HER2-positive Gastric Cancer Patients Research Articles

MiR-301a-3p induced by endoplasmic reticulum stress mediates the occurrence and transmission of trastuzumab resistance in HER2-positive gastric cancer

Trastuzumab resistance negatively influences the clinical efficacy of the therapy for human epidermal growth factor receptor 2 (HER2) positive gastric cancer (GC), and the underlying mechanisms remain elusive. Exploring the mechanisms and finding effective approaches to address trastuzumab resistance are of great necessity. Here, we confirmed that endoplasmic reticulum (ER) stress-induced trastuzumab resistance by up-regulating miR-301a-3p in HER2-positive GC cells. Moreover, we elucidated that miR-301a-3p mediated trastuzumab resistance by down-regulating the expression of leucine-rich repeats and immunoglobulin-like domains containing protein 1 (LRIG1) and subsequently activating the expression of insulin-like growth factor 1 receptor (IGF-1R) and fibroblast growth factor receptor 1 (FGFR1) under ER stress. We also found that intercellular transfer of miR-301a-3p by exosomes disseminated trastuzumab resistance. The present study demonstrated that exosomal miR-301a-3p could serve as a non-invasive biomarker for trastuzumab resistance, which was maybe a novel potential therapeutic target to overcome trastuzumab resistance and improve the curative effect of trastuzumab in HER2-positive GC patients.

HER2 Splice Site Mutation c.1899-1G>A as the Potential Acquired Resistance to Trastuzumab in a Patient with HER2-Positive Gastric Adenocarcinoma.

The addition of trastuzumab to chemotherapy regimen is the standard of care for human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer; however, most patients eventually acquire trastuzumab resistance. Although some resistance mechanisms to trastuzumab-based regimens have been proposed, further understanding is required for developing therapeutic strategies to overcome the resistance. In the present work, we attempted to determine the possible resistance mechanism to trastuzumab in a patient with HER2-positive stage IV gastric adenocarcinoma. In this study, we first report the nucleotide change c.1899-1G>A at the intron 15 acceptor splice site promoting exon 16 deletion of HER2 as the potential mechanism of trastuzumab resistance in HER2-positive gastric adenocarcinoma. KEY POINTS: The combination of trastuzumab with chemotherapy is considered to be the standard therapy for HER2-positive advanced gastric cancer (GC), but most of the patients eventually acquire trastuzumab resistance. The mechanisms of resistance to trastuzumab in GC are poorly characterized. To the best of the authors' knowledge, this study is the first to implicate HER2 c.1899-1G>A, which results in exon 16 skpping, as the acquired resistance mechanism to trastuzumab in HER2-positive gastric adenocarcinoma. This work provides insights into the potential molecular mechanism of trastuzumab resistance, which is crucial in developing effective therapeutic strategies for HER2-positive GC patients refractory to trastuzumab.

Trastuzumab Deruxtecan: Changing the Destiny of HER2 Expressing Solid Tumors.

HER2 targeted therapies have significantly improved prognosis of HER2-positive breast and gastric cancer. HER2 overexpression and mutation is the pathogenic driver in non-small cell lung cancer (NSCLC) and colorectal cancer, however, to date, there are no approved HER2-targeted therapies with these indications. Trastuzumab deruxtecan (T-DXd) is a novel HER2-directed antibody drug conjugate showing significant anti-tumor activity in heavily pre-treated HER2-positive breast and gastric cancer patients. Preliminary data have shown promising objective response rates in patients with HER2-positive NSCLC and colorectal cancer. T-DXd has an acceptable safety profile, however with concerns regarding potentially serious treatment-emergent adverse events. In this review we focus on the pharmacologic characteristics and toxicity profile of T-Dxd, and provide an update on the most recent results of clinical trials of T-DXd in solid tumors. The referenced papers were selected through a PubMed search performed on 16 March 2021 with the following searching terms: T-DXd and breast cancer, or gastric cancer, or non-small cell lung cancer (NSCLC), or colorectal cancer. Oral presentation, abstracts, and posters presented at the American Society of Clinical Oncology (ASCO, Alexandria, VA, USA) 2020 and the European Society for Medical Oncology (ESMO, Lugano, Switzerland) 2020 annual meetings were retrieved for data on T-DXd. We also overview ongoing research and data of combination therapies currently under investigation, which will impact on future therapeutic strategies. Clinicaltrials.gov was searched to identify ongoing clinical trials of T-DXd alone or in combination in solid tumors.

