Protein kinase C (PKC) isozymes have remained elusive cancer targets despite the unambiguous tumor promoting function of their potent ligands, phorbol esters, and the prevalence of their mutations. ...We analyzed 8% of PKC mutations identified in human cancers and found that, surprisingly, most were loss of function and none were activating. Loss-of-function mutations occurred in all PKC subgroups and impeded second-messenger binding, phosphorylation, or catalysis. Correction of a loss-of-function PKCβ mutation by CRISPR-mediated genome editing in a patient-derived colon cancer cell line suppressed anchorage-independent growth and reduced tumor growth in a xenograft model. Hemizygous deletion promoted anchorage-independent growth, revealing that PKCβ is haploinsufficient for tumor suppression. Several mutations were dominant negative, suppressing global PKC signaling output, and bioinformatic analysis suggested that PKC mutations cooperate with co-occurring mutations in cancer drivers. These data establish that PKC isozymes generally function as tumor suppressors, indicating that therapies should focus on restoring, not inhibiting, PKC activity.
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•Cancer-associated PKC mutations are LOF and can act in a dominant-negative manner•Correcting a heterozygous PKCβ LOF mutation reduces tumor volume•Hemizygous deletion shows PKC is haploinsufficient for tumor suppression•Therapeutic strategies should aim to restore PKC activity instead of inhibiting it
Cancer-associated kinase mutations have generally been characterized as oncogenic, but an analysis of PKC mutations reveals that the majority are loss of function, indicating a tumor-suppressive role for this kinase and a shift in therapeutic strategies targeting PKC.
Small-molecule inhibitors targeting growth factor receptors have failed to show efficacy for brain cancers, potentially due to their inability to achieve sufficient drug levels in the CNS. Targeting ...non-oncogene tumor co-dependencies provides an alternative approach, particularly if drugs with high brain penetration can be identified. Here we demonstrate that the highly lethal brain cancer glioblastoma (GBM) is remarkably dependent on cholesterol for survival, rendering these tumors sensitive to Liver X receptor (LXR) agonist-dependent cell death. We show that LXR-623, a clinically viable, highly brain-penetrant LXRα-partial/LXRβ-full agonist selectively kills GBM cells in an LXRβ- and cholesterol-dependent fashion, causing tumor regression and prolonged survival in mouse models. Thus, a metabolic co-dependency provides a pharmacological means to kill growth factor-activated cancers in the CNS.
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•Glioblastoma (GBM) cells rely on exogenous cholesterol for survival•GBM cells suppress cholesterol and liver X receptor (LXR) ligand synthesis•A brain-penetrant LXR agonist kills GBM cells in a cholesterol-dependent fashion
Villa et al. show that glioblastomas (GBM) are reliant on cholesterol uptake and highly sensitive to liver X receptor (LXR) agonist LXR-623, a full LXRβ and partial LXRα agonist. LXR-623 shows brain penetration and causes tumor regression in a GBM mouse model, reducing cholesterol and inducing cell death.
Chemotherapy and molecularly targeted approaches represent two very different modes of cancer treatment and each is associated with unique benefits and limitations. Both types of therapy share the ...overarching limitation of the emergence of drug resistance, which prevents these drugs from eliciting lasting clinical benefit. This review will provide an overview of the various mechanisms of resistance to each of these classes of drugs and examples of drug combinations that have been tested clinically. This analysis supports the contention that understanding modes of resistance to both chemotherapy and molecularly targeted therapies may be very useful in selecting those drugs of each class that will have complementing mechanisms of sensitivity and thereby represent reasonable combination therapies.
The highly lethal brain cancer glioblastoma (GBM) poses a daunting challenge because the blood-brain barrier renders potentially druggable amplified or mutated oncoproteins relatively inaccessible. ...Here, we identify sphingomyelin phosphodiesterase 1 (SMPD1), an enzyme that regulates the conversion of sphingomyelin to ceramide, as an actionable drug target in GBM. We show that the highly brain-penetrant antidepressant fluoxetine potently inhibits SMPD1 activity, killing GBMs, through inhibition of epidermal growth factor receptor (EGFR) signaling and via activation of lysosomal stress. Combining fluoxetine with temozolomide, a standard of care for GBM, causes massive increases in GBM cell death and complete tumor regression in mice. Incorporation of real-world evidence from electronic medical records from insurance databases reveals significantly increased survival in GBM patients treated with fluoxetine, which was not seen in patients treated with other selective serotonin reuptake inhibitor (SSRI) antidepressants. These results nominate the repurposing of fluoxetine as a potentially safe and promising therapy for patients with GBM and suggest prospective randomized clinical trials.
