EGFR family: structure physiology signalling and therapeutic targets

Epidermal growth factor receptor ligands: targets for optimizing treatment of metastatic colorectal cancer

The discovery of epidermal growth factor (EGF) and its receptor (EGFR) revealed the connection between EGF-like ligands, signaling from the EGFR family members and cancer. Over the next fifty years, analysis of EGFR expression and mutation led to the use of monoclonal antibodies to target EGFR in the treatment of metastatic colorectal cancer (mCRC) and this treatment has improved outcomes for patients. The use of the RAS oncogene mutational status has helped to refine patient selection for EGFR antibody therapy, but an effective molecular predictor of likely responders is lacking. This review analyzes the potential utility of measuring the expression, levels and activation of EGF-like ligands and associated processes as prognostic or predictive markers for the identification of patient risk and more effective mCRC therapies.

ADAM17: An Emerging Therapeutic Target for Lung Cancer

Lung cancer is the leading cause of cancer-related mortality, which histologically is classified into small-cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC accounts for approximately 85% of all lung cancer diagnoses, with the majority of patients presenting with lung adenocarcinoma (LAC). KRAS mutations are a major driver of LAC, and are closely related to cigarette smoking, unlike mutations in the epidermal growth factor receptor (EGFR) which arise in never-smokers. Although the past two decades have seen fundamental progress in the treatment and diagnosis of NSCLC, NSCLC still is predominantly diagnosed at an advanced stage when therapeutic interventions are mostly palliative. A disintegrin and metalloproteinase 17 (ADAM17), also known as tumour necrosis factor-α (TNFα)-converting enzyme (TACE), is responsible for the protease-driven shedding of more than 70 membrane-tethered cytokines, growth factors and cell surface receptors. Among these, the soluble interleukin-6 receptor (sIL-6R), which drives pro-inflammatory and pro-tumourigenic IL-6 trans-signaling, along with several EGFR family ligands, are the best characterised. This large repertoire of substrates processed by ADAM17 places it as a pivotal orchestrator of a myriad of physiological and pathological processes associated with the initiation and/or progression of cancer, such as cell proliferation, survival, regeneration, differentiation and inflammation. In this review, we discuss recent research implicating ADAM17 as a key player in the development of LAC, and highlight the potential of ADAM17 inhibition as a promising therapeutic strategy to tackle this deadly malignancy.

Altered immunoreactivity of ErbB4, a causative gene product for ALS19, in the spinal cord of patients with sporadic ALS

ErbB4 is the protein implicated in familial amyotrophic lateral sclerosis (ALS), designated as ALS19. ErbB4 is a receptor tyrosine kinase activated by its ligands, neuregulins (NRG), and plays an essential role in the function and viability of motor neurons. Mutations in the ALS19 gene lead to the reduced autophosphorylation capacity of the ErbB4 protein upon stimulation with NRG‐1, suggesting that the disruption of the NRG–ErbB4 pathway causes motor neuron degeneration. We used immunohistochemistry to study ErbB4 in the spinal cord of patients with sporadic ALS (SALS) to test the hypothesis that ErbB4 may be involved in the pathogenesis of SALS. ErbB4 was specifically immunoreactive in the cytoplasm of motor neurons in the anterior horns of the spinal cord. In patients with SALS, some of the motor neurons lost immunoreactivity with ErbB4, with the proportion of motor neurons with a loss of immunoreactivity correlated with the severity of motor neuron loss. The subcellular localization was altered, demonstrating nucleolar or nuclear localization, threads/dots and spheroids. The ectopic glial immunoreactivity was observed, mainly in the oligodendrocytes of the lateral columns and anterior horns. The reduction in the ErbB4 immunoreactivity was significantly correlated with the cytoplasmic mislocalization of transactivation response DNA‐binding protein 43 kDa (TDP‐43) in the motor neurons. No alteration in immunoreactivity was observed in the motor neurons of mice carrying atransgene for mutant form of the superoxide dismutase 1 gene (SOD1). This study provided compelling evidence that ErbB4 is also involved in the pathophysiology of SALS, and that the disruption of the NRG–ErbB4 pathway may underlie the TDP‐43‐dependent motor neuron degeneration in ALS.

Autophosphorylation of Orphan Receptor ERBB2 Can Be Induced by Extracellular Treatment with Mildly Alkaline Media

ErbB2 is an oncogene receptor tyrosine kinase linked to breast cancer. It is a member of the epidermal growth factor receptor (EGFR) minifamily. ErbB2 is currently viewed as an orphan receptor since, by itself, it does not bind EGF-like ligands and can be activated only when overexpressed in malignant cells or complexed with ErbB3, another member of the EGFR minifamily. Here, we report that ErbB2 can be activated by extracellular application of mildly alkaline (pH 8–9) media to ErbB2-transfected cells. We also show that the activation of the ErbB2 receptor by alkali is dose-dependent and buffer-independent. The endogenous ErbB2 receptor of A431 cell line can also undergo alkali-dependent autophosphorylation. Thus, we describe a novel ligand-independent mechanism of ErbB2 receptor activation.

Small molecule-mediated reprogramming of human hepatocytes into bipotent progenitor cells

BACKGROUND & AIMS

Currently, much effort is directed towards the development of new cell sources for clinical therapy using cell fate conversion by small molecules. Direct lineage reprogramming to a progenitor state has been reported in terminally differentiated rodent hepatocytes, yet remains a challenge in human hepatocytes.

METHODS

Human hepatocytes were isolated from healthy and diseased donor livers and reprogrammed into progenitor cells by 2 small molecules, A83-01 and CHIR99021 (AC), in the presence of EGF and HGF. The stemness properties of human chemically derived hepatic progenitors (hCdHs) were tested by standard in vitro and in vivo assays and transcriptome profiling.

RESULTS

We developed a robust culture system for generating hCdHs with therapeutic potential. The use of HGF proved to be an essential determinant of the fate conversion process. Based on functional evidence, activation of the HGF/MET signal transduction system collaborated with A83-01 and CHIR99021 to allow a rapid expansion of progenitor cells through the activation of the ERK pathway. hCdHs expressed hepatic progenitor markers and could self-renew for at least 10 passages while retaining a normal karyotype and potential to differentiate into functional hepatocytes and biliary epithelial cells in vitro. Gene expression profiling using RNAseq confirmed the transcriptional reprogramming of hCdHs towards a progenitor state and the suppression of mature hepatocyte transcripts. Upon intrasplenic transplantation in several models of therapeutic liver repopulation, hCdHs effectively repopulated the damaged parenchyma.