Changes in the therapeutic landscape of oesophago-gastric cancers.

This article reviews recent randomised clinical trials on systemic treatment of oesophago-gastric cancers in the perioperative and metastatic setting. Adding nivolumab to first-line chemotherapy improved survival in patients with metastatic gastric/gastro-oesophageal junction/oesophageal adenocarcinoma with PD-L1 combined positive score (CPS) ≥ five in a global trial and progression-free survival in metastatic gastric/gastro-oesophageal junction cancers in an Asian trial. The addition of pembrolizumab to first-line chemotherapy improved survival in metastatic oesophageal cancer patients, with the most benefit in oesophageal squamous cancer and tumours with high PD-L1 expression (CPS ≥ 10). Adjuvant nivolumab improved disease-free survival (DFS) in resectable oesophageal cancer patients with residual pathologic disease after neoadjuvant chemoradiation. In human epidermal growth factor receptor 2 (HER2)-positive oesophago-gastric adenocarcinoma, a phase II trial showed improved DFS when pertuzumab and trastuzumab were added to perioperative FLOT (5-fluorouracil/leucovorin, oxaliplatin, docetaxel). Another phase II trial showed improved response rates and survival in pretreated metastatic HER2-positive gastric and gastrooesophageal junction cancer patients who received the antibody-drug conjugate trastuzumab deruxtecan compared to physician's choice of chemotherapy. Chemo-immunotherapy combinations will become the new standard of care for some patients with metastatic oesophago-gastric cancers. Adjuvant nivolumab is a new option for oesophageal cancer patients with poor response after neoadjuvant chemoradiation.

Development of a Novel Weighted Ranking Method for Immunohistochemical Quantification of a Heterogeneously Expressed Protein in Gastro-Esophageal Cancers.

Simple SummaryHigh levels of the protein Junctional Adhesion Molecule-A (JAM-A) have been linked with aggressive disease in patients with several different cancers. However, its distribution is often non-uniform (heterogeneous) across tumors, and can be difficult to quantify. JAM-A has also been linked with high levels of HER2 (an important oncogene) in breast tumors, and the development of resistance to HER2-targeted drugs in those patients. Since gastro-esophageal (GE) cancers are often high in HER2 and have also been approved for HER2-targeted drugs, the aim of this study was to investigate if levels of JAM-A and HER2 are linked in GE cancer. JAM-A was expressed very heterogeneously across miniaturized tissue sections called tissue microarrays (TMAs) of GE cancer patients. In this model, therefore, there was no correlation between JAM-A and HER2 expression. However, when we used larger tissue sections and developed a scoring system to account for heterogeneity, a significant correlation between JAM-A and HER2 levels emerged. This work illustrates the importance of taking intra-tumor heterogeneity into account, particularly in an era when analysis of protein levels by this method is increasingly used to select patients for targeted cancer drugs.High expression of Junctional Adhesion Molecule-A (JAM-A) has been linked with poor prognosis in several cancers, including breast cancers overexpressing the human epidermal growth factor receptor-2 (HER2). Furthermore, JAM-A expression has been linked with regulating that of HER2, and associated with the development of resistance to HER2-targeted therapies in breast cancer patients. The purpose of this study was to establish a potential relationship between JAM-A and HER2 in HER2-overexpressing gastro-esophageal (GE) cancers. Interrogation of gene expression datasets revealed that high JAM-A mRNA expression was associated with poorer survival in HER2-positive gastric cancer patients. However, high intra-tumoral heterogeneity of JAM-A protein expression was noted upon immunohistochemical scoring of a GE cancer tissue microarray (TMA), precluding a simple confirmation of any relationship between JAM-A and HER2 at protein level. However, in a test-set of 25 full-face GE cancer tissue sections, a novel weighted ranking system proved effective in capturing JAM-A intra-tumoral heterogeneity and confirming statistically significant correlations between JAM-A/HER2 expression. Given the growing importance of immunohistochemistry in stratifying cancer patients for the receipt of new targeted therapies, this may sound a cautionary note against over-relying on cancer TMAs in biomarker discovery studies of heterogeneously expressed proteins. It also highlights a timely need to develop validated mechanisms of capturing intra-tumoral heterogeneity to aid in future biomarker/therapeutic target development for the benefit of cancer patients.

