ABSTRACT
This work examines the relationships between the properties (flux ratios, full width at half-maximum velocities) of the O i λλ6300, 6364, Ca ii λλ7291, 7323, and the Ca ii near-infrared ...triplet, emission lines of a large sample of core-collapse supernovas (SNe) and Ca-rich transients (509 spectra of 86 transients, of which 10 transients are Ca-rich events). Line-flux ratios as a function of time were investigated with differences identified between the transient classes, in particular the Type II SNe were found to have distinct line-flux ratios compared to stripped-envelope (SE) SNe. No correlation was found between the Ca ii/O i flux ratios of SE-SNe and their ejecta masses and kinetic energies (as measured from light-curve modelling), suggesting that there may be a contribution from an additional power source in more luminous SE-SNe. We found that the mean characteristic width of the Ca ii emission line is less than the O i emission line for all SN types, indicating that the Ca ii emission typically originates from deeper in the ejecta than O i. This is in some tension with standard models for emission in Type II SNe. The emission line properties of Type II SNe were also compared to theoretical models and found to favour lower mass tracks (MZAMS< 15 M⊙), with no evidence found for significant mixing of 56Ni into the H envelope nor Ca mixed into the O shell. The flux ratios of some superluminous SNe were found to be similar to those of SE-SNe when scaling to account for their longer rise times was applied (although we caution the sample size is small).
ABSTRACT Multiple explosion mechanisms have been proposed to explain type Ia supernovae (SNe Ia). Empirical modelling tools have also been developed that allow for fast, customized modelling of ...individual SNe and direct comparisons between observations and explosion model predictions. Such tools have provided useful insights, but the subjective nature with which empirical modelling is performed makes it difficult to obtain robust constraints on the explosion physics or expand studies to large populations of objects. Machine learning accelerated tools have therefore begun to gain traction. In this paper, we present riddler, a framework for automated fitting of SNe Ia spectral sequences up to shortly after maximum light. We train a series of neural networks on realistic ejecta profiles predicted by the W7 and N100 explosion models to emulate full radiative transfer simulations and apply nested sampling to determine the best-fitting model parameters for multiple spectra of a given SN simultaneously. We show that riddler is able to accurately recover the parameters of input spectra and use it to fit observations of two well-studied SNe Ia. We also investigate the impact of different weighting schemes when performing quantitative spectral fitting and show that best-fitting models and parameters are highly dependent on the assumed weighting schemes and priors. As spectroscopic samples of SNe Ia continue to grow, automated spectral fitting tools such as riddler will become increasingly important to maximise the physical constraints that can be gained in a quantitative and consistent manner.
Multiple explosion mechanisms have been proposed to explain type Ia supernovae (SNe Ia). Empirical modelling tools have also been developed that allow for fast, customised modelling of individual SNe ...and direct comparisons between observations and explosion model predictions. Such tools have provided useful insights, but the subjective nature with which empirical modelling is performed makes it difficult to obtain robust constraints on the explosion physics or expand studies to large populations of objects. Machine learning accelerated tools have therefore begun to gain traction. In this paper, we present riddler, a framework for automated fitting of SNe Ia spectral sequences up to shortly after maximum light. We train a series of neural networks on realistic ejecta profiles predicted by the W7 and N100 explosion models to emulate full radiative transfer simulations and apply nested sampling to determine the best-fitting model parameters for multiple spectra of a given SN simultaneously. We show that riddler is able to accurately recover the parameters of input spectra and use it to fit observations of two well-studied SNe Ia. We also investigate the impact of different weighting schemes when performing quantitative spectral fitting and show that best-fitting models and parameters are highly dependent on the assumed weighting schemes and priors. As spectroscopic samples of SNe Ia continue to grow, automated spectral fitting tools such as riddler will become increasingly important to maximise the physical constraints that can be gained in a quantitative and consistent manner.
Both KRAS and EGFR are essential mediators of pancreatic cancer development and interact with Argonaute 2 (AGO2) to perturb its function. Here, in a mouse model of mutant KRAS-driven pancreatic ...cancer, loss of AGO2 allows precursor lesion (PanIN) formation yet prevents progression to pancreatic ductal adenocarcinoma (PDAC). Precursor lesions with AGO2 ablation undergo oncogene-induced senescence with altered microRNA expression and EGFR/RAS signaling, bypassed by loss of p53. In mouse and human pancreatic tissues, PDAC progression is associated with increased plasma membrane localization of RAS/AGO2. Furthermore, phosphorylation of AGO2
disrupts both the wild-type and oncogenic KRAS-AGO2 interaction, albeit under different conditions. ARS-1620 (G12C-specific inhibitor) disrupts the KRAS
-AGO2 interaction, suggesting that the interaction is targetable. Altogether, our study supports a biphasic model of pancreatic cancer development: an AGO2-independent early phase of PanIN formation reliant on EGFR-RAS signaling, and an AGO2-dependent phase wherein the mutant KRAS-AGO2 interaction is critical for PDAC progression.
