DNA topoisomerase II in therapy-related acute promyelocytic leukemia

Single-cell EpiChem jointly measures drug-chromatin binding and multimodal epigenome

Studies of molecular and cellular functions of small-molecule inhibitors in cancer treatment, eliciting effects by targeting genome and epigenome associated proteins, requires measurement of drug-target engagement in single-cell resolution. Here we present EpiChem for in situ single-cell joint mapping of small molecules and multimodal epigenomic landscape. We demonstrate single-cell co-assays of three small molecules together with histone modifications, chromatin accessibility or target proteins in human colorectal cancer (CRC) organoids. Integrated multimodal analysis reveals diverse drug interactions in the context of chromatin states within heterogeneous CRC organoids. We further reveal drug genomic binding dynamics and adaptive epigenome across cell types after small-molecule drug treatment in CRC organoids. This method provides a unique tool to exploit the mechanisms of cell type-specific drug actions.

Myeloperoxidase inhibition protects bone marrow mononuclear cells from DNA damage induced by the TOP2 poison anti-cancer drug etoposide

Myeloperoxidase (MPO) is found almost exclusively in granulocytes and immature myeloid cells. It plays a key role in the innate immune system, catalysing the formation of reactive oxygen species that are important in anti-microbial action, but MPO also oxidatively transforms the topoisomerase II (TOP2) poison etoposide to chemical forms that have elevated DNA damaging properties. TOP2 poisons such as etoposide are widely used anti-cancer drugs, but they are linked to cases of secondary acute myeloid leukaemias through a mechanism that involves DNA damage and presumably erroneous repair leading to leukaemogenic chromosome translocations. This leads to the possibility that myeloperoxidase inhibitors could reduce the rate of therapy-related leukaemia by protecting haematopoietic cells from TOP2 poison-mediated genotoxic damage while preserving the anti-cancer efficacy of the treatment. We show here that myeloperoxidase inhibition reduces etoposide-induced TOP2B-DNA covalent complexes and resulting DNA double-strand break formation in primary ex vivo expanded CD34+ progenitor cells and unfractionated bone marrow mononuclear cells. Since MPO inhibitors are currently being developed as anti-inflammatory agents this raises the possibility that repurposing of these potential new drugs could provide a means of suppressing secondary acute myeloid leukaemias associated with therapies containing TOP2 poisons.

Therapy-Related Myeloid Neoplasm: Biology and Mechanistic Aspects of Malignant Progression

Therapy-related myeloid neoplasms (t-MN) arise after a documented history of chemo/radiotherapy as treatment for an unrelated condition and account for 10-20% of myelodysplastic syndromes and acute myeloid leukemia. T-MN are characterized by a specific genetic signature, aggressive features and dismal prognosis. The nomenclature and the subsets of these conditions have changed frequently over time, and despite the fact that, in the last classification, they lost their autonomous entity status and became disease qualifiers, the recognition of this feature remains of major importance. Furthermore, in recent years, extensive studies focusing on clonal hematopoiesis and germline variants shed light on the mechanisms of positive pressure underpinning the rise of driver gene mutations in t-MN. In this manuscript, we aim to review the evolution of defining criteria and characteristics of t-MN from a clinical and biological perspective, the advances in mechanistic aspects of malignant progression and the challenges in prevention and management.

Ubiquitin-specific peptidase 11 promotes development of keloid derived fibroblasts by de-ubiquitinating TGF-β receptorII

BACKGROUND

Keloid scars occur as a result of abnormal wound healing caused by trauma or inflammation of the skin. The progression of keloids is dependent on genetic and environmental influences. The incidence is more prevalent in people with darker skin tones (African, Asian and Hispanic origin). Studies have demonstrated that transforming growth factor (TGF) β/Smad signalling has an essential function in keloid as well as that USP11 could modulate the activation of TGFβ/Smad signalling and impact the progression of the fibrotic disease. Nonetheless, the potential mechanisms of USP11 in keloid were still unclear. The authors postulated that USP11 up-regulates and augments the ability of proliferation, invasion, migration and collagen deposition of keloid-derived fibroblasts (KFBs) through deubiquitinating TGF-β receptor II (TβRII).

METHODS

Fibroblast cells were isolated from keloid scars in vitro. Lentivirus infection was utilized to knockdown and over-express the USP11 in KFBs. Influence of USP11 on proliferation, invasion and migration of KFBs, and expression level of TβRII, Smad2, Smad3, α-SMA, collagen1 and collagen3 were assayed by CCK8, scratching, transwell, Western blot and real-time quantitative polymerase chain reaction. The interactions between USP11 and TβRII were examined using ubiquitination assays and co-immunoprecipitation. To further confirm the role of USP11 in keloid growth, we performed animal experiments.

RESULTS

Results show that down-regulated USP11 markedly suppressed the ability of proliferation, invasion and migration of keloid derived-fibroblasts in vitro and reduce the expression of TβRII, Smad2, Smad3, αSMA, collagen1 and collagen3. In addition, over-expression of USP11 demonstrated the contrary tendency. Ubiquitination experiments and co-immunoprecipitation demonstrated that USP11 was interacting with TβRII and deubiquitinated TβRII. Interferences with USP11 inhibited growth of keloid in vivo. Additionally, we have verified that knockdown of USP11 has no significant effect on normal skin fibroblasts.

CONCLUSION

USP11 elevates the ability of proliferation, collagen deposition, invasion and migration of keloid-derived fibroblasts by deubiquitinating TβRII.

Poor outcome of allogeneic transplantation for therapy-related acute myeloid leukemia induced by prior chemoradiotherapy

Therapy-related acute myeloid leukemia (t-AML) is a therapeutic challenge as a late complication of chemotherapy (CHT) and/or radiotherapy (RT) for primary malignancy. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) presents itself as a curative approach. To establish the optimal allo-HSCT strategy for t-AML, we evaluated the relationship between characteristics of primary malignancy and allo-HSCT outcomes. Patients with t-AML or de novo acute myeloid leukemia (AML) who underwent first allo-HSCT in Japan from 2011 to 2018 were identified using a nationwide database. The detailed background of t-AML was obtained by additional questionnaires. Multivariate analysis and propensity score matching (PSM) analysis were performed to detect the prognostic factors associated with t-AML and compare outcomes with de novo AML. We analyzed 285 t-AML and 6761 de novo AML patients. In patients with t-AML, receiving both CHT and RT for primary malignancy was an independent poor-risk factor for relapse and overall survival (OS) (hazard ratio (HR) 1.62; p = 0.029 and HR 1.65; p = 0.009, reference: CHT alone group), whereas other primary malignancy-related factors had no effect on the outcome. Compared to the CHT alone group, complex karyotypes were significantly increased in the CHT + RT group (86.1% vs. 57.5%, p = 0.007). In the PSM cohort, t-AML patients with prior CHT and RT had significantly worse 3-year OS than those with de novo AML (25.2% and 42.7%; p = 0.009). Our results suggest that prior CHT and RT for primary malignancy may be associated with increased relapse and worse OS of allo-HSCT in t-AML.

