Mechanism of action of rapamycin: new insights into the regulation of G1-phase progression in eukaryotic cells

Sirolimus reduces T cell cycling, immune checkpoint marker expression, and HIV-1 DNA in people with HIV

Key HIV cure strategies involve reversing immune dysfunction and limiting the proliferation of infected T cells. We evaluate the safety of sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, in people with HIV (PWH) and study the impact of sirolimus on HIV-1 reservoir size and HIV-1-specific immunity in a single-arm study of 20 weeks of treatment in PWH on antiretroviral therapy (ART). Sirolimus treatment does not impact HIV-1-specific CD8 T cell responses but leads to a significant decrease in CD4+ T cell-associated HIV-1 DNA levels at 20 weeks of therapy in the primary efficacy population (n = 16; 31% decline, p = 0.008). This decline persists for at least 12 weeks following cessation of the study drug. Sirolimus treatment also leads to a significant reduction in CD4+ T cell cycling and PD-1 expression on CD8+ lymphocytes. These data suggest that homeostatic proliferation of infected cells, an important mechanism for HIV persistence, is an intriguing therapeutic target.

lncRNA TINCR promotes the development of cervical cancer via the miRNA‑7/mTOR axis in vitro

The present study aimed to examine the effects of the long non-coding (lnc)RNA expressed by tissue differentiation-inducing non-protein coding RNA (TINCR) on cervical cancer development. For this purpose, adjacent normal and cancer tissues were obtained from patients with cervical cancer and the lncRNA TINCR level was examined using reverse transcription-quantitative PCR (RT-qPCR) and in situ hybridization. The association between lncRNA TINCR and the clinicopathological characteristics and prognosis of patients with cervical cancer was also analyzed. Furthermore, the expression levels of lncRNA TINCR, miRNA-7, mTOR, hypoxia-inducible factor 1 subunit α and VEGF were measured using RT-qPCR and western blot analysis. Cell proliferation, apoptosis, and invasion and migration were examined using MTT assay, 5-ethynyl-2'-deoxyuridine staining, flow cytometry, TUNEL assay, and Transwell and wound healing assays. The association between lncRNA TINCR, miRNA-7 and mTOR was also examined using a luciferase assay. The results revealed that the lncRNA TINCR level was significantly increased in cervical cancer tissues and was associated with the overall survival of patients (low vs. high expression group; P=0.0391). LncRNA TINCR was also associated with the clinicopathological characteristics of patients with cervical cancer. Following the knockdown of lncRNA TINCR using small interfering (si)RNA, cell proliferation was significantly decreased and cell apoptosis was significantly increased (P<0.001 for both); cell invasion and migration were also significantly decreased (P<0.001 for both) following transfection with mimics miRNA-7. Transfection with miRNA-7 antisense oligonucleotide decreased the antitumor effects of si-TINCR in Siha and HeLa cell lines. As shown using the dual-luciferase assay, lncRNA TINCR could target miRNA-7 and miRNA-7 could directly regulate mTOR in HeLa and SiHa cell lines. In conclusion, the present study demonstrated that lncRNA TINCR could promote cervical cancer development via regulation of the miRNA-7/mTOR axis in vitro.

Rapamycin Treatment Alleviates Chronic GVHD-Induced Lupus Nephritis in Mice by Recovering IL-2 Production and Regulatory T Cells While Inhibiting Effector T Cells Activation

In this study, we test the therapeutic effects of rapamycin in a murine model of SLE-like experimental lupus nephritis induced by chronic graft-versus-host disease (cGVHD). Our results suggest that rapamycin treatment reduced autoantibody production, inhibited T lymphocyte and subsequent B cell activation, and reduced inflammatory cytokine and chemokine production, thereby protecting renal function and alleviating histological lupus nephritis by reducing the occurrence of albuminuria. To explore the potential mechanism of rapamycin's reduction of kidney damage in mice with lupus nephritis, a series of functional assays were conducted. As expected, rapamycin remarkably inhibited the lymphocytes' proliferation within the morbid mice. Interestingly, significantly increased proportions of peripheral CD4+FOXP3+ and CD4+CD25high T cells were observed in rapamycin-treated group animals, suggesting an up-regulation of regulatory T cells (Tregs) in the periphery by rapamycin treatment. Furthermore, consistent with the results regarding changes in mRNA abundance in kidney by real-time PCR analysis, intracellular cytokine staining demonstrated that rapamycin treatment remarkably diminished the secretion of Th1 and Th2 cytokines, including IFN-γ, IL-4 and IL-10, in splenocytes of the morbid mice. However, the production of IL-2 from splenocytes in rapamycin-treated mice was significantly higher than in the cells from control group animals. These findings suggest that rapamycin treatment might alleviate systemic lupus erythematosus (SLE)-like experimental lupus nephritis through the recovery of IL-2 production, which promotes the expansion of regulatory T cells while inhibiting effector T cell activation. Our studies demonstrated that, unlike other commonly used immunosuppressants, rapamycin does not appear to interfere with tolerance induction but permits the expansion and suppressive function of Tregs in vivo.

