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Inhibition of the PI3K pathway in HER2-positive gastric cancer
abstracts
806P
Germline pathogenic mutations in Chinese patients with gastric cancer identified by next-generation sequencing (NGS)
X. Zhang1, J. Zhou2, Z. Zhao3, Y. Zhang3, S. Cai3 1 Department of Gastrointestinal Oncology, Beijing Cancer Hospital, Beijing, China, 2 Department of Gastroenterological Surgery, Peking University People’s Hospital, Beijing, China, 3Medical Department, 3D Medcines Inc, Shanghai, China Background: Gastric cancer (GC) is one of the leading cause of cancer death in China, which is mainly caused by environmental and genetic risk factors. By far, the nature of the genetic factors related to gastric cancer has not been well-studied. The aim of this study was to assess the frequency of germline mutations in Chinese gastric cancer population. Methods: Genomic profiling of DNA was performed through next-generation sequencing (NGS) on tissue or liquid biopsy from patients with gastric cancer between January 01, 2017 and May 07, 2019. Patients with germline pathogenic mutations were identified, and their clinical information were collected. Results: 750 gastric cancer patients were ultimately included for analysis. There were 476 (63.5%) male and 274 (36.5%) female patients. The median age was 61 (range, 2688). A total of 27 (3.6%) pathogenic germline pathogenic mutations were identified in 13 genes from these patients. The mutations fell most frequently in BRCA2 (0.93%), ATM (0.67%), PALB2 (0.4%), CHEK2 (0.27%), and CDH1 (0.27%), which has been previously reported to underlie hereditary diffuse gastric cancer. Of all these mutations, 9 (69.2%) genes lay in the DNA damage repair pathways, including BRCA1, BRCA2, ATM, PALB2, CHEK2, MRE11A, ATR, and two DNA mismatch repair genes, MLH1 and MSH6, the mutation of which usually result in the presence of microsatellite instability (MSI) in tumor tissues. Conclusions: This is the first study to explore the spectrum of pathogenic germline mutations in Chinese patients with gastric cancer. Our study has provided valuable clues for the assessment of the corresponding genetic susceptibility in gastric cancer. Legal entity responsible for the study: Beijing Cancer Hospital. Funding: Has not received any funding. Disclosure: Z. Zhao: Full / Part-time employment: 3D Medicines Inc. Y. Zhang: Full / Part-time employment: 3D Medicines Inc. S. Cai: Full / Part-time employment: 3D Medicines Inc. All other authors have declared no conflicts of interest.
807P
EGFR, ERBB2, ERBB3 and ERBB4 in the tumours and in a panel of HER2-positive GC cell lines (N87, OE19, ESO26 and SNU16). The anti-proliferative response to the PI3K inhibitor copanlisib alone and in combination with the HER2-targeted therapies Tr and lapatinib was assessed in vitro. Results: Patients with HER2-positive GC had significantly poorer overall survival compared to HER2-negative patients (15.9 months vs. 35.7 months; p ¼ 0.0032). PIK3CA, EGFR and ERBB mutations occurred more frequently in HER2-negative tumours than HER2-positive tumours, but had no impact on progression free or overall survival. In vitro OE19 cells were resistant to copanlisib, while all other cell lines were sensitive, independent of PIK3CA mutation status, with IC50s ranging from 23.4nm (N87) to 93.8nm (SNU16). All cell lines except SNU16 were sensitive to lapatinib with IC50s ranging from 0.04mM to 1.5mM. OE19 and SNU16 were resistant to Tr. The combination of lapatinib and copanlisib is synergistic in ESO-26 and OE-19 cells (ED50: 0.8360.19 and 0.8860.13, respectively) and additive in N87 cells (ED50:1.0160.55). The combination of copanlisib and Tr significantly improved growth inhibition compared to either therapy alone in N87, ESO26 and OE19 cells (p < 0.05). Conclusions: Copanlisib is an effective monotherapy in some HER2-positive GC cell lines. Combinations of copanlisib and Tr offer greater benefit than either drug alone, and may restore sensitivity to Tr in cells with intrinsic resistance to Tr. The addition of copanlisib to HER2 targeted therapy warrants further investigation in HER2-positive GC. Legal entity responsible for the study: The authors. Funding: North East Cancer Research and Education Trust (NECRET). Disclosure: All authors have declared no conflicts of interest.
Inhibition of the PI3K pathway in HER2-positive gastric cancer
S. Toomey1, M.J. Mezynski1, A. Farrelly1, P. Armstrong1, J. McAuley1, C. Holohan2, Y.Y. Elamin1, S. Rafee2, J. Workman1, M. Cremona1, L. Grogan3, O.S. Breathnach3, P.G. Morris3, J. Fay4, E. Kay4, B.T. Hennessy3 1 Department of Molecular Medicine, RCSI Molecular Medicine Laboratories, Dublin, Ireland, 2Medical Oncology, St James’s Hospital, Dublin, Ireland, 3Medical Oncology, Beaumont Hospital Cancer Centre, Dublin, Ireland, 4Histopathology, Royal College of Surgeons in Ireland, Dublin, Ireland Background: HER2 is overexpressed in 10-25% of gastric cancers (GCs). The association of PI3K pathway activating mutations with HER2 overexpression, or the impact of aberrant PI3K pathway signalling on response to trastuzumab (Tr) in GC has not been described. In HER2-positive breast cancer, targeting the PI3K pathway can overcome resistance to HER2-targeted therapies; however the role of PI3K inhibitors in sensitizing HER2-positive GCs to Tr or in overcoming Tr resistance is unknown. Methods: Tumour samples from 69 GC patients were stratified into HER2-positive (n ¼ 29) and HER2-negative (n ¼ 40) groups. Mass spectrometry-based genotyping (Agena Bioscience) was used to analyse 105 hotspot somatic mutations in PIK3CA,
v310 | Gastrointestinal Tumours, Non-Colorectal
808P
Investigation on gastric cancer susceptibility genes in Chinese earlyonset diffuse gastric cancer
Y. Feng1, M. Zhang1, X. Xing1, W. Chen1, W. Li1, S. Jia1, L. Su2, Y. Yang2 Center for Molecular Diagnostics, Peking University Cancer Hospital-Beijing Cancer Hospital, Beijing, China, 2Division of Medicine and Research, Genetron Health Gene Technology Co. Ltd, Beijing, China
1
Background: Hereditary diffuse gastric cancer (HDGC) is closely related to germline mutation of CDH1. In addition, potential pathogenic germline variants in other candidate genes were detected in FGC and HDGC families. However, comprehensive genetic profile of HDGC predisposing gene variants in Chinese Familial gastric cancer (FGC) and HDGC patients are yet to be elucidated. Methods: We collected peripheral blood from 28 early-onset DGC patients and from a first degree relative DGC patient who was diagnosed at age of 50. All 29 patients fulfilled IGCLC 2015 criteria for HDGC clinical diagnosis and genetic testing. Genomic DNA was extracted from peripheral blood followed by Whole Exome Sequencing (WES) with average sequencing depth of at least 100X. Gastric ancer predisposing SNV and Indel candidates were filtered based on population allele frequencies in public nucleotide polymorphism databases and corresponding functional impact was predicted by in silico tools. Results: Among previously reported gastric cancer susceptibility genes, CDH1, BRCA2, MAP3K6 expressed the most predisposing SNV and Indel candidates. In addition, a novel splice-site variant, c.2165-1G>A, in CDH1 was detected in a Chinese early-onset HDGC patient who developed ovarian metastasis. Moreover, BCR gene exhibited as the most prevalent gastric cancer predisposing gene with filtered variants primarily enriched in RhoGAP domain. Pathway enrichment analysis showed that the top three predisposing variant candidates were enriched in the following signalling pathway: ECM-receptor interaction (P-Value: 0.001), focal adhesion (P-Value: 0.02) and protein digestion and absorption (P-Value: 0.002). Conclusions: This study suggested that CDH1, BRCA2, MAP3K6 may act as potential gastric cancer susceptibility genes in Chinese early-onset HDGC patients. Further study may be required to investigate the functional role of BCR abnormality, especially in its RhoGAP domain, in the tumorigenesis of gastric cancer. Moreover, to further investigate molecular mechanisms of early-onset gastric cancer, one may consider genes involved in three signalling pathways: ECM-receptor interaction, focal adhesion and protein digestion and absorption. Legal entity responsible for the study: Peking University Cancer Hospital. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.
809P
A correlation analysis between survival rate and the characteristic gene of gastric cancer based on bioinformatics analysis
Y-W. Zhang, Y-J. Liu Laboratory of Clinical Pharmacy, Zhejiang Cancer Hospital, Hangzhou, China Background: Gastric cancer is one of the most common fatal disease worldwide, but its mechanism and therapeutic targets are still unclear. In this study, we have analyzed the differences in gene modules and key pathways in gastric cancer patients, and elaborated the mechanism and effective treatment of gastric cancer with microarray data from the gene expression omnibus (GEO) database.
Volume 30 | Supplement 5 | October 2019
Downloaded from https://academic.oup.com/annonc/article-abstract/30/Supplement_5/mdz247.133/5577460 by guest on 26 October 2019
Results: Patients with M1 GC demonstrated increased CD3þ lymphocytic infiltration of T, PT, O and P tissues. IRI in M1 O was significantly higher than in M0 (1.9560.3 vs 0.760.2), being similar in other tissues. Levels of DN lymphocytes were lower in O of M1, compared to M0 (7.762.5 vs 15.765.6, p 0.05). Contents of NK cells, NKT lymphocytes significantly decreased in O of M1 patients, compared to M0 (3.31.1 vs 14.02.3 and 1.760.5 vs 3.860.8, respectively). Higher levels of NKT lymphocytes were registered in M1 PT, compared to M0 (3.361.1 vs 1.360.4), as well as lower levels of NK cells in T (2.360.9 vs 5.3360.2). Percentage of Treg lymphocytes in P and O were significantly lower in M1 than in M0 (respectively, 6.961.5 vs 12.664.9 and 5.961.3 vs 12.664.9). Higher amount of B lymphocytes was registered in all tissues of M1 patients, compared to M0, maximal in O (13.163.3 vs 3.461.5), T (23.565.1 vs 17.262.3) and P (8.263.4 vs 3.561.2), while in PT it was lower (15.764.2 vs 43.764.5). Conclusions: GC metastasis to the omentum and peritoneum is characterized by a change in their immunological features – a decrease in the tissue level of NK and NKT lymphocytes, a loss in the prevalence of CD3þCD8þ due to an increase in the number of CD3þCD4þ cells, and an increase in the level of CD19 þ (B2) lymphocytes. This probably contributes to the appearance of metastatic lesions in these organs in gastric cancer. Legal entity responsible for the study: The authors. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.
Annals of Oncology
806P
Germline pathogenic mutations in Chinese patients with gastric cancer identified by next-generation sequencing (NGS)
X. Zhang1, J. Zhou2, Z. Zhao3, Y. Zhang3, S. Cai3 1 Department of Gastrointestinal Oncology, Beijing Cancer Hospital, Beijing, China, 2 Department of Gastroenterological Surgery, Peking University People’s Hospital, Beijing, China, 3Medical Department, 3D Medcines Inc, Shanghai, China Background: Gastric cancer (GC) is one of the leading cause of cancer death in China, which is mainly caused by environmental and genetic risk factors. By far, the nature of the genetic factors related to gastric cancer has not been well-studied. The aim of this study was to assess the frequency of germline mutations in Chinese gastric cancer population. Methods: Genomic profiling of DNA was performed through next-generation sequencing (NGS) on tissue or liquid biopsy from patients with gastric cancer between January 01, 2017 and May 07, 2019. Patients with germline pathogenic mutations were identified, and their clinical information were collected. Results: 750 gastric cancer patients were ultimately included for analysis. There were 476 (63.5%) male and 274 (36.5%) female patients. The median age was 61 (range, 2688). A total of 27 (3.6%) pathogenic germline pathogenic mutations were identified in 13 genes from these patients. The mutations fell most frequently in BRCA2 (0.93%), ATM (0.67%), PALB2 (0.4%), CHEK2 (0.27%), and CDH1 (0.27%), which has been previously reported to underlie hereditary diffuse gastric cancer. Of all these mutations, 9 (69.2%) genes lay in the DNA damage repair pathways, including BRCA1, BRCA2, ATM, PALB2, CHEK2, MRE11A, ATR, and two DNA mismatch repair genes, MLH1 and MSH6, the mutation of which usually result in the presence of microsatellite instability (MSI) in tumor tissues. Conclusions: This is the first study to explore the spectrum of pathogenic germline mutations in Chinese patients with gastric cancer. Our study has provided valuable clues for the assessment of the corresponding genetic susceptibility in gastric cancer. Legal entity responsible for the study: Beijing Cancer Hospital. Funding: Has not received any funding. Disclosure: Z. Zhao: Full / Part-time employment: 3D Medicines Inc. Y. Zhang: Full / Part-time employment: 3D Medicines Inc. S. Cai: Full / Part-time employment: 3D Medicines Inc. All other authors have declared no conflicts of interest.
807P
EGFR, ERBB2, ERBB3 and ERBB4 in the tumours and in a panel of HER2-positive GC cell lines (N87, OE19, ESO26 and SNU16). The anti-proliferative response to the PI3K inhibitor copanlisib alone and in combination with the HER2-targeted therapies Tr and lapatinib was assessed in vitro. Results: Patients with HER2-positive GC had significantly poorer overall survival compared to HER2-negative patients (15.9 months vs. 35.7 months; p ¼ 0.0032). PIK3CA, EGFR and ERBB mutations occurred more frequently in HER2-negative tumours than HER2-positive tumours, but had no impact on progression free or overall survival. In vitro OE19 cells were resistant to copanlisib, while all other cell lines were sensitive, independent of PIK3CA mutation status, with IC50s ranging from 23.4nm (N87) to 93.8nm (SNU16). All cell lines except SNU16 were sensitive to lapatinib with IC50s ranging from 0.04mM to 1.5mM. OE19 and SNU16 were resistant to Tr. The combination of lapatinib and copanlisib is synergistic in ESO-26 and OE-19 cells (ED50: 0.8360.19 and 0.8860.13, respectively) and additive in N87 cells (ED50:1.0160.55). The combination of copanlisib and Tr significantly improved growth inhibition compared to either therapy alone in N87, ESO26 and OE19 cells (p < 0.05). Conclusions: Copanlisib is an effective monotherapy in some HER2-positive GC cell lines. Combinations of copanlisib and Tr offer greater benefit than either drug alone, and may restore sensitivity to Tr in cells with intrinsic resistance to Tr. The addition of copanlisib to HER2 targeted therapy warrants further investigation in HER2-positive GC. Legal entity responsible for the study: The authors. Funding: North East Cancer Research and Education Trust (NECRET). Disclosure: All authors have declared no conflicts of interest.
Inhibition of the PI3K pathway in HER2-positive gastric cancer
S. Toomey1, M.J. Mezynski1, A. Farrelly1, P. Armstrong1, J. McAuley1, C. Holohan2, Y.Y. Elamin1, S. Rafee2, J. Workman1, M. Cremona1, L. Grogan3, O.S. Breathnach3, P.G. Morris3, J. Fay4, E. Kay4, B.T. Hennessy3 1 Department of Molecular Medicine, RCSI Molecular Medicine Laboratories, Dublin, Ireland, 2Medical Oncology, St James’s Hospital, Dublin, Ireland, 3Medical Oncology, Beaumont Hospital Cancer Centre, Dublin, Ireland, 4Histopathology, Royal College of Surgeons in Ireland, Dublin, Ireland Background: HER2 is overexpressed in 10-25% of gastric cancers (GCs). The association of PI3K pathway activating mutations with HER2 overexpression, or the impact of aberrant PI3K pathway signalling on response to trastuzumab (Tr) in GC has not been described. In HER2-positive breast cancer, targeting the PI3K pathway can overcome resistance to HER2-targeted therapies; however the role of PI3K inhibitors in sensitizing HER2-positive GCs to Tr or in overcoming Tr resistance is unknown. Methods: Tumour samples from 69 GC patients were stratified into HER2-positive (n ¼ 29) and HER2-negative (n ¼ 40) groups. Mass spectrometry-based genotyping (Agena Bioscience) was used to analyse 105 hotspot somatic mutations in PIK3CA,
v310 | Gastrointestinal Tumours, Non-Colorectal
808P
Investigation on gastric cancer susceptibility genes in Chinese earlyonset diffuse gastric cancer
Y. Feng1, M. Zhang1, X. Xing1, W. Chen1, W. Li1, S. Jia1, L. Su2, Y. Yang2 Center for Molecular Diagnostics, Peking University Cancer Hospital-Beijing Cancer Hospital, Beijing, China, 2Division of Medicine and Research, Genetron Health Gene Technology Co. Ltd, Beijing, China
1
Background: Hereditary diffuse gastric cancer (HDGC) is closely related to germline mutation of CDH1. In addition, potential pathogenic germline variants in other candidate genes were detected in FGC and HDGC families. However, comprehensive genetic profile of HDGC predisposing gene variants in Chinese Familial gastric cancer (FGC) and HDGC patients are yet to be elucidated. Methods: We collected peripheral blood from 28 early-onset DGC patients and from a first degree relative DGC patient who was diagnosed at age of 50. All 29 patients fulfilled IGCLC 2015 criteria for HDGC clinical diagnosis and genetic testing. Genomic DNA was extracted from peripheral blood followed by Whole Exome Sequencing (WES) with average sequencing depth of at least 100X. Gastric ancer predisposing SNV and Indel candidates were filtered based on population allele frequencies in public nucleotide polymorphism databases and corresponding functional impact was predicted by in silico tools. Results: Among previously reported gastric cancer susceptibility genes, CDH1, BRCA2, MAP3K6 expressed the most predisposing SNV and Indel candidates. In addition, a novel splice-site variant, c.2165-1G>A, in CDH1 was detected in a Chinese early-onset HDGC patient who developed ovarian metastasis. Moreover, BCR gene exhibited as the most prevalent gastric cancer predisposing gene with filtered variants primarily enriched in RhoGAP domain. Pathway enrichment analysis showed that the top three predisposing variant candidates were enriched in the following signalling pathway: ECM-receptor interaction (P-Value: 0.001), focal adhesion (P-Value: 0.02) and protein digestion and absorption (P-Value: 0.002). Conclusions: This study suggested that CDH1, BRCA2, MAP3K6 may act as potential gastric cancer susceptibility genes in Chinese early-onset HDGC patients. Further study may be required to investigate the functional role of BCR abnormality, especially in its RhoGAP domain, in the tumorigenesis of gastric cancer. Moreover, to further investigate molecular mechanisms of early-onset gastric cancer, one may consider genes involved in three signalling pathways: ECM-receptor interaction, focal adhesion and protein digestion and absorption. Legal entity responsible for the study: Peking University Cancer Hospital. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.
809P
A correlation analysis between survival rate and the characteristic gene of gastric cancer based on bioinformatics analysis
Y-W. Zhang, Y-J. Liu Laboratory of Clinical Pharmacy, Zhejiang Cancer Hospital, Hangzhou, China Background: Gastric cancer is one of the most common fatal disease worldwide, but its mechanism and therapeutic targets are still unclear. In this study, we have analyzed the differences in gene modules and key pathways in gastric cancer patients, and elaborated the mechanism and effective treatment of gastric cancer with microarray data from the gene expression omnibus (GEO) database.
Volume 30 | Supplement 5 | October 2019
Downloaded from https://academic.oup.com/annonc/article-abstract/30/Supplement_5/mdz247.133/5577460 by guest on 26 October 2019
Results: Patients with M1 GC demonstrated increased CD3þ lymphocytic infiltration of T, PT, O and P tissues. IRI in M1 O was significantly higher than in M0 (1.9560.3 vs 0.760.2), being similar in other tissues. Levels of DN lymphocytes were lower in O of M1, compared to M0 (7.762.5 vs 15.765.6, p 0.05). Contents of NK cells, NKT lymphocytes significantly decreased in O of M1 patients, compared to M0 (3.31.1 vs 14.02.3 and 1.760.5 vs 3.860.8, respectively). Higher levels of NKT lymphocytes were registered in M1 PT, compared to M0 (3.361.1 vs 1.360.4), as well as lower levels of NK cells in T (2.360.9 vs 5.3360.2). Percentage of Treg lymphocytes in P and O were significantly lower in M1 than in M0 (respectively, 6.961.5 vs 12.664.9 and 5.961.3 vs 12.664.9). Higher amount of B lymphocytes was registered in all tissues of M1 patients, compared to M0, maximal in O (13.163.3 vs 3.461.5), T (23.565.1 vs 17.262.3) and P (8.263.4 vs 3.561.2), while in PT it was lower (15.764.2 vs 43.764.5). Conclusions: GC metastasis to the omentum and peritoneum is characterized by a change in their immunological features – a decrease in the tissue level of NK and NKT lymphocytes, a loss in the prevalence of CD3þCD8þ due to an increase in the number of CD3þCD4þ cells, and an increase in the level of CD19 þ (B2) lymphocytes. This probably contributes to the appearance of metastatic lesions in these organs in gastric cancer. Legal entity responsible for the study: The authors. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.
Annals of Oncology