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BackgroundThe human leukocyte antigen class I (HLA-I) genotype has been linked with differential immune responses to infectious disease and cancer. However, the clinical relevance of germline HLA-mediated immunity in gastrointestinal (GI) cancer remains elusive.MethodsThis study retrospectively analyzed the genomic profiling data from 84 metastatic GI cancer patients treated with immune checkpoint blockade (ICB) recruited from Peking University Cancer Hospital (PUCH). A publicly available dataset from the Memorial Sloan Kettering (MSK) Cancer Center (MSK GI cohort) was employed as the validation cohort. For the PUCH cohort, we performed HLA genotyping by whole exome sequencing (WES) analysis on the peripheral blood samples from all patients. Tumor tissues from 76 patients were subjected to WES analysis and immune oncology-related RNA profiling. We studied the associations of two parameters of germline HLA as heterozygosity and evolutionary divergence (HED, a quantifiable measure of HLA-I evolution) with the clinical outcomes of patients in both cohorts.ResultsOur data showed that neither HLA heterozygosity nor HED at the HLA-A/HLA-C locus correlated with the overall survival (OS) in the PUCH cohort. Interestingly, in both the PUCH and MSK GI cohorts, patients with high HLA-B HED showed a better OS compared with low HLA-B HED subgroup. Of note, a combinatorial biomarker of HLA-B HED and tumor mutational burden (TMB) may better stratify potential responders. Furthermore, patients with high HLA-B HED were characterized with a decreased prevalence of multiple driver gene mutations and an immune-inflamed phenotype.ConclusionsOur results unveil how HLA-B evolutionary divergence influences the ICB response in patients with GI cancers, supporting its potential utility as a combinatorial biomarker together with TMB for patient stratification in the future.

Purpose RC48 contains the novel humanized anti-HER2 antibody hertuzumab conjugated to MMAE via a cleavable linker. A phase I study was initiated to evaluate the toxicity, MTD, PK, and antitumor activity of RC48 in patients with HER2-overexpressing locally advanced or metastatic solid carcinomas, particularly gastric cancer. Patients and methods This was a 2-part phase I study. Successive cohorts of patients received escalating doses of RC48 (0.1 mg/kg, 0.5 mg/kg, 1.0 mg/kg, 2.0 mg/kg, 2.5 mg/kg, and 3.0 mg/kg). Dose expansion proceeded at the dose of 2.0 mg/kg Q2W. The efficacy and safety set included all patients who received at least one dose of RC48. Results Fifty-seven patients were enrolled, the MTD was unavailable due to termination of 3.0 mg/kg cohort; 2.5 mg/kg Q2W was declared the RP2D. RC48 was well tolerated, the most frequent grade 3 or worse TRAEs included neutropenia (19.3%), leukopenia (17.5%), hypoesthesia (14.0%), and increased conjugated blood bilirubin (8.8%). Four deaths occurred during the whole study, three of which were believed to be related to RC48. Overall, ORR and DCR were 21.0% (12/57) and 49.1% (28/57). Notably, patients who were HER2 IHC2+/FISH- responded similarly to those who were IHC2+/FISH+ and IHC3+, with ORRs of 35.7% (5/14), 20% (2/10), and 13.6% (3/22), respectively. In patients who were pretreated with HER2-targeted drugs, RC48 also showed promising efficacy, with ORR of 15.0% (3/20) and DCR of 45.0% (9/20). Conclusion RC48 was well tolerated and showed promising antitumor activity in HER2-positive solid tumors, including gastric cancer with HER2 IHC 2+/FISH- status. Clinical trial information NCT02881190.

The association between genetic variations and immunotherapy benefit has been widely recognized, while such evidence in gastrointestinal cancer remains limited. We analyzed the genomic profile of 227 immunotherapeutic gastrointestinal cancer patients treated with immunotherapy, from the Memorial Sloan Kettering (MSK) Cancer Center cohort. A gastrointestinal immune prognostic signature (GIPS) was constructed using LASSO Cox regression. Based on this signature, patients were classified into two subgroups with distinctive prognoses (p N = 54) and Peking University Cancer Hospital cohort (N = 92). Multivariate analysis revealed that the GIPS was an independent prognostic biomarker. Notably, the GIPS-high tumor was indicative of a T-cell-inflamed phenotype and immune activation. The findings demonstrated that GIPS was a powerful predictor of immunotherapeutic survival in gastrointestinal cancer and may serve as a potential biomarker guiding immunotherapy treatment decisions.

ObjectiveEmerging evidence showed that immune checkpoint inhibitors (ICIs) lead to hyperprogressive disease (HPD) in a small proportion of patients. There is no well-recognized standard for the evaluation of HPD. Comprehensive exploration of HPD definition system in gastrointestinal cancer treated with ICI is lacking to date.MethodsA total of 126 patients with advanced or metastatic gastrointestinal cancer treated with ICI monotherapy were analyzed. Seven definitions of HPD were defined with tumor growth kinetics (TGK) or tumor growth rate (TGR) by including new lesions or not, and with different cutoffs. Incidence and performance of different criteria were compared. Clinicopathologic characteristics and baseline genomic variations associated with HPD were also explored.ResultsTumor growth kinetics ratio of more than two fold that incorporated new lesions into calculation of HPD outperformed other definitions by successfully stratifying 14 patients (11.1%) with both accelerated disease progression (median PFS, 1.62 versus 1.93 months; hazard ratio, 1.85; 95% CI, 0.98 to 3.48; P = 0.059) and worse overall survival (median OS, 3.97 versus 10.23 months; hazard ratio, 2.30; 95% CI, 1.11 to 4.78; P = 0.021). Baseline genomic alterations in circulating tumor DNA, including SMARCA2, MSH6, APC signaling pathway, and Wnt signaling pathway, might be associated with the risk of HPD.ConclusionIncorporating new lesions emerging during the treatment was shown to be reliable for the assessment of TGK. TGK serves as a more convenient way to reflect tumor growth acceleration compared with TGR. Genomic alterations were suggested to be associated with the occurrence of HPD.

