Terapie léky ze skupiny inhibitorů poiy(ADP-ribóza) polymerázy (PARP) je nejmodernějším krokem v léčbě ovariálního karcinomu. Až u poloviny karcinomů vaječníků lze nalézt defekt homologní rekombinace, jednoho ze způsobů opravy DNA. Proto se tento nádor stal modelem pro vývoj látek, které terapeuticky zasahují na úrovni reparace DNA. Buňky s poruchou homologní rekombinace musí využívat jiné cesty opravy DNA. Tyto cesty se tak stávají terapeutickým cílem. Proteiny rodiny PARP, především PARP1, hrají významnou roli v opravě jednovláknových zlomů DNA mechanismem nahrazování jednotlivých bází (base excision repair). Inhibice PARP vede ke kumulaci jednovláknových zlomů DNA, a následně, v důsledku kolapsu replikační vidlice, i k nahromadění dvouvláknových zlomů DNA. Tyto zlomy jsou ale opravovány jiným reparačním mechanismem - právě homologní rekombinací. Vyřazení dalšího z mechanismů opravy DNA inhibicí proteinu PARP olaparibem vede ke zvýšení citlivosti nádorových buněk k chemoterapii, nebo přímo k tzv. syntetické letaLitě. Tato léčba byla donedávna vyhrazena pacientkám s prokázanou germinální nebo somatickou mutací genů BRCA1 a BRCA2. Data o účinnosti PARP inhibitoru niraparibu však dovolila standardní použití u všech pacientek s pokročilým ovariálním karcinomem bez ohledu na mutační status. Prezentovaná kazuistika předkládá popis průběhu onemocnění u pacientky bez prokázané germinální nebo somatické mutace genů BRCA1 nebo BRCA2 s pokročilým high-grade serózním karcinomem ovaria, jíž byl po primární adjuvantní léčbě chemoterapií podáván perorální PARP inhibitor - niraparib - v udržovací léčbě. Přes vyšší toxicitu v úvodu léčby bylo, i za použití techniky deeskalace a reeskalace dávky, dosaženo dlouhodobého přežití bez známek onemocnění se zachováním vynikající kvality života.
Therapy with drugs from the group of poiy(ADP-ribose) polymerase (PARP) inhibitors is the latest step in the treatment of ovarian cancer. Defects in homologous recombination, one of the DNA repair pathways, can be found in up to half of ovarian cancers. Therefore, this tumor has become a model for the development of agents that therapeutically intervene at the level of DNA repair. Cells with defects in homologous recombination must use other DNA repair pathways. These pathways thus become therapeutic targets. PARP family proteins, particularly PARP1, play an important role in the repair of single-stranded DNA breaks by base excision repair. Inhibition of PARP leads to the accumulation of single-stranded DNA breaks and subsequently, due to replication fork collapse, to the accumulation of double-stranded DNA breaks. However, these breaks are repaired by another repair mechanism - homologous recombination. Knocking out another DNA repair mechanism by inhibiting the PARP protein with olaparib leads to i ncreased sensitivity of cancer cells to chemotherapy or directly to so-called synthetic lethality. Until recently, this treatment was reserved for patients with proven germline or somatic mutations in the BRCA1 and BRCA2 genes. However, data on the efficacy of the PARP inhibitor niraparib allowed standard use in all patients with advanced ovarian cancer regardless of mutational status. The present case report describes the course of disease in a patient without a proven germline or somatic mutation of the BRCA1 or BRCA2 genes with advanced high-grade serous ovarian cancer who was treated with the oral PARP inhibitor niraparib as maintenance therapy after primary adjuvant chemotherapy. Despite higher toxicity in the initial treatment, long-term disease-free survival with preservation of an excellent quality of life was achieved, even using dose de-escalation and re-escalation techniques.