Crystal packing reveals rapamycin-mediated homodimerization of an FK506-binding domain

Chemically induced dimerization (CID) is used to induce proximity and result in artificial complex formation between a pair of proteins involved in biological processes in cells to investigate and regulate these processes. The induced heterodimerization of FKBP fusion proteins by rapamycin and FK506 has been extensively exploited as a chemically induced dimerization system to regulate and understand highly dynamic cellular processes. Here, we report the crystal structure of the AtFKBP53 FKBD in complex with rapamycin. The crystal packing reveals an unusual feature whereby two rapamycin molecules appear to mediate homodimerization of the FKBD. The triene arm of rapamycin appears to play a significant role in forming this dimer. This forms the first structural report of rapamycin-mediated homodimerization of an FKBP. The structural information on the rapamycin-mediated FKBD dimerization may be employed to design and synthesize covalently linked dimeric rapamycin, which may subsequently serve as a chemically induced dimerization system for the regulation and characterization of cellular processes.

MTOR Signaling and Metabolism in Early T Cell Development

The mechanistic target of rapamycin (mTOR) controls cell fate and responses via its functions in regulating metabolism. Its role in controlling immunity was unraveled by early studies on the immunosuppressive properties of rapamycin. Recent studies have provided insights on how metabolic reprogramming and mTOR signaling impact peripheral T cell activation and fate. The contribution of mTOR and metabolism during early T-cell development in the thymus is also emerging and is the subject of this review. Two major T lineages with distinct immune functions and peripheral homing organs diverge during early thymic development; the αβ- and γδ-T cells, which are defined by their respective TCR subunits. Thymic T-regulatory cells, which have immunosuppressive functions, also develop in the thymus from positively selected αβ-T cells. Here, we review recent findings on how the two mTOR protein complexes, mTORC1 and mTORC2, and the signaling molecules involved in the mTOR pathway are involved in thymocyte differentiation. We discuss emerging views on how metabolic remodeling impacts early T cell development and how this can be mediated via mTOR signaling.

Everolimus, an mTORC1/2 inhibitor, in ART-suppressed individuals who received solid organ transplantation: A prospective study

Pharmacologic inhibition of the mammalian target of rapamycin (mTOR) in the setting of renal transplantation has previously been associated with lower human immunodeficiency virus 1 (HIV-1) DNA burden, and in vitro studies suggest that mTOR inhibition may lead to HIV transcriptional silencing. Because prospective clinical trials are lacking, we conducted an open-label, single-arm study to determine the impact of the broad mTOR inhibitor, everolimus, on residual HIV burden, transcriptional gene expression profiles, and immune responses in HIV-infected adult solid organ transplant (SOT) recipients on antiretroviral therapy. Whereas everolimus therapy did not have an overall effect on cell-associated HIV-1 DNA and RNA levels in the entire cohort, participants who maintained everolimus time-averaged trough levels >5 ng/mL during the first 2 months of therapy had significantly lower RNA levels up to 6 months after the cessation of study drug. Time-averaged everolimus trough levels significantly correlated with greater inhibition of mTOR gene pathway transcriptional activity. Everolimus treatment also led to decreased PD-1 expression on certain T cell subsets. These data support the rationale for further study of the effects of mTOR inhibition on HIV transcriptional silencing in non-SOT populations, either alone or in combination with other strategies. Trial Registration: ClinicalTrials.gov NCT02429869.

Effects of Aging on Angiogenic and Muscle Growth-Related Factors in Naturally Aged Rat Skeletal Muscles

Background

This study explored the effects of aging on the expression of angiogenic and muscle protein synthesis factors, as well as the number of satellite cells affecting sarcopenia in naturally aged rat skeletal muscles.

Methods

We divided 16 Sprague-Dawley rats into young (12 weeks old, n=8) and old (24 months old, n=8) groups and compared muscle and body weight (BW) between them. We also analyzed the expression levels of angiogenic and muscle growth proteins in soleus (slow-twitch) and extensor digitorum longus (EDL; fast-twitch) muscles by western blotting and assessed the number of skeletal muscle satellite cells and myonuclei and mean fiber cross-sectional area (CSA) using by immunofluorescence staining.

Results

EDL/BW was significantly lower in old rats than in young rats (p=0.002). The vascular endothelial growth factor level in soleus muscles was significantly lower in old rats than in young rats (p=0.001). Hypoxia-inducible factor 1-alpha and fetal liver kinase 1 levels in EDL muscles were lower in old rats than in young rats (p=0.001). The mammalian target of rapamycin (mTOR), p70S6K, and 4E-BP1 levels were significantly lower in the soleus muscles of old rats than in those of young rats (p<0.01). Similarly, insulin growth factor-1, Akt, mTOR, and p70S6K levels were significantly lower in EDL muscles of old rats than in those of young rats (p<0.01). Additionally, myonuclei/fiber, Pax7/fiber, and mean fiber CSAs in both muscle types were significantly lower in old rats than in young rats (p<0.01).

Conclusion

These data suggest different regulation of indices of angiogenic and muscle growth with aging in different muscle types.

