MET activation mediates resistance to lapatinib inhibition of HER2-amplified gastric cancer cells

HER2-targeted therapies beyond breast cancer - an update

The receptor tyrosine-kinase HER2 (also known as ErbB2) is a well-established therapeutic target in patients with breast or gastric cancer selected on the basis of HER2 overexpression on immunohistochemistry and/or ERBB2 amplification on in situ hybridization. With advances in cancer molecular profiling and increased implementation of precision medicine approaches into oncology practice, actionable HER2 alterations in solid tumours have expanded to include ERBB2 mutations in addition to traditional HER2 overexpression and ERBB2 amplification. These various HER2 alterations can be found in solid tumour types beyond breast and gastric cancer, although few HER2-targeted therapeutic options have been established for the other tumour types. Nevertheless, during the 5 years since our previous Review on this topic was published in this journal, obvious and fruitful progress in the development of HER2-targeted therapies has been made, including new disease indications, innovative drugs with diverse mechanisms of action and novel frameworks for approval by regulatory authorities. These advances have culminated in the recent histology-agnostic approval of the anti-HER2 antibody-drug conjugate trastuzumab deruxtecan for patients with HER2-overexpressing solid tumours. In this new Review, we provide an update on the current development landscape of HER2-targeted therapies beyond breast cancer, as well as anticipated future HER2-directed treatment strategies to overcome resistance and thereby improve efficacy and patient outcomes.

Ferroptosis regulating lipid peroxidation metabolism in the occurrence and development of gastric cancer

BACKGROUND

Gastric cancer is one of the most common malignant tumors in the world, and its occurrence and development involve complex biological processes. Iron death, as a new cell death mode, has attracted wide attention in recent years. However, the regulatory mechanism of iron death in gastric cancer and its effect on lipid peroxidation metabolism remain unclear.

AIM

To explore the role of iron death in the development of gastric cancer, reveal its relationship with lipid peroxidation, and provide a new theoretical basis for revealing the molecular mechanism of the occurrence and development of gastric cancer.

METHODS

The process of iron death in gastric cancer cells was simulated by cell culture model, and the occurrence of iron death was detected by fluorescence microscopy and flow cytometry. The changes of gene expression related to iron death and lipid peroxidation metabolism were analyzed by high-throughput sequencing technology. In addition, a mouse model of gastric cancer was established, and the role of iron death in vivo was studied by histology and immunohistochemistry, and the level of lipid peroxidation was detected. These methods comprehensively and deeply reveal the regulatory mechanism of iron death on lipid peroxidation metabolism in the occurrence and development of gastric cancer.

RESULTS

Iron death was significantly activated in gastric cancer cells, and at the same time, associated lipid peroxidation levels increased significantly. Through high-throughput sequencing analysis, it was found that iron death regulated the expression of several genes related to lipid metabolism. In vivo experiments demonstrated that increased iron death in gastric cancer mice was accompanied by a significant increase in lipid peroxidation.

CONCLUSION

This study confirmed the important role of iron death in regulating lipid peroxidation metabolism in the occurrence and development of gastric cancer. The activation of iron death significantly increased lipid peroxidation levels, revealing its regulatory mechanism inside the cell.

Artemisia argyi extracts overcome lapatinib resistance via enhancing TMPRSS2 activation in HER2-positive breast cancer

Breast cancer stands as the predominant malignancy and primary cause of cancer-related mortality among females globally. Approximately 25% of breast cancers exhibit HER2 overexpression, imparting a more aggressive tumor phenotype and correlating with poor prognoses. Patients with metastatic breast cancer receiving HER2 tyrosine kinase inhibitors (HER2 TKIs), such as Lapatinib, develop acquired resistance within a year, posing a critical challenge in managing this disease. Here, we explore the potential of Artemisia argyi, a Chinese herbal medicine known for its anti-cancer properties, in mitigating HER2 TKI resistance in breast cancer. Analysis of the Cancer Genome Atlas (TCGA) revealed diminished expression of transmembrane serine protease 2 (TMPRSS2), a subfamily of membrane proteolytic enzymes, in breast cancer patients, correlating with unfavorable outcomes. Intriguingly, lapatinib-responsive patients exhibited higher TMPRSS2 expression. Our study unveiled that the compounds from Artemisia argyi, eriodictyol, and umbelliferone could inhibit the growth of lapatinib-resistant HER2-positive breast cancer cells. Mechanistically, they suppressed HER2 kinase activation by enhancing TMPRSS2 activity. Our findings propose TMPRSS2 as a critical determinant in lapatinib sensitivity, and Artemisia argyi emerges as a potential agent to overcome lapatinib via activating TMPRSS2 in HER2-positive breast cancer. This study not only unravels the molecular mechanisms driving cell death in HER2-positive breast cancer cells induced by Artemisia argyi but also lays the groundwork for developing novel inhibitors to enhance therapy outcomes.

Characterization of MET Alterations in 37 Gastroesophageal Cancer Cell Lines for MET-Targeted Therapy

Capmatinib and savolitinib, selective MET inhibitors, are widely used to treat various MET-positive cancers. In this study, we aimed to determine the effects of these inhibitors on MET-amplified gastric cancer (GC) cells. Methods: After screening 37 GC cell lines, the following cell lines were found to be MET-positive with copy number variation >10: SNU-620, ESO51, MKN-45, SNU-5, and OE33 cell lines. Next, we assessed the cytotoxic response of these cell lines to capmatinib or savolitinib alone using cell counting kit-8 and clonogenic cell survival assays. Western blotting was performed to assess the effects of capmatinib and savolitinib on the MET signaling pathway. Xenograft studies were performed to evaluate the in vivo therapeutic efficacy of savolitinib in MKN-45 cells. Savolitinib and capmatinib exerted anti-proliferative effects on MET-amplified GC cell lines in a dose-dependent manner. Savolitinib inhibited the phosphorylation of MET and downstream signaling pathways, such as the protein kinase B (AKT) and extracellular signal-regulated kinase (ERK) pathways, in MET-amplified GC cells. Additionally, savolitinib significantly decreased the number of colonies formed on the soft agar and exerted dose-dependent anti-tumor effects in an MKN-45 GC cell xenograft model. Furthermore, a combination of trastuzumab and capmatinib exhibited enhanced inhibition of AKT and ERK activation in human epidermal growth factor receptor-2 (HER2)- and MET-positive OE33 cells. Targeting MET with savolitinib and capmatinib efficiently suppressed the growth of MET-amplified GC cells. Moreover, these MET inhibitors exerted synergistic effects with trastuzumab on HER2- and MET-amplified GC cells.

HER2+ advanced gastric cancer: Current state and opportunities (Review)

Human epidermal growth factor receptor 2 (HER2)+ gastric cancer (GC) is a distinct subtype of GC, accounting for 10‑20% of all cases of GC. Although the development of the anti‑HER2 monoclonal antibody trastuzumab has markedly improved response rates and prognosis of patients with HER2+ advanced GC (AGC), drug resistance remains a considerable challenge. Therefore, dynamic monitoring of HER2 expression levels can facilitate the identification of patients who may benefit from targeted therapy. Besides trastuzumab, DS‑8201 and RC48 have been applied in the treatment of HER2+ AGC, and several novel anti‑HER2 therapies are undergoing preclinical/clinical trials. At present, combination immunotherapy with anti‑HER2 agents is used as the first‑line treatment of this disease subtype. New promising approaches such as chimeric antigen receptor T‑cell immunotherapy and cancer vaccines are also being investigated for their potential to improve clinical outcomes. The current review provides new insights that will guide the future application of anti‑HER2 therapy by summarizing research progress on targeted therapy drugs for HER2+ AGC and combination treatments.

Clinical Implication of Concurrent Amplification of MET and FGFR2 in Metastatic Gastric Cancer

BACKGROUND

c-mesenchymal epithelial transition factor receptor (c-MET) and fibroblast growth factor receptor 2 (FGFR2) amplification have been identified as factors associated with advanced stage and poor prognosis in gastric cancer (GC). While they are typically considered mutually exclusive, concurrent amplifications have been reported in a small subset of GC patients.