Background A significant subset of mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) gastric adenocarcinomas (GAC) are resistant to immune checkpoint inhibitors (ICIs), yet the underlying mechanism remains largely unknown. We sought to investigate the genomic correlates of the density of tumor-infiltrating immune cells (DTICs) and primary resistance to ICI treatment. Methods Four independent cohorts of MSI-H GAC were included: (i) the surgery cohort (n = 175) with genomic and DTIC data, (ii) the 3DMed cohort (n = 32) with genomic and PD-L1 data, (iii) the Cancer Genome Atlas (TCGA) cohort (n = 73) with genomic, transcriptomic, and survival data, and (iv) the ICI treatment cohort (n = 36) with pre-treatment genomic profile and ICI efficacy data. Results In the dMMR/MSI-H GAC, the number of mutated genes in the PI3K-AKT-mTOR pathway (NMP) was positively correlated with tumor mutational burden (P + (P + (P = 0.065), CD8+ (P = 0.004), and FOXP3+ cells (P = 0.033) in the central-tumor rather than invasive-margin area, and the transcription of immune-related genes. Compared to the NMP-low (NMP = 0/1) patients, the NMP-high (NMP ≥ 2) patients exhibited a poorer objective response rate (29.4% vs. 85.7%, P P = 0.019), and overall survival (HR = 3.59, P = 0.048) upon ICI treatment. Conclusions Higher NMP was identified as a potential predictor of lower DTICs and primary resistance to ICIs in the dMMR/MSI-H GAC. Our results highlight the possibility of using mutational data to estimate DTICs and administering the PI3K-AKT-mTOR inhibitor as an immunotherapeutic adjuvant in NMP-high subpopulation to overcome the resistance to ICIs.

Objective: Immune checkpoint inhibitors (ICIs) have achieved remarkable results in cancer treatments. However, there is no effectivepredictive biomarker for gastrointestinal (GI) cancer. Methods: We conducted integrative analyses of the genomic and survival data of ICI-treated GI cancer patients from the MemorialSloan Kettering Cancer Center cohort (MSK-GI, n = 227), the Janjigian cohort (n = 40), and the Peking University Cancer Hospital& Institute cohort (PUCH, n = 80) to determine the possible associations between DNA damage response and repair (DDR) genemutations and clinical outcomes. Data from The Cancer Genome Atlas database were analyzed to determine the possible correlationsbetween DDR gene mutations and the tumor microenvironment. Results: In the MSK cohort, the presence of ≥ 2 DDR gene mutations was correlated with prolonged overall survival (OS). TheJanjigian and PUCH cohorts further confirmed that subgroups with ≥ 2 DDR gene mutations displayed a prolonged OS and ahigher durable clinical benefit. Furthermore, the DDR gene mutation load could be considered as an independent prognostic factor,and exhibited a potential predictive value for survival in GI cancer patients treated with ICIs. Mechanistically, we showed that thepresence of ≥ 2 DDR gene mutations was correlated with higher levels of tumor mutation burden, neoantigen, and T cell infiltration. Conclusions: The DDR gene mutation status was correlated with favorable clinical outcomes in GI cancer patients receiving ICIs,which could serve as a potential biomarker to guide patient selection for immunotherapy.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article was retracted at the request of the authors. The authors of this abstract have advised that full agreement between authors and sponsors on publication of the abstract has not been reached and they are therefore unable to publish this data at present.

Background Gastric cancer (GC) is confronted with limited options for precision medicine. Human epidermal growth factor receptor 2 (HER2) is the principal druggable target of GC, yet proper biomarkers for response/resistance prediction remain unveiled. Methods From 40 GC patients received HER2‐targeted therapy, a total of 327 peripheral blood plasma specimens was collected including baseline and treatment time points. Circulating tumor DNA (ctDNA) was extracted and sequenced with a target panel of 425 genes. Experimental validation of resistant mutations was carried out in NIH‐3T3 cell line. Results Genomic features, including ERBB2 copy number variation (CNV), total copy number load, and tumor mutation burdens (TMBs), dynamically changed along with the treatment process and correlated with disease progression. Plasma ctDNA‐based diagnosis was more sensitive than conventional computed tomography scanning in 40% of investigated patients, gaining additional time for clinical management. Compared to baseline, new gene alterations were emerged in 12 patients who developed drug resistance during treatment. ERBB2 mutations potentially related to Pyrotinib resistance were identified in plasma ctDNA of one patient and functional analysis of their downstream signaling pathways was carried out in NIH‐3T3 cell line. TMB exhibited more power than ERBB2 CNV in predicting treatment responses and prognosis for HER2‐targeted therapy in GC patients. Interestingly, survival analysis indicated that patients harboring both HER2 (ERBB2) positivity and high TMB might gain more therapeutic benefits from immune checkpoint inhibitors instead of HER2‐targeted regimens that required further studies and validations Conclusions Our work showed that the dynamic surveillance of plasma ctDNA genomic features provided instructive information for the precision medication of GC patients., Plasma ctDNA‐based diagnosis was more sensitive than conventional computed tomography scanning in 40% of patients, gaining time for clinical management.Plasma tumor mutation burden was a potential marker to predict the therapeutic outcomes of human epidermal growth factor receptor 2 (HER2)‐targeted therapy in GC.HER2‐positive patients with high TMB might gain more therapeutic benefits from immunotherapy instead of HER2‐targeted regimens that required further studies and validations.

BackgroundMicrosatellite instability (MSI) represents the first pan-cancer biomarker approved to guide immune checkpoint blockade (ICB) treatment. However its widespread testing, especially outside of gastrointestinal cancer, is hampered by tissue availability.MethodsAn algorithm for detecting MSI from peripheral blood was established and validated using clinical plasma samples. Its value for predicting ICB efficacy was evaluated among 60 patients with advanced gastrointestinal cancer. The landscape of MSI in blood was also explored among 5138 advanced solid tumors.ResultsThe algorithm included 100 microsatellite markers with high capture efficiency, sensitivity, and specificity. In comparison with orthogonal tissue PCR results, the method displayed a sensitivity of 82.5% (33/40) and a specificity of 96.2% (201/209), for an overall accuracy of 94.0% (234/249). When the clinical validation cohort was dichotomized by pretreatment blood MSI (bMSI), bMSI-high (bMSI-H) predicted both improved progression-free survival and overall survival than the blood microsatellite stable (bMSS) patients (HRs: 0.431 and 0.489, p=0.005 and 0.034, respectively). Four patients with bMSS were identified to have high blood tumor mutational burden (bTMB-H) and trended towards a better survival than the bMSS-bTMB-low (bTMB-L) subset (HR 0.026, 95% CI 0 to 2.635, p=0.011). These four patients with bMSS-bTMB-H plus the bMSI-H group collectively displayed significantly improved survival over the bMSS-bTMB-L patients (HR 0.317, 95% CI 0.157 to 0.640, pConclusionsWe have developed a reliable and robust next generation sequencing-based bMSI detection strategy which, in combination with a panel enabling concurrent profiling of bTMB from a single blood draw, may better inform ICB treatment.

