PTEN loss and level of HER2 amplification is associated with trastuzumab resistance and prognosis in HER2-positive gastric cancer

Human Epidermal Growth Factor Receptor 2 Positive Advanced Gastric or Esophagogastric Adenocarcinoma: Reflecting on the Past to Gain a New Insights

PURPOSE OF REVIEW

Human epidermal growth factor receptor 2 (HER2) is a critical target in advanced gastric cancer (AGC). This review highlights the current treatment landscape, lessons learned from past clinical trials, and prospects for future treatment strategies for HER2-positive AGC.

RECENT FINDINGS

Trastuzumab had been the standard treatment for HER2-positive AGC for a decade, and subsequently, trastuzumab deruxtecan, an antibody-drug conjugate (ADC), emerged with an impressive response. Recently, the addition of pembrolizumab to first-line chemotherapy plus trastuzumab has become a novel standard treatment. Past clinical trials of HER2-targeted therapies, which succeeded in HER2-positive breast cancer but failed in AGC, have deepened our understanding of resistance mechanisms. Based on these results, several clinical trials of novel HER2-targeted therapies, including immunologic approaches such as CAR-T cells and vaccines, are currently ongoing. Circulating tumor DNA is also expected to be a tool for real-time biomarker analysis. Additionally, ADCs with a bystander effect have the potential to expand the scope of HER2-targeted therapies to HER2-expressing, including HER2-low AGC. Learning from past trials, further development of novel HER2-targeted therapies is underway, expanding their scope to HER2-expressing AGC. Meanwhile, selecting optimal treatment is a challenging issue in cases with HER2-low AGC overlapping with other biomarkers like CLDN18.2.

Targeted Sequencing of HER2-Positive Breast Cancer Mutations Revealed a Potential Association between PIK3CA and Trastuzumab Resistance

BACKGROUND

Different molecular subtypes, including HER2-positive, have been identified in breast cancer. The overexpression of HER2 triggers downstream signaling pathways such as the PI3K/AKT/mTOR pathway. Until recently, trastuzumab has been used as a single HER2-targeted therapy in Egypt. However, resistance to trastuzumab has been reported. Previous studies have demonstrated the genetic variants that affect the trastuzumab response. However in Egypt, few studies investigated molecular biomarkers such as p53 that might affect the trastuzumab response. Therefore, we aimed to extend the genetics workup of Her2 + BC to include important oncogenes and other vital cancer pathways.

METHODS

Formalin-fixed paraffin-embedded samples were collected from 24 HER2+ BC Egyptian patients, twelve patients in complete remission for 2 years or more from the start of trastuzumab and twelve resistant patients who relapsed or developed metastasis within 2 years from the start of trastuzumab. Somatic mutations in hotspot regions of 17 genes were further investigated using next-generation sequencing.

RESULTS

Among the total number of identified variants (106 variants), PIK3CA showed the most frequent variants, with more variants occurring in the resistant group than in the responsive group (P= 0.004). The frequency of PIK3CA mutations was greater in resistant patients than in responsive patients (P= 0.036). Additionally, there was a significant correlation between PIK3CA mutations and pathological complete response (pCR) (P=0.036). Most of PIK3CA variants in resistant patients were detected in exon 9 and 20. The PIK3CA variants His1047Tyr, Glu545Lys, His701Pro, Lys111Glu, Val344Gly and Tyr1021Cys were found only in the resistant patients, suggesting that they are associated with trastuzumab resistance.

CONCLUSION

PIK3CA variants were more frequent in resistant HER2+ BC patients than in responsive patients, with a significant correlation between PIK3CA mutation and a lower pCR rate. PIK3CA variants within exon 9 and 20 (such as Glu545Lys and His1047Tyr respectively) were associated with trastuzumab resistance.

Establishment of a trastuzumab-resistant extramammary Paget disease model: loss of PTEN as a potential mechanism

BACKGROUND/OBJECTIVES

Extramammary Paget disease (EMPD) is a rare, cutaneous intraepithelial adenocarcinoma typically treated with wide local excision. Unfortunately, a number of patients with metastases show poor responses to chemotherapy. While some studies have explored trastuzumab's effectiveness against EMPD positive for human epidermal growth factor receptor 2 (HER2), trastuzumab resistance (TR) may emerge after anti-HER2 therapy.

METHODS/SUBJECTS

In this study, we established TR EMPD patient-derived xenografts (PDX) that replicated the histological and HER2 expression traits of naive EMPD tumours.

RESULTS

Cancer gene analyses revealed a loss of the PTEN gene in TR tumours, which was further confirmed by immunohistochemical staining and immunoblotting to test for protein expression levels. Reduced PTEN levels correlated with increased protein kinase B (Akt) phosphorylation and p27 downregulation, suggesting a potential mechanism for trastuzumab resistance in EMPD cells. In the trastuzumab-sensitive EMPD-PDX mouse model, PTEN inhibitors partially restored trastuzumab-mediated tumour regression. The TR EMPD-PDX responded favourably to targeted therapy (lapatinib, abemaciclib, palbociclib) and chemotherapy (eribulin, docetaxel, trastuzumab deruxtecan).

CONCLUSIONS

This study demonstrates an innovative TR EMPD-PDX model and introduces promising antineoplastic effects with various treatments for TR EMPD tumours.

Resistance to Anti-HER2 Therapies in Gastrointestinal Malignancies

Human epidermal growth factor 2 (HER2) is a tyrosine kinase receptor that interacts with multiple signaling pathways related to cellular growth and proliferation. Overexpression or amplification of HER2 is linked to various malignancies, and there have been decades of research dedicated to targeting HER2. Despite the landmark ToGA trial, progress in HER2-positive gastrointestinal malignancies has been hampered by drug resistance. This review examines current HER2 expression patterns and therapies for gastroesophageal, colorectal, biliary tract, and small bowel cancers, while dissecting potential resistance mechanisms that limit treatment effectiveness.

