Biologic therapy in esophageal and gastric malignancies: current therapies and future directions

The preclinical discovery and development of zolbetuximab for the treatment of gastric cancer

INTRODUCTION

Gastric cancer remains a formidable challenge in oncology with high mortality rates and few advancements in treatment. Claudin-18.2 (CLDN18.2) is a tight junction protein primarily expressed in the stomach and is frequently overexpressed in certain subsets of gastric cancers. Targeting CLDN18.2 with monoclonal antibodies, such as zolbetuximab (IMAB362), has shown promising efficacy results in combination with chemotherapy.

AREAS COVERED

The molecular cell biology of CLDN18.2 is discussed along with studies demonstrating the utility of CLDN18.2 expression as a biomarker and therapeutic target. Important clinical studies are reviewed, including Phase III trials, SPOTLIGHT and GLOW, which demonstrate the efficacy of zolbetuximab in combination with chemotherapy in patients with CLDN18.2-positive advanced gastric cancer.

EXPERT OPINION

CLDN18.2 is involved in gastric differentiation through maintenance of epithelial barrier function and coordination of signaling pathways, and its expression in gastric cancers reflects a 'gastric differentiation' program. Targeting Claudin-18.2 represents the first gastric cancer specific 'targeted' treatment. Further studies are needed to determine its role within current gastric cancer treatment sequencing, including HER2-targeted therapies and immunotherapies. Management strategies will also be needed to better mitigate zolbetuximab-related treatment side effects, including gastrointestinal (GI) toxicities.

Therapeutic implications of signaling pathways and tumor microenvironment interactions in esophageal cancer

Esophageal cancer (EC) is significantly influenced by the tumor microenvironment (TME) and altered signaling pathways. Downregulating these pathways in EC is essential for suppressing tumor development, preventing metastasis, and enhancing therapeutic outcomes. This approach can increase tumor sensitivity to treatments, enhance patient outcomes, and inhibit cancer cell proliferation and spread. The TME, comprising cellular and non-cellular elements surrounding the tumor, significantly influences EC's development, course, and treatment responsiveness. Understanding the complex relationships within the TME is crucial for developing successful EC treatments. Immunotherapy is a vital TME treatment for EC. However, the heterogeneity within the TME limits the application of anticancer drugs outside clinical settings. Therefore, identifying reliable microenvironmental biomarkers that can detect therapeutic responses before initiating therapy is crucial. Combining approaches focusing on EC signaling pathways with TME can enhance treatment outcomes. This integrated strategy aims to interfere with essential signaling pathways promoting cancer spread while disrupting factors encouraging tumor development. Unraveling aberrant signaling pathways and TME components can lead to more focused and efficient treatment approaches, identifying specific cellular targets for treatments. Targeting the TME and signaling pathways may reduce metastasis risk by interfering with mechanisms facilitating cancer cell invasion and dissemination. In conclusion, this integrative strategy has significant potential for improving patient outcomes and advancing EC research and therapy. This review discusses the altered signaling pathways and TME in EC, focusing on potential future therapeutics.

Molecular pathogenesis, targeted therapies, and future perspectives for gastric cancer

Gastric cancer is a major source of global cancer mortality with limited treatment options and poor patient survival. As our molecular understanding of gastric cancer improves, we are now beginning to recognize that these cancers are a heterogeneous group of diseases with incredibly unique pathogeneses and active oncogenic pathways. It is this molecular diversity and oftentimes lack of common oncogenic driver mutations that bestow the poor treatment responses that oncologists often face when treating gastric cancer. In this review, we will examine the treatments for gastric cancer including up-to-date molecularly targeted therapies and immunotherapies. We will then review the molecular subtypes of gastric cancer to highlight the diversity seen in this disease. We will then shift our discussion to basic science and gastric cancer mouse models as tools to study gastric cancer molecular heterogeneity. Furthermore, we will elaborate on a molecular process termed paligenosis and the cyclical hit model as key events during gastric cancer initiation that impart nondividing mature differentiated cells the ability to re-enter the cell cycle and accumulate disparate genomic mutations during years of chronic inflammation and injury. As our basic science understanding of gastric cancer advances, so too must our translational and clinical efforts. We will end with a discussion regarding single-cell molecular analyses and cancer organoid technologies as future translational avenues to advance our understanding of gastric cancer heterogeneity and to design precision-based gastric cancer treatments. Elucidation of interpatient and intratumor heterogeneity is the only way to advance future cancer prevention, diagnoses and treatment.

