Genomic profiling of biliary tract cancers to reveal clinically actionable genes and therapeutic biomarkers.

2021 ◽  
Vol 39 (15_suppl) ◽  
pp. e16187-e16187
Author(s):  
Yang Shao ◽  
Qiuxiang Ou ◽  
Zhenhao Fang ◽  
Rui Liu ◽  
Hua Bao ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Genomic Instability ◽  
Biliary Tract ◽  
Large Scale ◽  
Excision Repair ◽  
State Transitions ◽  
Pathway Enrichment Analysis ◽  
Distal Cholangiocarcinoma ◽  
Tract Cancer

e16187 Background: Bile tract cancers are genetically and clinically heterogenous with a poor prognosis. Identifying novel biomarkers for targeted therapy is required to improve the clinical outcome of bile tract cancer patients. Methods: Tumor tissue samples of 482 Chinese biliary tract cancer (BTC) patients were genetically profiled using targeted next generation sequencing. Tumor mutation burden (TMB) was calculated by counting all nonsynonymous mutations per megabase of coding sequences. The R package ReactomePA was used in pathway enrichment analysis. Genomic instability was characterized by an in-house developed NGS-based Homologous Recombination Deficiency (HRD) panel and a HRD score was an unweighted sum of loss of heterozygosity (LOH), telomeric allelic imbalance (TAI), and large-scale state transitions (LST) scores. Results: The BTC cohort consisted of 135 gallbladder cancer (GBC), 73 intrahepatic cholangiocarcinoma (iCCA), 18 distal cholangiocarcinoma (dCCA), 14 perihilar cholangiocarcinoma (pCCA), while the remaining 242 BTC patients of no specific subtype information. Most frequently mutated genes included TP53 (56%), KRAS (25%), ARID1A (17%), SMAD4 (11%), and CDKN2A (10%) . A preliminary pathway analysis revealed that mutations of DNA damage repair (DDR) pathway genes were enriched in the cohort ( p< 1e-10), accounting for over 70% of the patients, particularly in homologous recombination repair (HRR), Fanconi anemia (FA), mismatch repair (MMR), and base excision repair (BER) genes. More specifically, approximately 50% of the cohort carried at least one mutation of the HRR genes (43%) or MMR genes (14%). Patients with impaired MMR had increased microsatellite instability status (MSI) comparing to those with wildtype MMR (33% vs. 3.1%, p< 0.0001), and patients harboring HRR mutations demonstrated elevated genomic instability than those without such mutations (median HRD: 18 vs.14, p < 0.05), indicative of potential response to poly (ADP-ribose) polymerase (PARP) inhibitors and other DNA-damage agents. Furthermore, high TMB was found to be highly correlated with DDR gene alterations ( p =0.004). In addition, we observed higher mutation frequencies of BRCA1/2 genes (including somatic and germline) in GBCs in contrast to other BTC subtypes. Conclusions: We herein reported the genomic features of 482 Chinese BTC samples and highlighted the role of DDR pathways including HRR and MMR. These findings could be useful to establish treatment and diagnostic strategies for BTC patients based on genetic information.

Hrd in ovarian cancer: Defined today, evolving for the future.

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. e18052-e18052
Author(s):  
Markus Eckstein ◽  
Kenneth Joel Bloom ◽  
Peter Riccelli ◽  
Frank Policht ◽  
Derry Mae Keeling ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Homologous Recombination ◽  
Genomic Instability ◽  
Large Scale ◽  
Gene Mutations ◽  
Therapy Response ◽  
State Transitions ◽  
Data Set ◽  
Gene Target ◽  
Increased Risk

