Individualized tumor-informed circulating tumor DNA analysis for postoperative monitoring of non-small cell lung cancer.

We report a personalized tumor-informed technology, Patient-specific pROgnostic and Potential tHErapeutic marker Tracking (PROPHET) using deep sequencing of 50 patient-specific variants to detect molecular residual disease (MRD) with a limit of detection of 0.004%. PROPHET and state-of-the-art fixed-panel assays were applied to 760 plasma samples from 181 prospectively enrolled early stage non-small cell lung cancer patients. PROPHET shows higher sensitivity of 45% at baseline with circulating tumor DNA (ctDNA). It outperforms fixed-panel assays in prognostic analysis and demonstrates a median lead-time of 299 days to radiologically confirmed recurrence. Personalized non-canonical variants account for 98.2% with prognostic effects similar to canonical variants. The proposed tumor-node-metastasis-blood (TNMB) classification surpasses TNM staging for prognostic prediction at the decision point of adjuvant treatment. PROPHET shows potential to evaluate the effect of adjuvant therapy and serve as an arbiter of the equivocal radiological diagnosis. These findings highlight the potential advantages of personalized cancer techniques in MRD detection.

bITH, a blood-based metric of intratumor heterogeneity, is associated with clinical response to immune checkpoint blockade in non-small cell lung cancer.

BACKGROUND: Intratumor heterogeneity (ITH) has been associated with poor prognosis in advanced non-small cell cancer (NSCLC) patients receiving immune checkpoint blockade (ICB) therapies. However, there is currently no evidence supporting an ITH metric as a predictor of clinical benefit from ICB. The unique advantages of blood make it a promising material for ITH estimation and relevant applications. This study aims to develop and validate a blood-based ITH index for predicting ICB response. METHODS: NSCLC patients from the OAK and POPLAR clinical trials were used as the training cohorts for algorithm development. Survival analyses with overall survival (OS) and progression-free survival (PFS) as endpoints were performed to assess clinical response. The predictive value of bITH was subsequently validated with an independent cohort of 42 NSCLC patients treated with PD-1 blockade. FINDINGS: bITH was significantly associated with the differential OS and PFS elicited by atezolizumab vs. docetaxel in both univariable and multivariable analyses in the OAK patients, suggesting bITH as an independent predictor for response to ICB. Moreover, compared with blood tumor mutation burden (bTMB), bITH enabled greater OS segregation and comparable PFS segregation, and obtained a predictive role regardless of bTMB status. Moreover, the association between bITH and PFS was validated with an independent cohort. INTERPRETATION: Patients with low blood-based ITH metric manifest significant OS and PFS benefit from immunotherapy versus chemotherapy. Future research is awaited to corroborate our findings and to enrich the clinical utility of ITH. FUNDING: This study was supported by the National Natural Science Foundation of China (Nos. 81972718 and 81572321), the Natural Scientific Foundation of Zhejiang Province, China (No. LY19H160007), the Science and Technology Program for Health and Medicine in Zhejiang Province, China (No. 2021KY541), the Scientific Research Project, Science and Technology Department of Sichuan Province (No. 21YYJC1616), the Scientific Research Project, Sichuan Medical Association (No. S20002), Wu Jieping Medical Foundation (No. 320.6750), and 2018 Entrepreneurial Leading Talent of Guangzhou Huangpu District and Guangzhou Development District (No. 2022-L023).

Mutation Landscape of Homologous Recombination Repair Genes in Epithelial Ovarian Cancer in China and Its Relationship With Clinicopathlological Characteristics.