- Keywords
- niraparib,
- MeSH
- Homologous Recombination drug effects MeSH
- Quality of Life MeSH
- Middle Aged MeSH
- Humans MeSH
- Ovarian Neoplasms * drug therapy genetics mortality MeSH
- Poly(ADP-ribose) Polymerase Inhibitors pharmacology therapeutic use MeSH
- Disease-Free Survival MeSH
- Recurrence MeSH
- Maintenance Chemotherapy * MeSH
- Check Tag
- Middle Aged MeSH
- Humans MeSH
- Female MeSH
- Publication type
- Case Reports MeSH
Venetoclax (VEN), a B-cell lymphoma 2 (BCL2) inhibitor, has a promising single-agent activity in mantle cell lymphoma (MCL), acute lymphoblastic leukemia (ALL), and large BCLs, but remissions were generally short, which call for rational drug combinations. Using a panel of 21 lymphoma and leukemia cell lines and 28 primary samples, we demonstrated strong synergy between VEN and A1155463, a BCL-XL inhibitor. Immunoprecipitation experiments and studies on clones with knockout of expression or transgenic expression of BCL-XL confirmed its key role in mediating inherent and acquired VEN resistance. Of note, the VEN and A1155463 combination was synthetically lethal even in the cell lines with lack of expression of the proapoptotic BCL2L11/BIM and in the derived clones with genetic knockout of BCL2L11/BIM. This is clinically important because BCL2L11/BIM deletion, downregulation, or sequestration results in VEN resistance. Immunoprecipitation experiments further suggested that the proapoptotic effector BAX belongs to principal mediators of the VEN and A1155463 mode of action in the BIM-deficient cells. Lastly, the efficacy of the new proapoptotic combination was confirmed in vivo on a panel of 9 patient-derived lymphoma xenografts models including MCL (n = 3), B-ALL (n = 2), T-ALL (n = 1), and diffuse large BCL (n = 3). Because continuous inhibition of BCL-XL causes thrombocytopenia, we proposed and tested an interrupted 4 days on/3 days off treatment regimen, which retained the desired antitumor synergy with manageable platelet toxicity. The proposed VEN and A1155463 combination represents an innovative chemotherapy-free regimen with significant preclinical activity across diverse BCL2+ hematologic malignancies irrespective of the BCL2L11/BIM status.
- MeSH
- Apoptosis drug effects MeSH
- Benzothiazoles MeSH
- Bridged Bicyclo Compounds, Heterocyclic * pharmacology therapeutic use MeSH
- Drug Resistance, Neoplasm * MeSH
- Isoquinolines MeSH
- Humans MeSH
- Mice MeSH
- Cell Line, Tumor MeSH
- bcl-X Protein * metabolism antagonists & inhibitors MeSH
- Bcl-2-Like Protein 11 * metabolism genetics MeSH
- Antineoplastic Agents pharmacology therapeutic use MeSH
- Proto-Oncogene Proteins c-bcl-2 metabolism antagonists & inhibitors MeSH
- Sulfonamides * pharmacology therapeutic use MeSH
- Drug Synergism MeSH
- Xenograft Model Antitumor Assays MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Mice MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
BACKGROUND: Mantle cell lymphoma (MCL) is a chronically relapsing malignancy with deregulated cell cycle progression. We analyzed efficacy, mode of action, and predictive markers of susceptibility to palbociclib, an approved CDK 4/6 inhibitor, and its combination with venetoclax, a BCL2 inhibitor. METHODS: A panel of nine MCL cell lines were used for in vitro experiments. Four patient derived xenografts (PDX) obtained from patients with chemotherapy and ibrutinib-refractory MCL were used for in vivo proof-of-concept studies. Changes of the mitochondrial membrane potential, energy-metabolic pathways, AKT activity, and pro-apoptotic priming of MCL cells were evaluated by JC-1 staining, Seahorse XF analyser, genetically encoded fluorescent AKT reporter, and BH3 profiling, respectively. MCL clones with gene knockout or transgenic (over)expression of CDKN2A, MYC, CDK4, and RB1 were used to estimate impact of these aberrations on sensitivity to palbociclib, and venetoclax. RESULTS: Co-targeting MCL cells with palbociclib and venetoclax induced cytotoxic synergy in vitro and in vivo. Molecular mechanisms responsible for the observed synthetic lethality comprised palbociclib-mediated downregulation of anti-apoptotic MCL1, increased levels of proapoptotic BIM bound on both BCL2, and BCL-XL and increased pro-apoptotic priming of MCL cells mediated by BCL2-independent mechanisms, predominantly palbociclib-triggered metabolic and mitochondrial stress. Loss of RB1 resulted in palbociclib resistance, while deletion of CDKN2A or overexpression of CDK4, and MYC genes did not change sensitivity to palbociclib. CONCLUSIONS: Our data strongly support investigation of the chemotherapy-free palbociclib and venetoclax combination as an innovative treatment strategy for post-ibrutinib MCL patients without RB1 deletion.
