathway, high ERBB3 expression was significantly associated with poor prognosis in PDAC patients. The combination of Andro and Gem exhibited superior anti-cancer potential in Gem-R PDAC cells through potentiating cellular apoptosis. The combined treatment down-regulated ERBB3 and decreased intracellular calcium concentration in Gem-R PDAC cells. Finally, these findings were successfully interrogated in patient-derived 3D-organoids. In conclusion, we demonstrate novel evidence for Andro-mediated reversal of chemoresistance to Gem in PDAC cells through the regulation of ERBB3 and calcium signaling.

HER3 Alterations in Cancer and Potential Clinical Implications

In recent years, the third member of the HER family, kinase impaired HER3, has become a target of interest in cancer as there is accumulating evidence that HER3 plays a role in tumor growth and progression. This review focuses on HER3 activation in bladder, breast, colorectal, and lung cancer disease progression. HER3 mutations occur at a rate up to ~10% of tumors dependent on the tumor type. With patient tumors routinely sequenced for gene alterations in recent years, we have focused on HER3 mutations in bladder, breast, colon, and lung cancers particularly in response to targeted therapies and the potential to become a resistance mechanism. There are currently several HER3 targeting drugs in the pipeline, possibly improving outcomes for cancer patients with tumors containing HER3 activation and/or alterations.

The Yin and Yang of ERBB4: Tumor Suppressor and Oncoprotein

ERBB4 (HER4) is a member of the ERBB family of receptor tyrosine kinases, a family that includes the epidermal growth factor receptor (EGFR/ERBB1/HER1), ERBB2 (Neu/HER2), and ERBB3 (HER3). EGFR and ERBB2 are oncoproteins and validated targets for therapeutic intervention in a variety of solid tumors. In contrast, the role that ERBB4 plays in human malignancies is ambiguous. Thus, here we review the literature regarding ERBB4 function in human malignancies. We review the mechanisms of ERBB4 signaling with an emphasis on mechanisms of signaling specificity. In the context of this signaling specificity, we discuss the hypothesis that ERBB4 appears to function as a tumor suppressor protein and as an oncoprotein. Next, we review the literature that describes the role of ERBB4 in tumors of the bladder, liver, prostate, brain, colon, stomach, lung, bone, ovary, thyroid, hematopoietic tissues, pancreas, breast, skin, head, and neck. Whenever possible, we discuss the possibility that ERBB4 mutants function as biomarkers in these tumors. Finally, we discuss the potential roles of ERBB4 mutants in the staging of human tumors and how ERBB4 function may dictate the treatment of human tumors. SIGNIFICANCE STATEMENT: This articles reviews ERBB4 function in the context of the mechanistic model that ERBB4 homodimers function as tumor suppressors, whereas ERBB4-EGFR or ERBB4-ERBB2 heterodimers act as oncogenes. Thus, this review serves as a mechanistic framework for clinicians and scientists to consider the role of ERBB4 and ERBB4 mutants in staging and treating human tumors.

Epithelial-specific ERBB3 deletion results in a genetic background-dependent increase in intestinal and colon polyps that is mediated by EGFR

ERBB3 has gained attention as a potential therapeutic target to treat colorectal and other types of cancers. To confirm a previous study showing intestinal polyps are dependent upon ERBB3, we generated an intestinal epithelia-specific ERBB3 deletion in C57BL/6-ApcMin/+ mice. Contrary to the previous report showing a significant reduction in intestinal polyps with ablation of ERBB3 on a B6;129 mixed genetic background, we observed a significant increase in polyp number with ablation of ERBB3 on C57BL/6J compared to control littermates. We confirmed the genetic background dependency of ERBB3 by also analyzing polyp development on B6129 hybrid and B6;129 advanced intercross mixed genetic backgrounds, which showed that ERBB3 deficiency only reduced polyp number on the mixed background as previously reported. Increased polyp number with ablation of ERBB3 was also observed in C57BL/6J mice treated with azoxymethane showing the effect is model independent. Polyps forming in absence of ERBB3 were generally smaller than those forming in control mice, albeit the effect was greatest in genetic backgrounds with reduced polyp numbers. The mechanism for differential polyp number in the absence of ERBB3 was through altered proliferation. Backgrounds with increased polyp number with loss of ERBB3 showed an increase in cell proliferation even in non-tumor epithelia, while backgrounds showing reduced polyp number with loss of ERBB3 showed reduced cellular proliferation. Increase polyp number caused by loss of ERBB3 was mediated by increased epidermal growth factor receptor (EGFR) expression, which was confirmed by deletion of Egfr. Taken together, this study raises substantial implications on the use of ERBB3 inhibitors against colorectal cancer. The prediction is that some patients may have increased progression with ERBB3 inhibitor therapy, which is consistent with observations reported for ERBB3 inhibitor clinical trials.

ERBB3-dependent AKT and ERK pathways are essential for atrioventricular cushion development in mouse embryos

ERBB family members and their ligands play an essential role in embryonic heart development and adult heart physiology. Among them, ERBB3 is a binding partner of ERBB2; the ERBB2/3 complex mediates downstream signaling for cell proliferation. ERBB3 has seven consensus binding sites to the p85 regulatory subunit of PI3K, which activates the downstream AKT pathway, leading to the proliferation of various cells. This study generated a human ERBB3 knock-in mouse expressing a mutant ERBB3 whose seven YXXM p85 binding sites were replaced with YXXA. Erbb3 knock-in embryos exhibited lethality between E12.5 to E13.5, and showed a decrease in mesenchymal cell numbers and density in AV cushions. We determined that the proliferation of mesenchymal cells in the atrioventricular (AV) cushion in Erbb3 knock-in mutant embryos was temporarily reduced due to the decrease of AKT and ERK1/2 phosphorylation. Overall, our results suggest that AKT/ERK activation by the ERBB3-dependent PI3K signaling is crucial for AV cushion morphogenesis during embryonic heart development.

Source and Impact of the EGF Family of Ligands on Intestinal Stem Cells

Epidermal Growth Factor (EGF) has long been known for its role in promoting proliferation of intestinal epithelial cells. EGF is produced by epithelial niche cells at the base of crypts in vivo and is routinely added to the culture medium to support the growth of intestinal organoids ex vivo. The recent identification of diverse stromal cell populations that reside underneath intestinal crypts has enabled the characterization of key growth factor cues supplied by these cells. The nature of these signals and how they are delivered to drive intestinal epithelial development, daily homeostasis and tissue regeneration following injury are being investigated. It is clear that aside from EGF, other ligands of the family, including Neuregulin 1 (NRG1), have distinct roles in supporting the function of intestinal stem cells through the ErbB pathway.

Taking a Step Back: Insights into the Mechanisms Regulating Gut Epithelial Dedifferentiation

Despite the environmental constraints imposed upon the intestinal epithelium, this tissue must perform essential functions such as nutrient absorption and hormonal regulation, while also acting as a critical barrier to the outside world. These functions depend on a variety of specialized cell types that are constantly renewed by a rapidly proliferating population of intestinal stem cells (ISCs) residing at the base of the crypts of Lieberkühn. The niche components and signals regulating crypt morphogenesis and maintenance of homeostatic ISCs have been intensely studied over the last decades. Increasingly, however, researchers are turning their attention to unraveling the mechanisms driving gut epithelial regeneration due to physical damage or infection. It is now well established that injury to the gut barrier triggers major cell fate changes, demonstrating the highly plastic nature of the gut epithelium. In particular, lineage tracing and transcriptional profiling experiments have uncovered several injury-induced stem-cell populations and molecular markers of the regenerative state. Despite the progress achieved in recent years, several questions remain unresolved, particularly regarding the mechanisms driving dedifferentiation of the gut epithelium. In this review, we summarize the latest studies, primarily from murine models, that define the regenerative processes governing the gut epithelium and discuss areas that will require more in-depth investigation.

