EGFR Family Members Research Articles

Structural biology of HER2/ERBB2 dimerization: mechanistic insights and differential roles in healthy versus cancerous cells

Aim: Present study was done to understand the dimerization of HER2/ERBB2 in normal and cancer cells using in-silico study. Methods: Pathway analysis was done using Reactome. Structure of HER2/ERBB2 protein was obtained from PDB database, and using Schrödinger software protein structure was analysed and dimerization was done. Results: In normal cells, HER2/ERBB2 is present at low levels and forms a stable complex with HSP90 (heat shock protein 90), CDC37 (cell division cycle 37), and ERBIN (an adaptor protein of the HER2/ERBB2 receptor). HER2/ERBB2 lacks a ligand-binding site, so it cannot bind ligands to activate HER2/ERBB2 signaling directly. Instead, it heterodimerizes with other EGFR family members, using their ligand-binding sites to activate cell proliferation signaling cascades. In cancer, overexpression of HER2/ERBB2 leads to ligand-independent activation of signaling through dimerization. During this process, HER2/ERBB2 dissociates from the HSP90 complex. Normally, HSP90 helps to correct misfolded and aggregated proteins, but it fails to correct mutated HER2/ERBB2 in cancer cells. Conclusions: This discussion focuses on the structural changes that HER2/ERBB2 undergoes, particularly in the form of homodimers, under normal and cancerous conditions. This analysis highlights the mutated state of HER2/ERBB2 and the role of HSP90 in this context. Notably, a single-point mutation outside a protein’s active site can significantly alter its structure. This is a critical consideration in drug discovery, underscoring the need to evaluate the entire protein conformation during simulations.

New oxadiazole and pyrazoline derivatives as anti-proliferative agents targeting EGFR-TK: design, synthesis, biological evaluation and molecular docking study

Two new series of oxadiazole and pyrazoline derivatives were designed and synthesized as promising EGFR-TK inhibitors. The in vitro antiproliferative activity was studied against three human cancer cell lines; HCT116, HepG-2 and MCF7 using MTT assay. Compound 10c showed the most potent anticancer activity against all cancer cell lines, with IC50 range of 1.82 to 5.55 μM, while proving safe towards normal cells WI-38 (IC50 = 41.17 μM) compared to the reference drug doxorubicin (IC50 = 6.72 μM). The most active candidates 5a, 9b, 10a, 10b and 10c were further assessed for their EGFR-TK inhibition. The best of which, compounds 5a and 10b showed IC50 of 0.09 and 0.16 μM respectively compared to gefitinib (IC50 = 0.04 μM). Further investigation against other EGFR family members, showed that 5a displayed good activities against HER3 and HER4 with IC50 values 0.18 and 0.37 µM, respectively compared to gefitinib (IC50 = 0.35 and 0.58 µM, respectively). Furthermore, 5a was evaluated for cell cycle distribution and apoptotic induction on HepG-2 cells. It induced mitochondrial apoptotic pathway and increased accumulation of ROS. Molecular docking study came in agreement with the biological results. Compounds 5a and 10b showed promising drug-likeness with good physicochemical properties.

Targeting HER3 to overcome EGFR TKI resistance in NSCLC.

Receptor tyrosine kinases (RTKs) play a crucial role in cellular signaling and oncogenic progression. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) have become the standard treatment for advanced non-small cell lung cancer (NSCLC) patients with EGFR-sensitizing mutations, but resistance frequently emerges between 10 to 14 months. A significant factor in this resistance is the role of human EGFR 3 (HER3), an EGFR family member. Despite its significance, effective targeting of HER3 is still developing. This review aims to bridge this gap by deeply examining HER3's pivotal contribution to EGFR TKI resistance and spotlighting emerging HER3-centered therapeutic avenues, including monoclonal antibodies (mAbs), TKIs, and antibody-drug conjugates (ADCs). Preliminary results indicate combining HER3-specific treatments with EGFR TKIs enhances antitumor effects, leading to an increased objective response rate (ORR) and prolonged overall survival (OS) in resistant cases. Embracing HER3-targeting therapies represents a transformative approach against EGFR TKI resistance and emphasizes the importance of further research to optimize patient stratification and understand resistance mechanisms.