BackgroundEarly onset colorectal cancer (EO CRC) is a heterogeneous colorectal cancer subtype with obvious hereditary tendencies and increasing incidence. We sought to determine the susceptibility genes and molecular characteristics of EO CRC.Methods330 EO metastatic CRC (mCRC) (≤55 years) and 110 average-onset (AO) mCRC patients (>55 years) were enrolled. Capture-based targeted sequencing was performed on tumor tissue and paired white blood cells using a sequencing panel of 520 genes. The association between molecular alterations and overall survival (OS) was analyzed.ResultsOf the 330 EO mCRC patients, 31 carried pathogenic or likely pathogenic germline mutations, with 16 of them diagnosed with lynch syndrome. Fifteen patients had germline mutations in non-mismatch repair genes, including four in MUTHY, three in RAD50, one in TP53, and eight in other genes. Twenty-nine genes were recurrently mutated in EO mCRC, including TP53, APC, KRAS, SMAD4, and BRCA2. The majority of genomic alterations were comparable between EO and AO mCRC. EO mCRC patients were more likely to have a high tumor mutation burden (p < 0.05). RNF43, RBM10, TSC, and BRAF V600E mutations were more commonly observed in EO mCRC, while APC, ASXL1, DNMT3B, and MET genes were more commonly altered in AO patients. At the pathway level, the WNT pathway was the only differentially mutated pathway between EO and AO mCRC (p < 0.0001). The wild-type WNT pathway (p = 0.0017) and mutated TGF-β pathway (p = 0.023) were associated with unfavorable OS in EO mCRC.ConclusionsApproximately one in 10 EO mCRC was associated with hereditary tumors. The spectrum of somatic alterations was largely comparable between EO and AO mCRC with several notable differences.

Circulating tumor DNA (ctDNA) is considered an ideal sample type for genotyping patients with advanced unresectable cancer to inform treatment decision. It may better capture tumor heterogeneity, especially in gastric adenocarcinoma (GAC). However, there exists little evidence regarding genomic profiling of Chinese advanced GAC patients from ctDNA. Blood samples were obtained from 200 advanced GAC patients. Next-generation sequencing (NGS) was performed on ctDNA using a validated 150-gene panel. Blood tumor mutation burden (bTMB) was calculated according to the NGS results. Blood microsatellite instability (bMSI) status was determined by targeted sequencing of 100 microsatellite loci. One hundred sixty-nine (84.5%) patients carried at least one genomic alteration and 138 (69%) patients had at least one deleterious or likely deleterious alteration (del-alteration). The clonal fraction of del-alterations was higher than that of non-del-alterations (80.1% vs 54.5%, P < 0.0001). The most frequently altered genes were TP53 (38%), LRP1B (20%), MYC (13.5%), ERBB2 (12.5%), and KRAS (11.5%). The alterations were most enriched in the TP53/cell cycle (52%) and the RTK-Ras-MAPK pathway (51.5%). The median bTMB was two (range 0 to 42). Eight patients were identified to be high bMSI, with higher median bTMB than the blood microsatellite stable (bMSS) patients (15 vs 2, P = 0.0062). Patients harboring del-alterations of the DDR pathway had significantly higher percentages of high bTMB and bMSI-H patients than the wild-type subgroup (61.1% vs 6.5%, P < 0.0001; 33.3% vs 1.7%, P = 0.0002). A total of 45.5% cases harbored at least one potentially actionable alteration and one patient achieved complete response after receiving matched targeted therapy. Our study uncovered the molecular characterization of Chinese patients with advanced GAC from ctDNA, including genomic alteration, bTMB, and bMSI status. The findings suggested that targeted NGS-based ctDNA analysis may help inform the clinical decision in advanced GAC. KEY MESSAGES: We report the molecular profiling of the largest Chinese advance stage GACs cohort using a CLIA-certified ctDNA assay. Potentially actionable genomic alterations were identified in 45.5% of patients, suggesting clinical utility for ctDNA NGS in advance stage GACs. There was evidence of clinical benefit in one GAC patient with MET amplification treated with MET inhibitor.

Gastrointestinal (GI) cancers represent a major public health problem worldwide. Due to the late detection and high heterogeneity of GI cancers, traditional treatments, including surgery, radiotherapy, chemotherapy, and targeted therapy, have shown limited effects, and the overall prognosis of these patients remains poor. Recently, immunotherapy, involving programmed cell death-1 (PD-1) and its ligand (PD-L1), has shown promising efficacy in several solid cancers and seems to have become a potential treatment option for GI cancers This review focuses on data on the development of immunotherapy-based clinical trials in esophageal cancer, gastric cancer, and colorectal cancer. The predictive biomarkers and combination strategies in clinical trials and translational medicine are also discussed. Finally, prospects for immunotherapy in the treatment of GI cancers are described. Although only a small proportion of patients with GI cancers respond to PD-1/PD-L1 blockade, we strongly believe that precision immunotherapy might improve the overall survival of many more GI cancer patients in the future., Graphical Abstract, Public Summary • Immunotherapy has revolutionized the therapeutic landscape of gastrointestinal cancer, based on a series of clinical trials conducted in recent years. • The next level of predictive biomarker of the response to immune checkpoint inhibitors (ICIs) should address the integration of current multi-omics biomarkers with an interdisciplinary approach. • The emerging combination strategies based on ICIs should be more defined in the specific population. • It is imperative to understand mechanism of acquired resistance to ICIs and explore therapeutic strategies to reverse it.