Overexpression of GSE1 Related to Trastuzumab Resistance in Gastric Cancer Cells.

Gastric cancer is one of the most prevalent human cancers with poor prognosis. Trastuzumab is a well-used targeted drug for gastric cancer with HER2 amplification. Trastuzumab resistance restrains the clinical use of trastuzumab. In this study, we reported human Gse1 coiled-coil protein (GSE1) promoted trastuzumab resistance in HER2-positive gastric cancer cells. Acquired trastuzumab-resistant gastric cancer cells overexpressed GSE1, and depletion of GSE1 decreased the trastuzumab resistance of trastuzumab-resistant gastric cancer cells. BCL-2 was a downstream gene positively regulated by GSE1 and also performed promoting the role of trastuzumab resistance in HER2-positive gastric cancer cells. A high level of GSE1 was associated with a high risk of tumor lymph node metastasis and higher clinical stage in HER2-positive gastric cancer patients. GSE1 was a potential target that could be used for HER2-positive gastric cancer therapy.

Inhibitory effects of combinations of trastuzumab and cytotoxic chemotherapy drugs in HER2-positive gastric cancer

Human epidermal growth factor receptor 2 (HER2) proteins are overexpressed in a certain proportion of gastric cancer cases. Trastuzumab is a humanized monoclonal antibody that targets the HER2 receptor. Previous studies have demonstrated a synergistic interaction between trastuzumab and 5-fluorouracil/cisplatin in HER2-positive gastric cancer cells. However, it is unclear whether it is rational to combine trastuzumab with other chemotherapy regimens in clinical practice. We evaluated the growth inhibitory effects of combinations of trastuzumab and cytotoxic chemotherapy drugs in HER2-positive gastric cancer cell lines. HER2 protein expression was evaluated by Western blotting in five gastric cancer cell lines. MTT assays were performed to evaluate the growth inhibitory effects of trastuzumab and four chemotherapeutic agents, epirubicin, cisplatin, 5-fluorouracil and docetaxel, both alone and in combination. To explore the molecular mechanisms underlying the synergistic interactions of trastuzumab and chemotherapeutic agent treatment, the protein levels of phospho-protein kinase B (pAkt) were determined by Western blotting. We showed that trastuzumab synergizes with the cytotoxic effect of epirubicin in HER2-positive gastric cancer cells. Further investigation showed that the trastuzumab-epirubicin combination decreased the expression of pAkt. Altogether, our results provide preclinical evidence for the optimization of this combination regimen in the treatment of HER2-positive gastric cancer patients.

Response to Trastuzumab Treatment and Number of Cycles ın Her2-Positive Metastatic Gastric Cancer Survival.

Descriptive study. Department of Medical Oncology, Dr. Abdurrahman Yurtaslan Oncology Training and Research Hospital, from January 2012 to December 2019. Medical records of 33 HER2-positive metastatic gastric cancer patients who had received trastuzumab combined with chemotherapy at least 6 cycles and/or followed by maintenance as the first-line treatment were examined.Kaplan-Meier method was used for survival analysis. Log-Rank test was used to compare survival times. The prognostic factors were determined by Cox regression analysis. The median OS was 15.97 months, and the median PFS was 11.11 months. The median OS and PFS were significantly higher in those who demonstrated partial or complete response to trastuzumab combination treatment, and those who received more than 10 cycles of trastuzumab. A Cox regression analysis revealed that the risk of death was 3.18 times higher in patients with stable disease and 0.44 times lower in patients who received more than 10 cycles of trastuzumab as maintenance. The OS time was prolonged when the partial and complete response was obtained with chemotherapy combined with trastuzumab, as well as OS and PFS times were improved with the increasing number of trastuzumab cycles. Thus, it is concluded that the response better than stable disease of trastuzumab treatment and an increased number of cycles predicts improved survival efficiently in patients with HER2-positive metastatic gastric cancer. Key Words:Metastatic gastric cancer, Trastuzumab, Prognosis, Response, Efficiency.