Sensitivity towards HDAC inhibition is associated with RTK/MAPK pathway activation in gastric cancer

Gastric cancer ranks the fifth most common and third leading cause of cancer-related deaths worldwide. Alterations in the RTK/MAPK, WNT, cell adhesion, TP53, TGFβ, NOTCH, and NFκB signaling pathways could be identified as main oncogenic drivers. A combination of altered pathways can be associated with molecular subtypes of gastric cancer. In order to generate model systems to study the impact of different pathway alterations in a defined genetic background, we generated three murine organoid models: a RAS-activated (Kras^G12D , Tp53^R172H ), a WNT-activated (Apc^fl/fl , Tp53^R172H ), and a diffuse (Cdh1^fl/fl , Apc^fl/fl ) model. These organoid models were morphologically and phenotypically diverse, differed in proteome expression signatures and possessed individual drug sensitivities. A differential vulnerability to RTK/MAPK pathway interference based on the different mitogenic drivers and according to the level of dependence on the pathway could be uncovered. Furthermore, an association between RTK/MAPK pathway activity and susceptibility to HDAC inhibition was observed. This finding was further validated in patient-derived organoids from gastric adenocarcinoma, thus identifying a novel treatment approach for RTK/MAPK pathway altered gastric cancer patients.

Advances and challenges in the treatment of esophageal cancer

Esophageal cancer (EC) is one of the most common cancers with high morbidity and mortality rates. EC includes two histological subtypes, namely esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC). ESCC primarily occurs in East Asia, whereas EAC occurs in Western countries. The currently available treatment strategies for EC include surgery, chemotherapy, radiation therapy, molecular targeted therapy, and combinations thereof. However, the prognosis remains poor, and the overall five-year survival rate is very low. Therefore, achieving the goal of effective treatment remains challenging. In this review, we discuss the latest developments in chemotherapy and molecular targeted therapy for EC, and comprehensively analyze the application prospects and existing problems of immunotherapy. Collectively, this review aims to provide a better understanding of the currently available drugs through in-depth analysis, promote the development of new therapeutic agents, and eventually improve the treatment outcomes of patients with EC.

Molecular Pathology of Gastroesophageal Cancer

Upper gastroesophageal carcinomas consist of cancers arising from the esophagus and stomach. Squamous cell carcinomas and adenocarcinomas are seen in the esophagus and despite arising from the same organ have different biology. Gastric adenocarcinomas are categorized into 4 molecular subtypes: high Epstein-Barr virus load, microsatellite unstable cancers, chromosomal unstable (CIN) cancers, and genomically stable cancers. Genomically stable gastric cancers correlate highly with histologically defined diffuse-type cancers. Esophageal carcinomas and CIN gastric cancers often are driven by high-level amplifications of oncogenes and contain a high degree of intratumoral heterogeneity. Targeted therapeutics is an active area of research for gastroesophageal cancers.

Mitochondrial pathway of the lysine demethylase 5C inhibitor CPI-455 in the Eca-109 esophageal squamous cell carcinoma cell line

BACKGROUND

Esophageal cancer is a malignant tumor of the digestive tract that is difficult to diagnose early. CPI-455 has been reported to inhibit various cancers, but its role in esophageal squamous cell carcinoma (ESCC) is unknown.

AIM

To investigate the effects and mechanism of the lysine demethylase 5C inhibitor, CPI-455, on ESCC cells.

METHODS

A methyl tetrazolium assay was used to detect the inhibitory effect of CPI-455 on the proliferation of Eca-109 cells. Apoptosis, reactive oxygen species (ROS), and mitochondrial membrane potential were assessed by flow cytometry. Laser confocal scanning and transmission electron microscopy were used to observe changes in Eca-109 cell morphology. The protein expression of P53, Bax, lysine-specific demethylase 5C (KDM5C), cleaved Caspase-9, and cleaved Caspase-3 were assayed by western blotting.