METHODS

in this retrospective study, we analyzed the clinical outcomes of GC patients with MET and FGFR2 amplification using the next-generation sequencing (NGS) database cohort at Samsung Medical Center, which included a total of 2119 patients between October 2019 and April 2021.

RESULTS

Of 2119 cancer patients surveyed, the number of GC patients was 614 (29.0%). Out of 614 GC patients, 39 (6.4%) had FGFR2 amplification alone, 22 (3.6%) had MET amplification, and 2 GC patients (0.3%) had concurrent FGFR2 and MET amplification. Two patients with concurrent FGFR2 and MET amplification did not respond to first-line chemotherapy. These two patients had significantly shorter overall survival (3.6 months) compared to patients with FGFR2 or MET amplification alone (13.6 months and 8.4 months, respectively) (p = 0.004). Lastly, we tested the existence of FGFR2 and MET in tumor specimens from different organ sites. Initially, the NGS was tested in a primary tumor specimen from stomach cancer, where the MET copy number was 14.1 and the FGFR2 copy number was 5.3. We confirmed that both MET and FGFR2 were highly amplified in the primary tumor using FISH (MET-CEP7 ratio = 5 and FGFR2-CEP7 ratio = 3). However, although the MET copy number was normal in peritoneal seeding using FISH, FGFR2 remained amplified using FISH (FGFR2-CEP7 ratio = 7) with high FGFR2 protein overexpression. Hence, there was intra-patient molecular heterogeneity.

CONCLUSIONS

our findings suggest that concurrent amplification of FGFR2 and MET in GC patients is associated with clinical aggressiveness and may contribute to non-responsiveness to chemotherapy or targeted therapy.

Crizotinib-based proteolysis targeting chimera suppresses gastric cancer by promoting MET degradation

As one of the common malignant cancer types, gastric cancer (GC) is known for late-stage diagnosis and poor prognosis. Overexpression of the receptor tyrosine kinase MET is associated with poor prognosis among patients with advanced stage GC. However, no MET inhibitor has been used for GC treatment. Like other tyrosine kinase inhibitors that fit the "occupancy-driven" model, current MET inhibitors are prone to acquired resistance. The emerging proteolysis targeting chimera (PROTAC) strategy could overcome such limitations through direct degradation of the target proteins. In this study, we successfully transformed the MET-targeted inhibitor crizotinib into a series of PROTACs, recruiting cereblon/cullin 4A E3 ubiquitin ligase to degrade the MET proteins. The optimized lead PROTAC (PRO-6 E) effectively eliminated MET proteins in vitro and in vivo, inhibiting proliferation and motility of MET-positive GC cells. In the MKN-45 xenograft model, PRO-6 E showed pronounced antitumor efficacy with a well-tolerated dosage regimen. These results validated PRO-6 E as the first oral PROTAC for MET-dependent GC.

Rilotumumab Resistance Acquired by Intracrine Hepatocyte Growth Factor Signaling

Drug resistance is a long-standing impediment to effective systemic cancer therapy and acquired drug resistance is a growing problem for molecularly-targeted therapeutics that otherwise have shown unprecedented successes in disease control. The hepatocyte growth factor (HGF)/Met receptor pathway signaling is frequently involved in cancer and has been a subject of targeted drug development for nearly 30 years. To anticipate and study specific resistance mechanisms associated with targeting this pathway, we engineered resistance to the HGF-neutralizing antibody rilotumumab in glioblastoma cells harboring autocrine HGF/Met signaling, a frequent abnormality of this brain cancer in humans. We found that rilotumumab resistance was acquired through an unusual mechanism comprising dramatic HGF overproduction and misfolding, endoplasmic reticulum (ER) stress-response signaling and redirected vesicular trafficking that effectively sequestered rilotumumab and misfolded HGF from native HGF and activated Met. Amplification of MET and HGF genes, with evidence of rapidly acquired intron-less, reverse-transcribed copies in DNA, was also observed. These changes enabled persistent Met pathway activation and improved cell survival under stress conditions. Point mutations in the HGF pathway or other complementary or downstream growth regulatory cascades that are frequently associated with targeted drug resistance in other prevalent cancer types were not observed. Although resistant cells were significantly more malignant, they retained sensitivity to Met kinase inhibition and acquired sensitivity to inhibition of ER stress signaling and cholesterol biosynthesis. Defining this mechanism reveals details of a rapidly acquired yet highly-orchestrated multisystem route of resistance to a selective molecularly-targeted agent and suggests strategies for early detection and effective intervention.

MET gene alterations predict poor survival following chemotherapy in patients with advanced cancer

Background: To aid in oncology drug development, we investigated MET proto-oncogene receptor tyrosine kinase gene aberrations in 2,239 oncology patients who underwent next-generation sequencing (NGS) in clinical practice. Materials and methods: From November 2019 to January 2021, 2,239 patientswith advanced solid tumors who visited oncology clinics underwent NGS. The NGS panel included >500 comprehensive NGS tests using archival tissue specimens. Programmed death-ligand 1(PD-L1) 22C3 assay results and clinical records regarding initial chemotherapy were available for 1,137 (50.8%) and 1,761 (78.7%) patients, respectively for overall survival (OS) analysis. Results: The 2,239 patients represented 37 types of cancer. The NGS panel included >500 genes, microsatellite instability status, tumor mutational burden, and fusions. The most common cancer types were colorectal (N = 702), gastric (N = 481), and sarcoma (N = 180). MET aberrations were detected in 212 patients. All MET-amplified tumors had microsatellite stable status, and 8 had a high tumor mutational burden. Of 46 patients with MET-amplified cancers, 8 had MET-positive protein expression by immunohistochemistry (2+ and 3+). MET fusion was detected in 10 patients. Partner genes of MET fusion included ST7, TFEC, LRRD1, CFTR, CAV1, PCM1, HLA-DRB1, and CAPZA2. In survival analysis, patients with amplification of MET gene fusion had shorter OS and progression-free survival (PFS) than those without. Thus, MET aberration was determined to be a factor of response to chemotherapy. Conclusion: Approximately 2.1% and 0.4% of patients with advanced solid tumors demonstrated MET gene amplification and fusion, respectively, and displayed a worse response to chemotherapy and significantly shorter OS and PFS than those without MET gene amplification or fusion.

Signaling pathways and therapeutic interventions in gastric cancer

Gastric cancer (GC) ranks fifth in global cancer diagnosis and fourth in cancer-related death. Despite tremendous progress in diagnosis and therapeutic strategies and significant improvements in patient survival, the low malignancy stage is relatively asymptomatic and many GC cases are diagnosed at advanced stages, which leads to unsatisfactory prognosis and high recurrence rates. With the recent advances in genome analysis, biomarkers have been identified that have clinical importance for GC diagnosis, treatment, and prognosis. Modern molecular classifications have uncovered the vital roles that signaling pathways, including EGFR/HER2, p53, PI3K, immune checkpoint pathways, and cell adhesion signaling molecules, play in GC tumorigenesis, progression, metastasis, and therapeutic responsiveness. These biomarkers and molecular classifications open the way for more precise diagnoses and treatments for GC patients. Nevertheless, the relative significance, temporal activation, interaction with GC risk factors, and crosstalk between these signaling pathways in GC are not well understood. Here, we review the regulatory roles of signaling pathways in GC potential biomarkers, and therapeutic targets with an emphasis on recent discoveries. Current therapies, including signaling-based and immunotherapies exploited in the past decade, and the development of treatment for GC, particularly the challenges in developing precision medications, are discussed. These advances provide a direction for the integration of clinical, molecular, and genomic profiles to improve GC diagnosis and treatments.

A multiphase contrast-enhanced CT radiomics model for prediction of human epidermal growth factor receptor 2 status in advanced gastric cancer

Background: Accurate evaluation of human epidermal growth factor receptor 2 (HER2) status is of great importance for appropriate management of advanced gastric cancer (AGC) patients. This study aims to develop and validate a CT-based radiomics model for prediction of HER2 overexpression in AGC.