Mechanisms of resistance to trastuzumab in HER2-positive gastric cancer

Gastric cancer is one of the most prevalent cancers worldwide, and human epidermal growth factor receptor 2 (HER2)-positive cases account for approximately 20% of the total cases. Currently, trastuzumab + chemotherapy is the recommended first-line treatment for patients with HER2-positive advanced gastric cancer, and the combination has exhibited definite efficacy in HER2-targeted therapy. However, the emergence of drug resistance during treatment considerably reduces its effectiveness; thus, it is imperative to investigate the potential mechanisms underlying resistance. In the present review article, we comprehensively introduce multiple mechanisms underlying resistance to trastuzumab in HER2-positive gastric cancer cases, aiming to provide insights for rectifying issues associated with resistance to trastuzumab and devising subsequent treatment strategies.

HER2-Positive Gastric Cancer and Antibody Treatment: State of the Art and Future Developments

Despite a decreasing incidence in Western countries, gastric cancer is among the most common cancer subtypes globally and is associated with one of the highest tumor-related mortality rates. Biomarkers play an increasing role in the treatment against gastric cancer. HER2 was one of the first biomarkers that found its way into clinical practice. Since the ToGA trial, trastuzumab has been part of first-line palliative chemotherapy in metastatic or unresectable gastric cancer. HER2-targeting agents, such as the tyrosine kinase inhibitor lapatinib, the antibody drug conjugate (ADC) trastuzumab-emtansine or dual HER2 inhibition (pertuzumab and trastuzumab), have been investigated in the second-line setting but led to negative study results. More recently, the ADC trastuzumab-deruxtecan was authorized after the failure of trastuzumab-based treatment. However, further improvements in HER2-directed therapy are required as resistance mechanisms and HER2 heterogeneity limit the existing treatment options. This review aims to give an overview of the current standard-of-care HER2-directed therapy in gastric cancer, as well as its challenges and future developments.

Evaluation of phosphatase and tensin homologue (PTEN) expression in gastric cancer and its relationship with histopathological findings

INTRODUCTION

Phosphatase and tensin homologue (PTEN) is an important tumour suppressor in multi-step tumorigenesis. To establish the role of PTEN in gastric cancer progression, we examined the PTEN expression degree in gastric cancer tissues. We also explained the connection between PTEN expression and histopathological findings.

MATERIALS AND METHODS

Our study was cross-sectional and made up of 50 patients with known gastric cancer. Immunohistochemical staining for PTEN was done on gastric cancer tissues. Tumour behaviour was estimated by histopathological assessments.

RESULTS

Twenty-seven (54%) of the 50 patients had PTEN staining. The evaluation of the connection between PTEN expression and demographic data and tumour behaviours revealed no meaningful relationship between PTEN expression and patients' age, gender, tumour site and size, tumour type, tumour grade and stage, neural, and lymphovascular invasion (P-value>0.05).

CONCLUSION

PTEN expression level is expected to be a significant molecular event in the progression of gastric cancer and may be a predictive marker for gastric cancer behaviours dependent on society.

Genomic characterization between HER2-positive and negative gastric cancer patients in a prospective trial

BACKGROUND

We aimed to clarify the genomic characteristics of HER2-positive and negative gastric cancer cases that potentially affect tumor progression and treatment response in a prospective trial.

METHODS

We collected 80 formalin-fixed paraffin-embedded (FFPE) samples (49 HER2+ and 31 HER2-) from gastric cancer patients who participated in the TROX-A1 trial (UMIN000036865). We queried a 435-gene panel (CANCERPLEX-JP) to generate comprehensive genomic profiling data, including the tumor mutation burden, somatic mutations, and copy number variations. In addition, the genomic differences between HER2+ and HER2- gastric cancer patients were analyzed.

RESULTS

Mutational analyses showed that TP53 was the most frequently mutated gene regardless of HER2 status. ARID1A mutation was significantly enriched in HER2-negative patients. The number of total mutations in HER2-negative patients with ARID1A mutation was remarkably higher than that in HER2-positive patients. Next, copy number variation analyses showed that the number of amplified genes (such as CCNE1, PGAP3, and CDK12) in HER2-positive cases was significantly higher than that in HER2-negative cases. Moreover, PTEN deletion was more common in HER2-positive cases. Finally, we found that, compared with HER2-positive patients, HER2-negative patients tended to have a higher tumor mutation burden, particularly in patients with ARID1A mutation. Pathway analyses of the gene alterations showed an enrichment of several immune-related pathways in HER2-negative patients.

CONCLUSIONS

According to the genomic profiling of HER2-positive and negative gastric cancer, several gene alterations in the HER2 pathway may be the potential mechanism underlying trastuzumab resistance. Relative to HER2-positive gastric cancer, HER2-negative gastric tumors with ARID1A mutation may be sensitive to immune checkpoint inhibitors.

PTEN rs701848 Polymorphism is Associated with Trastuzumab Resistance in HER2-positive Metastatic Breast Cancer and Predicts Progression-free Survival

BACKGROUND

Trastuzumab is an effective therapeutic approach for HER2-positive metastatic breast cancer (BC). However, a considerable number of patients develop resistance along the course of the disease. PTEN rs701848 polymorphisms are associated with an increased risk of developing cancer and have a potential role in predicting drug resistance.

OBJECTIVE

We studied the significance of PTEN rs701848 variants as significant predictors for trastuzumab resistance in HER2-positive metastatic BC patients. Therefore, considering their value in predicting clinical outcomes.

MATERIALS AND METHODS

This case-control study was conducted among female patients with HER2-positive metastatic breast cancer who underwent Trastuzumab therapy during the period from March 2017 to December 2020. PTEN rs701848 genotypes were analyzed in 160 HER2-positive metastatic breast cancer who received Trastuzumab therapy and clinically monitored for therapeutic response.

RESULTS

PTEN rs701848 is deemed a significant predictor of Trastuzumab resistance and an independent prognostic factor of progression-free survival (PPFS). In particular, the C allele is associated with increased risk for Trastuzumab resistance and shorter PFS as compared to the homozygous TT genotype.

CONCLUSION

PTEN rs701848 is significant predictor of trastuzumab resistance. Therefore, their value in predicting clinical outcomes is recommended.