Mammalian Target of Rapamycin-RhoA Signaling Impairments in Direct Striatal Projection Neurons Induce Altered Behaviors and Striatal Physiology in Mice

BACKGROUND

As an integrator of molecular pathways, mTOR (mammalian target of rapamycin) has been associated with diseases including neurodevelopmental, psychiatric, and neurodegenerative disorders such as autism spectrum disorder, schizophrenia, and Huntington's disease. An important brain area involved in all these diseases is the striatum. However, the mechanisms behind how mTOR is involved in striatal physiology and its relative role in distinct neuronal populations in these striatal-related diseases still remain to be clarified.

METHODS

Using Drd1-Cre mTOR-conditional knockout male mice, we combined behavioral, biochemical, electrophysiological, and morphological analysis aiming to untangle the role of mTOR in direct pathway striatal projection neurons and how this would impact on striatal physiology.

RESULTS

Our results indicate deep behavioral changes in absence of mTOR in Drd1-expressing neurons such as decreased spontaneous locomotion, impaired social interaction, and decreased marble-burying behavior. These alterations were accompanied by a Kv1.1-induced increase in the fast phase of afterhyperpolarization and coincident decreased distal spine density in striatal direct pathway striatal projection neurons. The physiological changes were mechanistically independent of protein synthesis but sensitive to pharmacological blockade of transforming protein RhoA activity.

CONCLUSIONS

These results identify mTOR signaling as an important regulator of striatal functions through an intricate mechanism involving RhoA and culminating in Kv1.1 overfunction, which could be targeted to treat striatal-related monogenic disorders associated with the mTOR signaling pathway.

The Regulatory Effects of mTOR Complexes in the Differentiation and Function of CD4+ T Cell Subsets

T cells are an important part of the adaptive immune system and play critical roles in the elimination of various pathogens. T cells could differentiate into distinct cellular subsets under different extracellular signals and then play different roles in maintaining host homeostasis and defense. The mechanistic target of rapamycin (mTOR) is a conserved intracellular serine/threonine kinase which belongs to the phosphoinositide 3-kinase- (PI3K-) related kinase family. The mTOR signaling pathway is closely involved in a variety of cell biological processes, including cell growth and cell metabolism, by senses and integrates various environmental cues. Recent studies showed that mTOR including mTORC1 and mTORC2 is closely involved in the development of T cell subpopulations such as Th1, Th2, Th9, Th17, follicular helper T cells (Tfh), and Treg cells through distinctive pathways. We herein mainly focused on the recent progress in understanding the roles of mTOR in regulating the development and differentiation of CD4⁺ T cell subsets.

Transcription and Translation Inhibitors in Cancer Treatment

Transcription and translation are fundamental cellular processes that govern the protein production of cells. These processes are generally up regulated in cancer cells, to maintain the enhanced metabolism and proliferative state of these cells. As such cancerous cells can be susceptible to transcription and translation inhibitors. There are numerous druggable proteins involved in transcription and translation which make lucrative targets for cancer drug development. In addition to proteins, recent years have shown that the "undruggable" transcription factors and RNA molecules can also be targeted to hamper the transcription or translation in cancer. In this review, we summarize the properties and function of the transcription and translation inhibitors that have been tested and developed, focusing on the advances of the last 5 years. To complement this, we also discuss some of the recent advances in targeting oncogenes tightly controlling transcription including transcription factors and KRAS. In addition to natural and synthetic compounds, we review DNA and RNA based approaches to develop cancer drugs. Finally, we conclude with the outlook to the future of the development of transcription and translation inhibitors.

Effect of PFOA on DNA Methylation and Alternative Splicing in Mouse Liver

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant prevalent in the environment and implicated in damage to the liver leading to a fatty liver phenotype called hepatocellular steatosis. Our goal is to provide a basis for PFOA-induced hepatocellular steatosis in relation to epigenetic alterations and mRNA splicing. Young adult female mice exposed to different concentrations of PFOA showed an increase in liver weight with decreased global DNA methylation (5-mC). At higher concentrations, the expression of DNA methyltransferase 3A (Dnmt3a) was significantly reduced and the expression of tet methycytosine dioxygenase 1 (Tet1) was significantly increased. There was no significant change in the other Dnmts and Tets. PFOA exposure significantly increased the expression of cell cycle regulators and anti-apoptotic genes. The expression of multiple genes involved in mTOR (mammalian target of rapamycin) signaling pathway were altered significantly with reduction in Pten (phosphatase and tensin homolog, primary inhibitor of mTOR pathway) expression. Multiple splicing factors whose protein but not mRNA levels affected by PFOA exposure were identified. The changes in protein abundance of the splicing factors was also reflected in altered splicing pattern of their target genes, which provided new insights on the previously unexplored mechanisms of PFOA-mediated hepatotoxicity and pathogenesis.

A phase I study of sirolimus in combination with metronomic therapy (CHOAnome) in children with recurrent or refractory solid and brain tumors

BACKGROUND/PURPOSE

To determine the maximum tolerated dose, toxicities, and response of sirolimus combined with oral metronomic therapy in pediatric patients with recurrent and refractory solid and brain tumors.

