Biomarker For Immune Checkpoint Blockade Research Articles

Transcriptome analysis reveals the clinical significance of CXCL13 in Pan-Gyn tumors

BackgroundGynecologic and breast tumors (Pan-Gyn) exhibit similar characteristics, and the role of CXCL13 in anti-tumor immunity and it’s potential as a biomarker for immune checkpoint blockade (ICB) therapy have been gradually revealed. However, the precise role of CXCL13 in Pan-Gyn remains unclear, lacking a systematic analysis.MethodsWe analyzed 2497 Pan-Gyn samples from the TCGA database, categorizing them into high and low CXCL13 expression groups. Validation was conducted using tumor expression datasets sourced from the GEO database. Correlation between CXCL13 and tumor immune microenvironment (TIME) was evaluated using multiple algorithms. Finally, we established nomograms for 3-year and 5-year mortality.ResultsHigh expression of CXCL13 in Pan-Gyn correlates with a favorable clinical prognosis, increased immune cell infiltration, and reduced intra-tumor heterogeneity. Model was assessed using the C-index [BRCA: 0.763 (0.732–0.794), UCEC: 0.821 (0.793–0.849), CESC: 0.736 (0.684–0.788), and OV: 0.728 (0.707–0.749)], showing decent prediction of discrimination and calibration.ConclusionOverall, this study provides comprehensive insights into the commonalities and differences of CXCL13 in Pan-Gyn, potentially opening new avenues for personalized treatment.

The Evolving Landscape of Biomarkers for Immune Checkpoint Blockade in Genitourinary Cancers.

In the past decade, immune checkpoint inhibitors (ICI) have been approved for treatment of genitourinary malignancies and have revolutionized the treatment landscape of these tumors. However, despite the remarkable success of these therapies in some GU malignancies, many patients' tumors do not respond to these therapies, and others may experience significant side effects, such as immune-related adverse events (iRAEs). Accordingly, biomarkers and improved prognostic tools are critically needed to help predict which patients will respond to ICI, predict and mitigate risk of developing immune-related adverse events, and inform personalized choice of therapy for each patient. Ongoing clinical and preclinical studies continue to provide an increasingly robust understanding of the mechanisms of the response to immunotherapy, which continue to inform biomarker development and validation. Herein, we provide a comprehensive review of biomarkers of the response to immunotherapy in GU tumors and their role in selection of therapy and disease monitoring.

Abstract 2176: A cell mass-based platform for characterizing immune cell function and response to checkpoint blockade in primary blood and malignant fluid samples

