Rationale
50-kHz ultrasonic vocalizations (USVs) emitted by adult rats are heterogeneous; they occur over a wide frequency range, show varying degrees of frequency modulation, and appear to differ in ...their behavioral significance. However, they have not been extensively categorized.
Objectives
The main objective of this study was to identify subtypes of 50-kHz USVs emitted by adult rats and to determine how amphetamine (AMPH) or social testing condition affects their relative and absolute production rate and acoustic characteristics. A second objective was to determine the extent of individual differences in call rate, call subtype profile, and acoustic parameters (i.e., duration, bandwidth, and mean peak frequency).
Methods
Adult male Long–Evans rats were administered systemic amphetamine (0.25–2 mg/kg, IP) and tested individually or with a cage mate for 20 min. Call categories were defined based on visual inspection of over 20,000 USV spectrograms. Surgical devocalization was performed on a subset of AMPH-tested rats in order to confirm the authenticity of call subtypes.
Results
Fourteen categories of 50-kHz USVs were recognized. Call subtypes were differentially affected by social context, AMPH dose, and time within session. In contrast, the acoustic characteristics of call subtypes were notably stable. Marked and stable inter-individual differences occurred with respect to overall 50-kHz call rate, acoustic parameters, and call profile.
Conclusions
The present findings, obtained under saline and amphetamine test conditions, provide the first detailed classification of adult rat 50-kHz USVs. Consideration of 50-kHz USV subtypes may advance our understanding of inter-rat communication and affective state.
Sucrose preference (SP) is a widely used measure of anhedonia in rat models of depression, yet depressed patients do not reliably show an analogous deficit. As an alternative affect-related measure, ...adult rat ultrasonic vocalizations (USVs) are attracting interest, but it is unclear whether SP and USVs provide independent measures. Here, we have assessed whether SP and USV emission are correlated in the absence of a depressogenic procedure. To this end, 24 male Long-Evans rats were tested daily for 24 days, with alternating SP tests and USV recordings; after a 3-month hiatus, USV emission was re-evaluated for 6 more days. SP was measured in simultaneous two-bottle choice tests, and USVs were recorded in an open field. The main measures were: SP, 50-kHz call rate, and relative prevalence of trill and flat call subtypes. These measures showed temporally-stable individual differences across the initial 24-day testing period, and at the 3-month USV follow-up tests. Correlational analysis revealed no significant relationships between SP and the three main USV measures. Rats differed consistently, not only in their 50-kHz call rates but also in their 50-kHz call profiles (i.e., the relative prevalence of 14 call subtypes); most rats preferentially emitted either trill or flat calls. Several inter-call subtype associations were detected, including a strong negative relationship between the relative prevalence of flat and trill calls. The 50-kHz call rate was correlated with the relative prevalence of only one call subtype (short calls, negative correlation), but was positively correlated with absolute emission rates for almost all subtypes. In conclusion, adult rats exhibited temporally-stable individual differences over weeks (SP) or months (USVs) of testing. This trait-like stability helped to reveal a lack of relationship between SP and the USV-related variables under study, suggesting that these measures may capture different constructs of possible relevance to animal models of depression.
Cyclin-dependent kinases (CDKs) contribute to the cancer hallmarks of uncontrolled proliferation and increased survival. As a result, over the last two decades substantial efforts have been directed ...towards identification and development of pharmaceutical CDK inhibitors. Insights into the biological consequences of CDK inhibition in specific tumor types have led to the successful development of CDK4/6 inhibitors as treatments for certain types of breast cancer. More recently, a new generation of pharmaceutical inhibitors of CDK enzymes that regulate the transcription of key oncogenic and pro-survival proteins, including CDK9, have entered clinical development. Here, we provide the first disclosure of the chemical structure of fadraciclib (CYC065), a CDK inhibitor and clinical candidate designed by further optimization from the aminopurine scaffold of seliciclib. We describe its synthesis and mechanistic characterization. Fadraciclib exhibits improved potency and selectivity for CDK2 and CDK9 compared to seliciclib, and also displays high selectivity across the kinome. We show that the mechanism of action of fadraciclib is consistent with potent inhibition of CDK9-mediated transcription, decreasing levels of RNA polymerase II C-terminal domain serine 2 phosphorylation, the pro-survival protein Myeloid Cell Leukemia 1 (MCL1) and MYC oncoprotein, and inducing rapid apoptosis in cancer cells. This cellular potency and mechanism of action translate to promising anti-cancer activity in human leukemia mouse xenograft models. Studies of leukemia cell line sensitivity identify mixed lineage leukemia (MLL) gene status and the level of B-cell lymphoma 2 (BCL2) family proteins as potential markers for selection of patients with greater sensitivity to fadraciclib. We show that the combination of fadraciclib with BCL2 inhibitors, including venetoclax, is synergistic in leukemic cell models, as predicted from simultaneous inhibition of MCL1 and BCL2 pro-survival pathways. Fadraciclib preclinical pharmacology data support its therapeutic potential in CDK9- or CDK2-dependent cancers and as a rational combination with BCL2 inhibitors in hematological malignancies. Fadraciclib is currently in Phase 1 clinical studies in patients with advanced solid tumors (NCT02552953) and also in combination with venetoclax in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) (NCT03739554) and relapsed refractory acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) (NCT04017546).