NPM1-mutated acute myeloid leukemia: New pathogenetic and therapeutic insights and open questions

The nucleophosmin (NPM1) gene encodes for a multifunctional chaperone protein that is localized in the nucleolus but continuously shuttles between the nucleus and cytoplasm. NPM1 mutations occur in about one-third of AML, are AML-specific, usually involve exon 12 and are frequently associated with FLT3-ITD, DNMT3A, TET2, and IDH1/2 mutations. Because of its unique molecular and clinico-pathological features, NPM1-mutated AML is regarded as a distinct leukemia entity in both the International Consensus Classification (ICC) and the 5th edition of the World Health Organization (WHO) classification of myeloid neoplasms. All NPM1 mutations generate leukemic mutants that are aberrantly exported in the cytoplasm of the leukemic cells and are relevant to the pathogenesis of the disease. Here, we focus on recently identified functions of the NPM1 mutant at chromatin level and its relevance in driving HOX/MEIS gene expression. We also discuss yet controversial issues of the ICC/WHO classifications, including the biological and clinical significance of therapy-related NPM1-mutated AML and the relevance of blasts percentage in defining NPM1-mutated AML. Finally, we address the impact of new targeted therapies in NPM1-mutated AML with focus on CAR T cells directed against NPM1/HLA neoepitopes, as well as XPO1 and menin inhibitors.

Re-Exploring the Anthracycline Chemical Space for Better Anti-Cancer Compounds

The anthracycline anti-cancer drugs are intensely used in the clinic to treat a wide variety of cancers. They generate DNA double strand breaks, but recently the induction of chromatin damage was introduced as another major determinant of anti-cancer activity. The combination of these two events results in their reported side effects. While our knowledge on the structure-activity relationship of anthracyclines has improved, many structural variations remain poorly explored. Therefore, we here report on the preparation of a diverse set of anthracyclines with variations within the sugar moiety, amine alkylation pattern, saccharide chain and aglycone. We assessed the cytotoxicity in vitro in relevant human cancer cell lines, and the capacity to induce DNA- and chromatin damage. This coherent set of data allowed us to deduce a few guidelines on anthracycline design, as well as discover novel, highly potent anthracyclines that may be better tolerated by patients.

Clinical outcome of therapy-related acute myeloid leukemia patients. Real-life experience in a University Hospital and a Cancer Center in France

BACKGROUND

t-AML occurs after a primary malignancy treatment and retains a poor prognosis.

AIMS

To determine the impact of primary malignancies, therapeutic strategies, and prognostic factors on clinical outcomes of t-AML.

RESULTS

A total of 112 adult patients were included in this study. Fifty-Five patients received intensive chemotherapy (IC), 33 non-IC, and 24 best supportive care. At t-AML diagnosis, 42% and 44% of patients presented an unfavorable karyotype and unfavorable 2010 ELN risk profile, respectively. Among treated patients (n = 88), 43 (49%) achieved complete remission: four out of 33 (12%) and 39 out of 55 (71%) in non-IC and IC groups, respectively. With a median follow-up of 5.5 months, the median overall survival (OS) and disease-free survival (DFS) for the whole population were 9 months and 6.3 months, respectively, and for the 88 treated patients 13.5 months and 8.2 months, respectively. Univariate analysis on OS and DFS showed a significant impact of high white blood cells (WBC) and blast counts at diagnosis, unfavorable karyotype and ELN classification. Multivariate analysis showed a negative impact of WBC count at diagnosis and a positive impact of chemotherapy on OS and DFS in the whole population. It also showed a negative impact of previous auto-HCT and high WBC count on OS and DFS and of IC on OS in treated patients which disappeared when we considered only confounding variables (age, previous cancers, marrow blasts, and 2010 ELN classification). In a pair-matched analysis comparing IC treated t-AML with de novo AML, there was no difference of OS and DFS between the two populations.

CONCLUSION

We showed, in this study that t-AML patients with unfavorable features represented almost half of the population. Best outcomes obtained in patients receiving IC must be balanced by known confounding variables and should be improved by using new innovative agents and therapeutic strategies.

Circular RNAs drive oncogenic chromosomal translocations within the MLL recombinome in leukemia

The first step of oncogenesis is the acquisition of a repertoire of genetic mutations to initiate and sustain the malignancy. An important example of this initiation phase in acute leukemias is the formation of a potent oncogene by chromosomal translocations between the mixed lineage leukemia (MLL) gene and one of 100 translocation partners, known as the MLL recombinome. Here, we show that circular RNAs (circRNAs)-a family of covalently closed, alternatively spliced RNA molecules-are enriched within the MLL recombinome and can bind DNA, forming circRNA:DNA hybrids (circR loops) at their cognate loci. These circR loops promote transcriptional pausing, proteasome inhibition, chromatin re-organization, and DNA breakage. Importantly, overexpressing circRNAs in mouse leukemia xenograft models results in co-localization of genomic loci, de novo generation of clinically relevant chromosomal translocations mimicking the MLL recombinome, and hastening of disease onset. Our findings provide fundamental insight into the acquisition of chromosomal translocations by endogenous RNA carcinogens in leukemia.

An Overview of EGFR Mechanisms and Their Implications in Targeted Therapies for Glioblastoma

Despite all of the progress in understanding its molecular biology and pathogenesis, glioblastoma (GBM) is one of the most aggressive types of cancers, and without an efficient treatment modality at the moment, it remains largely incurable. Nowadays, one of the most frequently studied molecules with important implications in the pathogenesis of the classical subtype of GBM is the epidermal growth factor receptor (EGFR). Although many clinical trials aiming to study EGFR targeted therapies have been performed, none of them have reported promising clinical results when used in glioma patients. The resistance of GBM to these therapies was proven to be both acquired and innate, and it seems to be influenced by a cumulus of factors such as ineffective blood-brain barrier penetration, mutations, heterogeneity and compensatory signaling pathways. Recently, it was shown that EGFR possesses kinase-independent (KID) pro-survival functions in cancer cells. It seems imperative to understand how the EGFR signaling pathways function and how they interconnect with other pathways. Furthermore, it is important to identify the mechanisms of drug resistance and to develop better tailored therapeutic agents.

Recent Developments in Combination Chemotherapy for Colorectal and Breast Cancers with Topoisomerase Inhibitors

DNA topoisomerases are important enzymes that stabilize DNA supercoiling and resolve entanglements. There are two main types of topoisomerases in all cells: type I, which causes single-stranded DNA breaks, and type II, which cuts double-stranded DNA. Topoisomerase activity is particularly increased in rapidly dividing cells, such as cancer cells. Topoisomerase inhibitors have been an effective chemotherapeutic option for the treatment of several cancers. In addition, combination cancer therapy with topoisomerase inhibitors may increase therapeutic efficacy and decrease resistance or side effects. Topoisomerase inhibitors are currently being used worldwide, including in the United States, and clinical trials on the combination of topoisomerase inhibitors with other drugs are currently underway. The primary objective of this review was to comprehensively analyze the current clinical landscape concerning the combined application of irinotecan, an extensively investigated type I topoisomerase inhibitor for colorectal cancer, and doxorubicin, an extensively researched type II topoisomerase inhibitor for breast cancer, while presenting a novel approach for cancer therapy.

