Establishment of canine mammary gland tumor cell lines harboring PI3K/Akt activation as a therapeutic target.

Canine mammary gland tumors (MGT) have a poor prognosis in intact female canines, posing a clinical challenge. This study aimed to establish novel canine mammary cancer cell lines from primary tumors and characterize their cellular and molecular features to find potential therapeutic drugs. The MGT cell lines demonstrated rapid cell proliferation and colony formation in an anchorage-independent manner. Vimentin and α-SMA levels were significantly elevated in MGT cell lines compared to normal canine kidney (MDCK) cells, while CDH1 expression was either significantly lower or not detected at all, based on quantitative real-time PCR (qRT-PCR) analysis. Functional annotation and enrichment analysis revealed that epithelial-mesenchymal transition (EMT) phenotypes and tumor-associated pathways, particularly the PI3K/Akt signaling pathway, were upregulated in MGT cells. BYL719 (Alpelisib), a PI3K inhibitor, was also examined for cytotoxicity on the MGT cell lines. The results show that BYL719 can significantly inhibit the proliferation of MGT cell lines in vitro. Overall, our findings suggest that the MGT cell lines may be valuable for future studies on the development, progression, metastasis, and management of tumors.

Mutational evolution after chemotherapy-progression in metastatic colorectal cancer revealed by circulating tumor DNA analysis.

Emerging new mutations after treatment can provide clues to acquired resistant mechanisms. Circulating tumor DNA (ctDNA) sequencing has enabled noninvasive repeated tumor mutational profiling. We aimed to investigate newly emerging mutations in ctDNA after disease progression in metastatic colorectal cancer (mCRC). Blood samples were prospectively collected from mCRC patients receiving palliative chemotherapy before treatment and at radiological evaluations. ctDNA from pretreatment and progressive disease (PD) samples were sequenced with a next-generation sequencing panel targeting 106 genes. A total of 712 samples from 326 patients were analyzed, and 381 pretreatment and PD pairs (163 first-line, 85 second-line and 133 later-line [≥third-line]) were compared. New mutations in PD samples (mean 2.75 mutations/sample) were observed in 49.6% (189/381) of treatments. ctDNA samples from later-line had more baseline mutations (P = .002) and were more likely to have new PD mutations (adjusted odds ratio [OR] 2.27, 95% confidence interval [CI]: 1.40-3.69) compared to first-line. RAS/BRAF wild-type tumors were more likely to develop PD mutations (adjusted OR 1.87, 95% CI: 1.22-2.87), independent of cetuximab treatment. The majority of new PD mutations (68.5%) were minor clones, suggesting an increasing clonal heterogeneity after treatment. Pathways involved by PD mutations differed by the treatment received: MAPK cascade (Gene Ontology [GO]: 0000165) in cetuximab and regulation of kinase activity (GO: 0043549) in regorafenib. The number of mutations revealed by ctDNA sequencing increased during disease progression in mCRC. Clonal heterogeneity increased after chemotherapy progression, and pathways involved were affected by chemotherapy regimens.

Personalised circulating tumour DNA assay with large-scale mutation coverage for sensitive minimal residual disease detection in colorectal cancer.

BACKGROUND: Postoperative minimal residual disease (MRD) detection using circulating-tumour DNA (ctDNA) requires a highly sensitive analysis platform. We have developed a tumour-informed, hybrid-capture ctDNA sequencing MRD assay. METHODS: Personalised target-capture panels for ctDNA detection were designed using individual variants identified in tumour whole-exome sequencing of each patient. MRD status was determined using ultra-high-depth sequencing data of plasma cell-free DNA. The MRD positivity and its association with clinical outcome were analysed in Stage II or III colorectal cancer (CRC). RESULTS: In 98 CRC patients, personalised panels for ctDNA sequencing were built from tumour data, including a median of 185 variants per patient. In silico simulation showed that increasing the number of target variants increases MRD detection sensitivity in low fractions (<0.01%). At postoperative 3-week, 21.4% of patients were positive for MRD by ctDNA. Postoperative positive MRD was strongly associated with poor disease-free survival (DFS) (adjusted hazard ratio 8.40, 95% confidence interval 3.49-20.2). Patients with a negative conversion of MRD after adjuvant therapy showed significantly better DFS (P < 0.001). CONCLUSION: Tumour-informed, hybrid-capture-based ctDNA assay monitoring a large number of patient-specific mutations is a sensitive strategy for MRD detection to predict recurrence in CRC.