Abstract Existing predictive biomarkers for immune checkpoint blockade (ICB) therapies that rely on characterization of tumor genomics or immunohistological assessment of the tumor microenvironment have demonstrated mixed success, with no single biomarker proving to be universally predictive of ICB treatment outcome. To complement these existing approaches, we present a workflow that relies on high-resolution single-cell mass measurements curated with CNN-based image classification to characterize T cell activation and functional response to treatment with ICB therapies. As a highly integrative measure of cellular phenotype, cell mass can be used as a label-free biomarker for characterizing immune cell function. For instance, upon activation with anti-CD3/CD28, T cells isolated from human PBMC showed a rapid and significant increase in cell mass. However, in T cells that had been repeatedly stimulated in vitro to generate a PD-1+ exhausted-like phenotype, this mass response to activation was blunted. We hypothesized that this variability in activation-induced mass response was the result of an altered balance of stimulatory and inhibitory “signal two” cues seen by the T cells. Consistent with this hypothesis, purified T cells stimulated with anti-CD3 alone (no co-stimulation) demonstrated a significantly smaller increase in cell mass when compared with those stimulated with both anti-CD3 and anti-CD28. Furthermore, the T cell response measured when unpurified PBMC were activated with anti-CD3 demonstrated an intermediate mass increase, suggesting contributions of both stimulatory and inhibitory signaling from other cells in the milieu. To explore how ICB treatment disrupts this co-stimulatory/inhibitory signaling balance, we measured T cell mass responses for samples treated with anti-CD3 alone or in combination with pembrolizumab, atezolizumab, nivolumab, or dostarlimab. These samples included PBMC isolated from blood and tumor/immune cell milieus isolated from malignant fluids (pleural effusions or abdominal ascites) collected from patients with advanced cancer. We found that T cells isolated from samples treated with both anti-CD3 and an ICB drug often showed a significantly greater mass increase than the same samples treated with anti-CD3 alone. This mass response showed significant heterogeneity across patients, with many samples showing no significant treatment effect. Despite all four of these therapies targeting ostensibly the same PD-1/PD-L1 signaling axis, we also found significant response heterogeneity to these different treatments within individual samples.These results suggest that mass response measurements capture biological heterogeneity associated with ICB response and may serve as a valuable complementary readout to existing biomarkers. Citation Format: Robert Kimmerling, Mark Stevens, Selim Olcum, Anthony Minnah, Madeleine Vacha, Rachel LaBella, Katie Katsis, Audrey Guo, Juanita Fujii, Zayna Shaheen, Srividya Sundaresan, Anobel Tamrazi, Cliff Reid. A cell mass-based platform for characterizing immune cell function and response to checkpoint blockade in primary blood and malignant fluid samples [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2176.

Probabilistic Mixture Models Improve Calibration of Panel-derived Tumor Mutational Burden in the Context of both Tumor-normal and Tumor-only Sequencing.

Tumor mutational burden (TMB) has been investigated as a biomarker for immune checkpoint blockade (ICB) therapy. Increasingly, TMB is being estimated with gene panel-based assays (as opposed to full exome sequencing) and different gene panels cover overlapping but distinct genomic coordinates, making comparisons across panels difficult. Previous studies have suggested that standardization and calibration to exome-derived TMB be done for each panel to ensure comparability. With TMB cutoffs being developed from panel-based assays, there is a need to understand how to properly estimate exomic TMB values from different panel-based assays. Our approach to calibration of panel-derived TMB to exomic TMB proposes the use of probabilistic mixture models that allow for nonlinear relationships along with heteroscedastic error. We examined various inputs including nonsynonymous, synonymous, and hotspot counts along with genetic ancestry. Using The Cancer Genome Atlas cohort, we generated a tumor-only version of the panel-restricted data by reintroducing private germline variants. We were able to model more accurately the distribution of both tumor-normal and tumor-only data using the proposed probabilistic mixture models as compared with linear regression. Applying a model trained on tumor-normal data to tumor-only input results in biased TMB predictions. Including synonymous mutations resulted in better regression metrics across both data types, but ultimately a model able to dynamically weight the various input mutation types exhibited optimal performance. Including genetic ancestry improved model performance only in the context of tumor-only data, wherein private germline variants are observed. A probabilistic mixture model better models the nonlinearity and heteroscedasticity of the data as compared with linear regression. Tumor-only panel data are needed to properly calibrate tumor-only panels to exomic TMB. Leveraging the uncertainty of point estimates from these models better informs cohort stratification in terms of TMB.

The current landscape of predictive and prognostic biomarkers for immune checkpoint blockade in ovarian cancer.

Immune checkpoint blockade (ICB) therapy has evoked a prominent shift in anticancer therapy. Durable clinical antitumor activity to ICB has been observed in patients with ovarian cancer (OC). However, only a subset of patients derive clinical benefit, and immune-related adverse events (irAEs) caused by ICB therapy can lead to permanent tissue damageand even fatal consequences. It is thus urgent to develop predictive biomarkers to optimize patient outcomes and minimize toxicity risk. Herein, we review current predictive and prognostic biomarkers for checkpoint immunotherapy in OC and highlight emerging biomarkers to guide treatment with ICB. The prevalent biomarkers, such as PD-L1 expression status, tumor-infiltrating lymphocytes, mutational burden, and immune gene signatures, are further discussed. We provide a state-of-the-art survey on prognostic and predictive biomarkers for checkpoint immunotherapy and offer valuable information for guiding precision immunotherapy.