Molecular mechanism of XB130 adaptor protein mediates trastuzumab resistance in gastric cancer

BACKGROUND

Recent studies have shown that the activation of PI3K/AKT signaling pathway is an essential molecular mechanism participating in trastuzumab resistance in HER2 + GC (gastric cancer). However, how can we effectively inhibit AKT activity associated with drug resistance during trastuzumab treatment? Screening inhibitors against the upstream receptors of PI3K/AKT signaling pathway or interacting proteins of members has become an important way.

METHODS

In this study, western blot, qRT-PCR, CCK8, Co-IP and other techniques were used to explore possible mechanisms participating in trastuzumab resistance in vitro. Besides, the xenograft mouse model and GC tissue samples from patients were used to further validate the in-vitro results.

RESULTS

The expression of XB130 adaptor protein was remarkably increased in GC cell lines resistant to trastuzumab, and knockdown of XB130 could reverse the resistance via downregulating p-AKT. In addition, p-SRC (Tyr416) was increased in resistant cells, which could facilitate the binding of XB130 to PI3K p85α. It was also discovered that XB130 could negatively regulate PTEN gene transcription, and thus a positive feedback loop was formed between SRC-XB130-PTEN.

CONCLUSIONS

In HER2 + GC, XB130 contributes to trastuzumab resistance by stimulating the PI3K/AKT signaling pathway through binding to PI3K p85α under the mediation of SRC kinase and regulating PTEN gene transcription, and in turn forming a positive feedback loop between SRC-XB130-PTEN.

Resistance to Trastuzumab

Simple Summary

Trastuzumab is a humanized antibody that has significantly improved the management and treatment outcomes of patients with cancers that overexpress HER2. Many research groups, both in academia and industry, have contributed towards understanding the various mechanisms engaged by trastuzumab to mediate its anti-tumor effects. Nevertheless, data from several clinical studies have indicated that a significant proportion of patients exhibit primary or acquired resistance to trastuzumab therapy. In this article, we discuss underlying mechanisms that contribute towards to resistance. Furthermore, we discuss the potential strategies to overcome some of the mechanisms of resistance to enhance the therapeutic efficacy of trastuzumab and other therapies based on it.

Abstract

One of the most impactful biologics for the treatment of breast cancer is the humanized monoclonal antibody, trastuzumab, which specifically recognizes the HER2/neu (HER2) protein encoded by the ERBB2 gene. Useful for both advanced and early breast cancers, trastuzumab has multiple mechanisms of action. Classical mechanisms attributed to trastuzumab action include cell cycle arrest, induction of apoptosis, and antibody-dependent cell-mediated cytotoxicity (ADCC). Recent studies have identified the role of the adaptive immune system in the clinical actions of trastuzumab. Despite the multiple mechanisms of action, many patients demonstrate resistance, primary or adaptive. Newly identified molecular and cellular mechanisms of trastuzumab resistance include induction of immune suppression, vascular mimicry, generation of breast cancer stem cells, deregulation of long non-coding RNAs, and metabolic escape. These newly identified mechanisms of resistance are discussed in detail in this review, particularly considering how they may lead to the development of well-rationalized, patient-tailored combinations that improve patient survival.

Poorly cohesive cells gastric carcinoma including signet-ring cell cancer: Updated review of definition, classification and therapeutic management

While the incidence of gastric cancer (GC) in general has decreased worldwide in recent decades, the incidence of diffuse cancer historically comprising poorly cohesive cells-GC (PCC-GC) and including signet ring cell cancer is rising. Literature concerning PCC-GC is scarce and unclear, mostly due to a large variety of historically used definitions and classifications. Compared to other histological subtypes of GC, PCC-GC is nevertheless characterized by a distinct set of epidemiological, histological and clinical features which require a specific diagnostic and therapeutic approach. The aim of this review was to provide an update on the definition, classification and therapeutic strategies of PCC-GC. We focus on the updated histological definition of PCC-GC, along with its implications on future treatment strategies and study design. Also, specific considerations in the diagnostic management are discussed. Finally, the impact of some recent developments in the therapeutic management of GC in general such as the recently validated taxane-based regimens (5-Fluorouracil, leucovorin, oxaliplatin and docetaxel), the use of hyperthermic intraperitoneal chemotherapy as well as pressurized intraperitoneal aerosol chemotherapy and targeted therapy have been reviewed in depth for their relative importance for PCC-GC in particular.

Current status and future perspectives in HER2 positive advanced gastric cancer

Gastric cancer is one of the most common malignancy worldwide with a prognosis less than 1 year in unresectable or metastatic disease. HER2 expression is the main biomarker to lead the addition of trastuzumab to first line systemic chemotherapy improving the overall survival in advanced HER2-positivegastric adenocarcinoma. The inevitable development of resistance to trastuzumab remains a great problem inasmuch several treatment strategies that have proven effective in breast cancer failed to show clinical benefit in advanced gastric cancer. In this review, we summarize the available data on the mechanisms underlying primary and secondary resistance toHER2-targeted therapy and current challenges in the treatment of HER2-positive advanced gastric cancer refractory to trastuzumab. Further, we describe the prognostic value of new non-invasive screening techniques, the current development of novel agents such us HER2 antibody-drug conjugates and bispecific antibodies, and the strategies with antitumor activity on going.

Combining gene expression analysis of gastric cancer cell lines and tumor specimens to identify biomarkers for anti-HER therapies-the role of HAS2, SHB and HBEGF

Background

The standard treatment for patients with advanced HER2-positive gastric cancer is a combination of the antibody trastuzumab and platin-fluoropyrimidine chemotherapy. As some patients do not respond to trastuzumab therapy or develop resistance during treatment, the search for alternative treatment options and biomarkers to predict therapy response is the focus of research. We compared the efficacy of trastuzumab and other HER-targeting drugs such as cetuximab and afatinib. We also hypothesized that treatment-dependent regulation of a gene indicates its importance in response and that it can therefore be used as a biomarker for patient stratification.