Dynamic changes in longitudinal circulating tumour DNA profile during metastatic colorectal cancer treatment.

BACKGROUND: Circulating tumour DNA (ctDNA) has been spotlighted as an attractive biomarker because of its easy accessibility and real-time representation of tumour genetic profile. However, the clinical utility of longitudinal ctDNA monitoring has not been clearly defined. METHODS: Serial blood samples were obtained from metastatic colorectal cancer patients undergoing first-line chemotherapy. ctDNA was sequenced using a targeted next-generation sequencing platform which included 106 genes. Changes in ctDNA profile and treatment outcome were comprehensively analysed. RESULTS: A total of 272 samples from 62 patients were analysed. In all, 90.3% of patients had detectable ctDNA mutation before treatment. ctDNA clearance after chemotherapy was associated with longer progression-free survival which was independent of radiological response (adjusted hazard ratio 0.22, 95% confidence interval 0.10-0.46). Longitudinal monitoring was able to detect ctDNA progression which preceded radiological progressive disease (PD) in 58.1% (median 3.3 months). Diverse resistant mutations (34.9%) and gene amplification (7.0%) at the time of PD were discovered. For 16.3% of the PD patients, the newly identified mutations could be potential candidates of targeted therapy or clinical trial. CONCLUSION: ctDNA profile provided a more accurate landscape of tumour and dynamic changes compared to radiological evaluation. Longitudinal ctDNA monitoring may improve personalised treatment decision-making.

Phenotype-based single cell sequencing identifies diverse genetic subclones in CD133 positive cancer stem cells.

Tumor heterogeneity is one of the ongoing huddles in the field of colon cancer therapy. It is evident that there are countless clones which exhibit different phenotypes and therefore, single cell analysis is inevitable. Cancer stem cells (CSCs) are rare cell population within tumor which is known to function in cancer metastasis and recurrence. Although there have been trials to prove intra-tumoral heterogeneity using single cell sequencing, that of CSCs has not been clearly elucidated. Here, we articulate the presence of heterogeneous subclones within CD133 positive cancer stem cells through single cell sequencing. As a proof of principle, we performed phenotype-based high-throughput laser isolation and single cell sequencing (PHLI-seq) of CD133 positive cells in a frozen tumor tissue obtained from a patient with colorectal cancer. The result proved that CD133 positive cells were shown to be heterogeneous both in copy number and mutational profiles. Single cancer stem cell specific mutations such as RNF144A, PAK2, PARP4, ADAM21, HYDIN, KRT38 and CELSR1 could be also detected in liver metastatic tumor of the same patient. Collectively, these data suggest that single cell analysis used to spot subclones with genetic variation within rare population, will lead to new strategies to tackle colon cancer metastasis.

Activation of WNT/ß-catenin signaling results in resistance to a dual PI3K/mTOR inhibitor in colorectal cancer cells harboring PIK3CA mutations.

