Contrasting Dynamics in Isoelectronic Anions Formed by Electron Attachment

Cyanogen NCCN and cyanoacetylene HCCCN are isoelectronic molecules, and as such, they have many similar properties. We focus on the bond cleavage in these induced by the dissociative electron attachment. In both molecules, resonant electron attachment produces CN- with very similar energy dependence. We investigate the very different dissociation dynamics, in each of the two molecules, revealed by velocity map imaging of this common fragment. Different dynamics are manifested both in the excess energy partitioning and in the angular distributions of fragments. Based on the comparison with electron energy loss spectra, which provide information about possible parent states of the resonances (both optically allowed and forbidden excited states of the neutral target), we ascribe the observed effect to the distortion of the nuclear frame during the formation of core-excited resonance in cyanoacetylene. The proposed mechanism also explains a puzzling difference in the magnitude of the CN- cross section in the two molecules which has been so far unexplained.

Tmem2 Deficiency Leads to Enamel Hypoplasia and Soft Enamel in Mouse

Teeth consist of 3 mineralized tissues: enamel, dentin, and cementum. Tooth malformation, the most common craniofacial anomaly, arises from complex genetic and environmental factors affecting enamel structure, size, shape, and tooth eruption. Hyaluronic acid (HA), a primary extracellular matrix component, contributes to structural and physiological functions in periodontal tissue. Transmembrane protein 2 (TMEM2), a novel cell surface hyaluronidase, has been shown to play a critical role during embryogenesis. In this study, we demonstrate Tmem2 messenger RNA expression in inner enamel epithelium and presecretory, secretory, and mature ameloblasts. Tmem2 knock-in reporter mice reveal TMEM2 protein localization at the apical and basal ends of secretory ameloblasts. Micro-computed tomography analysis of epithelial-specific Tmem2 conditional knockout (Tmem2-CKO) mice shows a significant reduction in enamel layer thickness and severe enamel deficiency. Enamel matrix protein expression was remarkably downregulated in Tmem2-CKO mice. Scanning electron microscopy of enamel from Tmem2-CKO mice revealed an irregular enamel prism structure, while the microhardness and density of enamel were significantly reduced, indicating impaired ameloblast differentiation and enamel matrix mineralization. Histological evaluation indicated weak adhesion between cells and the basement membrane in Tmem2-CKO mice. The reduced and irregular expressions of vinculin and integrin β1 suggest that Tmem2 deficiency attenuated focal adhesion formation. In addition, abnormal HA accumulation in the ameloblast layer and weak claudin 1 immunoreactivity in Tmem2-CKO mice indicate impaired tight junction gate function. Irregular actin filament assembly was also observed at the apical and basal ends of secretory ameloblasts. Last, we demonstrated that Tmem2-deficient mHAT9d mouse ameloblasts exhibit defective adhesion to HA-containing substrates in vitro. Collectively, our data highlight the importance of TMEM2 in adhesion to HA-rich extracellular matrix, cell-to-cell adhesion, ameloblast differentiation, and enamel matrix mineralization.

Distant Symmetry Control in Electron-Induced Bond Cleavage

We experimentally show that N-H bond cleavage in the pyrrole molecule following resonant electron attachment is allowed and controlled by the motion of the atoms which are not dissociating, namely, of the carbon-attached hydrogen atoms. We use this fact to steer the efficiency of this bond cleavage. In order to interpret the experimental findings, we have developed a method for locating all resonant and virtual states of an electron-molecule system in the complex plane, based on all-electron R-matrix scattering calculations. Mapping these as a function of molecular geometry allows us to separate two contributing dissociation mechanisms: a π* resonance formation inducing strong bending deformations and a nonresonant σ* mechanism originating in a virtual state. The coupling between the two mechanisms is enabled by the out-of-plane motion of the C-H bonds, and we show that it must happen on an ultrafast (few fs) time scale.