Abstract C150: Targeted inhibition of homologous recombination and nonhomologous end joining in diffuse intrinsic pontine gliomas to prevent tumor recurrence

Abstract Therapeutic resistance remains a major obstacle to successful clinical management of Diffuse Intrinsic Pontine Glioma (DIPG), a high-grade pediatric tumor of the brain stem. In nearly all patients, available therapies fail to prevent progression. Innovative combinatorial therapies that penetrate the blood-brain barrier and lead to long-term control of tumor growth are desperately needed. We identified mechanisms of resistance to radiotherapy, the standard of care for DIPG. Based on these findings, we rationally designed a brain-penetrant small molecule, MTX-241F, that is a highly selective inhibitor of EGFR and PI3 kinase family members, including the DNA repair protein DNA-PK. Preliminary studies demonstrate that micromolar levels of this inhibitor can be achieved in murine brain tissue and that MTX-241F exhibits promising single-agent efficacy and radiosensitizing activity in patient-derived DIPG neurospheres. Its physiochemical properties include high exposure in the brain, indicating excellent brain penetrance. Since radiotherapy results in double-strand breaks that are repaired by homologous recombination (HR) and non-homologous DNA end joining (NHEJ), we have tested the combination of MTX-241F with an inhibitor of ATM to achieve blockade of HR and NHEJ, respectively, with or without radiotherapy. When HR blockers were combined with MTX-241F and radiotherapy, synthetic lethality was observed, providing impetus to explore this combination in clinically relevant models of DIPG. Our data provide proof-of-concept evidence to support advanced development of MTX-241F for the treatment of DIPG. Future studies will be designed to inform rapid clinical translation to ultimately impact patients diagnosed with this devastating disease. Citation Format: Ivana Barravecchia, Monika Sharma, Robert Teis, Jeanette Cruz, Rachel Mumby, Elizabeth Ziemke, Carlos Espinoza, Brian Magnuson, Mats Ljungman, Carl Koschmann, Christopher Whitehead, Judith Sebolt-Leopold, Stefanie Galban. Targeted inhibition of homologous recombination and nonhomologous end joining in diffuse intrinsic pontine gliomas to prevent tumor recurrence [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C150.

DDDR-05. TARGETED INHIBITION OF DNA REPAIR AND SURVIVAL SIGNALING IN DIFFUSE INTRINSIC PONTINE GLIOMAS

Abstract Therapeutic resistance remains a major obstacle to successful clinical management of Diffuse Intrinsic Pontine Glioma (DIPG), a high-grade pediatric tumor of the brain stem. In nearly all patients, available therapies fail to prevent progression. Innovative combinatorial therapies that penetrate the blood-brain barrier and lead to long-term control of tumor growth are desperately needed. We identified mechanisms of resistance to radiotherapy, the standard of care for DIPG. Based on these findings, we rationally designed a brain-penetrant small molecule, MTX-241F, that is a highly selective inhibitor of EGFR and PI3 kinase family members, including the DNA repair protein DNA-PK. Preliminary studies demonstrate that micromolar levels of this inhibitor can be achieved in murine brain tissue and that MTX-241F exhibits promising single-agent efficacy and radiosensitizing activity in patient-derived DIPG neurospheres. Its physiochemical properties include high exposure in the brain, indicating excellent brain penetrance. Since radiotherapy results in double-strand breaks that are repaired by homologous recombination (HR) and non-homologous DNA end joining (NHEJ), we have tested the combination of MTX-241F with an inhibitor of ATM to achieve blockade of HR and NHEJ, respectively, with or without radiotherapy. When HR blockers were combined with MTX-241F and radiotherapy, synthetic lethality was observed, providing impetus to explore this combination in clinically relevant models of DIPG. Our data provide proof-of-concept evidence to support advanced development of MTX-241F for the treatment of DIPG. Future studies will be designed to inform rapid clinical translation to ultimately impact patients diagnosed with this devastating disease.

Targeting DNA Repair and Survival Signaling in Diffuse Intrinsic Pontine Gliomas to Prevent Tumor Recurrence.