PIK3CA is a frequently mutated gene in cancer, including about ~15 to 20% of colorectal cancers (CRC). PIK3CA mutations lead to activation of the PI3K/AKT/mTOR signaling pathway, which plays pivotal roles in tumorigenesis. Here, we investigated the mechanism of resistance of PIK3CA-mutant CRC cell lines to gedatolisib, a dual PI3K/mTOR inhibitor. Out of a panel of 29 CRC cell lines, we identified 7 harboring one or more PIK3CA mutations; of these, 5 and 2 were found to be sensitive and resistant to gedatolisib, respectively. Both of the gedatolisib-resistant cell lines expressed high levels of active glycogen synthase kinase 3-beta (GSK3ß) and harbored the same frameshift mutation (c.465_466insC; H155fs*) in TCF7, which encodes a positive transcriptional regulator of the WNT/ß-catenin signaling pathway. Inhibition of GSK3ß activity in gedatolisib-resistant cells by siRNA-mediated knockdown or treatment with a GSK3ß-specific inhibitor effectively reduced the activity of molecules downstream of mTOR and also decreased signaling through the WNT/ß-catenin pathway. Notably, GSK3ß inhibition rendered the resistant cell lines sensitive to gedatolisib cytotoxicity, both in vitro and in a mouse xenograft model. Taken together, these data demonstrate that aberrant regulation of WNT/ß-catenin signaling and active GSK3ß induced by the TCF7 frameshift mutation cause resistance to the dual PI3K/mTOR inhibitor gedatolisib. Cotreatment with GSK3ß inhibitors may be a strategy to overcome the resistance of PIK3CA- and TCF7-mutant CRC to PI3K/mTOR-targeted therapies.

Association of pathway mutation with survival after recurrence in colorectal cancer patients treated with adjuvant fluoropyrimidine and oxaliplatin chemotherapy.

BACKGROUND: Although the prognostic biomarkers associated with colorectal cancer (CRC) survival are well known, there are limited data on the association between the molecular characteristics and survival after recurrence (SAR). The purpose of this study was to assess the association between pathway mutations and SAR. METHODS: Of the 516 patients with stage III or high risk stage II CRC patients treated with surgery and adjuvant chemotherapy, 87 who had distant recurrence were included in the present study. We analyzed the association between SAR and mutations of 40 genes included in the five critical pathways of CRC (WNT, P53, RTK-RAS, TGF-ß, and PI3K). RESULTS: Mutation of genes within the WNT, P53, RTK-RAS, TGF-ß, and PI3K pathways were shown in 69(79.3%), 60(69.0%), 57(65.5%), 21(24.1%), and 19(21.8%) patients, respectively. Patients with TGF-ß pathway mutation were younger and had higher incidence of mucinous adenocarcinoma (MAC) histology and microsatellite instability-high. TGF-ß pathway mutation (median SAR of 21.6 vs. 44.4 months, p = 0.021) and MAC (20.0 vs. 44.4 months, p = 0.003) were associated with poor SAR, and receiving curative resection after recurrence was associated with favorable SAR (Not reached vs. 23.6 months, p <  0.001). Mutations in genes within other critical pathways were not associated with SAR. When MAC was excluded as a covariate, multivariate analysis revealed TGF-ß pathway mutation and curative resection after distant recurrence as an independent prognostic factor for SAR. The impact of TGF-ß pathway mutations were predicted using the PROVEAN, SIFT, and PolyPhen-2. Among 25 mutations, 23(92.0%)-24(96.0%) mutations were predicted to be damaging mutation. CONCLUSIONS: Mutation in genes within TGF-ß pathway may have negative prognostic role for SAR in CRC. Other pathway mutations were not associated with SAR.

Association Between Fusobacterium nucleatum, Pathway Mutation, and Patient Prognosis in Colorectal Cancer.

BACKGROUND: There is a close link between Fusobacterium nucleatum and colorectal cancer (CRC) tumorigenesis and chemoresistance. However, the genetic characteristics and clinical significance of CRC related with F. nucleatum remains unclear. This study evaluated the relationship between F. nucleatum, pathway mutation, and patient prognosis. METHODS: Fusobacterium nucleatum amount in the tumor tissue and adjacent normal tissue were measured by quantitative polymerase chain reaction in adjuvant (N = 128) and metastatic (N = 118) cohorts. Patients were divided into binary (F. nucleatum-high and F. nucleatum-low) according to F. nucleatum amount. Targeted next-generation sequencing of 40 genes included in the 5 critical pathways (WNT, P53, RTK-RAS, PI3 K, and TGF-ß) was performed in the adjuvant cohort. RESULTS: Patients with MSI-H and CIMP-H had higher amount of F. nucleatum in tumor tissue. Fusobacterium nucleatum-high patients had higher rates of transition mutation and C to T (G to A) nucleotide change regardless of MSI status. In addition, mutation rate of AMER1 and ATM genes, and TGF-ß pathway was higher in F. nucleatum-high patients. Fusobacterium nucleatum-high was associated with poor overall survival (OS) in the palliative cohort (26.4 vs. 30.7 months, p = 0.042). Multivariate analysis revealed F. nucleatum-high as an independent negative prognostic factor for OS [adjusted hazard ratio of 1.69 (95% confidence interval 1.04-2.75), p = 0.034]. However, F. nucleatum amount was not associated with recurrence in the adjuvant cohort. CONCLUSIONS: F. nucleatum-high was associated with poor survival in metastatic CRC. In addition, we identified mutational characteristics of colorectal cancer according to F. nucleatum amount.