Over the past two decades there has been a great deal of interest in the development of inhibitors of the cyclin-dependent kinases (CDKs). This attention initially stemmed from observations that ...different CDK isoforms have key roles in cancer cell proliferation through loss of regulation of the cell cycle, a hallmark feature of cancer. CDKs have now been shown to regulate other processes, particularly various aspects of transcription. The early non-selective CDK inhibitors exhibited considerable toxicity and proved to be insufficiently active in most cancers. The lack of patient selection biomarkers and an absence of understanding of the inhibitory profile required for efficacy hampered the development of these inhibitors. However, the advent of potent isoform-selective inhibitors with accompanying biomarkers has re-ignited interest. Palbociclib, a selective CDK4/6 inhibitor, is now approved for the treatment of ER+/HER2- advanced breast cancer. Current developments in the field include the identification of potent and selective inhibitors of the transcriptional CDKs; these include tool compounds that have allowed exploration of individual CDKs as cancer targets and the determination of their potential therapeutic windows. Biomarkers that allow the selection of patients likely to respond are now being discovered. Drug resistance has emerged as a major hurdle in the clinic for most protein kinase inhibitors and resistance mechanism are beginning to be identified for CDK inhibitors. This suggests that the selective inhibitors may be best used combined with standard of care or other molecularly targeted agents now in development rather than in isolation as monotherapies.
Rationale
The behavioral effects of the nicotine metabolites nornicotine and cotinine have not been investigated extensively.
Objectives
To evaluate the effects of nicotine, cotinine, and ...nornicotine, given alone or in combination, on locomotor activity and emission of ultrasonic vocalizations in male adult rats.
Methods
Rats were first given home cage nicotine injections to make them tolerant to the drug’s locomotor depressant effects. On subsequent days, locomotor activity (LMA) and ultrasonic vocalizations were recorded in an open field, for 60 min after challenge injection, using repeated measures designs. In single-drug experiments, subjects were tested with nicotine 0.05–0.4 mg/kg, cotinine 0.03–3 mg/kg, or nornicotine 0.1–10 mg/kg. In drug-combination experiments, saline or nicotine 0.2 mg/kg challenge was preceded by cotinine (0, 0.3, 3 mg/kg) or nornicotine (0, 0.1, 0.3, 1, 3 mg/kg) injection.
Results
High doses of nornicotine increased LMA and blunted the locomotor stimulant effect of nicotine. Less consistently, nicotine and high doses of nornicotine decreased the 50-kHz call rate, with no clear evidence of a nornicotine × nicotine interaction. Cotinine, given alone or before nicotine injection, altered neither LMA nor the call rate. No drug altered the relative prevalence of flat vs. trill 50-kHz call subtypes, except that the highest dose of nornicotine promoted flat calls over trills. No drug evoked 22-kHz calls.
Conclusion
Nornicotine can exert an acute anti-nicotine effect in vivo
,
as previously reported in vitro. The finding that nicotine did not detectably alter the 50-kHz call profile appears consistent with this drug’s mild subjective effects in human subjects.