BackgroundDespite the great achievements made in immune-checkpoint-blockade (ICB) in cancer therapy, there are no effective predictive biomarkers in gastrointestinal (GI) cancer.MethodsThis study included 93 metastatic GI patients treated with ICBs. The first cohort comprising 73 GI cancer patients were randomly assigned into discovery (n=44) and validation (n=29) cohorts. Comprehensive genomic profiling was performed on all samples to determine tumor mutational burden (TMB) and copy-number alterations (CNAs). A subset of samples was collected for RNA immune oncology (IO) panel sequencing, microsatellite instability (MSI)/mismatch repair and program death ligand 1 (PD-L1) expression evaluation. In addition, 20 gastric cancer (GC) patients were recruited as the second validation cohort.ResultsIn the first cohort of 73 GI cancer patients, a lower burden of CNA was observed in patients with durable clinical benefit (DCB). In both the discovery (n=44) and validation (n=29) subsets, lower burden of CNA was associated with an improved clinical benefit and better overall survival (OS). Efficacy also correlated with a higher TMB. Of note, a combinatorial biomarker of TMB and CNA may better stratify DCB patients from ICB treatment, which was further confirmed in the second validation cohort of 20 GC patients. Finally, patients with lower burden of CNA revealed increased immune signatures in our cohort and The Cancer Genome Atlas data sets as well.ConclusionsOur results suggest that the burden of CNA may have superior predictive value compared with other signatures, including PD-L1, MSI and TMB. The joint biomarker of CNA burden and TMB may better stratify DCB patients, thereby providing a rational choice for GI patients treated with ICBs.

The lungs are the second most common site of metastasis for colorectal cancer (CRC) after the liver. Rectal cancer is associated with a higher incidence of lung metastases compared to colon cancer. In China, the proportion of rectal cancer cases is around 50%, much higher than that in Western countries (nearly 30%). However, there is no available consensus or guideline focusing on CRC with lung metastases. We conducted an extensive discussion and reached a consensus of management for lung metastases in CRC based on current research reports and the experts’ clinical experiences and knowledge. This consensus provided detailed approaches of diagnosis and differential diagnosis and provided general guidelines for multidisciplinary therapy (MDT) of lung metastases. We also focused on recommendations of MDT management of synchronous lung metastases and initial metachronous lung metastases. This consensus might improve clinical practice of CRC with lung metastases in China and will encourage oncologists to conduct more clinical trials to obtain high-level evidences about managing lung metastases. Electronic supplementary material The online version of this article (10.1186/s13045-019-0702-0) contains supplementary material, which is available to authorized users.

Immunotherapy has emerged as an effective therapeutic strategy for various cancers, including colorectal cancer (CRC), but only a subset of MSI-H patients can benefit from such therapy. Patched1 (PTCH1) is a frequently altered gene in CRCs and its mutations contribute to unregulated Hedgehog (Hh) signaling. In the study, we evaluated the association of PTCH1 mutations with CRC immunity based on our single-center cohort and multiple cancer genomic datasets. Among 21 enrolled patients, six (28.6%) harbored a PTCH1 mutation based on WES analyses. In CRC patients, the PTCH1 mutation subgroup experienced a higher durable clinical benefit rate than the PTCH1 wild-type subgroup (100% vs. 40%, P = 0.017). In addition, patients with the PTCH1 mutation experienced greater progression-free survival (PFS, P = 0.037; HR, 0.208) and overall survival (OS, P = 0.045; HR, 0.185). A validation cohort from the MSKCC also confirmed the correlation between PTCH1 mutation and better prognosis (P = 0.022; HR, 0.290). Mechanically, diverse antitumor immune signatures were more highly enriched in PTCH1-mutated tumors than in PTCH1 wild-type tumors. Furthermore, PTCH1-mutated tumors had higher proportions of CD8 + T cells, activated NK cells, and M1 type macrophage infiltration, as well as elevated gene signatures of several steps in the cancer-immunity cycle. Notably, the PTCH1 mutation was correlated with tumor mutational burden (TMB), loss of heterozygosity score, and copy number variation burden. Our results show that the mutation of PTCH1 is a potential biomarker for predicting the response of CRC patients to immunotherapy.

For most colorectal cancer patients with initial lung metastasis (LM), the only suitable treatments are palliative, including palliative local therapy and pharmacotherapy. We investigated the role of palliative local treatments in prolonging survival and the efficacy of different pharmacotherapies.After performing a medical record review of 2233 patients with metastatic colorectal cancer, 684 were identified as having LM. Their clinicopathologic characteristics, treatment patterns, and outcomes were analyzed retrospectively.For nonresectable initial LM, patients receiving palliative local therapy had significantly longer median progression-free survival (PFS) and overall survival (OS) than those treated with pharmacotherapy alone: PFS 16.1 months versus 7.4 months (P .001) and OS 51.8 months versus 23.8 months (P .001), respectively. Cox multivariate analysis confirmed the survival benefit induced by palliative local therapy. Chemonaive patients receiving single-agent fluoropyrimidine had shorter PFS and longer OS compared to oxaliplatin- or irinotecan-based doublets when used as first-line treatment (PFS 4.8, 7.4, and 7.3 months; and OS 28.7, 21.2, and 20.1 months, respectively); however, these differences were not statistically significant. The addition of targeted agents to cytotoxic drugs prolonged PFS (10.5 vs. 7.2 months, P = .005) but not OS (27.8 vs. 21.2 months, P = .454). Carcinoembryonic antigen level, LM-associated symptoms, extrapulmonary disease, and histopathologic type were independent pretreatment prognostic factors.Local treatments of LM may confer a survival benefit in the palliative setting. First-line single-agent fluoropyrimidine may be used in patients with good prognosis.

Background Data regarding the clinical characteristics and outcomes of lung metastases (LuM) from colorectal cancer (CRC) are different from those of liver metastases (LiM) from CRC. However, little is known about the genetic features of LuM. This study aimed to identify the different genetic characteristics of LuM and LiM from left-sided microsatellite stable CRC. Methods Tissue samples of the primary tumors and paired metastases from 18 CRC patients with isolated LuM (LuM cohort), 18 patients with isolated LiM (LiM cohort), and 10 locally advanced CRC patients without metastases (control cohort) were selected for next-generation sequencing. Patients in the LiM cohort had matched clinicopathological characteristics with the LuM cohort. The single-nucleotide variations (SNVs), copy number variations (CNVs), pathway alterations, and tumor mutation burdens (TMBs) were also calculated and analyzed. Results The CNV results showed that ZFHX4, GATA2, and FAM131B amplifications were more common in the metastatic cohorts than in the control cohort, while RECQL4 and FLCN amplifications were common in the controls. The LuM cohort had significantly higher proportions of HNF4A, BRD4, and U2AF1 amplification. The LuM, LiM, and control cohorts were successfully separated using pathway alteration analysis. The LuM cohort had more frequent alterations in the RTK/RAS pathway, HIPPO pathway, KRAS, and MET than the LiM group. The LuM cohort also had relatively higher TMBs than the LiM cohort. Conclusions CNVs in primary tumors could identify patients with LuM. Targeting the HIPPO pathway or MET and immune checkpoint inhibitors (ICIs) combined with other agents might be novel therapies for LuM.