e18052 Background: Homologous Recombination Repair (HRR) gene mutations result in Homologous Recombination Deficiency (HRD) associated with increased risk of high grade serous ovarian (HGOC) cancer and subsequent response to PARP inhibitors (PARPi). Traditionally, HRD has been determined by testing for germline and/or somatic BRCA1/2 mutations. Today, a growing number of HRR gene mutations are known to result in HRD and genomic instability, thus being a suitable target for PARPi. Therapy response to PARPi is highest in BRCA-mutant followed by HRD+/non-BRCA-mutant HGOC. Today, no standard HRD testing methods exist, causing confusion for physicians, and leading to poor outcomes for missed PARPi eligible patients. Thus, there is need to understand HRD testing utilization and methods in HGOC to inform best practices and optimize HRD testing in the clinic. Methods: We assessed the testing landscape for determining HRD status in ovarian cancer using a data set of 8,400 newly diagnosed and metastatic ovarian cancer patients in the US from Q3-2018 through Q2-2019 identified from Diaceutics’ proprietary Global Diagnostic Index (GDI). Analysis of real-world BRCA1/2 and NGS associated testing data and laboratory profile mapping exercise of 82 US labs was carried out using Diaceutics proprietary methods and data sources to evaluate BRCA1/2 and/or HRD germline/somatic testing rates, test availability, and test panel HRR gene composition. Results: Overall, germline mutation testing rates were 3x greater than somatic testing rates. Excluding BRCA1/2, 67 labs offered comprehensive solid tumor NGS panels capable of measuring HRD with varied HRR gene target composition. Across 34 labs, 5 HRR genes were commonly found on panels: PALB2, ATM, BARD1, BRIP1 and CHEK2. 3 labs currently offering panels explicitly intended for HRD determination only include BRCA1/2 and at least one genomic instability marker (loss of heterozygosity, large-scale state transitions or telomeric allelic imbalance). Conclusions: Lack of standardized HRD panels and low testing rate identifying patients with somatic mutations in BRCA1/2 and other HRR genes is leading to poorer outcomes for missed patients eligible for PARPi’s. As clinical evidence linking HRD status with PARPi efficacy grows in ovarian as well as prostate and pancreatic cancer, Diaceutics recommends organizations such as ASCO, CAP or AMP establish defined universal HRD testing panels including relevant somatic/germline HRR genes and BRCA1/2 as well as genomic instability markers and educate stake holders aiding harmonization and ultimately, better treatment outcomes.

scholarly journals PARP Inhibitor Olaparib Causes No Potentiation of the Bleomycin Effect in VERO Cells, Even in the Presence of Pooled ATM, DNA-PK, and LigIV Inhibitors

2020 ◽  
Vol 21 (21) ◽  
pp. 8288
Author(s):  
Valentina Perini ◽  
Michelle Schacke ◽  
Pablo Liddle ◽  
Salomé Vilchez-Larrea ◽  
Deborah J. Keszenman ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Synthetic Lethality ◽  
Excision Repair ◽  
Parp Inhibitor ◽  
Genotoxic Stress ◽  
Vero Cells ◽  
Limiting Factor ◽  
Parp Activation ◽  
Alternative Hypotheses

Poly(ADP-ribosyl)polymerase (PARP) synthesizes poly(ADP-ribose) (PAR), which is anchored to proteins. PAR facilitates multiprotein complexes’ assembly. Nuclear PAR affects chromatin’s structure and functions, including transcriptional regulation. In response to stress, particularly genotoxic stress, PARP activation facilitates DNA damage repair. The PARP inhibitor Olaparib (OLA) displays synthetic lethality with mutated homologous recombination proteins (BRCA-1/2), base excision repair proteins (XRCC1, Polβ), and canonical nonhomologous end joining (LigIV). However, the limits of synthetic lethality are not clear. On one hand, it is unknown whether any limiting factor of homologous recombination can be a synthetic PARP lethality partner. On the other hand, some BRCA-mutated patients are not responsive to OLA for still unknown reasons. In an effort to help delineate the boundaries of synthetic lethality, we have induced DNA damage in VERO cells with the radiomimetic chemotherapeutic agent bleomycin (BLEO). A VERO subpopulation was resistant to BLEO, BLEO + OLA, and BLEO + OLA + ATM inhibitor KU55933 + DNA-PK inhibitor KU-0060648 + LigIV inhibitor SCR7 pyrazine. Regarding the mechanism(s) behind the resistance and lack of synthetic lethality, some hypotheses have been discarded and alternative hypotheses are suggested.

scholarly journals Mph1p promotes gross chromosomal rearrangement through partial inhibition of homologous recombination

2008 ◽  
Vol 181 (7) ◽  
pp. 1083-1093 ◽  
Author(s):  
Soma Banerjee ◽  
Stephanie Smith ◽  
Ji-Hyun Oum ◽  
Hung-Jiun Liaw ◽  
Ji-Young Hwang ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Genomic Instability ◽  
Chromosomal Rearrangement ◽  
Protein A ◽  
Replication Protein A ◽  
Dna Helicase ◽  
Double Strand Breaks ◽  
Methyl Methanesulfonate ◽  
Strand Breaks