Dynamic cohesin-mediated chromatin architecture controls epithelial-mesenchymal plasticity in cancer.

Epithelial to mesenchymal transition (EMT) and mesenchymal to epithelial transition (MET) are important interconnected events in tumorigenesis controlled by complex genetic networks. However, the cues that activate EMT-initiating factors and the mechanisms that reversibly connect EMT/MET are not well understood. Here, we show that cohesin-mediated chromatin organization coordinates EMT/MET by regulating mesenchymal genes. We report that RAD21, a subunit of the cohesin complex, is expressed in epithelial breast cancer cells, whereas its expression is decreased in mesenchymal cancer. Depletion of RAD21 in epithelial cancer cells causes transcriptional activation of TGFB1 and ITGA5, inducing EMT. Reduced binding of RAD21 changes intrachromosomal chromatin interactions within the TGFB1 and ITGA5 loci, creating an active transcriptional environment. Similarly, stem cell-like cancer cells also show an open chromatin structure at both genes, which correlates with high expression levels and mesenchymal fate characteristics. Conversely, overexpression of RAD21 in mesenchymal cancer cells induces MET-specific expression patterns. These findings indicate that dynamic cohesin-mediated chromatin structures are responsible for the initiation and regulation of essential EMT-related cell fate changes in cancer.

Reduced cohesin destabilizes high-level gene amplification by disrupting pre-replication complex bindings in human cancers with chromosomal instability.

Gene amplification is a hallmark of cancer with chromosomal instability although the underlying mechanism by which altered copy numbers are maintained is largely unclear. Cohesin, involved in sister chromatid cohesion, DNA repair, cell cycle progression and transcriptional regulation of key developmental genes, is frequently overexpressed in human cancer. Here we show that cohesin-dependent change in DNA replication controls the copy numbers of amplified genes in cancer cells with chromosomal instability. We found that the down-regulation of elevated cohesin leads to copy number-associated gene expression changes without disturbing chromosomal segregation. Highly amplified genes form typical long-range chromatin interactions, which are stabilized by enriched cohesin. The spatial proximities among cohesin binding sites within amplified genes are decreased by RAD21-knockdown, resulting in the rapid decline of amplified gene expression. After several passages, cohesin depletion inhibits DNA replication initiation by reducing the recruitment of pre-replication complexes such as minichromosome maintenance subunits 7 (MCM7), DNA polymerase α, and CDC45 at replication origins near the amplified regions, and as a result, decreases the DNA copy numbers of highly amplified genes. Collectively, our data demonstrate that cohesin-mediated chromatin organization and DNA replication are important for stabilizing gene amplification in cancer cells with chromosomal instability.

Association between mutations of critical pathway genes and survival outcomes according to the tumor location in colorectal cancer.