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.

137P - Significant benefit of pyrotinib combined with SHR6390 in patients with multiline-resistant HER2-positive advanced gastric cancer

BackgroundThe aim of the present study was to explore the mechanism underlying the poor efficacy of pyrotinib, propose and validate a strategy for pyrotinib-combined therapy in patients with human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC). MethodsHuman GC cell lines and patient-derived xenograft (PDX) models were used to evaluate the antitumor activity and mechanisms of pyrotinib. One pyrotinib-refractory PDX model was established to explore the potential mechanisms underlying drug resistance, propose an optimal therapeutic strategy, and further validate in a phase I clinical trial (NCT03480256). ResultsPyrotinib exerted strong antitumor activity in HER2-positive GC cells and PDX models via suppressing the activation of the AKT/S6 signaling pathway. In addition, dysregulation of the cell cycle, represented by aberrant activation of the CCND1-CDK4/6-Rb axis, was found in the pyrotinib-refractory PDX model compared with the parental model. Then, combination therapy of pyrotinib with a CDK4/6 inhibitor (SHR6390) was proposed and its strong tumor growth inhibition was observed in the pyrotinib refractory-PDX model. Three HER2-positive GC patients after multiline therapies were subsequently enrolled in our clinical trial treatment with pyrotinib (400 mg/d for 28 days per cycle) combined with SHR6390 (100 mg/d for 21 days per cycle). After two cycles of therapy, two patients achieved a partial response (PR) and one patient achieved decreased stable disease (SD) with a progression-free survival of 120, 199, and 110 d, respectively. The common adverse events included leucopenia (grade 2 to 3), neutropenia (grade 2 to 4), anemia (grade 1 to 3), and thrombocytopenia (grade 1). ConclusionsThis representative translational study suggests that a combination treatment of pyrotinib with SHR6390 may serve as a promising strategy for patients with HER2-positive GC after systematic treatment failure. The optimal drug doses and tolerability of this combination treatment will be explored in future studies. Legal entity responsible for the studyZuhua Chen. FundingThe National Key Research and Development Program of China (No. 2017YFC1308900, 2017YFC0908400). DisclosureAll authors have declared no conflicts of interest.

Abstract 5096: Exploring novel prognostic genetic markers using elastic-net regularization and association rule mining in HER2-negative metastatic gastric cancer patients

Abstract Trastuzumab is the standard of care and has been shown to prolong survival of HER2-positive gastric cancer (GC) patients. However, HER2-positive is present only in about 20% of GC patients, there is a need to explore prognostic genetic markers for 80% of HER2-negative GC patients. The aim of this study was to identify the prognostic markers by elastic-net regularization and association rule mining and evaluate prognosis with selected genetic markers in HER2-negative metastatic GC (mGC) patients. A total of 143 HER2-negative mGC patients who have been treated with first-line chemotherapy in Yonsei Cancer Center, Korea between 2011 and 2018 were retrospectively assessed. Patients were categorized into two groups (responder or non-responder) based on the median progression-free survival (PFS: 7.8 months (95% confidence interval (CI), 6.3 - 8.9)) of the first-line chemotherapy. Targeted sequencing data of patients was obtained from CancerSCANTM and CANCER MASTER, and were analyzed with common variants of two panels. We used combined tools of elastic-net with 1,000 times of re-sampling bootstrap method and association rule mining to filter out and select critical genetic markers distinguishing responder or non-responder groups. To assess prognosis significance of selected genetic markers, we developed prognostic score based on the sum of sub-scores. If the right-hand-side of the rules signifies a responder, the patient is given a value of 0 when applying to the rule and 1 when they do not. PFS were determined by the Kaplan-Meier method and compared using the log-rank test. The 85 candidate genetic markers were selected by elastic-net with 60% of variable inclusion probability. Among the 85 candidate genetic markers, 12 genetic markers involved in 26 rules with lift greater than 1.5 were related to the responder group from association rule mining. The selected 12 genetic markers are included as follows: EGFR/KRAS normal copy number, APOBEC3B deletion, FGFR2/MLH1/PHLPP2/PARP4/SH2B3/BARD1/ALK/GNAS wild type, and NCOA3 mutation. The prognostic scores generated by selected genetic markers were 3, 4 and 5 respectively, and patients with higher scores had significantly poor prognosis than those with lower scores. Median PFS of each score group were 9.8 months (95% CI, 8.8 - 11.6), 7.5 months (95% CI, 5.7 - 8.6), and 5.2 months (95% CI, 1.2 - 6.7) for patients with consecutive scores of 3, 4 and 5 (P=0.017). The combined tool of elastic-net and association rule mining effectively found prognostic genetic markers and can be applied to develop the prognostic scoring system. The results of novel combined tool identified 12 multiple prognostic genetic markers and demonstrated significant survival differences in prognostic scores among HER2-negative mGC patients, although further studies are required. Note: This abstract was not presented at the meeting. Citation Format: Sejung Park, Woo Sun Kwon, Inhye Jeong, Hyun Jeong Kim, Jong Soo Hong, Jaeyoung Kim, Jingmin Che, Chung Mo Nam, Hyun Cheol Chung, Sun Young Rha. Exploring novel prognostic genetic markers using elastic-net regularization and association rule mining in HER2-negative metastatic gastric cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5096.

