Approximately 75% of all breast cancers express the oestrogen and/or progesterone receptors. Endocrine therapy is usually effective in these hormone-receptor-positive tumours, but primary and acquired resistance limits its long-term benefit 1,2 . Here we show that in mouse models of hormone-receptor-positive breast cancer, periodic fasting or a fasting-mimicking diet 3-5 enhances the activity of the endocrine therapeutics tamoxifen and fulvestrant by lowering circulating IGF1, insulin and leptin and by inhibiting AKT-mTOR signalling via upregulation of EGR1 and PTEN. When fulvestrant is combined with palbociclib (a cyclin-dependent kinase 4/6 inhibitor), adding periodic cycles of a fasting-mimicking diet promotes long-lasting tumour regression and reverts acquired resistance to drug treatment. Moreover, both fasting and a fasting-mimicking diet prevent tamoxifen-induced endometrial hyperplasia. In patients with hormone-receptor-positive breast cancer receiving oestrogen therapy, cycles of a fasting-mimicking diet cause metabolic changes analogous to those observed in mice, including reduced levels of insulin, leptin and IGF1, with the last two remaining low for extended periods. In mice, these long-lasting effects are associated with long-term anti-cancer activity. These results support further clinical studies of a fasting-mimicking diet as an adjuvant to oestrogen therapy in hormone-receptor-positive breast cancer.Growth factor signalling through the phosphoinositide 3-kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAP kinase) axes enhances oestrogen receptor activity and frequently underlies endocrine resistance in breast tumours 1,2,6 . Water-only fasting or plant-based diets that are simultaneously low in calories, sugar and protein and proportionally high in fat (fasting-mimicking diets (FMDs)) reduce circulating growth factors such as insulin and IGF1 2,6,7 . Therefore, we hypothesized that these dietary interventions could be used to enhance the activity of oestrogen therapy (ET) and delay endocrine resistance.Low-serum, low-glucose cell culture conditions designed to mimic the effects of fasting or FMD (referred to as short-term starvation, STS) increased the anti-tumour activities of tamoxifen and fulvestrant in HR + /HER2breast cancer (BC) cell lines, and similar results were obtained in mouse xenografts of the same cell lines subjected to weekly cycles of fasting or FMD (Fig. 1a, Extended Data Figs. 1, 2a, b). STS also increased the anti-tumour activity of tamoxifen in tumour organoids from patients with HR + BC 8 , and weekly FMD cycles prevented acquired resistance to tamoxifen in mice (Extended Data Fig. 2c, d). Enhancement of ET activity through STS was dependent on the reduction in serum, but not glucose, as adding back glucose to the growth medium did not affect the observed potentiation (Extended Data Fig. 3a).In mice, besides increasing β-hydroxybutyrate levels (Extended Data Fig. 3b) and lowering blood glucose (from 6.3 ± 0.6 mmol l −1 to 4.1 ± 0....

CD38, a transmembrane glycoprotein widely expressed in vertebrate cells, is a bifunctional ectoenzyme catalyzing the synthesis and hydrolysis of cyclic ADP-ribose (cADPR). cADPR is a universal second messenger that releases calcium from intracellular stores. Since cADPR is generated by CD38 at the outer surface of many cells, where it acts intracellularly, increasing attention is paid to addressing this topological paradox. Recently, we demonstrated that CD38 is a catalytically active, unidirectional transmembrane transporter of cADPR, which then reaches its receptor-operated intracellular calcium stores. Moreover, CD38 was reported to undergo a selective and extensive internalization through non clathrin-coated endocytotic vesicles upon incubating CD38(+) cells with either NAD+ or thiol compounds: these endocytotic vesicles can convert cytosolic NAD into cADPR despite an asymmetric unfavorable orientation that makes the active site of CD38 intravesicular. Here we demonstrate that the cADPR-generating activity of the endocytotic vesicles results in remarkable and sustained increases of intracellular free calcium concentration in different cells exposed to either NAD+, or GSH, or N-acetylcysteine. This effect of CD38-internalizing ligands on intracellular calcium levels was found to involve a two-step mechanism: 1) influx of cytosolic NAD+ into the endocytotic vesicles, mediated by a hitherto unrecognized dinucleotide transport system that is saturable, bidirectional, inhibitable by 8-N3-NAD+, and characterized by poor dinucleotide specificity, low affinity, and high efficiency; 2) intravesicular CD38-catalyzed conversion of NAD+ to cADPR, followed by outpumping of the cyclic nucleotide into the cytosol and subsequent release of calcium from thapsigargin-sensitive stores. This unknown intracellular trafficking of NAD+ and cADPR based on two distinctive and specific transmembrane carriers for either nucleotide can affect the intracellular calcium homeostasis in CD38(+) cells.

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Glial subcellular re-sealed particles (referred to as gliosomes here) were purified from rat cerebral cortex and investigated for their ability to release glutamate. Confocal microscopy showed that the glia-specific proteins glial fibrillary acidic protein (GFAP) and S-100, but not the neuronal proteins 95-kDa postsynaptic density protein (PSD-95), microtubule-associated protein 2 (MAP-2) and b-tubulin III, were enriched in purified gliosomes. Furthermore, gliosomes exhibited labelling neither for integrin-aM nor for myelin basic protein, which are specific for microglia and oligodendrocytes respectively. The Ca 2+ ionophore ionomycin (0. The role of glia in the brain is an area of intense investigation. In the past decade, exciting results in this field have led to dramatic conceptual changes about the role of glial cells, which were formerly thought to provide only structural and trophic support to neurones. An increasing number of papers have suggested that glia share at least some of the features typical of neurones, particularly those concerned with excitatory neurotransmission (for a review see Haydon 2001). In fact, glial cells are

In the last decade, substantial efforts have been made to identify NAD biosynthesis inhibitors, specifically against nicotinamide phosphoribosyltransferase (NAMPT), as preclinical studies indicate their potential efficacy as cancer drugs. However, the clinical activity of NAMPT inhibitors has proven limited, suggesting that alternative NAD production routes exploited by tumors confer resistance. Here, we show the gene encoding nicotinic acid phosphoribosyltransferase (NAPRT), a second NAD-producing enzyme, is amplified and overexpressed in a subset of common types of cancer, including ovarian cancer, where NAPRT expression correlates with a BRCAness gene expression signature. Both NAPRT and NAMPT increased intracellular NAD levels. NAPRT silencing reduced energy status, protein synthesis, and cell size in ovarian and pancreatic cancer cells. NAPRT silencing sensitized cells to NAMPT inhibitors both and; similar results were obtained with the NAPRT inhibitor 2-hydroxynicotinic acid. Reducing NAPRT levels in a BRCA2-deficient cancer cell line exacerbated DNA damage in response to chemotherapeutics. In conclusion, NAPRT-dependent NAD biosynthesis contributes to cell metabolism and to the DNA repair process in a subset of tumors. This knowledge could be used to increase the efficacy of NAMPT inhibitors and chemotherapy. .