HER2 and APC Mutations Promote Altered Crypt-Villus Morphology and Marked Hyperplasia in the Intestinal Epithelium

BACKGROUND AND AIMS

The Cancer Genome Atlas (TCGA) project has identified HER2 mutations or amplification in 7% of colon cancers. In addition to HER2 mutations, colon cancer patients also possess co-occurring mutations in genes such as APC. Here, we investigated the role of HER2 and APC mutations on the crypt-villus architecture of the intestinal epithelium, localization of secretory cells, and expression of intestinal stem cell markers.

METHODS

We generated a HER2 transgenic mouse (HER2V777L Tg) possessing an activating mutation commonly found in colorectal cancer patients, HER2V777L, using transcription activator-like effector nucleases-based gene editing technology. We expressed the HER2V777L transgene in mouse small intestine and colon using Lgr5-Cre and Villin-Cre recombinases. In addition, we analyzed Lgr5-Cre; APCmin; HER2V777L Tg mice by morphologic and gene expression assays on intestinal sections and organoids derived from the epithelium.

RESULTS

HER2V777L expression resulted in hypertrophic crypt formation with expanded zones of proliferation. Proximal intestinal villi showed increased abundance of multiple differentiated lineages including extensive intermediate cell differentiation, as evidenced by MUC2/MMP7 co-immunofluorescence and transmission electron microscopy. HER2V777L expression in the context of APC loss resulted in further enhancement and expansion of the proliferative crypt compartment.

CONCLUSIONS

We established an epithelial intrinsic role for HER2V777L on enhanced cellular proliferation. Additionally, we determined that HER2 and APC mutations, when combined, promote enhanced proliferation of intestinal crypts.

Embryonic lethality and defective mammary gland development of activator-function impaired conditional knock-in Erbb3 V943R mice

ERBB3 is a pseudokinase domain-containing member of the ERBB family of receptor tyrosine kinases (RTKs). Following ligand binding, ERBB receptors homo- or hetero-dimerize, leading to a head-to-tail arrangement of the intracellular kinase domains, where the "receiver" kinase domain of one ERBB is activated by the "activator" domain of the other ERBB in the dimer. In ERBB3, a conserved valine at codon 943 (V943) in the kinase C-terminal domain has been shown to be important for its function as an "activator" kinase in vitro. Here we report a knock-in mouse model where we have modified the endogenous Erbb3 allele to allow for tissue-specific conditional expression of Erbb3 ^V943R (Erbb3 ^CKI-V943R ). Additionally, we generated an Erbb3 ^D850N (Erbb3 ^CKI-D850N ) conditional knock-in mouse model where the conserved aspartate in the DFG motif of the pseudokinase domain was mutated to abolish any potential residual kinase activity. While Erbb3 ^D850N/D850N animals developed normally, homozygous Erbb3 ^V943R/V943R expression during development resulted in embryonic lethality. Further, tissue specific expression of Erbb3 ^V943R/V943R in the mammary gland epithelium following its activation using MMTV-Cre resulted in delayed elongation of the ductal network during puberty. Single-cell RNA-seq analysis of Erbb3 ^V943R/V943R mammary glands showed a reduction in a specific subset of fibrinogen-producing luminal epithelial cells.

New insights into ErbB3 function and therapeutic targeting in cancer

INTRODUCTION

The importance of ErbB3 receptor tyrosine kinase in cancer progression, primary and acquired drug resistance, has become steadily evident since its discovery in 1989. ErbB3 overexpression in various solid organ malignancies is associated with shorter survival of patients. However, initial strategies to therapeutically target ErbB3 have not been rewarding.

AREAS COVERED

Here, we provide an overview of ErbB3 biology in carcinogenesis. We outline the role of ErbB3 as a critical pathway for resistance to other anti-cancer drugs. We focus on emerging clinical data, which will steer the potential future development of ErbB3 directed therapies.

EXPERT OPINION

Initial approaches to ErbB3 targeting have been challenging. However, the lack of success of anti-ErbB3 therapies in ongoing clinical trials may relate more to the complex biology of the receptor and challenges with the biomarkers used to date. Furthermore, it seems certain that the expression of the receptor per se is necessary but not sufficient for the response to ErbB3 therapies. Emerging data suggest that more sophisticated biomarkers are needed. Nonetheless, it is also likely that ErbB3 therapies may have the most efficacy in combination therapy, and their favorable toxicity profile makes this feasible.

Mesenchymal Niche-Derived Neuregulin-1 Drives Intestinal Stem Cell Proliferation and Regeneration of Damaged Epithelium

Epidermal growth factor (EGF) maintains intestinal stem cell (ISC) proliferation and is a key component of organoid growth media yet is dispensable for intestinal homeostasis, suggesting roles for multiple EGF family ligands in ISC function. Here, we identified neuregulin 1 (NRG1) as a key EGF family ligand that drives tissue repair following injury. NRG1, but not EGF, is upregulated upon damage and is expressed in mesenchymal stromal cells, macrophages, and Paneth cells. NRG1 deletion reduces proliferation in intestinal crypts and compromises regeneration capacity. NRG1 robustly stimulates proliferation in crypts and induces budding in organoids, in part through elevated and sustained activation of mitogen-activated protein kinase (MAPK) and AKT. Consistently, NRG1 treatment induces a proliferative gene signature and promotes organoid formation from progenitor cells and enhances regeneration following injury. These data suggest mesenchymal-derived NRG1 is a potent mediator of tissue regeneration and may inform the development of therapies for enhancing intestinal repair after injury.

STAT3-mediated MLST8 gene expression regulates cap-dependent translation in cancer cells

Signal transducer and activator of transcription 3 (STAT3) regulates cell growth, cell survival, angiogenesis, metastasis of cancer cells, and cancer immune evasion by regulating gene expression as a transcription factor. However, the effect of STAT3 on translation is almost unknown. We demonstrated that STAT3 acts as a trans‐acting factor for MLST8 gene expression and the protein level of mLST8, a core component of mechanistic target of rapamycin complex 1 and 2 (mTORC1/2), positively regulates the mTORC1/2 downstream pathways. Suppression of STAT3 by siRNA attenuated 4E‐BP1 phosphorylation, cap‐dependent translation, and cell proliferation in a variety of cancer cells. In HCT116 cells, STAT3 knockdown‐induced decreases in 4E‐BP1 and AKT phosphorylation levels were further attenuated by MLST8 knockdown or recovered by mLST8 overexpression. STAT3 knockdown‐induced G2/M phase arrest was partially restored by co‐knockdown of 4EBP1, and the attenuation of cell proliferation was enhanced by the expression of an mTORC1‐mediated phosphorylation‐defective mutant of 4E‐BP1. ChIP and promoter mapping using a luciferase reporter assay showed that the −951 to −894 bp of MLST8 promoter seems to include STAT3‐binding site. Overall, these results suggest that STAT3‐driven MLST8 gene expression regulates cap‐dependent translation through 4E‐BP1 phosphorylation in cancer cells.

HER family in cancer progression: From discovery to 2020 and beyond

The human epidermal growth factor receptor (HER) family of receptor tyrosine kinases (RTKs) are among the first layer of molecules that receive, interpret, and transduce signals leading to distinct cancer cell phenotypes. Since the discovery of the tooth-lid factor-later characterized as the epidermal growth factor (EGF)-and its high-affinity binding EGF receptor, HER kinases have emerged as one of the commonly upregulated or hyperactivated or mutated kinases in epithelial tumors, thus allowing HER1-3 family members to regulate several hallmarks of cancer development and progression. Each member of the HER family exhibits shared and unique structural features to engage multiple receptor activation modes, leading to a range of overlapping and distinct phenotypes. EGFR, the founding HER family member, provided the roadmap for the development of the cell surface RTK-directed targeted cancer therapy by serving as a prototype/precursor for the currently used HER-directed cancer drugs. We herein provide a brief account of the discoveries, defining moments, and historical context of the HER family and guidepost advances in basic, translational, and clinical research that solidified a prominent position of the HER family in cancer research and treatment. We also discuss the significance of HER3 pseudokinase in cancer biology; its unique structural features that drive transregulation among HER1-3, leading to a superior proximal signaling response; and potential role of HER3 as a shared effector of acquired therapeutic resistance against diverse oncology drugs. Finally, we also narrate some of the current drawbacks of HER-directed therapies and provide insights into postulated advances in HER biology with extensive implications of these therapies in cancer research and treatment.