OBJECTIVE: The status of homologous recombination repair (HRR) gene mutations and their impact on the survival of patients with Chinese epithelial ovarian cancer (EOC) are still unclear. In this study, we retrospectively analyzed the mutations of HRR genes in tumor tissues and evaluated their values for predicting the survival of Chinese EOC patients. METHODS: A total of 273 primary EOC patients from five different hospitals between 2015 and 2016 were recruited. All patients received staging surgeries or debulking surgeries combined with systemic platinum-based chemotherapy. DNA was extracted from formalin-fixed, paraffin-embedded sections and analyzed for mutations using a 21-gene panel (including 13 well-known HRR genes) by next-generation sequencing. RESULTS: High-grade serous carcinoma (HGSOC) accounted for 76.2% of the cohort. A total of 34.1% (93/273) cases had 99 deleterious mutations in 9 HRR genes, namely, BRCA1 (56/273, 20.5%), BRCA2 (20/273, 7.3%), ATM (5/273, 1.8%), RAD51C (5/273, 1.8%), RAD51D (5/273, 1.8%), BRIP1 (2/273, 1.8%), CHEK2 (2/273, 0.7%), FANCI (2/273, 0.7%), and RAD54L (1/273, 0.4%). There is a strong mutual exclusion between HRR genes. The mutation landscape revealed several unappreciated deleterious variants in BRCA1/2 and other HRR genes reported previously. Estimated according to the mutation allele frequency, about 4.8% of the patients had potential somatic HRR gene mutations, which might be underestimated. Moreover, HRR mutations mainly exist in HGSOC (83/208, 39.9%), clear cell (2/30, 6.7%), and endometroid subtypes (8/20, 40%), but not seen in other rare subtypes. BRCA1 mutations tend to be present in younger patients with family history or multiple primary foci. Patients with BRCA1/2 mutations tend to have a longer progression-free survival and overall survival, while other HRR mutation carriers tend to have a shorter progression-free survival, but no significant difference in overall survival. CONCLUSION: This study revealed the distribution of HRR gene mutations in Chinese EOC tissues. BRCA1/2 account for the majority of HRR gene mutations and predict long prognosis in HGSOC. Non-BRCA HRR mutations also account for a very important proportion and might be associated with poor prognosis in HGSOC. It is suggested that HRR gene mutations need to be detected in EOC tissues and germline status be further clarified in clinical algorithm for potential targeted therapy, genetic screening, and prognosis prediction.

Low T790M relative allele frequency indicates concurrent resistance mechanisms and poor responsiveness to osimertinib.

BACKGROUND: T790M relative allele frequency (RAF) in plasma, calculated by the ratio of T790M to epidermal growth factor receptor (EGFR)-sensitizing mutation allele frequencies (AF), is associated with osimertinib response in patients with progressive non-small cell lung cancer (NSCLC) post 1st generation EGFR-tyrosine kinase inhibitor (TKI) treatment. However, which subgroup of patients carry concurrent resistance mechanisms and have poor responsiveness to osimertinib remains unknown. METHODS: Matched re-biopsy tissue and plasma samples obtained from 32 patients who had progression following 1st generation EGFR-TKI treatment were genotyped using next-generation sequencing (NGS) to investigate which subgroup of patients, classified by plasma position 790 (T790M) RAF, were more likely to carry concurrent resistance mechanisms. In another independent cohort, consisting of 21 T790M-positive patients, we validated whether these patients had a poor response to osimertinib treatment. RESULTS: In the discovery cohort, patients with T790M RAF less than 20% were more likely to harbor concurrent resistance mechanisms (P=0.018), such as MET or ERBB2 amplification, and small cell lung cancer transformation. In the validation cohort, we found that patients with low T790M RAF (<20%) had significantly lower objective response rates (ORRs) (0 vs. 68.8%, P=0.03) and disease control rates (DCRs) (60% vs. 100%, P=0.048) in response to osimertinib compared to patients with high T790M RAF. CONCLUSIONS: In patients with progressive NSCLC post 1st generation EGFR-TKI treatment, plasma T790M RAFs of less than 20% can be used to identify patients who carry concurrent resistance mechanisms, and can predict a poorer response to osimertinib. TRIAL REGISTRATION: This study was registered on http://www.chictr.org.cn (registration number: ChiCTR-DDD-16007900).

Genomic characteristics in Chinese non-small cell lung cancer patients and its value in prediction of postoperative prognosis.

BACKGROUND: The genomic profile of non-small cell lung cancer (NSCLC) in Asians is distinct from that of Caucasians, but comprehensive genetic profiling reports have been limited for Asian patients. We aimed to elucidate genomic characteristics of Chinese NSCLC patients and develop potential model including genomic characteristics to predict postoperative prognosis. METHODS: Resected tumor samples from 511 patients with stage I-IV lung cancer were subjected to targeted sequencing using a panel of 295 cancer-related genes. Based on the molecular profiles and clinical features, we established nomogram models with predictors consisting of integrated clinical and genomic characteristics to provide post-operative risk stratification. RESULTS: Compared to the TCGA population (mainly Caucasians), there was a significantly higher frequency of EGFR (53.7% vs. 14.4%) and NOTCH3 (8.4% vs. 1.3%) mutations and less mutated KRAS (11.0% vs. 32.6%), KEAP1 (4.4% vs. 17.4%) and LRP1B (16.3% vs. 29.6%) in Chinese lung adenocarcinomas (LUAD). Distinct patterns of mutually exclusive and co-occurring mutations were identified between LUAD and lung squamous cell carcinoma (LUSC), indicating the unique histology-specific tumorigenesis mechanism of each subtype. We observed alterations in pathways correlated with clinical characteristics. Additionally, we constructed nomogram model with predictors consisting of clinical and genomic characteristics, which were more accurate than models with clinical characteristics or TNM staging only both in stage I-IIIA patients and T1-2N0M0 sub-cohort. CONCLUSIONS: This study revealed Chinese NSCLC patients have unique genomic profile. Furthermore, the nomogram model combining clinical features with genomic characteristics could improve risk stratification in early-stage NSCLC.