Methods

A selection of gastric cancer cell lines (Hs746T, MKN1, MKN7 and NCI-N87) was treated with EGF, cetuximab, trastuzumab or afatinib for a period of 4 or 24 h. The effects of treatment on gene expression were measured by RNA sequencing and the resulting biomarker candidates were tested in an available cohort of gastric cancer patients from the VARIANZ trial or functionally analyzed in vitro.

Results

After treatment of the cell lines with afatinib, the highest number of regulated genes was observed, followed by cetuximab and trastuzumab. Although trastuzumab showed only relatively small effects on gene expression, BMF, HAS2 and SHB could be identified as candidate biomarkers for response to trastuzumab. Subsequent studies confirmed HAS2 and SHB as potential predictive markers for response to trastuzumab therapy in clinical samples from the VARIANZ trial. AREG, EREG and HBEGF were identified as candidate biomarkers for treatment with afatinib and cetuximab. Functional analysis confirmed that HBEGF is a resistance factor for cetuximab.

Conclusion

By confirming HAS2, SHB and HBEGF as biomarkers for anti-HER therapies, we provide evidence that the regulation of gene expression after treatment can be used for biomarker discovery.

Trial registration.

Clinical specimens of the VARIANZ study (NCT02305043) were used to test biomarker candidates.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09335-4.

The drugs screened by OncoVeeTM-Mini-PDX have significantly benefited the patient with HER2-positive advanced gastric cancer

Introduction

At present, the prognosis of HER2-positive advanced gastric cancer is extremely poor, and some patients fail to benefit from first-line Herceptin treatment, thus facing difficulties in choosing second-line drugs.

Case Report

Here, we report a 61-year-old male patient with HER2-positive advanced gastric cancer who is primarily resistant to Herceptin and has poor therapeutic effect.

Management & Outcome

Afterwards, the OncoVeeTM-MiniPDX-guided anticancer method was used to screen drugs for second-line treatment, which resulted in liquefaction and necrosis of the patient's lesions and improved liver function indicators, as well as rapid relief of the patient's clinical symptoms.

Discussion

In the treatment of the Herceptin-resistant patient with advanced gastric cancer, OncoVeeTM-MiniPDX method screened drugs and brought clinical benefits.

Human epidermal growth factor receptor 2 (HER2) in advanced gastric cancer: where do we stand?

Gastric cancer is one of the most common malignancy worldwide. In unresectable or metastatic disease, the prognosis is poor and in generally less than a year. HER2 expression remains an important biomarker to lead the addition of trastuzumab to first-line systemic chemotherapy in unresectable or metastatic gastroesophageal adenocarcinoma. To date, a major issue is represented by resistance to trastuzumab developed during treatment, considering the not improved outcomes in this molecular subtype of gastroesophageal adenocarcinoma to other HER2 target strategies. In this review, we summarize the available data on the mechanisms underlying primary and secondary resistance to HER2-targeted therapy and current challenges in the treatment of HER2-positive advanced gastric cancer refractory to trastuzumab. Furthermore, we describe the prognostic value of new non-invasive screening methods, under development novel agents (e.g., HER2 antibody-drug conjugates and bispecific antibodies) and strategies with antitumor activity in early studies.

PTEN is a predictive biomarker of trastuzumab resistance and prognostic factor in HER2-overexpressing gastroesophageal adenocarcinoma

Poor trastuzumab (Tmab) response of patients with human epidermal growth factor receptor 2-overexpressing gastric or gastroesophageal junction adenocarcinoma (HER2-GEA) is associated with the inhibition of phosphatase and tensin homolog (PTEN) expression. In this multicenter, retrospective observational study, pathological samples of patients with HER2-GEA receiving Tmab-combined chemotherapy were immunohistochemically analyzed for PTEN expression. The primary endpoints were disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). We assessed the effect of conventional chemotherapy and Tmab alone or combined with PI3K pathway inhibitors in vitro in HER2-GEA cells with or without PTEN expression. Twenty-nine and 116 patients were in the PTEN-loss and PTEN-positive groups, respectively. In patients with the target region, DCR was significantly lower in PTEN-loss patients than in PTEN-positive patients (67% and 87%, respectively, p = 0.049). The multivariate analysis demonstrated that PTEN loss was significantly associated with shorter PFS (HR = 1.63, p = 0.035) and OS (HR = 1.83, p = 0.022). PTEN knockdown did not affect the cytostatic effect of 5-FU and cisplatin, whereas Tmab combined with the PI3K/mTOR inhibitor NPV-BEZ235 suppressed PTEN-knockdown cell proliferation. In patients with HER2-GEA, PTEN loss is a predictive biomarker of Tmab resistance and prognostic factor. Molecular-targeted therapy with a PI3K/mTOR inhibitor would be effective for HER2-GEA with PTEN loss.

Novel HER2-Directed Treatments in Advanced Gastric Carcinoma: AnotHER Paradigm Shift?

Human epidermal growth factor receptor 2 (HER2) is overexpressed and/or amplified in approximately 15-20% of gastric adenocarcinoma (GC) patients. In 2010, the landmark ToGA trial established the combination of trastuzumab plus chemotherapy as the first-line standard of care for HER2-positive GC patients with advanced disease. However, subsequent studies on HER2 targeted therapies in this setting failed to meet their primary endpoints, and not all HER2-positive GC patients benefit from targeted approaches. More recently, novel HER2-directed treatments have been investigated, including trastuzumab deruxtecan (T-Dxd); following the results of the DESTINY-Gastric01 study, T-Dxd received its first U.S. Food and Drug Administration (FDA) approval on 15 January 2021 for the treatment of adults with unresectable, locally advanced, or metastatic GC who have received a prior trastuzumab-based regimen. In this review, we discuss the current HER2-targeted treatments for GC in the advanced disease setting, mainly focusing on emerging new treatments and future research directions.

Amplification of the human epidermal growth factor receptor 2 (HER2) gene is associated with a microsatellite stable status in Chinese gastric cancer patients

BACKGROUND

Gastric cancer (GC) is one of the most common cancers worldwide. However, little is known about the combination of HER2 amplification and microsatellite instability (MSI) status in GC. This study aimed to analyze the correlation of HER2 amplification with microsatellite instability (MSI) status, clinical characteristics, and the tumor mutational burden (TMB) of patients.