Gross chromosomal rearrangement (GCR) is a type of genomic instability associated with many cancers. In yeast, multiple pathways cooperate to suppress GCR. In a screen for genes that promote GCR, we identified MPH1, which encodes a 3′–5′ DNA helicase. Overexpression of Mph1p in yeast results in decreased efficiency of homologous recombination (HR) as well as delayed Rad51p recruitment to double-strand breaks (DSBs), which suggests that Mph1p promotes GCR by partially suppressing HR. A function for Mph1p in suppression of HR is further supported by the observation that deletion of both mph1 and srs2 synergistically sensitize cells to methyl methanesulfonate-induced DNA damage. The GCR-promoting activity of Mph1p appears to depend on its interaction with replication protein A (RPA). Consistent with this observation, excess Mph1p stabilizes RPA at DSBs. Furthermore, spontaneous RPA foci at DSBs are destabilized by the mph1Δ mutation. Therefore, Mph1p promotes GCR formation by partially suppressing HR, likely through its interaction with RPA.

scholarly journals Srs2 Plays a Critical Role in Reversible G2 Arrest upon Chronic and Low Doses of UV Irradiation via Two Distinct Homologous Recombination-Dependent Mechanisms in Postreplication Repair-Deficient Cells

2010 ◽  
Vol 30 (20) ◽  
pp. 4840-4850 ◽  
Author(s):  
Takashi Hishida ◽  
Yoshihiro Hirade ◽  
Nami Haruta ◽  
Yoshino Kubota ◽  
Hiroshi Iwasaki
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Excision Repair ◽  
Critical Role ◽  
Nuclear Antigen ◽  
Dna Damage Tolerance ◽  
Checkpoint Activation ◽  
Postreplication Repair ◽  
Nucleotide Excision ◽  
Proliferating Cell

ABSTRACT Differential posttranslational modification of proliferating cell nuclear antigen (PCNA) by ubiquitin or SUMO plays an important role in coordinating the processes of DNA replication and DNA damage tolerance. Previously it was shown that the loss of RAD6-dependent error-free postreplication repair (PRR) results in DNA damage checkpoint-mediated G2 arrest in cells exposed to chronic low-dose UV radiation (CLUV), whereas wild-type and nucleotide excision repair-deficient cells are largely unaffected. In this study, we report that suppression of homologous recombination (HR) in PRR-deficient cells by Srs2 and PCNA sumoylation is required for checkpoint activation and checkpoint maintenance during CLUV irradiation. Cyclin-dependent kinase (CDK1)-dependent phosphorylation of Srs2 did not influence checkpoint-mediated G2 arrest or maintenance in PRR-deficient cells but was critical for HR-dependent checkpoint recovery following release from CLUV exposure. These results indicate that Srs2 plays an important role in checkpoint-mediated reversible G2 arrest in PRR-deficient cells via two separate HR-dependent mechanisms. The first (required to suppress HR during PRR) is regulated by PCNA sumoylation, whereas the second (required for HR-dependent recovery following CLUV exposure) is regulated by CDK1-dependent phosphorylation.

scholarly journals Targeting Homologous Recombination in Lymphoid Malignancies: Evaluation of Four Small Molecule Inhibitors of RAD51

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2080-2080
Author(s):  
Melinda Day ◽  
Tyler Maclay ◽  
Amber Cyr ◽  
Muneer G Hasham ◽  
Kin-hoe Chow ◽  
...  
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Cell Line ◽  
Genomic Instability ◽  
Small Molecule ◽  
Small Molecule Inhibitors ◽  
Burkitt’S Lymphoma ◽  
Lymphoid Malignancies ◽  
Anti Tumor Activity