Tumor mutation burden in Chinese cancer patients and the underlying driving pathways of high tumor mutation burden across different cancer types.

BACKGROUND: Tumor mutation burden (TMB) has an important association with immunotherapy responses. TMB in the Chinese population has not been well established. Finding differences between the Chinese and Caucasian populations and elucidating the underlying biological mechanisms of high TMB might help develop more precise and effective means for TMB and immunotherapy response prediction. METHODS: Chinese cancer patients fresh tissue (n=2,177), formalin-fixed, paraffin-embed (FFPE) specimens (n=3,294), and pleural fluid (n=189) were profiled using a 295- or 520-gene next-generation sequencing (NGS) panel. The association of the TMB status with a series of molecular features and biological pathways was determined using bootstrapping. RESULTS: TMB, measured by 295- or 520-cancer-related gene panels, was correlated with whole-exome sequencing (WES) TMB based on the in silico simulation in The Cancer Genome Atlas cohort. The median TMB of our data was slightly higher than that from the Foundation Medicine Inc. (FMI) dataset. TMB was also slightly different within the same cancer type between the Chinese and Caucasian population. We discovered that the underlying pathways of TMB status varied greatly and sometimes had an opposite association with TMB across different cancer types. Moreover, we developed a 23-gene and a 16-gene signature to predict TMB prediction for lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), respectively, indicating a histology-specific mechanism for driving high-TMB in lung cancer. CONCLUSIONS: TMB varies among different ethnic populations. Our findings extend the knowledge of the underlying biological mechanisms for high TMB and might be helpful for developing more precise and accessible TMB assessment panels and algorithms in more cancer types.

The prognostic value of a Methylome-based Malignancy Density Scoring System to predict recurrence risk in early-stage Lung Adenocarcinoma.

Current NCCN guidelines do not recommend the use of adjuvant chemotherapy for stage IA lung adenocarcinoma patients with R0 surgery. However, 25% to 40% of patients with stage IA disease experience recurrence. Stratifying patients according to the recurrence risk may tailor adjuvant therapy and surveillance imaging for those with a higher risk. However, prognostic markers are often identified by comparing high-risk and low-risk cases which might introduce bias due to the widespread interpatient heterogeneity. Here, we developed a scoring system quantifying the degree of field cancerization in adjacent normal tissues and revealed its association with disease-free survival (DFS). Methods: We recruited a cohort of 44 patients with resected stage IA lung adenocarcinoma who did not receive adjuvant therapy. Both tumor and adjacent normal tissues were obtained from each patient and subjected to capture-based targeted genomic and epigenomic profiling. A novel methylome-based scoring system namely malignancy density ratio (MD ratio) was developed based on 39 patients by comparing tumor and corresponding adjacent normal tissues of each patient. A MD score was then obtained by Wald statistics. The correlations of MD ratio, MD score, and genomic features with clinical outcome were investigated. Results: Patients with a high-risk MD ratio showed a significantly shorter postsurgical DFS compared with those with a low-risk MD ratio (HR=4.47, P=0.01). The MD ratio was not associated with T stage (P=1), tumor cell fraction (P=0.748) nor inflammatory status (p=0.548). Patients with a high-risk MD score also demonstrated an inferior DFS (HR=4.69, P=0.039). In addition, multivariate analysis revealed EGFR 19 del (HR=5.39, P=0.012) and MD score (HR= 7.90, P=0.01) were independent prognostic markers. Conclusion: The novel methylome-based scoring system, developed by comparing the signatures between tumor and corresponding adjacent normal tissues of individual patients, largely minimizes the bias of interpatient heterogeneity and reveals a robust prognostic value in patients with resected lung adenocarcinoma.