BACKGROUND: Colorectal cancer (CRC) develops through the alteration of several critical pathways. This study was aimed at evaluating the influence of critical pathways on survival outcomes for patients with CRC. METHODS: Targeted next-generation sequencing of 40 genes included in the 5 critical pathways of CRC (WNT, P53, RTK-RAS, phosphatidylinositol-4,5-bisphosphate 3-kinase [PI3K], and transforming growth factor ß [TGF-ß]) was performed for 516 patients with stage III or high-risk stage II CRC treated with surgery followed by adjuvant fluoropyrimidine and oxaliplatin chemotherapy. The associations between critical pathway mutations and relapse-free survival (RFS) and overall survival were analyzed. The associations were further analyzed according to the tumor location. RESULTS: The mutation rates for the WNT, P53, RTK-RAS, PI3K, and TGF-ß pathways were 84.5%, 69.0%, 60.7%, 30.0%, and 28.9%, respectively. A mutation in the PI3K pathway was associated with longer RFS (adjusted hazard ratio [HR], 0.59; 95% confidence interval [CI], 0.36-0.99), whereas a mutation in the RTK-RAS pathway was associated with shorter RFS (adjusted HR, 1.60; 95% CI, 1.01-2.52). Proximal tumors showed a higher mutation rate than distal tumors, and the mutation profile was different according to the tumor location. The mutation rates of Kirsten rat sarcoma viral oncogene homolog (KRAS), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit α (PIK3CA), and B-Raf proto-oncogene serine/threonine kinase (BRAF) were higher in proximal tumors, and the mutation rates of adenomatous polyposis coli (APC), tumor protein 53 (TP53), and neuroblastoma RAS viral oncogene homolog (NRAS) were higher in distal tumors. The better RFS with the PI3K pathway mutation was significant only for proximal tumors, and the worse RFS with the RTK-RAS pathway mutation was significant only for distal tumors. CONCLUSIONS: A PI3K pathway mutation was associated with better RFS for CRC patients treated with adjuvant chemotherapy, and an RTK-RAS pathway mutation was associated with worse RFS. The significance of the prognostic impact differed according to the tumor location. Cancer 2017;123:3513-23. © 2017 American Cancer Society.

Identification of long-range epigenetic silencing on chromosome 15q25 and its clinical implication in gastric cancer.

Recent genome-wide epigenomic and transcription profiling studies have demonstrated that epigenetic silencing can encompass multiple neighboring genes, termed as long-range epigenetic silencing (LRES). Herein, we identified a novel LRES region by comparing gene expression of human colon cancer HCT116 cells with their DNA methyltransferase 1 and DNA methyltransferase 3B double-knockout derivative double-knockout cells. Ten consecutive genes spanning 3 Mb of chromosome 15q25 were coordinately silenced, with eight genes showing promoter CpG island hypermethylation and enrichment of repressive histone marks, which were evaluated by bisulfite sequencing analysis and chromatin immunoprecipitation assay. Comparison of primary gastric tumor specimens with normal tissue confirmed that the long-range silencing of this region was tumor specific. Methylation of genes within the LRES region was evaluated in 190 gastric tumor tissues using the MethyLight assay, and their association with clinicopathological features, such as older age, high-grade differentiation, and diffuse or mixed-type histology, was determined. LRES-positive gastric cancer patients (six or more methylated genes) showed lower recurrence and better survival. Our findings emphasize the differential dynamics of DNA methylation and histone modification, indicating the importance of studying the relationship of each epigenetic modification in the context of chromatin domains. Patients with LRES showed lower recurrence and better prognosis, indicating that stratifying patients according to underlying molecular features, such as LRES regions, may better predict recurrence and survival.

Predicting disease recurrence in limited disease small cell lung cancer using cell-free DNA-based mutation and fragmentome analyses.