Therapeutic resistance remains a major obstacle to successful clinical management of diffuse intrinsic pontine glioma (DIPG), a high-grade pediatric tumor of the brain stem. In nearly all patients, available therapies fail to prevent progression. Innovative combinatorial therapies that penetrate the blood-brain barrier and lead to long-term control of tumor growth are desperately needed. We identified mechanisms of resistance to radiotherapy, the standard of care for DIPG. On the basis of these findings, we rationally designed a brain-penetrant small molecule, MTX-241F, that is a highly selective inhibitor of EGFR and PI3 kinase family members, including the DNA repair protein DNA-PK. Preliminary studies demonstrated that micromolar levels of this inhibitor can be achieved in murine brain tissue and that MTX-241F exhibits promising single-agent efficacy and radiosensitizing activity in patient-derived DIPG neurospheres. Its physiochemical properties include high exposure in the brain, indicating excellent brain penetrance. Because radiotherapy results in double-strand breaks that are repaired by homologous recombination (HR) and non-homologous DNA end joining (NHEJ), we have tested the combination of MTX-241F with an inhibitor of Ataxia Telangiectasia Mutated to achieve blockade of HR and NHEJ, respectively, with or without radiotherapy. When HR blockers were combined with MTX-241F and radiotherapy, synthetic lethality was observed, providing impetus to explore this combination in clinically relevant models of DIPG. Our data provide proof-of-concept evidence to support advanced development of MTX-241F for the treatment of DIPG. Future studies will be designed to inform rapid clinical translation to ultimately impact patients diagnosed with this devastating disease.

Ruscogenin ameliorates dasatinib-induced intestinal barrier dysfunction via ErbB4/YAP and ROCK/MLC pathways.

Dasatinib is effective in the treatment of chronic and acute myeloid leukemia, which could cause the side effect of gastrointestinal bleeding by overdose or longtime use. Ruscogenin (RUS) from the traditional Chinese medicine Ophiopogon japonicas could protect endothelial microvascular barrier function. In this study, the therapeutic effect and underlying mechanisms of RUS were investigated on intestinal barrier dysfunction induced by dasatinib. Male C57BL/6J mice were given three doses of dasatinib (70, 140, 210mg/kg, ig) and RUS (3, 10, 30μg/kg, ip) to explore the effect of dasatinib on intestinal barrier and the intervention of RUS. It was proved that dasatinib could reduce intestinal blood flow, inhibit phosphorylation of EGFR family member v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 4 (ErbB4)/YES-associated protein (YAP) and activation of Rho-associated coiled coil-containing protein kinase (ROCK)/phosphorylation of (myosin light chain) MLC. RUS could significantly increase intestinal blood flow, improve intestinal injury, reduce Evans blue leakage and serum content of FITC-dextran 4kDa, and increase the expression of connexin (ZO-1, Occludin and VE-cadherin). Meanwhile, the in vitro effect of RUS (0.01, 0.1, 1μM) on the dysfunction of the endothelial barrier was observed in dasatinib (150nM)-pretreated HUVECs. The results showed that RUS suppressed dasatinib-induced the leakage of Evans blue, and degradation of F-actin and connexin. Furthermore, RUS could significantly increase the phosphorylation of ErbB4 at Tyr1284 site and YAP at Ser397 site, and inhibit ROCK expression and phosphorylation of MLC at Ser19 site in vivo and in vitro. In conclusion, the present research proved that RUS could suppress the side effects of dasatinib-induced intestinal barrier dysfunction by regulating ErbB4/YAP and ROCK/MLC pathways.