Circulating tumor DNA clearance predicts prognosis across treatment regimen in a large real-world longitudinally monitored advanced non-small cell lung cancer cohort.

BACKGROUND: Although growth advantage of certain clones would ultimately translate into a clinically visible disease progression, radiological imaging does not reflect clonal evolution at molecular level. Circulating tumor DNA (ctDNA), validated as a tool for mutation detection in lung cancer, could reflect dynamic molecular changes. We evaluated the utility of ctDNA as a predictive and a prognostic marker in disease monitoring of advanced non-small cell lung cancer (NSCLC) patients. METHODS: This is a multicenter prospective cohort study. We performed capture-based ultra-deep sequencing on longitudinal plasma samples utilizing a panel consisting of 168 NSCLC-related genes on 949 advanced NSCLC patients with driver mutations to monitor treatment responses and disease progression. The correlations between ctDNA and progression-free survival (PFS)/overall survival (OS) were performed on 248 patients undergoing various treatments with the minimum of 2 ctDNA tests. RESULTS: The results of this study revealed that higher ctDNA abundance (P=0.012) and mutation count (P=8.5×10-4) at baseline are associated with shorter OS. We also found that patients with ctDNA clearance, not just driver mutation clearance, at any point during the course of treatment were associated with longer PFS (P=2.2×10-16, HR 0.28) and OS (P=4.5×10-6, HR 0.19) regardless of type of treatment and evaluation schedule. CONCLUSIONS: This prospective real-world study shows that ctDNA clearance during treatment may serve as predictive and prognostic marker across a wide spectrum of treatment regimens.

Monitoring of circulating tumor DNA and its aberrant methylation in the surveillance of surgical lung Cancer patients: protocol for a prospective observational study.

BACKGROUND: Detection of circulating tumor DNA (ctDNA) is a promising method for postoperative surveillance of lung cancer. However, relatively low positive rate in early stage patients restricts its application. Aberrant methylation of ctDNA can be detected in blood samples, and may provide a more sensitive method. This study is designed to systematically evaluate and compare the detection of aberrant methylation and mutations in ctDNA among surgical non-small cell lung cancer (NSCLC) patients, aiming to investigate the feasibility of ctDNA detection as a means of lung cancer surveillance. METHODS: This is a prospective observational study. Consecutive surgical NSCLC patients will be recruited. Blood samples will be collected both before and after surgery (during the follow-up period), while matching tumor tissues and tumor-adjacent normal tissues will be collected during surgery. Quantitative analysis of aberrant methylation and mutations of ctDNA will be conducted in combination with a three-year follow-up data. DISCUSSION: This is the first registered prospective study designed to investigate the feasibility of ctDNA methylation detection as a means of postoperative lung cancer surveillance. We will systematically evaluate and compare the quantitative detection of ctDNA mutations and ctDNA methylation in surgical NSCLC patients, combining with the follow-up information. By integrating genetic and epigenetic information of ctDNA, more effective strategies for postoperative surveillance may be defined. TRIAL REGISTRATION: This study (MEDAL, MEthylation based Dynamic Analysis for Lung cancer) was registered on ClinicalTrials.gov on 08/05/2018 (NCT03634826; Pre-results).

Clinical Utility of Cerebrospinal Fluid Cell-Free DNA as Liquid Biopsy for Leptomeningeal Metastases in ALK-Rearranged NSCLC.

INTRODUCTION: Leptomeningeal metastases (LMs) indicated a poor prognosis in NSCLC. LMs were more frequent in driver gene-mutated patients, and cerebrospinal fluid (CSF) cell-free DNA has shown unique genetic profiles of LM in EGFR-mutated LM. However, studies in patients with ALK receptor tyrosine kinase gene (ALK)-rearranged NSCLC with LMs are scarce. METHODS: Patients with lung cancer with ALK rearrangement were screened from September 2011 to February 2018 at our institute. CSF and paired plasma were tested by next-generation sequencing. RESULTS: LMs were diagnosed in 30 (10.3%) of 291 patients with ALK-rearranged lung cancer. A total of 11 paired CSF and plasma samples tested by next-generation sequencing were analyzed. Driver genes were detected in 81.8% of the CSF samples (9 of 11) and 45.5% of the plasma samples (5 of 11) (p = 0.183). The maximum allelic fractions were all higher in CSF than in plasma (p = 0.009). ALK and tumor protein p53 gene (TP53) were the two most frequently mutated genes in CSF. Gatekeeper gene ALK G1202R and C1156F mutations were identified in CSF after resistance to alectinib. Multiple copy number variants were mainly found in CSF, including in EGFR, cyclin D1 gene (CCND1), fibroblast growth factor 3 gene (FGF3), and fibroblast growth factor 4 gene (FGF4). Also found were v-myc avian myelocytomatosis viral oncogene homolog gene (MYC) copy number gains and TP53 and cyclin dependent kinase inhibitor 2A gene (CDKN2A) copy number deletions. Brigatinib seemed to be effective in controlling LM. One case showed that CSF could be used to monitor disease development of LM and longitudinally monitor tumor response. CONCLUSION: Liquid biopsy of CSF is more sensitive than liquid biopsy of plasma to detect targetable alterations, characterizing resistance mechanisms on progression and monitoring tumor response in patients with ALK-rearranged NSCLC with LM. Thus, CSF might be promising as a medium of liquid biopsy in LM.

