Mitotic Catastrophe Research Articles

A Novel Dialkylamino-Functionalized Chalcone, DML6, Inhibits Cervical Cancer Cell Proliferation, In Vitro, via Induction of Oxidative Stress, Intrinsic Apoptosis and Mitotic Catastrophe.

In this study, we designed, synthesized and evaluated, in vitro, novel chalcone analogs containing dialkylamino pharmacophores in the cervical cancer cell line, OV2008. The compound, DML6 was selective and significantly decreased the proliferation of OV2008 and HeLa cells in sub-micromolar concentrations, compared to prostate, lung, colon, breast or human embryonic kidney cell line (HEK293). DML6, at 5 μM, arrested the OV2008 cells in the G2 phase. Furthermore, DML6, at 5 μM, increased the levels of reactive oxygen species and induced a collapse in the mitochondrial membrane potential, compared to OV2008 cells incubated with a vehicle. DML6, at 5 μM, induced intrinsic apoptosis by significantly (1) increasing the levels of the pro-apoptotic proteins, Bak and Bax, and (2) decreasing the levels of l the anti-apoptotic protein, Bcl-2, compared to cell incubated with a vehicle. Furthermore, DML6, at 5 and 20 μM, induced the cleavage of caspase-9, followed by subsequent cleavage of the executioner caspases, caspase-3 and caspase-7, which produced OV2008 cell death. Overall, our data suggest that DML6 is an apoptosis-inducing compound that should undergo further evaluation as a potential treatment for cervical cancer.

Discovery and Characterization of a Novel MASTL Inhibitor MKI-2 Targeting MASTL-PP2A in Breast Cancer Cells and Oocytes.

Although microtubule-associated serine/threonine kinase-like (MASTL) is a promising target for selective anticancer treatment, MASTL inhibitors with nano range potency and antitumor efficacy have not been reported. Here, we report a novel potent and selective MASTL inhibitor MASTL kinase inhibitor-2 (MKI-2) identified in silico through a drug discovery program. Our data showed that MKI-2 inhibited recombinant MASTL activity and cellular MASTL activity with IC50 values of 37.44 nM and 142.7 nM, respectively, in breast cancer cells. In addition, MKI-2 inhibited MASTL kinase rather than other AGC kinases, such as ROCK1, AKT1, PKACα, and p70S6K. Furthermore, MKI-2 exerted various antitumor activities by inducing mitotic catastrophe resulting from the modulation of the MASTL-PP2A axis in breast cancer cells. The MKI-2 treatment showed phenocopies with MASTL-null oocyte in mouse oocytes, which were used as a model to validate MKI-2 activity. Therefore, our study provided a new potent and selective MASTL inhibitor MKI-2 targeting the oncogenic MAST-PP2A axis in breast cancer cells.

Abstract 980: Preclinical evaluation of mps1 inhibition in uterine leiomyosarcoma

Abstract Background: Uterine leiomyosarcoma (Ut-LMS) is the commonest malignant mesenchymal tumor arising from the uterus. It is aggressive and the prognosis is dismal. To-date, no specific oncogenic drivers have been identified. Conventional adjuvant therapy and immunotherapy are ineffective and treatment largely remains surgical. MPS1 kinase is vital in spindle assembly checkpoint which safeguards the faithful segregation of chromosomes. Its inactivation leads to mitotic defects and induces mitotic catastrophe. Compare with normal tissue, MPS1 has shown to be overexpressed in Ut-LMS. Method: The Ut-LMS cell lines SK-UT-1 and SKN were treated with a MPS1 inhibitor. RT-qPCR was performed to analyze mRNA expression levels of Spindle Assembly Checkpoint-related genes. Cells were seeded in 96-well plates and treated with MPS1 inhibitor for 4 days. Sulforhodamine B stain was used to labelled viable cells. IC50 of different cell lines was determined by SRB assay. Cell cycle analysis was done after 2 days treatment by propidium iodide staining. Apoptosis study was done after 3 days treatment by AnnexinV/PI apoptotic assay. Flow cytometry was used to analyze PI assay and AnnexinV/PI apoptotic assay. Immunofluorescence staining of centromere, α-tubulin and DAPI was used to label kinetochore, mitotic spindles and DNA. Cells with chromosome missegregation were counted in treated and non-treated samples. Ut-LMS cell lines SKN was injected subcutaneously in Balb/c nude mice and MPS1 inhibitor was administrated through oral gavage daily, tumor weight was record and tumor size was estimated by caliper. Results: The Spindle Assembly Checkpoint-related genes MPS1, CDC20, MAD2L1, BUB1, BUB1B, and KNL1 were found to be overexpressed. SRB assays had shown that there was growth inhibition of both cell lines in a concentration-dependent manner with IC50 values ranged between 40-65 nM. An increase in aneuploidy cells was demonstrated by PI assay, which suggested that MPS1 inhibitor disrupted cell cycle and induced aneuploidy. The inhibitor also induced apoptosis as demonstrated an increase in AnnexinV+/PI+ cells. Chromosome missegregation was demonstrated in double-thymidine block synchronized anaphase cells with immunofluorescence staining. Micronuclei were also identified in tetraploid cells. In a preliminary in vivo study, MPS1 inhibitor was shown to reduce tumor growth in xenograft models. Conclusion: Our preclinical results indicated that MPS1 inhibitor was an effective treatment in Ut-LMS as a single agent by causing chromosome missegregation, mitotic catastrophe, genomic instability and cell death. Further evaluation of its use in combination with other pharmacological agents is in progress. Citation Format: Ho Shing Wong, Hok Yeung H. Lee, Ka Yu Tse, Tak Wah Mak, Philip PC Ip. Preclinical evaluation of mps1 inhibition in uterine leiomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 980.