Materials and Methods: Seven hundred and forty-five consecutive AGC patients (median age, 59 years; interquartile range, 52–66 years; 515 male and 230 female) were enrolled and separated into training set (n = 521) and testing set (n = 224) in this retrospective study. Radiomics features were extracted from three phases images of contrast-enhanced CT scans. A radiomics signature was built based on highly reproducible features using the least absolute shrinkage and selection operator method. Univariable and multivariable logistical regression analysis were used to establish predictive model with independent risk factors of HER2 overexpression. The predictive performance of radiomics model was assessed in the training and testing sets.

Results: The positive rate of HER2 was 15.9% and 13.8% in the training set and testing set, respectively. The positive rate of HER2 in intestinal-type GC was significantly higher than that in diffuse-type GC. The radiomics signature comprised eight robust features demonstrated good discrimination ability for HER2 overexpression in the training set (AUC = 0.84) and the testing set (AUC = 0.78). A radiomics-based model that incorporated radiomics signature and pathological type showed good discrimination and calibration in the training (AUC = 0.85) and testing (AUC = 0.84) sets.

Conclusion: The proposed radiomics model showed favorable accuracy for prediction of HER2 overexpression in AGC.

Research progress in targeted therapy and immunotherapy for gastric cancer

ABSTRACT

Gastric cancer (GC) is one of the most common malignant tumors worldwide. Its incidence ranks the 5th among all malignant tumors globally, and it is the 3rd leading cause of death among patients with cancer. Surgical treatment is the first choice in clinical practice. However, targeted therapy, immunotherapy, and other treatment methods have also become research hotspots at home and abroad with the development of individualized precision therapy in recent years, besides traditional radiotherapy and chemotherapy. At present, targeted therapy and immunotherapy are methods used for treating GC, and they have important clinical application value and prospects. This study aimed to review the research progress of targeted therapy and immunotherapy for GC, focusing on its mechanism of action and related important clinical trials, hoping to provide references for the clinical treatment of GC.

Significance of tumor heterogeneity of p-Smad2 and c-Met in HER2-positive gastric carcinoma with lymph node metastasis

Background

Tumor heterogeneity has frequently been observed in gastric cancer (GC), but the correlation between patients’ clinico-pathologic features and the tumoral heterogeneity of GC-associated molecules is unclear. We investigated the correlation between lymph node metastasis and the intra-tumoral heterogeneity of driver molecules in GC.

Materials and methods

We retrospectively analyzed the cases of 504 patients who underwent a gastrectomy at the Department of Gastroenterological Surgery, Osaka Metropolitan University and 389 cases drawn from The Cancer Genome Atlas (TCGA) data. We performed a clustering analysis based on eight cancer-associated molecules including HER2, c-Met, and p-Smad2 using the protein expression revealed by our immunohistochemical study of the patients’ and TCGA cases. We determined the correlations between HER2 expression and the other molecules based on the degree of lymph node metastasis.

Results

Immunohistochemical staining data showed that a 43 of the 504 patients with GC (8.5%) were HER2-positive. In the HER2-positive cases, the expressions of c-Met and p-Smad2 were increased in accord with the lymph-node metastatic level. The overall survival of the HER2-positive GC patients with both p-Smad2 and c-Met expression was significantly (p = 0.030) poorer than that of the patients with p-Smad2-negative and/or c-Met-negative expression. The results of the TCGA data analysis revealed that 58 of the 389 GC cases (14.9%) were ERBB2-positive. MET expression was more frequent in the N1 metastasis group than the N0 group. In the high lymph-node metastasis (N2 and N3) group, SMAD2 expression was more frequent, as was ERBB2 and MET expression.

Conclusion

p-Smad2 and c-Met signaling might play important roles in lymph node metastasis in HER2-positive GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09681-3.

Sensitizing drug-resistant cancer cells from blood using microfluidic electroporator

Direct assessment of patient samples holds unprecedented potential in the treatment of cancer. Circulating tumor cells (CTCs) in liquid biopsies are a rapidly evolving source of primary cells in the clinic and are ideal candidates for functional assays to uncover real-time tumor information in real-time. However, a lack of routines allowing direct and active interrogation of CTCs directly from liquid biopsy samples represents a bottleneck for the translational use of liquid biopsies in clinical settings. To address this, we present a workflow for using a microfluidic vortex-assisted electroporation system designed for the functional assessment of CTCs purified from blood. Validation of this approach was assessed through drug response assays on wild-type (HCC827 wt) and gefitinib-resistant (HCC827 GR6) non-small cell lung cancer (NSCLC) cells. HCC827 cells trapped within microscale vortices were electroporated to sequentially deliver drug agents into the cytosol. Electroporation conditions facilitating multi-agent delivery were characterized for both cell lines using an automatic single-cell image fluorescence intensity algorithm. HCC827 GR6 cells spiked into the blood to emulate drug-resistant CTCs were able to be collected with high purity, demonstrating the ability of the device to minimize background cell impact for downstream sensitive cell assays. Using our proposed workflow, drug agent combinations to restore gefitinib sensitivity reflected the anticipated cytotoxic response. Taken together, these results represent a microfluidics multi-drug screening panel workflow that can enable functional interrogation of patient CTCs in situ, thereby accelerating the clinical standardization of liquid biopsies.

Mesenchymal Epithelial Transition Factor (MET): A Key Player in Chemotherapy Resistance and an Emerging Target for Potentiating Cancer Immunotherapy

The MET protein is a cell surface receptor tyrosine kinase predominately expressed in epithelial cells. Upon binding of its only known ligand, hepatocyte growth factor (HGF), MET homodimerizes, phosphorylates, and stimulates intracellular signalling to drive cell proliferation. Amplification or hyperactivation of MET is frequently observed in various cancer types and it is associated with poor response to conventional and targeted chemotherapy. More recently, emerging evidence also suggests that MET/HGF signalling may play an immunosuppressive role and it could confer resistance to cancer immunotherapy. In this review, we summarized the preclinical and clinical evidence of MET's role in drug resistance to conventional chemotherapy, targeted therapy, and immunotherapy. Previous clinical trials investigating MET-targeted therapy in unselected or MET-overexpressing cancers yielded mostly unfavourable results. More recent clinical studies focusing on MET exon 14 alterations and MET amplification have produced encouraging treatment responses to MET inhibitor therapy. The translational relevance of MET inhibitor therapy to overcome drug resistance in cancer patients is discussed.

MeCP2 Increases Cisplatin Resistance in Human Gastric Cancer through the Activation of the AKT Pathway by Facilitating PDK-1 Transcription

BACKGROUND

Increasing evidence indicates that an imbalance of oncogenes is implicated in chemotherapy resistance in cancers. Methyl-CpG binding protein 2 (MeCP2), which acts as a master epigenetic regulator of various gene expressions, is involved in the carcinogenesis and progression of gastric cancer. However, whether this vital role may participates in acquired cisplatin resistance in GC remains unknown.

OBJECTIVE

This study aimed to determine whether inhibition of MeCP2 expression could sensitize DDP-resistant GC cells to DDP and to elucidate its underlying molecular mechanism.

METHODS

qRT-PCR and western blotting were used to evaluate MeCP2 expression in GC DDP-resistant GC cells. Subsequently, cell viability, colony formation, cell cycle, cell apoptosis and tumorigenicity assays were performed to explore the role of MeCP2 in vitro and in vivo. Chromatin immunoprecipitation-qPCR and luciferase reporter assays were used to identify whether 3-phosphoinositide-dependent protein kinase 1 (PDK-1) is a direct target gene of MeCP2.

RESULTS

MeCP2 was upregulated in malignant DDP-resistant cells compared to that in non-DDP-resistant GC cells or normal gastric epithelial cells. MeCP2 knockdown increased the sensitivity of DDP-resistant GC cells to DDP, resulting in reduced cell growth, G0/G1 phase arrest and increased apoptosis, wheras MeCP2 overexpression attenuated DDP sensitivity of DDP-resistant GC cells. In addition, MeCP2 knockdown enhanced DDP sensitivity in tumors in vivo. MeCP2 elevated PDK-1 expression by binding to its CpG sites in promoter regions, and inhibition of PDK-1 reversed the inductive effect of MeCP2 overexpression on DDP resistance in GC cells.

CONCLUSION

These findings indicate that silencing MeCP2 may potentiate DDP induced cell death, providing a promising therapeutic strategy for GC.