Parallel serial assessment of somatic mutation and methylation profile from circulating tumor DNA predicts treatment response and impending disease progression in osimertinib-treated lung adenocarcinoma patients.

BACKGROUND: Circulating tumor DNA (ctDNA) harboring tumor-specific genetic and epigenetic aberrations allows for early detection and real-time monitoring of tumor dynamics. In this study, we aimed to evaluate the potential of parallel serial assessment of somatic mutation and methylation profile in monitoring the response to osimertinib of epidermal growth factor receptor (EGFR) T790M-positive advanced lung adenocarcinoma patients. METHODS: Parallel somatic mutation and DNA methylation profiling was performed on a total of 85 longitudinal plasma samples obtained from 8 stage IV osimertinib-treated EGFR T790M-positive lung adenocarcinoma patients. RESULTS: Our results revealed a significant correlation between the by-patient methylation level with the maximum allele fraction (maxAF, P=0.0002). The methylation levels were significantly higher in the plasma samples of patients with detectable somatic mutations than patients without somatic mutations (P=0.0003) and healthy controls (P=0.0018). Moreover, analysis of both the DNA methylation level and maxAF revealed four trends of treatment response. Collectively, the decrease in methylation level and maxAF reflected treatment efficacy, while the gradual increase reflected impending disease progression (PD). Elevated methylation levels and maxAF were observed in 6 and 5 patients in an average lead-time of 3.0 and 1.9 months, respectively, prior to evaluation of PD using radiological imaging. CONCLUSIONS: DNA methylation profiling has the potential to predict disease relapse prior to evaluation through radiological modalities, suggesting that serial assessment of methylation level in combination with somatic mutation profiling are reliable methods for treatment monitoring. These methods should thus be incorporated with imaging modalities for a more comprehensive work-up of treatment response, particularly for patients treated with targeted therapies.

High-throughput sequencing reveals distinct genetic features and clinical implications of NSCLC with de novo and acquired EGFR T790M mutation.

INTRODUCTION: De novo T790 M mutation in EGFR has been reported in various studies. However, its genetic characteristics and association with EGFR tyrosine kinase inhibitors (TKIs) treatment response remain poorly studied. METHODS: We retrospectively screened 1228 consecutive non-small cell lung cancer (NSCLC) patients and identified 29 de novo T790 M carriers. Capture-based targeted deep sequencing was conducted on 21 eligible samples as well as a 20-sample cohort with acquired T790 M mutation after EGFR-TKIs treatment. We characterized and compared their mutational profiles using a panel consisting of 168 lung cancer-related genes. RESULTS: De novo T790 M mutation was found in 5.8% of the TKI-naive patients harboring EGFR activating mutations. Among the de novo T790 M samples, T790 M was significantly more likely to coexist with L858R than with 19del (76.2% vs. 23.8%) compared to the acquired T790 M cohort (30.0% vs. 70.0%) (p = 0.003). These two groups harbored different concurrent gene mutations as well. Notably, the ratio of allele frequency (AF) of the T790 M mutation to the EGFR activating mutation in each patient, defined as the T790 M relative AF (RAF), differed significantly between the de novo and acquired T790 M cohorts (86.1% vs. 22.3%, p < 0.0001). Among the 10 patients with de novo T790 M who received the 1st-generation EGFR-TKIs treatment, interestingly, the only one who achieved partial response (PR) had the lowest T790 M RAF of 19.7%. The other 9 patients with an average T790 M RAF of 85.9% (±22.6%) achieved stable disease or progressive disease as the best response. One patient, treated with osimertinib after erlotinib failure, achieved PR and the therapeutic response sustained for more than 14.5 months. CONCLUSION: The molecular characteristics of de novo T790 M carriers differ distinctly from acquired T790 M carriers. The RAF of EGFR T790 M mutation may serve as a predictive biomarker for treatment response to EGFR-TKIs. Osimertinib is potentially an effective drug for the treatment of NSCLC with de novo T790 M.