CONCLUSION

Our study is the first report of successful reprogramming of human hepatocytes to a population of proliferating bipotent cells with regenerative potential. hCdHs may provide a novel tool that permits expansion and genetic manipulation of patient-specific progenitors to study regeneration and the repair of diseased livers.

LAY SUMMARY

Human primary hepatocytes were reprogrammed towards hepatic progenitor cells by a combined treatment with 2 small molecules, A83-01 and CHIR99021, and HGF. Chemically derived hepatic progenitors exhibited a high proliferation potential and the ability to differentiate into hepatocytes and biliary epithelial cells both in vitro and in vivo. This approach enables the generation of patient-specific hepatic progenitors and provides a platform for personal and stem cell-based regenerative medicine.

Overview of CD24 as a new molecular marker in ovarian cancer

Ovarian cancer (OC) is the fifth leading cause of cancer-related death among women. The high mortality rate is due to lack of early symptoms, late diagnosis, limited treatment options, and also emerging of drug resistance. Todays, molecular markers have become promising in tumor-targeted therapy. Several molecular markers have been known in OC immunotherapy. Identification of the specific molecular markers with prognostic significance is interested. CD24 is a small sialoglycoprotein which is localized in lipid rafts through its glycosylphosphatidylinositol (GPI) anchor. It has been reported that CD24 is overexpressed in many cancers including OC. Also, CD24 is identified as a cancer stem cell marker in OC. The CD24 expression is associated with the development, invasion, and metastasis of cancer cells. The exact role of CD24 in cancer cells is not clearly understood. Recently, CD24 has been identified as an independent prognostic marker of survival in patients with OC. In this study, we reviewed the molecular targets in OC immune-targeted therapy and also presented an overview of the new molecular marker CD24 and its association with the OC by reviewing the recent literature.

Mechanisms Underlying the Action and Synergism of Trastuzumab and Pertuzumab in Targeting HER2-Positive Breast Cancer

Human epidermal growth factor receptor (HER) 2 (HER2) is overexpressed in 20⁻30% of breast cancers. HER2 is a preferred target for treating HER2-positive breast cancer. Trastuzumab and pertuzumab are two HER2-targeted monoclonal antibodies approved by the Food and Drug Administration (FDA) to use as adjuvant therapy in combination with docetaxel to treat metastatic HER2-positive breast cancer. Adding the monoclonal antibodies to treatment regimen has changed the paradigm for treatment of HER2-positive breast cancer. Despite improving outcomes, the percentage of the patients who benefit from the treatment is still low. Continued research and development of novel agents and strategies of drug combinations is needed. A thorough understanding of the molecular mechanisms underlying the action and synergism of trastuzumab and pertuzumab is essential for moving forward to achieve high efficacy in treating HER2-positive breast cancer. This review examined and analyzed findings and hypotheses regarding the action and synergism of trastuzumab and pertuzumab and proposed a model of synergism based on available information.

Exploitation of receptor tyrosine kinases by viral-encoded growth factors

Receptor tyrosine kinases (RTKs) are essential components of cell communication pathways utilized from the embryonic to adult stages of life. These transmembrane receptors bind polypeptide ligands, such as growth factors, inducing signalling cascades that control cellular processes such as proliferation, survival, differentiation, motility and inflammation. Many viruses have acquired homologs of growth factors encoded by the hosts that they infect. Production of growth factors during infection allows viruses to exploit RTKs for entry and replication in cells, as well as for host and environmental dissemination. This review describes the genetic diversity amongst virus-derived growth factors and the mechanisms by which RTK exploitation enhances virus survival, then highlights how viral ligands can be used to further understanding of RTK signalling and function during embryogenesis, homeostasis and disease scenarios.

Breast cancer development and progression: Risk factors, cancer stem cells, signaling pathways, genomics, and molecular pathogenesis

As the most commonly occurring cancer in women worldwide, breast cancer poses a formidable public health challenge on a global scale. Breast cancer consists of a group of biologically and molecularly heterogeneous diseases originated from the breast. While the risk factors associated with this cancer varies with respect to other cancers, genetic predisposition, most notably mutations in BRCA1 or BRCA2 gene, is an important causative factor for this malignancy. Breast cancers can begin in different areas of the breast, such as the ducts, the lobules, or the tissue in between. Within the large group of diverse breast carcinomas, there are various denoted types of breast cancer based on their invasiveness relative to the primary tumor sites. It is important to distinguish between the various subtypes because they have different prognoses and treatment implications. As there are remarkable parallels between normal development and breast cancer progression at the molecular level, it has been postulated that breast cancer may be derived from mammary cancer stem cells. Normal breast development and mammary stem cells are regulated by several signaling pathways, such as estrogen receptors (ERs), HER2, and Wnt/β-catenin signaling pathways, which control stem cell proliferation, cell death, cell differentiation, and cell motility. Furthermore, emerging evidence indicates that epigenetic regulations and noncoding RNAs may play important roles in breast cancer development and may contribute to the heterogeneity and metastatic aspects of breast cancer, especially for triple-negative breast cancer. This review provides a comprehensive survey of the molecular, cellular and genetic aspects of breast cancer.

Potential lymphangiogenesis therapies: Learning from current antiangiogenesis therapies-A review

In recent years, lymphangiogenesis, the process of lymphatic vessel formation from existing lymph vessels, has been demonstrated to have a significant role in diverse pathologies, including cancer metastasis, organ graft rejection, and lymphedema. Our understanding of the mechanisms of lymphangiogenesis has advanced on the heels of studies demonstrating vascular endothelial growth factor C as a central pro-lymphangiogenic regulator and others identifying multiple lymphatic endothelial biomarkers. Despite these breakthroughs and a growing appreciation of the signaling events that govern the lymphangiogenic process, there are no FDA-approved drugs that target lymphangiogenesis. In this review, we reflect on the lessons available from the development of antiangiogenic therapies (26 FDA-approved drugs to date), review current lymphangiogenesis research including nanotechnology in therapeutic drug delivery and imaging, and discuss molecules in the lymphangiogenic pathway that are promising therapeutic targets.