105P RADseq for tumour mutation burden estimation and mutation signature analysis

Tumour mutation burden (TMB) is a biomarker for cancer immune checkpoint blockade (ICB) response, and mutation signatures provide a “life history” of tumour evolution. Researchers have repurposed cancer gene panels (CGPs) to cheaply estimate these parameters. The low coverage of CGPs, however, may be problematic in the exploration of TMB as a biomarker for ICB. Restriction enzyme associated DNA sequencing (RADseq) uses restriction enzymes to achieve coverage at random loci throughout the genome.

1405P Circulating tumor DNA in advanced prostate cancer: Focus on high blood tumor mutational burden (h-bTMB)

High TMB is a promising predictive biomarker for immune checkpoint blockade. Circulating tumor DNA (ctDNA) from plasma is a minimally invasive method that may ease TMB assessment. Prevalence and characteristics of metastatic prostate cancer (mPC) with high TMB is not well described.

426P Assessing nivolumab in class II expressing microsatellite stable (pMMR) colorectal cancer (CRC): Results of the ANICCA-Class II trial

Predictive biomarkers for immune checkpoint blockade (ICB) are desperately needed. Retrospective studies demonstrate that tsMHC-II positivity is a strong predictive biomarker for anti-PD-1 activity in melanoma, Hodgkins disease and breast cancer. Deficient mismatch repair (dMMR) CRC responds readily to anti-PD-1 and has significantly higher tsMHC-II expression than pMMR CRC but some pMMR patients have strong primary tsMHC-II positivity and it is prognostic. We report here a prospective trial of nivolumab in locally advanced and metastatic tsMHC-II positive pMMR CRC (NCT03981146). pMMR CRC patients who had progressed on all standard of care therapies and whose tumors exhibited >1% tsMHC-II were prospectively treated with 480mg nivolumab every 4 weeks. Primary outcome measure was durable clinical benefit (DCB – no progression at 27 weeks), key secondary outcomes were objective response (OR), progression-free survival time (PFS) and overall survival (OS). Of 455 patients screened, 12.8% were tsMHC-II positive (8.6% ≥5% and 0.7% >50% staining). Of 35 patients treated, 65.7% has tsMHC-II ≥5%, 2.9% >50%. Liver metastases were present in 62.9%. At a median follow-up time of 57 weeks, only 1 patient was still on treatment. 3/35 (8.6%) had DCB, none of whom had liver metastases; of 9 patients remaining on therapy >18 weeks, 7 had no liver metastases. The OR was 0%. Currently mPFS is 9.1 weeks (95% Confidence Interval (CI): 9.0, 9.8) and mOS 29.6 weeks (95% CI: 17.3, 42.1). The one patient with tsMHC-II expression >50% remained on treatment for one cycle. Staining of matched primaries and secondaries showed discordance is common with <40% tsMHC-II positive primaries giving rise to positive secondaries. There were no new safety signals. In this first prospective trial of tsMHC-II as a predictive biomarker for anti-PD-1 we show that tsMHC-II expression is not a useful stratifier in advanced pMMR CRC. We discuss likely reasons for this which include the liver predominance of metastatic CRC, the discordance of tsMHC-II status by site and the nature of the IFNg producing T cells in those with tsMHC-II positive pMMR primaries that subsequently relapse.

Alterations in DNA damage response and repair genes as potential biomarkers for immune checkpoint blockade in gastrointestinal cancer.