Abstract 2951: A genome-wide association study identifies five novel genetic markers for trastuzumab-induced cardiotoxicity

Abstract Purpose: Trastuzumab has been administered to HER2-positive breast or gastric cancer patients as an effective treatment, however, the cardiotoxicity is identified as one of the life-threatening side effects. To identify a novel genetic marker(s) determining the risk of trastuzumab-induced cardiotoxicity, we performed a genome-wide association study (GWAS). Experimental Design: We carried out a GWAS using 11 cases (with trastuzumab-induced cardiotoxicity) and 257 controls (showing no sign of trastuzumab-induced cardiotoxicity). Top 100 single nucleotide polymorphisms (SNPs) which revealed smallest P value in GWAS (P = 1.61 x 10-7 -1.97 x 10-4) were further examined using replication samples consisted of 14 cases and 199 controls. Results: The combined analysis of the GWAS and replication study indicated possible association of five loci with trastuzumab-induced cardiotoxicity (chromosome 13q14.3, 4q25, 15q26.3, 17q25.3 and another 15q26.3, Pcombined = 6.00 x 10-6, 8.60 x 10-5, 1.01 x 10-4, 1.07 x 10-4, 1.60 x 10-4, respectively). Furthermore, we developed a risk prediction model for trastuzumab-induced cardiotoxicity, using five SNPs which revealed smallest P value at each locus. The incidence of trastuzumab-induced cardiotoxicity in patients with risk score ≥5 was 42.5% (P =8.69 x 10-15) . This scoring system using five candidate loci could be used to predict the risk of the adverse event before administration of trastuzumab. Conclusion: We identified five novel loci, which could be associated with trastuzumab-induced cardiotoxicity. These findings provide new insights into personalized trastuzumab therapy for patients with HER2-positive cancer. Citation Format: Chihiro Udagawa, Mari Hara, Arata Shimo, Yasuyuki Kojima, Reiko Yoshie, Hisamitsu Zaha, Norie Abe, Tokiwa Motonari, Mikiko Unesoko, Kenji Tamura, Tatsunori Shimoi, Masayuki Yoshida, Teruhiko Yoshida, Hiroshi Okamura, Taisei Mushiroda, Koichiro Tsugawa, Hitoshi Zembutsu. A genome-wide association study identifies five novel genetic markers for trastuzumab-induced cardiotoxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2951.