Response to crizotinib in advanced ALK-rearranged non-small cell lung cancers with different ALK-fusion variants.

INTRODUCTION: Anaplastic lymphoma kinase (ALK) rearrangements are present in approximately 5% of non-small-cell lung cancers (NSCLCs). NSCLCs with ALK-rearrangement can be effectively treated with crizotinib. However, magnitude and duration of responses are found to be heterogeneous. This study explored the clinical efficacy of crizotinib in different ALK variants. METHODS: Among 96 ALK-rearrangement patients treated with crizotinib, 60 patients were identified with tumor specimens that could be evaluated by next-generation sequencing (NGS). We retrospectively evaluated the efficacy of crizotinib in different ALK variants. RESULTS: The median Progression-free survival (PFS) of the 96 ALK-rearrangement patients was 14.17 months. Among the 60 patients with NGS results, the most frequent variants were variant 3a/b (33.33%), variant 1 (23.33%) and variant 2 (15.00%). The percentage of rare EML4-ALK variants and non EML4-ALK variants were 10.00% and 18.33%. Survival analysis showed that patients with variant 2 appeared to have longer PFS than others (P = .021); also, patients with TP53 mutation seemed to have an unfavorable PFS than those with TP53 wild-type with a borderline p value (P = .068). After adjusting for other baseline characteristics, EML4-ALK variant 2 was identified as an important factor for a better PFS of crizotinib. We also found that patients with variant 3a/b had shorter duration of response to crizotinib; however, no significant difference of PFS was observed between the PFS of variant3a/b and non-v3 EML4-ALK variants. CONCLUSIONS: Our results indicate prolonged PFS in patients with EML4-ALK variant 2.

Acquired MET Y1248H and D1246N Mutations Mediate Resistance to MET Inhibitors in Non-Small Cell Lung Cancer.

Purpose:MET amplification, responsible for 20% of acquired resistance to EGFR tyrosine kinase inhibitor (TKI) in patients with advanced non-small cell lung cancer (NSCLC), presents an attractive target. Numerous studies have conferred susceptibility of MET mutations and focal amplification to targeted MET-TKIs. However, the mechanism underlying MET-TKIs-induced resistance remains elusive.Experimental Design: We conducted a cohort of 12 patients with advanced NSCLC who developed resistance to a combinatorial therapy consisting of gefitinib and a type I MET-TKI. We performed capture-based targeted ultra-deep sequencing on serial tumor biopsies and plasmas ctDNA samples to detect and quantify genetic alterations.Results: We identified 2 newly acquired MET mutations, Y1248H and D1246N, in 2 patients and further confirmed their resistance against type I MET-TKIs in silco, in vitro, and in vivo Interestingly, NIH3T3 cells harboring either mutation exhibited responses to type II MET-TKIs, suggesting sequential use of MET-TKIs may offer a more durable response. In addition, we also discovered that EGFR amplification may act as an alternative MET-TKI resistance mechanism.Conclusions: Our study provides insight into the diversity of mechanisms underlying MET-TKI-induced resistance and highlights the potential of sequential use of MET-TKIs. Clin Cancer Res; 23(16); 4929-37. ©2017 AACR.

Hobnail variant of papillary thyroid carcinoma: molecular profiling and comparison to classical papillary thyroid carcinoma, poorly differentiated thyroid carcinoma and anaplastic thyroid carcinoma.