Objective:Immune checkpoint inhibitors (ICIs) have achieved remarkable results in cancer treatments. However, there is no effective predictive biomarker for gastrointestinal (GI) cancer.Methods:We conducted integrative analyses of the genomic and survival data of ICI-treated GI cancer patients from the Memorial Sloan 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) gene mutations and clinical outcomes. Data from The Cancer Genome Atlas database were analyzed to determine the possible correlations between 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). The Janjigian and PUCH cohorts further confirmed that subgroups with ≥ 2 DDR gene mutations displayed a prolonged OS and a higher 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 the presence 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.

Abstract 5096: Characteristics of tumor immune microenvironment in patients carrying comutations of DNA damage response pathways in esophageal cancer

Abstract Background: Immunotherapy exhibits promising clinical efficacy in treating unresectable esophageal cancer, and several studies have demonstrated that both comutations in DNA damage response (DDR) pathways and tumor immune microenvironment(TIME) could serve as potential biomarkers for immune checkpoint blockade (ICB) treatment. However, the associtation between DDR comutations and TIME remains unclear. Methods: Between April 2020 and September 2020, NGS and TIME analysis of tumor tissue from 22 patients with esophageal cancer were performed by 3D Medicines, Inc., a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory. We retrospectively investigated the association between genomic alterations and immune microenvironment features. Among eight DDR pathways, comutations of check point factors(CPF) plus base excision repair(BER), homologous recombination repair(HRR), mismatch repair(MMR) or Fanconi anemia(FA) were defined as "DDR co-mut+", while mutation of CPF or comutations of CPF plus nucleotide excision repair (NER) were defined as “DDR co-mut-”. In addition, the relationship between comutations of DDR pathways and tumor mutational burden (TMB) was also analyzed. Results: 22 patients with esophageal cancer were included for analysis. 16 of 22 patients (72.7%) were male and the median age was 62 years old(range, 52 to 73 years). Based on the definition of DDR co-mut+ and DDR co-mut-, 13 patients were devided into DDR co-mut+ group, and 9 patients belonged to DDR co-mut- group. Gene alterations and TIME analysis revealed that patients with DDR co-mut+ showed a higher abundance of CD56dim natural killer cells in both tumor(p=0.0161) and stroma(p=0.028) compared with DDR co-mut- patients. No differences were observed in the densities of CD8+ T cells, M1-TAMs, and M2-TAMs between DDR co-mut+ and DDR co-mut- patients. TMB analysis displayed slightly higher in DDR co-mut+ group with no significant difference. Conclusions: Patients with DDR co-mut+ showed better infiltration of CD56dim NK cells in tumor and stroma in esophageal cancer. Combination of DDR comutations with TIME features may be a more promising biomarker to guide immunotherapy. Keywords: esophageal cancer; DNA damage response pathway; tumor immune microenvironment; tumor mutational burden Citation Format: Hao Chen, Xihua Xia, Junling Zhang, Yanan Chen, Mengli Huang. Characteristics of tumor immune microenvironment in patients carrying comutations of DNA damage response pathways in esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5096.

ZFHX4 mutation as a novel predictive biomarker for immune checkpoint blockade in non-small cell lung cancer.