METHODS

A total of 192 gastric cancer (GC) patients were enrolled in this cohort. To analyze genomic alterations (GAs), deep sequencing was performed on 450 target cancer genes. TMB was measured by an in-house algorithm. MSI status was inferred based on the MANTIS (Microsatellite Analysis for Normal-Tumor InStability) score.

RESULTS

The most frequently amplified genes in the GC patients included cyclin E1 (CCNE1), human epidermal growth factor receptor 2 (HER2), fibroblast growth factor receptor 2 (FGFR2), cyclin D1 (CCND1), fibroblast growth factor 19 (FGF19), fibroblast growth factor 3 (FGF3), and fibroblast growth factor 4 (FGF4). The frequency of HER2 amplification was 9.38% (18/192). HER2 amplification was higher in females than in males (14.52% vs. 6.92%, respectively, P=0.091), however, MSI was higher in males compared to females (7.69% vs. 4.84%, respectively, P=0.46). HER2 amplification was higher in metastatic loci compared to primary lesions (23.08% vs. 8.38%, respectively, P=0.079) and was lower in patients with high TMB (TMB-H) compared to those with low TMB (TMB-L) (4.0% vs. 11.35%, respectively, P=0.12). While the frequency of MSI in metastatic foci was higher than that in primary lesions (15.38% vs. 6.15%, respectively, P=0.48), MSI status was highly associated with TMB-H (20% vs. 0%, respectively, P=3.66×10-7). Furthermore, HER2 amplification was negatively correlated with MSI status in Chinese GC patients.

CONCLUSIONS

HER2 amplification was negatively correlated with TMB-H and MSI status, and MSI status was significantly associated with TMB-H in Chinese GC patients. These data suggested that HER2 amplification might be a negative indicator for GC immunotherapy.

PTEN Protein Loss and Loss-of-Function Mutations in Gastric Cancers: The Relationship with Microsatellite Instability, EBV, HER2, and PD-L1 Expression

Inactivation of phosphatase and tensin homolog (PTEN) is caused by multiple mechanisms, and loss of PTEN activity is related to the progression of various cancers. In gastric cancer (GC), the relationship between the loss of PTEN protein expression and various genetic alterations remains unclear. The effects of microsatellite instability (MSI), Epstein–Barr virus (EBV), HER2 overexpression, and PD-L1 expression on PTEN mutation have not been fully explored. We performed comprehensive cancer panel tests with a cohort of 322 tumor samples from patients with advanced GC. Immunohistochemistry for PTEN protein was performed in all cases, and the loss of protein expression was defined as a complete absence of nuclear staining. In total, 34 cases (10.6%) had pathogenic PTEN mutations, of which 19 (55.9%) showed PTEN protein loss. The most common PTEN variants associated with protein loss were p.R130 (n = 4) followed by p.R335, p.L265fs, and deletions (n = 2). All the ten nonsense mutations identified in the samples resulted in PTEN inactivation. In the remaining 288 GC cases with wild-type PTEN, protein loss was found in 35 cases (12.2%). Thus, PTEN mutations were significantly associated with PTEN protein loss (p = 5.232 × 10⁻¹⁰), high MSI (p = 3.936 × 10⁻⁸), and EBV-positivity (p = 0.0071). In conclusion, our results demonstrate that loss-of-function mutations in PTEN are a frequent genetic mechanism of PTEN inactivation in GC.

Targeting PI3Kβ alone and in combination with chemotherapy or immunotherapy in tumors with PTEN loss

Background: PTEN-deficient tumors are dependent on PI3Kβ activity, making PI3Kβ a compelling target. We evaluated the efficacy of PI3Kβ inhibitor AZD8186 on tumors with PTEN loss. Results: In vitro cell viability assay and immunoblotting demonstrated that PTEN loss was significantly correlated with AZD8186 sensitivity in triple negative breast cancer (TNBC) cell lines. Colony formation assay confirmed sensitivity of PTEN-deficient cell lines to AZD8186. AZD8186 inhibited PI3K signaling in PTEN loss TNBC cells. AZD8186 in combination with paclitaxel, eribulin had synergistic effects on growth inhibition in PTEN loss cells. AZD8186 promoted apoptosis in PTEN loss cells which was synergized by paclitaxel. In vivo, AZD8186 had limited activity as a single agent, but enhanced antitumor activity when combined with paclitaxel in MDA-MB-436 and MDA-MB-468 cell-line xenografts. AZD8186 significantly enhanced antitumor efficacy of anti-PD1 antibodies in the PTEN-deficient BP murine melanoma xenograft model, but not in the PTEN-wild-type CT26 xenograft model. Methods: In vitro, cell proliferation and colony formation assays were performed to determine cell sensitivity to AZD8186. Immunoblotting was performed to assess PTEN expression and PI3K signaling activity. FACS was performed to evaluate apoptosis. In vivo, antitumor efficacy of AZD8186 and its combinations were evaluated. Conclusions: AZD8186 has single agent efficacy in PTEN-deficient TNBC cell lines in vitro, but has limited single agent efficacy in vivo. However, AZD8186 has enhanced efficacy when combined with paclitaxel and anti-PD1 in vivo. Further study is needed to determine optimal combination therapies for PTEN-deficient solid tumors.

HER2 Heterogeneity in Personalized Therapy of Gastro-Oesophageal Malignancies: An Overview by Different Methodologies

Human epidermal growth factor receptor-2 (HER2)-expression gastro-oesophageal adenocarcinomas (GEA) gained interest as an important target for therapy with trastuzumab. In the current review, we focused the current knowledge on HER2 status in dysplastic and neoplastic gastric conditions, analyzing the methodological procedures to identify HER2 expression/amplification, as well as the proposed scoring recommendations. One of the most relevant questions to evaluate the useful impact of HER2 status on therapeutic choice in GEAs is represented by the significant heterogeneity of HER2 protein and gene expression that may affect the targeted treatment selection. Future development of biotechnology will continue to evolve in order to offer more powerful detection systems for the assessment of HER2 status. Finally, liquid biopsy as well as mutation/amplification of several additional genes may furnish an early detection of secondary HER2 resistance mechanisms in GEAs with a better monitoring of the treatment response.