NRG1-Fc improves metabolic health via dual hepatic and central action

Neuregulins (NRGs) are emerging as an important family of signaling ligands that regulate glucose and lipid homeostasis. NRG1 lowers blood glucose levels in obese mice, whereas the brown fat-enriched secreted factor NRG4 protects mice from high-fat diet-induced insulin resistance and hepatic steatosis. However, the therapeutic potential of NRGs remains elusive, given the poor plasma half-life of the native ligands. Here, we engineered a fusion protein using human NRG1 and the Fc domain of human IgG1 (NRG1-Fc) that exhibited extended half-life in circulation and improved potency in receptor signaling. We evaluated its efficacy in improving metabolic parameters and dissected the mechanisms of action. NRG1-Fc treatment triggered potent AKT activation in the liver, lowered blood glucose, improved insulin sensitivity, and suppressed food intake in obese mice. NRG1-Fc acted as a potent secretagogue for the metabolic hormone FGF21; however, the latter was largely dispensable for its metabolic effects. NRG1-Fc directly targeted the hypothalamic POMC neurons to promote membrane depolarization and increase firing rate. Together, NRG1-Fc exhibits improved pharmacokinetic properties and exerts metabolic benefits through dual inhibition of hepatic gluconeogenesis and caloric intake.

The effects of trastuzumab on HER2-mediated cell signaling in CHO cells expressing human HER2

BACKGROUND

Targeted therapy with trastuzumab has become a mainstay for HER2-positive breast cancer without a clear understanding of the mechanism of its action. While many mechanisms have been suggested for the action of trastuzumab, most of them are not substantiated by experimental data. It has been suggested that trastuzumab functions by inhibiting intracellular signaling initiated by HER2, however, the data are very controversial. A major issue is the different cellular background of various breast cancer cells lines used in these studies. Each breast cancer cell line has a unique expression profile of various HER receptors, which could significantly affect the effects of trastuzumab.

METHODS

To overcome this problem, in this research we adopted a cell model that allow us to specifically examine the effects of trastuzumab on a single HER receptor without the influence of other HER receptors. Three CHO cell lines stably expressing only human EGFR (CHO-EGFR), HER2 (CHO-K6), or HER3 (CHO-HER3) were used. Various methods including cytotoxicity assay, immunoblotting, indirect immunofluorescence, cross linking, and antibody-dependent cellular cytotoxicity (ADCC) were employed in this research.

RESULTS

We showed that trastuzumab did not bind EGFR and HER3, and thus did not affect the homodimerization and phosphorylation of EGFR and HER3. However, overexpression of HER2 in CHO cells, in the absence of other HER receptors, resulted in the homodimerization of HER2 and the phosphorylation of HER2 at all major pY residues. Trastuzumab bound to HER2 specifically and with high affinity. Trastuzumab inhibited neither the homodimerization of HER2, nor the phosphorylation of HER2 at most phosphotyrosine residues. Moreover, trastuzumab did not inhibit the phosphorylation of ERK and AKT in CHO-K6 cells, and did not inhibit the proliferation of CHO-K6 cells. However, trastuzumab induced strong ADCC in CHO-K6 cells.

CONCLUSION

We concluded that, in the absence of other HER receptors, trastuzumab exerts its antitumor activity through the induction of ADCC, rather than the inhibition of HER2-homodimerization and phosphorylation.

Effect of neoadjuvant chemotherapy and its correlation with HPV status, EGFR, Her-2-neu, and GADD45 expression in oral squamous cell carcinoma

Background

Head and neck cancers are the commonest cancer in Southeast Asia. Despite being a surface cancer, it is associated with significant morbidity as despite early detection by the patients they often report for treatment late and hence are associated with poor prognosis. The role of neoadjuvant chemotherapy in head and neck cancer is still under evaluation; there is a large subgroup of population that does not respond to chemotherapy, and hence, most studies have failed to show any survival benefit. This study evaluated the role of neoadjuvant therapy with docetaxel and carboplatin in patients with oral cancer and correlated the response to human papilloma virus, EGFR1, EGFR2, and GADD45 expression.

Methods

A total of 24 locally advanced, non-metastatic oral cancer patients were included in the study. Tumor biopsies were taken prior to the start of neoadjuvant therapy for expression of EGFR, Her-2-Neu, and GADD45 by immunohistochemistry and for HPV by PCR. The response was evaluated using Response Evaluation Criteria in Solid Tumors (RECIST) criteria after three cycles of chemotherapy. Statistical analysis was performed using correlation and Kaplan–Meier analysis; the difference in survival was calculated with log rank test.

Results

A total of 21 male and 3 female with a mean age of 53.12 years were enrolled. Sixty-five percent of these received three cycles of chemotherapy. Five patients were positive for HPV 16 and none for HPV 18. Twenty-two of 24 patients showed GADD45 expression, 3 showed expression of Her-2-Neu while all 24 showed expression for EGFR1 protein. Two-year overall survival was 81%; GADD45 expressions were found to significantly affect the overall and disease-free survival, while any of the other protein expression studied and HPV status was not significant.

Conclusion

The result of the present study shows significant downgrading of the oral cancers with neoadjuvant chemotherapy suggesting its utility in borderline operable cases. However, the response of chemotherapy does not appear to be related to the expression of EGFR, Her-2-Neu, and GADD45 protein or presence of HPV. Bone involvement, perineural invasion, and GADD45 expression significantly predict OS and DFS. All patients who did not express Gadd45 died before 2 years. Study with more subjects and longer follow-up should be carried out to elucidate this relation further.

PP2A as the Main Node of Therapeutic Strategies and Resistance Reversal in Triple-Negative Breast Cancer

Triple negative breast cancer (TNBC), is defined as a type of tumor lacking the expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). The ER, PR and HER2 are usually the molecular therapeutic targets for breast cancers, but they are ineffective for TNBC because of their negative expressions, so chemotherapy is currently the main treatment strategy in TNBC. However, drug resistance remains a major impediment to TNBC chemotherapeutic treatment. Recently, the protein phosphatase 2A (PP2A) has been found to regulate the phosphorylation of some substrates involved in the relevant target of TNBC, such as cell cycle control, DNA damage responses, epidermal growth factor receptor, immune modulation and cell death resistance, which may be the effective therapeutic strategies or influence drug sensitivity to TNBCs. Furthermore, PP2A has also been found that could induce ER re-expression in ER-negative breast cancer cells, and which suggests PP2A could promote the sensitivity of tamoxifen to TNBCs as a resistance reversal agent. In this review, we will summarize the potential therapeutic value of PP2A as the main node in developing targeting agents, disrupting resistance or restoring drug sensitivity in TNBC.