e20535 Background: ZFHX4 mutation as a novel predictive biomarker for immune checkpoint blockade in non-small cell lung cancer. Methods: 165 NSCLC patients treated with ICIs from independent public cohorts(Rizvi2015; Hellmann2018; Miao 2018) were included to assess immunotherapeutic predictive performance of ZFHX4 mutation. The genomic, mRNA profile and its corresponding survival data were retrieved from The Cancer Genome Atlas (TCGA) database for prognostic analysis. Results: In public cohorts 43 (26.06%) NSCLC patients harbored ZFHX4 mutations. Longer PFS was detected in NSCLC patients with ZFHX4 mutation (ZFHX4-mut) compared with those with wildtype ZFHX4 (ZFHX4-wt) (median PFS 22.1 months vs 4.2 months, HR 0.37; 95% CI 0.22 to 0.61; p &lt; 0.001). Higher ORR and DCR were also observed in patients with ZFHX4-mut compared with ZFHX4-wt (ORR: 62.8% vs 21.3%, p＜0.001; DCR: 86.0% vs 60.7%, p＜0.001, respectively). In the multivariable Cox proportional hazards regression model adjusted by PD- L1 expression and tumor mutational burden (TMB) and other confounding factors, ZFHX4-mut remained an independent predictor (HR 0.43; 95% CI 0.22 to 0.83; p = 0.01). ZFHX4-mut was associated with significantly higher TMB compared to ZFHX4-wt (P＜0.001). According to ZFHX4 status and TMB level, we stratified patients into four subgroups: ZFHX4mut-TMB high, ZFHX4mut-TMB low, ZFHX4wt-TMB high, and ZFHX4wt-TMB low. As expected, ZFHX4mut-TMB high patients achieved the longest PFS 23 months (HR 0.21 95% CI 0.10 to 0.43; p &lt; 0.01) among all groups. The combination of ZFHX4 mutation and TMB-H had a better predictive effect. Conclusions: Our results suggested that ZFHX4 mutation might be a potential predictor for ICIs therapy in NSCLC. Prospective studies to further understand the mechanism are warranted.

Homologous recombination deficiency and molecular subtype are associated with immunogenicity in ovarian cancer.

Aim: There is an unmet need for predictive biomarkers for immune checkpoint blockade in ovarian cancer. Homologous recombination deficiency (HRD) and immunoreactive molecular subtype may be associated with determinants of immunogenicity. Materials & methods: Neoantigen load, tumor inflammation signature (TIS), immune cell infiltratesand individual immune checkpoints were assessed based on HRD status and molecular subtype. Results: Tumors with HRD demonstrated significantly higher expression of neoantigens and multiple immune check points, but not higher TIS scores or increased immune cell infiltrates. Immunoreactive tumors had significantly higher neoantigen expression, TIS scores, immune cell infiltrateand immune checkpoint expression compared with other subtypes. Conclusion: HRD and the immunoreactive molecular subtype signature were associated with multiple determinants of immunogenicity and deserve further exploration as predictive biomarkers.

NKG2A and PD-L1 expression panel predicts clinical benefits from adjuvant chemotherapy and PD-L1 blockade in muscle-invasive bladder cancer

BackgroundProgrammed cell death ligand-1 (PD-L1) expression as a single biomarker for immune checkpoint blockade (ICB) was controversial. NKG2A was a PD1/PD-L1 axis-related immunity-dependent factor. NKG2A and PD-L1 expression as a...

Pan-Cancer Analyses Identify the CTC1-STN1-TEN1 Complex as a Protective Factor and Predictive Biomarker for Immune Checkpoint Blockade in Cancer.

The CTC1-STN1-TEN1 (CST) complex plays a crucial role in telomere replication and genome stability. However, the detailed mechanisms of CST regulation in cancer remain largely unknown. Here, we perform a comprehensive analysis of CST across 33 cancer types using multi-omic data from The Cancer Genome Atlas. In the genomic landscape, we identify CTC1/STN1 deletion and mutation and TEN1 amplification as the dominant alteration events. Expressions of CTC1 and STN1 are decreased in tumors compared to those in adjacent normal tissues. Clustering analysis based on CST expression reveals three cancer clusters displaying differences in survival, telomerase activity, cell proliferation, and genome stability. Interestingly, we find that CTC1 and STN1, but not TEN1, are co-expressed and associated with better survival. CTC1-STN1 is positively correlated with CD8 T cells and B cells and predicts a better response to immune checkpoint blockade in external datasets of cancer immunotherapy. Pathway analysis shows that MYC targets are negatively correlated with CTC1-STN1. We experimentally validated that knockout of CTC1 increased the mRNA level of c-MYC. Furthermore, CTC1 and STN1 are repressed by miRNAs and lncRNAs. Finally, by mining the connective map database, we discover a number of potential drugs that may target CST. In sum, this study illustrates CTC1-STN1 as a protective factor and provides broad molecular signatures for further functional and therapeutic studies of CST in cancer.