Hypoxic human proximal tubular epithelial cells undergo ferroptosis and elicit an NLRP3 inflammasome response in CD1c+ dendritic cells

Inflammasomes are multiprotein platforms responsible for the release of pro-inflammatory cytokines interleukin (IL)-1β and IL-18. Mouse studies have identified inflammasome activation within dendritic cells (DC) as pivotal for driving tubulointerstitial fibrosis and inflammation, the hallmarks of chronic kidney disease (CKD). However, translation of this work to human CKD remains limited. Here, we examined the complex tubular cell death pathways mediating inflammasome activation in human kidney DC and, thus, CKD progression. Ex vivo patient-derived proximal tubular epithelial cells (PTEC) cultured under hypoxic (1% O₂) conditions modelling the CKD microenvironment showed characteristics of ferroptotic cell death, including mitochondrial dysfunction, reductions in the lipid repair enzyme glutathione peroxidase 4 (GPX4) and increases in lipid peroxidation by-product 4-hydroxynonenal (4-HNE) compared with normoxic PTEC. The addition of ferroptosis inhibitor, ferrostatin-1, significantly reduced hypoxic PTEC death. Human CD1c⁺ DC activated in the presence of hypoxic PTEC displayed significantly increased production of inflammasome-dependent cytokines IL-1β and IL-18. Treatment of co-cultures with VX-765 (caspase-1/4 inhibitor) and MCC950 (NLRP3 inflammasome inhibitor) significantly attenuated IL-1β/IL-18 levels, supporting an NLRP3 inflammasome-dependent DC response. In line with these in vitro findings, in situ immunolabelling of human fibrotic kidney tissue revealed a significant accumulation of tubulointerstitial CD1c⁺ DC containing active inflammasome (ASC) specks adjacent to ferroptotic PTEC. These data establish ferroptosis as the primary pattern of PTEC necrosis under the hypoxic conditions of CKD. Moreover, this study identifies NLRP3 inflammasome signalling driven by complex tubulointerstitial PTEC-DC interactions as a key checkpoint for therapeutic targeting in human CKD.

Cep55 overexpression promotes genomic instability and tumorigenesis in mice

High expression of centrosomal protein CEP55 has been correlated with clinico-pathological parameters across multiple human cancers. Despite significant in vitro studies and association of aberrantly overexpressed CEP55 with worse prognosis, its causal role in vivo tumorigenesis remains elusive. Here, using a ubiquitously overexpressing transgenic mouse model, we show that Cep55 overexpression causes spontaneous tumorigenesis and accelerates Trp53^+/− induced tumours in vivo. At the cellular level, using mouse embryonic fibroblasts (MEFs), we demonstrate that Cep55 overexpression induces proliferation advantage by modulating multiple cellular signalling networks including the hyperactivation of the Pi3k/Akt pathway. Notably, Cep55 overexpressing MEFs have a compromised Chk1-dependent S-phase checkpoint, causing increased replication speed and DNA damage, resulting in a prolonged aberrant mitotic division. Importantly, this phenotype was rescued by pharmacological inhibition of Pi3k/Akt or expression of mutant Chk1 (S280A) protein, which is insensitive to regulation by active Akt, in Cep55 overexpressing MEFs. Moreover, we report that Cep55 overexpression causes stabilized microtubules. Collectively, our data demonstrates causative effects of deregulated Cep55 on genome stability and tumorigenesis which have potential implications for tumour initiation and therapy development.

Sinha et al. demonstrate that overexpression of centrosomal protein Cep55 in mice is sufficient to cause a wide-spectrum of cancer via multiple mechanisms including hyperactivation of the Pi3k/Akt pathway, stabilized microtubules and a defective replication checkpoint response. These findings are relevant to human cancers as high CEP55 expression is associated with worse prognosis across multiple cancer types.

Temporary anions of the dielectric gas C3F7CN and their decay channels

We probe the transient anion states (resonances) in the dielectric gas C₄F₇N by the electron energy loss spectroscopy and the dissociative electron attachment spectroscopy. The vibrationally inelastic electron scattering leads to two excitation types. The first is the excitation of specific vibrational modes that are assigned with the help of an infrared spectrum of this molecule and quantum chemistry calculations. In the second type of vibrational excitation, the excess energy is randomized via internal vibrational redistribution in the temporary anion, and the electrons are emitted statistically. The electron attachment proceeds in three different regimes. The first is the formation of the parent C₄F₇N^- anion at energies close to 0 eV. The second is a statistical evaporation of the F-atom, leading to the defluorinated anion C₄F₆N^-. Finally, the third is dissociative electron attachment proceeding via the formation of several resonances and leading to a number of fragments. The present data explain the puzzling recent results of the pulsed-Townsend experiments with this gas.

