Pancreatic ductal adenocarcinoma is one of the deadliest carcinomas and is characterized by highly tumorigenic and metastatic cancer stem cells (CSC). CSCs evade available therapies, which ...preferentially target highly proliferative and more differentiated progenies, leaving behind CSCs as a putative source for disease relapse. Thus, to identify potentially more effective treatment regimens, we screened established and new compounds for their ability to eliminate CSCs in primary pancreatic cancer (stem) cells in vitro and corresponding patient-derived pancreatic cancer tissue xenografts in vivo. Intriguingly, we found that in vitro treatment with the antimalarial agent chloroquine significantly decreased CSCs, translating into diminished in vivo tumorigenicity and invasiveness in a large panel of pancreatic cancers. In vivo treatment in combination with gemcitabine was capable of more effectively eliminating established tumors and improved overall survival. The inhibitory effect of chloroquine was not related to inhibition of autophagy, but was due to inhibition of CXCL12/CXCR4 signaling, resulting in reduced phosphorylation of ERK and STAT3. Furthermore, chloroquine showed potent inhibition of hedgehog signaling by decreasing the production of Smoothened, translating into a significant reduction in sonic hedgehog-induced chemotaxis and downregulation of downstream targets in CSCs and the surrounding stroma. Our study demonstrates that via to date unreported effects, chloroquine is an effective adjuvant therapy to chemotherapy, offering more efficient tumor elimination and improved cure rates. Chloroquine should be further explored in the clinical setting as its success may help to more rapidly improve the poor prognosis of patients with pancreatic cancer.
Background & Aims Although smoking is a leading risk factor for pancreatic ductal adenocarcinoma (PDAC), little is known about the mechanisms by which smoking promotes initiation or progression of ...PDAC. Methods We studied the effects of nicotine administration on pancreatic cancer development in Kras +/LSLG12Vgeo ;Elas-tTA/tetO-Cre (Ela-KRAS) mice, Kras +/LSLG12D ;Trp53+/LSLR172H;Pdx-1-Cre (KPC) mice (which express constitutively active forms of KRAS), and C57/B6 mice. Mice were given nicotine for up to 86 weeks to produce blood levels comparable with those of intermediate smokers. Pancreatic tissues were collected and analyzed by immunohistochemistry and reverse transcriptase polymerase chain reaction; cells were isolated and assayed for colony and sphere formation and gene expression. The effects of nicotine were also evaluated in primary pancreatic acinar cells isolated from wild-type, nAChR7a−/− , Trp53−/− , and Gata6−/− ; Trp53−/− mice. We also analyzed primary PDAC cells that overexpressed GATA6 from lentiviral expression vectors. Results Administration of nicotine accelerated transformation of pancreatic cells and tumor formation in Ela-KRAS and KPC mice. Nicotine induced dedifferentiation of acinar cells by activating AKT–ERK–MYC signaling; this led to inhibition of Gata6 promoter activity, loss of GATA6 protein, and subsequent loss of acinar differentiation and hyperactivation of oncogenic KRAS. Nicotine also promoted aggressiveness of established tumors as well as the epithelial–mesenchymal transition, increasing numbers of circulating cancer cells and their dissemination to the liver, compared with mice not exposed to nicotine. Nicotine induced pancreatic cells to acquire gene expression patterns and functional characteristics of cancer stem cells. These effects were markedly attenuated in K-Ras+/LSL-G12D ; Trp53+/LSLR172H ; Pdx-1-Cre mice given metformin. Metformin prevented nicotine-induced pancreatic carcinogenesis and tumor growth by up-regulating GATA6 and promoting differentiation toward an acinar cell program. Conclusions In mice, nicotine promotes pancreatic carcinogenesis and tumor development via down-regulation of Gata6 to induce acinar cell dedifferentiation.