Precision medicine for gastrointestinal cancer: Recent progress and future perspective

Gastrointestinal (GI) cancer has a high tumor incidence and mortality rate worldwide. Despite significant improvements in radiotherapy, chemotherapy, and targeted therapy for GI cancer over the last decade, GI cancer is characterized by high recurrence rates and a dismal prognosis. There is an urgent need for new diagnostic and therapeutic approaches. Recent technological advances and the accumulation of clinical data are moving toward the use of precision medicine in GI cancer. Here we review the application and status of precision medicine in GI cancer. Analyses of liquid biopsy specimens provide comprehensive real-time data of the tumor-associated changes in an individual GI cancer patient with malignancy. With the introduction of gene panels including next-generation sequencing, it has become possible to identify a variety of mutations and genetic biomarkers in GI cancer. Although the genomic aberration of GI cancer is apparently less actionable compared to other solid tumors, novel informative analyses derived from comprehensive gene profiling may lead to the discovery of precise molecular targeted drugs. These progressions will make it feasible to incorporate clinical, genome-based, and phenotype-based diagnostic and therapeutic approaches and apply them to individual GI cancer patients for precision medicine.

Durable Clinical Response to Pyrotinib After Resistance to Prior Anti-HER2 Therapy for HER2-Positive Advanced Gastric Cancer: A Case Report

Background: Patients with advanced gastric cancer, especially the HER2-positive type, have a poor prognosis; there is a paucity of effective anti-HER2 drug therapies in patients who develop resistance to trastuzumab. Case presentation: We report the case of a 36-year-old male with HER2-positive gastric cancer with lung and liver metastases. The patient responded after treatment with trastuzumab combined with chemotherapy and attained a progression-free survival (PFS) of 17 months. Subsequently, the patient received apatinib that selectively inhibits the VEGFR2 and obtained an evident tumor response and a PFS of 8 months. When the disease progressed again, the regimen containing lapatinib failed. Then, the patient received treatment with nivolumab. However, he presented with hyper-progressive disease (HPD). Finally, he received a combination of capecitabine and pyrotinib, an irreversible dual TKI, acting on HER2 and EGFR. The tumor shrank markedly with this combination therapy. The mechanism of both HPD due to immunotherapy and the resistance to trastuzumab and lapatinib were investigated in this case. Loss of phosphatase and tensin homolog (PTEN) and new mutations of BRCA1 and KRAS were detected after resistance to trastuzumab and lapatinib. Conclusions: For patients with HER2-positive advanced gastric cancer who have developed resistance to trastuzumab, pyrotinib is a promising new agent, which can be used as salvage therapy.

CMIP promotes Herceptin resistance of HER2 positive gastric cancer cells

Gastric cancer remains one of the most malignant human cancers with poor prognosis. Herceptin is a well-received antibody drug for HER2 positive gastric cancer. Primary Herceptin resistance and acquired Herceptin resistance retarded the use of Herceptin for gastric cancer. We herein reported CMIP (C-Maf-inducing protein) was overexpressed in Herceptin-resistant gastric cancer cells MKN45-HR and NCI-N87-HR; CMIP promoted Herceptin resistance of HER2 positive gastric cancer cells. SOX2 was examined to be positively regulated by CMIP and also promoted Herceptin resistance of HER2 positive gastric cancer cells. SOX2 might mediate the Herceptin resistance promoting role of CMIP in gastric cancer cells. Elevated expression of CMIP was associated with poor clinicopathological features including tumor size, lymph node metastasis and clinical stage in HER2 positive gastric cancer patients. Inhibitors of CMIP could be used as potential adjuvant therapeutic drugs for HER2 positive gastric cancer.

Novel Biomarkers for Prediction of Response to Preoperative Systemic Therapies in Gastric Cancer

Preoperative chemo- and radiotherapeutic strategies followed by surgery are currently a standard approach for treating locally advanced gastric and esophagogastric junction cancer in Western countries. However, in a large number of cases, the tumor is extremely resistant to these treatments and the patients are exposed to unnecessary toxicity and delayed surgical therapy. The current clinical trials evaluating the combination of preoperative systemic therapies with modern targeted and immunotherapeutic agents represent a unique opportunity for identifying predictive biomarkers of response to select patients that would benefit the most from these treatments. However, it is of utmost importance that these potential biomarkers are corroborated by extensive preclinical and translational research. The aim of this review article is to present the most promising biomarkers of response to classic chemotherapeutic, anti-HER2, antiangiogenic, and immunotherapeutic agents that can be potentially useful for personalized preoperative systemic therapies in gastric cancer patients.

Trastuzumab in combination with paclitaxel enhances antitumor activity by promoting apoptosis in human epidermal growth factor receptor 2-positive trastuzumab-resistant gastric cancer xenograft models

Trastuzumab, a humanized anti-human epidermal growth factor receptor 2 antibody drug, is the first-line therapy for human epidermal growth factor receptor 2-positive breast and gastric cancer. For breast cancer, the benefit of continuous treatment with trastuzumab after it becomes refractory to first-line therapy has been demonstrated. However, it is unclear whether trastuzumab can show similar efficacy as a second-line treatment for gastric cancer. Here, we report that trastuzumab in combination with paclitaxel exhibits increased antitumor efficacy even for trastuzumab-resistant xenografted tumors. We derived the trastuzumab-resistant models from previously established human epidermal growth factor receptor 2-positive gastric cancer patient-derived cells. Human epidermal growth factor receptor 2 expression, PIK3CA mutation, and phosphatase and tensin homolog expression in these resistant models was equivalent to those in the trastuzumab-sensitive parental model, whereas cyclin-dependent kinase inhibitors, such as p16, p15, and p21, were downregulated. Trastuzumab in combination with paclitaxel enhanced antitumor activity in both the sensitive and resistant models. In the trastuzumab-sensitive model, the combination of trastuzumab and paclitaxel resulted in suppression of the AKT-p27-retinoblastoma protein pathway and induction of apoptosis. Although this combination did not suppress retinoblastoma protein phosphorylation in the trastuzumab-resistant model, it did markedly decrease epidermal growth factor receptor and human epidermal growth factor receptor 2 phosphorylation and further enhance paclitaxel-mediated apoptosis. These results suggested that trastuzumab in combination with paclitaxel can still exert more potent antitumor efficacy than each agent alone in trastuzumab-resistant models, providing evidence that trastuzumab remains beneficial in the treatment of trastuzumab-resistant tumors.