The coexpression of the MLL partial tandem duplication (PTD) and the FLT3 internal tandem duplication (ITD) mutations associate with a poor outcome in cytogenetically normal acute myeloid leukemia ...(AML). In mice, a double knock-in (dKI) of Mll(PTD/wt) and Flt3(ITD/wt) mutations induces spontaneous AML with an increase in DNA methyltransferases (Dnmt1, 3a, and 3b) and global DNA methylation index, thereby recapitulating its human AML counterpart. We determined that a regulator of Dnmts, miR-29b, is downregulated in bone marrow of dKI AML mice. Bortezomib exerted a dose-dependent increase in miR-29b expression in AML blasts ex vivo, followed by decreased Dnmts, reduced proliferation, and increased apoptosis. In vivo, bortezomib was not active against dKI AML, yet liposomal-encapsulated bortezomib, as a single agent, reversed downregulation of miR-29b in vivo and induced a long-term (90-day) disease-free remission in 80% of dKI AML mice that exhibited high leukemic burden at the start of therapy, yet showed no signs of relapse at autopsy. Taken together, these data support that liposomal bortezomib, as a single agent, eradicates Mll(PTD/wt):Flt3(ITD/wt) AML in mouse and may represent a powerful and potentially curative approach to high-risk human disease.
Abstract
The RAS gene family is among the most commonly mutated genes within cancer, and while much research has elucidated the major downstream pathways, including MAPK and PI3K, little progress has ...been made in successfully targeting mutant RAS in cancer. We recently identified an interaction between the N terminal domain of Argonaute 2 (AGO2), a core component of RNA-induced silencing complex (RISC), and the Switch II domain of KRAS. Furthermore, this interaction was found in all cell lines tested, expressing either wild-type (WT) or mutant KRAS. We found that stable knockdown of AGO2 in KRAS dependent cell lines lead to a decrease in KRAS protein expression with a subsequent decrease in cellular proliferation. Conversely, the overexpression of AGO2 in these cells lead to both an increase in KRAS expression and oncogenesis. In addition, this interaction inhibits the RNAi function of AGO2 by preventing microRNA unwinding in the presence of oncogenic KRAS compared to WT-KRAS. Despite a clear association between mutant KRAS and AGO2 mediating increased KRAS mediated oncogenesis, the precise function of this interaction remains unclear in normal physiology. In order to better assess the endogenous function of the KRAS-AGO2 interaction, we analyzed two mouse embryonic fibroblast cell lines (NIH 3T3 and MEF) with complete knockout of AGO2. Utilizing a Raf-1 RAS binding domain (RBD) pulldown method, we assessed activated WT-RAS levels in AGO2 null NIH 3T3 and MEF cells. We found that knockout of AGO2 lead to an increase in WT RAS-GTP activation compared to normal control cells. Immunoblot analysis also indicates that AGO2 null fibroblasts lead to increase in RAS downstream signaling through the MAPK/ERK and PI3K/AKT pathways. Furthermore, rescue of AGO2 knockout using full length mouse AGO2 decreased wild type RAS activation and its downstream signaling. Taken together, these observations suggest that the AGO2 interaction may suppress WT-KRAS activation, leading to maintenance of RAS-GDP levels. Using RNA-seq, proteome and microRNA analysis, we have begun to identify the pathways that may be involved in RAS activation in AGO2 null cells. Early analyses indicate that AGO2 controls WT-KRAS levels and activity through multiple mechanisms, laying the foundation for a better understanding of the RAS-AGO2 interaction in normal physiology.
Citation Format: Ronald F. Siebenaler, Sunita Shankar, Vijaya L. Dommeti, Malay Mody, Arul Chinnaiyan. Argonaute 2 controls RAS activation in mouse embryonic fibroblasts abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1362. doi:10.1158/1538-7445.AM2017-1362
Abstract
The RAS gene family is among the most commonly mutated genes within cancer. While much research has elucidated its major functions and downstream pathways, little progress has been made in ...successfully targeting RAS mutations. We recently identified Argonaute 2 (AGO2) of the RNA-induced silencing complex (RISC) as a novel partner of the Switch II domain of KRAS. We have found that stable knockdown of AGO2 in KRAS-dependent cell lines lead to a decrease in KRAS protein expression with a subsequent decrease in cellular proliferation. In addition, we observed a decrease in microRNA unwinding in the presence of mutant KRAS, suggesting this interaction inhibits the endogenous RNAi function of AGO2. Despite this clear connection between KRAS and AGO2 in KRAS mediated oncogenesis, the precise function of this interaction remains unclear in both normal and cancer biology.
In order to identify endogenous regulators of AGO2-RAS, we investigated the ability of EGFR signaling to modulate the AGO2-RAS interaction. We established two mouse embryonic fibroblast cell lines (NIH-3T3 and MEF) with complete knockout of AGO2. When compared to normal control cells, we found that knockout of AGO2 resulted in an increase in WT RAS-GTP activation levels, phosphorylation of Y1068-EGFR, and MAPK/ERK and PI3K/AKT signaling. Rescue of AGO2 knockout resulted in a return to normal levels of active RAS-GTP, pEGFR, and downstream signaling.