Colorectal cancer (CRC) as a multifactorial disease and its causal correlations with multiple signaling pathways

Colorectal cancer (CRC) is the third most common malignancy and one of the leading causes of cancer-related death among men worldwide. CRC is a multifactor digestive pathology, which is a huge problem faced not only by clinicians but also by researchers. Importantly, a unique feature of CRC is the dysregulation of molecular signaling pathways. To date, a series of reviews have indicated that different signaling pathways are disordered and have potential as therapeutic targets in CRC. Nevertheless, an overview of the function and interaction of multiple signaling pathways in CRC is needed. Therefore, we summarized the pathways, biological functions and important interactions involved in CRC. First, we investigated the involvement of signaling pathways, including Wnt, PI3K/Akt, Hedgehog, ErbB, RHOA, Notch, BMP, Hippo, AMPK, NF-κB, MAPK and JNK. Subsequently, we discussed the biological function of these pathways in pathophysiological aspects of CRC, such as proliferation, apoptosis and metastasis. Finally, we summarized important interactions among these pathways in CRC. We believe that the interaction of these pathways could provide new strategies for the treatment of CRC.

Kinase activity of ERBB3 contributes to intestinal organoids growth and intestinal tumorigenesis

As a member of the epidermal growth factor receptor (EGFR) family, ERBB3 plays an essential role in development and disease independent of inherently inactive kinase domain. Recently, ERBB3 has been found to bind to ATP and has catalytic activity in vitro. However, the biological function of ERBB3 kinase activity remains elusive in vivo. Here we have identified the physiological function of inactivated ERBB3 kinase activity by creating Erbb3‐K740M knockin mice in which ATP cannot bind to ERBB3. Unlike Erbb3 knockout mice, kinase‐inactive Erbb3^K740M homozygous mice were born in Mendelian ratios and showed normal development. After dextran sulfate sodium‐induced colitis, the kinase‐inactive Erbb3 mutant mice showed normal recovery. However, the outgrowth of ileal organoids by neuregulin‐1 treatment was more attenuated in Erbb3 mutant mice than in WT mice. Moreover, in combination with the Apc^Min mouse, the proportion of polyps less than 1 mm in diameter in mutant mice was higher than in control mice and an increase in the number of apoptotic cells was observed in polyps from mutant mice compared with polyps from control mice. Taken together, the ERBB3 kinase activity contributes to the outgrowth of ileal organoids and intestinal tumorigenesis, and the development of ERBB3 kinase inhibitors, including epidermal growth factor receptor family members, can be a potential way to target colorectal cancer.

Identification of differentially expressed circRNAs and a novel hsa_circ_0000144 that promote tumor growth in gastric cancer

Background

Circular RNAs (circRNAs) are involved in regulating tumor pathogenesis. The mechanism of circRNAs in gastric cancer (GC) is still unknown. Our study aimed to identify differentially expressed circRNAs and assess a novel circRNA (hsa_circ_0000144) in the proliferation, migration, and invasion in GC.

Methods

Gene ontology (GO) enrichment and analyses of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, pathway network, and the ceRNA regulatory network of hsa_circ_0000144 targeting miRNAs and mRNAs were performed with the help of bioinformatics using R language and Perl software. hsa_circ_0000144 expression and circRNA knockdown in GC cell lines were detected using quantitative PCR (qPCR) in vitro. Cell proliferation, migration, and invasion after circRNA knockdown were measured using the cell counting kit-8 assay and Transwell assay.

Results

The circRNA expression profile GSE78092 downloaded from the Gene Expression Omnibus database included three GC patients and three normal tissues. Thirty-two differentially expressed circRNAs comprised six upregulated circRNAs and 26 downregulated circRNAs. In particular, the ErbB signaling pathway, neurotrophin signaling pathway, cellular senescence, and pathways in bladder cancer and GC played the most important roles in the pathway network. The expression of hsa_circ_0000144 was upregulated in GC cell lines. Hsa_circ_0000144 knockdown suppressed tumor growth in vitro.

Conclusions

Hsa_circ_0000144 promotes GC cell proliferation, migration, and invasion, and the ceRNA regulatory network of hsa_circ_0000144 targeting miRNAs and mRNAs might be biomarkers for GC diagnosis and targeted therapy.

ITCH-dependent proteasomal degradation of c-FLIP induced by the anti-HER3 antibody 9F7-F11 promotes DR5/caspase 8-mediated apoptosis of tumor cells

Background

HER3/ErbB3 receptor deletion or blockade leads to tumor cell apoptosis, whereas its overexpression confers anti-cancer drug resistance through upregulation of protective mechanisms against apoptosis. We produced the anti-HER3 antibody 9F7-F11 that promotes HER3 ubiquitination and degradation via JNK1/2-dependent activation of the E3 ubiquitin ligase ITCH, and that induces apoptosis of cancer cells. Cellular FLICE-like inhibitory protein (c-FLIP) is a key regulator of apoptotic pathways. Here, we wanted to determine the mechanisms underlying the pro-apoptotic effect of 9F7-F11.

Methods

Anti-HER3 antibody-induced apoptosis was assessed by western blot, and by flow cytometry measurement of Annexin V/7-AAD-labelled tumor cells (BxPC3, MDA-MB-468 and DU145 cell lines). c-FLIP/ITCH interaction and subsequent degradation/ubiquitination were investigated by co-immunoprecipitation of ITCH-silenced vs scramble control cells. The relationship between ITCH-mediated c-FLIP degradation and antibody-induced apoptosis was examined by western blot and flow cytometry of tumor cells, after ITCH RNA interference or by pre-treatment with ITCH chemical inhibitor chlorimipramine (CI).

Results

Following incubation with 9F7-F11, cancer cell apoptosis occurs through activation of caspase-8, − 9 and − 3 and the subsequent cleavage of poly (ADP-ribose) polymerase (PARP). Moreover we showed that ubiquitination and proteasomal degradation of the anti-apoptotic protein c-FLIP was mediated by USP8-regulated ITCH recruitment. This effect was abrogated by ITCH- and USP8-specific RNA interference (siRNA), or by the ITCH chemical inhibitor CI. Specifically, ITCH silencing or CI blocked 9F7-F11-induced caspase-8-mediated apoptosis of tumor cells, and restored c-FLIP expression. ITCH-silencing or CI concomitantly abrogated HER3-specific antibody-induced apoptosis of Annexin V/7-AAD-labelled BxPC3 cells. 9F7-F11 favored the extrinsic apoptosis pathway by inducing TRAIL-R2/DR5 upregulation and TRAIL expression that promoted the formation of death-inducing signaling complex (DISC), leading to caspase-8-mediated apoptosis. Incubation with 9F7-F11 also induced BID cleavage, BAX upregulation and BIM expression, which initiated the caspase-9/3-mediated mitochondrial death pathway. The anti-HER3 antibody pro-apoptotic effect occurred concomitantly with downregulation of the pro-survival proteins c-IAP2 and XIAP.

Conclusions

The allosteric non-neuregulin competing modulator 9F7-F11, sensitizes tumor cells to DR5/caspase-8-mediated apoptosis through ITCH-dependent downregulation of c-FLIP.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0413-8) contains supplementary material, which is available to authorized users.