Clinical and molecular prognostic markers of survival after surgery for gastric cancer: tumor-node-metastasis staging system and beyond

For accurately predicting prognosis and for effectively describing cancer states at a certain point during treatment to other care providers and patients, various staging systems have been utilized in gastric cancer. Among these, the UICC/AJCC tumor-node-metastasis (TNM) staging system is most widely used. However, even within the same substage, gastric cancers can vary substantially in regards to prognosis after treatment. For more accurate and individualized prognostication, staging systems have been found to benefit from including molecular markers and genomic subtypes, in addition to clinicopathological parameters, such as age, sex, tumor size, tumor location, Lauren classification, number of lymph nodes resected, extent of surgical resection, lymphovascular invasion, and adjuvant chemotherapy. In this review article, we review and summarize relevant biomarkers for gastric cancer that can be incorporated into the current anatomy-based TNM staging system, as well as results from validation studies thereof.

Bone metastases from a 1p/19q codeleted and IDH1-mutant anaplastic oligodendroglioma: a case report

BACKGROUND

Oligodendroglioma is a rare type of primary brain tumor which, like other malignant gliomas, metastasizes very rarely even when in high-grade form.

CASE REPORT

A 36-year-old white man diagnosed 29 months previously as having 1p/19q codeleted anaplastic oligodendroglioma presented bilateral cruralgia and lower limb motor deficits. A computed tomography scan showed multiple osteoblastic bone lesions. The presence of oligodendroglial cells was revealed by bone marrow biopsy and confirmed by immunohistochemical analyses. A positon emission tomography-computed tomography scan confirmed the exclusive involvement of bones.

CONCLUSION

This case joins less than 20 other reported cases of oligodendroglioma bone marrow metastasis, and is one of only a handful of cases of diffuse bone metastases beyond the axial skeleton. To the best of our knowledge, the early relapse of 1p/19q codeleted anaplastic oligodendroglioma with this distribution of metastases has never been described in the literature.

Monoclonal antibody therapy of solid tumors: clinical limitations and novel strategies to enhance treatment efficacy

Monoclonal antibodies (mAbs) have become a cornerstone in the therapeutic guidelines of a wide range of solid tumors. The targeted nature of these biotherapeutics has improved treatment outcomes by offering enhanced specificity to reduce severe side effects experienced with conventional chemotherapy. Notwithstanding, poor tumor tissue penetration and the heterogeneous distribution achieved therein are prominent drawbacks that hamper the clinical efficacy of therapeutic antibodies. Failure to deliver efficacious doses throughout the tumor can lead to treatment failure and the development of acquired resistance mechanisms. Comprehending the morphological and physiological characteristics of solid tumors and their microenvironment that affect tumor penetration and distribution is a key requirement to improve clinical outcomes and realize the full potential of monoclonal antibodies in oncology. This review summarizes the essential architectural characteristics of solid tumors that obstruct macromolecule penetration into the targeted tissue following systemic delivery. It further describes mechanisms of resistance elucidated for blockbuster antibodies for which extensive clinical data exists, as a way to illustrate various modes in which cancer cells can overcome the anticancer activity of therapeutic antibodies. Thereafter, it describes novel strategies designed to improve clinical outcomes of mAbs by increasing potency and/or improving tumor delivery; focusing on the recent clinical success and growing clinical pipeline of antibody-drug conjugates, immune checkpoint inhibitors and nanoparticle-based delivery systems.

Randomised phase II trial comparing four front-line doublets in Asian patients with metastatic gastric cancer

INTRODUCTION

Consensus has not been reached regarding the standard regimen for front-line chemotherapy of recurrent/metastatic gastric cancer. In this randomised phase II study, we compared four doublet regimens: S-1 and cisplatin (SP); oxaliplatin and 5-FU (FOLFOX); docetaxel and 5-FU (DF) and paclitaxel and 5-FU (PF).

PATIENTS AND METHODS

Patients without prior history of chemotherapy for recurrent/metastatic gastric cancer were randomised evenly to each regimen. The primary end-point was progression-free survival (PFS). The secondary end-points were overall survival (OS), response rate (RR) and safety profile.

RESULTS

A total of 179 Korean patients were enrolled from March 2010 to May 2015. The study was prematurely terminated because of slow accrual. At data cut-off, the median PFS was 8.4 months for SP, 5.8 months for FOLFOX, 5.7 months for DF and 4.2 months for PF (P = 0.023). The median OS was 14.7 months for SP, 11.3 months for FOLFOX, 11.7 months for DF and 10.8 months for PF (P = 0.143). RR was 18%, 23%, 16% and 32% for SP, FOLFOX, DF and PF, respectively. The platinum group displayed a longer PFS trend than the taxane group (7.2 versus 4.9 months, P = 0.058), but no significant difference in OS was found. Notably, 105 patients were exposed to all three drugs (platinum, taxane and fluoropyrimidine) throughout the treatment course, and OS was identical whether starting with platinum or taxane (13.3 versus 13.3 months, P = 0.997). All regimens were well tolerated.

CONCLUSION

SP showed the most favourable results in PFS, whereas a significant difference in OS was not observed among the four regimens.

The role of the phosphatase and tensin homolog status in predicting pathological complete response to neoadjuvant anti-HER2 therapies in HER2-positive primary breast cancer: A meta-analysis

PURPOSE

The addition of anti-HER2 therapies to neoadjuvant treatment significantly enhances pathological complete response (PCR) rate in patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Selecting patients unlikely to benefit from neoadjuvant anti-HER2 therapies is increasingly important. In this study, we proposed to assess the role of the phosphatase and tensin homolog (PTEN) as a biomarker in predicting PCR to neoadjuvant anti-HER2 therapies by conducting meta-analysis.