Abstract LB212: BCG022: A novel bispecific antibody-drug conjugate targeting HER3 and MET

Abstract HER3 is a unique EGFR family member that plays a role in both tumor progression and drug resistance. Its expression can act as a bypass mechanism for EGFR and HER2-targeted therapies, resulting in therapeutic resistance. MET has also been reported as a bypass resistance mechanism to EGFR-TKI treatment. HER3 and MET are co-expressed at high prevalence in multiple tumor types, including gastric, colorectal, breast, and non-small-cell lung cancer (NSCLC). In addition, HER3 and MET are frequently overexpressed in liver metastases from patients with colorectal cancer, indicating that targeting both proteins may provide clinical benefit. We generated fully human bispecific antibodies (bsAbs) targeting HER3 and MET with cross-species reactivity, using RenLite® mice, which contain the full human heavy chain variable domain with a common human kappa light chain to facilitate future bispecific antibody assembly. These 1+1 bsAbs have demonstrated enhanced internalization compared to the parental monoclonal antibodies in multiple cancer cell lines. These bsAbs were then conjugated with Monomethyl auristatin E (MMAE) to generate HER3 and MET-targeting bispecific ADC (BCG022) candidates. In vivo drug efficacies are being screened using cell-derived hepatocellular carcinoma (HCC) and gastric carcinoma xenografts, as well as patient-derived gastric and pancreatic xenograft models. Collectively, these results suggest that BCG022 has the potential to be a novel therapeutic option for HER3 and MET co-expressing tumors. Citation Format: Zhuolin Li, Chengzhang Shang, Xuewa Guan, Zhenyan Han, Gao An, Ellen Zhang, Qingcong Lin, Yi Yang. BCG022: A novel bispecific antibody-drug conjugate targeting HER3 and MET [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB212.

Ex Vivo Drug Testing in Patient-derived Papillary Renal Cancer Cells Reveals EGFR and the BCL2 Family as Therapeutic Targets

BackgroundImmune checkpoint inhibitors and antiangiogenic agents are used for first-line treatment of advanced papillary renal cell carcinoma (pRCC) but pRCC response rates to these therapies are low. ObjectiveTo generate and characterise a functional ex vivo model to identify novel treatment options in advanced pRCC. Design, setting, and participantsWe established patient-derived cell cultures (PDCs) from seven pRCC samples from patients and characterised them via genomic analysis and drug profiling. Outcome measurements and statistical analysisComprehensive molecular characterisation in terms of copy number analysis and whole-exome sequencing confirmed the concordance of pRCC PDCs with the original tumours. We evaluated their sensitivity to novel drugs by generating drug scores for each PDC. Results and limitationsPDCs confirmed pRCC-specific copy number variations such as gains in chromosomes 7, 16, and 17. Whole-exome sequencing revealed that PDCs retained mutations in pRCC-specific driver genes. We performed drug screening with 526 novel and oncological compounds. Whereas exposure to conventional drugs showed low efficacy, the results highlighted EGFR and BCL2 family inhibition as the most effective targets in our pRCC PDCs. ConclusionsHigh-throughput drug testing on newly established pRCC PDCs revealed that inhibition of EGFR and BCL2 family members could be a therapeutic strategy in pRCC. Patient summaryWe used a new approach to generate patient-derived cells from a specific type of kidney cancer. We showed that these cells have the same genetic background as the original tumour and can be used as models to study novel treatment options for this type of kidney cancer.

The lysosome as a novel therapeutic target of EGFR-mediated tumor inflammation.

EGFR-mediated tumors have been targeted to overcome several different malignant cancers. EGFR overexpression and mutations are directly related to the malignancy, which makes the therapy more complicated. One reason for the malignancy is the induction of AP1 followed by inflammation via IL-6 secretion. Current therapeutic strategies to overcome EGFR-mediated tumors are tyrosine kinase inhibitors (TKIs), anti-EGFR monoclonal antibodies, and the combination of these two agents with classic chemotherapy or immune checkpoint inhibitors (ICIs). Although the strategies are straightforward and have shown promising efficacy in several studies, there are still hurdles to overcoming the adverse effects and limited efficacy. This study reviews the current therapeutic strategies to target EGFR family members, how they work, and their effects and limitations. We also suggest developing novel strategies to target EGFR-mediated tumors in a novel approach. A lysosome is the main custodial staff to discard unwanted amounts of EGFR and other receptor tyrosine kinase molecules. Targeting this organelle may be a new approach to overcoming EGFR-mediated cancers.

Regulation of Signaling from the Epidermal Growth Factor Family.