Dual gene deficient models of ApcMin/+ mouse in assessing molecular mechanisms of intestinal carcinogenesis

The Apc^Min/+ mouse, carrying an inactivated allele of the adenomatous polyposis coli (Apc) gene, is a widely used animal model of human colorectal tumorigenesis. While crossed with other gene knockout or knock-in mice, these mice possess advantages in investigation of human intestinal tumorigenesis. Intestinal tumor pathogenesis involves multiple gene alterations; thus, various double gene deficiency models could provide novel insights into molecular mechanisms of tumor biology, as well as gene-gene interactions involved in intestinal tumor development and assessment of novel strategies for preventing and treating intestinal cancer. This review discusses approximately 100 double gene deficient mice and their associated intestinal tumor development and progression phenotypes. The dual gene knockouts based on the Apc mutation background consist of inflammation and immune-related, cell cycle-related, Wnt/β-catenin signaling-related, tumor growth factor (TGF)-signaling-related, drug metabolism-related, and transcription factor genes, as well as some oncogenes and tumor suppressors. Future studies should focus on conditional or inducible dual or multiple mouse gene knockout models to investigate the molecular mechanisms underlying intestinal tumor development, as well as potential drug targets.

The role of ErbB3 binding protein 1 in cancer: Friend or foe?

ErbB3, a member of the epidermal growth factor receptor family, reportedly plays an essential role in the regulation of cancer progression and therapeutic resistance. Numerous studies have indicated that ErbB3 binding protein 1 (Ebp1), a binding partner for ErbB3, plays an important regulatory role in the expression and function of ErbB3, but there is no agreement as to whether Ebp1 also has an ErbB3-independent function in cancer and how it might contribute to tumorigenesis. In this review, we will discuss the different functions of the two Ebp1 isoforms, p48 and p42, that may be responsible for the potentially dual role of Ebp1 in cancer growth.

Imaging EGFR and HER3 through 89Zr-labeled MEHD7945A (Duligotuzumab)

Tumor resistance to treatment paved the way toward the development of single agent drugs that target multiple molecular signatures amplified within the malignancy. The discovered crosstalk between EGFR and HER3 as well as the role of HER3 in mediating EGFR resistance made these two receptor tyrosine kinases attractive targets. MEHD7945A or duligotuzumab is a single immunotherapy agent that dually targets both molecular signatures. In this study, a positron emission tomography (PET) companion diagnostic to MEHD7945A is reported and evaluated in pancreatic cancer. Tumor accretion and whole body pharmacokinetics of 89Zr-MEHD7945A were established. Specificity of the probe for EGFR and/or HER3 was further examined.

The role of the EGFR signaling pathway in stem cell differentiation during planarian regeneration and homeostasis

Cell signaling is essential for cells to adequately respond to their environment. One of the most evolutionarily conserved signaling pathways is that of the epidermal growth factor receptor (EGFR). Transmembrane receptors with intracellular tyrosine kinase activity are activated by the binding of their corresponding ligands. This in turn activates a wide variety of intracellular cascades and induces the up- or downregulation of target genes, leading to a specific cellular response. Freshwater planarians are an excellent model in which to study the role of cell signaling in the context of stem-cell based regeneration. Owing to the presence of a population of pluripotent stem cells called neoblasts, these animals can regenerate the entire organism from a tiny piece of the body. Here, we review the current state of knowledge of the planarian EGFR pathway. We describe the main components of the pathway and their functions in other animals, and focus in particular on receptors and ligands identified in the planarian Schmidtea mediterranea. Moreover, we summarize current data on the function of some of these components during planarian regeneration and homeostasis. We hypothesize that the EGFR pathway may act as a key regulator of the terminal differentiation of distinct populations of lineage-committed progenitors.

Oncogenic Ras triggers hyperproliferation and impairs polarized colonic morphogenesis by autocrine ErbB3 signaling

Here we study the effects of inducible oncogenic K-Ras (G12V) expression on the polarized morphogenesis of colonic epithelial cells. We provide evidence that the autocrine production of heregulins, ligands for the ErbB3 receptor tyrosine kinase, is responsible for the hyperproliferation and aberrant 3D morphogenesis upon oncogenic K-Ras expression. This is in line with results obtained in primary intestinal organoid cultures, in which exogenous heregulin is shown to interfere with normal tissue architecture. Importantly, ErbB3 inhibition and heregulin gene silencing rescued K-RasG12V-induced features of cell transformation. Together with the increased ErbB3 positivity detected in human high-grade primary colorectal cancers, our findings provide support for an autocrine signaling loop engaged by oncogenic K-Ras involving ErbB3 that contributes to the dedifferentiation of the intestinal epithelium during tumor initiation and progression.

Anti-Trop2 blockade enhances the therapeutic efficacy of ErbB3 inhibition in head and neck squamous cell carcinoma

ErbB3 has been widely implicated in treatment resistance, but its role as a primary treatment target is less clear. Canonically ErbB3 requires EGFR or ErbB2 for activation, whereas these two established treatment targets are thought to signal independently of ErbB3. In this study, we show that ErbB3 is essential for tumor growth of treatment-naive HNSCC patient-derived xenografts. This ErbB3 dependency occurs via ErbB3-mediated control of EGFR activation and HIF1α stabilization, which require ErbB3 and its ligand neuregulin-1. Here, we show that ErbB3 antibody treatment selects for a population of ErbB3-persister cells that express high levels of the transmembrane protein Trop2 that we previously identified as an inhibitor of ErbB3. Co-treatment with anti-ErbB3 and anti-Trop2 antibodies is synergistic and produces a greater anti-tumor response than either antibody alone. Collectively, these data both compel a revision of ErbB-family signaling and delineate a strategy for its effective inhibition in HNSCC.

MET Signaling Mediates Intestinal Crypt-Villus Development, Regeneration, and Adenoma Formation and Is Promoted by Stem Cell CD44 Isoforms

BACKGROUND & AIMS

Resistance of metastatic human colorectal cancer cells to drugs that block epidermal growth factor (EGF) receptor signaling could be caused by aberrant activity of other receptor tyrosine kinases, activating overlapping signaling pathways. One of these receptor tyrosine kinases could be MET, the receptor for hepatocyte growth factor (HGF). We investigated how MET signaling, and its interaction with CD44 (a putative MET coreceptor regulated by Wnt signaling and highly expressed by intestinal stem cells [ISCs] and adenomas) affects intestinal homeostasis, regeneration, and adenoma formation in mini-gut organoids and mice.

METHODS

We established organoid cultures from ISCs stimulated with HGF or EGF and assessed intestinal differentiation by immunohistochemistry. Mice with total epithelial disruption of MET (Ah^Cre/Met^fl/fl/LacZ) or ISC-specific disruption of MET (Lgr5^Creert2/Met^fl/fl/LacZ) and control mice (Ah^Cre/Met^+/+/LacZ, Lgr5^Creert2/Met^+/+/LacZ) were exposed to 10 Gy total body irradiation; intestinal tissues were collected, and homeostasis and regeneration were assessed by immunohistochemistry. We investigated adenoma organoid expansion stimulated by HGF or EGF using adenomas derived from Lgr5^Creert2/Met^fl/fl/Apc^fl/fl and Lgr5^Creert2/Met^+/+/Apc^fl/fl mice. The same mice were evaluated for adenoma prevalence and size. We also quantified adenomas in Ah^Cre/Met^fl/fl/Apc^fl/+ mice compared with Ah^Cre/Met^+/+/Apc^fl/+ control mice. We studied expansion of organoids generated from crypts and adenomas, stimulated by HGF or EGF, that were derived from mice expressing different CD44 splice variants (Cd44^+/+, Cd44^-/-, Cd44^s/s, or Cd44^v4-10/v4-10 mice).

RESULTS

Crypts incubated with EGF or HGF expanded into self-organizing mini-guts with similar levels of efficacy and contained all differentiated cell lineages. MET-deficient mice did not have defects in intestinal homeostasis. Total body irradiation reduced numbers of proliferating crypts in Ah^Cre/Met^fl/fl/LacZ mice. Lgr5^Creert2/Met^fl/fl/LacZ mice had impaired regeneration of MET-deficient ISCs. Adenoma organoids stimulated with EGF or HGF expanded to almost twice the size of nonstimulated organoids. MET-deficient adenoma organoids did not respond to HGF stimulation, but did respond to EGF. ISC-specific disruption of Met (Lgr5^Creert2/Met^fl/fl/Apc^fl/fl mice) caused a twofold increase in apoptosis in microadenomas, resulting in an approximately 50% reduction of microadenoma numbers and significantly reduced average adenoma size. Total epithelial disruption of Met (Ah^Cre/Met^fl/fl/Apc^fl/+ mice) resulted in an approximate 50% reduction in (micro)adenoma numbers. Intestinal crypts from Cd44^-/- mice did not expand to the same extent as crypts from Cd44^+/+ mice on stimulation with HGF, but had the same response to EGF. The negative effect on HGF-mediated growth was overcome by expression of CD44v4-10, but not by CD44s. Similarly, HGF-mediated expansion of adenoma organoids required CD44v4-10.