RESULTS

Compared with the control group, CPI-455 significantly inhibited Eca-109 cell proliferation. Gemcitabine inhibited Eca-109 cell proliferation in a concentration- and time-dependent manner. CPI-455 caused extensive alteration of the mitochondria, which appeared to have become atrophied. The cell membrane was weakly stained and the cytoplasmic structures were indistinct and disorganized, with serious cavitation when viewed by transmission electron microscopy. The flow cytometry and western blot results showed that, compared with the control group, the mitochondrial membrane potential was decreased and depolarized in Eca-109 cells treated with CPI-455. CPI-455 significantly upregulated the ROS content, P53, Bax, Caspase-9, and Caspase-3 protein expression in Eca-109 cells, whereas KDM5C expression was downregulated.

CONCLUSION

CPI-455 inhibited Eca-109 cell proliferation via mitochondrial apoptosis by regulating the expression of related genes.

Tumor organoids to study gastroesophageal cancer: a primer

Gastroesophageal cancers are leading causes of cancer death. Our attempts at adopting molecularly based treatment approaches have been slow and ineffective even though we begin to identify specific targetable gene mutations and pathways. It is clear that we should no longer treat all gastroesophageal cancers as a homogeneous disease, which is what we do when we use non-specific chemotherapy. However, we currently cannot monitor successful gene/pathway targeting, nor understand how/when tumors develop resistance, nor predict which patients will derive maximal benefit. To improve outcomes, we must precisely detail the heterogeneity of these tumors to then individualize cancer therapy as well as develop novel avenues to study and predict treatment effects in individual patients. To this end, patient-derived organoids, in which tumor cells from individual patients are grown in a Petri dish, are a new versatile system that allows for timely expandability, detailed molecular characterization, and genetic manipulation with the promise of enabling predictive assessment of treatment response. In this review, we will explore the development and basic techniques for organoid generation, and discuss the current and potential future applications of this exciting technology to study the basic science of carcinogenesis and to predict/guide cancer patient care in the clinics.

Nucleolin-Sle A Glycoforms as E-Selectin Ligands and Potentially Targetable Biomarkers at the Cell Surface of Gastric Cancer Cells

BACKGROUND

Gastric cancer (GC) is a major health burden worldwide, with half of patients developing metastases within 5 years after treatment, urging novel biomarkers for diagnosis and efficient therapeutic targeting. Sialyl-Lewis A (SLeA), a terminal glycoepitope of glycoproteins and glycolipids, offers tremendous potential towards this objective. It is rarely expressed in healthy tissues and blood cells, while it is present in highly metastatic cell lines and metastases. SLeA is also involved in E-selectin mediated metastasis, making it an ideal target to control disease dissemination.

METHODS AND RESULTS

To improve cancer specificity, we have explored the SLeA-glycoproteome of six GC cell models, with emphasis on glycoproteins showing affinity for E-selectin. A novel bioinformatics-assisted algorithm identified nucleolin (NCL), a nuclear protein, as a potential targetable biomarker potentially involved in metastasis. Several immunoassays, including Western blot and in situ proximity ligation reinforced the existence of cell surface NCL-SLeA glycoforms in GC. The NCL-SLeA glycophenotype was associated with decreased survival and was not reflected in relevant healthy tissues.

CONCLUSIONS

NCL-SLeA is a biomarker of poor prognosis in GC holding potential for precise cancer targeting. This is the first report describing SLeA in preferentially nuclear protein, setting a new paradigm for cancer biomarkers discovery and targeted therapies.

Esophageal carcinoma: Towards targeted therapies

BACKGROUND

Patients with esophageal cancer are confronted with high mortality rates. Whether it is esophageal squamous cell carcinoma (ESCC) or esophageal adenocarcinoma (EAC), patients usually present at advanced stages, with treatment options traditionally involving chemotherapy in metastatic settings. With the comprehensive genomic characterization of esophageal cancers, targeted therapies are gaining interest and agents such as ramucirumab, trastuzumab and pembrolizumab are already being used for the treatment of EAC.

CONCLUSIONS

Pembrolizumab has recently been FDA-approved for PD-L1 positive, locally advanced or metastatic ESCC. Despite comprehensive molecular characterization, however, available targed therapies for ESCC are still lagging behind. Herein, we discuss current trends towards more targeted therapies in esophageal cancers, taking into consideration unique features of ESCCs and EACs. Patients progressing on standard therapies should be subjected to genomic profiling and considered for clinical trials aimed at testing targeted therapies. Future targeted therapies may include CDK4/6 inhibitors, PARP inhibitors and inhibitors targeting the NRF2 and Wnt signaling pathways. Ultimately, optimized biomarker assays and next generation sequencing platforms may allow for the identification of subcategories of ESCC and EAC patients that will benefit from selective targeted therapies and/or combinations thereof.