e16101 Background: To date, although a number of biomarker-related investigations have focused on the intrinsic properties of tumor cells and immune microenvironment, how germline genetics influences efficacy of immune checkpoint inhibitors (ICIs) immunotherapy in gastrointestinal (GI) cancer is scarcely understood. Methods: Our investigation enrolled 94 metastatic GI cancer patients treated with ICIs recruited from Peking University Cancer Hospital (PUCH) between August 1, 2015, and May 24, 2019. A publicly available dataset from the Memorial Sloan Kettering (MSK) Cancer Center (MSK GI cohort) was used for validation. For the PUCH cohort, we performed HLA genotyping by whole exome sequencing (WES) analysis on the peripheral blood mononuclear cell (PBMC) from all 94 patients. Tumor tissues from 86 patients were subjected to WES analysis and immune oncology-related RNA profiling. Results: We assessed the clinic relevance of germline HLA heterozygosity and evolutionary divergence (HED, a quantifiable measure of HLA-I evolution) to immunotherapy in patients with advanced GI cancers from the PUCH cohort. Our data showed that neither HLA heterozygosity nor mean HED correlated with the overall survival (OS) in the PUCH cohort. However, patients with high HLA-B HED showed a better OS and durable clinic benefit (DCB) rate compared with the lower subgroup (p < 0.05 for all comparison). The prognostic value of HLA-B HED was consistently validated in the MSK GI cohort (N = 84). Notably, a combinatorial biomarker based on HLA-B HED and tumor mutation burden (TMB) could better stratify potential responders (86 patients with tumor samples). Survival analysis performed on the PUCH and MSK GI cancer datasets further demonstrated the potential joint utility of HLA-B HED and TMB for prognosis stratification. Moreover, HLA-B HED high subgroup was characterized with a lower prevalence of TP53 mutation and enrichment of multiple immune related pathways, indicating an immune-inflamed phenotype of this subgroup. Conclusions: Taken together, our data create an intriguing argument for the germline HLA-B sequence divergence and TMB as complementary biomarkers in guiding patient selection for GI cancer immunotherapy. Further investigation revealed a potential HLA-B restricted mutational pattern of TP53, and can be indicative of tumor immune microenvironment in GI cancer.

e15527 Background: BRAF mutations are present in 5-10% of metastatic colorectal cancers (mCRCs). Patients with mCRC whose tumors harbor BRAF V600 mutation generally respond poorly to standard chemotherapy. Treatment with BRAF inhibitors has been shown to improve outcomes, whereas the resistance develops through undefined mechanisms. Therefore, it is imperative to accurately comprehend the genomic profiling of resistance mechanisms to BRAF inhibitors in mCRC for exploring its clinical treatment strategies. Methods: We analyzed next-generation sequencing results in 520 cancer-associated genes for 22 patients who had BRAF V600E mutant mCRC in order to characterize genomic predictors of treatment outcome and track the acquired resistance (AR) mechanisms during the vemurafenib/dabrafenib/encorafenib treatment in combination with cetuximab +/- trametinib. The median age of the patients was 61 years old, 54.5% were male, 54.5% had right-sided mCRC, and 81.8% received one or more prior chemotherapy lines. Tissue and/or plasma samples were collected at baseline (prior to anti-BRAF treatment) and upon disease progression (PD). Objective tumor responses were radiologically assessed every 6 weeks according to RECIST v1. 1. Results: By Feb 2021, treatment had been discontinued in 15 (63.2%) of the patients due to disease progression, while the other 7 cases were still under treatment. The median PFS (mPFS) for all patients was 4.5 months. The overall response rate was 32%, and the disease control rate was 86%. In addition to BRAF V600E, the most common concomitant mutations were identified in TP53 (20/22), RNF43 (8/22), LRP18 (7/22), APC (7/22) and PIK3CA (5/22). Patients with baseline alterations in RNF43 (n = 8; p = 0.0466), or RECQL4 (n = 4; p = 0.0406) had significantly longer PFS than their respective wild type counterparts. In contrast, baseline alterations in PPP2R2A (n = 3; p = 0.0131), RUNX1T1 (n = 3; p = 0.0147), and receptor tyrosine kinase (RTK) signaling pathway genes (n = 6; p = 0.0057) were each significantly associated with shorter PFS. Among the 15 patients whose disease progressed, 9 were identified with newly developed AR mutations in PD tumor or plasma samples. MET amplification was the most common AR mechanism (n = 4) followed by BRAF amplification, KRAS, NRAS mutations (n = 3 each), and MAP2K1, PIK3R1 mutations (n = 1 each). Q61 substitution was the most dominant form for both KRAS and NRAS AR mutations (83%, 5/6). In terms of signaling pathway, MAPK (67%, 6/9) and RTK (44%, 4/9) pathway alterations were most frequently observed. Conclusions: Our study illustrated the landscape of genetic alterations in patients with BRAF V600E mutant mCRC upon BRAF inhibitor treatment, which could be critical to predict responses to BRAF inhibitors and guide personalized clinical decision-making after disease progression.