CONCLUSIONS

In studies of intestinal organoid cultures and mice with inducible deletion of MET, we found HGF receptor signaling to regulate intestinal homeostasis and regeneration, as well as adenoma formation. These activities of MET are promoted by the stem cell CD44 isoform CD44v4-10. Our findings provide rationale for targeting signaling via MET and CD44 during anti-EGF receptor therapy of patients with colorectal cancer or in patients resistant to EGF receptor inhibitors.

Disrupted hippocampal neuregulin-1/ErbB3 signaling and dentate gyrus granule cell alterations in suicide

Neuregulin-1 (NRG1) and ErbB receptors have been associated with psychopathology, and NRG1-ErbB3 signaling has been shown to increase hippocampal neurogenesis and induce antidepressant-like effects. In this study, we aimed to determine whether deficits in NRG1 or ErbBs might be present in the hippocampus of suicide completers. In well-characterized postmortem hippocampal samples from suicides and matched sudden-death controls, we assessed gene expression and methylation using qRT-PCR and EpiTYPER, respectively. Moreover, in hippocampal tissues stained with cresyl violet, stereology was used to quantify numbers of granule cells and of glia. Granule cell body size was examined with a nucleator probe, and granule cell layer volume with a Cavalieri probe. Unmedicated suicides showed sharply decreased hippocampal ErbB3 expression and decreased numbers of ErbB3-expressing granule cell neurons in the anterior dentate gyrus; a phenomenon seemingly reversed by antidepressant treatment. Furthermore, we found ErbB3 expression to be significantly decreased in the dentate gyrus of adult mice exposed to chronic social defeat stress. Taken together, these results reveal novel suicidal endophenotypes in the hippocampus, as well as a putative etiological mechanism underlying suicidality, and suggest that antidepressant or NRG1 treatment may reverse a potential deficit in anterior dentate gyrus granule cell neurons in individuals at risk of dying by suicide.

The ErbB3 receptor tyrosine kinase negatively regulates Paneth cells by PI3K-dependent suppression of Atoh1

Paneth cells (PCs), a secretory population located at the base of the intestinal crypt, support the intestinal stem cells (ISC) with growth factors and participate in innate immunity by releasing antimicrobial peptides, including lysozyme and defensins. PC dysfunction is associated with disorders such as Crohn's disease and necrotizing enterocolitis, but the specific pathways regulating PC development and function are not fully understood. Here we tested the role of the neuregulin receptor ErbB3 in control of PC differentiation and the ISC niche. Intestinal epithelial ErbB3 knockout caused precocious appearance of PCs as early as postnatal day 7, and substantially increased the number of mature PCs in adult mouse ileum. ErbB3 loss had no effect on other secretory lineages, but increased expression of the ISC marker Lgr5. ErbB3-null intestines had elevated levels of the Atoh1 transcription factor, which is required for secretory fate determination, while Atoh1⁺ cells had reduced ErbB3, suggesting reciprocal negative regulation. ErbB3-null intestinal progenitor cells showed reduced activation of the PI3K-Akt and ERK MAPK pathways. Inhibiting these pathways in HT29 cells increased levels of ATOH1 and the PC marker LYZ. Conversely, ErbB3 activation suppressed LYZ and ATOH1 in a PI3K-dependent manner. Expansion of the PC compartment in ErbB3-null intestines was accompanied with elevated ER stress and inflammation markers, raising the possibility that negative regulation of PCs by ErbB3 is necessary to maintain homeostasis. Taken together, our data suggest that ErbB3 restricts PC numbers through PI3K-mediated suppression of Atoh1 levels leading to inhibition of PC differentiation, with important implications for regulation of the ISC niche.

ErbB4 signaling stimulates pro-inflammatory macrophage apoptosis and limits colonic inflammation

Efficient clearance of pro-inflammatory macrophages from tissues after resolution of a challenge is critical to prevent prolonged inflammation. Defects in clearance can contribute to conditions such as inflammatory bowel disease, and thus may be therapeutically targetable. However, the signaling pathways that induce termination of pro-inflammatory macrophages are incompletely defined. We tested whether the ErbB4 receptor tyrosine kinase, previously not known to have role in macrophage biology, is involved in this process. In vitro, pro-inflammatory activation of cultured murine and human macrophages induced ErbB4 expression; in contrast, other ErbB family members were not induced in pro-inflammatory cells, and other innate immune lineages (dendritic cells, neutrophils) did not express detectable ErbB4 levels. Treatment of activated pro-inflammatory macrophages with the ErbB4 ligand neuregulin-4 (NRG4) induced apoptosis. ErbB4 localized to the mitochondria in these cells. Apoptosis was accompanied by loss of mitochondrial membrane potential, and was dependent upon the proteases that generate the cleaved ErbB4 intracellular domain fragment, suggesting a requirement for this fragment and mitochondrial pathway apoptosis. In vivo, ErbB4 was highly expressed on pro-inflammatory macrophages but not neutrophils during experimental DSS colitis in C57Bl/6 mice. Active inflammation in this model suppressed NRG4 expression, which may allow for macrophage persistence and ongoing inflammation. Consistent with this notion, NRG4 levels rebounded during the recovery phase, and administration of exogenous NRG4 during colitis reduced colonic macrophage numbers and ameliorated inflammation. These data define a novel role for ErbB4 in macrophage apoptosis, and outline a mechanism of feedback inhibition that may promote resolution of colitis.

Dynamical Analysis of Drug Efficacy and Mechanism of Action Using GFP Reporters

To the development of effective cancer drug, it is necessary to, first, identify drugs and their possible combinations that could exert desired control over the type of cancer being considered; second, have a drug testing method that allows one to assess the variety of responses that can be provoked by drugs. To facilitate such an experiment-modeling-experiment cycle for drug development, a method based on the dynamical systems of pathways is presented. It involves a three-state experimental design: (1) formulate an oncologic pathway model of relevant cancer; (2) perturb the pathways with the drugs of known effects on components of the pathways of interest; and (3) measure process activity indicators at various points on cell populations. To evaluate the drug response in a high-throughput manner, a green fluorescent protein reporter-based technology has been developed. The authors apply the dynamical approach to several issues in the context of colon cancer cell lines.

Prophylactic vaccination targeting ERBB3 decreases polyp burden in a mouse model of human colorectal cancer

Prophylactic vaccination is typically utilized for the prevention of communicable diseases such as measles and influenza but, with the exception of vaccines to prevent cervical cancer, is not widely used as a means of preventing or reducing the incidence of cancer. Here, we utilize a peptide-based immunotherapeutic approach targeting ERBB3, a pseudo-kinase member of the EGFR/ERBB family of receptor tyrosine kinases, as a means of preventing occurrence of colon polyps. Administration of the peptide resulted in a significant decrease in the development of intestinal polyps in C57BL/6J-Apc^Min mice, a model of familial adenomatous polyposis (FAP). In addition, even though they were not vaccinated, Apc^Min offspring born to vaccinated females developed significantly fewer polyps than offspring born to control females. Lastly, to validate ERBB as a valid target for vaccination, we found no overt toxicity, increases in apoptosis, or morphological changes in tissues where Erbb3 was ablated in adult mice. These results indicate that prophylactic vaccination targeting ERBB3 could prevent the development of colon polyps in an at-risk patient population.