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•The unique membrane lipid composition makes GBMs sensitive to SMPD1 inhibition•Fluoxetine inhibits SMPD1, sphingomyelin metabolism, and EGFR signaling in GBM•Fluoxetine safely and potently shrinks GBM tumors and prevents recurrence in mice•Addition of fluoxetine to standard-of-care chemotherapy improves patient survival
Bi et al. reveal an actionable lipid vulnerability in GBM that can be exploited with a safe, highly brain-penetrant, FDA-approved drug. They show that fluoxetine kills GBMs by blocking acid sphingomyelinase, and they demonstrate that, when added to standard of care, fluoxetine, unlike other SSRIs, significantly improves patient survival.
In glioblastoma (GBM), heterogeneous expression of amplified and mutated epidermal growth factor receptor (EGFR) presents a substantial challenge for the effective use of EGFR-directed therapeutics. ...Here we demonstrate that heterogeneous expression of the wild-type receptor and its constitutively active mutant form, EGFRvIII, limits sensitivity to these therapies through an interclonal communication mechanism mediated by interleukin-6 (IL-6) cytokine secreted from EGFRvIII-positive tumor cells. IL-6 activates a NF-κB signaling axis in a paracrine and autocrine manner, leading to bromodomain protein 4 (BRD4)-dependent expression of the prosurvival protein survivin (BIRC5) and attenuation of sensitivity to EGFR tyrosine kinase inhibitors (TKIs). NF-κB and survivin are coordinately up-regulated in GBM patient tumors, and functional inhibition of either protein or BRD4 in in vitro and in vivo models restores sensitivity to EGFR TKIs. These results provide a rationale for improving anti-EGFR therapeutic efficacy through pharmacological uncoupling of a convergence point of NF-κB-mediated survival that is leveraged by an interclonal circuitry mechanism established by intratumoral mutational heterogeneity.
Epidermal growth factor receptor (EGFR) is overexpressed in head and neck squamous cell carcinoma (HNSCC) where expression levels correlate with decreased survival. Therapies that block EGFR have ...shown limited efficacy in clinical trials and primarily when combined with standard therapy. The most common form of mutant EGFR (EGFRvIII) has been described in several cancers, chiefly glioblastoma. The present study was undertaken to determine the incidence of EGFRvIII expression in HNSCC and the biological consequences of EGFRvIII on tumor growth in response to EGFR targeting.
Thirty-three HNSCC tumors were evaluated by immunostaining and reverse transcription-PCR for EGFRvIII expression. A representative HNSCC cell line was stably transfected with an EGFRvIII expression construct. EGFRvIII-expressing cells and vector-transfected controls were compared for growth rates in vitro and in vivo as well as chemotherapy-induced apoptosis and the consequences of EGFR inhibition using the chimeric monoclonal antibody C225/cetuximab/Erbitux.
EGFRvIII expression was detected in 42% of HNSCC tumors where EGFRvIII was always found in conjunction with wild-type EGFR. HNSCC cells expressing EGFRvIII showed increased proliferation in vitro and increased tumor volumes in vivo compared with vector-transfected controls. Furthermore, EGFRvIII-transfected HNSCC cells showed decreased apoptosis in response to cisplatin and decreased growth inhibition following treatment with C225 compared with vector-transfected control cells.
EGFRvIII is expressed in HNSCC where it contributes to enhanced growth and resistance to targeting wild-type EGFR. The antitumor efficacy of EGFR targeting strategies may be enhanced by the addition of EGFRvIII-specific blockade.
In silico interrogation of glioblastoma (GBM) in The Cancer Genome Atlas (TCGA) revealed upregulation of GNA12 (Gα12), encoding the alpha subunit of the heterotrimeric G-protein G12, concomitant with ...overexpression of multiple G-protein coupled receptors (GPCRs) that signal through Gα12. Glioma stem cell lines from patient-derived xenografts also showed elevated levels of Gα12. Knockdown (KD) of Gα12 was carried out in two different human GBM stem cell (GSC) lines. Tumors generated in vivo by orthotopic injection of Gα12KD GSC cells showed reduced invasiveness, without apparent changes in tumor size or survival relative to control GSC tumor-bearing mice. Transcriptional profiling of GSC-23 cell tumors revealed significant differences between WT and Gα12KD tumors including reduced expression of genes associated with the extracellular matrix, as well as decreased expression of stem cell genes and increased expression of several proneural genes. Thrombospondin-1 (THBS1), one of the genes most repressed by Gα12 knockdown, was shown to be required for Gα12-mediated cell migration in vitro and for in vivo tumor invasion. Chemogenetic activation of GSC-23 cells harboring a Gα12-coupled DREADD also increased THBS1 expression and in vitro invasion. Collectively, our findings implicate Gα12 signaling in regulation of transcriptional reprogramming that promotes invasiveness, highlighting this as a potential signaling node for therapeutic intervention.