Background: Limited disease (LD) small cell lung cancer (SCLC) treated with definitive concurrent chemoradiotherapy (CCRT) potentially experience disease recurrence. We investigated the feasibility of circulating-tumor DNA (ctDNA)-based genomic and fragmentome analyses to assess the risk of recurrence. Methods: Targeted sequencing was conducted using pre-treatment and on-treatment blood samples from definitive CCRT-treated patients with LD-SCLC (n=50). Based on 12-month recurrence-free survival (RFS), patients were categorized into persistent-response (PeR, n=29) and non-PeR (n=21) groups. Fragmentome analysis was conducted using ctDNA fragments of different lengths: P1 (100-155 bp) and P2 (160-180 bp). Results: Patients with TP53 (n=15) and RB1 (n=11) mutation in on-treatment samples demonstrated significantly shorter RFS than patients with wild-type (WT) (P=0.05, P=0.0014, respectively). Fragmentome analysis of all available on-treatment samples (n=26) revealed that the non-PeR group (n=10) had a significantly higher P1 range (P=0.003) and lower P2 range (P=0.002). The areas under the curves for P1, P2, and the fragmentation ratio (P1/P2) in distinguishing the PeR and non-PeR were 0.850, 0.725, and 0.900, respectively. Using optimal cut-off, longer RFSs were found with the low-fragmentation-ratio group than with the high-fragmentation-ratio group (not reached vs. 7.6 months, P=0.002). Patients with both WT RB1 and a low-fragmentation-ratio (n=10) showed better outcomes than patients with both mutated RB1 and a high-fragmentation-ratio (n=10; hazard ratio, 7.55; 95% confidence interval: 2.14-26.6; P=0.002). Conclusions: RB1 mutations and high fragmentation ratios correlated with early disease recurrence. Analyzing ctDNA could help in predicting early treatment failure and making clinical decisions for high-risk patients.

Analytical and Clinical Validation of a Highly Sensitive NGS-Based ctDNA Assay with Real-World Concordance in Non-Small Cell Lung Cancer.

PURPOSE: There have been needs to improve the sensitivity of liquid biopsy. This report aims to report the analytical and clinical validation of a next-generation sequencing (NGS)-based circulating tumor DNA (ctDNA) assay. MATERIALS AND METHODS: Analytical validation was conducted in vitro by evaluating the limit of detection (LOD), precision, and specificity for various genomic aberrations. The real-world performance in non-small cell lung cancer (NSCLC) was assessed by comparing the results of AlphaLiquid100 to the tissue-based results. RESULTS: The LODs with 30 ng input DNA were 0.11%, 0.11%, 0.06%, 0.21%, and 2.13 copies for detecting single nucleotide variants, insertions, deletions, fusions, and copy number alterations (CNA), respectively. Quantitatively, single nucleotide variants/insertions and deletions, fusions, and CNAs showed a good correlation (R2=0.91, 0.40, and 0.65; y=0.95, 1.06, and 1.19) to the manufacturer's values, and per-base specificities for all types of variants were near 100%. In real-world NSCLC (n=122), key actionable mutations in NSCLC were detected in 60.7% (74/122) with the ctDNA assay. Comparative analysis against the NGS-based tissue results for all key mutations showed positive percent agreement (PPA) of 85.3%. For individual genes, the PPA was as high as 95.7% for epidermal growth factor receptor (EGFR) mutations and 83.3% for ALK translocations. AlphaLiquid100 detected drug-sensitive EGFR mutation at a variant allele frequency as low as 0.02% and also identified an EGFR mutation in a case where tissue sample missed. Blood samples collected post-targeted therapies revealed additional acquired mutations. CONCLUSION: The AlphaLiquid100 ctDNA assay demonstrates robust analytical validity, offering clinically important information for NSCLC patients.

Proteomic analysis reveals that CD147/EMMPRIN confers chemoresistance in cancer stem cell-like cells.

Cancer stem cells (CSCs) are a subpopulation of tumor cells that can self-renew, metastasize, and promote cancer recurrence. A comprehensive characterization of the CSC proteome has been hampered due to their scarcity and rapid differentiation. Here, we present a systematic analysis of the cell-surface proteome using a CSC-like cell line derived from MDA-MB453 breast cancer cells, which exhibited a CD44(+) /CD24(-) (where CD is cluster of differentiation) phenotype and chemoresistance. We identified differentially expressed proteins in CSC-like cells, including upregulated plasma membrane proteins such as CD44, CD133, epidermal growth factor receptor (EGFR), CD147, cadherin 1, integrins, and catenin (cadherin-associated protein), beta 1 (CTNNB1), using an in-situ biotinylation approach followed by MS analysis. We examined the role of CD147 in the promotion of CSC growth and survival, and demonstrated that inhibition of CD147 with a monoclonal antibody induced significant inhibition of cell growth. siRNA-mediated silencing of CD147 gene expression restored the sensitivity of CSC-like cells to 5-fluorouracil (5-FU), along with decreasing the expression of thymidylate synthase, p-AKT, and ß-catenin, while increasing the expression of p-glycogen synthase kinase (GSK)3ß. Increased CD147 expression in the CSC-like cells, as seen by proteomic analysis, and the functional consequences of CD147 overexpression in CSC-like cells suggest that CD147 may be one of the critical cell-surface proteins involved in promoting chemoresistance and survival in CSCs.