Integrin β5 in plasma-derived exosomal protein predicting liver-specific metastasis in advanced gastric cancer patients.

e14521 Background: Gastric cancer (GC) is the second leading cause of cancer death in China. Liver metastasis (LM) is a highly frequent event of the advanced GC, and the patients with LM always present dismal prognosis. A predicted factor of LM is urgently established to screen out the population in high risk of LM. Tumor-derived exosomes play critical roles in cancer metastasis process. Exosomes integrin (ITG) αvβ5 is uptake by liver resident cells and linked to LM in cell lines. This study is designed to evaluate the association between exosomes ITG αvβ5 and liver metastasis, especially in HER2 positive gastric cancer. Methods: 74 untreated advanced GC patients with matched blood and tumor tissue samples and clinical features were collected in the study. Exosomal HER2, ITG αv and β5 expression were measured by enzyme-linked immunosorbent assay (ELISA) after the exosomes isolated from plasma. HER2 status of tumor tissue was determined by IHC and/or FISH. Results: Based on HER2 status of tumor tissue, we initially proved the feasibility of detecting HER2 expression from exosome. ROC curves showed the optimum exosomal HER2 expression diagnostic cutoff for HER2 positive patients was 266.38 pg/ml (sensitivity 71.4% and specificity 72.6%). In total, 27 patients were LM and the rest (n = 47) was non-LM. The median expression value of ITG αv and β5 were 57.55 pg/ml and 836.00 pg/ml, respectively. And these two median value were identified as the cutoff value for subsequent analysis, respectively. HER2 expression was merely linked to ITG β5 expression (P = 0.019), not ITG αv (P > 0.050). There was no relationship between ITG αv and LM (P = 0.629), however, ITG β5 expression presented significant association with LM (P = 0.016). We further probed the relationship between ITG and other metastasis. Results showed no correlation between any ITG and other non-liver organic metastases, like lung, bone, ovarian, lymph, and peritoneal metastasis. Besides, ITG β5 expression was also associated with LM in the HER2-positive GC patients. Conclusions: Exosomes might serve as a potential non-invasive diagnostic and screening tool. In clinical samples, ITG β5, not αv, was linked to LM, and might be a valuable biomarker in the use of predicting LM of GC, even in the HER2-positive patients.

Synthetic miR-143 Inhibits Growth of HER2-Positive Gastric Cancer Cells by Suppressing KRAS Networks Including DDX6 RNA Helicase.

Gastric cancer (GC) is one of the most common cancers worldwide. In the clinical setting, the identification of HER2 overexpression in GC was a significant finding, as trastuzumab, an anti-HER2 drug, provides a survival advantage to HER2-positive GC patients. In HER2-postive GC, the dysregulation of PI3K/AKT and MAPK/ERK signaling pathways has been reported, and inhibition of these pathways is an important therapeutic strategy. MiR-143 is known to act as a tumor suppressor in several cancers, such as bladder cancer, breast cancer, colorectal cancer, and gastric cancer. In the current study, we developed a novel chemically-modified miR-143 and explored the functions of this synthetic miR-143 (syn-miR-143) in HER2-positive gastric cancer. The expression level of miR-143 was down-regulated in GC cell lines, including HER2-positive GC cell lines, MKN7, and KATO-III. The ectopic expression of miR-143 in those cell lines suppressed cell growth through systemic silencing of KRAS and its effector signaling molecules, AKT and ERK. Furthermore, syn-miR-143 indirectly down-regulated the expression of HER2, an upstream molecule of KRAS, through silencing DEAD/H-box RNA helicase 6 (DDX6), RNA helicase, which enhanced HER2 protein expression at the translational step in HER2-positive GC cells. These findings suggested that syn-miR-143 acted as a tumor suppressor through the impairment of KRAS networks including the DDX6.

Comparison of HER2 expression by immunohistochemistry and HER2 copy number by digital PCR in tumor tissue during treatment with trastuzumab in the prospective cohort of metastatic HER2-positive gastric cancer patients.