The discovery and development of small molecule cancer drugs has been revolutionised over the last decade. Most notably, we have moved from a one-size-fits-all approach that emphasized cytotoxic ...chemotherapy to a personalised medicine strategy that focuses on the discovery and development of molecularly targeted drugs that exploit the particular genetic addictions, dependencies and vulnerabilities of cancer cells. These exploitable characteristics are increasingly being revealed by our expanding understanding of the abnormal biology and genetics of cancer cells, accelerated by cancer genome sequencing and other high-throughput genome-wide campaigns, including functional screens using RNA interference. In this review we provide an overview of contemporary approaches to the discovery of small molecule cancer drugs, highlighting successes, current challenges and future opportunities. We focus in particular on four key steps: Target validation and selection; chemical hit and lead generation; lead optimization to identify a clinical drug candidate; and finally hypothesis-driven, biomarker-led clinical trials. Although all of these steps are critical, we view target validation and selection and the conduct of biology-directed clinical trials as especially important areas upon which to focus to speed progress from gene to drug and to reduce the unacceptably high attrition rate during clinical development. Other challenges include expanding the envelope of druggability for less tractable targets, understanding and overcoming drug resistance, and designing intelligent and effective drug combinations. We discuss not only scientific and technical challenges, but also the assessment and mitigation of risks as well as organizational, cultural and funding problems for cancer drug discovery and development, together with solutions to overcome the ‘Valley of Death’ between basic research and approved medicines. We envisage a future in which addressing these challenges will enhance our rapid progress towards truly personalised medicine for cancer patients.
► Here we review small molecule cancer drug discovery and development. ► We focus on Target selection, hit identification, lead optimization and clinical trials. ► A particular emphasis of this article is personalized medicine.
Highlights • PI3K is an important target for innovative anticancer drug development and precision medicine. • Over 30 small molecule PI3K inhibitors are currently in clinical trial testing. • These ...drugs include dual PI3K/mTOR, pan-Class I PI3K and isoform-selective PI3K inhibitors. • The PI3Kδ inhibitor idelalisib has received FDA approval for the treatment of B-cell malignancies. • Drug resistance, patient selection and development of targeted combinations remain challenges.
Huang et al. (2021) identified a mechanism acting through the arginine methyltransferase PRMT6 that stabilizes the interaction of RCC1 with chromatin, promoting cell proliferation and tumorigenicity. ...Targeting this mechanism might enhance the treatment of tumors such as glioblastoma.
Huang et al. (2021) identified a mechanism acting through the arginine methyltransferase PRMT6 that stabilizes the interaction of RCC1 with chromatin, promoting cell proliferation and tumorigenicity. Targeting this mechanism might enhance the treatment of tumors such as glioblastoma.
The small nuclear GTPase Ran controls the directionality of macromolecular transport between the nucleus and the cytoplasm. Ran also has important roles during mitosis, when the nucleus is ...dramatically reorganized to allow chromosome segregation. Ran directs the assembly of the mitotic spindle, nuclear-envelope dynamics and the timing of cell-cycle transitions. The mechanisms that underlie these functions provide insights into the spatial and temporal coordination of the changes that occur in intracellular organization during the cell-division cycle.
Rationale
Systemic amphetamine (AMPH) administration increases the rate of 50-kHz ultrasonic vocalizations (USVs) in adult rats and preferentially enhances the ‘trill’ subtype; these effects of AMPH ...critically depend on noradrenergic transmission, but the possible contributions of dopamine are unclear.
Objective
To assess the role of dopamine in 50-kHz USVs emitted drug-free and following systemic AMPH administration.
Methods
Adult male Long–Evans rats pre-selected for high AMPH-induced calling rates were tested with AMPH (1 mg/kg, intraperitoneal (IP)) and saline following pretreatment with the following dopamine receptor antagonists: SCH 23390 (0.005–0.02 mg/kg, subcutaneous (SC)), SCH 39166 (0.03–0.3 mg/kg, SC), haloperidol (0.1, 0.2 mg/kg, IP), sulpiride (20–80 mg/kg, SC), raclopride (0.1–0.5 mg/kg, SC), clozapine (4 mg/kg, SC), risperidone (0.5 mg/kg, SC), and pimozide (1 mg/kg, IP). The dopamine and noradrenaline reuptake inhibitors (GBR 12909 and nisoxetine, respectively) were also tested, alone and in combination.
Results
SCH 23390, SCH 39166, haloperidol, and raclopride dose-dependently inhibited vocalizations under AMPH and suppressed the proportion of trill calls. Sulpiride, however, had no discernable effect on call rate or profile, even at a high dose that reduced locomotor activity. Single doses of clozapine, risperidone, and pimozide all markedly decreased calling under saline and AMPH. Finally, GBR 12909 and nisoxetine failed to promote 50-kHz USVs detectably or alter the subtype profile, when tested alone or in combination.
Conclusions
The rate of 50-kHz USVs and the call subtype profile following systemic AMPH administration depends on dopaminergic neurotransmission through D1-like and D2-like receptors. However, inhibiting dopamine and/or noradrenaline reuptake appears insufficient to induce calling.
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