Gefitinib resistance of cancer cells correlated with TM4SF5-mediated epithelial-mesenchymal transition.

Although cancers can be initially treated with the epidermal growth factor receptor (EGFR) inhibitor, gefitinib, continued gefitinib therapy does not benefit the survival of patients due to acquired resistance through EGFR mutations, c-MET amplification, or epithelial-mesenchymal transition (EMT). It is of further interest to determine whether mesenchymal-like, but not epithelial-like, cancer cells can become resistant to gefitinib by bypassing EGFR signaling and acquiring alternative routes of proliferative and survival signaling. Here we examined whether gefitinib resistance of cancer cells can be caused by transmembrane 4 L six family member 5 (TM4SF5), which has been shown to induce EMT via cytosolic p27Kip1 stabilization. Gefitinib-resistant cells exhibited higher and/or sustained TM4SF5 expression, cytosolic p27Kip1 stabilization, and mesenchymal phenotypes, compared with gefitinib-sensitive cells. Conversion of gefitinib-sensitive to -resistant cells by introduction of the T790M EGFR mutation caused enhanced and sustained expression of TM4SF5, phosphorylation of p27Kip1 Ser10 (responsible for cytosolic location), loss of E-cadherin from cell-cell contacts, and gefitinib-resistant EGFR and survival signaling activities. Additionally, TM4SF5 overexpression lessened the sensitivity of NSCLC cells to gefitinib. Suppression of TM4SF5 or p27Kip1 in gefitinib-resistant cells via the T790M EGFR mutation or TM4SF5 expression rendered them gefitinib-sensitive, displaying more epithelial-like and less mesenchymal-like characteristics. Together, these results indicate that TM4SF5-mediated EMT may have an important function in the gefitinib resistance of cancer cells.

EBS-seq: enrichment-based method for accurate analysis of 5-hydroxymethylcytosine at single-base resolution.

BACKGROUND: A growing body of research has emphasized 5-hydroxymethylcytosine (5hmC) as an important epigenetic mark. High-resolution methods to detect 5hmC require high sequencing depth and are therefore expensive. Many studies have used enrichment-based methods to detect 5hmC; however, conventional enrichment-based methods have limited resolution. To overcome these limitations, we developed EBS-seq, a cost-efficient method for 5hmC detection with single-base resolution that combines the advantages of high-resolution methods and enrichment-based methods. RESULTS: EBS-seq uses selective labeling of 5hmC, deamination of cytosine and 5-methylcytosine, pull-down of labeled 5hmC, and C-to-T conversion during DNA amplification. Using this method, we profiled 5hmC in HEK293T cells and two colorectal cancer samples. Compared with conventional enrichment-based 5hmC detection, EBS-seq improved 5hmC signals by localizing them at single-base resolution. Furthermore, EBS-seq was able to determine 5hmC levels in CpG-dense regions where distortion of signals can occur, such as CpG islands and CpG shores. Comparing EBS-seq and conventional high-resolution 5hmC detection by ACE-seq, we showed that EBS-seq is more effective at finding 5hmC sites. Using EBS-seq, we found strong associations between gene expression and gene-body 5hmC content in both HEK293T cells and colorectal cancer samples. CONCLUSIONS: EBS-seq is a reliable and cost-efficient method for 5hmC detection because it simultaneously enriches 5hmC-containing DNA fragments and localizes 5hmC signals at single-base resolution. This method is a promising choice for 5hmC detection in challenging clinical samples with low 5hmC levels, such as cancer tissues.