The rs2292239 polymorphism in ERBB3 gene is associated with risk for type 1 diabetes mellitus in a Brazilian population

The Erb-b2 receptor tyrosine kinase 3 (ERBB3) belongs to a family of epidermal growth factor receptors of protein tyrosine kinases, and regulates cell survival, differentiation and proliferation in several cell types. Previous studies have suggested that ERBB3 contributes to T1DM pathogenesis by modulating antigen presenting cell function, autoimmunity and cytokine-induced beta-cell apoptosis. Accordingly, some genome-wide association studies identified ERBB3 gene as a susceptibility locus for T1DM, with the strongest association signal being observed for the rs2292239 single nucleotide polymorphism (SNP) in intron 7 of the gene. Therefore, the aim of the present study was to replicate the association of the ERBB3 rs2292239 SNP with T1DM in a Brazilian population. We analyzed 421 T1DM patients (cases) and 510 nondiabetic subjects (controls). All subjects were self-declared as white. The ERBB3 rs2292239 (A/C) SNP was genotyped by real-time PCR using TaqMan MGB probes. Genotype (P=0.001) and allele (P=0.002) frequencies of the ERBB3 rs2292239 SNP were differently distributed between T1DM patients and nondiabetic controls. Moreover, the A allele was significantly associated with risk for T1DM when considering recessive (OR=1.58, 95% CI 1.11-2.27; P=0.015), additive (OR=1.78, 95% CI 1.21-2.62; P=0.004), and dominant (OR=1.39, 95% CI 1.07-1.81; P=0.016) models of inheritance. However, after adjustment for presence of high-risk HLA DR/DQ genotypes, the rs2292239 SNP remained independently associated with T1DM only for the additive model (OR=1.62, 95% CI 1.02-2.59; P=0.043). Our results suggest that the A/A genotype of the ERBB3 rs2292239 SNP is associated with risk for T1DM in a white Brazilian population.

The role of HER2, EGFR, and other receptor tyrosine kinases in breast cancer

Breast cancer affects approximately 1 in 8 women, and it is estimated that over 246,660 women in the USA will be diagnosed with breast cancer in 2016. Breast cancer mortality has decline over the last two decades due to early detection and improved treatment. Over the last few years, there is mounting evidence to demonstrate the prominent role of receptor tyrosine kinases (RTKs) in tumor initiation and progression, and targeted therapies against the RTKs have been developed, evaluated in clinical trials, and approved for many cancer types, including breast cancer. However, not all breast cancers are the same as evidenced by the multiple subtypes of the disease, with some more aggressive than others, showing differential treatment response to different types of drugs. Moreover, in addition to canonical signaling from the cell surface, many RTKs can be trafficked to various subcellular compartments, e.g., the multivesicular body and nucleus, where they carry out critical cellular functions, such as cell proliferation, DNA replication and repair, and therapeutic resistance. In this review, we provide a brief summary on the role of a selected number of RTKs in breast cancer and describe some mechanisms of resistance to targeted therapies.

Fatty acid synthase affects expression of ErbB receptors in epithelial to mesenchymal transition of breast cancer cells and invasive ductal carcinoma

The aim of the present study was to investigate changes in the expression of ErbBs during epithelial-mesenchymal transition (EMT) of breast cancer cells and its association with the expression of fatty acid synthase (FASN). MCF-7-MEK5 cells were used as the experimental model, while MCF-7 cells were used as a control. Tumor cells were implanted into nude mice for in vivo analysis. Cerulenin was used as a FASN inhibitor. Reverse transcription-polymerase chain reaction and western blot analysis were used to detect expression levels of FASN and ErbB1-4. Immunohistochemistry was used to detect the expression of FASN and ErbB1-4 in 58 invasive ductal carcinomas (IDC), as well as their association with clinicopathological characteristics. The expression of FASN and ErbB1-4 in MCF-7-MEK5 cells and tumor tissues increased significantly compared with controls (P<0.001). Inhibition of FASN by cerulenin resulted in a significant decrease in expression of ErbB1, 2 and 4 (P<0.001), whereas there was no evident change in ErbB3. In IDC samples, the expression of FASN and ErbB1-4 increased considerably in lymph node metastases compared with non-lymph node metastases (P<0.05). ErbB2 expression increased in advanced clinical stages (II, III and IV) of IDC and in tumors with larger diameters (P<0.05). The expression of ErbB3 increased in ER-positive tumors (P<0.05). Additionally, a positive association between the expression of FASN and ErbB1, 2 and 4 was observed (P<0.05). FASN activates ErbB1, 2 and 4, and their dimers, which are polymerized via the microstructural domain of the cell membrane. This may initiate EMT and consequentlyincrease the invasion and migration of cancer cells. However, ErbB3 may also affect tumor progression via a FASN-independent pathway.

STAT3 signaling mediates tumour resistance to EGFR targeted therapeutics

Several EGFR inhibitors are currently undergoing clinical assessment or are approved for the clinical management of patients with varying tumour types. However, treatment often results in a lack of response in many patients. The majority of patients that initially respond eventually present with tumours that display acquired resistance to the original therapy. A large number of receptor tyrosine and intracellular kinases have been implicated in driving signaling that mediates this tumour resistance to anti-EGFR targeted therapy, and in a few cases these discoveries have led to overall changes in prospective tumour screening and clinical practice (K-RAS in mCRC and EGFR T790M in NSCLC). In this mini-review, we specifically focus on the role of the STAT3 signaling axis in providing both intrinsic and acquired resistance to inhibitors of the EGFR. We also focus on STAT3 pathway targeting in an attempt to overcome resistance to anti-EGFR therapeutics.