Abstract P2-08-15: Clinical, pathologic, and molecular associations of tumor mutational burden in metastatic breast cancer

Abstract Background: Tumor mutational burden (TMB) is a biomarker approved to predict response to immune checkpoint blockade (ICB) in solid tumors irrespective of their tissue of origin. However, there are limited data in patients with breast cancer and high TMB to support the use of ICB. The goal of this analysis is to describe clinical, pathological and molecular associations with TMB within a cohort of patients with metastatic breast cancer. Methods: We included patients enrolled onto an ongoing prospective study titled Individualized Molecular Analyses Guide Efforts (IMAGE)-II. Patients eligible for IMAGE-II have metastatic breast cancer of any subtype that had progressed on at least one standard-of-care therapy. Genetic profiling of tumor tissue was performed at the discretion of the treating team using one of several commercially available next generation sequencing platforms. For purposes of this analysis, only patients who underwent tissue-based Foundation Medicine analysis are included as TMB assessments are different across different platforms. Data are summarized by descriptive statistics. Linear and logistic regression analyses are conducted to evaluate the association between TMB and other clinical, pathological and molecular factors. We will present data on associations with specific mutations (i.e. ESR1, ERBB2, DNA repair, Pi3K signaling, TP53) and ctDNA TMB at a later time. Results:Of 117 patients in the IMAGE-II database, median age was 57 (range 23-86), 65% were White, 29% Black, and 6% Other. TMB data were available on 62 patients. Of those with both TMB and subtype information, 35 (70%) had ER+HER2- tumors, and 15 (30%) had ER-HER2- tumors. Median TMB was 4 mutations/megabase and ranged from 0 to 27. We did not observe significant differences in TMB in patients with ER+HER2- and those with ER-HER2- tumors (median TMB of 4 [0-27] and 5 [1-25], respectively), nor between White versus Black patients (median TMB of 4 [0-27] and 5 [0-12], respectively). However, we did observe that age was positively associated with higher TMB (p-value = 0.02). Additionally, we observed that the time between metastatic diagnosis and TMB measurement was positively associated with TMB (p-value &amp;lt; 0.01); this significant association was also observed in ER+HER2- patients (p-value &amp;lt; 0.01) but not in ER-HER2- patients. Median time to obtaining TMB since metastatic diagnosis was 1.1 (range -0.8 - 12.8) years. More lines of chemotherapy prior to TMB assessment was not observed to be associated with higher TMB. Conclusions: We observed that TMB was higher in patients who have had a longer disease course. Further research is required to understand changes in TMB over time, and how TMB is correlated with. other genomic and tumor microenvironment characteristics. A deeper understanding of TMB may help refine it as a predictive biomarker for ICB. Citation Format: Mohamed A Mohamed, Chenghuang Wang, Morgan Buckley, Jennifer Lehman, Jenna Canzoniero, Christopher D Gocke, Raquel Nunes, Ben Ho Park, Karen L Smith, Jessica Tao, Hanna Tukachinsky, Mary Wilkinson, Antonio C Wolff, Vered Stearns, Cesar A Santa-Maria. Clinical, pathologic, and molecular associations of tumor mutational burden in metastatic breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-08-15.

Association of Smoking Status with Efficacy of First-line Immune Checkpoint Inhibitors in Advanced Non-small Cell Lung Cancers: A Systematic Review and Meta-analysis.