BACKGROUND: As a rare but aggressive papillary thyroid carcinoma (PTC) variant, the genetic changes of hobnail variant of PTC (HVPTC) are still unclear. RESULTS: The prevalence of HVPTC was 1.69% (18/1062) of all PTC diagnosed in our cohort. 73 samples from 55 patients (17 HVPTC, 26 CPTC, 7 PDTC and 5 ATC) were successfully analyzed using targeted NGS with an 18-gene panel. Thirty-seven mutation variant types were identified among 11 genes. BRAF V600E mutation was the most common mutation, which is present in almost all HVPTC samples (16/17, 94%), most CPTC samples (20/26, 77%), and none of the ATC and PDTC samples. TERT promoter mutation (C228T) was identified in 2 ATC and one HVPTC patient. RAS and TP53 mutation are almost exclusively present among ATC and PDTC samples although TP53 mutation was also observed in 3 HVPTC patients. Six different GNAS mutations were identified among 8 CPTC patients (31%) and none of the HVPTC patients. The only patient who died of disease progression harbored concomitant TERT C228T mutation, BRAF V600E mutation and TP53 mutation. METHODS: HVPTC cases were identified from a group of 1062 consecutive surgical specimens diagnosed as PTC between 2000 and 2010. Targeted next-generation sequencing (NGS) was applied to investigate the mutation spectrum of HVPTC, compared to classical PTC (CPTC), poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC). CONCLUSION: As an aggressive variant of PTC, HVPTC has relatively specific molecular features, which is somewhat different from both CPTC and ATC/PDTC and may underlie its relatively aggressive behavior.

An allosteric PRC2 inhibitor targeting the H3K27me3 binding pocket of EED.

Polycomb repressive complex 2 (PRC2) consists of three core subunits, EZH2, EED and SUZ12, and plays pivotal roles in transcriptional regulation. The catalytic subunit EZH2 methylates histone H3 lysine 27 (H3K27), and its activity is further enhanced by the binding of EED to trimethylated H3K27 (H3K27me3). Small-molecule inhibitors that compete with the cofactor S-adenosylmethionine (SAM) have been reported. Here we report the discovery of EED226, a potent and selective PRC2 inhibitor that directly binds to the H3K27me3 binding pocket of EED. EED226 induces a conformational change upon binding EED, leading to loss of PRC2 activity. EED226 shows similar activity to SAM-competitive inhibitors in blocking H3K27 methylation of PRC2 target genes and inducing regression of human lymphoma xenograft tumors. Interestingly, EED226 also effectively inhibits PRC2 containing a mutant EZH2 protein resistant to SAM-competitive inhibitors. Together, we show that EED226 inhibits PRC2 activity via an allosteric mechanism and offers an opportunity for treatment of PRC2-dependent cancers.

Capture-Based Targeted Ultradeep Sequencing in Paired Tissue and Plasma Samples Demonstrates Differential Subclonal ctDNA-Releasing Capability in Advanced Lung Cancer.

INTRODUCTION: Circulating tumor DNA (ctDNA), which represents an unbiased way to assess tumor genetic profile noninvasively, facilitates studying intratumor heterogeneity. Although intratumor heterogeneity has been elucidated substantially in a few cancer types, including NSCLC, how it influences the ability of tumor cells harboring different genetic abnormalities in releasing their DNA remains elusive. We designed a capture-based panel targeting NSCLC to detect and quantify genetic alterations from plasma samples by using deep sequencing. By applying the panel to paired biopsy and plasma samples, we imputed and compared the ctDNA-releasing efficiency in subclones harboring distinct genetic variants. METHODS: We collected 40 pairs of matched biopsy and plasma samples from patients with advanced lung cancer and applied capture-based sequencing using our LungPlasma panel, which consists of critical exons and introns of 168 genes. We derived a normalized relative allelic fraction score (NRAFS) to reflect ctDNA-releasing efficiency. RESULTS: By using mutations detected in biopsy samples as a reference, we achieved 87.2% by-variant sensitivity, including for single-nucleotide variants, insertions or deletions, and gene fusions. Furthermore, the by-variant sensitivity for the seven most critical and actionable genes was 96.2%. The average NRAFS for subclones carrying mutations from seven actionable genes was 0.877; in contrast, the average NRAFS for other mutations was 0.658. Mutations from four genes involved in cell cycle pathways had a particularly low NRAFS (0.480) compared with the other two groups (p = 0.07). CONCLUSIONS: We have demonstrated that subclones carrying driver mutations are more prone to release DNA. We have also demonstrated the quantitative ability of capture-based sequencing, paving its way for routine utilization in clinical settings.

Combinational Analysis of FISH and Immunohistochemistry Reveals Rare Genomic Events in ALK Fusion Patterns in NSCLC that Responds to Crizotinib Treatment.