Inhibition of Hes1 enhances lapatinib sensitivity in gastric cancer sphere-forming cells

It has been considered that the neurogenic locus notch homolog protein (Notch) signaling pathway serves an essential role in cellular differentiation, proliferation and apoptosis. However, the function of the Notch signaling pathway in gastric cancer stem cells (GCSCs) and epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) sensitivity remains unclear. The present study aimed to delineate the role of the Notch1 signaling pathway in GCSCs and lapatinib sensitivity. Sphere-forming cells were separated from human gastric cancer MKN45 parental cells. The sphere-forming cells exhibited characteristics of CSCs and higher Notch1 expression compared with that of parental cells. To investigate the role of the Notch1 signaling pathway in GCSCs, the expression of transcription factor Hes1 (Hes1) was knocked down using small interfering RNA against Hes1. It was observed that Hes1 expression was significantly downregulated in knocked down cells. The inhibition of Hes1 suppressed the properties of CSCs, as indicated by significant decreases in the expression of the transcription factor sex determining region Y-box 2, epithelial cell adhesion molecule and the homeobox protein Nanog and reduced spheroid colony formation. In addition, epithelial-mesenchymal transition was significantly impaired in sphere-forming cells following Hes1 knockdown. Furthermore, the inhibition of Hes1 effectively enhanced lapatinib sensitivity in sphere-forming cells. These results suggest that sphere-forming gastric cancer cells possess the characteristics of CSCs, and that the Notch1 signaling pathway serves an essential role in the maintenance of CSCs and lapatinib sensitivity.

Autocrine mechanisms of cancer chemoresistance

An ever-increasing number of studies highlight the role of cancer secretome in the modification of tumour microenvironment and in the acquisition of cancer cell resistance to therapeutic drugs. The knowledge of the mechanisms underlying the relationship between cancer cell-secreted factors and chemoresistance is becoming fundamental for the identification of novel anticancer therapeutic strategies overcoming drug resistance and novel prognostic secreted biomarkers. In this review, we summarize the novel findings concerning the regulation of secreted molecules by cancer cells compromising drug sensitivity. In particular, we highlight data from available literature describing the involvement of cancer cell-secreted molecules determining chemoresistance in an autocrine manner, including: i) growth factors; ii) glycoproteins; iii) inflammatory cytokines; iv) enzymes and chaperones; and v) tumor-derived exosomes.

Molecular and hydrodynamic properties of human epidermal growth factor receptor HER2 extracellular domain and its homodimer: Experiments and multi-scale simulations

BACKGROUND

In a broad range of human carcinomas gene amplification leads to HER2 overexpression, which has been proposed to cause spontaneous dimerization and activation in the absence of ligand. This makes HER2 attractive as a therapeutic target. However, the HER2 homodimerization mechanism remains unexplored. It has been suggested that the "back-to-back" homodimer does not form in solution. Notwithstanding, very recently the crystal structure of the HER2 extracellular domain homodimer formed with a "back-to-head" interaction has been resolved. We intend to explore the existence of such interactions.

METHODS

A combination of experiments, molecular dynamics and hydrodynamic modeling were used to monitor the transport properties of HER2 in solution.

RESULTS & CONCLUSIONS

We have detected the HER2 extracellular domain homodimer in solution. The results show a high degree of molecular flexibility, which ultimately leads to quite higher values of the intrinsic viscosity and lower values of diffusion coefficient than those corresponding to globular proteins. This flexibility obeys to the open conformation of the receptor and to the large fluctuations of the different domains. We also report that for obtaining the correct hydrodynamic constants from the modeling one must consider the glycosylation of the systems.

GENERAL SIGNIFICANCE

Conformational features of epidermal growth factor receptors regulate their hydrodynamic properties and control their activity. It is essential to understand the dynamics of these systems and the role of the specific domains involved. To find biophysical correlations between dynamics and macroscopic transport properties is of general interest for researches working in this area. This article is part of a Special Issue entitled "Biochemistry of Synthetic Biology - Recent Developments" Guest Editor: Dr. Ilka Heinemann and Dr. Patrick O'Donoghue.

Long-term influence of sialoadenectomy on the liver of male albino rat

Epidermal growth factor is an endocrine product of the submandibular gland; the liver is an important target of its action and is affected by sialoadenectomy. Thirty rats were used in this study and divided into group I (sham-operated animals), group II (sialoadenectomy after 4 weeks), and group III (sialoadenectomy after 10 weeks). Liver samples were processed for light and electron microscope examination. Sialoadenectomy induced mild-to-moderate liver damage which persists up to 10 weeks after the operation. This damage is manifested morphologically rather than functionally, affecting the general structure, hepatocytes, hepatic stellate cells, and hepatic sinusoids.

ErbB-2 nuclear function in breast cancer growth, metastasis and resistance to therapy

Approximately 15-20% of breast cancers (BC) show either membrane overexpression of ErbB-2 (MErbB-2), a member of the ErbBs family of receptor tyrosine kinases, or ERBB2 gene amplification. Until the development of MErbB-2-targeted therapies, this BC subtype, called ErbB-2-positive, was associated with increased metastatic potential and poor prognosis. Although these therapies have significantly improved overall survival and cure rates, resistance to available drugs is still a major clinical issue. In its classical mechanism, MErbB-2 activates downstream signaling cascades, which transduce its effects in BC. The fact that ErbB-2 is also present in the nucleus of BC cells was discovered over twenty years ago. Also, compelling evidence revealed a non-canonical function of nuclear ErbB-2 as a transcriptional regulator. As a deeper understanding of nuclear ErbB-2 actions would be crucial to the disclosure of its role as a biomarker and a target of therapy in BC, we will here review its function in BC, in particular, its role in growth, metastatic spreading and response to currently available MErbB-2-positive BC therapies.

The Evolution of Oncology Companion Diagnostics from Signal Transduction to Immuno-Oncology

Sixteen oncology drugs have been approved with a companion diagnostic (CDx) test by the FDA. These represent only 9.6% of the 167 oncology drug approvals since 1998, the year the first CDx test for Herceptin was approved. The great majority of CDx tests are for drugs that inhibit signal transduction pathways by either inhibiting the intracellular kinase activity with a small molecule or preventing ligand-induced receptor activation with a monoclonal antibody. In most of these cases, prospective patient selection for the biomarker-positive subpopulation was initiated in or before Phase II. The development of CDx tests for emerging immunotherapies will be more complicated because they are not dependent on driver mutations in the drug target, the mechanism of action is often pleiotropic, and will require both protein and cell-based assays to evaluate the interaction of the tumor with the immune system. Consequently, we will need to develop new biomarker strategies for the development of immunotherapies and to determine whether the optimum strategy is to release a prior checkpoint blockade in patients with a suppressed immune response, or to prime a new immune response to the tumor.