Background: Although smoking status has potential as a biomarker for immune checkpoint blockade in advanced non-small cell lung cancer (NSCLC), its clinical significance remains obscure. This meta-analysis aims to assess the impact of the smoking status on the efficacy of first-line immunotherapy and to find better treatment in never-smoker and ever-smoker patients.Methods: We searched the MEDLINE, EMBASE, and Cochrane database for trials comparing immunotherapy with conventional chemotherapy as front-line treatment for advanced NSCLC. Random-effects models were used to pool estimates of hazard ratios (HRs) for overall survival with 95% confidence intervals (CIs). Predefined subgroup analysis was performed to investigate the difference in the efficacy between the single checkpoint blockade and checkpoint inhibitor plus chemotherapy combination in the never-smokers and current/former smokers.Results: Twelve trials involving 6,446 patients were included in the analysis. A statistically significant overall survival benefit over conventional chemotherapy was found for both checkpoint inhibitor monotherapy (HR, 0.71; 95% CI, 0.59-0.85) and checkpoint inhibitor plus chemotherapy (HR, 0.75; 95% CI, 0.63-0.90) in the current/former smoker group. There was no subgroup difference between monotherapy and combination treatment (p=0.67). However, there was an inconsistent survival outcome in the never-smoker group; checkpoint blockade monotherapy did not show significantly better efficacy than chemotherapy alone (HR, 1.05; 95% CI, 0.81-1.37), but combination treatment showed an overall survival benefit (HR, 0.64; 95% CI, 0.43-0.94). A significant subgroup difference existed between monotherapy and combination therapy (p=0.04). Similarly, there was a significant difference in efficacy of monotherapy between the current/former smoker and never-smoker group (p=0.01), but the efficacy of the combination treatment was comparable between the two groups (p=0.45).Conclusion: Smoking status, which is easily available information, could be used as a guide in clinical practice to choose better treatment in the front-line setting for advanced NSCLC patients.

Protein phosphatase 2A inactivation induces microsatellite instability, neoantigen production and immune response

Microsatellite-instable (MSI), a predictive biomarker for immune checkpoint blockade (ICB) response, is caused by mismatch repair deficiency (MMRd) that occurs through genetic or epigenetic silencing of MMR genes. Here, we report a mechanism of MMRd and demonstrate that protein phosphatase 2A (PP2A) deletion or inactivation converts cold microsatellite-stable (MSS) into MSI tumours through two orthogonal pathways: (i) by increasing retinoblastoma protein phosphorylation that leads to E2F and DNMT3A/3B expression with subsequent DNA methylation, and (ii) by increasing histone deacetylase (HDAC)2 phosphorylation that subsequently decreases H3K9ac levels and histone acetylation, which induces epigenetic silencing of MLH1. In mouse models of MSS and MSI colorectal cancers, triple-negative breast cancer and pancreatic cancer, PP2A inhibition triggers neoantigen production, cytotoxic T cell infiltration and ICB sensitization. Human cancer cell lines and tissue array effectively confirm these signaling pathways. These data indicate the dual involvement of PP2A inactivation in silencing MLH1 and inducing MSI.

ARID1A, ARID1B, and ARID2 Mutations Serve as Potential Biomarkers for Immune Checkpoint Blockade in Patients With Non-Small Cell Lung Cancer.

Worldwide, non-small cell lung cancer (NSCLC) has the highest morbidity and mortality of all malignancies. The lack of responsiveness to checkpoint inhibitors is a central problem in the modern era of cancer immunotherapy, with the rapid development of immune checkpoint inhibitors (ICIs) in recent years. The human switch/sucrose nonfermentable (SWI/SNF) chromatin-remodeling complex has been reported to be recurrently mutated in patients with cancer, and those with SWI/SNF mutations have been reported to be sensitive to ICIs. Six reported cohorts, a total of 3416 patients, were used to analyze the mutation status of ARID1A, ARID1B, ARID2 and SMARCA4 in patients with NSCLC and the effect of mutations on prognosis after ICIs. Finally, a nomogram was established to guide the clinical use of ICIs. The results show that patients with NSCLC who have ARID1A, ARID1B, and ARID2 mutations of the SWI/SNF complex were more likely to benefit from ICI therapy.