Abstract LB119: VRN08, a Selective Mps1 Kinase Inhibitor Induces Mitotic Catastrophe and Apoptosis Efficiently in Advanced Cancers Including Rb1-Deficient

Abstract Spindle assembly checkpoint (SAC) prevents mis-segregation of chromosome and allows accurate division in mitosis. Mps1 (also known as TTK) is one of the essential kinases for recruitment of SAC proteins after chromosome segregation. Failure of SAC induces chromosome instability, mitotic catastrophe, and ultimately apoptotic cell death and Mps1 is induced or activated in rapidly dividing tumor cells. Therefore, Mps1 has been considered an attractive anti-cancer drug target. VRN081569 is a potent type I kinase inhibitor of Mps1, which stabilizes Mps1 kinase domain in a closed conformation by forming a tight interface with its kinase domain. This structural stabilization appears to increase cellular potency for the induction of aneuploidy and apoptosis (~ 10 nM or less GI50 value). The loss of retinoblastoma tumor suppressor gene (Rb1), which is prevalent in advanced cancers, dysregulates cell cycle and promotes cell division. In particular, the resistance to CDK4/6 inhibitors has been reportedly mediated by loss of the Rb1 gene. We found that Rb1-negative cells express higher level of Mps1 than Rb1-positive cells and VRN081569 efficiently induce apoptosis of Rb1-negative Triple Negative Breast Cancer (TNBC) cell line MDA-MB-468 than Rb1-positive TNBC MDA-MB-231. Especially we confirmed that VRN081569 induces caspase 3/7 activity faster in Rb1-negative cells (~50-fold EC50 of caspase 3/7 activity compared to Rb1-positive cells), and cell cycle analysis has shown that our compound induces a dose-dependent dysregulation of mitosis, resulting in a decrease in the frequency of the G0/G1 phase, and also induces aneuploidy and apoptosis. Finally, we confirmed a combination effects with anti-microtubule agents BCL-2 inhibitor and PARP-1 inhibitor, suggesting that modulation of two different cellular processes may overcome the lack of single agent activity for TNBC. Citation Format: Hong Ryul Jung, Yeonsil Kim, Haelee Kim, Ji-Hye Kwon, Dong-hyuk Seo, Jung Beom Son, Nam Doo Kim, Daekwon Kim, Sunghwan Kim. VRN08, a Selective Mps1 Kinase Inhibitor Induces Mitotic Catastrophe and Apoptosis Efficiently in Advanced Cancers Including Rb1-Deficient [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB119.

Abstract 2473: NR4A1 suppresses cancer replication stress through R-loop-dependent inhibition of immediate early gene transcriptional elongation

Abstract Deregulation of oncogenic proliferative signals triggers replication stress in cancer cells to which they must adapt. Immediate early genes (IEGs), identified by their rapid stress-induced transient bursts of expression, are critical to integrating downstream signaling pathways. In studying tumor initiation by patient-derived breast cancer cells, we observed acquisition of open chromatin domains at the genebody and 3'-UTR of IEGs, uniquely across the genome. Through in vivo and in vitro modeling, we show that the IEG and orphan nuclear receptor NR4A1 localizes across multiple IEG genebodies, where it binds to RNA Pol II, arresting transcriptional elongation and generating extensive R-loops and accessible chromatin. Acute stress promptly removes NR4A1 from IEG genebodies, triggering immediate release of their poised transcripts. In breast cancer cells, NR4A1 overexpression increases tumorigenesis; conversely, its deletion leads to uncompensated replication stress, chromosomal instability and mitotic catastrophe, driven by deregulation of its IEG target FOS. A large fraction of primary breast and other cancers exhibit open genebody chromatin at IEGs, consistent with preserved NR4A1 function. Thus, NR4A1 mediates a novel transcriptional elongation checkpoint, unique to stress-induced genes and required for their rapid bursts of expression. Cancers that have retained this mechanism in adapting to chronic replication stress may be dependent on NR4A1 for proliferation. Citation Format: Hongshan Guo, Gabriel Golczer, Shyamala Maheswaran, Michael S. Lawrence, Daniel A. Haber. NR4A1 suppresses cancer replication stress through R-loop-dependent inhibition of immediate early gene transcriptional elongation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2473.

Abstract 2051: Inhibiting CDC7 kinase for the treatment of Ewing sarcoma

Abstract Ewing Sarcoma is a malignant tumor of the bone and soft tissue that is primarily driven by the fusion protein EWS-FLI1. With no current targeted therapy, treatment options remain limited and toxic. Recent reports have shown that Ewing tumors harbor large amounts of transcription-associated replication stress and that this offers an attractive therapeutic intervention point. Our group has shown that inhibition of the kinase complex DDK (CDC7-DBF4) results in apoptosis and a significant reduction in cell viability in EWS-FLI1-harboring Ewing's sarcoma cell lines. Also, low dose DDK inhibition in Ewing's sarcoma cells caused an S/G2 cell cycle accumulation at 24 hours, followed by re-entry into G1 and appearance of sub-G1 DNA. This suggests a failure to properly progress through S-phase followed by premature mitotic entry and mitotic catastrophe resulting in cell death. To this end, there was a significant increase in the formation of micronuclei and other aberrant mitotic structures upon DDK inhibition in Ewing's cells. Interestingly, there was minimal signs of mitotic accumulation, despite clear evidence of mitotic stress, indicating a failure to properly enforce a G2-M checkpoint. Importantly, these phenotypes were not mimicked with the use of the CDK2 inhibitor Roscotivine, suggesting an origin firing-independent basis for the sensitivity to DDK inhibition. Furthermore, we show that DDK inhibition synergizes with the TOP1 inhibitor Camptothecin and with the PARP1 inhibitor Talazoparib to kill Ewing Sarcoma cells in vitro. We have hypothesized this to be due to DDK's potential role in replication fork instability/restart. Together, these results suggest that Ewing sarcoma cells rely on the activity of DDK to maintain cell viability independently from its role in the regulation of replication origin initiation and suggest that DDK inhibition may prove to be a viable treatment option for patients with Ewing's sarcoma. Citation Format: Jeffrey C. Martin. Inhibiting CDC7 kinase for the treatment of Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2051.

A Novel Phthalimide-Derivative, TC11, Induced G2/M Arrest and Apoptosis of High-Risk Myeloma Cells By Interacting with Nucleophosmin1 and α-Tubulin, but Not By Binding to Celeblon

Background and Purpose:Emergence of novel drugs including immunomodulatory drugs (IMiDs) such as thalidomide, lenalidomide and pomalidomide have markedly improved the survival of multiple myeloma (MM) patients. However, IMiDs have substantial limitation in the treatment of MM; little effect on MM patients with high-risk cytogenetic changes and their teratogenicity. Recently it was reported that IMiDs showed anti-tumor activity as well as teratogenicity by directly binding to cereblon (CRBN).We have previously reported that a novel phthalimide-derivative, 2-(2,6-diisopropylphenyl)-5-amino-1H-isoindole-1,3-dione (TC11), induced apoptosis of high-risk MM cells in vivo and also showed anti-osteoclastogenic activity. At the same time, we observed abnormal α-tubulin fragmentation in TC11-treated MM cell (Matsushita et. al. PLoS One 2015). We have also demonstrated that TC11 bound to nucleophosmin 1(NPM1) and α-tubulin using in vitro virus (IVV) method (Shiheido et. al. PLoS One 2012). Interestingly, lenalidomide also bound to NPM1. The purpose of this study is to clarify molecular mechanisms of anti-myeloma effects of TC11.Results and Discussion:(1) Effect of TC11 is CRBN-independent:Recently it was reported that lenalidomide bound to CRBN, resulting in degradation of its substrates, IKZF1/3 and CK1α. In this study, we found that lenalidomide caused degradation of IKZF1/3 and CK1α in the high-risk MM cell line, KMS34. However, TC11 didn't down-regulate CRBN or its substrates, IKZF1/3 and CK1α. Taken together with the result of Biacore assay, TC11 induced MM cell death via CRBN-independent pathway.(2) Cell cycle arrest by TC11 vs. lenalidomide:Then we tried to elucidate molecular mechanisms of TC11 by the microarray analysis of KMS21, which is highly sensitive to TC11 and lenalidomide. Microarray Gene Set Enrichment Analysis (GSEA) indicated that TC11 upregulated the gene set of G2/M checkpoint, however lenalidomide did not. These results were also confirmed by analyzing the DNA contents of MM cells using flow cytometry and by western blot analysis of cell cycle regulators, phosphorylated cdc2 and p21. These data suggest that TC11 induced apoptosis of MM cells by distinct molecular mechanism from lenalidomide probably by regulating G2/M cell cycle. TP53 gene regulates G1/S cell cycle and occasionally deleted in high-risk MM cells. However, TC11 is able to induce apoptosis of TP53 -deleted high-risk MM cells by causing G2/M arrest.(3) Inhibition of tubulin assembly by TC11:Since we have previously showed that TC11 bound to α-tubulin by IVV method, we speculated that TC11 affected tubulin polymerization or depolymerization. Treatment of MM cells with TC11 significantly reduced polymerized fraction of α-tubulin, indicating TC11 inhibited tubulin polymerization. In contrast, lenalidomide did not inhibit either tubulin polymerization or depolymerization. In this regard, the mechanism of TC11 is different from that of lenalidomide.(4) Inhibition of oligomerization of NPM1 by TC11:We have also showed that TC11 bound to NPM1 by IVV method (Shiheido et. al. PLoS One 2012). It has been reported that oligomerized NPM1 had pleiotropic biological functions. Thus we examined whether TC11 affected NPM1 oligomerization using blue native polyacrylamide gel electrophoresis. As a result, TC11 treatment significantly reduced the amount of oligomerized NPM1 fraction. At the same time, we found that TC11 significantly increased in phosphorylation of NPM1 at Ser4, Thr95 and Thr199. It has been reported that phosphorylation of NPM1 inhibited its oligomerization (Mitrea et. al. Proc Natl Acad Sci U S A 2014). Thus, we speculated that TC11-induced phosphorylation resulted in inhibition of oligomerization of NPM1.Conclusion:It was shown that TC11 bound to α-tubulin and NPM1, but not to CRBN. TC11 inhibited tubulin assembly as well as NPM1 oligomerization, leading to G2/M arrest and mitotic catastrophe. These novel molecular events by TC11 induced apoptosis of TP53 -deleted high-risk MM cells. [Display omitted] DisclosuresYonemura:IDAC Theranostics Inc.: Employment. Tabata:IDAC Theranostics Inc.: Employment. Yanagawa:IDAC Theranostics Inc.: Employment. Hattori:Cosmic Corporation Co., Ltd.: Research Funding; Merck Sharp & Dohme: Research Funding; Takeda Pharmaceutical Company Limited.: Research Funding.

Stathmin 1 Is Highly Expressed in Acute Promyelocytic Leukemia and Microtubule Dynamics Is a Potential Target for ATRA-Resistant APL Cells

Introduction : Stathmin 1 is a microtubule destabilizer protein involved in the proliferation and differentiation of early hematopoietic progenitors. Aberrant Stathmin 1 expression has been reported in hematological malignancies. Stathmin 1 silencing reduces cell proliferation and clonogenicity of leukemia cell lines. A previous study identified that the PML-RARα fusion protein, which is necessary to acute promyelocytic leukemia (APL) genesis, positively regulates Stathmin 1 at transcription and protein activity levels. However, Stathmin 1 expression and its impact on prognosis and leukemia cell biology have rarely been studied in APL. Objectives : To evaluate Stathmin 1 expression and its association with laboratory and clinical parameters in a cohort of APL patients. To investigate Stathmin 1 expression and activity upon all-trans retinoic acid (ATRA) treatment and during cell cycle in the PML-RARα cell lines. Finally, to phenocopy the effects of Stathmin 1 inhibition using the pharmacological microtubule stabilizing agent paclitaxel. Methods : Bone marrow samples from 121 APL patients enrolled in the International Consortium on Acute Promyelocytic Leukemia (IC-APL) at diagnosis and 22 healthy donors were included. Patients were treated with ATRA and chemotherapy as described elsewhere. Patients were dichotomized according to Stathmin 1 expression using the median as cut-off. The PML-RARα cell lines, NB4 (ATRA-sensible) and NB4-R2 (ATRA-resistant) were used for functional assays. Cell cycle was synchronized by double thymidine block. For dose-response curves (MTT), PML-RARα cells were treated with graded concentrations of paclitaxel and IC50 values were calculated using a nonlinear regression analysis. For apoptosis assay (annexin V/PI), PML-RARα cells were treated with ATRA (1 µM) and/or IC50 paclitaxel dose for 72 hours. Gene and protein expressions were evaluated by qPCR and Western blot, and microtubule networks by confocal microscopy. For statistical analyses, Fisher's exact test or Chi-square test were used to compare categorical variables. Mann-Whitney test, t Student test or ANOVA test and Bonferroni post-test were used to compare continuous variables. Log-rank test and Cox regression were used for survival analyzes. P -value <0.05 was considerate statistically significant. Results : Stathmin 1 transcripts were significantly increased in bone marrow samples from APL patients compared with healthy donors (median 1.21 [range 0.02-4.62] versus (vs.) 0.66 [0.01-1.71]; p <0.01). Stathmin 1 levels did not impact on disease-free survival, overall survival and complete remission rates of APL patients. No relevant association between Stathmin 1 expression and clinical and laboratory parameters were observed. In NB4 cells, but not in NB4-R2, ATRA induced granulocytic differentiation, associated with a prominent reduction of Stathmin 1 gene and protein expression (p <0.05). Paradoxically, ATRA-induced granulocytic differentiation strongly reduced α-tubulin acetylation (microtubule stability marker) in NB4 cells. Using thymidine-synchronized cells, we observed that Stathmin 1 phosphorylation at serine 16 (an inhibitory site) was predominant in pool of mitosis-enriched cells, and its phosphorylation was marked reduced in pool of G1-enriched cells. NB4 and NB4-R2 cells presented high sensibility to paclitaxel treatment (IC50 of 3.6 nM and 1.8 nM, respectively). In NB4-R2 cells, but not in NB4 cells, paclitaxel increased the number of apoptotic cells after 72 hours of ATRA treatment; increased annexin V and caspase 3 cleavage (p <0.05). Paclitaxel treatment increased acetyl-α-tubulin, y-H2AX and CDKN1A levels. Conclusions : Stathmin 1 is highly expressed, but does not impact clinical outcomes in APL patients. Stathmin 1 reduces during ATRA-induced cell differentiation. Stathmin 1 activity is reduced during mitosis (as demonstrate by increased p-Stathmin 1S16) and increases post-mitosis (reduced p-Stathmin 1S16), indicating that this protein participates in microtubule dynamics and cell cycle progression in PML-RARα cells. Paclitaxel was an efficient pharmacological agent in inducing microtubule stabilization, reducing cell viability, increasing mitotic catastrophe as monotherapy or in combination with ATRA, in PML-RARα cells, including ATRA-resistant cells. Our study provides new insights on Stathmin 1 and microtubule dynamics in APL. DisclosuresBittencourt:Janssen, Takeda: Honoraria.

Endothelial Immunity Trained by Coronavirus Infections, DAMP Stimulations and Regulated by Anti-Oxidant NRF2 May Contribute to Inflammations, Myelopoiesis, COVID-19 Cytokine Storms and Thromboembolism.

To characterize transcriptomic changes in endothelial cells (ECs) infected by coronaviruses, and stimulated by DAMPs, the expressions of 1311 innate immune regulatomic genes (IGs) were examined in 28 EC microarray datasets with 7 monocyte datasets as controls. We made the following findings: The majority of IGs are upregulated in the first 12 hours post-infection (PI), and maintained until 48 hours PI in human microvascular EC infected by middle east respiratory syndrome-coronavirus (MERS-CoV) (an EC model for COVID-19). The expressions of IGs are modulated in 21 human EC transcriptomic datasets by various PAMPs/DAMPs, including LPS, LPC, shear stress, hyperlipidemia and oxLDL. Upregulation of many IGs such as nucleic acid sensors are shared between ECs infected by MERS-CoV and those stimulated by PAMPs and DAMPs. Human heart EC and mouse aortic EC express all four types of coronavirus receptors such as ANPEP, CEACAM1, ACE2, DPP4 and virus entry facilitator TMPRSS2 (heart EC); most of coronavirus replication-transcription protein complexes are expressed in HMEC, which contribute to viremia, thromboembolism, and cardiovascular comorbidities of COVID-19. ECs have novel trained immunity (TI), in which subsequent inflammation is enhanced. Upregulated proinflammatory cytokines such as TNFα, IL6, CSF1 and CSF3 and TI marker IL-32 as well as TI metabolic enzymes and epigenetic enzymes indicate TI function in HMEC infected by MERS-CoV, which may drive cytokine storms. Upregulated CSF1 and CSF3 demonstrate a novel function of ECs in promoting myelopoiesis. Mechanistically, the ER stress and ROS, together with decreased mitochondrial OXPHOS complexes, facilitate a proinflammatory response and TI. Additionally, an increase of the regulators of mitotic catastrophe cell death, apoptosis, ferroptosis, inflammasomes-driven pyroptosis in ECs infected with MERS-CoV and the upregulation of pro-thrombogenic factors increase thromboembolism potential. Finally, NRF2-suppressed ROS regulate innate immune responses, TI, thrombosis, EC inflammation and death. These transcriptomic results provide novel insights on the roles of ECs in coronavirus infections such as COVID-19, cardiovascular diseases (CVD), inflammation, transplantation, autoimmune disease and cancers.

Targeting DNA Repair Mechanisms to Overcome Drug Resistance in Diffuse Large B Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) accounts for 30-40% of adult non-Hodgkin lymphomas. Most DLBCL patients achieve long-term remission after treatment, but a third relapse after conventional Rituximab (R)-based chemotherapy regimens, such as CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) (Siegel et al, 2012).Cancer cells are exposed to chronic replication stress, which impedes the duplication of their genome and induces mitotic catastrophe (Shaheen et al, 2011). Functional DNA repair pathways are therefore important for the survival of cancer cells. This dependence can be exploited therapeutically to hamper repair of the intrinsic DNA damage occurring during replication or to exacerbate DNA damage induced by chemotherapy (Shaheen et al, Blood 2011). Furthermore, high-risk DLBCL patients overexpress genes potentially involved in resistance to CHOP-based regimens, such as genes of the nucleotide excision repair (NER) pathway (Bret et al, Oncotarget 2012, Cell Cycle 2013).We recently developed GEP-based DNA repair scores that allow to identify high-risk DLBCL patients that could benefit from treatment with DNA repair inhibitors (Bret at al, BJH 2015).DLBCL treatments include cyclophosphamide, a nitrogen mustard derivate that induces interstrand crosslinks (ICLs), and doxorubicin, a DNA topoisomerase inhibitor that induces DNA double-strand breaks, DNA adducts and formaldehyde-dependent ICL formation. Inhibiting DNA repair is a promising strategy to improve the efficacy of genotoxic drugs and overcome drug resistance. Our data support the view that inhibitors of DNA damage signaling and DNA repair have potential therapeutic interest in DLBCL.We characterized the drug-response of 16 DLBCL cell lines to 9 DNA repair inhibitors including PJ34 (PARP inhibitor), NU7441 (DNAPK inhibitor), KU55933 (ATM inhibitor), PF477736 (CHK1/2 inhibitor), AZD6738 (ATR inhibitor), MK8776 (CHK1 inhibitor), AZD1775 (Wee1 inhibitor), MP-470 (Rad51 inhibitor), Lomeguatrib (MGMT) and genotoxic agents used in DLBCL treatment (Cyclophosphamide, Gemcitabine, Doxorubicin and Etoposide) (Table 1). All drugs induced significant apoptosis (Annexin V staining and PARP cleavage) and significant inhibition of proliferation (BrdU incorporation) in the different DLBCL cell lines tested (P <0.05). CHK1/2 inhibitor, Wee1 inhibitor, Cyclophosphamide, Gemcitabine and Doxorubicin induced DNA damages monitored by H2AX phosphorylation. Correlating drug response of each compounds with our GEP-based DNA repair scores (Bret et al, BJH 2015), we identified a significant correlation between FANC score and response to ATR inhibitor (AZD6738) and HRR score/BER score and response to Etoposide (P<0.05). High-risk DLBCL patients identified with GEP-based FANC, HRR and BER scores may benefit from treatment by ATR inhibitors or Etoposide respectively.Since DNA repair pathways play a role in drug resistance, we sought to identify new synthetic lethal and synergistic combinations associating IC20 of DNA repair targeted treatments with conventional genotoxic agents in DLBCL. Applying a standard threshold of 2 SDs below the IC50 of the genotoxic agent alone, a total of 3 synthetic lethal combinations have been identified including cyclophosphamide with CHK1/2 inhibitor (PF477736) (IC50 reduced from 2.63 µM to 1.20 µM), cyclophosphamide and ATR inhibitor (AZD6738) (IC50 reduced from 2.63 µM to 0.74 µM) and doxorubicin with DNAPK inhibitor (NU7441) (IC50 reduced from 57 nM to 14 nM).Furthermore we identified new potent synergistic combinations (combination index < 1) including CHK1/2 inhibitor (PF477736) with etoposide (IC50 reduced from 560 nM to 437 nM), ATR inhibitor (AZD6738) (IC50 reduced from 560 nM to 364 nM) with etoposide and ATM inhibitor (KU55933) with etoposide (IC50 reduced from 560 nM to 269 nM).Despite overall improvements in the treatment of DLBCL, including the use of rituximab, approximately one-third of patients fail to achieve complete remission or experience relapse. This remains a major cause of morbidity and mortality. The DNA repair scores could be useful to identify high-risk DLBCL patients and define the best synthetic lethal approach combining DNA repair inhibitors with conventional chemotherapy. These results open new perspectives to improve the treatment of DLBCL patients and provide new strategies to overcome drug resistance. [Display omitted] DisclosuresCartron:Sanofi, BMS, Jansen, celgene, Roche, Gilead: Equity Ownership; Celgene: Consultancy, Employment; Roche: Consultancy, Equity Ownership, Honoraria, Research Funding.

ATR Inhibition Induces CDK1-SPOP Signaling and Enhances Anti-PD-L1 Cytotoxicity in Prostate Cancer.

Despite significant benefit for other cancer subtypes, immune checkpoint blockade (ICB) therapy has not yet been shown to significantly improve outcomes for men with castration-resistant prostate cancer (CRPC). Prior data have shown that DNA damage response (DDR) deficiency, via genetic alteration and/or pharmacologic induction using DDR inhibitors (DDRi), may improve ICB response in solid tumors in part due to induction of mitotic catastrophe and innate immune activation. Discerning the underlying mechanisms of this DDRi-ICB interaction in a prostate cancer-specific manner is vital to guide novel clinical trials and provide durable clinical responses for men with CRPC. We treated prostate cancer cell lines with potent, specific inhibitors of ATR kinase, as well as with PARP inhibitor, olaparib. We performed analyses of cGAS-STING and DDR signaling in treated cells, and treated a syngeneic androgen-indifferent, prostate cancer model with combined ATR inhibition and anti-programmed death ligand 1 (anti-PD-L1), and performed single-cell RNA sequencing analysis in treated tumors. ATR inhibitor (ATRi; BAY1895433) directly repressed ATR-CHK1 signaling, activated CDK1-SPOP axis, leading to destabilization of PD-L1 protein. These effects of ATRi are distinct from those of olaparib, and resulted in a cGAS-STING-initiated, IFN-β-mediated, autocrine, apoptotic response in CRPC. The combination of ATRi with anti-PD-L1 therapy resulted in robust innate immune activation and a synergistic, T-cell-dependent therapeutic response in our syngeneic mouse model. This work provides a molecular mechanistic rationale for combining ATR-targeted agents with immune checkpoint blockade for patients with CRPC. Multiple early-phase clinical trials of this combination are underway.

Targeting glioma cells by antineoplastic activity of reversine.

Gliomas are the most common type of primary central nervous system tumors and despite great advances in understanding the molecular basis of the disease very few new therapies have been developed. Reversine, a synthetic purine analog, is a multikinase inhibitor that targets aurora kinase A (AURKA) and aurora kinase B (AURKB). In gliomas, a high expression of AURKA or AURKB is associated with a malignant phenotype and a poor prognosis. The present study investigated reversine-related cellular and molecular antiglioma effects in HOG, T98G and U251MG cell lines. Gene and protein expression were assessed by reverse transcription-quantitative PCR and western blotting, respectively. For functional assays, human glioma cell lines (HOG, T98G and U251MG) were exposed to increasing concentrations of reversine (0.4–50 µM) and subjected to various cellular and molecular assays. Reversine reduced the viability and clonogenicity in a dose- and/or time-dependent manner in all glioma cells, with HOG (high AURKB-expression) and T98G (high AURKA-expression) cells being more sensitive compared with U251MG cells (low AURKA- and AURKB-expression). Notably, HOG cells presented higher levels of polyploidy, while T98G presented multiple mitotic spindles, which is consistent with the main regulatory functions of AURKB and AURKA, respectively. In molecular assays, reversine reduced AURKA and/or AURKB expression/activity and increased DNA damage and apoptosis markers, but autophagy-related proteins were not modulated. In conclusion, reversine potently induced mitotic catastrophe and apoptosis in glioma cells and higher basal levels of aurora kinases and genes responsive to DNA damage and may predict improved antiglioma responses to the drug. Reversine may be a potential novel drug in the antineoplastic arsenal against gliomas.

Targeting of lactate dehydrogenase C dysregulates the cell cycle and sensitizes breast cancer cells to DNA damage response targeted therapy.

The cancer testis antigen (CTA) lactate dehydrogenase C (LDHC) is a promising anticancer target with tumor‐specific expression and immunogenicity. Interrogation of breast cancer patient cohorts from The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) indicate that upregulation of LDHC expression correlates with unfavorable prognosis. Although the role of LDHC is well characterized in spermatocytes, its role in tumors remains largely unknown. We investigated whether LDHC is involved in regulating genomic stability and whether it could be targeted to affect tumor cellular fitness. Silencing LDHC in four breast cancer cell lines significantly increased the presence of giant cells, nuclear aberrations, DNA damage, and apoptosis. LDHC‐silenced cells demonstrated aberrant cell cycle progression with differential expression of cell cycle checkpoint and DNA damage response regulators. In addition, LDHC silencing‐induced microtubule destabilization, culminating in increased mitotic catastrophe and reduced long‐term survival. Notably, the clonogenicity of LDHC‐silenced cells was further reduced by treatment with the poly (ADP‐ribose) polymerase (PARP) inhibitor olaparib and with the DNA‐damaging drug cisplatin. This study supports the therapeutic potential of targeting LDHC to mitigate cancer cell survival and improve sensitivity to agents that cause DNA damage or inhibit its repair.

MCDB: A comprehensive curated mitotic catastrophe database for retrieval, protein sequence alignment, and target prediction

Mitotic catastrophe (MC) is a form of programmed cell death induced by mitotic process disorders, which is very important in tumor prevention, development, and drug resistance. Because rapidly increased data for MC is vigorously promoting the tumor-related biomedical and clinical study, it is urgent for us to develop a professional and comprehensive database to curate MC-related data. Mitotic Catastrophe Database (MCDB) consists of 1214 genes/proteins and 5014 compounds collected and organized from more than 8000 research articles. Also, MCDB defines the confidence level, classification criteria, and uniform naming rules for MC-related data, which greatly improves data reliability and retrieval convenience. Moreover, MCDB develops protein sequence alignment and target prediction functions. The former can be used to predict new potential MC-related genes and proteins, and the latter can facilitate the identification of potential target proteins of unknown MC-related compounds. In short, MCDB is such a proprietary, standard, and comprehensive database for MC-relate data that will facilitate the exploration of MC from chemists to biologists in the fields of medicinal chemistry, molecular biology, bioinformatics, oncology and so on. The MCDB is distributed on http://www.combio-lezhang.online/MCDB/index_html/.

EMBR-23. KIF11 DEPENDENCY ON P53 MUTATIONAL STATUS IN MEDULLOBLASTOMA

IntroductionKIF11, a mitotic kinesin, is a component responsible for assembly and maintenance of mitotic spindle during mitosis. Tumor cells can upregulate KIF11. Inhibition of KIF11 results monopolar spindle formation, resulting in monoastral mitosis in cells. This activates the spindle assembly checkpoint, cells are arrested and prevented from entering cell cycle, resulting in cell death via apoptosis or necrosis, cell division with aneuploidy or mitotic slippage without division into tetraploid G1 phase. MethodsWe hypothesized that the effect of KIF11 inhibition on medulloblastoma (MB) is dependent of its p53 mutational status. ResultsOur findings on Hoechst staining demonstrated a small molecule inhibitor of KIF11 which induced apoptosis in p53-wildtype MB cells at 48h (p<0.0001), was able to trigger mitotic catastrophe (p = 0.0010) in p53-mutant MB cells at 24h and subsequent necrosis (p=0.0039) at 48h. KIF11 inhibitor exerted anti-proliferative effects on five MB cell lines at nanomolar concentration range, independent of its p53 mutational status. Cells treated with KIF11 inhibitor were arrested in G2/M phase. Apoptosis was observed on Annexin V flow cytometry 24h after treatment, followed by necrosis after 48h in p53-wildtype cells. In contrast, treated p53-mutant cells underwent necrosis at 24h. Differences in cell death mechanisms upon KIF11 inhibition was confirmed on immunoblotting by upregulated p53 expression and presence of cleaved-PARP and DNA-damage marker in p53-wildtype cells, indicative of apoptosis. While inhibition of KIF11 and increased p53 expression were observed only after 48h, cleaved-PARP expression was detected as early as 24h in p53-wildtype, suggesting KIF11-independent, cleaved-PARP-mediated cell death at 24h. In contrast, treated p53-mutant cells showed decreased p53 expression and absence of cleaved-PARP and DNA-damage marker after 24h. ConclusionsOur results suggest that when mitotic arrest is induced, p53-mutant MB cells undergo mitotic catastrophe and necrosis while p53-wildtype MB cells predominantly undergo apoptosis.

Resistance of bone marrow stroma to genotoxic preconditioning is determined by p53

Transplantation of bone marrow (BM) is made possible by the differential sensitivity of its stromal and hematopoietic components to preconditioning by radiation and/or chemotherapeutic drugs. These genotoxic treatments eliminate host hematopoietic precursors by inducing p53-mediated apoptosis but keep the stromal niche sufficiently intact for the engraftment of donor hematopoietic cells. We found that p53-null mice cannot be rescued by BM transplantation (BMT) from even the lowest lethal dose of total body irradiation (TBI). We compared structural changes in BM stroma of mice differing in their p53 status to understand why donor BM failed to engraft in the irradiated p53-null mice. Irradiation did not affect the general structural integrity of BM stroma and induced massive expression of alpha-smooth muscle actin in mesenchymal cells followed by increased adiposity in p53 wild-type mice. In contrast, none of these events were found in p53-null mice, whose BM stroma underwent global structural damage following TBI. Similar differences in response to radiation were observed in in vitro-grown bone-adherent mesenchymal cells (BAMC): p53-null cells underwent mitotic catastrophe while p53 wild-type cells stayed arrested but viable. Supplementation with intact BAMC of either genotype enabled donor BM engraftment and significantly extended longevity of irradiated p53-null mice. Thus, successful preconditioning depends on the p53-mediated protection of cells critical for the functionality of BM stroma. Overall, this study reveals a dual positive role of p53 in BMT: it drives apoptotic death of hematopoietic cells and protects BM stromal cells essential for its functionality.

A first-in-human phase I study of ATR inhibitor M1774 in patients with solid tumors.

TPS3153 Background: Ataxia telangiectasia and Rad3-related (ATR) protein kinase plays a critical role in the DNA damage response by sensing and responding to DNA replication stress, and by inducing cell cycle arrest to prevent aberrant replication and mitotic catastrophe. Based on extensive preclinical and limited clinical evidence, ATR inhibition is a promising treatment strategy as monotherapy for patients with advanced tumors harboring synthetically lethal conditions, such as alternative lengthening of telomeres (ALT) and inactivating mutations in ARID1A and ATM. M1774 is a potent, selective, orally administered ATR inhibitor that has been shown to exert antitumor activity in patient-derived xenograft tumors and acute myeloid leukemia xenograft tumors that express the ATR inhibition sensitizing mixed lineage leukemia fusion protein. This study (NCT04170153) aims to evaluate the safety and tolerability, maximum tolerated dose, recommended dose for expansion (RDE) and pharmacokinetics (PK) of M1774 (part A1), the effect of food on M1774 PK (part A2), and the efficacy of M1774 in patients with tumors harboring selected mutations (part A3). An additional objective is to assess the pharmacodynamics of M1774 by measuring relative changes in baseline p-CHK1 and γ-H2AX expression in paired tumor biopsies and serial blood samples. Methods: Patients aged ≥18 years, with an Eastern Cooperative Oncology Group performance status ≤1, adequate baseline hematological, renal and hepatic function, and with locally advanced or metastatic disease refractory to standard therapy are eligible. Patients with tumors bearing loss-of-function (LoF) mutations (determined by site testing or a central trial assay) in ARID1A, ATM, or ATRX and/or DAXX as ALT status surrogate markers; and measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, will be enrolled in part A3. In the dose escalation phase (part A1 [open]), 18–24 patients are due to receive M1774 at a starting dose of 5 mg once daily. Dose escalation is determined by the safety monitoring committee and guided by a Bayesian 2-parameter logistic regression model. The preliminary food assessment (part A2) will follow a randomized two-sequence two-period crossover design in which ≤12 patients will be randomized (1:1) to receive a single dose of M1774 on Day –7 at the RDE (determined in part A1) in either a fed or fasted condition. After the food assessment, patients will subsequently receive M1774 according to the part A1 dosing schedule. In the preliminary efficacy study (part A3), patients (n = 20–24 for each of the three planned cohorts) with tumors harboring LoF mutations in the genes for ARID1A, ATM, ATRX and/or DAXX, will receive M1774 at the RDE. The primary efficacy endpoint is overall response (RECIST). The study is open and currently recruiting. Patients have been enrolled to seven cohorts in part A1 with no DLTs observed; dose escalation is ongoing. Clinical trial information: NCT04170153.