Epidermal Growth Factor Induces Proliferation of Hair Follicle-Derived Mesenchymal Stem Cells Through Epidermal Growth Factor Receptor-Mediated Activation of ERK and AKT Signaling Pathways Associated with Upregulation of Cyclin D1 and Downregulation of p16

The maintenance of highly proliferative capacity and full differentiation potential is a necessary step in the initiation of stem cell-based regenerative medicine. Our recent study showed that epidermal growth factor (EGF) significantly enhanced hair follicle-derived mesenchymal stem cell (HF-MSC) proliferation while maintaining the multilineage differentiation potentials. However, the underlying mechanism remains unclear. Herein, we investigated the role of EGF in HF-MSC proliferation. HF-MSCs were isolated and cultured with or without EGF. Immunofluorescence staining, flow cytometry, cytochemistry, and western blotting were used to assess proliferation, cell signaling pathways related to the EGF receptor (EGFR), and cell cycle progression. HF-MSCs exhibited surface markers of mesenchymal stem cells and displayed trilineage differentiation potentials toward adipocytes, chondrocytes, and osteoblasts. EGF significantly increased HF-MSC proliferation as well as EGFR, ERK1/2, and AKT phosphorylation (p-EGFR, p-ERK1/2, and p-AKT) in a time- and dose-dependent manner, but not STAT3 phosphorylation. EGFR inhibitor (AG1478), PI3K-AKT inhibitor (LY294002), ERK inhibitor (U0126), and STAT3 inhibitor (STA-21) significantly blocked EGF-induced HF-MSC proliferation. Moreover, AG1478, LY294002, and U0126 significantly decreased p-EGFR, p-AKT, and p-ERK1/2 expression. EGF shifted HF-MSCs at the G1 phase to the S and G2 phase. Concomitantly, cyclinD1, phosphorylated Rb, and E2F1expression increased, while that of p16 decreased. In conclusion, EGF induces HF-MSC proliferation through the EGFR/ERK and AKT pathways, but not through STAT-3. The G1/S transition was stimulated by upregulation of cyclinD1 and inhibition of p16 expression.

L-Tyrosine Confers Residualizing Properties to a d-Amino Acid-Rich Residualizing Peptide for Radioiodination of Internalizing Antibodies

PURPOSE

The aims of the study were to develop and evaluate a novel residualizing peptide for labeling internalizing antibodies with (124)I to support clinical development using immuno-positron emission tomography (PET).

METHODS

The anti-epidermal growth factor receptor antibody ch806 was radiolabeled directly or indirectly with isotopes and various residualizing peptides. Azido-derivatized radiolabeled peptides were conjugated to dibenzylcyclooctyne-derivatized ch806 antibody via click chemistry. The radiochemical purities, antigen-expressing U87MG.de2-7 human glioblastoma cell-binding properties, and targeting of xenografts at 72 hours post injection of all radioconjugates were compared. Biodistribution of (124)I-PEG4-tptddYddtpt-ch806 and immuno-PET imaging were evaluated in tumor-bearing mice.

RESULTS

Biodistribution studies using xenografts at 72 hours post injection showed that (131)I-PEG4-tptddYddtpt-ch806 tumor uptake was similar to (111)In-CHX-A″-DTPA-ch806. (125)I-PEG4-tptddyddtpt-ch806 showed a lower tumor uptake value but higher than directly labeled (125)I-ch806. (124)I-PEG4-tptddYddtpt-ch806 was produced at 23% labeling efficiency, 98% radiochemical purity, 25.9 MBq/mg specific activity, and 64% cell binding in the presence of antigen excess. Tumor uptake for (124)I-PEG4-tptddYddtpt-ch806 was similar to (111)In-CHX-A″-DTPA-ch806. High-resolution immuno-PET/magnetic resonance imaging of tumors showed good correlation with biodistribution data.

CONCLUSIONS

The mixed d/l-enantiomeric peptide, dThr-dPro-dThr-dAsp-dAsp-Tyr-dAsp-dAsp-dThr-dPro-dThr, is suitable for radiolabeling antibodies with radiohalogens such as (124)I for high-resolution immuno-PET imaging of tumors and for evaluation in early-phase clinical trials.

Hesperetin and Naringenin sensitize HER2 positive cancer cells to death by serving as HER2 Tyrosine Kinase inhibitors

AIM

Aberrant human epidermal growth factor receptor-2 (HER2) expression and constitutive mutant activation of its tyrosine kinase domain account for tumor aggression and therapy resistance in many types of cancers with major share in breast cancer cases. HER2 specific treatment modalities still face challenges owing to the side effects and acquired resistance of available therapeutics. Recently, the anti-proliferative and pro-apoptotic potential of phytochemicals, especially of flavonoids have become increasingly appreciated as powerful chemo preventive agents. Consequently, the major goal of our study is to identify flavonoids capable of inhibiting HER2 Tyrosine Kinase (HER2-TK) activity and validate their anti-tumor activity against HER2 positive tumors.

MAIN METHODS

Molecular docking studies for identifying flavonoids binding at HER2 kinase domain, ADP-Glo™ Kinase Assay for determining kinase activity, MTT assay to measure growth inhibition, various apoptotic assays and cell cycle analysis by FACS were performed.

KEY FINDINGS

Among the flavonoids screened, Naringenin (NG) and Hesperetin (HP) possessed high glide scores from molecular docking studies of enzyme-inhibitor mode. The interaction analysis revealed their ability to establish stable and strong interaction at the ATP binding site of HER2-TK. These compounds also inhibited in vitro HER2-TK activity suggesting their role as HER2 inhibitors. The study also unraveled the anti-proliferative, pro-apoptotic and anti-cancerous activity of these flavonoids against HER2 positive breast cancer cell line.

SIGNIFICANCE

The study identified two citrus fruit flavonoids, NG and HP as HER2-TK inhibitors and this is the first report on their potential to target preferentially and sensitize HER2 positive cancer cells to cell death.