The epidermal growth factor (EGF) system has allowed chemists, biologists, and clinicians to improve our understanding of cell production and cancer therapy. The discovery of EGF led to the recognition of cell surface receptors capable of controlling the proliferation and survival of cells. The detailed structures of the EGF-like ligand and the responses of their receptors (EGFR-family) has revealed the conformational and aggregation changes whereby ligands activate the intracellular kinase domains. Biophysical analysis has revealed the preformed clustering of different EGFR-family members and the processes which occur on ligand binding. Understanding these receptor activation processes and the consequential cytoplasmic signaling has allowed the development of inhibitors which are revolutionizing cancer therapy. This Review describes the recent progress in our understanding of the activation of the EGFR-family, the effects of signaling from the EGFR-family on cell proliferation, and the targeting of the EGFR-family in cancer treatment.

Abstract 3966: Targeting DNA repair and survival signaling in diffuse intrinsic pontine gliomas to prevent tumor recurrence

Abstract Therapeutic resistance remains a major obstacle in the successful clinical management of Diffuse Intrinsic Pontine Glioma (DIPG), a high-grade pediatric tumor arising in the brain stem. Currently available therapies do not prevent tumor recurrence in nearly all patients diagnosed with this devastating disease. Innovative combinatorial therapies that penetrate the blood brain barrier and effectively lead to long-term control of tumor growth are desperately needed. Using RNA sequencing, we identified mechanisms of resistance of DIPG to radiotherapy (RT) standard of care. Not surprisingly, RT leads to upregulation of DNA repair and PI3K-mTOR signaling. Our team has rationally designed a brain-penetrant small molecule that is a highly selective inhibitor of EGFR and PI3 kinase family members, including the DNA repair protein DNA-PK. This molecule, MTX-241F, developed at the University of Michigan, is an excellent candidate to target the compensatory escape mechanisms leading to radioresistance and drug evasion of DIPG. Due to achievement of micromolar levels of MTX-241F in mouse brain tissue, we anticipate that this development candidate will be highly efficacious and considerably more effective than predecessor combination therapies tested against DIPG. Preliminary studies carried out in patient derived DIPG neurospheres show that MTX-241F exhibits promising signs of single agent activity efficacy and radiosensitizing activity in the combination setting. The physiochemical properties of MTX-241F include remarkably high exposure in the brain, indicating efficient blood brain barrier penetrance. Since radiotherapy results in double strand breaks which are repaired by both homologous recombination (HR) and non-homologous DNA end joining (NHEJ), we have also tested the combination of MTX-241F with an inhibitor of ATM, to achieve blockade of HR and NHEJ, respectively in the absence or presence of radiotherapy. When the HR blockers were combined with MTX-241F and radiotherapy synthetic lethality was observed in clonogenic assays, providing impetus to explore combination of HR blockers with this novel first-in-class kinase inhibitor and radiotherapy in clinically relevant models of DIPG. In summary, our data provide proof of concept evidence to support the rapid clinical development of MTX-241F for the treatment of DIPG. Future studies have been designed to inform rapid clinical translation to ultimately impact patients diagnosed with this devastating disease. Citation Format: Monika Sharma, Rachel Mumby, Varunkumar Krishnamoorthy, Brian Magnuson, Mats Ljungman, Chris Whitehead, Judith Sebolt-Leopold, Stefanie Galban. Targeting DNA repair and survival signaling in diffuse intrinsic pontine gliomas to prevent tumor recurrence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3966.

Met\u2013HER3 crosstalk supports proliferation via MPZL3 in MET-amplified cancer cells

Receptor tyrosine kinases (RTKs) are recognized as targets of precision medicine in human cancer upon their gene amplification or constitutive activation, resulting in increased downstream signal complexity including heterotypic crosstalk with other RTKs. The Met RTK exhibits such reciprocal crosstalk with several members of the human EGFR (HER) family of RTKs when amplified in cancer cells. We show that Met signaling converges on HER3–tyrosine phosphorylation across a panel of seven MET-amplified cancer cell lines and that HER3 is required for cancer cell expansion and oncogenic capacity in vitro and in vivo. Gene expression analysis of HER3-depleted cells identified MPZL3, encoding a single-pass transmembrane protein, as HER3-dependent effector in multiple MET-amplified cancer cell lines. MPZL3 interacts with HER3 and MPZL3 loss phenocopies HER3 loss in MET-amplified cells, while MPZL3 overexpression can partially rescue proliferation upon HER3 depletion. Together, these data support an oncogenic role for a HER3–MPZL3 axis in MET-amplified cancers.

