The AsiDNA™ decoy mimicking DSBs protects the normal tissue from radiation toxicity through a DNA-PK/p53/p21-dependent G1/S arrest

AsiDNA™, a cholesterol-coupled oligonucleotide mimicking double-stranded DNA breaks, was developed to sensitize tumour cells to radio- and chemotherapy. This drug acts as a decoy hijacking the DNA damage response. Previous studies have demonstrated that standalone AsiDNA™ administration is well tolerated with no additional adverse effects when combined with chemo- and/or radiotherapy. The lack of normal tissue complication encouraged further examination into the role of AsiDNA™ in normal cells. This research demonstrates the radioprotective properties of AsiDNA™. In vitro, AsiDNA™ induces a DNA-PK/p53/p21-dependent G1/S arrest in normal epithelial cells and fibroblasts that is absent in p53 deficient and proficient tumour cells. This cell cycle arrest improved survival after irradiation only in p53 proficient normal cells. Combined administration of AsiDNA™ with conventional radiotherapy in mouse models of late and early radiation toxicity resulted in decreased onset of lung fibrosis and increased intestinal crypt survival. Similar results were observed following FLASH radiotherapy in standalone or combined with AsiDNA™. Mechanisms comparable to those identified in vitro were detected both in vivo, in the intestine and ex vivo, in precision cut lung slices. Collectively, the results suggest that AsiDNA™ can partially protect healthy tissues from radiation toxicity by triggering a G1/S arrest in normal cells.

An interactive murine single-cell atlas of the lung responses to radiation injury

Radiation Induced Lung Injury (RILI) is one of the main limiting factors of thorax irradiation, which can induce acute pneumonitis as well as pulmonary fibrosis, the latter being a life-threatening condition. The order of cellular and molecular events in the progression towards fibrosis is key to the physiopathogenesis of the disease, yet their coordination in space and time remains largely unexplored. Here, we present an interactive murine single cell atlas of the lung response to irradiation, generated from C57BL6/J female mice. This tool opens the door for exploration of the spatio-temporal dynamics of the mechanisms that lead to radiation-induced pulmonary fibrosis. It depicts with unprecedented detail cell type-specific radiation-induced responses associated with either lung regeneration or the failure thereof. A better understanding of the mechanisms leading to lung fibrosis will help finding new therapeutic options that could improve patients' quality of life.

Cytidine deaminase deficiency in mice enhances genetic instability but limits the number of chemically induced colon tumors

Cytidine deaminase (CDA) catalyzes the deamination of cytidine (C) and deoxycytidine (dC) to uridine and deoxyuridine, respectively. We recently showed that CDA deficiency leads to genomic instability, a hallmark of cancers. We therefore investigated whether constitutive CDA inactivation conferred a predisposition to cancer development. We developed a novel mouse model of Cda deficiency by generating Cda-knockout mice. Cda^+/+ and Cda^-/- mice did not differ in lifetime phenotypic or behavioral characteristics, or in the frequency or type of spontaneous cancers. However, the frequency of chemically induced tumors in the colon was significantly lower in Cda^-/- mice. An analysis of primary kidney cells from Cda^-/- mice revealed an excess of C and dC associated with significantly higher frequencies of sister chromatid exchange and ultrafine anaphase bridges and lower Parp-1 activity than in Cda^+/+ cells. Our results suggest that, despite inducing genetic instability, an absence of Cda limits the number of chemically induced tumors. These results raise questions about whether a decrease in basal Parp-1 activity can protect against inflammation-driven tumorigenesis; we discuss our findings in light of published data for the Parp-1-deficient mouse model.

Distinct roles of α- and β-tubulin polyglutamylation in controlling axonal transport and in neurodegeneration