Purpose: Microsatellite instability (MSI) was the FDA-approved companion diagnostic biomarker for using pembrolizumab in solid tumors and the biomarker for Lynch Syndrome. Next-generation sequencing (NGS) based method was recommended by NCCN and ESMO for detecting MSI status due to rich mutation information it could provide. However, current NGS based methods could be discordant on some cases, triggering confusion in clinical practice. To address this concern, we developed a novel and highly accurate MSI detection method, 3D-MSI, with a set of well-selected loci and compared its performance with other 3 public methods (MANTIS, MSISensor2, mSINGS) Materials and Methods: 100 MSI loci were selected from 2539 candidates and then sequenced on 145 FFPE samples as the training dataset. A binomial distribution model was built on each loci to predict PCR-validated MSI statuses of all samples in the training dataset and then all models were ordered by their prediction accuracy. 3D-MSI method determined MSI status by the percentage of top 30 loci models which predict the sample as MSI-H (>40%: MSI-H; otherwise MSS). Performances of 3D-MSI and other 3 methods were compared on 485 MSI-validated sample. Their discordance were further investigated on a large cohort of 10399 Chinese cancer patients. Detection limits of these 4 methods were determined by 4 serial-diluted tumor samples. We also observed concordance between 3D-MSI detected statuses and immunotherapy response on 27 advanced colorectal cancer (CRC) patients. Results: In the dataset of 485 samples, 3D-MSI had the highest accuracy (All: 96.7%, Colorectal cancer CRC: 98.9%, Gastric cancer GC: 97.0%, other cancer: 86.4%), sensitivity (All: 93.2%, CRC: 97.0%, GC: 94.4%, Other: 80.8%) and specificity (All: 98.2%, CRC: 99.5%, GC: 98.8%, Other: 90.0%) among all 4 methods. It could detect correct MSI status under low tumor content down to 5%, but other methods required much higher tumor content to work (MSISensor2: ≥15%, mSINGS: ≥20%, MANTIS: ≥40%). Study on 10399 Chinese cancer patients confirmed superiority of 3D-MSI: compared with other 3 methods, it yielded the fewest discordant and unreliable MSI statuses questioned by PCR (3D-MSI: 1, MSISensor2: 36, mSINGS: 36, MANTIS: 50). Loci selection was the key point for 3D-MSI to outrival other 3 methods, revealed by comparing their scoring distribution. 3D-MSI detection predicted significantly prolonged PFS (log-rank P Conclusions: Our study offered an improved and clinically validated method for NGS-based MSI detection and stressed importance of loci selection in MSI detection, which would have crucial implications for future research and clinical management. Citation Format: Jian Li, Zhenghang Wang, Bo Yang, Bin Li, Yunjie Song, Bei Zhang, Xiaochen Zhao, Yifan Zhou, Zhenghua Xie, Xiaofang Li, Hao Chen, Hua Dong, Yuezong Bai, Lei Xiong, Fugen Li, Jing Gao, Lin Shen. A novel loci-selected method for microsatellite instability detection validated on a large Chinese cohort [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5477.

Purpose: Predictive biomarkers for immune checkpoint inhibitors (ICIs) are urgently needed in advanced gastrointestinal (GI) carcinoma. Methods: Peripheral blood lymphocyte, lymphocyte subset and early dynamic changes of them were retrospectively analyzed in patients with GI cancer treated with ICIs. Cox regression and Kaplan-Meier analyses were conducted to analyze survival. Results: Eighty patients were enrolled. According to whether tumor progression occurred by 6 months after the initial ICI, patients were divided into two cohorts, 6m-progressive disease (PD) (N=40) and 6m-non-PD (nPD) (N=40).BaselineCD4+/CD8+ T cell (CD4/CD8) ratio was higher in the 6m-nPD cohort than in the 6m-PD cohort. Lymphocyte subsets were obtained both at baseline and before the second dose of ICIs in 61 patients. In total, 54.1% (33/61) of patients experienced tumor progression within 6 months of the initial ICI treatment, and these patients showed significant declines in CD4+ T cell counts (CD4-C1-decline) (p=0.0002) and the CD8+ T cell counts (CD8-C1-decline) (p=0.045) after the first dose of ICIs. In multivariate analyses, CD4-C1-decline (HR=12.66; 95% CI: 2.17-73.91; p=0.005) was an independent prognostic factor for OS. Furthermore, Stratified analyses indicated that CD4-C1-decline was a poor prognostic factor for tumor progression in patients with a deficient mismatch repair (dMMR)/microsatellite instability-high (MSI-H). Conclusion: Early change in CD4+ T cell counts in peripheral blood samples may help as prognostic biomarkers for GI cancer patients treated with ICIs. Further prospective studies are needed to validate this conclusion. Citation Format: Zhi-Hao Lu, Chang Liu, Yan-ni Wang, Shuang Li, Xi Jiao, Jian-ling Zou, Zheng-hang Wang, Chang-song Qi, Xiao-tian Zhang, Jian Li, Lin Shen. Early change in peripheral blood CD4+T cells associated with the clinical outcome in gastrointestinal cancer patients receiving immune checkpoint inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3162.

Immune checkpoint inhibitors (ICIs) have revolutionized the therapeutic landscape of gastrointestinal cancer. However, biomarkers correlated with the efficacy of ICIs in gastrointestinal cancer are still lacking. In this study, we performed 395-plex immune oncology (IO)-related gene target sequencing in tumor samples from 96 patients with metastatic gastrointestinal cancer patients treated with ICIs, and a linear support vector machine learning strategy was applied to construct a predictive model. ResultsAll 96 patients were randomly assigned into the discovery (n=72) and validation (n=24) cohorts. A 24-gene RNA signature (termed the IO-score) was constructed from 395 immune-related gene expression profiling using a machine learning strategy to identify patients who might benefit from ICIs. The durable clinical benefit rate was higher in patients with a high IO-score than in patients with a low IO-score (discovery cohort: 92.0% vs 4.3%, p