INTRODUCTION: The purpose of this study was to explore the complicated rearrangement mechanisms underlying cases with atypical and negative anaplastic lymphoma receptor tyrosine kinase gene (ALK) fluorescence hybridization (FISH) and positive immunohistochemistry (IHC) results and to stress the importance of combinational assay of these two methods in current pathological diagnosis. METHODS: A total of 3128 NSCLCs were screened for ALK fusions through both FISH analysis and IHC assays with Ventana-D5F3 antibody. Fourteen cases with atypical and negative FISH results with the current criteria and positive IHC results were analyzed with targeted next-generation sequencing (NGS). RESULTS: Of the 3128 cases tested, 228 (7.3%) and 214 (6.8%) were ALK positive by IHC and FISH, respectively. Fourteen cases with negative and atypical FISH results all demonstrated IHC positivity. Of 2991 cases, eight (0.27%) with negative FISH results demonstrated echinoderm microtubule associated protein like 4 gene (EML4)-ALK fusions revealed by targeted NGS, and the relative abundance of fusion ranged from 0.9% to 46.8%. Three of 2991 cases (0.1%) did not exhibit any type of ALK fusions. In addition, two patients showed an isolated 5' side signal and targeted NGS revealed two novel ALK partner genes, baculoviral IAP repeat containing 6 gene (BIRC6) and phosphatidylinositol binding clathrin assembly protein gene (PICALM). One patient showed an isolated and attenuated 3' red signal and demonstrated a novel translocation partner with CCAAT/enhancer binding protein zeta gene (CEBPZ). Of all the patients, four received crizotinib treatment and demonstrated partial responses at the end of follow-up. CONCLUSIONS: Our study showed that patients with negative and atypical ALK FISH patterns may have positive results for IHC testing and harbor the translocation partners of EML4 or other genes. Therefore, additional testing with NGS should be conducted to explore the molecular mechanisms underlying the complicated gene rearrangement events.

Noninvasive genotyping and monitoring of anaplastic lymphoma kinase (ALK) rearranged non-small cell lung cancer by capture-based next-generation sequencing.

Noninvasive genotyping of driver genes and monitoring of tumor dynamics help make better personalized therapeutic decisions. However, neither PCR-based assays nor amplicon-based targeted sequencing can detect fusion genes like anaplastic lymphoma kinase (ALK) rearrangements in blood samples. To investigate the feasibility and performance of capture-based sequencing on ALK fusion detection, we developed a capture-based targeted sequencing panel to detect and quantify rearrangement events, along with other driver mutation variants in plasma. In this perspective study, we screened 364 patients with advanced non-small cell lung cancer (NSCLC) for ALK rearrangements, and collected blood samples from 24 of them with confirmed ALK rearrangements based on their tissue biopsies. ALK rearrangements were successfully detected in 19 of 24 patients at baseline with 79.2% (95% CI 57.9%, 92.9%) sensitivity and 100% (36/36) specificity. Among the 24 patients, we obtained longitudinal blood samples from 7 of them after either chemotherapy and/or Crizotinib treatment for disease monitoring. The by-sample detection rate of ALK rearrangements after treatment drops to 69.2% (9 of 13). In addition to detecting ALK rearrangements, we also detected 3 Crizotinib resistant mutations, ALK L1152R, ALK I1171T and ALK L1196M from patient P4. ctDNA concentration correlates with responses and disease progression, reflecting its ability as a biomarker. Our findings suggest capture-based sequencing can detect and quantify ALK rearrangements as well as other somatic mutations, including mutations mediated drug resistance, in plasma with high sensitivity, paving the way for its application in identifying driver fusion genes and monitoring tumor dynamics in the clinic.

Histone methyltransferase SETDB1 regulates liver cancer cell growth through methylation of p53.

SETDB1 is a histone H3K9 methyltransferase that has a critical role in early development. It is located within a melanoma susceptibility locus and facilitates melanoma formation. However, the mechanism by which SETDB1 regulates tumorigenesis remains unknown. Here we report the molecular interplay between SETDB1 and the well-known hotspot gain-of-function (GOF) TP53 R249S mutation. We show that in hepatocellular carcinoma (HCC) SETDB1 is overexpressed with moderate copy number gain, and GOF TP53 mutations including R249S associate with this overexpression. Inactivation of SETDB1 in HCC cell lines bearing the R249S mutation suppresses cell growth. The TP53 mutation status renders cancer cells dependent on SETDB1. Moreover, SETDB1 forms a complex with p53 and catalyses p53K370 di-methylation. SETDB1 attenuation reduces the p53K370me2 level, which subsequently leads to increased recognition and degradation of p53 by MDM2. Together, we provide both genetic and biochemical evidence for a mechanism by which SETDB1 regulates cancer cell growth via methylation of p53.