Overlapping features of therapy-related and de novo NPM1-mutated AML

NPM 1-mutated acute myeloid leukemia (AML) shows unique features. However, the characteristics of "therapy-related" NPM1-mutated AML (t-NPM1 AML) are poorly understood. We compared the genetics, transcriptional profile, and clinical outcomes of t-NPM1 AML, de novo NPM1-mutated AML (dn-NPM1 AML), and therapy-related AML (t-AML) with wild-type NPM1 (t-AML). Normal karyotype was more frequent in t-NPM1 AML (n = 78/96, 88%) and dn-NPM1 (n = 1986/2394, 88%) than in t-AML (n = 103/390, 28%; P < .001). DNMT3A and TET2 were mutated in 43% and 40% of t-NPM1 AML (n = 107), similar to dn-NPM1 (n = 88, 48% and 30%; P > 0.1), but more frequently than t-AML (n = 162; 14% and 10%; P < 0.001). Often mutated in t-AML, TP53 and PPM1D were wild-type in 97% and 96% of t-NPM1 AML, respectively. t-NPM1 and dn-NPM1 AML were transcriptionally similar, (including HOX genes upregulation). At 62 months of median follow-up, the 3-year overall survival (OS) for t-NPM1 AML (n = 96), dn-NPM1 AML (n = 2394), and t-AML (n = 390) were 54%, 60%, and 31%, respectively. In multivariable analysis, OS was similar for the NPM1-mutated groups (hazard ratio [HR] 0.9; 95% confidence interval [CI], 0.65-1.25; P = .45), but better in t-NPM1 AML than in t-AML (HR, 1.86; 95% CI, 1.30-2.68; P < .001). Relapse-free survival was similar between t-NPM1 and dn-NPM1 AML (HR, 1.02; 95% CI, 0.72-1.467; P = .90), but significantly higher in t-NPM1 AML versus t-AML (HR, 1.77; 95% CI, 1.19-2.64; P = .0045). t-NPM1 and dn-NPM1 AML have overlapping features, suggesting that they should be classified as a single disease entity.

Chromosomal breaks at the origin of small tandem DNA duplications

Small tandem DNA duplications in the range of 15 to 300 base-pairs play an important role in the aetiology of human disease and contribute to genome diversity. Here, we discuss different proposed mechanisms for their occurrence and argue that this type of structural variation mainly results from mutagenic repair of chromosomal breaks. This hypothesis is supported by both bioinformatical analysis of insertions occurring in the genome of different species and disease alleles, as well as by CRISPR/Cas9-based experimental data from different model systems. Recent work points to fill-in synthesis at double-stranded DNA breaks with complementary sequences, regulated by end-joining mechanisms, to account for small tandem duplications. We will review the prevalence of small tandem duplications in the population, and we will speculate on the potential sources of DNA damage that could give rise to this mutational signature. With the development of novel algorithms to analyse sequencing data, small tandem duplications are now more frequently detected in the human genome and identified as oncogenic gain-of-function mutations. Understanding their origin could lead to optimized treatment regimens to prevent therapy-induced activation of oncogenes and might expose novel vulnerabilities in cancer.

Long-term retrospective study of retinoic acid combined with arsenic and chemotherapy for acute promyelocytic leukemia

Chemotherapy, all-trans retinoic acid (ATRA), and arsenic are effective options for acute promyelocytic leukemia (APL). We conducted a 20-year retrospective analysis of newly diagnosed (ND) APL patients treated with arsenic, ATRA and mitoxantrone. After achieving complete remission (CR), patients received 3-5 cycles of chemotherapy followed by AS4S4 maintenance for 3 years. Eighty-eight ND APL patients were treated with either oral AS4S4 (n = 42) or arsenic trioxide (ATO) (n = 46). The 8-year overall survival (OS) rate was 100% in the AS4S4 group and 90% in the ATO group. The disease-free survival (DFS) rates were 100% and 87.1% (p = 0.027), respectively. Patients in the ATO group had more side effects. A subsequent cohort of 33 ND APL patients received triple therapy with oral AS4S4, ATRA, and chemotherapy. The 13-year OS and DFS rates were 100% and 90.9%. Our long-term analyses show that APL patients with oral AS4S4 had better outcomes compared to ATO, with no need for hospitalization.

Dual Targeting Topoisomerase/G-Quadruplex Agents in Cancer Therapy-An Overview

Topoisomerase (Topo) inhibitors have long been known as clinically effective drugs, while G-quadruplex (G4)-targeting compounds are emerging as a promising new strategy to target tumor cells and could support personalized treatment approaches in the near future. G-quadruplex (G4) is a secondary four-stranded DNA helical structure constituted of guanine-rich nucleic acids, and its stabilization impairs telomere replication, triggering the activation of several protein factors at telomere levels, including Topos. Thus, the pharmacological intervention through the simultaneous G4 stabilization and Topos inhibition offers a new opportunity to achieve greater antiproliferative activity and circumvent cellular insensitivity and resistance. In this line, dual ligands targeting both Topos and G4 emerge as innovative, efficient agents in cancer therapy. Although the research in this field is still limited, to date, some chemotypes have been identified, showing this dual activity and an interesting pharmacological profile. This paper reviews the available literature on dual Topo inhibitors/G4 stabilizing agents, with particular attention to the structure-activity relationship studies correlating the dual activity with the cytotoxic activity.

Single-cell analysis reveals selection of TP53-mutated clones after MDM2 inhibition

The mechanisms of transformation of chronic myeloproliferative neoplasms (MPN) to leukemia are largely unknown, but TP53 mutations acquisition is considered a key event in this process. p53 is a main tumor suppressor, but mutations in this protein per se do not confer a proliferative advantage to the cells, and a selection process is needed for the expansion of mutant clones. MDM2 inhibitors may rescue normal p53 from degradation and have been evaluated in a variety of cancers with promising results. However, the impact of these drugs on TP53-mutated cells is underexplored. We report herein evidence of a direct effect of MDM2 inhibition on the selection of MPN patients' cells harboring TP53 mutations. To decipher whether these mutations can arise in a specific molecular context, we used a DNA single-cell approach to determine the clonal architecture of TP53-mutated cells. We observed that TP53 mutations are late events in MPN, mainly occurring in the driver clone, whereas clonal evolution frequently consists of sequential branching instead of linear consecutive acquisition of mutations in the same clone. At the single-cell level, the presence of additional mutations does not influence the selection of TP53 mutant cells by MDM2 inhibitor treatment. Also, we describe an in vitro test allowing to predict the emergence of TP53 mutated clones. Altogether, this is the first demonstration that a drug treatment can directly favor the emergence of TP53-mutated subclones in MPN.

