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Genes Jun 2024Patients with advanced-stage epithelial ovarian cancer (EOC) receive treatment with a poly-ADP ribose-polymerase (PARP) inhibitor (PARPi) as maintenance therapy after...
BACKGROUND
Patients with advanced-stage epithelial ovarian cancer (EOC) receive treatment with a poly-ADP ribose-polymerase (PARP) inhibitor (PARPi) as maintenance therapy after surgery and chemotherapy. Unfortunately, many patients experience disease progression because of acquired therapy resistance. This study aims to characterize epigenetic and genomic changes in cell-free DNA (cfDNA) associated with PARPi resistance.
MATERIALS AND METHODS
Blood was taken from 31 EOC patients receiving PARPi therapy before treatment and at disease progression during/after treatment. Resistance was defined as disease progression within 6 months after starting PARPi and was seen in fifteen patients, while sixteen patients responded for 6 to 42 months. Blood cfDNA was evaluated via Modified Fast Aneuploidy Screening Test-Sequencing System (mFast-SeqS to detect aneuploidy, via Methylated DNA Sequencing (MeD-seq) to find differentially methylated regions (DMRs), and via shallow whole-genome and -exome sequencing (shWGS, exome-seq) to define tumor fractions and mutational signatures.
RESULTS
Aneuploid cfDNA was undetectable pre-treatment but observed in six patients post-treatment, in five resistant and one responding patient. Post-treatment ichorCNA analyses demonstrated in shWGS and exome-seq higher median tumor fractions in resistant (7% and 9%) than in sensitive patients (7% and 5%). SigMiner analyses detected predominantly mutational signatures linked to mismatch repair and chemotherapy. DeSeq2 analyses of MeD-seq data revealed three methylation signatures and more tumor-specific DMRs in resistant than in responding patients in both pre- and post-treatment samples (274 vs. 30 DMRs, 190 vs. 57 DMRs, Χ-test < 0.001).
CONCLUSION
Our genome-wide Next-Generation Sequencing (NGS) analyses in PARPi-resistant patients identified epigenetic differences in blood before treatment, whereas genomic alterations were more frequently observed after progression. The epigenetic differences at baseline are especially interesting for further exploration as putative predictive biomarkers for PARPi resistance.
Topics: Humans; Female; Drug Resistance, Neoplasm; Middle Aged; Ovarian Neoplasms; Poly(ADP-ribose) Polymerase Inhibitors; Epigenesis, Genetic; Aged; DNA Methylation; Carcinoma, Ovarian Epithelial; Adult; Aneuploidy; Genomics
PubMed: 38927686
DOI: 10.3390/genes15060750 -
British Journal of Cancer Jun 2024
PubMed: 38926527
DOI: 10.1038/s41416-024-02768-7 -
The Journal of Molecular Diagnostics :... Jun 2024PMS2 is one of the mismatch repair genes included in routine genetic testing for Lynch syndrome, colorectal, ovarian, and endometrial cancers. PMS2 is also included in...
PMS2 is one of the mismatch repair genes included in routine genetic testing for Lynch syndrome, colorectal, ovarian, and endometrial cancers. PMS2 is also included in the American College of Medical Genetics and Genomics (ACMG) secondary findings gene list in the context of clinical exome and genome sequencing. However, sequencing of PMS2 by short-read based next generation sequencing (NGS) technologies is complicated by the presence of the pseudogene PMS2CL and often supplemented by long-range based approaches such as long-range polymerase chain reaction (LR-PCR) or long-read based next generation sequencing, which increases the complexity and cost. Here, we described a bioinformatics homology triage workflow that can eliminate the need for long-read based testing for PMS2 for the vast majority of patients undergoing exome sequencing, thus simplifying PMS2 testing and reducing the associated cost.
PubMed: 38925456
DOI: 10.1016/j.jmoldx.2024.06.001 -
The Journal of Molecular Diagnostics :... Jun 2024Replication-coupled gene editing using locked-nucleic-acid-modified single-stranded oligodeoxyribonucleotides (LMOs) can genetically engineer mammalian cells with high...
Replication-coupled gene editing using locked-nucleic-acid-modified single-stranded oligodeoxyribonucleotides (LMOs) can genetically engineer mammalian cells with high precision at single nucleotide resolution. Based on this method, we developed oligonucleotide-directed mutation screening (ODMS) to determine whether variants of uncertain clinical significance of DNA mismatch-repair (MMR) genes can cause Lynch syndrome. In ODMS, the appearance of 6-thioguanine (6TG)-resistant colonies upon introduction of the variant is indicative for defective MMR and hence pathogenicity. Whereas previously mouse embryonic stem cells (mESCs) hemizygous for DNA mismatch-repair (MMR) genes were used, we now show that ODMS can also be applied in wild-type mESCs carrying two functional alleles of each MMR gene. 6TG resistance can result from two possible events: first, the mutation is present in only one allele, which is indicative for dominant-negative activity of the variant; second, both alleles contain the planned modification, which is indicative for a regular loss-of-function variant. Thus, ODMS in wild-type mESCs can discriminate fully disruptive and dominant-negative MMR variants. The feasibility of biallelic targeting suggested that the efficiency of LMO-mediated gene targeting at a non-selectable locus may be enriched in cells that had undergone a simultaneous selectable LMO targeting event. This turned out to be the case and provided a protocol to improve recovery of LMO-mediated gene modification events.