CX-5461 activates the DNA damage response and demonstrates therapeutic efficacy in high-grade serous ovarian cancer

Acquired resistance to PARP inhibitors (PARPi) is a major challenge for the clinical management of high grade serous ovarian cancer (HGSOC). Here, we demonstrate CX-5461, the first-in-class inhibitor of RNA polymerase I transcription of ribosomal RNA genes (rDNA), induces replication stress and activates the DNA damage response. CX-5461 co-operates with PARPi in exacerbating replication stress and enhances therapeutic efficacy against homologous recombination (HR) DNA repair-deficient HGSOC-patient-derived xenograft (PDX) in vivo. We demonstrate CX-5461 has a different sensitivity spectrum to PARPi involving MRE11-dependent degradation of replication forks. Importantly, CX-5461 exhibits in vivo single agent efficacy in a HGSOC-PDX with reduced sensitivity to PARPi by overcoming replication fork protection. Further, we identify CX-5461-sensitivity gene expression signatures in primary and relapsed HGSOC. We propose CX-5461 is a promising therapy in combination with PARPi in HR-deficient HGSOC and also as a single agent for the treatment of relapsed disease.

Underlying Histopathology Determines Response to Oxidative Stress in Cultured Human Primary Proximal Tubular Epithelial Cells

Proximal tubular epithelial cells (PTEC) are key players in the progression of kidney diseases. PTEC studies to date have primarily used mouse models and transformed human PTEC lines. However, the translatability of these models to human kidney disease has been questioned. In this study, we investigated the phenotypic and functional response of human primary PTEC to oxidative stress, an established driver of kidney disease. Furthermore, we examined the functional contribution of the underlying histopathology of the cortical tissue used to generate our PTEC. We demonstrated that human primary PTEC from both histologically ‘normal’ and ‘diseased’ cortical tissue responded to H₂O₂-induced oxidative stress with significantly elevated mitochondrial superoxide levels, DNA damage, and significantly decreased proliferation. The functional response of ‘normal’ PTEC to oxidative stress mirrored the reported pathogenesis of human kidney disease, with significantly attenuated mitochondrial function and increased cell death. In contrast, ‘diseased’ PTEC were functionally resistant to oxidative stress, with maintenance of mitochondrial function and cell viability. This selective survival of ‘diseased’ PTEC under oxidizing conditions is reminiscent of the in vivo persistence of maladaptive PTEC following kidney injury. We are now exploring the impact that these differential PTEC responses have in the therapeutic targeting of oxidative stress pathways.

Microbiological strategies for enhancing biological nitrogen fixation in nonlegumes

In an agro-ecosystem, industrially produced nitrogenous fertilizers are the principal sources of nitrogen for plant growth; unfortunately these also serve as the leading sources of pollution. Hence, it becomes imperative to find pollution-free methods of providing nitrogen to crop plants. A diverse group of free-living, plant associative and symbiotic prokaryotes are able to perform biological nitrogen fixation (BNF). BNF is a two component process involving the nitrogen fixing diazotrophs and the host plant. Symbiotic nitrogen fixation is most efficient as it can fix nitrogen inside the nodule formed on the roots of the plant; delivering nitrogen directly to the host. However, most of the important crop plants are nonleguminous and are unable to form symbiotic associations. In this context, the plant associative and endophytic diazotrophs assume importance. BNF in nonlegumes can be encouraged either through the transfer of BNF traits from legumes or by elevating the nitrogen fixing capacity of the associative and endophytic diazotrophs. In this review we discuss mainly the microbiological strategies which may be used in nonleguminous crops for enhancement of BNF.

Blockade of PDGFRβ circumvents resistance to MEK-JAK inhibition via intratumoral CD8+ T-cells infiltration in triple-negative breast cancer

BACKGROUND

Despite the increasing progress in targeted and immune based-directed therapies for other solid organ malignancies, currently there is no targeted therapy available for TNBCs. A number of mechanisms have been reported both in pre-clinical and clinical settings that involve inherent, acquired and adaptive resistance to small molecule inhibitors. Here, we demonstrated a novel resistance mechanism in TNBC cells mediated by PDGFRβ in response to JAK2 inhibition.

METHODS

Multiple in vitro (subG1, western blotting, immunofluorescence, RT-PCR, Immunoprecipitation), in vivo and publically available datasets were used.

RESULTS

We showed that TNBC cells exposed to MEK1/2-JAK2 inhibitors exhibit resistant colonies in anchorage-independent growth assays. Moreover, cells treated with various small molecule inhibitors including JAK2 promote PDGFRβ upregulation. Using publically available databases, we showed that patients expressing high PDGFRβ or its ligand PDGFB exhibit poor relapse-free survival upon chemotherapeutic treatment. Mechanistically we found that JAK2 expression controls steady state levels of PDGFRβ. Thus, co-blockade of PDGFRβ with JAK2 and MEK1/2 inhibitors completely eradicated resistant colonies in vitro. We found that triple-combined treatment had a significant impact on CD44⁺/CD24^- stem-cell-like cells. Likewise, we found a significant tumor growth inhibition in vivo through intratumoral CD8⁺ T cells infiltration in a manner that is reversed by anti-CD8 antibody treatment.