PROCEDURE

Patients younger than 30 years of age with recurrent, refractory, or high-risk solid and brain tumors were eligible. Patients received six-week cycles of sirolimus with twice daily celecoxib, and alternating etoposide and cyclophosphamide every three weeks, with Bayesian dose escalation over four dose levels (NCT01331135).

RESULTS

Eighteen patients were enrolled: four on dose level (DL) 1, four on DL2, eight on DL3, and two on DL4. Diagnoses included solid tumors (Ewing sarcoma, osteosarcoma, malignant peripheral nerve sheath tumor, rhabdoid tumor, retinoblastoma) and brain tumors (glioblastoma multiforme [GBM], diffuse intrinsic pontine glioma, high-grade glioma [HGG], medulloblastoma, ependymoma, anaplastic astrocytoma, low-grade infiltrative astrocytoma, primitive neuroectodermal tumor, nongerminomatous germ cell tumor]. One dose-limiting toxicity (DLT; grade 4 neutropenia) was observed on DL2, two DLTs (grade 3 abdominal pain and grade 3 mucositis) on DL3, and two DLTs (grade 3 dehydration and grade 3 mucositis) on DL4. The recommended phase II dose of sirolimus was 2 mg/m² (DL3). Best response was stable disease (SD) in eight patients, and partial response (PR) in one patient with GBM. A patient with HGG was removed from the study with SD and developed PR without further therapy. Western blot analysis showed inhibition of phospho-S6 kinase in all patients during the first cycle of therapy.

CONCLUSION

The combination of sirolimus with metronomic chemotherapy is well tolerated in children. A phase II trial of this combination is ongoing.

Kaempferol attenuates imiquimod-induced psoriatic skin inflammation in a mouse model

Psoriasis is an immune-mediated inflammatory skin disease that mainly affects the skin barrier. Treatment for psoriasis mainly includes conventional immunosuppressive drugs. However, long-term treatment with global immunosuppressive agents may cause a variety of side effects, including nephrotoxicity and infections. Kaempferol, a natural flavonol present in various plants, is known to possess potent anti-inflammatory, anti-oxidant and anti-cancerous properties. However, it is unknown whether kaempferol is also anti-psoriatic. Here we established an imiquimod (IMQ)-induced psoriatic mouse model to explore the potential therapeutic effects of kaempferol on psoriatic skin lesions and inflammation. In this study, we demonstrated that treatment with kaempferol protected mice from developing psoriasis-like skin lesions induced by topical administration of IMQ. Kaempferol reduced CD3⁺ T cell infiltration and gene expression of major proinflammatory cytokines, including interleukin (IL)-6, IL-17A and tumor necrosis factor (TNF)-α, in the psoriatic skin lesion. It also down-regulated proinflammatory nuclear factor kappa B (NF-κB) signaling in the skin. The therapeutic effects were associated with a significant increase in CD4⁺ forkhead box protein 3 (FoxP3)⁺ regulatory T cell (T_reg ) frequency in the spleen and lymph nodes as well as FoxP3-positive staining in the skin lesion. Conversely, depletion of CD4⁺ CD25⁺ T_regs reversed the therapeutic effects of kaempferol on the skin lesion. Kaempferol also lowered the percentage of IL-17A⁺ CD4⁺ T cells in the spleen and lymph nodes of IMQ-induced psoriatic mice. Finally, kaempferol suppressed the proliferation of T cells in vitro and their mTOR signaling. Thus, our findings suggest that kaempferol may be a therapeutic drug for treating human psoriasis in the near future.

Shikonin Prolongs Allograft Survival via Induction of CD4+FoxP3+ Regulatory T Cells

A transplanted organ is usually rejected without any major immunosuppressive treatment because of vigorous alloimmune responsiveness. However, continuous global immunosuppression may cause severe side effects, including nephrotoxicity, tumors, and infections. Therefore, it is necessary to seek novel immunosuppressive agents, especially natural ingredients that may provide sufficient efficacy in immunosuppression with minimal side effects. Shikonin is a bioactive naphthoquinone pigment, an ingredient originally extracted from the root of Lithospermum erythrorhizon. Previous studies have shown that shikonin regulates immunity and exerts anti-inflammatory effects. In particular, it can ameliorate arthritis in animal models. However, it is unclear whether shikonin inhibits alloimmunity or allograft rejection. In this study and for the first time, we demonstrated that shikonin significantly prolonged the survival of skin allografts in wild-type mice. Shikonin increased the frequencies of CD4⁺Foxp3⁺ regulatory T cells (Tregs) post-transplantation and induced CD4⁺Foxp3⁺ Tregs in vitro as well. Importantly, depleting the Tregs abrogated the extension of skin allograft survival induced by shikonin. It also decreased the frequencies of CD8⁺CD44^highCD62L^low effector T cells and CD11c⁺CD80⁺/CD11c⁺CD86⁺ mature DCs after transplantation. Moreover, we found that shikonin inhibited the proliferation of T cells in vitro and suppressed their mTOR signaling. It also reduced the gene expression of pro-inflammatory cytokines, including IFNγ, IL-6, TNFα, and IL-17A, while increasing the gene expression of anti-inflammatory mediators IL-10, TGF-β1, and indoleamine-2, 3-dioxygenase (IDO) in skin allografts. Further, shikonin downregulated IDO protein expression in skin allografts and DCs in vitro. Taken together, shikonin inhibits allograft rejection via upregulating CD4⁺Foxp3⁺ Tregs. Thus, shikonin is a novel immunosuppressant that could be potentially used in clinical transplantation.