JAK-STAT core cancer pathway: An integrative cancer interactome analysis.

Through a comprehensive review and in silico analysis of reported data on STAT‐linked diseases, we analysed the communication pathways and interactome of the seven STATs in major cancer categories and proposed rational targeting approaches for therapeutic intervention to disrupt critical pathways and addictions to hyperactive JAK/STAT in neoplastic states. Although all STATs follow a similar molecular activation pathway, STAT1, STAT2, STAT4 and STAT6 exert specific biological profiles associated with a more restricted pattern of activation by cytokines. STAT3 and STAT5A as well as STAT5B have pleiotropic roles in the body and can act as critical oncogenes that promote many processes involved in cancer development. STAT1, STAT3 and STAT5 also possess tumour suppressive action in certain mutational and cancer type context. Here, we demonstrated member‐specific STAT activity in major cancer types. Through systems biology approaches, we found surprising roles for EGFR family members, sex steroid hormone receptor ESR1 interplay with oncogenic STAT function and proposed new drug targeting approaches of oncogenic STAT pathway addiction.

Role and mechanism of action of LAPTM4B in EGFR-mediated autophagy.

LAPTM4B is upregulated in the majority of types of cancer and associated with cancer cell proliferation, survival and drug resistance, as well as poor patient prognosis. LAPTM4B knockdown inhibits autophagosome maturation in the context of metabolic stress. Autophagy is a homeostatic process that degrades and recycles intracellular components in response to metabolic stress. The function of autophagy is dual, as this process can either have a tumor suppressor or an oncogenic role. EGFR serves an important role in determining the tumor-suppressive or oncogenic roles of autophagy. EGFR family members regulate autophagy through various signaling pathways, including PI3K/AKT signaling. Notably, LAPTM4B also promotes cancer cell proliferation via the PI3K/AKT signaling pathway. In addition, LAPTM4B can enhance and prolong EGFR signal transduction by blocking active EGFR intraluminal sorting and lysosomal degradation. Thus, LAPTM4B may be associated with autophagy through EGFR signaling. The present review proposed that LAPTM4B participates in regulating autophagy through the EGFR pathway.

Targeting the HER3 pseudokinase domain with small molecule inhibitors.

HER3 is a potent oncogenic growth factor receptor belonging to the human epidermal growth factor (HER/EGFR) family of receptor tyrosine kinases. In contrast to other EGFR family members, HER3 is a pseudokinase, lacking functional kinase activity. As such, efforts to develop small molecule tyrosine kinase inhibitors against this family member have been limited. In response to HER3-specific growth factors such as neuregulin (NRG, also known as heregulin or HRG), HER3 must couple with catalytically active family members, including its preferred partner HER2. Dimerization of the intracellular HER2:HER3 kinase domains is a critical part of the activation mechanism and HER3 plays a specialized role as an allosteric activator of the active HER2 kinase partner. Intriguingly, many pseudokinases retain functionally important nucleotide binding capacity, despite loss of kinase activity. We demonstrated that occupation of the nucleotide pocket of the pseudokinase HER3 retains functional importance for growth factor signaling through oncogenic HER2:HER3 heterodimers. Mutation of the HER3 nucleotide pocket both disrupts signaling and disrupts HER2:HER3 dimerization. Conversely, ATP competitive drugs which bind to HER3, but not HER2, can stabilize HER2:HER3 dimers, induce signaling and promote cell growth in breast cancer models. This indicates a nucleotide-dependent conformational role for the HER3 kinase domain. Critically, our recent proof-of-concept work demonstrated that HER3-directed small molecule inhibitors can also disrupt HER2:HER3 dimerization and signaling, supporting the prospect that HER3 can be a direct drug target despite its lack of intrinsic activity. In this chapter we will describe methods for identifying and validating small molecule inhibitors against the HER3 pseudokinase.