The aim of this work was to evaluate the reproductive toxicological effects of uranium (U) at 2.5, 5, and 10 mgU/kg/d chronically administered in drinking water for 40 d. Swiss female control mice (n ...= 28) and mice chronically contaminated with uranyl nitrate in drinking water (n = 36) were tested. The number and quality of ovulated oocytes, chromatin organization, and nuclear integrity were evaluated. No significant differences were obtained in the numbers of ovulated oocytes between the different groups. Nevertheless, in 1,520 of the oocytes examined, dysmorphism increased from 11.99% in the control group to 27.99%, 27.19%, and 27.43% in each of the contaminated groups, respectively, in a dose-independent manner. On the other hand, morphological chromatin organization from 880 oocytes examined showed an increase in metaphase plate abnormalities from 37.20% (+/-7.21) in the control group to 55.13% (+/-21.36), 58.29% (+/-21.72), and 64.10% (+/-12.62) in each of the contaminated groups, respectively. Cumulus cell (CC) micronucleation, a parameter of nuclear integrity, increased from 0.21% (+/-0.31) in the control group to 1.92 (+/-0.95), 2.98 (+/-0.97), and 3.2 (+/-0.98), respectively. Both metaphase plate abnormalities and CC micronucleation showed an increase in a dose-dependent manner (r = 0.9; p < 0.001). The oocyte and its microenvironment showed high sensitivity to uranium contamination by drinking water. The lowest observed adverse effect level for this system is estimated at a level below 2.5 mgU/kg/d for female mice.
The consistency of the published values for fission averaged cross-sections of threshold reactions induced in a nuclear reactor is analyzed. The influence of the literature data involved in the ...determination of these cross-sections is discussed. Renormalizations based on cross-sections value for the standard reactions, isotopic abundances of the precursors and radiation emission probabilities of the radionuclide under study and the monitor, are applied to the evaluation of the cross-sections for the reactions: 46Ti(n,p)46Sc; 47Ti(n,p)47Sc; 48Ti(n,p)48Sc; and 64Zn(n,p)64Cu.
•Some published data on cross-sections averaged over a fission spectrum are analyzed.•The reactions were 46Ti(n,p)46Sc; 47Ti(n,p)47Sc; 48Ti(n,p)48Sc and 64Zn(n,p)64Cu.•Renormalization as a function of five critical parameters was performed.•Averages of the renormalized values were calculated and the results discussed.
Background
A short‐course of proton pump inhibitors (PPIs) is often used to confirm gastroesophageal reflux disease (GERD). However, some patients with PPI responsive heartburn do not seem to have ...evidence of GERD on impedance‐pH monitoring (MII‐pH). The aim of the study was to evaluate patients with reflux symptoms and a negative endoscopy, who well respond to PPIs with MII‐pH.
Methods
We enrolled 312 patients with GERD symptoms and negative endoscopy: 144 reported well‐controlled symptoms after 8‐week PPIs and 155 were non‐responders. Symptom relief was evaluated with GERD Impact Scale and visual analog scale score. All patients underwent MII‐pH off‐therapy. Thirteen patients were excluded from analysis. Patients were grouped as follows: non‐erosive reflux disease (NERD; increased acid exposure time, AET); hypersensitive esophagus (HE; normal AET, positive symptom association, SI/SAP); MII‐pH‐/PPI+ (normal AET, negative SI/SAP) in the responder group; MII‐pH‐/PPI‐ in non‐responders.
Key Results
MII‐pH in PPI responders (symptom relief during PPI therapy > 75%) showed: 79/144 NERD (54.9%); 37/144 HE (25.7%); 28/144 MII‐pH‐/PPI+ (19.4%). MII‐pH‐/PPI+ patients reported the same symptom relief when compared with NERD and HE. In non‐responder (symptom relief during PPI therapy < 50%) group, 27/155 patients were NERD (17.4%); 53/155 were HE (34.2%); 75/155 were MII‐pH‐/PPI‐ (48.4%). NERD diagnosis was significantly higher in responder group (p < 0.01).
Conclusions & Inferences
In a substantial subgroup of patients responding to PPI with typical reflux symptoms, the diagnosis of GERD cannot be confirmed with pH‐impedance monitoring. Proton pump inhibitor response and presence of typical symptoms are thus not reliable predictors of the diagnosis and antireflux surgery should always be preceded by reflux monitoring.
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