CONCLUSION

These findings reveal a novel regulatory role of JAK2-mediated PDGFRβ proteolysis and provide an example of a PDGFRβ-mediated resistance mechanism upon specific target inhibition in TNBC.

Intraluminal brachytherapy boost following external beam radiotherapy with concurrent chemotherapy of oesophagus carcinoma: Results of a prospective observational study

PURPOSE

The main objective of our study is to evaluate response and toxicity profile in patients receiving external beam radiotherapy with concurrent chemotherapy followed by intraluminal brachytherapy boost for a carcinoma of the oesophagus.

MATERIAL AND METHODS

Twenty patients with biopsy-proven carcinoma of the oesophagus received external beam radiotherapy (50Gy in 25 fractions) with concurrent chemotherapy (cisplatin: 40mg/m²). After a gap of two to three weeks, intraluminal brachytherapy (10Gy in two fractions each 1 week apart by a high dose rate ⁶⁰Co source) was given. Response was evaluated at 1 month and at 1 year of completion of treatment. In addition, acute and chronic toxicity was evaluated at 1 month and 6 months of treatment.

RESULTS

Complete response were seen in 80% of patients and partial response in 20% at 1 month. Moreover, there were 65% complete response, 10% local recurrences, 15% patients showed local control with distant metastasis and 10% patients died at 1 year. Grade 1, grade 2 and grade 3 oesophagitis were seen in 10%, 70% and 20% of patients respectively. Stricture was seen in 40% of patients and fistula in 10% of patients. There was no spinal cord, cardiac and nephrotoxicity found.

CONCLUSIONS

With the concept that high tumoricidal dose for adequate tumor control achieved by intraluminal brachytherapy as a mean of dose escalation, while sparing surrounding normal tissue and potentially improving therapeutic ratio, external beam radiotherapy followed by intraluminal brachytherapy could be a better choice for oesophagus carcinoma.

The 2-μm plasmid encoded protein Raf1 regulates both stability and copy number of the plasmid by blocking the formation of the Rep1-Rep2 repressor complex

The 2-μm plasmid of the budding yeast Saccharomyces cerevisiae achieves a high chromosome-like stability with the help of four plasmid-encoded (Rep1, Rep2, Raf1 and Flp) and several host-encoded proteins. Rep1 and Rep2 and the DNA locus STB form the partitioning system ensuring equal segregation of the plasmid. The Flp recombinase and its target sites FRTs form the amplification system which is responsible for the steady state plasmid copy number. In this work we show that the absence of Raf1 can affect both the plasmid stability and the steady sate copy number. We also show that the Rep proteins do bind to the promoter regions of the 2-μm encoded genes, as predicted by earlier models and Raf1 indeed blocks the formation of the Rep1–Rep2 repressor complex not by blocking the transcription of the REP1 and REP2 genes but by physically associating with the Rep proteins and negating their interactions. This explains the role of Raf1 in both the partitioning and the amplification systems as the Rep1–Rep2 complex is believed to modulate both these systems. Based on this study, we have provided, from a systems biology perspective, a model for the mechanism of the 2-μm plasmid maintenance.

Enhanced dependency of KRAS-mutant colorectal cancer cells on RAD51-dependent homologous recombination repair identified from genetic interactions in Saccharomyces cerevisiae

Activating KRAS mutations drive colorectal cancer tumorigenesis and influence response to anti‐EGFR‐targeted therapy. Despite recent advances in understanding Ras signaling biology and the revolution in therapies for melanoma using BRAF inhibitors, no targeted agents have been effective in KRAS‐mutant cancers, mainly due to activation of compensatory pathways. Here, by leveraging the largest synthetic lethal genetic interactome in yeast, we identify that KRAS‐mutated colorectal cancer cells have augmented homologous recombination repair (HRR) signaling. We found that KRAS mutation resulted in slowing and stalling of the replication fork and accumulation of DNA damage. Moreover, we found that KRAS‐mutant HCT116 cells have an increase in MYC‐mediated RAD51 expression with a corresponding increase in RAD51 recruitment to irradiation‐induced DNA double‐strand breaks (DSBs) compared to genetically complemented isogenic cells. MYC depletion using RNA interference significantly reduced IR‐induced RAD51 foci formation and HRR. On the contrary, overexpression of either HA‐tagged wild‐type (WT) MYC or phospho‐mutant S62A increased RAD51 protein levels and hence IR‐induced RAD51 foci. Likewise, depletion of RAD51 selectively induced apoptosis in HCT116‐mutant cells by increasing DSBs. Pharmacological inhibition targeting HRR signaling combined with PARP inhibition selectivity killed KRAS‐mutant cells. Interestingly, these differences were not seen in a second isogenic pair of KRAS WT and mutant cells (DLD‐1), likely due to their nondependency on the KRAS mutation for survival. Our data thus highlight a possible mechanism by which KRAS‐mutant‐dependent cells drive HRR in vitro by upregulating MYC‐RAD51 expression. These data may offer a promising therapeutic vulnerability in colorectal cancer cells harboring otherwise nondruggable KRAS mutations, which warrants further investigation in vivo.