Conquering obesity has become a major socioeconomic challenge. Here, we show that reduced expression of the miR-25-93-106b cluster, or miR-93 alone, increases fat mass and, subsequently, insulin ...resistance. Mechanistically, we discovered an intricate interplay between enhanced adipocyte precursor turnover and increased adipogenesis. First, miR-93 controls Tbx3, thereby limiting self-renewal in early adipocyte precursors. Second, miR-93 inhibits the metabolic target Sirt7, which we identified as a major driver of in vivo adipogenesis via induction of differentiation and maturation of early adipocyte precursors. Using mouse parabiosis, obesity in mir-25-93-106b–/– mice could be rescued by restoring levels of circulating miRNA and subsequent inhibition of Tbx3 and Sirt7. Downregulation of miR-93 also occurred in obese ob/ob mice, and this phenocopy of mir-25-93-106b–/– was partially reversible with injection of miR-93 mimics. Our data establish miR-93 as a negative regulator of adipogenesis and a potential therapeutic option for obesity and the metabolic syndrome.
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•Knockout of the miR-25-93-106b cluster increased fat mass and insulin resistance•MiR-93 controls Tbx3 and thereby limits self-renewal of early adipocyte precursors•MiR-93 further inhibits the metabolic target Sirt7 and thus in vivo adipogenesis•(Circulating) miR-93 reduced obesity in miR-25-93-106b KO and ob/ob mice
Cioffi et al. provide evidence that miRNA-93 suppresses Tbx3 and Sirt7, thereby controlling expansion of adipocyte precursors and inhibiting adipogenesis, respectively.
Activation of calcium permeable glutamate receptors is likely to be important for neuronal death associated with brain trauma, stroke and neurodegenerative diseases. Cobalt uptake can be used to ...identify cells containing Ca2+-permeable non-NMDA ionotropic glutamate receptors. However, the relative contribution of AMPA and kainate receptors, and also the role of receptor desensitization on the influx of Co2+, remain to be established. We found that the selective non-desensitizing activation of AMPA receptors was efficient in promoting Co2+ staining. However, the selective activation of kainate receptors, even under non-desensitizing conditions, did not result in Co2+ staining. Taken together, our results show that non-desensitizing stimulation of AMPA, but not of kainate receptors, mediates the influx of Co2+ in cultured rat hippocampal neurons.
The lateral organization of lipids in cell membranes is thought to regulate numerous cell processes. Most studies focus on the coexistence of two fluid phases, the liquid crystalline (
l
d) and the ...liquid-ordered (
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o); the putative presence of gel domains (
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o) is not usually taken into account. We show that in phospholipid:sphingolipid:cholesterol mixtures, in which sphingomyelin (SM) promoted fluid
l
o domains, dihydrosphingomyelin (DHSM) tended to form rigid domains. Genetic and pharmacological blockade of the dihydroceramide desaturase (Des1), which replaced SM with DHSM in cultured cells, inhibited cell infection by replication-competent and -deficient HIV-1. Increased DHSM levels gave rise to more rigid membranes, resistant to the insertion of the gp41 fusion peptide, thus inhibiting viral-cell membrane fusion. These results clarify the function of dihydrosphingolipids in biological membranes and identify Des1 as a potential target in HIV-1 infection.
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► We show that dihydrosphingolipids form solid-ordered microdomains in model membranes ► Des1 inhibition increases dihydrosphingolipid levels in the membrane of living cells ► Chemical and genetic blockade of Des1 activity inhibits infection by HIV-1 ► Dihydrosphingolipid-enriched membranes are less prone to HIV-1 gp41-mediated fusion
Teaching students about the physiology of neurotransmitter receptors usually requires practical lessons with the use of sophisticated equipment and complex analysis of data. Here, we report our ...experience in teaching medical students with a simple, practical protocol that transforms the physiology of glutamate receptors into neuronal staining, observable under bright-field microscopy. Essentially, the students were challenged to selectively stain a subpopulation of cultured neurons expressing Ca(2+)-permeable alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors (a subgroup of ionotropic glutamate receptors). Neurons expressing this type of receptors were loaded with Co(2+) (in substitution for Ca(2+)) after nondesensitizing activation of AMPA receptors. After precipitation, the Co(2+) was revealed after treatment with silver. At the end of the procedure, the neurons expressing Ca(2+)-permeable AMPA receptors were visually identified under bright-field microscopy. The procedure allowed the visualization of the complete dendritic network of the stained neurons and allowed the students to learn very efficiently about the physiology of glutamate receptors.
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