mTOR signaling in the nucleus accumbens mediates behavioral sensitization to methamphetamine

Chronic psychostimulant treatment in rodents readily produces behavioral sensitization, which reflects altered brain function in response to repeated drug exposure. Numerous morphological and biochemical investigations implicate altered neural plasticity in striatal medium spiny neurons (MSNs) as an essential component in behavioral sensitization. The mammalian target of the rapamycin (mTOR) signaling pathway, a key regulator of synaptic neuroplasticity, in the ventral striatum of methamphetamine (METH) -sensitized mice was investigated to determine if a link exists with the development of METH sensitization. Behaviorally, METH-sensitized mice possessed increased levels of phosphorylated mTOR/S2448 and its down-stream regulator p70S6K and pS6 in the ventral striatum. Systemic treatment with rapamycin, a specific mTOR inhibitor, coincident with a daily METH injection suppressed the induction of METH sensitization and reduced the number of dendritic spines in the shell and core of the nucleus accumbens. The infusion of lentivirus-expressing mTOR-shRNA into the shell region of the nucleus accumbens inhibited the induction of behavioral sensitization to METH, which was comparable to the effect of rapamycin. These results suggest that mTORC1-mediated signaling in the nucleus accumbens mediates the development of behavioral sensitization to METH.

Emerging Role of mTOR Signaling-Related miRNAs in Cardiovascular Diseases

Mechanistic/mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase of the phosphoinositide 3-kinase- (PI3K-) related kinase family, elicits a vital role in diverse cellular processes, including cellular growth, proliferation, survival, protein synthesis, autophagy, and metabolism. In the cardiovascular system, the mTOR signaling pathway integrates both intracellular and extracellular signals and serves as a central regulator of both physiological and pathological processes. MicroRNAs (miRs), a class of short noncoding RNA, are an emerging intricate posttranscriptional modulator of critical gene expression for the development and maintenance of homeostasis across a wide array of tissues, including the cardiovascular system. Over the last decade, numerous studies have revealed an interplay between miRNAs and the mTOR signaling circuit in the different cardiovascular pathophysiology, like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation, and atherosclerosis. In this review, we provide a comprehensive state of the current knowledge regarding the mechanisms of interactions between the mTOR signaling pathway and miRs. We have also highlighted the latest advances on mTOR-targeted therapy in clinical trials and the new perspective therapeutic strategies with mTOR-targeting miRs in cardiovascular diseases.

Cell size sensing in animal cells coordinates anabolic growth rates and cell cycle progression to maintain cell size uniformity

Cell size uniformity in healthy tissues suggests that control mechanisms might coordinate cell growth and division. We derived a method to assay whether cellular growth rates depend on cell size, by monitoring how variance in size changes as cells grow. Our data revealed that, twice during the cell cycle, growth rates are selectively increased in small cells and reduced in large cells, ensuring cell size uniformity. This regulation was also observed directly by monitoring nuclear growth in live cells. We also detected cell-size-dependent adjustments of G1 length, which further reduce variability. Combining our assays with chemical/genetic perturbations confirmed that cells employ two strategies, adjusting both cell cycle length and growth rate, to maintain the appropriate size. Additionally, although Rb signaling is not required for these regulatory behaviors, perturbing Cdk4 activity still influences cell size, suggesting that the Cdk4 pathway may play a role in designating the cell’s target size.

Animal cells come in many different sizes. In humans, for example, egg cells are thousands of times larger than sperm cells. Yet cells of any given type are often strikingly similar in size. The cells that line the surface of organs including the skin and kidneys are especially uniform; in fact a loss of size uniformity in certain tumors is a sign of malignancy. What kind of regulation could enable separate cells within a tissue to have the same size?

One possibility is that each type of cell is programmed with a specific target size, and that a cell can sense if it strays from its target and take steps to compensate. Animal cells sensing their own size was first reported in the 1960s, and now Ginzberg et al. confirm that human cells grown in the laboratory do indeed monitor their size and correct deviations from their target. It turns out that two separate and independent processes help to keep all the cells in the population roughly uniform in size. Firstly, proliferating human cells that are smaller than their target size spend longer growing before they divide. Secondly, at two time points between cell divisions, large cells adjust their growth rate such that they grow slower than small cells.

To show these processes in action, Ginzberg et al. introduced mutations or chemicals that perturbed the length of time between cell divisions or the rate of a cell’s growth. As expected, most of these perturbations had only a modest influence on cell size, due to the cell’s compensatory strategies. Cells that had less time to grow compensated by more quickly making new protein molecules, meaning that they still had enough material to build two new cells by the time they had to divide. In contrast, if a cell’s division was artificially delayed, it reduced its growth rate to stop it from becoming too large. Similarly, cells grown in conditions that slow the production of proteins extended the time between their cell divisions to give them enough time to accumulate the material required for two new cells.