Accurate Detection of Urothelial Bladder Cancer Using Targeted Deep Sequencing of Urine DNA.

Patients with hematuria are commonly given an invasive cystoscopy test to detect bladder cancer (BC). To avoid the risks associated with cystoscopy, several urine-based methods for BC detection have been developed, the most prominent of which is the deep sequencing of urine DNA. However, the current methods for urine-based BC detection have significant levels of false-positive signals. In this study, we report on uAL100, a method to precisely detect BC tumor DNA in the urine without tumor samples. Using urine samples from 43 patients with BC and 21 healthy donors, uAL100 detected BC with 83.7% sensitivity and 100% specificity. The mutations identified in the urine DNA by uAL100 for BC detection were highly associated with BC tumorigenesis and progression. We suggest that uAL100 has improved accuracy compared to other urine-based methods for early BC detection and can reduce unnecessary cystoscopy tests for patients with hematuria.

Practical Utility of Liquid Biopsies for Evaluating Genomic Alterations in Castration-Resistant Prostate Cancer.

Traditional tissue-based assessments of genomic alterations in castration-resistant prostate cancer (CRPC) can be challenging. To evaluate the real-world clinical utility of liquid biopsies for the evaluation of genomic alterations in CRPC, we preemptively collected available plasma samples and archival tissue samples from patients that were being treated for clinically confirmed CRPC. The cell-free DNA (cfDNA) and tumor tissue DNA were analyzed using the AlphaLiquid®100-HRR panel. Plasma samples from a total of 87 patients were included in this study. Somatic mutations from cfDNA were detected in 78 (89.7%) patients, regardless of the presence of overt metastasis or concomitant treatment given at the time of plasma sample collection. Twenty-three patients were found to have known deleterious somatic or germline mutations in HRR genes from their cfDNA. Archival tissue samples from 33 (37.9%) patients were available for comparative analysis. Tissue sequencing was able to yield an NGS result in only 51.5% of the tissue samples. The general sensitivity of cfDNA for detecting somatic mutations in tissues was 71.8%, but important somatic/germline mutations in HRR genes were found to have a higher concordance (100%). Liquid biopsies can be a reasonable substitute for tissue biopsies in CRPC patients when evaluating genomic alterations.

Circulating Tumor DNA Dynamics and Treatment Outcome of Regorafenib in Metastatic Colorectal Cancer.

PURPOSE: Circulating tumor DNA (ctDNA) is emerging as a valuable non-invasive tool to identify tumor heterogeneity and tumor burden. This study investigated ctDNA dynamics in metastatic colorectal cancer patients treated with regorafenib. Materials and Methods: In this prospective biomarker study, plasma cell-free DNA (cfDNA) samples obtained at baseline, at the first response evaluation after 2 cycles of treatment, and at the time of progressive disease were sequenced using a targeted next-generation sequencing platform which included 106 genes. RESULTS: A total of 285 blood samples from 110 patients were analyzed. Higher baseline cfDNA concentration was associated with worse progression-free survival (PFS) and overall survival (OS). After 2 cycles of treatment, variant allele frequency (VAF) in the majority of ctDNA mutations decreased with a mean relative change of -31.6%. Decreases in the VAF of TP53, APC, TCF7L2, and ROS1 after 2 cycles of regorafenib were associated with longer PFS. We used the sum of VAF at each time point as a surrogate for the overall ctDNA burden. A reduction in sum (VAF) of ≥ 50% after 2 cycles was associated with longer PFS (6.1 vs. 2.7 months, p=0.002), OS (11.3 vs. 5.9 months, p=0.001), and higher disease control rate (86.3% vs. 51.1%, p < 0.001). VAF of the majority of the ctDNA mutations increased at the time of disease progression, and VAF of BRAF increased markedly. CONCLUSION: Reduction in ctDNA burden as estimated by sum (VAF) could be used to predict treatment outcome of regorafenib.