Targeting poly(ADP-ribose) glycohydrolase (PARG) is currently explored as a therapeutic approach to treat various cancer types, but we have a poor understanding of the specific genetic vulnerabilities that would make cancer cells susceptible to such a tailored therapy. Moreover, the identification of such vulnerabilities is of interest for targeting BRCA2;p53-deficient tumors that have acquired resistance to poly(ADP-ribose) polymerase inhibitors (PARPi) through loss of PARG expression. Here, by performing whole-genome CRISPR/Cas9 drop-out screens, we identify various genes involved in DNA repair to be essential for the survival of PARG;BRCA2;p53-deficient cells. In particular, our findings reveal EXO1 and FEN1 as major synthetic lethal interactors of PARG loss. We provide evidence for compromised replication fork progression, DNA single-strand break repair, and Okazaki fragment processing in PARG;BRCA2;p53-deficient cells, alterations that exacerbate the effects of EXO1/FEN1 inhibition and become lethal in this context. Since this sensitivity is dependent on BRCA2 defects, we propose to target EXO1/FEN1 in PARPi-resistant tumors that have lost PARG activity. Moreover, EXO1/FEN1 targeting may be a useful strategy for enhancing the effect of PARG inhibitors in homologous recombination-deficient tumors.
- MeSH
- Flap Endonucleases genetics metabolism therapeutic use MeSH
- DNA Repair Enzymes genetics MeSH
- Exodeoxyribonucleases genetics MeSH
- Glycoside Hydrolases genetics metabolism MeSH
- Humans MeSH
- Tumor Suppressor Protein p53 * genetics metabolism MeSH
- Neoplasms * drug therapy genetics MeSH
- DNA Repair MeSH
- Poly(ADP-ribose) Polymerase Inhibitors pharmacology MeSH
- DNA Damage MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Genetic screens have been used extensively to probe interactions between nuclear genes and their impact on phenotypes. Probing interactions between mitochondrial genes and their phenotypic outcome, however, has not been possible due to a lack of tools to map the responsible polymorphisms. Here, using a toolkit we previously established in Drosophila, we isolate over 300 recombinant mitochondrial genomes and map a naturally occurring polymorphism at the cytochrome c oxidase III residue 109 (CoIII109) that fully rescues the lethality and other defects associated with a point mutation in cytochrome c oxidase I (CoIT300I). Through lipidomics profiling, biochemical assays and phenotypic analyses, we show that the CoIII109 polymorphism modulates cardiolipin binding to prevent complex IV instability caused by the CoIT300I mutation. This study demonstrates the feasibility of genetic interaction screens in animal mitochondrial DNA. It unwraps the complex intra-genomic interplays underlying disorders linked to mitochondrial DNA and how they influence disease expression.
- MeSH
- Drosophila genetics MeSH
- Cardiolipins * genetics metabolism MeSH
- DNA, Mitochondrial * genetics metabolism MeSH
- Mitochondria genetics metabolism MeSH
- Electron Transport Complex IV metabolism MeSH
- Synthetic Lethal Mutations MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
Mitochondria are central for cancer responses to therapy-induced stress signals. Refractory tumors often show attenuated sensitivity to apoptotic signaling, yet clinically relevant molecular actors to target mitochondria-mediated resistance remain elusive. Here, we show that MYC-driven neuroblastoma cells rely on intact mitochondrial ribosome (mitoribosome) processivity and undergo cell death following pharmacological inhibition of mitochondrial translation, regardless of their multidrug/mitochondrial resistance and stem-like phenotypes. Mechanistically, inhibiting mitoribosomes induced the mitochondrial stress-activated integrated stress response (ISR), leading to downregulation of c-MYC/N-MYC proteins prior to neuroblastoma cell death, which could be both rescued by the ISR inhibitor ISRIB. The ISR blocks global protein synthesis and shifted the c-MYC/N-MYC turnover toward proteasomal degradation. Comparing models of various neuroectodermal tumors and normal fibroblasts revealed overexpression of MYC proteins phosphorylated at the degradation-promoting site T58 as a factor that predetermines vulnerability of MYC-driven neuroblastoma to mitoribosome inhibition. Reducing N-MYC levels in a neuroblastoma model with tunable MYCN expression mitigated cell death induction upon inhibition of mitochondrial translation and functionally validated the propensity of neuroblastoma cells for MYC-dependent cell death in response to the mitochondrial ISR. Notably, neuroblastoma cells failed to develop significant resistance to the mitoribosomal inhibitor doxycycline over a long-term repeated (pulsed) selection. Collectively, we identify mitochondrial translation machinery as a novel synthetic lethality target for multidrug-resistant MYC-driven tumors.