EGFR regulates the development and microarchitecture of intratumoral angiogenic vasculature capable of sustaining cancer cell intravasation

Many malignant characteristics of cancer cells are regulated through pathways induced by the tyrosine kinase activity of the epidermal growth factor receptor (EGFR). Herein, we show that besides directly affecting the biology of cancer cells per se, EGFR also regulates the primary tumor microenvironment. Specifically, our findings demonstrate that both the expression and signaling activity of EGFR are required for the induction of a distinct intratumoral vasculature capable of sustaining tumor cell intravasation, a critical rate-limiting step in the metastatic cascade. An intravasation-sustaining mode of intratumoral angiogenic vessels depends on high levels of tumor cell EGFR and the interplay between EGFR-regulated production of interleukin 8 by tumor cells, interleukin-8–induced influx of tumor-infiltrating neutrophils delivering their unique matrix metalloproteinase-9, and neutrophil matrix metalloproteinase-9–dependent release of the vascular permeability and endothelial growth factor, VEGF. Our data indicate that through VEGF-mediated disruption of endothelial layer integrity and increase of intratumoral vasculature permeability, EGFR activity significantly facilitates active intravasation of cancer cells. Therefore, this study unraveled an important but overlooked function of EGFR in cancer, namely, its ability to create an intravasation-sustaining microenvironment within the developing primary tumor by orchestrating several interrelated processes required for the initial steps of cancer metastasis through vascular routes. Our findings also suggest that EGFR-targeted therapies might be more effective when implemented in cancer patients with early-staged primary tumors containing a VEGF-dependent angiogenic vasculature. Accordingly, early EGFR inhibition combined with various anti-VEGF approaches could synergistically suppress tumor cell intravasation through inhibiting the highly permeable angiogenic vasculature induced by EGFR-overexpressing aggressive cancer cells.

Weak binding to E3 ubiquitin ligase c-Cbl increases EGFRvA protein stability

Recently, we have identified a novel epidermal growth factor receptor isoform (EGFRvA), which has higher tumor-promoting capacity than EGFR. However, the underlying mechanism is not well understood. Here, we demonstrate that EGFRvA is more stable than EGFR. Interestingly, we observe that EGFRvA binds less to E3 ubiquitin ligase c-Cbl than EGFR does, although Y1045, a direct binding site of c-Cbl, is well phosphorylated in both of them. Further study reveals that EGFRvA cannot bind to Grb2, an important binding mediator between EGFR and c-Cbl. Thus, our study finds that EGFRvA is more stable than EGFR because of its decreased binding to c-Cbl.

Emerging anti-cancer antibodies and combination therapies targeting HER3/ERBB3

Cancer progression depends on stepwise accumulation of oncogenic mutations and a select group of growth factors essential for tumor growth, metastasis and angiogenesis. Agents blocking the epidermal growth factor receptor (EGFR, also called HER1 and ERBB1) and the co-receptor called HER2/ERBB2 have been approved over the last decade as anti-cancer drugs. Because the catalytically defective member of the family, HER3/ERBB3, plays critical roles in emergence of resistance of carcinomas to various drugs, current efforts focus on antibodies and other anti-HER3/ERBB3 agents, which we review herein with an emphasis on drug combinations and some unique biochemical features of HER3/ERBB3.

ABT-414, an Antibody-Drug Conjugate Targeting a Tumor-Selective EGFR Epitope

Targeting tumor-overexpressed EGFR with an antibody-drug conjugate (ADC) is an attractive therapeutic strategy; however, normal tissue expression represents a significant toxicity risk. The anti-EGFR antibody ABT-806 targets a unique tumor-specific epitope and exhibits minimal reactivity to EGFR in normal tissue, suggesting its suitability for the development of an ADC. We describe the binding properties and preclinical activity of ABT-414, an ABT-806 monomethyl auristatin F conjugate. In vitro, ABT-414 selectively kills tumor cells overexpressing wild-type or mutant forms of EGFR. ABT-414 inhibits the growth of xenograft tumors with high EGFR expression and causes complete regressions and cures in the most sensitive models. Tumor growth inhibition is also observed in tumor models with EGFR mutations, including activating mutations and those with the exon 2-7 deletion [EGFR variant III (EGFRvIII)], commonly found in glioblastoma multiforme. ABT-414 exhibits potent cytotoxicity against glioblastoma multiforme patient-derived xenograft models expressing either wild-type EGFR or EGFRvIII, with sustained regressions and cures observed at clinically relevant doses. ABT-414 also combines with standard-of-care treatment of radiation and temozolomide, providing significant therapeutic benefit in a glioblastoma multiforme xenograft model. On the basis of these results, ABT-414 has advanced to phase I/II clinical trials, and objective responses have been observed in patients with both amplified wild-type and EGFRvIII-expressing tumors. Mol Cancer Ther; 15(4); 661-9. ©2016 AACR.

miRNAs and resistance to EGFR-TKIs in EGFR-mutant non-small cell lung cancer: beyond 'traditional mechanisms' of resistance

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) have dramatically changed the prognosis of advanced non-small cell lung cancers (NSCLCs) that harbour specific EGFR activating mutations. However, the efficacy of an EGFR-TKI is limited by the onset of acquired resistance, usually within one year, in virtually all treated patients. Moreover, a small percentage of EGFR-mutant NSCLCs do not respond to an EGFR-TKI, thus displaying primary resistance. At the present time, several mechanisms of either primary and acquired resistance have been elucidated, and new drugs are currently under preclinical and clinical development in order to overcome resistance to treatment. Nevertheless, there still remains much to be thoroughly investigated, as so far research has mainly focused on the role of proteincoding genes involved in resistance to EGFR-TKIs. On the other hand, in line with the data underscoring the relevance of non-coding RNAs in the pathogenesis of lung cancer and modulation of response to systemic therapies, microRNAs (miRNAs) have been supposed to play an important role in resistance to EGFR-TKIs. The aim of this review is to briefly summarise the existing relationship between miRNAs and resistance to EGFR-TKIs, and also focusing on the possible clinical applications of miRNAs in reverting and overcoming such resistance.

What common biomarkers characterize a triple-negative profile in breast cancer?

Triple-negative breast cancers are not a homogeneous subgroup. There is substantial intra-subgroup diversity in tumor biology, prognosis and treatment sensitivity. Then, these triple-negative phenotype (TNP) groups, having specific features, can be again divided into subclasses based on an added immunohistochemical markers. The challenge in treating TNP breast cancers is that they are not responsive to antiestrogens or trastuzumab secondary to negative receptor status, and as a result have a poor prognosis. Therefore, the presence or absence of supplementary markers could help predict which therapies are best suited for patients based on the pattern that their disease markers show. In this review, we will recapitulate the major supplementary biomarkers related to triple-negative breast cancer, which could give new therapeutic options.