MicroRNA-449b-5p Suppresses Proliferation, Migration, and Invasion of Osteosarcoma by Targeting c-Met

Background

The aim of this study was to clarify the biological function of microRNA-449b-5p in the progression of osteosarcoma (OS) and to define the underlying mechanism.

Material/Methods

Relative levels of microRNA-449b-5p in OS tissues and cell lines was determined by quantitative real-time polymerase chain reaction (qRT-PCR). The correlation between microRNA-449b-5p level and pathological characteristics of OS patients was analyzed by chi-square test. Kaplan-Meier analysis was used for survival analysis of OS patients based on their expression level of microRNA-449b-5p. Regulatory effects of microRNA-449b-5p on cellular behaviors of OS cells were evaluated by cell counting kit-8 (CCK-8) and Transwell assay. The binding relationship between microRNA-449b-5p and c-Met was verified through dual-luciferase reporter gene assay, and their interaction in OS progression was further examined through a series of rescue experiments.

Results

MicroRNA-449b-5p was expressed at low levels in OS. Lower levels of microRNA-449b-5p were seen in OS tissues with worse tumor grade or histological differentiation. OS patients with low levels of microRNA-449b-5p had worse overall survival relative to those with high level of microRNA-449b-5p. Overexpression of microRNA-449b-5p markedly attenuated proliferative, migratory, and invasive abilities of OS cells. C-Met is the downstream target of microRNA-449b-5p, and its level was inhibited in OS cells overexpressing microRNA-449b-5p. Importantly, c-Met partially rescued the inhibitory effects of microRNA-449b-5p on behavior of OS cells.

Conclusions

MicroRNA-449b-5p is downregulated in OS, which alleviates the malignant progression of OS by targeting c-Met.

Cistanche tubulosa phenylethanoid glycosides induce apoptosis in Eca-109 cells via the mitochondria-dependent pathway

Cistanche tubulosa has various biological functions. In the present study, the antitumor effect of water-soluble phenylethanoid glycosides of C. tubulosa (CTPG-W) on esophageal cancer was investigated. Eca-109 cells were treated with CTPG-W and the cell viability was measured by MTT assay. The apoptosis, cell cycle, mitochondrial membrane potential (Δψm) and reactive oxygen species were analyzed by flow cytometry. The levels of proteins in apoptotic pathways were detected by western blot analysis. It was determined that CTPG-W significantly reduced the viability of Eca-109 cells through the induction of apoptosis and cell cycle arrest. Following CTPG-W treatment, the Δψm of Eca-109 was notably decreased, which is associated with the upregulated levels of B-cell lymphoma-2 (Bcl-2)-associated X and downregulated levels of Bcl-2. Consequently, the levels of cytochrome c and c-Jun NH₂-terminal kinase were increased, which upregulated the levels of cleaved-poly (ADP-ribose) polymerase and cleaved-caspase-3, −7 and −9, but not caspase-8. Correspondingly, the levels of reactive oxygen species in Eca-109 cells demonstrated notable changes. These results indicated that CTPG-W induced apoptosis of Eca-109 cells through a mitochondrial-dependent pathway.

Curcumin analog, GO-Y078, overcomes resistance to tumor angiogenesis inhibitors

Tumor angiogenesis inhibition is one of the most potent strategies in cancer chemotherapy. From past clinical studies, inhibition of the vascular endothelial growth factor pathway successfully treats malignant tumors. However, vascular endothelial growth factor inhibitors alone cannot cure tumors. Moreover, resistance to small molecule inhibitors has also been reported. Herein, we show the antiangiogenic potential of a newly synthesized curcumin analog, GO-Y078, that possibly functions through inhibition of actin stress fiber formation, resulting in mobility inhibition; this mechanism is different from that of vascular endothelial growth factor inhibition. In addition, we examined the detailed mechanism of action of the antiangiogenesis potential of GO-Y078 using human umbilical venous epithelial cells resistant to angiogenesis inhibitors (HUVEC-R). GO-Y078 inhibited the growth and mobility of HUVEC-R at 0.75 μmol/L concentration. Expression analyses by microarray and RT-PCR showed that expressions of genes including that of fibronectin 1 were significantly suppressed. Among these genes, fibronectin 1 is abundantly expressed and, therefore, seems to be a good target for GO-Y078. In a knockdown experiment using Si-oligo of fibronectin 1 (FN1), FN1 expression was decreased to half of that in mock experiments as well as GO-Y078. Knockdown of FN1 resulted in the suppression of HUVEC-R growth at 24 hours after treatment. Fibronectin is a key molecule contributing to angiogenesis that could be inhibited by GO-Y078. Thus, resistance to vascular endothelial growth factor inhibition can be overcome using GO-Y078.