Roles of MET in human cancer

The MET proto-oncogene was first identified in osteosarcoma cells exposed to carcinogens. Although expressed in many normal cells, MET is overexpressed in many human cancers. MET is involved in the initiation and development of various human cancers and mediates proliferation, migration and invasion. Accordingly, MET has been successfully used as a biomarker for diagnosis and prognosis, survival, post-operative recurrence, risk assessment and pathologic grading, as well as a therapeutic target. In addition, recent work indicates that inhibition of MET expression and function has potential clinical benefit. This review summarizes the role, mechanism, and clinical significance of MET in the formation and development of human cancer.

Therapeutic Mechanism of Lapatinib Combined with Sulforaphane on Gastric Cancer

Background

Lapatinib is a small-molecule tyrosine kinase inhibitor that plays important roles in cell proliferation and survival. Administration of lapatinib with capecitabine is an effective treatment for HER2-positive metastatic BC. However, the effects of lapatinib on gastric cancer (GC) remain to be clear. In this study, we aimed to investigate the therapeutic effects of lapatinib combined with sulforaphane on GC and its underlying mechanisms.

Methods

SGC-7901 and lapatinib-resistant SGC-7901 cells were treated with lapatinib (0.2 μM), sulforaphane (5 μM), or their combinations. Cell viability, invasion, cycle, and apoptosis of SGC-7901 and lapatinib-resistant SGC-7901 cells were evaluated by thiazolyl blue tetrazolium bromide (MTT), Boyden chamber assay, and flow cytometer. The protein expressions of HER-2, p-HER-2, AKT, p-AKT, ERK, and p-ERK were detected by Western blotting.

Results

We observed that lapatinib combined with sulforaphane significantly decreased cell viability and inhibited cell migration of drug-sensitive and drug-resistant cells. Lapatinib sulforaphane also remarkably induced cell apoptosis with G0/G1 arrest. In addition, Western blotting revealed that the expressions of HER-2, p-HER-2, AKT, p-AKT, ERK, and p-ERK were downregulated by lapatinib-sulforaphane treatment.

Conclusion

Combination of lapatinib and sulforaphane might be a novel and promising therapeutic treatment for lapatinib-sensitive or lapatinib-resistant GC patients.

Breast Cancer Treatments: Updates and New Challenges

Breast cancer (BC) is the most frequent cancer diagnosed in women worldwide. This heterogeneous disease can be classified into four molecular subtypes (luminal A, luminal B, HER2 and triple-negative breast cancer (TNBC)) according to the expression of the estrogen receptor (ER) and the progesterone receptor (PR), and the overexpression of the human epidermal growth factor receptor 2 (HER2). Current BC treatments target these receptors (endocrine and anti-HER2 therapies) as a personalized treatment. Along with chemotherapy and radiotherapy, these therapies can have severe adverse effects and patients can develop resistance to these agents. Moreover, TNBC do not have standardized treatments. Hence, a deeper understanding of the development of new treatments that are more specific and effective in treating each BC subgroup is key. New approaches have recently emerged such as immunotherapy, conjugated antibodies, and targeting other metabolic pathways. This review summarizes current BC treatments and explores the new treatment strategies from a personalized therapy perspective and the resulting challenges.

A novel treatment strategy for lapatinib resistance in a subset of HER2-amplified gastric cancer

Background

Gastric cancer (GC) is one of the leading causes of cancer-related deaths worldwide. Human epidermal growth factor receptor 2 (HER2) amplification occurs in approximately 13–23% of all GC cases and patients with HER2 overexpression exhibit a poor prognosis. Lapatinib, a dual EGFR/HER2 tyrosine kinase inhibitor, is an effective agent to treat HER2-amplified breast cancer but it failed in gastric cancer (GC) clinical trials. However, the molecular mechanism of lapatinib resistance in HER2-amplified GC is not well studied.

Methods

We employed an unbiased, genome-scale screening with pooled CRISPR library on HER2-amplified GC cell lines to identify genes that are associated with resistance to lapatinib. To validate the candidate genes, we applied in vitro and in vivo pharmacological tests to confirm the function of the target genes.

Results

We found that loss of function of CSK or PTEN conferred lapatinib resistance in HER2-amplified GC cell lines NCI-N87 and OE19, respectively. Moreover, PI3K and MAPK signaling was significantly increased in CSK or PTEN null cells. Furthermore, in vitro and in vivo pharmacological study has shown that lapatinib resistance by the loss of function of CSK or PTEN, could be overcome by lapatinib combined with the PI3K inhibitor copanlisib and MEK inhibitor trametinib.

Conclusions

Our study suggests that loss-of-function mutations of CSK and PTEN cause lapatinib resistance by re-activating MAPK and PI3K pathways, and further proved these two pathways are druggable targets. Inhibiting the two pathways synergistically are effective to overcome lapatinib resistance in HER2-amplified GC. This study provides insights for understanding the resistant mechanism of HER2 targeted therapy and novel strategies that may ultimately overcome resistance or limited efficacy of lapatinib treatment for subset of HER2 amplified GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08283-9.

Pharmacological Basis of Breast Cancer Resistance to Therapies - An Overview

Breast cancer (BC) is a molecular heterogeneous disease and often patients with similar clinico-pathological characteristics may display different response to treatment. Cellular processes, including uncontrolled cell-cycle, constitutive activation of signalling pathways parallel to or downstream of HER2 and alterations in DNA-repair mechanisms are the main features altered in the tumor. These cellular processes play significant roles in the emergence of therapy resistance. The introduction of target therapies as well as immunotherapies has improved the management of breast cancer. Furthermore, several therapeutic options are available to overcome resistance and physicians could overcome the challenge of resistant BC using combinatorial drug strategies and incorporating novel biomarkers. Molecular profiling promises to help in refine personalized treatment decisions and catalyse the development of further strategies when resistances inevitably occur. The search for biological explanations for treatment failure helps to clarify the phenomenon and allows to incorporate new biomarkers into clinical practice that can lead to adequate solutions to overcome it. This review provides a summary of genetic and molecular aspects of resistance mechanisms to available treatments for BC patients, and its clinical implications.

Pim1 Kinase Inhibitors Exert Anti-Cancer Activity Against HER2-Positive Breast Cancer Cells Through Downregulation of HER2

The proviral integration site for moloney murine leukemia virus 1 (Pim1) is a serine/threonine kinase and able to promote cell proliferation, survival and drug resistance. Overexpression of Pim1 has been observed in many cancer types and is associated with the poor prognosis of breast cancer. However, it remains unclear whether Pim1 kinase is a potential therapeutic target for breast cancer patients. In this study, we found that Pim1 expression was strongly associated with HER2 expression and that HER2-overexpressing breast cancer cells were more sensitive to Pim1 inhibitor-induced inhibitions of cell viability and metastatic ability. Mechanistically, Pim1 inhibitor suppressed the expression of HER2 at least in part through transcriptional level. More importantly, Pim1 inhibitor overcame the resistance of breast cancer cells to HER2 tyrosine kinase inhibitor lapatinib. In summary, downregulation of HER2 by targeting Pim1 may be a promising and effective therapeutic approach not only for anti-cancer growth but also for circumventing lapatinib resistance in HER2-positive breast cancer patients.

Monoclonal Antibodies, Small Molecule Inhibitors and Antibody-drug Conjugates as HER2 Inhibitors

Overexpression of human epidermal growth factor receptor (HER)-2 is found in a variety of cancers, often portending poor clinical outcomes. Therefore, HER2 is an attractive target for treatment. This review describes the research progress of HER2 targeted inhibitors in recent years. Excellent reviews are available, so we focus on the development, mechanisms of action, and structure-activity relationships of different types of inhibitors, including monoclonal antibodies, small molecule inhibitors, and antibody-drug conjugates (ADCs). In addition, the differences among them are compared.