Tubulin polyglutamylation is a post-translational modification of the microtubule cytoskeleton, which is generated by a variety of enzymes with different specificities. The "tubulin code" hypothesis predicts that modifications generated by specific enzymes selectively control microtubule functions. Our recent finding that excessive accumulation of polyglutamylation in neurons causes their degeneration and perturbs axonal transport provides an opportunity for testing this hypothesis. By developing novel mouse models and a new glutamylation-specific antibody, we demonstrate here that the glutamylases TTLL1 and TTLL7 generate unique and distinct glutamylation patterns on neuronal microtubules. We find that under physiological conditions, TTLL1 polyglutamylates α-tubulin, while TTLL7 modifies β-tubulin. TTLL1, but not TTLL7, catalyses the excessive hyperglutamylation found in mice lacking the deglutamylase CCP1. Consequently, deletion of TTLL1, but not of TTLL7, prevents degeneration of Purkinje cells and of myelinated axons in peripheral nerves in these mice. Moreover, loss of TTLL1 leads to increased mitochondria motility in neurons, while loss of TTLL7 has no such effect. By revealing how specific patterns of tubulin glutamylation, generated by distinct enzymes, translate into specific physiological and pathological readouts, we demonstrate the relevance of the tubulin code for homeostasis.

BRCAness, SLFN11, and RB1 loss predict response to topoisomerase I inhibitors in triple-negative breast cancers

Topoisomerase I (TOP1) inhibitors trap TOP1 cleavage complexes resulting in DNA double-strand breaks (DSBs) during replication, which are repaired by homologous recombination (HR). Triple-negative breast cancer (TNBC) could be eligible for TOP1 inhibitors given the considerable proportion of tumors with a defect in HR-mediated repair (BRCAness). The TOP1 inhibitor irinotecan was tested in 40 patient-derived xenografts (PDXs) of TNBC. BRCAness was determined with a single-nucleotide polymorphism (SNP) assay, and expression of Schlafen family member 11 (SLFN11) and retinoblastoma transcriptional corepressor 1 (RB1) was evaluated by real-time polymerase chain reaction (RT-PCR) and immunohistochemistry analyses. In addition, the combination of irinotecan and the ataxia telangiectasia and Rad3-related protein (ATR) inhibitor VE-822 was tested in SLFN11-negative PDXs, and two clinical non-camptothecin TOP1 inhibitors (LMP400 and LMP776) were tested. Thirty-eight percent of the TNBC models responded to irinotecan. BRCAness combined with high SLFN11 expression and RB1 loss identified highly sensitive tumors, consistent with the notion that deficiencies in cell cycle checkpoints and DNA repair result in high sensitivity to TOP1 inhibitors. Treatment by the ATR inhibitor VE-822 increased sensitivity to irinotecan in SLFN11-negative PDXs and abolished irinotecan-induced phosphorylation of checkpoint kinase 1 (CHK1). LMP400 (indotecan) and LMP776 (indimitecan) showed high antitumor activity in BRCA1-mutated or BRCAness-positive PDXs. Last, low SLFN11 expression was associated with poor survival in 250 patients with TNBC treated with anthracycline-based chemotherapy. In conclusion, a substantial proportion of TNBC respond to irinotecan. BRCAness, high SLFN11 expression, and RB1 loss are highly predictive of response to irinotecan and the clinical indenoisoquinoline TOP1 inhibitors.

Tubulin glycylation controls axonemal dynein activity, flagellar beat, and male fertility

Posttranslational modifications of the microtubule cytoskeleton have emerged as key regulators of cellular functions, and their perturbations have been linked to a growing number of human pathologies. Tubulin glycylation modifies microtubules specifically in cilia and flagella, but its functional and mechanistic roles remain unclear. In this study, we generated a mouse model entirely lacking tubulin glycylation. Male mice were subfertile owing to aberrant beat patterns of their sperm flagella, which impeded the straight swimming of sperm cells. Using cryo-electron tomography, we showed that lack of glycylation caused abnormal conformations of the dynein arms within sperm axonemes, providing the structural basis for the observed dysfunction. Our findings reveal the importance of microtubule glycylation for controlled flagellar beating, directional sperm swimming, and male fertility.

FLASH Irradiation Spares Lung Progenitor Cells and Limits the Incidence of Radio-induced Senescence

PURPOSE

One of the main limitations to anticancer radiotherapy lies in irreversible damage to healthy tissues located within the radiation field. "FLASH" irradiation at very high dose-rate is a new treatment modality that has been reported to specifically spare normal tissue from late radiation-induced toxicity in animal models and therefore could be a promising strategy to reduce treatment toxicity.

EXPERIMENTAL DESIGN

Lung responses to FLASH irradiation were investigated by qPCR, single-cell RNA sequencing (sc-RNA-Seq), and histologic methods during the acute wound healing phase as well as at late stages using C57BL/6J wild-type and Terc^-/- mice exposed to bilateral thorax irradiation as well as human lung cells grown in vitro.