Genomic profiles of primary and metastatic esophageal adenocarcinoma identified via digital sorting of pure cell populations: results from a case report

Background

We report on a female patient who underwent primary radical resection for a stage 2B Her-2-positive Barrett’s-type esophageal adenocarcinoma (EAC). Despite Her-2 targeted therapy, her disease recurred and required repeated metastectomies.

Case presentation

Digital cell sorting and targeted sequencing of cancer sub-clones from EAC and metastases revealed a completely mutated TP53, whereas the sorted stromal cells were wild-type. Her-2 amplification was significantly lower in the metastases when the patient became therapy-resistant.

Conclusions

The mechanism of therapy resistance illustrated by this case could only be detected through accurate analysis of tumor sub-populations.

Investigating tumor sub-populations of recurrent disease is important for adjusting therapy in recurrent EAC.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4789-4) contains supplementary material, which is available to authorized users.

Ricolinostat (ACY-1215) suppresses proliferation and promotes apoptosis in esophageal squamous cell carcinoma via miR-30d/PI3K/AKT/mTOR and ERK pathways

Ricolinostat (ACY-1215), a first-in-class selective HDAC6 inhibitor, exhibits antitumor effects alone or in combination with other drugs in various cancers. However, its efficacy in esophageal cancer remains unclear. In this study, we found that the high expression of HDAC6 was associated with poor prognosis in esophageal squamous cell carcinoma (ESCC) tissues. Then, we identified that ACY-1215 significantly inhibited cellular proliferation in ESCC, and caused G2/M phase arrest and apoptosis. We further demonstrated that ACY-1215 treatment reduced the expression of PI3K, P-AKT, P-mTOR, and P-ERK1/2 and increased that of Ac-H3K9 and Ac-H4K8. In addition, using miRNA microarray and bioinformatics analysis, we detected that ACY-1215 promoted miR-30d expression, and PI3K regulatory subunit 2 (PIK3R2) was a direct target of miR-30d. Anti-miR-30d partially rescued the G2/M phase arrest and apoptosis caused by ACY-1215 treatment. The reductions in PI3K, P-AKT, and P-mTOR expression were also partially reversed by miR-30d inhibitor. Furthermore, the effects of ACY-1215 inhibited ESCC proliferation were validated in a mouse xenograft model in vivo. In conclusion, our study showed that ACY-1215 suppressed proliferation and promoted apoptosis in ESCC via miR-30d/PI3K/AKT/mTOR and ERK pathways and that ACY-1215 may be a promising antitumor agent in ESCC.

Genomic markers of resistance to targeted treatments in gastric cancer: potential new treatment strategies

Gastric cancer is a highly heterogeneous disease, displaying a complex genomic landscape and an unfavorable outcome with standard therapies. Based on distinctive genomic alterations, novel targeted agents have been developed with the aim of personalizing treatments and improving patient outcome. However, a subgroup of patients is primarily treatment-resistant, and even in the initially sensitive population, secondary resistance emerges, thus limiting therapeutic benefit. In this review, we summarize the clinical data about standard targeted agents in gastric cancer, specifically anti-HER2 treatments and antivascular therapies. We also illustrate the available evidence regarding molecular mechanisms of resistance to these agents and we discuss potential strategies for new targeted treatments that could overcome such resistance.

The vanillin derivative 6-bromine-5-hydroxy-4-methoxybenzaldehyde induces aberrant mitotic progression and enhances radio-sensitivity accompanying suppression the expression of PLK1 in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the most common form of esophageal cancer in China. Since chemotherapy is the standard clinical intervention for advanced ESCC, the development of highly effective and minimal/non-toxic drugs is essential to improve the clinical outcome and prognosis of the patients. A novel derivative of vanillin, 6-bromine-5-hydroxy-4-methoxybenzaldehyde (BVAN08), has been recently reported to activate different cell death pathways in cancer cells. In this study, we demonstrate that BVAN08 exhibits a potent anti-proliferation effect on ESCC cells (TE-1 and ECA-109) by inhibiting the expression of PLK1, an important mitotic kinase. Consistent with this, BVAN08 induces mitotic arrest and chromosomal misalignment in ESCC cells. The disruption of microtubule nucleation around centrosomes is also observed in BVAN08 treated ESCC cells. Furthermore, BVAN08 enhances radio-sensitivity of ESCC cells by prolonging DNA damage repair. These findings underscore the potential value of BVAN08 in cancer therapeutics and demonstrate the underlying mechanism by which BVAN08 induces mitotic catastrophe and enhances radio-sensitivity in ESCC cells.