PubMed: 38925454
DOI: 10.1016/j.jmoldx.2024.05.011 -
The Journal of Biological Chemistry Jun 2024The human AlkB homologs, ALKBH2 and ALKBH3, respond to methylation damage to maintain genomic integrity and cellular viability. Both ALKBH2 and ALKBH3 are direct...
The human AlkB homologs, ALKBH2 and ALKBH3, respond to methylation damage to maintain genomic integrity and cellular viability. Both ALKBH2 and ALKBH3 are direct reversal repair (DRR) enzymes that remove 1meA and 3meC lesions commonly generated by alkylating chemotherapeutic agents. Thus, the existence of deficiencies in ALKBH proteins can be exploited in synergy with chemotherapy. In this study, we investigated possible interactions between ALKBH2 and ALKBH3 with other proteins that could alter damage response and discovered an interaction with the mismatch repair (MMR) system. To test whether the lack of active MMR impacts ALKBH2 and/or ALKBH3 response to methylating agents, we generated cells deficient in ALKBH2, ALKBH3, or both in addition to Mlh homolog 1 (MLH1), another MMR protein. We found that MLH1ALKBH3 cells showed enhanced resistance towards S1- and S2-type methylating agents, whereas MLH1ALKBH2 cells were only resistant to S1-type methylating agents. Concomitant loss of ALKBH2 and ALKBH3 (ALKBH23) rendered cells sensitive to S1- and S2-agents, but the additional loss of MLH1 enhanced resistance to both types of damage. We also showed that ALKBH23 cells have an ATR-dependent arrest at the G/M checkpoint, increased apoptotic signalling, and replication fork stress in response to methylation. However, these responses were not observed with the loss of functional MLH1 in MLH1ALKBH23 cells. Finally, in MLH1ALKBH23 cells, we observed elevated mutant frequency in untreated and temozolomide treated cells. These results suggest that obtaining a more accurate prognosis of chemotherapeutic outcome requires information on the functionality of ALKBH2, ALKBH3, and MLH1.
PubMed: 38925328
DOI: 10.1016/j.jbc.2024.107492 -
FEBS Letters Jun 2024Myotonic dystrophy type 2 (DM2) is a neurogenerative disease caused by caprylic/capric triglyceride (CCTG) tetranucleotide repeat expansions in intron 1 of the cellular...
Myotonic dystrophy type 2 (DM2) is a neurogenerative disease caused by caprylic/capric triglyceride (CCTG) tetranucleotide repeat expansions in intron 1 of the cellular nucleic acid-binding protein (CNBP) gene. Non-B DNA structures formed by CCTG repeats can promote genetic instability, whereas interrupting motifs of NCTG (N = A/T/G) within CCTG repeats help to maintain genomic stability. However, whether the interrupting motifs can affect DNA structures of CCTG repeats remains unclear. Here, we report that four CCTG repeats with an interrupting 3'-A/T/G residue formed dumbbell structures, whereas a non-interrupting 3'-C residue resulted in a multi-loop structure exhibiting conformational dynamics that may contribute to a higher tendency of escaping from DNA mismatch repair and causing repeat expansions. The results provide new structural insights into the genetic instability of CCTG repeats in DM2.
PubMed: 38922834
DOI: 10.1002/1873-3468.14952 -
International Journal of Gynaecology... Jun 2024To assess the stage distribution and stage-related disease-specific survival rates for endometrial cancer using the FIGO (the International Federation of Gynecology &...
Stage distribution and prognostic accuracy of the 2023 FIGO (the International Federation of Gynecology & Obstetrics) staging system for endometrial cancer: A retrospective cohort study.
OBJECTIVE
To assess the stage distribution and stage-related disease-specific survival rates for endometrial cancer using the FIGO (the International Federation of Gynecology & Obstetrics) 2009 and 2023 staging systems. Further, we sought to evaluate the prognostic utility of additional covariates beyond the FIGO 2023 stage.
METHODS
Endometrial carcinomas were molecularly classified by the Proactive Molecular Risk Classifier for Endometrial Cancer and staged according to FIGO 2009 and 2023 criteria. Disease-specific survival was calculated as the time from surgery to death from endometrial cancer.
RESULTS
Data from 604 patients were analyzed. Median follow-up time was 81 months. A total of 118 stage shifts (19.5%) occurred between the FIGO 2009 and FIGO 2023 systems, with upshifts accounting for 107 (90.7%) of these changes. Within the FIGO 2023 system, molecular classification resulted in restaging of 69 patients (11.4%). Shifts that could alter adjuvant therapy decisions were identified in 23 patients (3.8%). The FIGO 2023 system effectively categorized endometrial cancers into prognostic subgroups. The FIGO 2023 stage, tumor size, positive peritoneal cytology, and mismatch repair deficiency were associated with disease-specific survival in a multivariable analysis, whereas age and adjuvant therapy were not.