EGFR in Cancer: Signaling Mechanisms, Drugs, and Acquired Resistance

The epidermal growth factor receptor (EGFR) has served as the founding member of the large family of growth factor receptors harboring intrinsic tyrosine kinase function. High abundance of EGFR and large internal deletions are frequently observed in brain tumors, whereas point mutations and small insertions within the kinase domain are common in lung cancer. For these reasons EGFR and its preferred heterodimer partner, HER2/ERBB2, became popular targets of anti-cancer therapies. Nevertheless, EGFR research keeps revealing unexpected observations, which are reviewed herein. Once activated by a ligand, EGFR initiates a time-dependent series of molecular switches comprising downregulation of a large cohort of microRNAs, up-regulation of newly synthesized mRNAs, and covalent protein modifications, collectively controlling phenotype-determining genes. In addition to microRNAs, long non-coding RNAs and circular RNAs play critical roles in EGFR signaling. Along with driver mutations, EGFR drives metastasis in many ways. Paracrine loops comprising tumor and stromal cells enable EGFR to fuel invasion across tissue barriers, survival of clusters of circulating tumor cells, as well as colonization of distant organs. We conclude by listing all clinically approved anti-cancer drugs targeting either EGFR or HER2. Because emergence of drug resistance is nearly inevitable, we discuss the major evasion mechanisms.

Targeted dual inhibition of c-Met/VEGFR2 signalling by foretinib improves antitumour effects of nanoparticle paclitaxel in gastric cancer models

Elevated expression of multiple growth factors and receptors including c‐Met and VEGFR has been reported in gastric adenocarcinoma (GAC) and thus provides a potentially useful therapeutic target. The therapeutic efficacy of foretinib, a c‐Met/VEGFR2 inhibitor, was determined in combination with nanoparticle paclitaxel (NPT) in GAC. Animal studies were conducted in NOD/SCID mice in subcutaneous and peritoneal dissemination xenografts. The mechanism of action was assessed by Immunohistochemical and Immunoblot analyses. In c‐Met overexpressing MKN‐45 cell‐derived xenografts, NPT and foretinib demonstrated inhibition in tumour growth, while NPT plus foretinib showed additive effects. In c‐Met low‐expressing SNU‐1 or patient‐derived xenografts, the foretinib effect was smaller, while NPT had a similar effect compared with MKN‐45, as NPT plus foretinib still exhibited an additive response. Median mice survival was markedly improved by NPT (83%), foretinib (100%) and NPT plus foretinib (230%) in peritoneal dissemination xenografts. Subcutaneous tumour analyses exhibited that foretinib increased cancer cell death and decreased cancer cell proliferation and tumour vasculature. NPT and foretinib suppressed the proliferation of GAC cells in vitro and had additive effects in combination. Further, foretinib caused a dramatic decrease in phosphorylated forms of c‐Met, ERK, AKT and p38. Foretinib led to a decrease in Bcl‐2, and an increase in p27, Bax, Bim, cleaved PARP‐1 and cleaved caspase‐3. Thus, these findings highlight the antitumour impact of simultaneous suppression of c‐Met and VEGFR2 signalling in GAC and its potential to enhance nanoparticle paclitaxel response. This therapeutic approach might lead to a clinically beneficial combination to increase GAC patients’ survival.

Combination of HGF/MET-targeting agents and other therapeutic strategies in cancer

MET receptor has emerged as a druggable target across several human cancers. Agents targeting MET and its ligand hepatocyte growth factor (HGF) including small molecules such as crizotinib, tivantinib and cabozantinib or antibodies including rilotumumab and onartuzumab have proven their values in different tumors. Recently, capmatinib was approved for treatment of metastatic lung cancer with MET exon 14 skipping. In this review, we critically examine the current evidence on how HGF/MET combination therapies may take advantage of synergistic effects, overcome primary or acquired drug resistance, target tumor microenvironment, modulate drug metabolism or tackle pharmacokinetic issues. Preclinical and clinical studies on the combination of HGF/MET-targeted agents with conventional chemotherapeutics or molecularly targeted treatments (including EGFR, VEGFR, HER2, RAF/MEK, and PI3K/Akt targeting agents) and also the value of biomarkers are examined. Our deeper understanding of molecular mechanisms underlying successful pharmacological combinations is crucial to find the best personalized treatment regimens for cancer patients.

A comparative study of RTK gene status between primary tumors, lymph-node metastases, and Krukenberg tumors

Krukenberg tumor (KT) refers to a rare ovarian tumor that has metastasized from a primary site. Patients with KTs have a poorer prognosis and worse survival. Thus far, little is known about the frequency of receptor tyrosine kinase (RTK) gene amplification and the concordance of gene amplification between primary tumors, lymph-node metastases, and KTs. Herein, 50 paired samples, including primary cancers, metastatic lymph nodes, and KTs were collected, and RTK gene amplification was tested by fluorescence in situ hybridization (FISH). There were four cases positive for human epidermal growth factor receptor type 2 (HER2) amplification, all of which showed conversion of HER2 status between different lesions. Of the two cases with c-mesenchymal-epithelial transition (c-MET) amplification, the primary tumors and lymph nodes were negative while the right involved ovaries were positive. Inconsistent fibroblast growth factor receptor 2 (FGFR2) status in different lesions was observed in three of the six FGFR2-amplified cases. Co-amplification of RTK genes was identified in only one patient for primary cancer and two for KTs. Collectively, there were 46, 48, 50, and 44 cases negative for HER2, c-MET, EGFR, and FGFR2 amplification in all lesions, respectively. There was no significant difference in overall survival between KTs of gastric origin and colorectal origin. However, of all synchronous cancers, KTs of colorectal origin had a better prognosis than those of gastric origin. In conclusion, the positive rate of RTK gene amplification in KTs was low. Intratumoral heterogeneity was frequent in KTs with RTK gene amplification. A mutually exclusive pattern of RTK gene amplification was dominant in primary cancers, lymph-node metastases, and KTs. There was no survival difference between KTs of gastric origin and colorectal origin. However, of all synchronous cancers, KTs of colorectal origin had a better prognosis than those of gastric origin.

MET Inhibitors for the Treatment of Gastric Cancer: What's Their Potential?

Gastric cancer remains a disease with a dismal prognosis. Extensive efforts to find targetable disease drivers in gastric cancer were implemented to improve patient outcomes. Beyond anti-HER2 therapy, MET pathway seems to be culprit of cancer invasiveness with MET-overexpressing tumors having poorer prognosis. Tyrosine kinase inhibitors targeting the HGF/MET pathway were studied in MET-positive gastric cancer, but no substantial benefit was proven. Some patients responded in early phase trials but later developed resistance. Others failed to show any benefit at all. Etiologies of resistance may entail inappropriate patient selection with a lack of MET detection standardization, tumor alternative pathways, variable MET amplification, and genetic variation. Optimizing MET detection techniques and better understanding the MET pathway, as well as tumor bypass mechanisms, are an absolute need to devise means to overcome resistance using targeted therapy alone, or in combination with other synergistic agents to improve outcomes of patients with MET-positive GC.

Cellular mesenchymal epithelial transition (C-MET) gene copy number variation in gastric adenocarcinoma: A pilot search for new marker for targeted therapy in HER-2/neu resistance

Increasing HER-2/neu resistance in gastric carcinoma has encouraged search for new biomarkers for targeted therapy. Cellular mesenchymal epithelial transition (C-MET) is one such tyrosine kinase inhibitor proposed for personalized salvage treatment. We determined frequency of C-MET gene copy number variation (CNV) by Fluorescent in-situ hybridization (FISH) in gastric adenocarcinoma (GAC) and sought its correlation with conventional clinicopathologic parameters. Dual-coloured FISH was done on 32 GAC cases. C-MET gene and centromere 7 signals were counted under fluorescent microscope and ratio was calculated for each case. Correlation between C-MET CNV and conventional clinic-pathologic parameters was done by Fischer exact test. CNV was identified in the form of amplification and polysomy (3.1% each) and associated with poorer prognostic parameters. Our pilot study highlights limited subset of patients that may benefit from anti-C-MET-targeted therapy and thus could be a novel biomarker for targeted intervention in GAC.