Recent studies have described EGFR phosphorylation of AGO2 under hypoxic cell conditions, resulting in the inhibition of AGO2 association with RISC members. In order to better characterize the relationship between EGFR-AGO2-RAS, we found that overnight serum starvation followed by stimulation with EGF led to a decrease in AGO2-RAS co-IP in WT KRAS cells. Blocking AGO2 phosphorylation with a Y393F mutant of AGO2 prevented AGO2-RAS dissociation following EGFR stimulation. While WT KRAS cell lines displayed regulation of AGO2-RAS via EGFR, the phosphorylation of AGO2Y393 was unable to disrupt the interaction of AGO2 with mutant KRAS following stimulation with EGF. Together these results suggest a unique EGFR-AGO2-RAS signaling axis, and its dysregulation by mutant KRAS could increase oncogenic growth through promotion of AGO2-RAS interaction in cancer.
Citation Format: Ronald F. Siebenaler, Sunita Shankar, Jean C. Tien, Vijaya L. Dommeti, Malay Mody, Chandan Kumar-Sinha, Arul M. Chinnaiyan. Regulation of AGO2-KRAS interaction through epidermal growth factor receptor abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4370.
Abstract Objective In this secondary analysis from the Clinical Outcomes in MEasurement-based Treatment trial (COMET), we evaluated whether providing primary care physicians with patient-reported ...feedback regarding depression severity affected pharmacological treatment patterns. Method Intervention-arm physicians received their patients' 9-item Patient Health Questionnaire scores monthly. Odds of having no change in antidepressant treatment during the 6-month study period were calculated. Relationships between depression symptom status (partial or nonresponse) at month 3 and treatment changes in months 3 through 6 were assessed. Results Among 503 intervention and 412 usual care (UC) patients with major depressive disorder, most received antidepressant monotherapy at baseline (79.4% UC vs. 88.4% intervention; P =.047). Few switched their baseline antidepressant (17.4%), increased their dose (12.4%) or augmented with a second medication (2%). Odds of having no change in antidepressant therapy did not differ significantly between study arms (odds ratio 1.21; 95% confidence interval 0.78–1.88; P =.392). Few month 3 partial or nonresponders had a regimen change over the following 3 months; the study arms did not differ significantly (partial responders: 4.1% UC vs. 7.7% intervention; P =.429; nonresponders: 14.6% UC vs. 15.9% intervention; P =.888). Conclusions Among depressed patients treated in primary care, little active management was observed. The lack of treatment modification for the majority of partial and nonresponders was notable.
Abstract
The RAS gene family is among the most commonly mutated genes within cancer, but little progress has been made in successfully targeting RAS mutations. Targeting binding partners of mutated ...RAS, however, presents a promising alternative therapeutic strategy. With the goal of uncovering novel interactors of RAS, we recently identified Argonaute 2 (AGO2) of the RNA-induced silencing complex (RISC) as a novel partner of the Switch II domain of KRAS. In order to assess the role of AGO2 in KRAS-G12D driven disease, we developed a mouse model of pancreatic cancer with conditional loss of AGO2. While AGO2 knockout did not prevent development of early precursor pancreatic intraepithelial (PanIN) lesions, loss of AGO2 prevented progression to late-stage PanINs, pancreactic ductal adenocarcinoma (PDAC), and metastatic disease. AGO2 null lesions displayed increased activation of the EGFR-RAS signaling axis during PanIN development. This signaling resulted in an increase in WT RAS-GTP activation, pEGFR-Y1068, and pERK levels leading to the development of oncogene-induced senescence in these PanIN lesions. Furthermore, we observed that EGFR-mediated phosphorylation of AGO2-Y393 disrupted the interaction between WT RAS and AGO2. This regulation by EGFR, however, was blocked in cells expressing mutant KRAS. These results suggested that the interaction of mutant RAS and AGO2 was vital to tumor development. To better assess the role of AGO2 loss in mutant RAS driven cancer, we performed AGO2 knockdown in multiple cell lines expressing mutations in either NRAS or HRAS isoforms. In each cell line, AGO2 directly interacted with KRAS, NRAS, and KRAS. In addition to suppressing growth in mutant RAS-driven cells (T24: HRAS-G12V, SK-MEL-2: NRAS-Q61H), loss of AGO2 produced marked increases in beta-galactosidase and p16 expression, as well as a decrease in cyclin D1, suggesting development of oncogene-induced senescence. Interestingly, upon AGO2 loss, cells displayed induction of pEGFR and pERK similar to what was observed in our pancreatic mouse model, and despite decreased expression of mutant RAS, WT RAS-GTP loading upon AGO2 loss was strongly induced. Together these results suggest a unique EGFR-AGO2-RAS signaling axis that requires AGO2-RAS interaction to prevent induction of oncogene-induced senescence in mutant RAS-driven cancers.
Citation Format: Ronald F. Siebenaler, Sunita Shankar, Jean C. Tien, Vijaya L. Dommeti, Sylvia Zelenka-Wang, Jessica Waninger, Malay Mody, Seema Chugh, Chandan Kumar-Sinha, Arul M. Chinnaiyan. Loss of Argonaute 2 leads to oncogene-induced senescence in mutant RAS-driven cancer abstract. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr A21.
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