In a recent related study, Liu, Ginzberg et al. identified some of the molecules that a human cell uses to sense its own size. Together these two studies now pave the road to answering a fundamental question in cell biology: what is the elusive cell size sensor? Understanding how cells sense their size will open a window onto how quantitative information is programmed, sensed and communicated within living cells. These findings will shed also new light onto how cells specialize into cell types of different sizes, and what happens when cells lose the ability to sense or regulate their size in diseases like cancers.

Molecular determinants of Drosophila immunophilin FKBP39 nuclear localization

FK506-binding proteins (FKBPs) belong to a distinct class of immunophilins that interact with immunosuppressants. They use their peptidyl-prolyl isomerase (PPIase) activity to catalyze the cis-trans conversion of prolyl bonds in proteins during protein-folding events. FKBPs also act as a unique group of chaperones. The Drosophila melanogaster peptidyl-prolyl cis-trans isomerase FK506-binding protein of 39 kDa (FKBP39) is thought to act as a transcriptional modulator of gene expression in 20-hydroxyecdysone and juvenile hormone signal transduction. The aim of this study was to analyze the molecular determinants responsible for the subcellular distribution of an FKBP39-yellow fluorescent protein (YFP) fusion construct (YFP-FKBP39). We found that YFP-FKBP39 was predominantly nucleolar. To identify the nuclear localization signal (NLS), a series of YFP-tagged FKBP39 deletion mutants were prepared and examined in vivo. The identified NLS signal is located in a basic domain. Detailed mutagenesis studies revealed that residues K188 and K191 are crucial for the nuclear targeting of FKBP39 and its nucleoplasmin-like (NPL) domain contains the sequence that controls the nucleolar-specific translocation of the protein. These results show that FKBP39 possesses a specific NLS in close proximity to a putative helix-turn-helix (HTH) motif and FKBP39 may bind DNA in vivo and in vitro.

Pathology of Calcineurin and Mammalian Target of Rapamycin Inhibitors in Kidney Transplantation

The recent evolution in immunosuppression therapy has led to significant improvement in short-term kidney allograft outcomes; however, this progress did not translate into similar improvement in long-term graft survival. The latter, at least in part, is likely to be attributed to immunosuppressant side effects. In this review, we focus on the histologic manifestations of calcineurin inhibitor and mammalian target of rapamycin inhibitor toxicity. We discuss the pathologic features attributed to such toxicity and allude to the lack of highly specific pathognomonic lesions. Finally, we highlight the importance of clinicopathologic correlation to achieve a meaningful pathologic interpretation.

Use of multitarget tyrosine kinase inhibitors to attenuate platelet-derived growth factor signalling in lung disease

Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) play a fundamental role in the embryonic development of the lung. Aberrant PDGF signalling has been documented convincingly in a large variety of pulmonary diseases, including idiopathic pulmonary arterial hypertension, lung cancer and lung fibrosis. Targeting PDGF signalling has been proven to be effective in these diseases. In clinical practice, the most effective way to block PDGF signalling is to inhibit the activity of the intracellular PDGFR kinases. Although the mechanism of action of such drugs is not specific for PDGF signalling, the medications have a broad therapeutic index that allows clinical use. The safety profile and therapeutic opportunities of these and future medications that target PDGFs and PDGFRs are reviewed.

An increasing role for PDGF signalling inhibitors in clinical trials for the treatment of various pulmonary diseaseshttp://ow.ly/buaI30f9HcN

WITHDRAWN: MicroRNA-99a Suppresses Proliferation, Migration, Invasion and Induces G1-phase Cell Cycle Arrest via Targeting Insulin-like Growth Factor 1 Receptor Pathway in Renal Cell Carcinoma 786-0 and OS-RC-2 Cells

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Systemic Immunomodulatory Strategies in High-risk Corneal Transplantation

The cornea is the most commonly transplanted tissue in the body. Although corneal grafts generally have high success rates, transplantation onto inflamed and vascularized host beds, or so-called high-risk corneal transplantation, has a high rate of graft rejection. The management of this high-risk corneal transplantation is challenging and involves numerous measures. One of the key measures to prevent graft rejection in these cases is the use of systemic immunosuppressive agents. In this article, we will review the systemic immunosuppressive agents most commonly used for high-risk corneal transplantation, which include corticosteroids, cysclosporine A, tacrolimus, mycophenolate mofetil, and rapamycin. Benefits, risks, and published data on the use of these medications for high-risk corneal transplantation will be detailed. We will also summarize novel immunoregulatory approaches that may be used to prevent graft rejection in high-risk corneal transplantation.

Everolimus (RAD001) ameliorates vascular cognitive impairment by regulating microglial function via the mTORC1 signaling pathway

Vascular dementia (VaD) is a widely prevalent and devastating disease. Despite the tremendous complexity that limits understanding of the pathophysiology of VaD, microglial dysfunction has been attributed, in part, to immune microenviroment disorder and finally leads to cognitive deficits. Considered the mammalian target of rapamycin complex 1 (mTORC1) is a key player in regulation of glial function, our work focused on whether the mTOR inhibitor everolimus (RAD001) could overcome the destructive microglial function, change the phenotype and ameliorate cognitive decline induced by chronic cerebral hypoperfusion. Strikingly, the results suggest that inhibition of the mTORC1 activity by RAD001 ameliorates VaD by restoring microglia's M1/M2 balance. Therefore, RAD001 may have promise as a therapy for VaD disease.

Melanoma Differentiation-associated Gene 7/IL-24 Exerts Cytotoxic Effects by Altering the Alternative Splicing of Bcl-x Pre-mRNA via the SRC/PKCδ Signaling Axis

Melanoma differentiation-associated gene 7 (MDA-7/IL-24) exhibits cytotoxic effects on tumor cells while sparing untransformed cells, and Bcl-x(L) is reported to efficiently block the induction of cell death by MDA-7/IL-24. The expression of Bcl-x(L) is regulated at the level of RNA splicing via alternative 5' splice site selection within exon 2 to produce either the pro-apoptotic Bcl-x(s) or the anti-apoptotic Bcl-x(L). Our laboratory previously reported that Bcl-x RNA splicing is dysregulated in a large percentage of human non-small cell lung cancer (NSCLC) tumors. Therefore, we investigated whether the alternative RNA splicing of Bcl-x pre-mRNA was modulated by MDA-7/IL-24, which would suggest that specific NSCLC tumors are valid targets for this cytokine therapy. Adenovirus-delivered MDA-7/IL-24 (Ad.mda-7) reduced the viability of NSCLC cells of varying oncogenotypes, which was preceded by a decrease in the ratio of Bcl-x(L)/Bcl-x(s) mRNA and Bcl-x(L) protein expression. Importantly, both the expression of Bcl-x(L) and the loss of cell viability were "rescued" in Ad.mda-7-treated cells incubated with Bcl-x(s) siRNA. In addition, NSCLC cells ectopically expressing Bcl-x(s) exhibited significantly reduced Bcl-x(L) expression, which was again restored by Bcl-x(s) siRNA, suggesting the existence of a novel mechanism by which Bcl-x(s) mRNA restrains the expression of Bcl-x(L). In additional mechanistic studies, inhibition of SRC and PKCδ completely ablated the ability of MDA-7/IL-24 to reduce the Bcl-x(L)/(s) mRNA ratio and cell viability. These findings show that Bcl-x(s) expression is an important mediator of MDA-7/IL-24-induced cytotoxicity requiring the SRC/PKCδ signaling axis in NSCLC cells.

PLD1 activation mediates Amb a 1-induced Th2-associated cytokine expression via the JNK/ATF-2 pathway in BEAS-2B cells

The purpose of this study was to identify the role of phospholipase D1 (PLD1) in Amb a 1-induced IL-5 and IL-13 expression. When BEAS-2B cells were stimulated with Amb a 1, PLD activity increased, and knockdown of PLD1 decreased Amb a 1-induced IL-5 and IL-13 expression. Amb a 1 also activated the PLCγ/p70S6K/JNK pathway. Furthermore, Amb a 1-induced PLD activation was also attenuated by PLCγ inhibition, and knockdown of PLD1 decreased Amb a 1-induced activation of P70S6K and JNK. When ATF-2 activity was blocked with ATF-2 siRNA, Amb a 1-induced IL-5 and IL-13 expression was completely abolished, indicating that ATF-2 is a transcriptional factor required for the expression of IL-5 and IL-13 in response to Amb a 1. Taken together, we suggest that PLD1 acts as an important regulator in Amb a 1-induced expression of IL-5 and IL-13 via a PLCγ/p70S6K/JNK/ATF-2 pathway in BEAS-2B cells.

Recent treatment advances and novel therapeutic approaches in epilepsy

The purpose of this article is to review recent advances in the treatment of epilepsy. It includes five antiepileptic drugs that have been recently added to the pharmacologic armamentarium and surgical techniques that have been developed in the last few years. Finally, we review ongoing research that may have a potential role in future treatments of epilepsy.

Caerulomycin A suppresses immunity by inhibiting T cell activity

BACKGROUND

Caerulomycin A (CaeA) is a known antifungal and antibiotic agent. Further, CaeA is reported to induce the expansion of regulatory T cell and prolongs the survival of skin allografts in mouse model of transplantation. In the current study, CaeA was purified and characterized from a novel species of actinomycetes, Actinoalloteichus spitiensis. The CaeA was identified for its novel immunosuppressive property by inhibiting in vitro and in vivo function of T cells.

METHODS

Isolation, purification and characterization of CaeA were performed using High Performance Flash Chromatography (HPFC), NMR and mass spectrometry techniques. In vitro and in vivo T cell studies were conducted in mice using flowcytometry, ELISA and thymidine-[methyl-(3)H] incorporation.