Genetic variants in ERBB4 is associated with chronic hepatitis B virus infection

Background

The role of ERBB4 in liver disease has seldom been reported. This study aims to find genetic markers at ERBB4 for chronic hepatitis B virus (HBV) infection and determine the role of ERBB4 in liver injury.

Methods

We selected and genotyped three single nucleotide polymorphisms and one insertion/deletion (Ins/Del) at the 5′ and 3′ untranslated region (UTR) of ERBB4 in a case-control study including 1344 pairs of HBV carriers and HBV natural clearance subjects. The luciferase reporter system was applied to study the regulative role of Ins/Del on ERBB4. Further, ERBB4 knockout mice were used to study the role of ERBB4 in liver injury. Proteomic quantification was performed by HPLC-MS/MS analysis to identify liver protein profile change between liver-specific ERBB4 knockout and control mice.

Results

rs6147150 Ins/Del and rs1836724 T>C at the 3′ UTR of ERBB4 were associated with reduced risk of chronic HBV infection (P = 0.002 and 0.004, respectively). Besides, the 12bp deletion at the 3′ UTR increased ERBB4 expression due to lacking let-7c binding site. In addition, loss of ERBB4 led to more severe acute or chronic inflammation in mouse liver injury models. Further, quantitative proteomic analysis and data from the cancer genome atlas revealed that ACLY, an enzyme key for de novo lipogenesis, was negatively correlated with ERBB4.

Conclusions

ERBB4 plays protective role from liver injury and its 3′UTR genetic variants could be genetic markers for chronic HBV infection.

Hepatocyte ERBB3 and EGFR are required for maximal CCl4-induced liver fibrosis

Epidermal growth factor receptor (EGFR) and its ligands have been implicated in liver fibrosis. However, it has not been directly shown that hepatocellular genetic ablation of either this receptor tyrosine kinase or ERBB3, its interactive signaling partner, affects hepatic fibrosis. Carbon tetrachloride (CCl₄)-induced liver fibrosis in hepatocyte-specific (HS) mouse models of EGFR and ERBB3 ablation was evaluated in both single gene knockouts and an HS-EGFR-ERBB3 double knockout (DKO). Loss of hepatocellular EGFR or ERBB3 did not impact cytochrome P450-2E1 expression, the extent of centrilobular injury, or the initial regenerative response, but it did diminish liver fibrosis induced by chronic intraperitoneal administration of CCl₄ The reduction of liver fibrosis correlated with reduced α-smooth muscle actin expression. Maximal impact to fibrogenesis occurred in the ERBB3 and EGFR-ERBB3 DKO models, suggesting that EGFR-ERBB3 heterodimeric signaling in damaged hepatocytes may play a more important role in liver fibrosis than EGFR-EGFR homodimeric signaling. Immunohistochemical analyses of phospho-EGFR and phospho-ERBB3 isoforms revealed clear staining in hepatocytes, activated stellate cells, and macrophages. Our results support a role for the hepatocellular ERBB tyrosine kinases in fibrogenesis and suggest that pharmacologic inhibition of EGFR-ERBB3 signaling may reverse or retard hepatic fibrosis.

Arhgap17, a RhoGTPase activating protein, regulates mucosal and epithelial barrier function in the mouse colon

Coordinated regulation of the actin cytoskeleton by the Rho GTPase family is required for the maintenance of polarity in epithelial cells as well as for their proliferation and migration. A RhoGTPase-activating protein 17 (Arhgap17) is known to be involved in multiple cellular processes in vitro, including the maintenance of tight junctions and vesicle trafficking. However, the function of Arhgap17 has not been studied in the physiological context. Here, we generated Arhgap17-deficient mice and examined the effect in the epithelial and mucosal barriers of the intestine. Reporter staining revealed that Arhgap17 expression is limited to the luminal epithelium of intestine. Arhgap17-deficient mice show an increased paracellular permeability and aberrant localization of the apical junction complex in the luminal epithelium, but do not develop spontaneous colitis. The inner mucus layer is impervious to the enteric bacteria irrespective of Tff3 downregulation in the Arhgap17-deficient mice. Interestingly however, treatment with dextran sulfate sodium (DSS) causes an increased accumulation of DSS and TNF production in intraluminal cells and rapid destruction of the inner mucus layer, resulting in increased severity of colitis in mutant mice. Overall, these data reveal that Arhgap17 has a novel function in regulating transcellular transport and maintaining integrity of intestinal barriers.

Downregulation of epidermal growth factor receptor family receptors and ligands in a mutant K-ras group of patients with colorectal cancer

The present study investigated the expression profiles of the epidermal growth factor receptor (EGFR) family, which consists of four transmembrane tyrosine kinase receptors and their eight ligands, in 122 patients with colorectal cancer (CRC) using reverse transcription-quantitative polymerase chain reaction analysis. On comparison of the CRC primary tumor and matched adjacent normal mucosa (ANM) tissue samples, the mRNA expression levels of ErbB3, but not ErbB1, were significantly increased in CRC tissue samples, compared with those in the ANM tissues. The expression levels of the ligands exhibited opposing trends to their corresponding receptors, including EGF, BTC, AREG, EREG and HB‑EGF, which were increased in the CRC tissues, whereas NRG1 and NGR2 were decreased in thee CRC tissues, compared with those in the AMN tissues. Subsequently, the present study investigated the frequency of K-ras mutations in the patients with CRC. The K‑ras mutations were found to be present in 36.8% (45/122) of the cases, however, no correlation was observed between K‑ras mutations and clinicopathological characteristics. In the CRC tissues, the expression levels of the EGFR family receptors and their ligands were determined in wild-type and mutant K-ras CRC cases. The expression levels of ErbB1, ErbB2, ErbB3, BTC, AREG, EREG, NRG1 and NRG2 were significantly decreased in the mutant K‑ras cases, compared with those in the wild‑type K‑ras cases. These results suggested that the tumorigenesis of CRC with wild‑type K‑ras was mediated through, not only ErbB1, but also through the ErbB2 and ErbB3 pathways. Notably, although ErbB2 does not bind any ErbB ligands, ErbB2 may activate tumorigenesis via a heterodimer, rather than a homodimer. Therefore, the results of the present study suggest that the most effective strategy to target not only ErbB1, but also ErbB2 and ErbB3, is the use of monoclonal antibody treatment.

The genetic and regulatory architecture of ERBB3-type 1 diabetes susceptibility locus

The study aimed to explore the role of ERBB3 in type 1 diabetes (T1D). We examined whether genetic variation of ERBB3 (rs2292239) affects residual β-cell function in T1D cases. Furthermore, we examined the expression of ERBB3 in human islets, the effect of ERBB3 knockdown on apoptosis in insulin-producing INS-1E cells and the genetic and regulatory architecture of the ERBB3 locus to provide insights to how rs2292239 may confer disease susceptibility. rs2292239 strongly correlated with residual β-cell function and metabolic control in children with T1D. ERBB3 locus associated lncRNA (NONHSAG011351) was found to be expressed in human islets. ERBB3 was expressed and down-regulated by pro-inflammatory cytokines in human islets and INS-1E cells; knockdown of ERBB3 in INS-1E cells decreased basal and cytokine-induced apoptosis. Our data suggests an important functional role of ERBB3 and its potential regulators in the β-cells and may constitute novel targets to prevent β-cell destruction in T1D.

Loss of hepatocyte ERBB3 but not EGFR impairs hepatocarcinogenesis

Epidermal growth factor receptor (EGFR) and ERBB3 have been implicated in hepatocellular carcinogenesis (HCC). However, it is not known whether altering the activity of either EGFR or ERBB3 affects HCC development. We now show that Egfr(Dsk5) mutant mice, which have a gain-of-function allele that increases basal EGFR kinase activity, develop spontaneous HCC by 10 mo of age. Their tumors show increased activation of EGFR, ERBB2, and ERBB3 as well as AKT and ERK1,2. Hepatocyte-specific models of EGFR and ERBB3 gene ablation were generated to evaluate how the loss of these genes affected tumor progression. Loss of either receptor tyrosine kinase did not alter liver development or regenerative liver growth following carbon tetrachloride injection. However, using a well-characterized model of HCC in which N-nitrosodiethylamine is injected into 14-day-old mice, we discovered that loss of hepatocellular ERBB3 but not EGFR, which occurred after tumor initiation, retarded liver tumor formation and cell proliferation. We found no evidence that this was due to increased apoptosis or diminished phosphatidylinositol-3-kinase activity in the ERBB3-null cells. However, the relative amount of phospho-STAT3 was diminished in tumors derived from these mice, suggesting that ERBB3 may promote HCC through STAT3 activation.