Tyrosine Kinase Inhibitors in the Combination Therapy of HER2 Positive Breast Cancer

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer (BC) accounts for about 20% to 30% of all BC subtypes and is characterized by invasive disease and poor prognosis. With the emergence of anti-HER2 target drugs, HER2-positive BC patient outcomes have changed dramatically. However, treatment failure is mostly due to drug resistance and the special treatment needs of different subgroups. Small molecule tyrosine kinase inhibitors can inhibit multiple targets of the human epidermal growth factor receptor family and activate PI3K/AKT, MAPK, PLC γ, ERK1/2, JAK/STAT, and other pathways affecting the expression of MDM2, mTOR, p27, and other transcription factors. This can help regulate the differentiation, apoptosis, migration, growth, and adhesion of normal cells and reverse drug resistance to a certain extent. These inhibitors can cross the blood-brain barrier and be administered orally. They have a good synergistic effect with effective drugs such as trastuzumab, pertuzumab, t-dm1, and cyclin-dependent kinase 4 and 6 inhibitors. These advantages have resulted in small-molecule tyrosine kinase inhibitors attracting attention. The new small-molecule tyrosine kinase inhibitor was investigated in multi-target anti-HER2 therapy, showed a good effect in preclinical and clinical trials, and to some extent, improved the prognosis of HER2-positive BC patients. Its use could lead to a de-escalation of treatment in some patients, possibly preventing unnecessary procedures along with the associated side effects and costs.

Crizotinib induced antitumor activity and synergized with chemotherapy and hormonal drugs in breast cancer cells via downregulating MET and estrogen receptor levels

MET is a receptor tyrosine kinase known to drive neoplastic transformation and aggressive tumor phenotypes. Crizotinib is an oral multi-targeted tyrosine kinase inhibitor of MET, ALK, RON, and ROS1 kinases. In this study, the anticancer effects of crizotinib on breast cancer cells were investigated in vitro along with the molecular mechanisms associated with these effects. Besides, the antiproliferative effects of crizotinib in combination with chemotherapy, hormonal drugs, and targeted agents were examined. Results showed that crizotinib produced dose-dependent antiproliferative effects in BT-474 and SK-BR-3 breast cancer cells with IC₅₀ values of 1.7 μM and 5.2 μM, respectively. Crizotinib inhibited colony formation of BT-474 cells at low micromolar concentrations (1-5 μM). Immunofluorescence and Western blotting indicated that crizotinib reduced total levels of MET and estrogen receptor (ERα) in BT-474 cells. Also, crizotinib reduced the levels of phosphorylated (active) MET and HER2 in BT-474 cells. The combined treatment of crizotinib with doxorubicin and paclitaxel resulted in synergistic growth inhibition of BT-474 cells with combination index values of 0.46 and 0.35, respectively. Synergy was also observed with the combination of crizotinib with the hormonal drugs 4-hydroxytamoxifen and fulvestrant in BT-474 cells. Alternatively, the combination of crizotinib with lapatinib produced antagonistic antiproliferative effects in both BT-474 and SK-BR-3 cells. Collectively, these findings demonstrate the anticancer effects of crizotinib in breast cancer cells and reveal ERα as a potential therapeutic target of the drug apart from its classical kinase inhibitory activity. Crizotinib could be an appealing option in combination with chemotherapy or hormonal drugs for the management of breast cancer.

Crosstalk Mechanisms Between HGF/c-Met Axis and ncRNAs in Malignancy

Several lines of evidence have confirmed the magnitude of crosstalk between HGF/c-Met axis (hepatocyte growth factor and its high-affinity receptor c-mesenchymal-epithelial transition factor) and non-coding RNAs (ncRNAs) in tumorigenesis. Through activating canonical or non-canonical signaling pathways, the HGF/c-Met axis mediates a range of oncogenic processes such as cell proliferation, invasion, apoptosis, and angiogenesis and is increasingly becoming a promising target for cancer therapy. Meanwhile, ncRNAs are a cluster of functional RNA molecules that perform their biological roles at the RNA level and are essential regulators of gene expression. The expression of ncRNAs is cell/tissue/tumor-specific, which makes them excellent candidates for cancer research. Many studies have revealed that ncRNAs play a crucial role in cancer initiation and progression by regulating different downstream genes or signal transduction pathways, including HGF/c-Met axis. In this review, we discuss the regulatory association between ncRNAs and the HGF/c-Met axis by providing a comprehensive understanding of their potential mechanisms and roles in cancer development. These findings could reveal their possible clinical applications as biomarkers for therapeutic interventions.

Analysis of the Effect of Increased α2,3-Sialylation on RTK Activation in MKN45 Gastric Cancer Spheroids Treated with Crizotinib

In the scenario of personalized medicine, targeted therapies are currently the focus of cancer drug development. These drugs can block the growth and spread of tumor cells by interfering with key molecules involved in malignancy, such as receptor tyrosine kinases (RTKs). MET and Recepteur d'Origine Nantais (RON), which are RTKs frequently overactivated in gastric cancer, are glycoprotein receptors whose activation have been shown to be modulated by the cellular glycosylation. In this work, we address the role of sialylation in gastric cancer therapy using an innovative 3D high-throughput cell culture methodology that mimics better the in vivo tumor features. We evaluate the response to targeted treatment of glycoengineered gastric cancer cell models overexpressing the sialyltransferases ST3GAL4 or ST3GAL6 by subjecting 3D spheroids to the tyrosine kinase inhibitor crizotinib. We show here that 3D spheroids of ST3GAL4 or ST3GAL6 overexpressing MKN45 gastric cancer cells are less affected by the inhibitor. In addition, we disclose a potential compensatory pathway via activation of the Insulin Receptor upon crizotinib treatment. Our results suggest that cell sialylation, in addition of being involved in tumor progression, could play a critical role in the response to tyrosine kinase inhibitors in gastric cancer.

MET inhibitors in cancer: pitfalls and challenges

Introduction: The HGF/MET axis is a key therapeutic pathway in cancer; it is aberrantly activated because of mutations, fusions, amplification or aberrant ligand production. Extensive efforts have been made to discover predictive factors of anti-MET therapeutic efficacy, but they have mostly unsuccessful. An understanding of the intrinsic and acquired mechanism of MET resistance will be fundamental for the development of new therapeutic interventions.Areas covered: This article provides a systematic review of phase II randomized and phase III clinical trials investigating the use of MET inhibitors in the treatment of cancer. We discuss preliminary findings on efficacy and methodologic design flaws in these trials.Expert opinion: MET inhibitors showed poor activity in unselected patients or patients selected by MET expression, p-MET or high HGF basal levels. The efficacy in advanced solid tumors is very modest and in phase III clinical trials, survival differences did not fulfill the stringent requirements of ESMO-Magnitude Clinical Benefit Score (MCBS). Prospective novel liquid biomarker-driven studies and novel trial designs such as Umbrella and Basket trials are necessary to progress MET inhibitor development.

Variety Is the Spice of Life, but Maybe Not in Gastroesophageal Adenocarcinomas

Sanchez-Vega and colleagues prospectively demonstrate that both intra- and intertumoral differential expression of the receptor tyrosine kinases HER2, EGFR, and MET dictate sensitivity to the pan-HER inhibitor afatinib in a phase II trial of trastuzumab-refractory HER2-amplified gastroesophageal adenocarcinomas. Rapid autopsy, tissue-based genomic characterization, and molecular imaging provide complementary information and may aid in selecting optimal patients for targeted monotherapy versus combination approaches in gastroesophageal adenocarcinomas.See related article by Sanchez-Vega et al., p. 199.

MET as resistance factor for afatinib therapy and motility driver in gastric cancer cells

The therapeutic options for advanced gastric cancer are still limited. Several drugs targeting the epidermal growth factor receptor family have been developed. So far, the HER2 antibody trastuzumab is the only drug targeting the HER-family that is available to gastric cancer patients. The pan-HER inhibitor afatinib is currently investigated in clinical trials and shows promising results in cell culture experiments and patient-derived xenograft (PDX) models. However, some cell lines do not respond to afatinib treatment. The determination of resistance factors in these cell lines can help to find the best treatment option for gastric cancer patients. In this study, we analyzed the role of MET as a resistance factor for afatinib therapy in a gastric cancer cell line. MET expression in afatinib-resistant MET-amplified Hs746T cells was reduced by means of siRNA transfection. The effects of MET knockdown on signal transduction, cell proliferation and motility were examined. In addition to the manual assessment of cell motility, a computational motility analysis involving parameters such as (approximate) average speed, displacement entropy or radial effectiveness was realized. Moreover, the impact of afatinib was compared between MET knockdown cells and control cells. MET knockdown in Hs746T cells resulted in impaired signal transduction and reduced cell proliferation and motility. Moreover, the afatinib resistance of Hs746T cells was reversed after MET knockdown. Therefore, the amplification of MET is confirmed as a resistance factor in gastric cancer cells. Whether MET is a useful resistance marker for afatinib therapy or other HER-targeting drugs in patients should be investigated in clinical trials.