Characterization of recombinant \u03b2 subunit of human MUC4 mucin (rMUC4\u03b2)

MUC4 is a transmembrane mucin expressed on various epithelial surfaces, including respiratory and gastrointestinal tracts, and helps in their lubrication and protection. MUC4 is also aberrantly overexpressed in various epithelial malignancies and functionally contributes to cancer development and progression. MUC4 is putatively cleaved at the GDPH site into a mucin-like α-subunit and a membrane-tethered growth factor-like β-subunit. Due to the presence of several functional domains, the characterization of MUC4β is critical for understanding MUC4 biology. We developed a method to produce and purify multi-milligram amounts of recombinant MUC4β (rMUC4β). Purified rMUC4β was characterized by Far-UV CD and I-TASSER-based protein structure prediction analyses, and its ability to interact with cellular proteins was determined by the affinity pull-down assay. Two of the three EGF-like domains exhibited typical β-fold, while the third EGF-like domain and vWD domain were predominantly random coils. We observed that rMUC4β physically interacts with Ezrin and EGFR family members. Overall, this study describes an efficient and simple strategy for the purification of biologically-active rMUC4β that can serve as a valuable reagent for a variety of biochemical and functional studies to elucidate MUC4 function and generating domain-specific antibodies and vaccines for cancer immunotherapy.

Advances in understanding the therapeutic targeting of ErbB2 by regulating endocytic degradation

<p indent="0mm">ErbB2/HER2 belongs to the ErbB/EGFR family of receptor tyrosine kinases (RTKs), which are overexpressed in diverse cancer-types, such as breast, ovarian, gastric cancers, etc., and are frequently associated with adverse clinical outcomes. ErbB2 forms homodimers or heterodimers with EGFR family members on the plasma membrane. It can activate a series of downstream signaling pathways to promote the proliferation and survival of cancer cells. Current ErbB2-targeted therapies include monoclonal antibodies, antibody-drug conjugates, and small-molecule kinase inhibitors. However, in most cases, drug resistance seems inevitable and threatens patients’ lives. Recent advances suggest that the induced ubiquitylation and endocytic degradation of ErbB2 effectively diminish its surface presence and, thus, successfully suppress the growth of cancer cells. Herein, we briefly introduce ErbB2 and targeted therapies against this RTK before focusing on recent advances in the understanding of the dynamic regulation of its ubiquitylation and endocytic degradation. We aim to shed light on the development of novel ErbB2-targeted therapeutic strategies in the treatment of human cancers.

Identification of Immunogenic MHC Class II Human HER3 Peptides that Mediate Anti-HER3 CD4+ Th1 Responses and Potential Use as a Cancer Vaccine.

The HER3/ERBB3 receptor is an oncogenic receptor tyrosine kinase that forms heterodimers with EGFR family members and is overexpressed in numerous cancers. HER3 overexpression associates with reduced survival and acquired resistance to targeted therapies, making it a potential therapeutic target in multiple cancer types. Here, we report on immunogenic, promiscuous MHC class II-binding HER3 peptides, which can generate HER3-specific CD4+ Th1 antitumor immune responses. Using an overlapping peptide screening methodology, we identified nine MHC class II-binding HER3 epitopes that elicited specific Th1 immune response in both healthy donors and breast cancer patients. Most of these peptides were not identified by current binding algorithms. Homology assessment of amino acid sequence BLAST showed >90% sequence similarity between human and murine HER3/ERBB3 peptide sequences. HER3 peptide-pulsed dendritic cell vaccination resulted in anti-HER3 CD4+ Th1 responses that prevented tumor development, significantly delayed tumor growth in prevention models, and caused regression in multiple therapeutic models of HER3-expressing murine tumors, including mammary carcinoma and melanoma. Tumors were robustly infiltrated with CD4+ T cells, suggesting their key role in tumor rejection. Our data demonstrate that class II HER3 promiscuous peptides are effective at inducing HER3-specific CD4+ Th1 responses and suggest their applicability in immunotherapies for human HER3-overexpressing tumors.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature