Prognostic impact of KRAS mutant type and MET amplification in metastatic and recurrent gastric cancer patients treated with first-line S-1 plus cisplatin chemotherapy

KRAS mutation as a predictor of insufficient trastuzumab efficacy and poor prognosis in HER2-positive advanced gastric cancer

PURPOSE

Although RAS and PIK3CA mutations have been associated with resistance to anti-EGFR antibody in colorectal cancer or trastuzumab in breast cancer, their implications for trastuzumab resistance in HER2-positive advanced gastric cancer (AGC) remains unclear. We aimed to assess the relationship between trastuzumab efficacy and mutation status in the HER family signaling pathway.

METHODS

This study retrospectively evaluated patients with HER2-positive AGC who received first-line trastuzumab-containing chemotherapy between March 2011 and November 2015. Multiplex genotyping, including KRAS, NRAS, PIK3CA, and BRAF, was then performed using the Luminex Assay, after which KRAS amplification was measured using quantitative real-time reverse transcription-polymerase chain reaction. Thereafter, the association between genetic alterations and clinical outcomes were evaluated.

RESULTS

KRAS mutation (MT) was detected in 6 of 77 patients (7.8%), whereas KRAS amplification was found in 15 of 67 patients (22%). No mutations in NRAS, PIK3CA, or BRAF were identified. The KRAS MT group showed significantly worse response rates (16.7% vs. 66.2%, P = 0.016), progression-free survival [median, 4.8 vs. 11.6 months; hazard ratio (HR), 3.95; 95% CI, 1.60-9.76; P = 0.0029], and overall survival (11.5 vs. 23.6 months; HR, 3.80; 95% CI, 1.56-9.28; P = 0.033) compared to the KRAS wild-type group. KRAS amplification had no effect on clinical outcomes.

CONCLUSION

KRAS mutation was an independent prognostic factor for poor survival and might predict insufficient trastuzumab efficacy, whereas KRAS amplification showed no prognostic significance during trastuzumab treatment. Further investigations are warranted to confirm the predictive value of KRAS status in HER2-positive AGC.

MET deletion is a frequent event in gastric/gastroesophageal junction/esophageal cancer: a cross-sectional analysis of gene status and signal distribution in 1,580 patients

BACKGROUND

MET gene aberrations are found in several human cancers including gastric, ovarian and lung. In a large multinational cohort of patients with gastric/gastroesophageal junction/esophageal (G/GEJ/E) adenocarcinoma we assessed the MET status with respect to amplification and deletion and correlate the results with the phenotypical gene signal distribution pattern.

METHODS

Tissue specimens from 1,580 patients were analyzed using a novel fluorescence in situ hybridization (FISH) assay employing a MET/CEN-7 IQFISH Probe Mix. MET amplification and deletions were defined as a MET/CEN-7 ratio ≥2.0 and a MET/CEN-7 ratio <0.8, respectively. Furthermore, the link between the MET gene status and the phenotypical signal distribution was investigated.

RESULTS

The prevalence of MET amplification and deletions was found to be 7.2% and 8.7%, respectively. Significant differences were observed with regard to geographic regions and sex. The Asian population had the highest percentage of MET amplification (9.4%) and the lowest percentage of deletions (3.2%). MET deletions was found more frequently among males (10.1%) compared to females (5.3%) and in esophagus (17.6%) compared to the stomach (5.7%). More than 50% of the patients who harbored MET gene amplification had a heterogeneous distribution of the FISH signals. Patients with a focal signal distribution were solely to be found among the MET amplified population. MET deletion were mainly observed in the group of patients with a homogenous signal distribution.

CONCLUSIONS

The screening data from this cross-sectional study showed that MET deletion and amplification are frequent events in G/GEJ/E cancer, which are linked to different phenotypical signal distribution patterns. The role of MET deletion in relation to tumor development is not fully understood but it is likely to play a role in the oncogenic transformation of the cells.

Prognostic Biomarkers in Early-stage Gastric Adenocarcinoma Treated With Adjuvant Chemoradiotherapy

BACKGROUND/AIM

Early-stage gastric cancer has a high risk of recurrence, despite trimodality therapy with surgery, chemotherapy and radiation. To improve patient selection for adjuvant chemoradiotherapy, we evaluated the prognostic significance of immunohistochemical and genetic biomarkers in patients with resected gastric adenocarcinoma.

PATIENTS AND METHODS

Tumors from 119 patients were subjected to immunohistochemistry for 12 protein biomarkers, as well as next-generation sequencing. Clinical and biomarker data were available for 91 patients.

RESULTS

EBV-positive tumors and tumors with mutations had higher intratumoral CD8 tumor-infiltrating lymphocyte density (p=0.009 and p=0.017, respectively). PIK3CA mutations were correlated with VEGFA overexpression (p=0.042), while KRAS mutations and HER2 expression were mutually exclusive (p=0.036). PTEN expression univariately confirmed longer overall survival (HR=0.27; p=0.046), while there was a trend between the presence of KRAS mutations and inferior disease-free and overall survival.

CONCLUSION

PTEN protein expression and KRAS mutations may predict disease outcome in early-stage gastric cancer. These results need to be further validated in larger cohorts.

Genetic profiling of somatic alterations by Oncomine Focus Assay in Korean patients with advanced gastric cancer

Gastric cancer is one of the leading causes of cancer-associated death; however, analysis of its molecular and clinical characteristics has been complicated by its histological and etiological heterogeneity. The present study aimed to estimate somatic mutation profiling in gastric cancer. To do so, targeted next-generation sequencing (NGS) was performed with the Oncomine Focus Assay to compare the clinicopathological characteristics with the mutation profiles in 50 patients with advanced gastric cancer (AGC). Among the 35 hotspot genes and 19 genes for copy number variations (CNVs), 18 single nucleotide variants (SNVs) or small insertions and deletions (14 missense and four frameshift mutations), and 10 amplifications were identified. To examine the association between mutation profiles and clinicopathological characteristics, each element of the clinicopathological characteristics was categorized into three groups: No alteration, PI3K catalytic subunit α (PIK3CA) alterations and alterations other than PIK3CA. Fisher's exact test identified no statistical differences between the clinicopathological characteristics, with the exception of the Tumor-Node-Metastasis (TNM) T stage between the three groups. Cases of AGC with somatic alterations but no PIK3CA exhibited a significant difference in the TNM T stage compared with those with no alterations or PIK3CA alterations (P=0.044). In addition, AGC with PIK3CA alterations was categorized by Lauren's classification to the intestinal type only. The distribution of Lauren's classification in AGC with PIK3CA alterations was statistically different compared with AGC with alterations other than PIK3CA (P=0.028), but not compared with AGC with no alterations (P=0.076). In conclusion, the present study demonstrated a molecular profiling approach that identified potential molecular classifications for gastric cancer and suggested a framework for precision medicine in AGC.

Clinical significance of MET gene amplification in metastatic or locally advanced gastric cancer treated with first-line fluoropyrimidine and platinum combination chemotherapy

Objective

To investigate the clinical significance of MET gene amplification in patients with gastric cancer in the palliative setting.

Methods

MET amplification was assessed using fluorescence in situ hybridization (FISH) in 50 patients and quantitative polymerase chain reaction (qPCR) in 326 patients; 259 patients treated with first-line fluoropyrimidine and platinum were included for survival analysis.

Results

The results of FISH and qPCR indicated that the c-MET/CEP7 ratio was correlated with gene copy number. The optimal cutoff value for the copy number using qPCR to detect MET gene amplification with FISH was 5 (κ=0.778, P<0.001). Twenty-one out of 326 patients (6.4%) were identified asMET amplification with a copy number of >5 detected by qPCR. MET-amplified gastric cancer was associated with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of ≥2 (33.3% vs. 10.5% P=0.007), peritoneal metastasis (76.2% vs. 46.2%, P=0.008), and elevated bilirubin levels (28.6% vs. 7.3%, P=0.006). The median overall survival (OS) and progression-free survival (PFS) were 11.9 and 5.6 months, respectively. MET-amplified gastric cancer was not associated with survival outcomes [hazard ratio (HR)=0.68, 95% confidence interval (95% CI): 0.35−1.32, P=0.254 for PFS; HR=0.68, 95% CI: 0.35−1.32, P=0.251 for OS].

Conclusions

qPCR can be used to detect MET gene amplification. MET amplification was not a predictor of poor prognosis in patients with metastatic or unresectable gastric cancer.

Crizotinib-resistant MET mutations in gastric cancer patients are sensitive to type II tyrosine kinase inhibitors

Aim: Crizotinib has been used to counter MET amplification in different human malignancies. However, transient responses were observed in some patients with rapid acquisition of resistant mutations in MET. Materials & methods: MET mutations stably expressed Ba/F3 cell lines were used for IC₅₀ detection. Signaling pathway analysis was done using 293T cell line. Results: Four MET mutations conferred resistance to crizotinib with sustained activation of downstream signaling pathways of MET. On the other hand, the four MET mutations displayed different response to type II tyrosine kinase inhibitors with variable deterioration of the downstream signals. Conclusion: This study suggested that patients carrying MET V1092L, D1228G or Y1230H mutations could benefit from type II tyrosine kinase inhibitor treatment, but not patients with G1163R or D1228Y/N mutations.

Prognostic impact of fibroblast growth factor receptor 2 gene amplification in patients receiving fluoropyrimidine and platinum chemotherapy for metastatic and locally advanced unresectable gastric cancers

Although Fibroblast growth factor receptor (FGFR) 2 gene amplification and its prognostic significance have been reported in resectable gastric cancers, information on these features remains limited in the metastatic setting. The presence of FGFR2 amplification was assessed in formalin-fixed, paraffin-embedded tissues using a quantitative PCR-based gene copy number assay with advanced gastric cancer cohorts. A total of 327 patients with tumor portion of ≥70% were analyzed for clinical features. Among these patients, 260 who received first-line fluoropyrimidine and platinum chemotherapy were analyzed for survival.Sixteen of 327 patients (4.9%) exhibited FGFR2 amplification. The amplification group showed associations with age <65 years, Borrmann type 4 disease, poor performance status, poorly differentiated histology, extra-abdominal lymph node metastases, and bone metastases. The median overall survival (OS) and progression-free survival (PFS) were found to be 12.7 and 5.8 months, respectively. In univariate analysis, PFS did not differ between amplification and no amplification groups (hazard ratio [HR]=1.34, 95% confidence interval [CI]: 0.78-2.31, p=0.290), although the OS was significantly shorter in the amplification group (HR=1.92, 95% CI: 1.13-3.26, p=0.015). However, multivariate analysis indicated that FGFR2 amplification was not an independent prognostic factor for OS (HR=1.42, 95% CI: 0.77-2.61, p=0.261).Although FGFR2 amplification is associated with poorer OS, it does not appear to be an independent prognostic predictor in patients with advanced gastric cancer treated with palliative fluoropyrimidine and platinum chemotherapy.

Detection of MET amplification in gastroesophageal tumor specimens using IQFISH

BACKGROUND

The gene mesenchymal epithelial transition factor (MET) is a proto-oncogene that encodes a transmembrane receptor with intrinsic tyrosine kinase activity known as Met or cMet. MET is found to be amplified in several human cancers including gastroesophageal cancer.

METHODS

Here we report the MET amplification prevalence data from 159 consecutive tumor specimens from patients with gastric (G), gastroesophageal junction (GEJ) and esophageal (E) adenocarcinoma, using a novel fluorescence in situ hybridization (FISH) assay, MET/CEN-7 IQFISH Probe Mix [an investigational use only (IUO) assay]. MET amplification was defined as a MET/CEN-7 ratio ≥2.0. Furthermore, the link between the MET signal distribution and amplification status was investigated.

RESULTS

The prevalence of MET amplification was found to be 6.9%. The FISH assay demonstrated a high inter-observer reproducibility. The inter-observer results showed a 100% overall agreement with respect to the MET status (amplified/non-amplified). The inter-observer CV was estimated to 11.8% (95% CI: 10.2-13.4). For the signal distribution, the inter-observer agreement was reported to be 98.7%. We also report an association of MET amplification and a unique signal distribution pattern in the G/GEJ/E tumor specimens. We found that the prevalence of MET amplification was markedly higher in tumors specimens with a heterogeneous (66.7%) versus homogeneous (2.0%) signal distribution. Furthermore, specimens with a heterogeneous signal distribution had a statically significantly higher median MET/CEN-7 ratio (2.35 versus 1.04; P<0.0001).

CONCLUSIONS

The novel FISH assay showed a high inter-observer reproducibility both with respect to amplification status and signal distribution. Based on the finding in the study it is suggested that MET amplification mainly is associated with tumor cells that is represented by a heterogonous growth pattern.

Phase I dose-escalation study of the c-Met tyrosine kinase inhibitor SAR125844 in Asian patients with advanced solid tumors, including patients with MET-amplified gastric cancer

SAR125844 is a potent and selective inhibitor of the c-Met kinase receptor. This was an open-label, phase I, multicenter, dose-escalation, and dose-expansion trial of SAR125844 in Asian patients with solid tumors, a subgroup of whom had gastric cancer and MET amplification (NCT01657214). SAR125844 was administered by intravenous infusion (260-570 mg/m2) on days 1, 8, 15, and 22 of each 28-day cycle. Objectives were to determine the maximum tolerated dose (MTD) and to evaluate SAR125844 safety and pharmacokinetic profile. Antitumor activity was also assessed. Of 38 patients enrolled (median age 64.0 years), 22 had gastric cancer, including 14 with MET amplification. In the dose-escalation cohort (N = 19; unselected population, including three patients with MET-amplification [two with gastric cancer and one with lung cancer]), the MTD was not reached, and the recommended dose was established at 570 mg/m2. Most frequent treatment-emergent adverse events (AEs) were nausea (36.8%), vomiting (34.2%), decreased appetite (28.9%), and fatigue or asthenia, constipation, and abdominal pains (each 21.1%); none appeared to be dose-dependent. Grade ≥ 3 AEs were observed in 39.5% of patients and considered drug-related in 7.9%. SAR125844 exposure increased slightly more than expected by dose proportionality; dose had no significant effect on clearance. No objective responses were observed in the dose-escalation cohort, with seven patients (three gastric cancer, two colorectal cancer, one breast cancer, and one with cancer of unknown primary origin) having stable disease. Modest antitumor activity was observed at 570 mg/m2 in the dose-expansion cohort, comprising patients with MET-amplified tumors (N = 19). Two gastric cancer patients had partial responses, seven patients had stable disease (six gastric cancer and one kidney cancer), and 10 patients had progressive disease. Single-agent SAR125844 administered up to 570 mg/m2 has acceptable tolerability and modest antitumor activity in patients with MET-amplified gastric cancer.

Liver metastases from gastric carcinoma: A Case report and review of the literature

Gastric carcinoma (GC) is the fifth most common malignancy worldwide but the third leading cause of cancer death, and surgery remains the only curative treatment option. Prognosis of patients with liver metastases from gastric carcinoma (LMGC) is poor, and the optimal treatment of metastatic gastric cancer remains a matter of debate. In 2002, a 53-year-old male patient with GC and synchronous oligometastatic lesion in liver VIII segment underwent a total gastrectomy combined with metastasectomy. The pathologic diagnosis was stage IV gastric adenocarcinoma (pT3N2M1), which was treated with adjuvant chemotherapy (cisplatin, epirubicin, leucovorin, and 5-fluorouracil). In 2012, abdominal ultrasound and percutaneous liver biopsy revealed recurrence of the metastasis in the right liver lobe. Progression of the disease was observed after palliative chemotherapy (epirubicin, oxaliplatin, and capecitabine). Nevertheless, an extended right hemihepatectomy, with excision of segments 1, 4A, 5, 6, 7, and 8, was still performed. Pathologic examination confirmed large KRAS- and HER2-negative LMGC. The patient is alive and free of disease 47 months after the repeated hepatectomy and 13 years after removal of the primary GC and synchronous liver metastasis. Based on review of 27 articles, 5-year overall survival rate following gastrectomy and liver metastasectomy may reach 60%, with median survival time up to 74 months. Although the combination of aggressive surgical approach with systemic therapy for LMGC is controversial, it may allow favorable outcome. Careful selection of patients based on evaluable predictive factors for R0 surgical resection of both primary tumor and liver metastases can lead to cure, as shown in our case presentation, where a 10-year relapse-free survival was observed, followed by successful repeated hepatectomy due to liver metastases.

Progression inference for somatic mutations in cancer

Computational methods were employed to determine progression inference of genomic alterations in commonly occurring cancers. Using cross-sectional TCGA data, we computed evolutionary trajectories involving selectivity relationships among pairs of gene-specific genomic alterations such as somatic mutations, deletions, amplifications, downregulation, and upregulation among the top 20 driver genes associated with each cancer. Results indicate that the majority of hierarchies involved TP53, PIK3CA, ERBB2, APC, KRAS, EGFR, IDH1, VHL, etc. Research into the order and accumulation of genomic alterations among cancer driver genes will ever-increase as the costs of nextgen sequencing subside, and personalized/precision medicine incorporates whole-genome scans into the diagnosis and treatment of cancer.

Concurrent MET copy number gain and KRAS mutation is a poor prognostic factor in pancreatobiliary subtype ampullary cancers

Hepatocyte growth factor (HGF) and MET are candidates of targeted therapies for cancer patients. Although MET and HGF are commonly expressed in biliary tract cancers, their expression and gene copy number status and their association with KRAS mutations have not been investigated in pancreatobiliary-type ampullary adenocarcinomas (A-ACs), one of the aggressive periampullary cancers. MET and HGF expressions and MET copy number status were examined by performing immunohistochemistry (IHC) and silver in situ hybridization (SISH) in 62 surgically resected, paraffin-embedded tumors, respectively. High MET and HGF protein expressions were detected in 24 (38.7%) and 15 (24.2%) tumors. High MET expression was associated with KRAS mutation. However, there were no associations of high MET/HGF expression alone with other clinicopathological feature or survival. MET SISH positivity was detected in 19 tumors (30.6%), where 84.2% were due to high trisomy or polysomy and only 3 cases (15.8%) were MET gene amplification. The overall MET protein overexpression was well correlated with MET SISH positivity. The concurrent MET SISH positivity and KRAS mutation, not each alone, was an independent poor prognostic factor of disease-free survival only in pancreatobiliary subtype of A-ACs, but not in intestinal subtype. Concurrent MET SISH positivity and KRAS mutation may predict a high risk of recurrence in pancreatobiliary subtype of A-ACs, indicating those markers could be potent candidates for a new therapeutic target in this cancer type. MET IHC can be used as a reliable tool screening for MET copy number status in ampullary cancers.