RESULTS

In vitro studies gave evidence of a reduced level of DNA damage and induced lethality at the advantage of FLASH. In mouse lung, sc-RNA-seq and the monitoring of proliferating cells revealed that FLASH minimized the induction of proinflammatory genes and reduced the proliferation of progenitor cells after injury. At late stages, FLASH-irradiated lungs presented less persistent DNA damage and senescent cells than after CONV exposure, suggesting a higher potential for lung regeneration with FLASH. Consistent with this hypothesis, the beneficial effect of FLASH was lost in Terc^-/- mice harboring critically short telomeres and lack of telomerase activity.

CONCLUSIONS

The results suggest that, compared with conventional radiotherapy, FLASH minimizes DNA damage in normal cells, spares lung progenitor cells from excessive damage, and reduces the risk of replicative senescence.

Low retinal toxicity of intravitreal carboplatin associated with good retinal tumour control in transgenic murine retinoblastoma

BACKGROUND

Retinoblastoma is a rare intraocular malignancy in children. Current treatments have many adverse effects. New therapeutic approaches like intravitreal injections of chemotherapies are currently being developed but their toxicities need to be evaluated on animal models. This study compares the efficacy and toxicity of intravitreal melphalan, topotecan and carboplatin, alone or in combination (sequential administration), in the LHBetaTag retinoblastoma mice.

METHODS

Mice were divided into nine groups: control, carboplatin 1.5 and 4 μg, melphalan 0.1 and 1 μg, topotecan 0.1 and 1 μg, carboplatin 4 μg/topotecan 0.1 μg and melphalan 1 μg/topotecan 0.1 μg. The follow-up was performed using fundus imaging and optical coherence tomography combined with histopathological analysis. Absence of tumour and presence of calcified tumours were the criteria for therapeutic response assessment. Ocular complications were assessed after four weekly injections. Retinal toxicity was defined by the decrease of retinal thickness and of the number of retinal layers.

RESULTS

Topotecan was inactive on retinal tumours. Melphalan (1 μg) led to a complete tumour control in 91.7% of eyes. Carboplatin strongly decreased the tumour burden (85.7-93.8% of eyes without retinal tumour). The intravitreal injection itself led to ocular complications (25% of media opacities and 45.7% of retinal detachment). Only melphalan at 1 μg showed a strong retinal toxicity. The two combinations showed a good efficacy in reducing the number of eyes with retinal tumours with a reduced retinal toxicity.

CONCLUSIONS

This preclinical study suggests that intravitreal injection of carboplatin has a low toxicity and could be evaluated in clinical practice to treat patients suffering from retinoblastoma.

An autocrine ActivinB mechanism drives TGFβ/Activin signaling in Group 3 medulloblastoma

Medulloblastoma (MB) is a pediatric tumor of the cerebellum divided into four groups. Group 3 is of bad prognosis and remains poorly characterized. While the current treatment involving surgery, radiotherapy, and chemotherapy often fails, no alternative therapy is yet available. Few recurrent genomic alterations that can be therapeutically targeted have been identified. Amplifications of receptors of the TGFβ/Activin pathway occur at very low frequency in Group 3 MB. However, neither their functional relevance nor activation of the downstream signaling pathway has been studied. We showed that this pathway is activated in Group 3 MB with some samples showing a very strong activation. Beside genetic alterations, we demonstrated that an ActivinB autocrine stimulation is responsible for pathway activation in a subset of Group 3 MB characterized by high PMEPA1 levels. Importantly, Galunisertib, a kinase inhibitor of the cognate receptors currently tested in clinical trials for Glioblastoma patients, showed efficacy on orthotopically grafted MB‐PDX. Our data demonstrate that the TGFβ/Activin pathway is active in a subset of Group 3 MB and can be therapeutically targeted.