Changes in expression of PD-L1 on peripheral T cells in patients with melanoma and lung cancer treated with PD-1 inhibitors

Advances in cancer immunology have increased the use of immune checkpoint inhibitors in clinical practice, however not all patients respond, and treatment can have severe side-effects. Blood-based immunological biomarkers are an attractive method for predicting which patients will respond to therapy, however, reliable biomarkers for immune checkpoint blockade are lacking. This study aimed to identify patients before or early in treatment who would best respond to PD-1 inhibitors. We hypothesised that higher baseline PD-L1 and/or PD-1 on peripheral blood T cells could predict radiological response to PD-1 inhibitors. This pilot prospective cohort study assessed 26 patients with melanoma or non-small cell lung cancer, treated with pembrolizumab, nivolumab, or nivolumab/ipilimumab combined. Response was assessed by RECIST 1.1. Peripheral blood lymphocytes collected at baseline, after one cycle, 10 weeks and at discontinuation of therapy were analysed by flow cytometry. Patients with a higher proportion of PD-L1+ T cells at baseline had improved objective response to PD-1 inhibitor therapy, and patients with a lower proportion of regulatory T cells at baseline experienced more immune-related adverse events. These findings may prove useful to assist in clinical decision making. Further studies with larger cohorts are required to validate these findings.

Abstract 347: TET1 mutation as potential biomarker for immune checkpoint blockade in colorectal cancer

Abstract Background: TET1, a DNA demethylase, is encoded by TET1 gene. At present, TET1 mutation has been reported to be associated with enhanced tumor immunogenicity and activated anti-tumor immunity across multiple cancers. However, the clinical effect of TET1 mutation on immunotherapy in colorectal cancer is little known. Methods: 876 patients with colorectal cancer were enrolled in this study. Genomic profiling of DNA was performed on formalin-fixed paraffin-embedded tumor samples by NGS with 733 cancer-related genes panel. The somatic and germline mutation data were both obtained. Benign and likely benign mutations were excluded from our analysis. Programmed death ligand-1(PD-L1) expression status was determined by immunohistochemistry, evaluated with the combined positive score (CPS) and tumor proportion score (TPS). The efficiency of immunotherapy was analyzed in a cohort of 85 patients with colorectal cancer from Morris et al. Results: 40 of 876 patients (4.75%) harbored TET1 mutations, including nonsynonymous, frameshift and stopgain mutations. Totally, 66 TET1 single nucleotide mutation were identified. Median tumor mutation burden (TMB) value with TET1 mutations was 109.2 mutations/MB, significantly higher than 6.1 mutations/MB in TET1 wild-type group (p&amp;lt;0.001). Microsatellite instability-high (MSI-H) appeared more frequently in TET1 mutations group than TET1 wild-type group (50.0% vs 5.0%, p&amp;lt;0.001). For PD-L1 TPS, compare to TET1 wild type groups, the positive rate of PD-L1 expression in TET1 mutations was higher significantly (6.7% vs 2.7%, p&amp;lt;0.001). The same thing happened with PD-L1 CPS (50.0% vs 23.3%, p&amp;lt;0.001). Possibly, TET1 mutation was a potential marker for immunotherapy. The results were validated in a clinical cohort of immunotherapy, including 85 patients with colorectal cancer. The median overall survival was non-reached in 7 patients with TET1 mutations compare to 13 months in TET1 wild-type group (HR: 0.28, 95% CI 0.11-0.69, P=0.006). Conclusions: TET1 mutation was strongly associated with higher TMB, MSI-H and PD-L1 expression and improved OS in patients receiving immune checkpoint blockade treatment, suggesting that TET1 mutation is a novel predictive biomarker for immunotherapy in colorectal cancer. Citation Format: Shaojun Yu, Ding Zhang, Shiqing Chen. TET1 mutation as potential biomarker for immune checkpoint blockade in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 347.