- MeSH
- Apoptosis MeSH
- Humans MeSH
- Cell Line, Tumor MeSH
- Neuroblastoma * drug therapy genetics metabolism MeSH
- N-Myc Proto-Oncogene Protein genetics metabolism MeSH
- Proto-Oncogene Proteins c-myc genetics metabolism MeSH
- Signal Transduction MeSH
- Synthetic Lethal Mutations * MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
INTRODUCTION: Hepatocellular carcinoma (HCC) patients at advanced stages receive immunotherapy or treatment with tyrosine kinase inhibitors (TKIs) such as Sorafenib (Sora) or Lenvatinib in frontline as well as Regorafenib (Rego) or Cabozantinib in second-line. A major hindrance of TKI therapies is the development of resistance, which renders drug treatment futile and results in HCC progression. METHODS: In this study, we addressed the impact of the receptor tyrosine kinase Axl binding to its ligand Gas6 in acquiring refractoriness to TKIs. The initial responses of Axl-positive and Axl-negative cell lines to different TKIs were assessed. Upon inducing resistance, RNA-Seq, gain- and loss-of-function studies were applied to understand and intervene with the molecular basis of refractoriness. Secretome analysis was performed to identify potential biomarkers of resistance. RESULTS: We show that HCC cells exhibiting a mesenchymal-like phenotype were less sensitive to drug treatment, linking TKI resistance to changes in epithelial plasticity. Gas6/Axl expression and activation were upregulated in Rego-resistant HCC cells together with the induction of ErbB receptors, whereas HCC cells lacking Axl failed to stimulate ErbBs. Treatment of Rego-insensitive HCC cells with the pan-ErbB family inhibitor Afatinib rather than with Erlotinib blocking ErbB1 reduced cell viability and clonogenicity. Genetic intervention with ErbB2-4 but not ErbB1 confirmed their crucial involvement in refractoriness to Rego. Furthermore, Rego-resistant HCC cells secreted basic fibroblast growth factor (bFGF) depending on Axl expression. HCC patients treated with Sora in first-line and with Rego in second-line displayed elevated serum levels of bFGF, emphasizing bFGF as a predictive biomarker of TKI treatment. DISCUSSION: Together, these data suggest that the inhibition of ErbBs is synthetic lethal with Rego in Axl-expressing HCC cells, showing a novel vulnerability of HCC.
- Publication type
- Journal Article MeSH
BACKGROUND: Multiple myeloma (MM) is an incurable plasma cell malignancy, accounting for approximately 1% of all cancers. Despite recent advances in the treatment of MM, due to the introduction of proteasome inhibitors (PIs) such as bortezomib (BTZ) and carfilzomib (CFZ), relapses and disease progression remain common. Therefore, a major challenge is the development of novel therapeutic approaches to overcome drug resistance, improve patient outcomes, and broaden PIs applicability to other pathologies. METHODS: We performed genetic and drug screens to identify new synthetic lethal partners to PIs, and validated candidates in PI-sensitive and -resistant MM cells. We also tested best synthetic lethal interactions in other B-cell malignancies, such as mantle cell, Burkitt's and diffuse large B-cell lymphomas. We evaluated the toxicity of combination treatments in normal peripheral blood mononuclear cells (PBMCs) and bone marrow stromal cells (BMSCs). We confirmed the combo treatment' synergistic effects ex vivo in primary CD138+ cells from MM patients, and in different MM xenograft models. We exploited RNA-sequencing and Reverse-Phase Protein Arrays (RPPA) to investigate the molecular mechanisms of the synergy. RESULTS: We identified lysine (K)-specific demethylase 1 (LSD1) as a top candidate whose inhibition can synergize with CFZ treatment. LSD1 silencing enhanced CFZ sensitivity in both PI-resistant and -sensitive MM cells, resulting in increased tumor cell death. Several LSD1 inhibitors (SP2509, SP2577, and CC-90011) triggered synergistic cytotoxicity in combination with different PIs in MM and other B-cell neoplasms. CFZ/SP2509 treatment exhibited a favorable cytotoxicity profile toward PBMCs and BMSCs. We confirmed the clinical potential of LSD1-proteasome inhibition in primary CD138+ cells of MM patients, and in MM xenograft models, leading to the inhibition of tumor progression. DNA damage response (DDR) and proliferation machinery were the most affected pathways by CFZ/SP2509 combo treatment, responsible for the anti-tumoral effects. CONCLUSIONS: The present study preclinically demonstrated that LSD1 inhibition could provide a valuable strategy to enhance PI sensitivity and overcome drug resistance in MM patients and that this combination might be exploited for the treatment of other B-cell malignancies, thus extending the therapeutic impact of the project.