Human topoisomerases and their roles in genome stability and organization

Human topoisomerases comprise a family of six enzymes: two type IB (TOP1 and mitochondrial TOP1 (TOP1MT), two type IIA (TOP2A and TOP2B) and two type IA (TOP3A and TOP3B) topoisomerases. In this Review, we discuss their biochemistry and their roles in transcription, DNA replication and chromatin remodelling, and highlight the recent progress made in understanding TOP3A and TOP3B. Because of recent advances in elucidating the high-order organization of the genome through chromatin loops and topologically associating domains (TADs), we integrate the functions of topoisomerases with genome organization. We also discuss the physiological and pathological formation of irreversible topoisomerase cleavage complexes (TOPccs) as they generate topoisomerase DNA–protein crosslinks (TOP-DPCs) coupled with DNA breaks. We discuss the expanding number of redundant pathways that repair TOP-DPCs, and the defects in those pathways, which are increasingly recognized as source of genomic damage leading to neurological diseases and cancer.

Topoisomerases have essential roles in transcription, DNA replication, chromatin remodelling and, as recently revealed, 3D genome organization. However, topoisomerases also generate DNA–protein crosslinks coupled with DNA breaks, which are increasingly recognized as a source of disease-causing genomic damage.

Aconitine linoleate, a natural lipo-diterpenoid alkaloid, stimulates anti-proliferative activity reversing doxorubicin resistance in MCF-7/ADR breast cancer cells as a selective topoisomerase IIα inhibitor

Aconitine linoleate (1) is a lipo-diterpenoid alkaloid, isolated from Aconitum sinchiangense W. T. Wang. The study aimed at investigating the anti-proliferative efficacy and the underlying mechanisms of 1 against MCF-7 and MCF-7/ADR cells, as well as obvious the safety evaluation in vivo. The cytotoxic activities of 1 were measured in vitro. Also, we investigated the latent mechanism of 1 by cell cycle analysis in MCF-7/ADR cells and topo I and topo IIα inhibition assay. Molecular docking is done by Discovery Studio 3.5 and Autodock vina 1.1.2. Finally, the acute toxicity of 1 was detected on mice. 1 exhibited significant antitumor activity against both MCF-7 and MCF-7/ADR cells, with IC50 values of 7.58 and 7.02 μM, which is 2.38 times and 5.05 times more active, respectively than etoposide in both cell lines, and being 9.63 times more active than Adriamycin in MCF-7/ADR cell lines. The molecular docking and the topo inhibition test found that it is a selective inhibitor of topoisomerase IIα. Moreover, activation of the damage response pathway of the DNA leads to cell cycle arrest at the G0G1 phase. Furthermore, the in vivo acute toxicity of 1 in mice displayed lower toxicity than aconitine, with LD50 of 2.2 × 105 nmol/kg and only slight pathological changes in liver and lung tissue, 489 times safer than aconitine. In conclusion, compared with aconitine, 1 has more significant anti-proliferative activity against MCF-7 and MCF-7/ADR cells and greatly reduces in vivo toxicity, which suggests this kind of lipo-alkaloids is powerful and promising antitumor compounds for breast cancer.

Synthetic enamine naphthoquinone derived from lawsone as cytotoxic agents assessed by in vitro and in silico evaluations

We synthesized ten enamine naphthoquinones with yields ranging from 43 to 76%. These compounds were screened for their in vitro antiproliferative activities by MTT assay against four types of human cancer cell lines: HCT116, PC3, HL60 and SNB19. The naphthoquinones bearing the picolylamine (7) and quinoline (12) moieties were the most actives (IC₅₀ < 24 μM for all the cell lines), which were comparable or better to the values obtained for the control drugs. In silico evaluations allowed us to develop a qualitative Structure-Activity Relationship which suggest that electrostatic features, particularly the C₂-C₃ internuclear repulsion and the molecular dipole moment, relate to the biological response. Furthermore, Molecular Docking simulations indicate that the synthetic compounds have the potential to act as anticancer molecules by inhibiting topoisomerase-II and thymidylate synthase.

Molecular Landscape of Therapy-related Myeloid Neoplasms in Patients Previously Treated for Gynecologic and Breast Cancers

Definition of therapy-related myeloid neoplasms (TRMN) is only based on clinical history of exposure to leukemogenic therapy. No specific molecular classification combining therapy-related acute myeloid leukemia and therapy-related myelodysplastic syndromes has been proposed. We aimed to describe the molecular landscape of TRMN at diagnosis, among 77 patients with previous gynecologic and breast cancer with a dedicated next-generation sequencing panel covering 74 genes. We investigated the impact of clonal hematopoiesis of indeterminate potential-associated mutations (CHIP-AMs defined as presence at TRMN stage of mutations described in CHIP with a frequency >1%) on overall survival (OS) and the clinical relevance of a modified genetic ontogeny-based classifier that categorized patients in 3 subgroups. The most frequently mutated genes were TP53 (31%), DNMT3A (19%), IDH1/2 (13%), NRAS (13%), TET2 (12%), NPM1 (10%), PPM1D (9%), and PTPN11 (9%). CHIP-AMs were detected in 66% of TRMN patients, with no impact on OS. Yet, patients with CHIP-AM were older and had a longer time interval between solid tumor diagnosis and TRMN. According to our modified ontogeny-based classifier, we observed that the patients with TP53 or PPM1D mutations had more treatment lines and complex karyotypes, the “MDS-like” patients were older with more gene mutations, while patients with “De novo/pan-AML” mutations were younger with more balanced chromosomal translocations. Median OS within each subgroup was 7.5, 14.5, and 25.2 months, respectively, with statistically significant difference in multivariate analysis. These results support the integration of cytogenetic and molecular markers into the future TRMN classification to reflect the biological diversity of TRMN and its impact on outcomes.

Differential Survival Outcomes Between De Novo and Secondary Acute Promyelocytic Leukemia: An Updated Population-based study

BACKGROUND

Whether the characteristics and outcome of secondary acute promyelocytic leukemia (s-APL) are similar to de no APL (dn-APL) remains unknown.

PATIENTS AND METHODS

Using the SEER database, we identified 3877 patients with APL diagnosed from 2000 to 2014, including 465 s-APL and 3412 dn-APL.

RESULTS

Compared with dn-APL, s-APL werecharacterized by older median age, and a higher early mortality rate. Multivariate Cox model showed s-APL, older age, earlier year of diagnosis, and male gender were independently associated with worse survival. Notably, s-APL had a significantly inferior survival regardless of gender, race, marital status, and year of diagnosis. However, the difference between the 2 cohorts was only evident in younger patients (≤ 65 years) but was lost in older patients (> 65 years). Additionally, the majority of index cancer type was breast and prostate in female and male s-APL, respectively. Latency < 3 years was associated with superior survival in s-APL with breast index cancer.

CONCLUSIONS

Inferior survival of s-APL points to the need for treatment improvement.

Sequential Phase II clinical trials evaluating CRLX101 as monotherapy and in combination with bevacizumab in recurrent ovarian cancer

BACKGROUND

Topoisomerase-1 inhibitors are an important class of cytotoxics associated with toxicity that limits their use. CRLX101 is a novel cyclodextrin-containing polymer conjugate of camptothecin (CPT) that self-assembles into nanoparticles to deliver sustained levels of active CPT into cancer cells while substantially reducing systemic exposure.

METHODS

We conducted sequential phase II, open label, single arm clinical trials to evaluate CRLX101 as a single agent (n = 29) and with bevacizumab (Bev) (n = 34). Patients (pts) had measurable recurrent epithelial ovarian, tubal or primary peritoneal cancer, that could be platinum refractory, resistant or sensitive. Cohort A (Single agent CRLX101) allowed up to 3 prior chemotherapy regimens, but no prior topo-1 inhibitors. Pts received CRLX101 15 mg/m² IV every 14 days Q28 with response evaluation every 2 cycles. Cohort B also received Bev 10 mg/kg D1,15 Q28, and included only platinum resistant disease with up to 2 prior lines, and more rigorous eligibility criteria.

RESULTS

CRLX101 was well tolerated other than nausea, fatigue and anemia. 29 pts. received a median of 3 (1-16) cycles with a clinical benefit rate (CBR) of 68% and overall response rate (ORR) of 11%. With the addition of Bev in Cohort B (n = 34), the CBR was increased to 95% and the ORR to 18%. PFS was 4.5 months (0.9 to 15.9 months) in Cohort A and 6.5 months (2.8 to 14.4 months) in Cohort B. Bev increased the incidence of hypertension and qualitatively increased bladder toxicities, but without SAEs.

CONCLUSIONS

CRLX101 meets the clinical need for an effective and tolerable topoisomerase I inhibitor and can be safely combined with bevacizumab.

Mutagenic Consequences of Sublethal Cell Death Signaling

Many human cancers exhibit defects in key DNA damage response elements that can render tumors insensitive to the cell death-promoting properties of DNA-damaging therapies. Using agents that directly induce apoptosis by targeting apoptotic components, rather than relying on DNA damage to indirectly stimulate apoptosis of cancer cells, may overcome classical blocks exploited by cancer cells to evade apoptotic cell death. However, there is increasing evidence that cells surviving sublethal exposure to classical apoptotic signaling may recover with newly acquired genomic changes which may have oncogenic potential, and so could theoretically spur the development of subsequent cancers in cured patients. Encouragingly, cells surviving sublethal necroptotic signaling did not acquire mutations, suggesting that necroptosis-inducing anti-cancer drugs may be less likely to trigger therapy-related cancers. We are yet to develop effective direct inducers of other cell death pathways, and as such, data regarding the consequences of cells surviving sublethal stimulation of those pathways are still emerging. This review details the currently known mutagenic consequences of cells surviving different cell death signaling pathways, with implications for potential oncogenic transformation. Understanding the mechanisms of mutagenesis associated (or not) with various cell death pathways will guide us in the development of future therapeutics to minimize therapy-related side effects associated with DNA damage.

Topoisomerase II Poisons: Converting Essential Enzymes into Molecular Scissors

The extensive length, compaction, and interwound nature of DNA, together with its controlled and restricted movement in eukaryotic cells, create a number of topological issues that profoundly affect all of the functions of the genetic material. Topoisomerases are essential enzymes that modulate the topological structure of the double helix, including the regulation of DNA under- and overwinding and the removal of tangles and knots from the genome. Type II topoisomerases alter DNA topology by generating a transient double-stranded break in one DNA segment and allowing another segment to pass through the DNA gate. These enzymes are involved in a number of critical nuclear processes in eukaryotic cells, such as DNA replication, transcription, and recombination, and are required for proper chromosome structure and segregation. However, because type II topoisomerases generate double-stranded breaks in the genetic material, they also are intrinsically dangerous enzymes that have the capacity to fragment the genome. As a result of this dualistic nature, type II topoisomerases are the targets for a number of widely prescribed anticancer drugs. This article will describe the structure and catalytic mechanism of eukaryotic type II topoisomerases and will go on to discuss the actions of topoisomerase II poisons, which are compounds that stabilize DNA breaks generated by the type II enzyme and convert these essential enzymes into "molecular scissors." Topoisomerase II poisons represent a broad range of structural classes and include anticancer drugs, dietary components, and environmental chemicals.

Treatment of progressive multiple sclerosis with high-dose all-trans retinoic acid - no clear evidence of positive disease modifying effects

BACKGROUND

All-trans retinoic acid (ATRA) is an acid derivative of vitamin A which is discussed as a promising candidate to ameliorate the disease course of multiple sclerosis (MS) by immunomodulation or even by promoting regeneration in progressive MS. Here we report a patient who significantly improved for MS related disability following administration of chemotherapy including ATRA for mitoxantrone-related acute promyelocytic leukemia and assess the effect of high-dose ATRA in three additional patients with progressive MS.

METHODS

Patients with progressive MS who had failed previous therapies were treated with high-dose ATRA. Patients underwent clinical and routine laboratory monitoring. Additionally, PBMCs were analyzed by flow cytometry for lymphocyte subsets.

RESULTS

ATRA was well tolerated and no pathological laboratory abnormalities were observed. After initial mild (not statistically significant) improvement of EDSS and mean MSFC z-score, ongoing disease progression was observed. One patient subacutely experienced severe cognitive and motor worsening. Cerebral MRI revealed persistent gadolinium-enhancing lesions. Flow cytometric alterations of peripheral blood naïve, central memory and effector memory CD4 and CD8 T cells, B lymphocytes, plasma cells, memory B cells, plasmablasts and natural killer (NK) cells did not reach statistical significance.

CONCLUSIONS

Stand-alone therapy with ATRA did not ameliorate progressive MS in our limited cohort and we did not observe consistent alterations of T and B cell subsets. Intriguingly, application of ATRA may have caused marked disease exacerbation in one patient.

What's new in the pathogenesis and treatment of therapy-related myeloid neoplasms

Therapy-related myeloid neoplasms (t-MN) include diseases onsetting in patients treated with chemo- and/or radiotherapy for a primary cancer, or an autoimmune disorder. Genomic variants, in particular in familial cancer genes, may play a predisposing role. Recent advances in deep sequencing techniques have shed light on the pathogenesis of t-MN, identifying clonal hematopoiesis of indeterminate potential (CHIP) as a frequent first step in the multi-hit model of t-MN. CHIP is often detectable prior to any cytotoxic treatment, probably setting the fertile genomic background for secondary leukemogenesis. The evolution pattern towards t-MN is then a complex process, shaped by the type of cancer therapy, the aging process, and the individual exposures, that favor additional hits, such as the acquisition of TP53 mutations and unfavorable karyotype abnormalities. The pathogenesis of t-MN differs from MN associated with environmental exposure. Indeed, the genetic aberration patterns of MN developing in atomic bomb survivors show few mutations in classical DNA methylation genes, and a high prevalence of 11q and ATM alterations, together with TP53 mutations. Survival in t-MN is poor. In addition to the biology of t-MN, the patient's previous disease history and the remission status at t-MN diagnosis are significant factors contributing to unfavorable outcome. New drugs active in secondary leukemias include CPX-351, or venetoclax in combination with hypomethylating agents, monoclonal antibodies as magrolimab, or targeted drugs against pathogenic mutations. Allogeneic stem cell transplantation remains the best currently available therapeutic option with curative intent for fit patients with unfavorable genetic profiles.

Human CREBBP acetyltransferase is impaired by etoposide quinone, an oxidative and leukemogenic metabolite of the anticancer drug etoposide through modification of redox-sensitive zinc-finger cysteine residues

Etoposide is an extensively prescribed anticancer drug that, unfortunately, causes therapy-related leukemia. The mechanisms by which etoposide induces secondary hematopoietic malignancies are poorly documented. However, etoposide-related leukemogenesis is known to depend on oxidative metabolites of etoposide, notably etoposide quinone, that can react with protein cysteine residues such as in topoisomerases II. CREBBP is a major histone acetyltransferase that functions mainly as a transcriptional co-activator. This epigenetic enzyme is considered as a tumor suppressor that plays a major role in hematopoiesis. Genetic alterations affecting CREBBP activity are highly common in hematopoietic malignancies. We report here that CREBBP is impaired by etoposide quinone. Molecular and kinetic analyses show that this inhibition occurs through the rapid and covalent (k_inhib = 16.10² M^-1. s^-1) adduction of etoposide quinone with redox sensitive cysteine residues within the RING and PHD Zn²⁺-fingers of CREBBP catalytic core leading to subsequent release of Zn²⁺. In agreement with these findings, experiments conducted in cells and in mice treated with etoposide showed irreversible inhibition of endogenous CREBBP activity and decreased H3K18 and H3K27 acetylation. As shown for topoisomerases II, our work thus suggests that the leukemogenic metabolite etoposide quinone can impair the epigenetic CREBBP acetyltransferase through reaction with redox sensitive cysteine residues.

Protection against chemotherapy- and radiotherapy-induced side effects: A review based on the mechanisms and therapeutic opportunities of phytochemicals

BACKGROUND

Although great achievements have been made in the field of cancer therapy, chemotherapy and radiotherapy remain the mainstay cancer therapeutic modalities. However, they are associated with various side effects, including cardiocytotoxicity, nephrotoxicity, myelosuppression, neurotoxicity, hepatotoxicity, gastrointestinal toxicity, mucositis, and alopecia, which severely affect the quality of life of cancer patients. Plants harbor a great chemical diversity and flexible biological properties that are well-compatible with their use as adjuvant therapy in reducing the side effects of cancer therapy.

PURPOSE

This review aimed to comprehensively summarize the molecular mechanisms by which phytochemicals ameliorate the side effects of cancer therapies and their potential clinical applications.

METHODS

We obtained information from PubMed, Science Direct, Web of Science, and Google scholar, and introduced the molecular mechanisms by which chemotherapeutic drugs and irradiation induce toxic side effects. Accordingly, we summarized the underlying mechanisms of representative phytochemicals in reducing these side effects.

RESULTS

Representative phytochemicals exhibit a great potential in reducing the side effects of chemotherapy and radiotherapy due to their broad range of biological activities, including antioxidation, antimutagenesis, anti-inflammation, myeloprotection, and immunomodulation. However, since a majority of the phytochemicals have only been subjected to preclinical studies, clinical trials are imperative to comprehensively evaluate their therapeutic values.

CONCLUSION

This review highlights that phytochemicals have interesting properties in relieving the side effects of chemotherapy and radiotherapy. Future studies are required to explore the clinical benefits of these phytochemicals for exploitation in chemotherapy and radiotherapy.

Doxorubicin and Aclarubicin: Shuffling Anthracycline Glycans for Improved Anticancer Agents

Anthracycline anticancer drugs doxorubicin and aclarubicin have been used in the clinic for several decades to treat various cancers. Although closely related structures, their molecular mode of action diverges, which is reflected in their biological activity profile. For a better understanding of the structure-function relationship of these drugs, we synthesized ten doxorubicin/aclarubicin hybrids varying in three distinct features: aglycon, glycan, and amine substitution pattern. We continued to evaluate their capacity to induce DNA breaks, histone eviction, and relocated topoisomerase IIα in living cells. Furthermore, we assessed their cytotoxicity in various human tumor cell lines. Our findings underscore that histone eviction alone, rather than DNA breaks, contributes strongly to the overall cytotoxicity of anthracyclines, and structures containing N,N-dimethylamine at the reducing sugar prove that are more cytotoxic than their nonmethylated counterparts. This structural information will support further development of novel anthracycline variants with improved anticancer activity.

New insights into the activities and toxicities of the old anticancer drug doxorubicin

The anthracycline drug doxorubicin is among the most used—and useful—chemotherapeutics. While doxorubicin is highly effective in the treatment of various hematopoietic malignancies and solid tumours, its application is limited by severe adverse effects, including irreversible cardiotoxicity, therapy‐related malignancies and gonadotoxicity. This continues to motivate investigation into the mechanisms of anthracycline activities and toxicities, with the aim to overcome the latter without sacrificing the former. It has long been appreciated that doxorubicin causes DNA double‐strand breaks due to poisoning topoisomerase II. More recently, it became clear that doxorubicin also leads to chromatin damage achieved through eviction of histones from select sites in the genome. Evaluation of these activities in various anthracycline analogues has revealed that chromatin damage makes a major contribution to the efficacy of anthracycline drugs. Furthermore, the DNA‐damaging effect conspires with chromatin damage to cause a number of adverse effects. Structure–activity relationships within the anthracycline family offer opportunities for chemical separation of these activities towards development of effective analogues with limited adverse effects. In this review, we elaborate on our current understanding of the different activities of doxorubicin and their contributions to drug efficacy and side effects. We then offer our perspective on how the activities of this old anticancer drug can be amended in new ways to benefit cancer patients, by providing effective treatment with improved quality of life.

PML-RARA Fusion Transcripts Detectable 8 Months prior to Promyelocytic Blast Crisis in Chronic Myeloid Leukemia

Promyelocytic blast crisis arising from chronic myeloid leukemia (CML) is rare. We present a 40-year-old male who developed promyelocytic blast crisis 17 months after CML diagnosis, confirmed by the presence of the t(15;17) and t(9;22) translocations in the leukemic cells. Preserved nucleic acids from routine BCR-ABL1 testing provided a unique opportunity to evaluate clonal progression over time. Retrospective analysis demonstrated PML-RARA fusion transcripts were first detectable 8 months prior to blast crisis presentation. A review of 21 cases of promyelocytic blasts crisis published in the literature reveals a male predominance with earlier age at onset as compared to females. Interestingly, TKI therapy during chronic phase did not impact the time interval between diagnosis and promyelocytic blast crisis. Treatment with standard acute promyelocytic leukemia regimens provides more favorable outcomes with complete molecular remission. Although rare, it is important to consider a promyelocytic blast crisis when evaluating for transformation of CML due to its effective treatment with specific therapies.

Uncoupling DNA damage from chromatin damage to detoxify doxorubicin

The anthracycline doxorubicin (Doxo) and its analogs daunorubicin (Daun), epirubicin (Epi), and idarubicin (Ida) have been cornerstones of anticancer therapy for nearly five decades. However, their clinical application is limited by severe side effects, especially dose-dependent irreversible cardiotoxicity. Other detrimental side effects of anthracyclines include therapy-related malignancies and infertility. It is unclear whether these side effects are coupled to the chemotherapeutic efficacy. Doxo, Daun, Epi, and Ida execute two cellular activities: DNA damage, causing double-strand breaks (DSBs) following poisoning of topoisomerase II (Topo II), and chromatin damage, mediated through histone eviction at selected sites in the genome. Here we report that anthracycline-induced cardiotoxicity requires the combination of both cellular activities. Topo II poisons with either one of the activities fail to induce cardiotoxicity in mice and human cardiac microtissues, as observed for aclarubicin (Acla) and etoposide (Etop). Further, we show that Doxo can be detoxified by chemically separating these two activities. Anthracycline variants that induce chromatin damage without causing DSBs maintain similar anticancer potency in cell lines, mice, and human acute myeloid leukemia patients, implying that chromatin damage constitutes a major cytotoxic mechanism of anthracyclines. With these anthracyclines abstained from cardiotoxicity and therapy-related tumors, we thus uncoupled the side effects from anticancer efficacy. These results suggest that anthracycline variants acting primarily via chromatin damage may allow prolonged treatment of cancer patients and will improve the quality of life of cancer survivors.

Oral arsenic trioxide, all-trans retinoic acid, and ascorbic acid maintenance after first complete remission in acute promyelocytic leukemia: Long-term results and unique prognostic indicators

BACKGROUND

The role of arsenic trioxide (As₂ O₃ ) in the maintenance of first complete remission (CR1) in acute promyelocytic leukemia (APL) is unclear.

METHODS

A total of 129 consecutive adult patients with APL of all risk categories who achieved CR1 with conventional induction (all-trans retinoic acid [ATRA]/daunorubicin) and consolidation (daunorubicin/cytarabine [induction daunorubicin and consolidation omitted for age ≥70 years]) underwent maintenance comprising ATRA (45 mg/m² /day), oral As₂ O₃ (10 mg/day), and ascorbic acid (1 g/day) (AAA) for 2 weeks every 2 months for 2 years.

RESULTS

Over a 17-year period from August 1, 2002, to July 31, 2019, 63 men and 66 women (median age, 46 years [range, 18-82 years]) received AAA maintenance, which was already completed in 117 patients. At a median follow-up of 100 months (range, 8-215 months), 17 patients (13%) developed first relapse (R1) (hematologic, n = 14; molecular, n = 3) after a median of 19 months (range, 7-96 months) from CR1. Two R1 patients had concomitant central nervous system (CNS) involvement. All patients achieved CR2 with oral As₂ O₃ -based salvage. Five patients had a subsequent relapse and died. Eight patients died of unrelated causes while still in CR1. The 5-year and 10-year rates of relapse-free survival (RFS) were 89% and 85%, respectively. The 5-year and 10-year rates of overall survival (OS) were 94% and 87%, respectively. Multivariate analysis showed that inferior RFS was associated with FLT3-ITD (P = .005) and CNS involvement on presentation (P = .004), and inferior OS was associated with therapy-related APL (P = .03), FLT3-ITD (P = .03), and relapse (P = .03). The safety profile was favorable, with no grade 3/4 organ toxicities.

CONCLUSION

CR1 maintenance with AAA is safe and results in favorable long-term survival in patients with APL.

Characterization of therapy-related acute leukemia in hereditary breast-ovarian carcinoma patients: role of BRCA1 mutation and topoisomerase II-directed therapy

Therapy-related acute leukemias (t-ALs) represent approximately 10-20% of all acute leukemias, are frequently resistant to chemotherapy, and are associated with guarded outcomes. The national comprehensive cancer network data suggest that t-AL cases are diagnosed at increasing rates in breast cancer patients treated with chemotherapeutic agents targeting topoisomerase II. Two cases of BRCA1-mutated ovarian and breast carcinoma who developed therapy-related APL and ALL, respectively, following topoisomerase II-directed therapy were characterized. Genomic characterization of therapy-related acute promyelocytic leukemia (t-APL) revealed a unique RARA intron 2 breakpoint (Chr17: 40347487) at 3'-end of RARA corroborating breakpoint clustering in t-APL following topoisomerase II inhibition. Both cases of this series harbored germline BRCA1 mutations. The germline BRCA1 mutation in patient with t-APL was detected in exon 8 (HGVS nucleotide: c.512dupT). This mutation in t-APL is extremely rare. Interestingly, t-ALL patient in this series had a BRCA1 mutation (HGVS nucleotide: c.68_69delAG; BIC designation: 187delAG) identical to a previously reported case after the treatment of same primary disease. It is unlikely that two breast cancer patients with identical BRCA1 mutation receiving topoisomerase II-targeted agents for the primary disease developed t-AL by chance. This report highlights the development of t-AL in BRAC1-mutated hereditary breast and ovarian cancer patients and warrants further studies on functional consequences of topoisomerase inhibition in this setting.

Association of immunophenotype with expression of topoisomerase II α and β in adult acute myeloid leukemia

Anthracyclines used in the treatment of acute myelogenous leukemia (AML) inhibit the activity of the mammalian topoisomerase II (topo II) isoforms, topo II α and topo IIβ. In 230 patients with non-M3 AML who received frontline ara-C/daunorubicin we determined expression of topo IIα and topo IIβ by RT-PCR and its relationship to immunophenotype (IP) and outcomes. Treatment outcomes were analyzed by logistic or Cox regression. In 211 patients, available for analysis, topo IIα expression was significantly lower than topo IIβ (P < 0.0001). In contrast to topo IIα, topo IIβ was significantly associated with blast percentage in marrow or blood (P = 0.0001), CD7 (P = 0.01), CD14 (P < 0.0001) and CD54 (P < 0.0001). Event free survival was worse for CD56-negative compared to CD56-high (HR = 1.9, 95% CI [1.0-3.5], p = 0.04), and overall survival was worse for CD-15 low as compared to CD15-high (HR = 2.2, 95% CI [1.1-4.2], p = 0.02). Ingenuity pathway analysis indicated topo IIβ and immunophenotype markers in a network associated with cell-to-cell signaling, hematological system development/function and inflammatory response. Topo IIβ expression reflects disease biology of highly proliferative disease and distinct IP but does not appear to be an independent variable influencing outcome in adult AML patients treated with anthracycline-based therapy.

Tuning the surface coating of IONs toward efficient sonochemical tethering and sustained liberation of topoisomerase II poisons

Background

Iron oxide nanoparticles (IONs) have been increasingly utilized in a wide spectrum of biomedical applications. Surface coatings of IONs can bestow a number of exceptional properties, including enhanced stability of IONs, increased loading of drugs or their controlled release.

Methods

Using two-step sonochemical protocol, IONs were surface-coated with polyoxyethylene stearate, polyvinylpyrrolidone or chitosan for a loading of two distinct topo II poisons (doxorubicin and ellipticine). The cytotoxic behavior was tested in vitro against breast cancer (MDA-MB-231) and healthy epithelial cells (HEK-293 and HBL-100). In addition, biocompatibility studies (hemotoxicity, protein corona formation, binding of third complement component) were performed.

Results

Notably, despite surface-coated IONs exhibited only negligible cytotoxicity, upon tethering with topo II poisons, synergistic or additional enhancement of cytotoxicity was found in MDA-MB-231 cells. Pronounced anti-migratory activity, DNA fragmentation, decrease in expression of procaspase-3 and enhancement of p53 expression were further identified upon exposure to surface-coated IONs with tethered doxorubicin and ellipticine. Moreover, surface-coated IONs nanoformulations of topo II poisons exhibited exceptional stability in human plasma with no protein corona and complement 3 binding, and only a mild induction of hemolysis in human red blood cells.