ADAM Proteases and Gastrointestinal Function

A disintegrin and metalloproteinases (ADAMs) are a family of cell surface proteases that regulate diverse cellular functions, including cell adhesion, migration, cellular signaling, and proteolysis. Proteolytically active ADAMs are responsible for ectodomain shedding of membrane-associated proteins. ADAMs rapidly modulate key cell signaling pathways in response to changes in the extracellular environment (e.g., inflammation) and play a central role in coordinating intercellular communication within the local microenvironment. ADAM10 and ADAM17 are the most studied members of the ADAM family in the gastrointestinal tract. ADAMs regulate many cellular processes associated with intestinal development, cell fate specification, and the maintenance of intestinal stem cell/progenitor populations. Several signaling pathway molecules that undergo ectodomain shedding by ADAMs [e.g., ligands and receptors from epidermal growth factor receptor (EGFR)/ErbB and tumor necrosis factor α (TNFα) receptor (TNFR) families] help drive and control intestinal inflammation and injury/repair responses. Dysregulation of these processes through aberrant ADAM expression or sustained ADAM activity is linked to chronic inflammation, inflammation-associated cancer, and tumorigenesis.

ERBB3 is required for tumor promotion in a mouse model of skin carcinogenesis

The epidermal growth factor receptor (EGFR) plays a key role in skin inflammation, wound healing, and carcinogenesis. Less is known about the functions of the structurally related receptor ERBB3 (HER3) in the skin. We assessed the requirement of ERBB3 for skin homeostasis, wound healing, and tumorigenesis by crossing mice carrying a conditional Erbb3 allele with animals expressing cre under the control of the keratin 5 promoter. Erbb3(del) mice, lacking ERBB3 specifically in keratinocytes, showed no obvious abnormalities. The EGFR was upregulated in Erbb3(del) skin, possibly compensating the loss of ERBB3. Nonetheless, healing of full-thickness excisional wounds was negatively affected by ERBB3 deficiency. To analyze the function of ERBB3 during tumorigenesis, we employed the established DMBA/TPA multi-stage chemical carcinogenesis protocol. Erbb3(del) mice remained free of papillomas for a longer time and had significantly reduced tumor burden compared to control littermates. Tumor cell proliferation was considerably reduced in Erbb3(del) mice, and loss of ERBB3 also impaired keratinocyte proliferation after a single application of TPA. In human skin tumor samples, upregulated ERBB3 expression was observed in squamous cell carcinoma, condyloma, and malignant melanoma. Thus, we conclude that ERBB3, while dispensable for the development and the homeostasis of the epidermis and its appendages, is required for proper wound healing and for the progression of skin tumors during multi-stage chemical carcinogenesis in mice. ERBB3 may also be important for human skin cancer progression. The latter effects most probably reflect a key role for ERBB3 in increasing cell proliferation after stimuli as wounding or carcinogenesis.

RasGRP1 opposes proliferative EGFR-SOS1-Ras signals and restricts intestinal epithelial cell growth

The character of EGFR signals can influence cell fate but mechanistic insights into intestinal EGFR-Ras signalling are limited. Here we show that two distinct Ras nucleotide exchange factors, RasGRP1 and SOS1, lie downstream of EGFR but act in functional opposition. RasGRP1 is expressed in intestinal crypts where it restricts epithelial growth. High RasGRP1 expression in colorectal cancer (CRC) patient samples correlates with a better clinical outcome. Biochemically, we find that RasGRP1 creates a negative feedback loop that limits proliferative EGFR-SOS1-Ras signals in CRC cells. Genetic Rasgrp1 depletion from mice with either an activating mutation in KRas or with aberrant Wnt signalling due to a mutation in Apc resulted in both cases in exacerbated Ras-ERK signalling and cell proliferation. The unexpected opposing cell biological effects of EGFR-RasGRP1 and EGFR-SOS1 signals in the same cell shed light on the intricacy of EGFR-Ras signalling in normal epithelium and carcinoma.

ERBB3 knockdown induces cell cycle arrest and activation of Bak and Bax-dependent apoptosis in colon cancer cells

ERBB3 is an emerging target for cancer therapy among the EGFR family. Contrary to resistance against EGFR and ERBB2 targeting, the genetic inhibition of ERBB3 results in anti-tumorigenic in HCT116 colon cancer cells harboring constitutively active KRAS and PIK3CA mutations. Still, the anti-tumorigenic molecular mechanism has not been defined. We demonstrated in this study that ERBB3 knockdown resulted in cell cycle arrest and activation of Bak and Bax-dependent apoptosis. Apoptosis was irrelevant to the majority of BH3-only pro-apoptotic proteins and correlated with the transcriptional upregulation of Bak and p53-dependent Bax translocation. Treatment with LY294002, a PI3K inhibitor, resulted in cell cycle arrest without apoptosis and a concomitant down-regulation of cap-dependent translation by the suppression of the PI3K/AKT/mTOR pathway. However, the inhibition of cap-dependent translation by ERBB3 knockdown occurred without altering the PI3K/AKT/mTOR pathway. In addition, ERBB3 knockdown-induced cell cycle arrest was observed in most colon cancer cells but was accompanied by apoptosis in p53 wild-type cells. These results indicate that ERBB3 is a potential target for EGFR- and ERBB2-resistant colon cancer therapy.

ERBB4 is over-expressed in human colon cancer and enhances cellular transformation

The ERBB4 receptor tyrosine kinase promotes colonocyte survival. Herein, we tested whether ERBB4's antiapoptotic signaling promotes transformation and colorectal tumorigenesis. ERBB4 alterations in a The Cancer Genome Atlas colorectal cancer (CRC) data set stratified survival, and in a combined Moffitt Cancer Center and Vanderbilt Medical Center CRC expression data set, ERBB4 message levels were increased at all tumor stages. Similarly, western blot and immunohistochemistry on additional CRC tissue banks showed elevated ERBB4 protein in tumors. ERBB4 was highly expressed in aggressive, dedifferentiated CRC cell lines, and its knockdown in LIM2405 cells reduced anchorage-independent colony formation. In nude mouse xenograft studies, ERBB4 alone was insufficient to induce tumor establishment of non-transformed mouse colonocytes, but its over-expression in cells harboring Apc(min) and v-Ha-Ras caused a doubling of tumor size. ERBB4-expressing xenografts displayed increased activation of survival pathways, including epidermal growth factor receptor and Akt phosphorylation and COX-2 expression, and decreased apoptotic signals. Finally, ERBB4 deletion from mouse intestinal epithelium impaired stem cell replication and in vitro enteroid establishment. In summary, we report that ERBB4 is over-expressed in human CRC, and in experimental systems enhances the survival and growth of cells driven by Ras and/or WNT signaling. Chronic ERBB4 over-expression in the context of, for example, inflammation may contribute to colorectal carcinogenesis. Tumors with high receptor levels are likely to have enhanced cell survival signaling through epidermal growth factor receptor, PI3K and COX-2. These results suggest ERBB4 as a novel therapeutic target in a subset of CRC.

Alteration of WWOX in human cancer: a clinical view

WWOX gene is located in FRA16D, the highly affected chromosomal fragile site. Its tumor suppressor activity has been proposed on a basis of numerous genomic alterations reported in chromosome 16q23.3-24.1 locus. WWOX is affected in many cancers, showing as high as 80% loss of heterozygosity in breast tumors. Unlike most tumor suppressors impairing of both alleles of WWOX is very rare. Despite cellular and animal models information on a WWOX role in cancer tissue is limited and sometimes confusing. This review summarizes information on WWOX in human tumors.