Loss of the deglutamylase CCP5 perturbs multiple steps of spermatogenesis and leads to male infertility

Sperm cells are highly specialized mammalian cells, and their biogenesis requires unique intracellular structures. Perturbations of spermatogenesis often lead to male infertility. Here we assess the role of a posttranslational modification of tubulin, glutamylation, in spermatogenesis. We show that mice lacking the tubulin deglutamylase CCP5 do not form functional sperm. Spermatids accumulate polyglutamylated tubulin, accompanied by the occurrence of disorganized microtubule arrays, in particular the sperm manchette, fail to re-arrange their intracellular space and accumulate organelles and cytosol, while nuclei condense normally. Strikingly, spermatids lacking CCP5 show supernumerary centrioles, suggesting that glutamylation could control centriole duplication. We show that most of these observed defects are also present in mice in which CCP5 is deleted only in the male germ line, strongly suggesting that they are germ-cell-autonomous. Our findings reveal that polyglutamylation is, beyond its known importance for sperm flagella, and essential regulator of several microtubule-based functions during spermatogenesis. This makes enzymes involved in glutamylation prime candidates for genes involved in male sterility.

Excessive tubulin polyglutamylation causes neurodegeneration and perturbs neuronal transport

Posttranslational modifications of tubulin are emerging regulators of microtubule functions. We have shown earlier that upregulated polyglutamylation is linked to rapid degeneration of Purkinje cells in mice with a mutation in the deglutamylating enzyme CCP1. How polyglutamylation leads to degeneration, whether it affects multiple neuron types, or which physiological processes it regulates in healthy neurons has remained unknown. Here, we demonstrate that excessive polyglutamylation induces neurodegeneration in a cell-autonomous manner and can occur in many parts of the central nervous system. Degeneration of selected neurons in CCP1-deficient mice can be fully rescued by simultaneous knockout of the counteracting polyglutamylase TTLL1. Excessive polyglutamylation reduces the efficiency of neuronal transport in cultured hippocampal neurons, suggesting that impaired cargo transport plays an important role in the observed degenerative phenotypes. We thus establish polyglutamylation as a cell-autonomous mechanism for neurodegeneration that might be therapeutically accessible through manipulation of the enzymes that control this posttranslational modification.

Aberrant ERBB4-SRC Signaling as a Hallmark of Group 4 Medulloblastoma Revealed by Integrative Phosphoproteomic Profiling

The current consensus recognizes four main medulloblastoma subgroups (wingless, Sonic hedgehog, group 3 and group 4). While medulloblastoma subgroups have been characterized extensively at the (epi-)genomic and transcriptomic levels, the proteome and phosphoproteome landscape remain to be comprehensively elucidated. Using quantitative (phospho)-proteomics in primary human medulloblastomas, we unravel distinct posttranscriptional regulation leading to highly divergent oncogenic signaling and kinase activity profiles in groups 3 and 4 medulloblastomas. Specifically, proteomic and phosphoproteomic analyses identify aberrant ERBB4-SRC signaling in group 4. Hence, enforced expression of an activated SRC combined with p53 inactivation induces murine tumors that resemble group 4 medulloblastoma. Therefore, our integrative proteogenomics approach unveils an oncogenic pathway and potential therapeutic vulnerability in the most common medulloblastoma subgroup.

NRL and CRX Define Photoreceptor Identity and Reveal Subgroup-Specific Dependencies in Medulloblastoma

Cancer cells often express differentiation programs unrelated to their tissue of origin, although the contribution of these aberrant phenotypes to malignancy is poorly understood. An aggressive subgroup of medulloblastoma, a malignant pediatric brain tumor of the cerebellum, expresses a photoreceptor differentiation program normally expressed in the retina. We establish that two photoreceptor-specific transcription factors, NRL and CRX, are master regulators of this program and are required for tumor maintenance in this subgroup. Beyond photoreceptor lineage genes, we identify BCL-XL as a key transcriptional target of NRL and provide evidence substantiating anti-BCL therapy as a rational treatment opportunity for select MB patients. Our results highlight the utility of studying aberrant differentiation programs in cancer and their potential as selective therapeutic vulnerabilities.