Genomic instability is recognized as a driver of tumorigenesis and cancer progression. Loss of tumor suppressors or activation of oncogenes can induce DNA damage stress, promoting genomic instability and creating dependencies upon key DNA repair pathways. These dependencies can be targeted therapeutically to induce synthetic lethality. The homologous recombination (HR) repair pathway is an attractive target. HR deficient cancers are hypersensitive to numerous anticancer drugs, and tumors will often induce expression of HR genes to promote drug resistance. RAD51 is a key component of the HR pathway. RAD51 forms nucleoprotein filaments at sites of DNA damage and replication fork stalls, mediating homologous DNA strand exchange to promote recombinational repair of breaks and damaged replication forks. We utilized four small molecule inhibitors of RAD51-mediated HR for evaluation of RAD51 as a potential therapeutic target. Compounds CYT-0851, CYT-0853, CYT-1027, and CYT-1127 were evaluated for anti-cancer activity in vitro and in vivo. To determine the impact of the small molecules on RAD51 and HR, all four were tested for effects on RAD51 focus formation and sister chromatid exchange (SCE) activity. All the compounds showed a reduction in SCE activity, however only CYT-0851 and CYT-0853 produced a measurable reduction in RAD51 foci. We have previously shown that that RAD51 inhibition leads to accumulation of DNA breaks, and ultimately cell death, in cells expressing the DNA mutator protein Activation Induced Cytidine deaminase (AICDA/AID). Cytotoxicity assays were performed in an AID+ (Daudi, Burkitt's Lymphoma) and AID- (WI-38, fibroblast) cell lines. All four compounds were preferentially active in AID+ cells with little to no cytotoxicity observed in the AID-negative WI-38 cell line. CYT-0853 was the most potent in the Daudi cell line with an EC50 of 8nM. All four compounds were orally bioavailable in all preclinical species tested but showed differences in pharmacokinetics. Preclinical cell line derived xenograft models of AID-high Burkitt's lymphoma (Daudi) and B-cell acute lymphoblastic leukemia (CCRF-SB) were used to determine the in vivo anti-tumor activity of the compounds in lymphoid cancer models. CYT-0851 and CYT-0853 both showed significant anti-tumor activity with tumor growth inhibition of greater than 50% in both models. Further analysis showed drug exposure with CYT-0851 was more consistent in the CDX models than CYT-0853. Overall, these data indicate that RAD51 and HR are attractive therapeutic targets for the treatment of lymphoid malignancies and that CYT-0851 is a viable clinical development candidate. Disclosures Day: Cyteir Therapeutics: Employment. Maclay:Cyteir Therapeutics: Employment. Cyr:Cyteir Therapeutics: Employment. Mills:Cyteir Therapeutics: Employment, Equity Ownership.

scholarly journals Intrahepatic Cholangiocarcinoma: Evolving Concepts and Medical Treatment

2021 ◽  
Vol 26 (1) ◽  
pp. 33-42
Author(s):  
Hong Ja Kim
Keyword(s):  
Biliary Tract ◽  
Intrahepatic Cholangiocarcinoma ◽  
Biliary Tract Cancer ◽  
Chemotherapeutic Agents ◽  
Growth Patterns ◽  
Classification Systems ◽  
Anatomical Location ◽  
Extrahepatic Cholangiocarcinoma ◽  
Distal Cholangiocarcinoma ◽  
Tract Cancer

Cholangiocarcinoma (bile duct cancer) is classified into intrahepatic and extrahepatic cholangiocarcinoma (perihilar and distal cholangiocarcinoma) according to the anatomical location of the lesion. The incidence of extrahepatic cholangiocarcinoma has been relatively stagnant in recent decades, but intrahepatic cholangiocarcinoma is steadily increasing worldwide, requiring attention. Various classification systems based on gross growth patterns, histological findings, and tumor-derived cells, as well as classification based on existing anatomical location, have been proposed, however, the consensus has not been established yet. Intrahepatic cholangiocarcinoma is a carcinoma with an extremely poor prognosis. Complete tumor resection is the only curative treatment. The overall survival rate for 5 years after surgery is 15% to 40%, but recurrence after surgery is observed in 2/3 patients. Therefore, determining the right stage before surgery and selecting an appropriate treatment method through a multidisciplinary approach is a very important process in determining proper treatment. Systemic therapy may be used for locally advanced biliary tract cancer or metastatic biliary tract cancer where surgery is not possible. However, the effectiveness of traditional anticancer chemotherapeutic agents is rather pessimistic, therefore treatments using molecular biological properties have recently been attempted. Finding a way to increase the number of resectable cases through early diagnosis is one of the main challenges. In addition, it is also hoped that the selection of new therapeutic targets and therapeutics will be possible as a result of advanced research on gene expression profiles and mutations in cholangiocarcinoma.

scholarly journals Dysregulation of Splicing Patterns in MDS Induced By the S100A9/Fto Axis