Targeting cell cycle regulation via the G2-M checkpoint for synthetic lethality in melanoma

ABSTRACT Disruption of cell cycle checkpoints has been well established as a hallmark of cancer. In particular, the G1-S transition mediated by the cyclin D-cyclin-dependent kinase 4/6 (CDK4/6) pathway is dysregulated in more than 90% of melanoma cases. Therefore, tumor cells mainly rely on the G2-M checkpoint to halt the cell cycle in order to repair DNA damage. Here, we review the promising method of cell cycle-mediated synthetic lethality for melanoma treatment, which entails exploiting somatically acquired mutations in the G1-S transition with inhibitors of the G2-M transition in order to specifically kill melanoma cells. The idea stems from the theory that melanoma cells lacking G1-S checkpoints are particularly vulnerable to mitotic catastrophe when presented with G2-M checkpoint inhibition in addition to DNA damage, whereas normal cells with intact G1-S checkpoints should theoretically be spared. This review explores the link between cell cycle dysregulation and synthetic lethality in melanoma cells and discusses potential future applications for this treatment.

The Targeting of MRE11 or RAD51 Sensitizes Colorectal Cancer Stem Cells to CHK1 Inhibition.

Simple SummaryThe ATR-CHK1 axis of the DNA damage response is crucial for the survival of most colorectal cancer stem cells (CRC-SCs), but a significant fraction of primary CRC-SCs either is resistant to ATR or CHK1 inhibitors or survives the abrogation of the ATR-CHK1 cascade despite an initial response. Here, we demonstrate that the targeting of RAD51 or MRE11 improves the sensitivity of primary CRC-SCs to the CHK1/2 inhibitor prexasertib by sequentially inducing replication stress, the abrogation of cell cycle checkpoints, and the emergence of mitotic defects. This results in the induction of mitotic catastrophe and CRC-SC killing via a caspase-dependent apoptosis.Cancer stem cells (CSCs) drive not only tumor initiation and expansion, but also therapeutic resistance and tumor relapse. Therefore, CSC eradication is required for effective cancer therapy. In preclinical models, CSCs demonstrated high capability to tolerate even extensive genotoxic stress, including replication stress, because they are endowed with a very robust DNA damage response (DDR). This favors the survival of DNA-damaged CSCs instead of their inhibition via apoptosis or senescence. The DDR represents a unique CSC vulnerability, but the abrogation of the DDR through the inhibition of the ATR-CHK1 axis is effective only against some subtypes of CSCs, and resistance often emerges. Here, we analyzed the impact of druggable DDR players in the response of patient-derived colorectal CSCs (CRC-SCs) to CHK1/2 inhibitor prexasertib, identifying RAD51 and MRE11 as sensitizing targets enhancing prexasertib efficacy. We showed that combined inhibition of RAD51 and CHK1 (via B02+prexasertib) or MRE11 and CHK1 (via mirin+prexasertib) kills CSCs by affecting multiple genoprotective processes. In more detail, these two prexasertib-based regimens promote CSC eradication through a sequential mechanism involving the induction of elevated replication stress in a context in which cell cycle checkpoints usually activated during the replication stress response are abrogated. This leads to uncontrolled proliferation and premature entry into mitosis of replication-stressed cells, followed by the induction of mitotic catastrophe. CRC-SCs subjected to RAD51+CHK1 inhibitors or MRE11+CHK1 inhibitors are eventually eliminated, and CRC-SC tumorspheres inhibited or disaggregated, via a caspase-dependent apoptosis. These results support further clinical development of these prexasertib-based regimens in colorectal cancer patients.

Invitro induction of mitotic catastrophe as a therapeutic approach for oral cancer using the ethanolic extract of Juniperus squamata.

Mitotic catastrophe, a cell death mechanism characterized by abnormal mitosis, has been regarded as a therapeutic approach for the development of anti‑cancer drug candidates. The aim of the present study was to investigate the potential effect of the ethanolic extract of Juniperus squamata(EEJS) on the occurrence of mitotic catastrophe in human oral cancer cell lines. The effect of EEJS on the occurrence of mitotic catastrophe was evaluated by measuring cytotoxicity, observing phase‑contrast or transmission electron microscope findings, evaluating the appearance of microtubule or chromosome abnormalities, and detecting the phosphorylation of histoneH3(Ser10). The apoptotic effect of EEJS was assessed by detecting cleaved PARP, analyzing the sub‑G1 population, AnnexinV‑FITC/PI double staining, western blot analysis, and the transient transfection of myeloid cell leukemia‑1(Mcl‑1) overexpression vectors. EEJS treatment was effective in inhibiting cell proliferation in human oral cancer cell lines. EEJS resulted in the enrichment of enlarged multinucleated cells, the disturbance of microtubule formation, and increased phosphorylation of histoneH3 (Ser10), which demonstrates the occurrence of mitotic catastrophe. Additionally, the multinucleated cells underwent apoptotic cell death in a cell context‑dependent manner, which was associated with the reduction of Mcl‑1 protein levels. Findings of the present study indicate that EEJS could be effective for treating human oral cancer by promoting mitotic catastrophe linked to apoptotic cell death.