METHODS

Our team searched Embase, Medline, and the Cochrane Library by the end of September 16, 2018, for trials on patients with HER2-positive breast cancer treated with neoadjuvant anti-HER2 therapies. The associations between PTEN expression and PCR rate were then assessed. Odds ratio (ORs) and hazard ratio (HRs) with 95% confidence intervals (CIs) with 2-sided P values were calculated. The Newcastle-Ottawa scale (NOS) was used to estimate the quality of the involved trials.

RESULTS

A total of 820 patients from 8 trials were included in this meta-analysis. Overall, the PTEN normal tumors was related to a significant increase in PCR rate (OR 0.55; 95% CI = 0.31-0.96; P = .04; I = 54%). In different anti-HER2 agents analysis, the PTEN normal tumors was related to a significant increase in PCR rate in patients treated with trastuzumab alone (OR 0.40; 95% CI = 0.24-0.67; P = .0005; I = 15%). Besides, no significant association between PTEN status and PCR rate was detected in patients treated with lapatinib alone (OR 1.90; 95% CI = 0.78-4.60; P = .16; I = 0%) or trastuzumab plus lapatinib (OR 1.27; 95% CI = 0.27-5.97; P = .76; I = 73%).

CONCLUSION

Based on current evidence, PTEN status could be n suitable biomarker in predicting PCR rate to neoadjuvant anti-HER2 therapies, especially in trastuzumab-treated patients.

Hsa_circ_0033155: A potential novel biomarker for non-small cell lung cancer

Circular RNAs (circRNAs) are a novel type of endogenous RNAs and increasing evidence have uncovered the important role of circRNA in tumor progression; however, the function of circRNAs in non-small cell lung cancer (NSCLC) remains largely unclear. In the present study, it was demonstrated that the expression level of hsa_circ_0033155 was significantly downregulated in NSCLC tissue and the expression of hsa_circ_0033155 correlated with lymphatic metastasis. In order to further investigate the possible role of hsa_circ_0033155 in NSCLC progression, circRNA was overexpressed in NSCLC cells and it was observed that the overexpression of hsa_circ_0033155 significantly decreased cell proliferation, colony formation and migration, and elevated the level of phosphatase and tensin homolog deleted on chromosome 10, a tumor suppressor in many types of tumor. In conclusion, hsa_circ_0033155 may serve as a prospective biomarker for detection and a promising therapeutic target for NSCLC.

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.

Molecular biomarkers in gastro-esophageal cancer: recent developments, current trends and future directions

Gastro-esophageal adenocarcinomas (GEA) represent a severe global health burden and despite improvements in the multimodality treatment of these malignancies the prognosis of patients remains poor. HER2 overexpression/amplification has been the first predictive biomarker approved in clinical practice to guide patient selection for targeted treatment with trastuzumab in advanced gastric and gastro-esophageal junction cancers. More recently, immunotherapy has been approved for the treatment of GEA and PD-L1 expression is now a biomarker required for the administration of pembrolizumab in these diseases. Significant progress has been made in recent years in dissecting the genomic makeup of GEA in order to identify distinct molecular subtypes linked to distinct patterns of molecular alterations. GEA have been found to be highly heterogeneous malignances, representing a challenge for biomarkers discovery and targeted treatment development. The current review focuses on an overview of established and novel promising biomarkers in GEA, covering recent molecular classifications from TCGA and ACRG. Main elements of molecular heterogeneity are discussed, as well as emerging mechanisms of primary and secondary resistance to HER2 targeted treatment and recent biomarker-driven trials. Future perspectives on the role of epigenetics, miRNA/lncRNA and liquid biopsy, and patient-derived xenograft models as a new platform for molecular-targeted drug discovery in GEA are presented. Our knowledge on the genomic landscape of GEA continues to evolve, uncovering the high heterogeneity and deep complexity of these tumors. The availability of new technologies and the identification of promising novel biomarker will be critical to optimize targeted treatment development in a setting where therapeutic options are currently lacking. Nevertheless, clinical validation of novel biomarkers and treatment strategies still represents an issue.

Value of CagA, HER2, ALDH1, and KiSS-1 in predicting metastasis and prognosis for gastric adenocarcinoma

BACKGROUND

Cytotoxin-associated gene A (CagA), is able to translocate into gastric epithelial cells. Human epidermal growth factor receptor 2 (also named as HER2, is a proto-oncogene which can encode a transmembrane receptor), Aldehyde dehydrogenase 1 (ALDH1, a biomarker of cancer stem cells), and KiSS-1 (a suppressor gene of cancer metastasis) are all valuably predictive biomarkers for various human cancers. The purpose of this study is to investigate the associations among CagA, HER2, ALDH1, and KiSS-1 in gastric adenocarcinoma (GAC), and their respective associations with clinical characteristics and survival in GAC.

METHODS

The expression of CagA, HER2, ALDH1, and KiSS-1 in 232 cases of whole GAC tissues were detected by immunohistochemical staining. Patient clinical and survival data were also collected.

RESULTS

Positive expression of CagA, HER2, and ALDH1 is significantly higher, and positive expression of KiSS-1 is significantly lower, in GAC tissues than in the corresponding normal tissues. Furthermore, the positive expression of CagA, HER2, ALDH1, and KiSS-1 were significantly associated with tumor grade, tumor stage, lymph node metastasis (LNM) stage, and tumor node metastasis (TNM) stages, and with patients' overall survival (OS); whereas the KiSS-1 positive group had longer OS than did the KiSS-1 negative group. In logistic analysis, positive expression of CagA, HER2, ALDH1, and KiSS-1 are significantly associated with LNM of patients with GAC. COX regression analysis indicated that positive expression of CagA, HER2, ALDH1, and KiSS-1, and tumor stages, LNM stages, and TNM stages were independent prognostic factors for patients with GAC.

CONCLUSIONS

Expression of CagA, HER2, ALDH1, and KiSS-1 should be considered as promising biomarkers for metastasis and prognosis, as well as potential therapeutic targets for GAC.