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4215-4215
Author(s):  
Erika Adriana Eksioglu ◽  
Ling Cen ◽  
Xianghong Chen ◽  
Pingyan Cheng ◽  
Kenneth Wright ◽  
...  
Keyword(s):  
Dna Damage ◽  
Rna Polymerase Ii ◽  
Genomic Instability ◽  
Excision Repair ◽  
Functional Domain ◽  
Loop Formation ◽  
Hematopoietic Stem ◽  
Nuclear Exclusion ◽  
Rna:Dna Hybrids ◽  
Splicing Patterns

We previously reported that S100A9 promotes ineffective hematopoiesis and the development of MDS in a feed forward age-dependent fashion. Nonetheless, the precise mechanism by which S100A9 may foster DNA damage in MDS remains unclear. We recently showed that S100A9 directs overexpression of the fat-mass and obesity-associated gene (FTO) encoding an m6A RNA demethylase, which leads to nuclear exclusion of SRSF2. Removal of SRSF2 from its functional domain in the nucleosome leads to stalling of RNA polymerase II and formation of the nucleic acid R-loops, comprising DNA:RNA hybrids with the associated non-template single-stranded DNA. S100A9/FTO axis activation leads to SRSF2 deregulation through suppression of its main nuclear transport protein RanBP2, thereby stalling transcription machinery with resulting accumulation of nuclear R-loops and cytosolic/extracellular RNA:DNA hybrids. Persistent R-loops induce DNA damage while also compromising DNA repair. Here we identify an S100A9/FTO-regulated pathway responsible for induction of genomic instability through the accumulation of cytoplasmic RNA:DNA hybrids and modification of the spliceosomal patterns of aged S100A9Tg mice matching MDS hematopoietic stem and progenitor cells (HSPC). We first investigated which components of the S100A9/FTO axis are critical to hematopoiesis and those that are important for both the development of RNA:DNA hybrids and γH2AX activation. We analyzed the contribution of RanBP2 and the effects of elimination of R-loop formation via overexpression of RNAse H1, an enzyme that removes stalled R-loops in the nucleus by degrading DNA-hybridized RNA, thereby reducing the accumulation of cytoplasmic RNA:DNA hybrids. CRISPR knock-down of RanBP2 showed that the protein is critical for accumulation of yH2AX defined by double stranded breaks (DSB). Importantly, overexpression of RNAse H1 degraded R-loops and restored colony-forming capacity, indicating that RNA:DNA hybrids induced by the S100A9/FTO have profound effects on hematopoietic potential. However, while the FTO exclusion of SRSF2 from the nucleus explains the accumulation of γH2AX, it should potentially impact global RNA splicing. To investigate this, we performed a comparative RNAseq analysis on WT and S100A9Tg mice (young and old) to understand both changes induced through the normal aging process as well as those compounded by S100A9. We found that genes linked to splicing, RNA development, nucleotide excision repair and genomic instability and ribosome function were downregulated in aged S100A9Tg mice. Further analysis comparing splicing patterns of S100A9Tg and WT mice with human MDS BM HSPC led to ~200 common genes that were analyzed further. These genes showed that there are splicing changes enriched in spliceosomal assembly and mRNA splice selection site genes. We also found that the enriched genes affect the nucleolus and ribosome formation matching what is seen phenotypically with MDS. Dysregulation of these pathways are highly consistent with our observations of the pathways affected by the S100A9/FTO-induced inflammaging process, validating our hypothesis of S100A9 as a common initiator of dysfunction that can give rise to MDS. Importantly, our data demonstrates the potential for spliceosomal dysfunction regardless of the presence of spliceosomal mutations in MDS. We are currently in the process of performing both DRIPseq and m6A-seq of primary human MDS specimens and S100A9Tg mice to further assess the role of the S100A9/FTO pathway in the selection of sites for RNA/DNA hybrid formation and rise of genomic dysfunction that gives rise to MDS. We conclude that S100A9/FTO-induced nuclear exclusion of SRSF2 aids in the formation of RNA:DNA-hybrids that lead to genomic instability and the disruption of normal spliceosomal patterns in both human HSPC and the S100A9Tg MDS murine model, representing a previously uncharacterized mechanism contributing to MDS pathogenesis. Our studies provide evidence that targeting this cascade offers significant potential for development of novel, biologically rational therapeutics for MDS. Disclosures List: Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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