Patient-Derived Xenografts and Matched Cell Lines Identify Pharmacogenomic Vulnerabilities in Colorectal Cancer

PURPOSE

Patient-derived xenograft (PDX) models accurately recapitulate the tumor of origin in terms of histopathology, genomic landscape, and therapeutic response, but some limitations due to costs associated with their maintenance and restricted amenability for large-scale screenings still exist. To overcome these issues, we established a platform of 2D cell lines (xeno-cell lines, XL), derived from PDXs of colorectal cancer with matched patient germline gDNA available.

EXPERIMENTAL DESIGN

Whole-exome and transcriptome sequencing analyses were performed. Biomarkers of response and resistance to anti-HER therapy were annotated. Dependency on the WRN helicase gene was assessed in MSS, MSI-H, and MSI-like XLs using a reverse genetics functional approach.

RESULTS

XLs recapitulated the entire spectrum of colorectal cancer transcriptional subtypes. Exome and RNA-seq analyses delineated several molecular biomarkers of response and resistance to EGFR and HER2 blockade. Genotype-driven responses observed in vitro in XLs were confirmed in vivo in the matched PDXs. MSI-H models were dependent upon WRN gene expression, while loss of WRN did not affect MSS XLs growth. Interestingly, one MSS XL with transcriptional MSI-like traits was sensitive to WRN depletion.

CONCLUSIONS

The XL platform represents a preclinical tool for functional gene validation and proof-of-concept studies to identify novel druggable vulnerabilities in colorectal cancer.

Emergence of ERBB2 Mutation as a Biomarker and an Actionable Target in Solid Cancers

The oncogenic role ERBB2 amplification is well established in breast and gastric cancers. This has led to the development of a well-known portfolio of monoclonal antibodies and kinase inhibitors targeting the ERBB2 kinase. More recently, activating mutations in the ERBB2 gene have been increasingly reported in multiple solid cancers and were shown to play an oncogenic role similar to that of ERBB2 amplification. Thus, ERBB2 mutations define a distinct molecular subtype of solid tumors and serve as actionable targets. However, efforts to target ERBB2 mutation has met with limited clinical success, possibly because of their low frequency, inadequate understanding of the biological activity of these mutations, and difficulty in separating the drivers from the passenger mutations. Given the current impetus to deliver molecularly targeted treatments for cancer, there is an important need to understand the therapeutic potential of ERBB2 mutations. Here we review the distribution of ERBB2 mutations in different tumor types, their potential as a novel biomarker that defines new subsets in many cancers, and current data on preclinical and clinical efforts to target these mutations. IMPLICATIONS FOR PRACTICE: A current trend in oncology is to identify novel genomic drivers of solid tumors and developing precision treatments that target them. ERBB2 amplification is an established therapeutic target in breast and gastric cancers, but efforts to translate this finding to other solid tumors with ERBB2 amplification have not been effective. Recently the focus has turned to targeting activating ERBB2 mutations. The year 2018 marked an important milestone in establishing ERBB2 mutation as an important actionable target in multiple cancer types. There have been several recent preclinical and clinical studies evaluating ERBB2 mutation as a therapeutic target with varying success. With increasing access to next-generation sequencing technologies in the clinic, oncologists are frequently identifying activating ERBB2 mutations in patients with cancer. There is a significant need both from the clinician and bench scientist perspectives to understand the current state of affairs for ERBB2 mutations.

Biomarker analysis of the GATSBY study of trastuzumab emtansine versus a taxane in previously treated HER2-positive advanced gastric/gastroesophageal junction cancer

BACKGROUND

Prespecified exploratory biomarker analyses of the phase II/III GATSBY study (NCT01641939) assessed whether patient subgroups experienced a survival benefit from trastuzumab emtansine (T-DM1) versus taxane therapy, and to advance understanding of HER2-positive advanced gastric/gastroesophageal junction cancer (AGC) disease biology.

METHODS

Adults with HER2-positive AGC whose disease progressed during/after first-line therapy were enrolled and randomized to receive T-DM1 [Stage 1: 3.6 mg/kg q3w, 2.4 mg/kg qw, or taxane (docetaxel/paclitaxel); Stage 2: 2.4 mg/kg qw or taxane]. Primary efficacy endpoint was overall survival (OS). Prespecified exploratory biomarkers included HER2, HER3, PTEN, PIK3CA mutation status, FcγR, and cMET. Tumor samples from patients who received 2.4 mg/kg T-DM1 (n = 228) or taxane (n = 117) were included.

RESULTS

Median OS was longer in subgroups with HER2 immunohistochemistry (IHC) 3+ [9.5 versus 8.3 months for T-DM1 versus taxane; hazard ratio (HR) 0.99 (95% CI 0.68-1.43)] versus HER2 IHC 2+/in situ hybridization-positive [5.2 versus 9.2 months for T-DM1 versus taxane; HR 1.53 (95% CI 0.94-2.50)] tumors. Trends towards increased median OS were also observed in subgroups with > versus ≤ median HER2 mRNA expression, higher versus lower HER2 gene copy number, HER2 gene ratio and H score, and homogenous or nonfocal HER2 IHC staining. T-DM1 was not associated with superior OS versus taxane in any subgroup.

CONCLUSIONS

Patients with previously treated HER2-positive AGC with higher HER2 expression experienced a better treatment effect from T-DM1 than those with lower HER2 expression and may derive comparable survival benefits from T-DM1 and taxane therapy.

CLINICAL TRIALS REGISTRATION

NCT01641939 ( https://clinicaltrials.gov/ct2/show/NCT01641939 ).

EPHA2 blockade reverses acquired resistance to afatinib induced by EPHA2-mediated MAPK pathway activation in gastric cancer cells and avatar mice

Afatinib is a pan-HER inhibitor approved for specific types of lung cancer. We explored antitumor activity, predictive biomarkers and the potential mechanisms underlying antitumor effect and acquired resistance of afatinib in gastric cancer (GC) in vitro and in vivo. Five human GC cell lines and eight patient-derived xenograft (PDX) models with clear molecular profiling were used to evaluate the antitumor activity and mechanisms of afatinib. The ErbB family and downstream PI3K/AKT/mTOR and mitogen-activated protein kinase (MAPK) pathways were evaluated before and after afatinib treatment. An afatinib-resistant PDX model was established to explore both the potential mechanisms of drug resistance and reversal strategies. We found that afatinib exerted a strong tumor suppression in EGFR/HER2 highly amplified (copy number >6) or overexpressed (IHC 3+) PDX models and a moderate tumor suppression in EGFR/HER2 moderately expressed (IHC 2+) PDX models. Afatinib selectively inhibited the proliferation of HER2 highly amplified GC cells in a dose-dependent manner in vitro. Afatinib also exerted its antitumor effect by inducing cell apoptosis and cell arrest at G1 phase. Diminished activation of the ErbB family and downstream PI3K/AKT/mTOR and MAPK pathways was also observed. Erythropoietin-producing hepatocellular receptor A2 (EPHA2) upregulation and phosphorylation might be involved in afatinib-acquired resistance, and EPHA2 blockade could restore afatinib sensitivity. GC patients with amplification (copy number >6) or overexpression (IHC 3+) of EGFR/HER2 were most likely to benefit from afatinib treatment and EPHA2 blockade reversed acquired resistance to afatinib treatment, which could provide solid evidences for future clinical trials.