CONCLUSION
The FIGO 2023 staging system for endometrial cancer appears highly prognostic. Prognostic assessment of the patients can be further enhanced by readily accessible covariates. A stage shift between the FIGO 2009 and 2023 systems occurs in about one-fifth of patients. The implementation of molecular classification within the FIGO 2023 system bears implications for decisions regarding adjuvant therapy.
PubMed: 38922703
DOI: 10.1002/ijgo.15749 -
Gastric Cancer : Official Journal of... Jun 2024Gastric cancer (GC) is a common malignancy that presents challenges in patient care worldwide. The mismatch repair (MMR) system is a highly conserved DNA repair... (Review)
Review
Gastric cancer (GC) is a common malignancy that presents challenges in patient care worldwide. The mismatch repair (MMR) system is a highly conserved DNA repair mechanism that protects genome integrity during replication. Deficient MMR (dMMR) results in an increased accumulation of genetic errors in microsatellite sequences, leading to the development of a microsatellite instability-high (MSI-H) phenotype. Most MSI-H/dMMR GCs arise sporadically, mainly due to MutL homolog 1 (MLH1) epigenetic silencing. Unlike microsatellite-stable (MSS)/proficient MMR (pMMR) GCs, MSI-H/dMMR GCs are relatively rare and represent a distinct subtype with genomic instability, a high somatic mutational burden, favorable immunogenicity, different responses to treatment, and prognosis. dMMR/MSI-H status is a robust predictive biomarker for treatment with immune checkpoint inhibitors (ICIs) due to high neoantigen load, prominent tumor-infiltrating lymphocytes, and programmed cell death ligand 1 (PD-L1) overexpression. However, a subset of MSI-H/dMMR GC patients does not benefit from immunotherapy, highlighting the need for further research into predictive biomarkers and resistance mechanisms. This review provides a comprehensive overview of the clinical, molecular, immunogenic, and therapeutic aspects of MSI-H/dMMR GC, with a focus on the impact of ICIs in immunotherapy and their potential as neoadjuvant therapies. Understanding the complexity and diversity of the molecular and immunological profiles of MSI-H/dMMR GC will drive the development of more effective therapeutic strategies and molecular targets for future precision medicine.
PubMed: 38922524
DOI: 10.1007/s10120-024-01523-4 -
Cells Jun 2024Cancer accounted for 10 million deaths in 2020, nearly one in every six deaths annually. Despite advancements, the contemporary clinical management of human neoplasms... (Review)
Review
Cancer accounted for 10 million deaths in 2020, nearly one in every six deaths annually. Despite advancements, the contemporary clinical management of human neoplasms faces a number of challenges. Surgical removal of tumor tissues is often not possible technically, while radiation and chemotherapy pose the risk of damaging healthy cells, tissues, and organs, presenting complex clinical challenges. These require a paradigm shift in developing new therapeutic modalities moving towards a more personalized and targeted approach. The tumor-agnostic philosophy, one of these new modalities, focuses on characteristic molecular signatures of transformed cells independently of their traditional histopathological classification. These include commonly occurring DNA aberrations in cancer cells, shared metabolic features of their homeostasis or immune evasion measures of the tumor tissues. The first dedicated, FDA-approved tumor-agnostic agent's profound progression-free survival of 78% in mismatch repair-deficient colorectal cancer paved the way for the accelerated FDA approvals of novel tumor-agnostic therapeutic compounds. Here, we review the historical background, current status, and future perspectives of this new era of clinical oncology.
Topics: Humans; Neoplasms; Precision Medicine
PubMed: 38920700
DOI: 10.3390/cells13121071 -
The Oncologist Jun 2024Colorectal cancer (CRC) is a major cause of cancer-related deaths globally. While treatment advancements have improved survival rates, primarily through targeted...
Colorectal cancer (CRC) is a major cause of cancer-related deaths globally. While treatment advancements have improved survival rates, primarily through targeted therapies based on KRAS, NRAS, and BRAF mutations, personalized treatment strategies for CRC remain limited. Immunotherapy, mainly immune checkpoint blockade, has shown efficacy in various cancers but is effective in only a small subset of patients with CRC with deficient mismatch repair (dMMR) proteins or high microsatellite instability (MSI). Recent research has challenged the notion that CRC is immunologically inert, revealing subsets with high immunogenicity and diverse lymphocytic infiltration. Identifying precise biomarkers beyond dMMR and MSI is crucial to expanding immunotherapy benefits. Hence, exploration has extended to various biomarker sources, such as the tumor microenvironment, genomic markers, and gut microbiota. Recent studies have introduced a novel classification system, consensus molecular subtypes, that aids in identifying patients with CRC with an immunogenic profile. These findings underscore the necessity of moving beyond single biomarkers and toward a comprehensive understanding of the immunological landscape in CRC, facilitating the development of more effective, personalized therapies.
PubMed: 38920285
DOI: 10.1093/oncolo/oyae152