e16551 Background: Chowell et al. showed that HLA (human leukocyte antigen) class I (HLA-I) heterozygosity may avail to survival benefit from immune checkpoint blockade (ICB) in advanced cancer patients. Among their cohorts of melanoma patients, patients with the HLA-B44 supertype had improved survival, while the individuals with HLA-B62 supertype had worse outcome. However, these observations were not supported by another study of NSCLC patients treated with immune checkpoint inhibitors (ICIs). Now whether HLA-I genotype can serve as predictive marker for ICB treatment of other malignancies such as gastrointestinal cancer remains unclear. Methods: Tumor tissue samples before immunotherapy as well as related clinical data were collected from 91 Chinese gastrointestinal cancer patients receiving anti-PD-1/PD-L1 inhibitors and/or anti-CTLA-4 antibodies. Genomic features of tumor specimens were characterized by whole exome sequencing (WES) and HLA-I genotyping of normal DNA from peripheral blood cells were performed using WES data. Tumor immune microenvironment signatures were examined by RNA-sequencing targeting 395 immune related genes. Results: We observed that the individuals with HLA-B62 supertype (n = 15) had a significantly shorter PFS (median PFS, 1.83 months versus 3.53 months; HR, 2.3; 95% CI, 1.03-5.0; p= 0.009) than that of those without HLA-B62 supertype (n = 35) in a subgroup of patients with microsatellite stability (MSS, n = 50) and it was not so in other patients with microsatellite instability-high (MSI-H, n = 17) or unknown MSI status (n = 24). Moreover, the patients with B62 supertype and TP53 mutations (n = 15) exhibited more markedly shortened PFS (mPFS, 1.8 months versus 5.57 months; HR, 3.9; 95% CI, 1.5-9.6; p< 0.0001) and OS (mOS, 4.2 months versus 17.3 months; HR, 4.5; 95% CI, 1.5-13.2; p< 0.0001) compared to those patients with non-B62 supertype and TP53 wildtype (n = 26). Furthermore, gene expression levels of certain immune activation related pathways or markers (IFN-γ signature, cytolytic marker, etc.) in the patients with B62 supertype and without B44 supertype (n = 23) were statistically lower ( p< 0.05) than in those patients without B62 supertype (n = 62). Chi-square test revealed no correlation between HLA-B62 supertype and TP53 mutation, MSI status, tumor mutation burden (TMB) or PD-L1 expression. Conclusions: HLA-B62 supertype in combination with TP53 mutations may define a subset of gastrointestinal cancer patients who probably fail to benefit from ICIs, especially in MSS patients.

e16014 Background: Although we have approved immune checkpoint inhibitors (ICIs) in microsatellite instability high (MSI-H) or mismatch-repair-deficient (dMMR) colorectal cancer (CRC), more than half of patients did not respond well to ICIs, emphasizing the need for effective biomarkers. Methods: Whole exome sequencing (WES) analysis was performed on a Chinese cohort of MSI-H/dMMR CRC patients (n = 16). We investigated the pertinence between clinic benefit and potential biomarkers, as TP53 mutation and tumor mutational burden (TMB). The open cohort of ICI-treated CRC patients from the Memorial Sloan Kettering cancer center (MSK ICI cohort) further validated the genomic correlation. Besides, we used the colorectal adenocarcinoma (COADREAD) cohort from The Cancer Genome Atlas (TCGA) dataset to explore the effect of TP53 mutation on the genomic and immunogenetic features. Results: In a Chinese cohort of MSI-H/dMMR CRCs receiving ICIs, we found that patients with TP53 mutation (6 out of 16) showed a remarkable lower durable clinic benefit (DCB) rate than TP53 wild-type subgroup (100% vs. 33%, P = 0.008). Moreover, TP53 wild-type patients were associated with prolonged progression-free survival (P = 0.02; HR, 0.11) and overall survival (P = 0.0037; HR, 0.04). However, TMB-high revealed no statistical significant predictive or prognostic value when using top 20%, 40% or 50% as the cutoff values in our cohort. Further, in order to confirm our observation, we analyzed the association of TP53 mutation with clinic outcome in the publicly available MSK ICI-treated CRC cohort. As expected, the TP53 wild-type patients had a better prognosis (P = 0.037; HR, 0.54) versus the TP53 mutant subgroup. Mechanically, we found that the retention of wild-type TP53 in the TCGA COADREAD cohort was associated with improvement of several steps in the cancer immunity cycle. More intriguingly, in the MSI-H subtype, the TP53 wild-type tumors showed enhanced recognition of cancer cells by T cells and a higher proportion of effector memory CD8+ T cells. Finally, TP53 wild-type tumors also showed reduced heterogeneity and decreased burden of copy number variation, but the correlation between TP53 wild-type tumors and TMB was limited due to MSI status. Conclusions: Our study highlights that TP53 mutations in CRC may indicate inhibition of the tumor microenvironment, particularly in MSI-H/dMMR CRCs. Therefore, the assessment of TP53 status may have important significance in predicting the effectiveness of ICIs in CRC patients and their MSI-H /dMMR subgroup.

Biomarkers in non-colorectal gastrointestinal (GI) cancer patients receiving immune checkpoint blockades (ICBs) are still limited.Data were prospectively collected from a discovery cohort (n = 53) and a validation cohort (n = 107) in patients with non-colorectal GI cancer receiving ICB, as well as a chemotherapy-only cohort (n = 171). System inflammatory markers and derived neutrophil-to-lymphocyte ratio (dNLR) were determined as biomarkers by univariate and multivariate analyses.A higher level of dNLR (cutoff = 3) was associated with shorter overall survival (OS) in discovery and validation cohorts. In pooled cohort, disease control rate (DCR) (28% vs. 48.1%) was associated with dNLR (p = .017). In univariate analysis, original tumor site, tumor histopathology, number of metastases, and dNLR were correlated with OS. In multivariate analysis, higher dNLR level was correlated with reduced OS (10.43 months vs. 4.20 months, p .001). In chemotherapy-only cohort, dNLR was also correlated with DCR and OS.Higher dNLR level was correlated with worse outcomes, suggesting that dNLR may help risk-group stratification and assist disease management strategies as a prognostic biomarker for non-colorectal GI patients receiving ICB.

We investigated the distribution of human leukocyte antigen (HLA)-B27 subtypes in Uygur ankylosing spondylitis patients in Xinjiang. B27-positive patients with ankylosing spondylitis were subtyped by using polymerase chain reaction-sequence-based typing. The HLA-B27 subtype frequencies of Uygur patients were compared with those in Han patients in Xinjiang and the other areas of China. B*2705 was the predominant subtype in Uygur patients with a frequency of 58.95%, which was much higher than that in Han patients in Xinjiang (31.58%, P < 0.05) and the other areas of China (excluding the Shandong region, which was 63.89%). The frequency of B*2704 (27.37%) in Uygur patients was the lowest and significantly lower than that in Han patients (61.18%, P < 0.05) and in 8 other areas of China. B*2710 has not been previously reported in Uygur ankylosing spondylitis patients; B*2704 was the main (61.18%) subtype in Han patients in Xinjiang, followed by B*2705 (31.58%) and was similar to the characteristics of Han patients in the other areas of China. B*2724 in Han ankylosing spondylitis patients has not been previously reported. Additionally, the B*2702/B*2705 homozygote was identified in Uygur patients. B*2702/B*2704, B*2704/B*2705, and B*2705/B*2705 homozygotes were identified in 3 Han patients. The distribution of HLAB27 subtypes in Uygur ankylosing spondylitis patients in Xinjiang significantly differed from that in Han patients. Understanding the distribution of HLAB27 subtypes in ethnic minority populations of Xinjiang is important for anthropological genetic studies and for analyzing the impact of genetic background on ankylosing spondylitis susceptibility.