Angiogenic factors: role in esophageal cancer, a brief review

Esophageal cancer has an aggressive behavior with rapid tumor mass growth and frequently poor prognosis; it is known as one of the most fatal types of cancer worldwide. The identification of potential molecular markers that can predict the response to treatment and the prognosis of this cancer has been subject of a vast investigation in the recent years. Among several molecules, various angiogenic factors that are linked to the tumor development, growth, and invasion, such as VEGF, HGF, angiopoietin-2, IL-6, and TGF-B1, were investigated. In this paper, the authors sought to review the role of these angiogenic factors in prognosis and hypothesize how they can be used as a treatment target.

A Combination of SAHA and Quinacrine Is Effective in Inducing Cancer Cell Death in Upper Gastrointestinal Cancers

Purpose: We aimed to investigate the therapeutic efficacy of single agent and the combination of quinacrine and suberoylanilide hydroxamic acid (SAHA) in wt- and mut-p53 upper gastrointestinal cancer (UGC) cell models.Experimental Design: ATP-Glo, clonogenic cell survival, Annexin V, comet, DNA double-strand breaks (DSBs), qPCR, and Western blot analysis assays were utilized.Results: Using clonogenic cell survival, ATP-Glo cell viability, Annexin V, and sub-G₀ population analysis, we demonstrated that a combination of quinacrine and SAHA significantly decreased colony formation and increased cancer cell death (range, 4-20 fold) in six UGC cell models, as compared with single-agent treatments, irrespective of the p53 status (P < 0.01). The combination of quinacrine and SAHA induced high levels of DSB DNA damage (>20-fold, P < 0.01). Western blot analysis showed activation of caspases-3, 9, and γ-H2AX in all cell models. Of note, although quinacrine treatment induced expression of wt-p53 protein, the combination of quinacrine and SAHA substantially decreased the levels of both wt-P53 and mut-P53. Furthermore, cell models that were resistant to cisplatin (CDDP) or gefitinib treatments were sensitive to this combination. Tumor xenograft data confirmed that a combination of quinacrine and SAHA is more effective than a single-agent treatment in abrogating tumor growth in vivo (P < 0.01).Conclusions: Our novel findings show that the combination of quinacrine and SAHA promotes DNA damage and is effective in inducing cancer cell death, irrespective of p53 status and resistance to CDDP or gefitinib in UGC models. Clin Cancer Res; 24(8); 1905-16. ©2018 AACR.

Genomic alterations of ERBB receptors in cancer: clinical implications

The ERBB family of receptor tyrosine kinases has been implicated in carcinogenesis for over three decades with rigorous attention to EGFR and HER2. ERBB receptors, consisting of EGFR, HER2, HER3, and HER4 are part of a complicated signaling network that activates downstream signaling pathways including PI3K/AKT, Ras/Raf/MAPK, JAK/STAT and PKC. It is well established that EGFR is amplified and/or mutated in gliomas and non-small-cell lung carcinoma while HER2 is amplified and/or over-expressed in breast, gastric, ovarian, non-small cell lung carcinoma, and several other tumor types. With the advent of next generation sequencing and large scale efforts to explore the entire spectrum of genomic alterations involved in human cancer progression, it is now appreciated that somatic ERBB receptor mutations occur at relatively low frequencies across multiple tumor types. Some of these mutations may represent oncogenic driver events; clinical studies are underway to determine whether tumors harboring these alterations respond to small molecule EGFR/HER2 inhibitors. Recent evidence suggests that some somatic ERBB receptor mutations render resistance to FDA-approved EGFR and HER2 inhibitors. In this review, we focus on the landscape of genomic alterations of EGFR, HER2, HER3 and HER4 in cancer and the clinical implications for patients harboring these alterations.