58 Background: Trastuzumab (Tmab) is an active molecular-targeted drug for HER2-positive gastric cancer (GC) patients. HER2 expression is known to change during the treatment of Tmab and HER2 amplification in blood is widely investigated as a new biomarker of the treatment candidate or the monitoring of HER2-target therapy. We evaluated the change of the HER2 expression by immunohistochemistory (IHC) and HER2 copy number by degital PCR during the treatment with Tmab in metastatic HER2-positive GC patients. Methods: Metastatic HER2-positive GC patients treated with Tmab were registered prospectively, and tissues were obtained by biopsy from primary lesions at the following points: (1) pre-treatment, (2) post-treatment, and (3) disease progression during chemotherapy with Tmab. Formalin-fixed paraffin-embedded tissue slides were prepared, and the expression of HER2 expression were scored by IHC and HER2 copy number were evaluated by digital-PCR. Results: Among 20 enrolled patients, HER2 expression was evaluated by IHC in all patients. HER2 copy number was evaluated by digital PCR in 15 patients. A patient was excluded because HER2 expression were not detected by re-evaluation. The median of HER2 copy number of 33 sampling points during the treatment was 6.37 (range: 2.12 - 85.8). The median of HER2 copy number of IHC 3+, IHC 2+, IHC 0-1 were 22.4 (3.37 – 85.8), 2.88 (2.65 – 3.6), 2.37 (2.12 – 3.85), respectively. High level of HER2 copy number was detected in tumor tissues of HER2 IHC 3+ compared with that of IHC≦2+. HER2 expression by IHC was disappeared after treatment of Tmab in 42% of HER2-positive patients. Among these patients, HER2 copy number at pre-treatment were relatively low (2.63 - 3.6). Conclusions: High copy number of HER2 was detected in tumor tissues with HER2 IHC3+ in HER2-positive GC patients during the treatment of Tmab. In addition, low copy number of HER2 in tumor tissues at pre-treatment may be associated with the loss of HER2 expression after treatment of Tmab. Further research by large number of patients to confirm our results is required.

Phase II clinical trial of second-line weekly paclitaxel plus trastuzumab for patients with HER2-positive metastatic gastric cancer

Combination therapy with fluorouracil, platinum, and trastuzumab (Tmab) is the first-line treatment for human epidermal growth factor receptor 2 (HER2)-positive gastric cancer, and there is currently no established second-line therapy. We evaluated the efficacy and safety of weekly paclitaxel plus Tmab as second-line chemotherapy for HER2-positive gastric cancer patients. Eligible patients were older than or equal to 20 years, had histologically confirmed gastric adenocarcinoma that was HER2 positive (immunohistochemistry 3+ or immunohistochemistry 2+ and fluorescence in-situ hybridization positive or dual color in-situ hybridization positive), and had been treated previously with chemotherapy (pretreated or not with Tmab). Patients received weekly paclitaxel plus Tmab as the second-line chemotherapy. The primary endpoint was the overall response rate (ORR; threshold ORR=20% and expected ORR=35%). Twenty-eight patients were enrolled. ORR was 21.4%. The median progression-free survival (PFS) was 4.6 months. The median overall survival (OS) was 9.6 months. No significant differences were observed in ORR, PFS, or OS between the Tmab beyond progression (TBP) group (n=20) and the non-TBP group (n=8). However, in the TBP group, a therapeutic effect was associated with the duration of PFS in the first-line Tmab treatment [≥6 months PFS in the first-line Tmab treatment (n=10) vs. <6 months (n=10); ORR: 40 and 10%, P=0.303, PFS: 6.2 and 2.8 months, P=0.005, OS: 15.8 and 6.5 months, P=0.006, respectively]. Weekly paclitaxel plus Tmab was not superior as second-line chemotherapy for HER2-positive gastric cancer patients, but may be effective for patients who showed better responses to Tmab-combined chemotherapy in the first-line treatment.

Loss of HER2 positivity after anti-HER2 chemotherapy in HER2-positive gastric cancer patients: results of the GASTric cancer HER2 reassessment study 3 (GASTHER3).

Although discordance in HER2 positivity between primary and metastatic lesions is well established, changes in HER2 positivity after anti-HER2 therapy have not been well evaluated in gastric cancer. We aimed to evaluate whether HER2 expression in gastric cancer is affected by trastuzumab therapy. We enrolled 48 HER2-positive advanced gastric cancer patients treated with trastuzumab-containing first-line chemotherapy and had paired biopsies at baseline and after progression. At baseline, HER2 was positive, with immunohistochemistry (IHC) 2+ and in situ hybridization (ISH)+ in five patients, and with IHC 3+ in 43 patients. Fourteen patients (29.1%) exhibited loss of HER2 positivity on post-progression biopsy: 10 with IHC 0 or 1+, and four with IHC 2+/ISH-. HER2 remained positive on second biopsy in 34 patients: four with IHC 2+/ISH+, and 30 with IHC 3+. Median H-scores decreased from 225 to 175 (p = 0.047). HER2 genetic heterogeneity was defined in one of 34 ISH-assessable patients (2.9%) at baseline and seven of 32 (21.9%) at second biopsy. Among 13 patients who received second-line trastuzumab emtansine, three showed HER2-negative conversion; they had no objective response and short progression-free survival (1.2, 1.3, and 3.4months). Patients with stable HER2 status had a 44% response rate and median progression-free survival of 2.7 (0.4-36.8)months. A substantial portion of HER2-positive patients showed HER2-negative conversion with increased HER2 genetic heterogeneity after failure of trastuzumab-containing chemotherapy. Loss of HER2 positivity could be predictive of second-line anti-HER2 treatment, suggesting a need to reexamine HER2 status before initiating second-line anti-HER2 therapy.