HSP90 inhibitor, AUY922, debilitates intrinsic and acquired lapatinib-resistant HER2-positive gastric cancer cells

Human epidermal growth factor receptor 2 (HER2) inhibitors, such as trastuzumab and lapatinib are used to treat HER2-positive breast and gastric cancers. However, as with other targeted therapies, intrinsic or acquired resistance to HER2 inhibitors presents unresolved therapeutic problems for HER2-positive gastric cancer. The present study describes investigations with AUY922, a heat shock protein 90 (HSP90) inhibitor, in primary lapatinib-resistant (ESO26 and OE33) and lapatinib-sensitive gastric cancer cells (OE19, N87, and SNU-216) harboring HER2 amplification/over-expression. In order to investigate whether AUY922 could overcome intrinsic and acquired resistance to HER2 inhibitors in HER2-positive gastric cancer, we generated lapatinib-resistant gastric cancer cell lines (OE19/LR and N87/LR) by continuous exposure to lapatinib in vitro. We found that activation of HER2 and protein kinase B (AKT) were key factors in inducing intrinsic and acquired lapatinib-resistant gastric cancer cell lines, and that AUY922 effectively suppressed activation of both HER2 and AKT in acquired lapatinib-resistant gastric cancer cell lines. In conclusion, AUY922 showed a synergistic anti-cancer effect with lapatinib and sensitized gastric cancer cells with intrinsic resistance to lapatinib. Dual inhibition of the HSP90 and HER2 signaling pathways could represent a potent therapeutic strategy to treat HER2-positive gastric cancer with intrinsic and acquired resistance to lapatinib.

(-)-Oleocanthal Combined with Lapatinib Treatment Synergized against HER-2 Positive Breast Cancer In Vitro and In Vivo

Dysregulation of epidermal growth factor receptor (EGFR)/human epidermal growth factor-2 (HER2) family is a hallmark of aggressive breast cancer. Small-molecule tyrosine kinase inhibitors are among the most effective cancer targeted treatments. (−)-Oleocanthal (OC) is a naturally occurring phenolic secoiridoid lead from extra-virgin olive oil with documented anti-cancer activities via targeting mesenchymal epithelial transition factor (c-Met). Dysregulation of c-Met promotes aggressiveness to breast cancer-targeted therapies. Lapatinib (LP) is an FDA-approved dual EGFR/HER2 inhibitor for HER2-amplified breast cancer. HER2-Positive tumor cells can escape targeted therapies like LP effects by overexpressing c-Met. Combined OC-LP treatment is hypothesized to be mechanistically synergistic against HER2-overexpressing breast cancer. Combined sub-effective treatments of OC-LP resulted in synergistic anti-proliferative effects against the HER2-positive BT-474 and SK-BR-3 breast cancer cell lines, compared to OC or LP monotherapy. Antibody array and Western blot analysis showed that combined OC-LP treatment significantly inhibited EGFR, HER2, and c-Met receptor activation, as well as multiple downstream signaling proteins, compared to individual OC or LP treatment. OC-LP Combination significantly inhibited invasion and migration of breast cancer cells through reduced activation of focal adhesion kinase (FAK) and paxillin. Combined treatment of OC-10 mg/kg with LP-12.5 mg/kg suppressed more than 90% of BT-474 tumor cells growth in a nude mouse xenograft model, compared to individual OC or LP treatment. Activated c-Met, EGFR, HER2, and protein kinase B (AKT) were significantly suppressed in combination-treated mice tumors, compared to OC or LP monotherapy. This study reveals the OC future potential as combination therapy to sensitize HER2-overexpressing breast cancers and significantly reduce required doses of targeted HER family therapeutics.

EGFR and MET Amplifications Determine Response to HER2 Inhibition in ERBB2-Amplified Esophagogastric Cancer

The anti-HER2 antibody trastuzumab is standard care for advanced esophagogastric (EG) cancer with ERBB2 (HER2) amplification or overexpression, but intrinsic and acquired resistance are common. We conducted a phase II study of afatinib, an irreversible pan-HER kinase inhibitor, in trastuzumab-resistant EG cancer. We analyzed pretreatment tumor biopsies and, in select cases, performed comprehensive characterization of postmortem metastatic specimens following acquisition of drug resistance. Afatinib response was associated with coamplification of EGFR and ERBB2. Heterogeneous 89Zr-trastuzumab PET uptake was associated with genomic heterogeneity and mixed clinical response to afatinib. Resistance to afatinib was associated with selection for tumor cells lacking EGFR amplification or with acquisition of MET amplification, which could be detected in plasma cell-free DNA. The combination of afatinib and a MET inhibitor induced complete tumor regression in ERBB2 and MET coamplified patient-derived xenograft models established from a metastatic lesion progressing on afatinib. Collectively, differential intrapatient and interpatient expression of HER2, EGFR, and MET may determine clinical response to HER kinase inhibitors in ERBB2-amplified EG cancer. SIGNIFICANCE: Analysis of patients with ERBB2-amplified, trastuzumab-resistant EG cancer who were treated with the HER kinase inhibitor afatinib revealed that sensitivity and resistance to therapy were associated with EGFR/ERBB2 coamplification and MET amplification, respectively. HER2-directed PET imaging and cell-free DNA sequencing could help guide strategies to overcome the emergence of resistant clones.See related commentary by Klempner and Catenacci, p. 166.This article is highlighted in the In This Issue feature, p. 151.

Receptor Tyrosine Kinase-Targeted Cancer Therapy

In the past two decades, several molecular targeted inhibitors have been developed and evaluated clinically to improve the survival of patients with cancer. Molecular targeted inhibitors inhibit the activities of pathogenic tyrosine kinases. Particularly, aberrant receptor tyrosine kinase (RTK) activation is a potential therapeutic target. An increased understanding of genetics, cellular biology and structural biology has led to the development of numerous important therapeutics. Pathogenic RTK mutations, deletions, translocations and amplification/over-expressions have been identified and are currently being examined for their roles in cancers. Therapies targeting RTKs are categorized as small-molecule inhibitors and monoclonal antibodies. Studies are underway to explore abnormalities in 20 types of RTK subfamilies in patients with cancer or other diseases. In this review, we describe representative RTKs important for developing cancer therapeutics and predicting or evaluated resistance mechanisms.

Human epidermal growth factor receptor targeted inhibitors for the treatment of ovarian cancer

Ovarian cancer is the second most lethal gynecological cancer worldwide and while most patients respond to initial therapy, they often relapse with resistant disease. Human epidermal growth factor receptors (especially HER1/EGFR and HER2/ERBB2) are involved in disease progression; hence, strategies to inhibit their action could prove advantageous in ovarian cancer patients, especially in patients resistant to first line therapy. Monoclonal antibodies and tyrosine kinase inhibitors are two classes of drugs that act on these receptors. They have demonstrated valuable antitumor activity in multiple cancers and their possible use in ovarian cancer continues to be studied. In this review, we discuss the human epidermal growth factor receptor family; review emerging clinical studies on monoclonal antibodies and tyrosine kinase inhibitors targeting these receptors in ovarian cancer patients; and propose future research possibilities in this area.

Phosphoproteomic analysis reveals PAK2 as a therapeutic target for lapatinib resistance in HER2-positive breast cancer cells

The human epidermal growth factor receptor 2 (HER2)-positive breast cancer with overexpression of HER2 accounts for approximately 25% of breast cancers and is more aggressive than other types of breast cancer. Lapatinib has been widely used as a HER2-targeted therapy, however, a number of patients develop lapatinib resistance and still suffer from poor prognosis. Therefore, it is essential to identify novel therapeutic targets that could overcome lapatinib resistance. In this study, we carried out phosphoproteomic analysis of lapatinib sensitive and resistant cell lines (SKBR3 and SKBR3-LR) using stable isotope labeling with amino acids in cell culture (SILAC). We identified 3808 phosphopeptides from 1807 proteins and then analyzed signaling pathways, Gene Ontology, and protein-protein interaction networks. Finally, we identified PAK2 as a therapeutic target from the network analysis and validated that PAK2 knockdown and PAK inhibitor treatment resensitize the lapatinib resistant cells to lapatinib. This results suggest that PAK2 is a potent therapeutic target to overcome acquired lapatinib resistance in HER2-positive breast cancer cells.

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.