Identifying novel hypoxia-associated markers of chemoresistance in ovarian cancer

Background

Ovarian cancer is associated with poor long-term survival due to late diagnosis and development of chemoresistance. Tumour hypoxia is associated with many features of tumour aggressiveness including increased cellular proliferation, inhibition of apoptosis, increased invasion and metastasis, and chemoresistance, mostly mediated through hypoxia-inducible factor (HIF)-1α. While HIF-1α has been associated with platinum resistance in a variety of cancers, including ovarian, relatively little is known about the importance of the duration of hypoxia. Similarly, the gene pathways activated in ovarian cancer which cause chemoresistance as a result of hypoxia are poorly understood. This study aimed to firstly investigate the effect of hypoxia duration on resistance to cisplatin in an ovarian cancer chemoresistance cell line model and to identify genes whose expression was associated with hypoxia-induced chemoresistance.

Methods

Cisplatin-sensitive (A2780) and cisplatin-resistant (A2780cis) ovarian cancer cell lines were exposed to various combinations of hypoxia and/or chemotherapeutic drugs as part of a ‘hypoxia matrix’ designed to cover clinically relevant scenarios in terms of tumour hypoxia. Response to cisplatin was measured by the MTT assay. RNA was extracted from cells treated as part of the hypoxia matrix and interrogated on Affymetrix Human Gene ST 1.0 arrays. Differential gene expression analysis was performed for cells exposed to hypoxia and/or cisplatin. From this, four potential markers of chemoresistance were selected for evaluation in a cohort of ovarian tumour samples by RT-PCR.

Results

Hypoxia increased resistance to cisplatin in A2780 and A2780cis cells. A plethora of genes were differentially expressed in cells exposed to hypoxia and cisplatin which could be associated with chemoresistance. In ovarian tumour samples, we found trends for upregulation of ANGPTL4 in partial responders and down-regulation in non-responders compared with responders to chemotherapy; down-regulation of HER3 in partial and non-responders compared to responders; and down-regulation of HIF-1α in non-responders compared with responders.

Conclusion

This study has further characterized the relationship between hypoxia and chemoresistance in an ovarian cancer model. We have also identified many potential biomarkers of hypoxia and platinum resistance and provided an initial validation of a subset of these markers in ovarian cancer tissues.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1539-8) contains supplementary material, which is available to authorized users.

Deregulation of the EGFR/PI3K/PTEN/Akt/mTORC1 pathway in breast cancer: possibilities for therapeutic intervention

The EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance and metastasis. The expression of this pathway is frequently altered in breast cancer due to mutations at or aberrant expression of: HER2, ERalpha, BRCA1, BRCA2, EGFR1, PIK3CA, PTEN, TP53, RB as well as other oncogenes and tumor suppressor genes. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway and upstream HER2 has been associated with breast cancer initiating cells (CICs) and in some cases resistance to treatment. The anti-diabetes drug metformin can suppress the growth of breast CICs and herceptin-resistant HER2+ cells. This review will discuss the importance of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway primarily in breast cancer but will also include relevant examples from other cancer types. The targeting of this pathway will be discussed as well as clinical trials with novel small molecule inhibitors. The targeting of the hormone receptor, HER2 and EGFR1 in breast cancer will be reviewed in association with suppression of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway.

Mechanochemical stimulation of MCF7 cells with rod-shaped Fe-Au Janus particles induces cell death through paradoxical hyperactivation of ERK

Multifunctional nanoparticles that actively target-specific tissues are studied for cancer diagnosis and treatment. Magnetically and optically active particles are of particular interest because they enable multiple imaging modalities and physically modulated therapies, such as magnetic hyperthermia. Fe-Au nanorods are synthesized that have a long iron segment, coated with polyethylene glycol, and a short gold tip functionalized with heregulin (HRG), a known ligand of ErbB family of receptors. HRG-nanorods preferentially target MCF7 cells relative to MDA-MB-231 cells, as demonstrated in a novel microfluidics device. Targeting rates of these classical breast cancer cells correlate with their differential expression of ErbB2/3 receptors. HRG-nanorod binding stimulates the extracellular signal-regulated kinase 1/2 (ERK) phosphorylation in MCF7 cells. The increase in ERK phosphorylation is linked to "active zones," dynamic regions in the cell periphery, which exhibit higher rates of particle binding than the rest of the cell. Periodically stretching cells using magnetic tweezers further activates ERK, which leads to cell death in cells co-treated with B-Raf inhibitors, through ERK hyperactivation. Although to a lesser extent, cell death is also achieved through magnetic hyperthermia. These results demonstrate nanoscale targeting and localized mechanochemical treatment of specific cancer cell lines based on their receptor expression using multifunctional nanoparticles.

Toward a magic or imaginary bullet? Ligands for drug targeting to cancer cells: principles, hopes, and challenges

There are many problems directly correlated with the systemic administration of drugs and how they reach their target site. Targeting promises to be a hopeful strategy as an improved means of drug delivery, with reduced toxicity and minimal adverse side effects. Targeting exploits the high affinity of cell-surface-targeted ligands, either directly or as carriers for a drug, for specific retention and uptake by the targeted diseased cells. One of the most important parameters which should be taken into consideration in the selection of an appropriate ligand for targeting is the binding affinity (K D). In this review we focus on the importance of binding affinities of monoclonal antibodies, antibody derivatives, peptides, aptamers, DARPins, and small targeting molecules in the process of selection of the most suitable ligand for targeting of nanoparticles. In order to provide a critical comparison between these various options, we have also assessed each technology format across a range of parameters such as molecular size, immunogenicity, costs of production, clinical profiles, and examples of the level of selectivity and toxicity of each. Wherever possible, we have also assessed how incorporating such a targeted approach compares with, or is superior to, original treatments.

Examination of HER3 targeting in cancer using monoclonal antibodies

The human EGF receptor (HER/EGFR) family of receptor tyrosine kinases serves as a key target for cancer therapy. Specifically, EGFR and HER2 have been repeatedly targeted because of their genetic aberrations in tumors. The therapeutic potential of targeting HER3 has long been underestimated, due to relatively low expression in tumors and impaired kinase activity. Nevertheless, in addition to serving as a dimerization partner of EGFR and HER2, HER3 acts as a key player in tumor cells' ability to acquire resistance to cancer drugs. In this study, we generated several monoclonal antibodies to HER3. Comparisons of their ability to degrade HER3, decrease downstream signaling, and inhibit growth of cultured cells, as well as recruit immune effector cells, selected an antibody that later emerged as the most potent inhibitor of pancreatic cancer cells grown as tumors in animals. Our data predict that anti-HER3 antibodies able to intercept autocrine and stroma-tumor interactions might strongly inhibit tumor growth, in analogy to the mechanism of action of anti-EGFR antibodies routinely used now to treat colorectal cancer patients.