Fentanyl-augmented MRCP

BACKGROUND

Drugs such as secretin and morphine have been used to augment the visualization of magnetic resonance cholangiopancreatography (MRCP). This study investigated the effectiveness of intravenous administration of a synthetic opioid, fentanyl, in improving the MRCP image quality.

METHODS

Thirty consecutive patients with a provisional diagnosis of benign biliary and/or pancreatic disease underwent MRCP. Coronal single-shot fast spin-echo heavily T2-weighted dynamic MRCP images were generated before and at every minute for 10 min after intravenous administration of fentanyl citrate at a dose of 1.0 mug/kg. Pre- and postinjection images were compared and analyzed qualitatively and quantitatively.

RESULTS

Qualitatively, visualization of intrahepatic bile ducts, common bile duct, and main pancreatic duct improved after fentanyl injection in five (16%), 11 (37%), and 19 (63%) patients, respectively. The pancreatobiliary junction and common channel were visualized better after fentanyl injection in eight of the 18 patients (44%). Quantitatively, signal intensity and diameters of the intrahepatic ducts, common bile duct, and main pancreatic duct measured at corresponding points on pre- and postinjection images showed an increase above preinjection values in 28 (93%), 27 (90%), and 21 (70%) and in 18 (60%), 26 (86%), and 22 (73%), respectively, and these changes were highly significant at all sites (p < 0.001).

CONCLUSIONS

Intravenous administration of fentanyl before MRCP improves qualitative and quantitative visualization of the ductal system anatomy that may be of value in clinical diagnosis and management.

Androgenic regulation of steroid hormone receptor mRNAs in the brain of whiptail lizards

Sex and species differences in androgenic regulation of steroid hormone receptor mRNAs were examined in the diencephalon of two species of whiptail lizards: Cnemidophorus inornatus is a sexual species and the direct evolutionary ancestor to Cnemidophorus uniparens, an all-female parthenogenetic species. Lizards were gonadectomized and treated with different doses of either aromatizable testosterone or nonaromatizable dihydrotestosterone. The relative abundances of androgen-, oestrogen-, and progesterone-receptor mRNAs were compared in various nuclei following in situ hybridization with homologous riboprobes. A diversity of patterns in androgenic regulation was observed, with effects differing according to brain region, the steroid-receptor mRNA being considered and, in some cases, between androgens. In the ancestral sexual species, intact males had lower androgen-receptor mRNA abundances than castrated, blank-implanted males in the medial preoptic area. Testosterone significantly decreased androgen-receptor mRNA abundance in the medial preoptic area of castrated males. Males had higher androgen-receptor mRNA levels in the preoptic area than females generally and neither the sexual or parthenogenetic females showed a decrease in androgen-receptor mRNA with androgen treatment. Both testosterone and dihydrotestosterone increased oestrogen-receptor mRNA abundance in the ventromedial hypothalamus of C. inornatus, but no sex differences in this effect were observed. Gonadectomy decreased, whereas androgen treatment increased, progesterone-receptor mRNA abundance in the ventromedial hypothalamus. There was a sex difference in this response to androgen in the sexual species, with males having greater amounts than females in this brain area. The parthenogenetic species exhibited a similar pattern to females of the sexual species, but the levels were higher overall, possibly because Cnemidophorus uniparens is triploid. The periventricular preoptic area showed a different pattern, with testosterone treatment increasing progesterone-receptor mRNA abundance in both sexes of the sexual species and in the parthenogenetic species, while dihydrotestosterone did not. The diversity of patterns in androgen effects indicates that gonadal sex, aromatization of androgen, and perhaps gene dosage all influence the expression of steroid-receptor mRNAs in the lizard brain.