Changes in the NFκB and E-cadherin expression are associated to diabetic nephropathy inPsammomys obesus

Diabetes mellitus is a major leading cause of end-stage renal failure, characterized by kidney inflammation and glomerular dysfunction, in worldwide. Kidney inflammation is associated to modifications in the expression levels of pro-inflammatory molecules, such as nuclear factor-κB (NFκB) and adhesion molecules, such as E-cadherin, leading to glomerular dysfunction. However, the relationships between these two processes in human diabetic nephropathy remain an open question. Since Psammomys obesus is an ideal animal model to study diabetes mellitus temporal evolution, we have used this model to study the correlation between kidney structural changes and modification on the expression levels of NFκB and E-cadherin over time. We have demonstrated that, after induction of diabetes metillus with a high energy diet (HED), P. obesus develops the characteristic symptoms of human disease. In detail, at the third month nuclear factor NFκB is expressed in the kidney of diabetic P. obesus and structural renal changes, such as mesangial expansion or interstitial fibrosis, are detectable; at 6 months, thickening of glomerular basement membrane, glomerular sclerosis, and tubular atrophy occurs; at 9 months, symptoms of the final stages of the disease, such as down expression of E-cadherin, happens. As a result of these observations we proposed that NFκB activation and E-cadherin down-expression are interlinked on diabetic kidney disease (DKD).

Unraveling the Role of Huntingtin in Breast Cancer Metastasis

BACKGROUND

Huntingtin (HTT) is mutated in Huntington's disease but is ubiquitously expressed, and mutant HTT influences cancer progression. We investigated wild-type HTT function during breast cancer.

METHODS

We analyzed HTT and ZO1 expression as well as the HTT phosphoserine 421-activated form (S421-P-HTT) in human breast cancer tissues by quantitative reverse transcription polymerase chain reaction and immunohistochemistry. We performed in vitro migration and invasion assays as well as in vivo tail vein injections of the metastatic 4T1 cells in BALB/c mice (n = 11 per group). We analyzed tumor progression in knock-in mice with modified S421 crossed with the MMTV-PyVT mammary cancer model (at least n = 12 per group). Data were analyzed with unpaired t tests, analysis of variance, Pearson or Spearman correlation, and Mann Whitney or Kruskal-Wallis tests. All statistical tests were two-sided.

RESULTS

Levels of HTT and of S421-P-HTT are abnormally low in poorly differentiated and metastatic human breast cancers. HTT expression is downregulated in invasive compared with in situ carcinoma (P < .001). In BALB/c mice, silencing of HTT promotes lung colonization by a metastatic mammary cancer cell line (P = .005) and S421-unphosphorylatable-HTT accelerates cancer progression. HTT interacts with ZO1 and regulates both its expression and its localization to tight junctions. In human breast tumors, the patterns of HTT and ZO1 expression are similar (Pearson correlation coefficient = 0.66, P < .001).

CONCLUSIONS

HTT may inhibit breast tumor dissemination through maintenance of ZO1 at tight junctions. Downregulation of HTT transcript and protein levels is a prognostic factor for poor prognosis and metastasis development.

The calcineurin/NFAT pathway is activated in diagnostic breast cancer cases and is essential to survival and metastasis of mammary cancer cells

Nuclear factor of activated T cells 1 (NFAT1) expression has been associated with increased migratory/invasive properties of mammary tumor-derived cell lines in vitro. It is unknown, however, if NFAT activation actually occurs in breast cancer cases and whether the calcineurin/NFAT pathway is important to mammary tumorigenesis. Using a cohort of 321 diagnostic cases of the major subgroup of breast cancer, we found Cn/NFAT pathway activated in ER⁻PR⁻HER2⁻ triple-negative breast cancer subtype, whereas its prevalence is less in other subgroups. Using a small hairpin RNA-based gene expression silencing approach in murine mammary tumor cell line (4T1), we show that not only NFAT1 but also NFAT2 and their upstream activator Cn are essential to the migratory and invasive properties of mammary tumor cells. We also demonstrate that Cn, NFAT1 and NFAT2 are essential to the tumorigenic and metastatic properties of these cells in mice, a phenotype which coincides with increased apoptosis in vivo. Finally, global gene expression analyses identified several NFAT-deregulated genes, many of them being previously associated with mammary tumorigenesis. In particular, we identified the gene encoding a disintegrin and metalloproteinase with thrombonspondin motifs 1, as being a potential direct target of NFAT1. Thus, our results show that the Cn/NFAT pathway is activated in diagnostic cases of breast cancers and is essential to the tumorigenic and metastatic potential of mammary tumor cell line. These results suggest that pharmacological inhibition of the Cn/NFAT pathway at different levels could be of therapeutical interest for breast cancer patients.