Conclusion

The results imply a high potential of an efficient ultrasound-mediated surface functionalization of IONs as delivery vehicles to improve therapeutic efficiency of topo II poisons.

DNA Damage and Perturbed Topoisomerase IIα as a Target of 1,4-Benzoquinone Toxicity in Murine Fetal Liver Cells

Benzene is a ubiquitous environmental pollutant. Recent studies have shown a link between the development of childhood leukemias and maternal benzene exposure, suggesting that these leukemias may be initiated in utero. Benzene crosses the placental barrier however the mechanisms behind in utero benzene toxicity have not been well elucidated. This study is the first to show that the benzene metabolite, benzoquinone (BQ), perturbs fetal topoisomerase IIα (Topo IIα), an enzyme essential for DNA repair. Using cultured murine CD-1 fetal liver cells, this study shows that Topo IIα activity decreases following 24 hours of exposure to BQ (12.5 and 15.625 µM), with the 12.5 µM confirmed to disrupt the c-kit+Lin-Sca-1-Il7rα- population of cells in culture. Pre-treatment with the antioxidant, N-acetylcysteine did not prevent the inhibtion of Topo IIα by BQ. An increase in Topo IIα-DNA covalent adducts was detected following 24-hour exposures to BQ (12.5 and 50 µM). Interestingly, BQ (12.5 µM) exposure did not significantly increase levels of 4-hydroxynonenal (4-HNE), a marker of oxidative stress after 24 hours. However, increased levels of the double-stranded DNA break marker γH2AX were detected following 24 hours of BQ exposure, confirming that Topo IIα-induced breaks are increased in BQ treated cells. This study shows that fetal Topo IIα is perturbed by BQ and suggests that this protein is a target of benzene and may be implicated with in utero benzene toxicity.

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

Polymorphisms in MDM2 and TP53 Genes and Risk of Developing Therapy-Related Myeloid Neoplasms

One of the most severe complications after successful cancer therapy is the development of therapy-related myeloid neoplasms (t-MN). Constitutional genetic variation is likely to impact on t-MN risk. We aimed to evaluate if polymorphisms in the p53 pathway can be useful for predicting t-MN susceptibility. First, an association study revealed that the Pro variant of the TP53 Arg72Pro polymorphism and the G allele of the MDM2 SNP309 were associated with t-MN risk. The Arg variant of TP53 is more efficient at inducing apoptosis, whereas the Pro variant is a more potent inductor of cell cycle arrest and DNA repair. As regards MDM2 SNP309, the G allele is associated with attenuation of the p53 apoptotic response. Second, to evaluate the biological effect of the TP53 polymorphism, we established Jurkat isogenic cell lines expressing p53Arg or p53Pro. Jurkat p53Arg cells presented higher DNA damage and higher apoptotic potential than p53Pro cells, after treatment with chemotherapy agents. Only p53Pro cells presented t(15;17) translocation and del(5q). We suggest that failure to repair DNA lesions in p53Arg cells would lead them to apoptosis, whereas some p53Pro cells, prone to cell cycle arrest and DNA repair, could undergo misrepair, generating chromosomal abnormalities typical of t-MN.

Coupling the core of the anticancer drug etoposide to an oligonucleotide induces topoisomerase II-mediated cleavage at specific DNA sequences

Etoposide and other topoisomerase II-targeted drugs are important anticancer therapeutics. Unfortunately, the safe usage of these agents is limited by their indiscriminate induction of topoisomerase II-mediated DNA cleavage throughout the genome and by a lack of specificity toward cancer cells. Therefore, as a first step toward constraining the distribution of etoposide-induced DNA cleavage sites and developing sequence-specific topoisomerase II-targeted anticancer agents, we covalently coupled the core of etoposide to oligonucleotides centered on a topoisomerase II cleavage site in the PML gene. The initial sequence used for this 'oligonucleotide-linked topoisomerase inhibitor' (OTI) was identified as part of the translocation breakpoint of a patient with acute promyelocytic leukemia (APL). Subsequent OTI sequences were derived from the observed APL breakpoint between PML and RARA. Results indicate that OTIs can be used to direct the sites of etoposide-induced DNA cleavage mediated by topoisomerase IIα and topoisomerase IIβ. OTIs increased levels of enzyme-mediated cleavage by inhibiting DNA ligation, and cleavage complexes induced by OTIs were as stable as those induced by free etoposide. Finally, OTIs directed against the PML-RARA breakpoint displayed cleavage specificity for oligonucleotides with the translocation sequence over those with sequences matching either parental gene. These studies demonstrate the feasibility of using oligonucleotides to direct topoisomerase II-mediated DNA cleavage to specific sites in the genome.

Therapy-related acute myeloid leukemia following treatment of lymphoid malignancies

Therapy-related acute myeloid leukemia (t-AML) is a heterogeneous entity most frequently related to breast cancer or lymphoproliferative diseases (LD). Population-based studies have reported an increased risk of t-AML after treatment of lymphomas. The aim of this study was to describe the characteristics and outcome of 80 consecutive cases of t-AML following treatment of LD. t-AML accounted for 2.3% of all AML cases, occurred 60 months after LD diagnosis, and were characterized by a high frequency of FAB M6 AML and poor-risk cytogenetic abnormalities. Time to t-AML diagnosis was influenced by patient age, type of LD, and treatment. Among the 48 t-AML patients treated with intensive chemotherapy, median overall survival (OS) was 7.7 months compared to 26.1 months in de novo, 4.2 months in post-myeloproliferative neoplasm, 9.4 months in post-myelodysplastic syndrome, 8.6 months in post-chronic myelomonocytic leukemia AML, 13.4 months in t-AML secondary to the treatment of solid cancer, and 14.7 months in breast cancer only. OS of post-LD t-AML patients was significantly influenced by age, performance status, myelodysplastic syndrome prior to LD/t-AML, and treatment regimen for LD. Thus, t-AML following lymphoid malignancies treatment should be considered as very high-risk secondary AML. New treatment strategies in patients with LD/t-AML are needed urgently.

Mechanisms of receptor tyrosine kinase activation in cancer

Receptor tyrosine kinases (RTKs) play an important role in a variety of cellular processes including growth, motility, differentiation, and metabolism. As such, dysregulation of RTK signaling leads to an assortment of human diseases, most notably, cancers. Recent large-scale genomic studies have revealed the presence of various alterations in the genes encoding RTKs such as EGFR, HER2/ErbB2, and MET, amongst many others. Abnormal RTK activation in human cancers is mediated by four principal mechanisms: gain-of-function mutations, genomic amplification, chromosomal rearrangements, and / or autocrine activation. In this manuscript, we review the processes whereby RTKs are activated under normal physiological conditions and discuss several mechanisms whereby RTKs can be aberrantly activated in human cancers. Understanding of these mechanisms has important implications for selection of anti-cancer therapies.