e15097 Background: Metastases from colorectal cancer (CRC) are common and develop in 40 to 60% of the patients. The liver and lung are the most frequently metastatic sites. Although lung metastasis (LuM) is characterized with slower growth rate and longer survival duration compared to liver metastasis (LiM). Little is known about the genetic differences between LuM and LiM CRC patients. Methods: The LuM cohort was composed of 18 patients with isolated lung metastasis and LiM cohorts was composed of 18 patients with liver metastasis. All the 36 patients were left-sided CRC and all lesions were microsatellite stability (MSS). The two cohorts were matched case by case according to age, gender, primary location, T stage and N stage. The Control cohort involved 10 patients who had locally advanced tumors, received R0 resection and suffered no relapse in at least five years. Based on a 1408 cancer-related gene panel (covering 967010 bases), the next-generation sequencing (NGS) of primary tumors and metastases was performed on the primary and metastatic lesions of these patients. Results: For primary tumors, results showed that the frequency of BRD4 amplification in the LuM cohort (n = 16 ) was 50%, which was much higher than that in the LiM (n = 16) and Control cohorts (n = 10) ( p < 0.05). U2AF1 amplification in the LuM (30%) was more common than that in LiM (0%) patients ( p= 0.043). For metastatic lesions, amplification of MET and SDHC and Hippo pathway activation were more frequently observed in LuM cohort (n = 15) than that in LiM (n = 18). Median TMB of the primary tumors and metastases in the LuM cohort were 9.518 and 6.022 mutations/Mb, respectively, which were both much higher than that in the LiM and Control cohorts ( p< 0.05). Conclusions: Amplification of BRD4 and U2AF1 was the characteristic feature of primary tumors which metastasized to the lungs, indicating this genetic alteration might be used in identifying patients at risk of developing LuM. MET amplification and Hippo pathway activation were promising therapeutic targets of left-sided CRC-LuM with MSS. Patients with LuM might respond well to immunotherapies due to relatively high level of TMB. Expanded prospective cohorts are warranted to further elucidate these findings.

e24263Background: Not only has been proved to be an effective biomarker for prognosis and chemotherapies, but also becomes the first pan-cancer biomarker for immunotherapies, MSI/MMR detection has ...

We investigated the presence of serum antinuclear antibodies (ANAs) and autoantibodies and their relationship with serum prognostic indicators in lymphoma patients. The study population comprised 127 patients diagnosed with lymphoma and 138 healthy control subjects. The blood samples of the participants were assayed for ANAs by immunofluorescence, and autoantibodies were detected by western blotting. Serum ANAs were detected in 31.5 (40/127) and 6.5% (9/138) of lymphoma patients and control subjects, respectively. There was a statistically significant difference between the lymphoma and the control groups (P < 0.05). The level of lactate dehydrogenase in the ANA-positive subjects was significantly lower than in the ANA-negative subjects (P < 0.05). Low ANA titers (1:100) were commonly found in the ANA-positive subjects and the control subjects, and the fluorescence models were diverse. Autoantibodies were found in 35% (14/40) of the ANA-positive patients by western blotting. Detection of ANAs in lymphoma patients helps in determining the diagnosis and prognosis of lymphoma, but has no independent diagnostic value; there are still various autoantibodies of unknown significance that require further study.

This study examined the effects of N-ethylmaleimide-sensitive factor (NSF) small interfering RNA (siRNA) on cardiac function following myocardial infarction (MI) in rats. Thirty-six adult Sprague Dawley rats were randomly divided into three equivalent groups. An acute MI model was established by ligating the anterior descending branch of the left coronary artery and confirmed by electrocardiogram. Recombinant NSF-siRNA adenovirus (experimental), negative adenovirus (control), and normal saline were injected near the infarcted area of the left ventricle in each respective group. The left ventricular ejection fraction (LVEF) was measured with a noninvasive ultrasonic cardiogram. Left ventricular end-diastolic pressure (LVEDP) and the maximum rate of rise in left ventricular pressure (+dp/dt max) were measured using the BL-420 Biological Functional Experimental System. Hearts were sectioned and stained with 2,3,5,-triphenyl tetrazolium chloride (TTC) to observe the MI area. Two weeks after surgery, LVEF in the experimental group (46.0 ± 7.5%) was higher than control (34.0 ± 6.0%) and saline (37.5 ± 4.5%) group LVEFs (P < 0.05), whereas LVEDP was the lowest in the experimental group (18.51 ± 6.87 vs 29.47 ± 9.94 and 26.58 ± 8.97 mmHg, respectively) (P < 0.05). The +dp/dt max was also higher in the experimental group (9.74 ± 1.16 vs 4.33 ± 1.19 and 5.24 ± 1.53 mmHg/s x 10(3), respectively) (P < 0.05); however, the MI area did not differ significantly between groups. Local injection of an adenovirus-mediated NSF-siRNA expression vector near infarcted areas improved cardiac function two weeks after MI, but had no impact on the MI area.

We sought to investigate the effect of nerve growth factor (NGF) expression on the formation and prognosis of cerebral aneurysms. Forty-eight cases were selected following a diagnosis of cerebral aneurysm using computed tomography angiography and surgical confirmation. Thirty-four cases of healthy deaths were also chosen. The tissue was tested for NGF expression changes by reverse-transcription PCR, Western blot and histopathology, and NGF expression was compared between the cerebral aneurysm and healthy groups. The expression level of NGF in cerebral aneurysm tissue was significantly increased over that observed in control tissue. The abnormal expression of NGF is related to cerebral aneurysms. The elevated expression of NGF in cerebral aneurysms may be associated with a poor prognosis.

We report measurements of third-order optical nonlinearity of the 90GeS 2 –5Ga 2 S 3 –5CdS (in mol%) chalcogenide glass using the femtosecond time-resolved optical Kerr gate technique at 820 nm. The third-order nonlinear susceptibility was estimated to be as large as 1.0 × 10 −12 esu. The full width at half maximum of the Kerr signal was 150 fs, implying that the sample had a response faster than 120 fs. Its response was dominantly assigned to the ultrafast distortion of the electron cloud. This glass sample is promising in future all-optical switching devices.