- Publication type
- Journal Article MeSH
Functional perturbations of the cohesin complex with subsequent changes in chromatin structure and replication are reported in a multitude of cancers including acute myeloid leukemia (AML). Mutations of its STAG2 subunit may predict unfavorable risk as recognized by the 2022 European Leukemia Net recommendations, but the underlying evidence is limited by small sample sizes and conflicting observations regarding clinical outcomes, as well as scarce information on other cohesion complex subunits. We retrospectively analyzed data from a multi-center cohort of 1615 intensively treated AML patients and identified distinct co-mutational patters for mutations of STAG2, which were associated with normal karyotypes (NK) and concomitant mutations in IDH2, RUNX1, BCOR, ASXL1, and SRSF2. Mutated RAD21 was associated with NK, mutated EZH2, KRAS, CBL, and NPM1. Patients harboring mutated STAG2 were older and presented with decreased white blood cell, bone marrow and peripheral blood blast counts. Overall, neither mutated STAG2, RAD21, SMC1A nor SMC3 displayed any significant, independent effect on clinical outcomes defined as complete remission, event-free, relapse-free or overall survival. However, we found almost complete mutual exclusivity of genetic alterations of individual cohesin subunits. This mutual exclusivity may be the basis for therapeutic strategies via synthetic lethality in cohesin mutated AML.
The pro-survival MCL1 protein is overexpressed in many cancers, including B-cell non-Hodgkin lymphomas (B-NHL). S63845 is a highly specific inhibitor of MCL1. We analyzed mechanisms of sensitivity/resistance to S63845 in preclinical models of diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma. Annexin V-based cytotoxic assays, Western blot analysis, protein co-immunoprecipitation, and cell clones with manipulated expression of BCL2 family proteins were used to analyze mechanisms of sensitivity to S63845. Experimental in vivo therapy with S63845 and/or venetoclax was performed using patient-derived xenografts (PDX) of treatment-refractory B-NHL. A subset of DLBCL and majority of Burkitt lymphoma cell lines were sensitive to S63845. The level of BCL2 protein expression was the major determinant of resistance to S63845: BCL2 serves as a buffer for pro-apoptotic proteins released from MCL1 upon exposure to S63845. While BCL2-negative lymphomas were effectively eliminated by single-agent S63845, its combination with venetoclax was synthetically lethal in BCL2-positive PDX models. Concerning MCL1, both, the level of MCL1 protein expression, and its occupational status represent key factors mediating sensitivity to S63845. In contrast to MCL1-BIM/BAK1 complexes that prime lymphoma cells for S63845-mediated apoptosis, MCL1-NOXA complexes are associated with S63845 resistance. In conclusion, MCL1 represents a critical survival molecule for most Burkitt lymphomas and a subset of BCL2-negative DLBCLs. The level of BCL2 and MCL1 expression and occupational status of MCL1 belong to the key modulators of sensitivity/resistance to S63845. Co-treatment with venetoclax can overcome BCL2-mediated resistance to S63845, and enhance efficacy of MCL1 inhibitors in BCL2-positive aggressive B-NHL.
- MeSH
- Apoptosis MeSH
- Burkitt Lymphoma genetics mortality MeSH
- Lymphoma, Large B-Cell, Diffuse genetics mortality MeSH
- Humans MeSH
- Cell Line, Tumor MeSH
- Myeloid Cell Leukemia Sequence 1 Protein metabolism MeSH
- Proto-Oncogene Proteins c-bcl-2 metabolism MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