Clinical impact of intratumoral HER2 heterogeneity on trastuzumab efficacy in patients with HER2-positive gastric cancer

BackgroundThere is growing interest in the clinical significance of intratumoral HER2 heterogeneity. Its prognostic and predictive impacts on trastuzumab efficacy were demonstrated in breast cancer. However, its clinical significance in gastric cancer is still unclear.MethodsTwenty-eight HER2-positive gastric cancer patients who had gastrectomy prior to trastuzumab-based chemotherapy were consecutively enrolled. Intratumoral HER heterogeneity was evaluated using whole-tissue sections by immunohistochemistry. When all tumor cells overexpressed HER2 protein, the tumor was defined as homogeneously HER2 (Homo-HER2)-positive group. The others were defined as heterogeneously HER2 (Hetero-HER2)-positive group.ResultsThere was no significant difference in clinicopathological features between the two groups. The median progression-free survival (PFS) and overall survival (OS) in the Homo-HER2-positive group were significantly longer than those in the Hetero-HER2-positive group (PFS; 20.0 months [95% CI 17.8–22.2] vs. 6.0 months [95% CI 2.3–9.7]; HR 0.11; 95% CI 0.03–0.41; p < 0.001, OS; not reached vs. 14.0 months [95% CI 11.9–16.1]; HR 0.18; 95% CI 0.06–0.61; p = 0.003). In the multivariate analysis, these associations remained significant both in PFS (HR 0.12; 95% CI 0.03–0.46, p = 0.002) and OS (HR 0.21; 95% CI 0.06–0.72, p = 0.013). With respect to response rate, no statistical difference was found between two groups. However, deeper tumor shrinkage was obtained in the Homo-HER2-positive group compared with the Hetero-HER2-positive group (p = 0.046).ConclusionsIntratumoral HER2 heterogeneity may have robust clinical impact on trastuzumab efficacy in patients with HER2-positive gastric cancer. These findings should be validated by larger independent cohorts and further molecular correlative analyses are warranted.

Establishment of a Patient-derived Xenograft for Development of Personalized HER2-targeting Therapy in Gastric Cancer.

To maximize success rate for development of HER2-targeted therapeutics, patient-derived xenograft (PDX) models reflecting HER2-positive gastric cancer (HER2+ GC) patients were established. GC tissues obtained from surgery of GC patients were implanted into immune-deficient mice, and tumor tissue of HER2+ PDXs were verified of the patient-mimic HER2 expression by immunohistochemistry and explored for the feasibility by testing with Herceptin, the approved therapeutics and novel HER2 antibody therapeutics being developed. We obtained 5 cases of HER2+ GC PDX models reflecting patient's GC tumor, consisting of 2 cases of HER2 3+ and 2 cases of HER2 2+. Novel HER2 antibody displayed significantly improved anti-cancer efficacy in combination with Herceptin. The HER2+ GC PDX models were successfully established to be utilized for preclinical evaluation of HER2-targeting drugs and combined therapies for GC treatment, as an ideal platform of personalized tools for precision therapy.

213P - HGCSG 1201: Phase II study of trastuzumab with irinotecan in HER2-positive metastatic or advanced gastric cancer patients previously treated with trastuzumab

213P - HGCSG 1201: Phase II study of trastuzumab with irinotecan in HER2-positive metastatic or advanced gastric cancer patients previously treated with trastuzumab