ERBB3-independent activation of the PI3K pathway in EGFR-mutant lung adenocarcinomas

ERBB3, a member of the EGFR family of receptor tyrosine kinases, has been implicated in activation of the PI3K pathway in human lung adenocarcinomas driven by EGFR mutations. We investigated the contribution of ERBB3 to the initiation, progression, and therapeutic response of EGFR-induced lung adenocarcinomas using tetracycline- and tamoxifen-inducible transgenic mouse models. Deletion of Erbb3 at the time of induction of mutant EGFR had no effect on tumorigenesis, demonstrating that ERBB3 is not required to initiate tumorigenesis. Tumors that developed in the absence of ERBB3 remained sensitive to EGFR tyrosine kinase inhibitors and retained activation of the PI3K-AKT pathway. Interestingly, acute loss of Erbb3 suppressed further growth of established EGFR(L858R)-mediated lung tumors. Four weeks after deletion of Erbb3, the tumors exhibited phosphorylation of EGFR, of the adaptor proteins GAB1 and GAB2, and of the downstream signaling molecules AKT and ERK, suggesting that alternative signaling pathways could compensate for loss of Erbb3. Similar to our observations with mouse tumors, we found that GAB adaptor proteins play a role in ERBB3-independent activation of the PI3K pathway by mutant EGFR in EGFR-mutant human cell lines. Finally, in such cell lines, increased levels of phosphorylation of ERBB2 or MET were associated with reduced sensitivity to acute loss of ERBB3, suggesting remarkable plasticity in the signaling pathways regulated by mutant EGFR with important therapeutic implications.

Effect of BRAF mutational status on expression profiles in conventional papillary thyroid carcinomas

BACKGROUND

Whereas 40 % to 70 % of papillary thyroid carcinomas (PTCs) are characterized by a BRAF mutation (BRAFmut), unified biomarkers for the genetically heterogeneous group of BRAF wild type (BRAFwt) PTCs are not established yet. Using state-of-the-art technology we compared RNA expression profiles between conventional BRAFwt and BRAFmut PTCs.

METHODS

Microarrays covering 36,079 reference sequences were used to generate whole transcript expression profiles in 11 BRAFwt PTCs including five micro PTCs, 14 BRAFmut PTCs, and 7 normal thyroid specimens. A p-value with a false discovery rate (FDR) < 0.05 and a fold change > 2 were used as a threshold of significance for differential expression. Network and pathway utilities were employed to interpret significance of expression data. BRAF mutational status was established by direct sequencing the hotspot region of exon 15.

RESULTS

We identified 237 annotated genes that were significantly differentially expressed between BRAFwt and BRAFmut PTCs. Of these, 110 genes were down- and 127 were upregulated in BRAFwt compared to BRAFmut PTCs. A number of molecules involved in thyroid hormone metabolism including thyroid peroxidase (TPO) were differentially expressed between both groups. Among cancer-associated molecules were ERBB3 that was downregulated and ERBB4 that was upregulated in BRAFwt PTCs. Two microRNAs were significantly differentially expressed of which miR492 bears predicted functions relevant to thyroid-specific molecules. The protein kinase A (PKA) and the G protein-coupled receptor pathways were identified as significantly related signaling cascades to the gene set of 237 genes. Furthermore, a network of interacting molecules was predicted on basis of the differentially expressed gene set.

CONCLUSIONS

The expression study focusing on affected genes that are differentially expressed between BRAFwt and BRAFmut conventional PTCs identified a number of molecules which are connected in a network and affect important canonical pathways. The identified gene set adds to our understanding of the tumor biology of BRAFwt and BRAFmut PTCs and contains genes/biomarkers of interest.

Localization of phosphorylated ErbB1-4 and heregulin in colorectal cancer

Background

The ErbB family consists of four proteins including (EGFR)/ErbB1, ErbB2, ErbB3, and ErbB4, and plays a crucial role in the promotion of multiple tumorigenic processes. In addition to the traditional pathways of EGFR signaling, EGFR translocates to the nucleus and acts as a transcription factor in the proliferation of cancer cells. Heregulin is known as both an ErbB3 and an ErbB4 ligand. This study aimed to investigate the expression of heregulin and its relevant EGFR family members as well as their phosphorylated forms in human colorectal cancer (CRC) tissues and to determine the relationship between their expression and clinicopathological factors including patient prognosis.

Methods

We analyzed the effects of exogenous heregulin on ErbB2, ErbB3 and ErbB4 phosphorylation in Caco-2, DLD-1, and HCT 116 colon cancer cell lines by western blot analysis. We examined 155 surgical resections from colorectomy patients. Cellular localization of ErbB1-4, their phosphorylated forms and heregulin protein was analyzed in CRC surgical resections by immunohistochemical analysis. Immunohistochemical results were compared with clinicopathological factors and patient prognosis.

Results

Phosphorylated ErbB2 (pErbB2) and phosphorylated ErbB3 (pErbB3) were detected in both nuclear and cytosolic fractions of Caco-2 and DLD-1 cells stimulated by exogenous heregulin. Whereas, phosphorylated ErbB4 (pErbB4) was detected only in cytosolic fractions of HCT 116 cells stimulated by exogenous heregulin. Phosphorylated EGFR (pEGFR) immunoreactivity was observed in the cytoplasm and nuclei of cancer cells, whereas the pattern of EGFR staining was membranous and cytoplasmic. Subcellular localization of pErbB2, cytoplasmic, membranous, or nuclear, varied among cases. pErbB3 immunoreactivity was exclusively observed in the nuclei of cancer cells. pErbB4 immunoreactivity was observed in the cell membrane of cancer cells. Statistically, heregulin immunoreactivity correlated with pErbB2 and pErbB4 expression. In multivariate analysis for disease free survival, lymph node status, pErbB3 and pErbB4 expression retained independent prognostic significance. In multivariate analysis for overall survival, lymph node status, pEGFR and pErbB4 retained independent prognostic significance.

Conclusions

ErbB2 and ErbB3 phosphorylated by heregulin localized in the nucleus of CRC cells. Phosphorylated ErbB1-4 and heregulin contribute to poorer patient prognosis in CRC. This heregulin-ErbB family member autocrine loop may be a candidate for targeted treatment of CRC.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-863) contains supplementary material, which is available to authorized users.

The ErbB4 ligand neuregulin-4 protects against experimental necrotizing enterocolitis

Necrotizing enterocolitis (NEC) affects up to 10% of premature infants, has a mortality of 30%, and can leave surviving patients with significant morbidity. Neuregulin-4 (NRG4) is an ErbB4-specific ligand that promotes epithelial cell survival. Thus, this pathway could be protective in diseases such as NEC, in which epithelial cell death is a major pathologic feature. We sought to determine whether NRG4-ErbB4 signaling is protective in experimental NEC. NRG4 was used i) in the newborn rat formula feeding/hypoxia model; ii) in a recently developed model in which 14- to 16-day-old mice are injected with dithizone to induce Paneth cell loss, followed by Klebsiella pneumoniae infection to induce intestinal injury; and iii) in bacterially infected IEC-6 cells in vitro. NRG4 reduced NEC incidence and severity in the formula feed/hypoxia rat model. It also reduced Paneth cell ablation-induced NEC and prevented dithizone-induced Paneth cell loss in mice. In vitro, cultured ErbB4(-/-) ileal epithelial enteroids had reduced Paneth cell markers and were highly sensitive to inflammatory cytokines. Furthermore, NRG4 blocked, through a Src-dependent pathway, Cronobacter muytjensii-induced IEC-6 cell apoptosis. The potential clinical relevance of these findings was demonstrated by the observation that NRG4 and its receptor ErbB4 are present in human breast milk and developing human intestine, respectively. Thus, NRG4-ErbB4 signaling may be a novel pathway for therapeutic intervention or prevention in NEC.