RESULTS

CaeA significantly suppressed T cell activation and IFN-γ secretion. Further, it inhibited the T cells function at G1 phase of cell cycle. No apoptosis was noticed by CaeA at a concentration responsible for inducing T cell retardation. Furthermore, the change in the function of B cells but not macrophages was observed. The CaeA as well exhibited substantial inhibitory activity in vivo.

CONCLUSION

This study describes for the first time novel in vitro and in vivo immunosuppressive function of CaeA on T cells and B cells. CaeA has enough potential to act as a future immunosuppressive drug.

Kinetics of rapamycin production by Streptomyces hygroscopicus MTCC 4003

Research work was carried out to describe the kinetics of cell growth, substrate consumption and product formation in batch fermentation of rapamycin using shake flask as well as laboratory-scale fermentor. Fructose was used as the sole carbon source in the fermentation media. Optimization of fermentation parameters and reliable mathematical models were used for the maximum production of rapamycin from Streptomyces hygroscopicus MTCC 4003. The experimental data for microbial production of rapamycin fitted well with the proposed mathematical models. Kinetic parameters were evaluated using best fit unstructured models, viz. Andrew's model, Monod model, Yano model, Aiba model. Andrew's model showed a comparatively better R² value (0.9849) among all tested models. The values of maximum specific growth rate (μ_max), saturation constant (K_S), inhibition constant (K_i), and growth yield coefficient (Y_X/S) were found to be 0.008 (h^-1), 2.835 (g/L), 0.0738 (g/L), and 0.1708 (g g^-1), respectively. The optimum production of rapamycin was obtained at 300 rpm agitation and 1 vvm aeration rate in the fermentor. The final production of rapamycin in shake flask was 539 mg/L. Rapamycin titer found in bioreactor was 1,316 mg/L which is 52 % higher than the latest maximum value reported in the literature.

Phase I study and preclinical efficacy evaluation of the mTOR inhibitor sirolimus plus gemcitabine in patients with advanced solid tumours

Background:

We conducted a phase I study in patients with advanced solid tumours to identify the recommended dose, assess pharmacokinetics (PK), pharmacodynamic activity and preclinical antitumour efficacy of the combination of sirolimus and gemcitabine.

Methods:

Nineteen patients were treated with sirolimus 2 or 5 mg daily and gemcitabine 800 or 1000 mg m⁻² on days 1 and 8. Dose escalation depended on dose-limiting toxicity (DLT) rate during the first 3-week period. Paired skin biopsies were evaluated for phosphorylated S6 (pS6) as marker of mTOR (mammalian target of rapamycin) inhibition. Pharmacokinetics and preclinical evaluation of efficacy using two different sarcoma cell lines and leiomyosarcoma xenografts were also conducted.

Results:

Three DLTs were observed: grade 3 transaminitis, grade 3 thrombocytopenia and grade 4 thrombocytopenia. Common treatment-related adverse events included anaemia, neutropenia, thrombocytopenia and transaminitis. Pharmacodynamic analyses demonstrated mTOR inhibition with sirolimus 5 mg and PK showed no influence of sirolimus concentrations on gemcitabine clearance. In vitro and in vivo studies suggested mTOR pathway hyperactivation by gemcitabine that was reversed by sirolimus. Tumour growth in leiomyosarcoma xenografts was dramatically inhibited by the treatment.

Conclusions:

Recommended dose was sirolimus 5 mg per 24 h plus gemcitabine 800 mg m⁻². Antitumour activity in preclinical sarcoma models and mTOR signalling inhibition were observed. A phase II study is currently ongoing.

mTOR signaling inhibition modulates macrophage/microglia-mediated neuroinflammation and secondary injury via regulatory T cells after focal ischemia

Signaling by the mammalian target of rapamycin (mTOR) plays an important role in the modulation of both innate and adaptive immune responses. However, the role and underlying mechanism of mTOR signaling in poststroke neuroinflammation are largely unexplored. In this study, we injected rapamycin, a mTOR inhibitor, by the intracerebroventricular route 6 h after focal ischemic stroke in rats. We found that rapamycin significantly reduced lesion volume and improved behavioral deficits. Notably, infiltration of γδ T cells and granulocytes, which are detrimental to the ischemic brain, was profoundly reduced after rapamycin treatment, as was the production of proinflammatory cytokines and chemokines by macrophages and microglia. Rapamycin treatment prevented brain macrophage polarization toward the M1 type. In addition, we also found that rapamycin significantly enhanced anti-inflammation activity of regulatory T cells (Tregs), which decreased production of proinflammatory cytokines and chemokines by macrophages and microglia. Depletion of Tregs partially elevated macrophage/microglia-induced neuroinflammation after stroke. Our data suggest that rapamycin can attenuate secondary injury and motor deficits after focal ischemia by enhancing the anti-inflammation activity of Tregs to restrain poststroke neuroinflammation.

Reduction of HIV persistence following transplantation in HIV-infected kidney transplant recipients

Chronic inflammation may contribute to human immunodeficiency virus (HIV) persistence through a number of potential pathways. We explored the impact of immunosuppressant therapy on peripheral blood measures of HIV persistence following kidney transplantation. Stored plasma and peripheral blood mononuclear cells prior to transplantation and at weeks 12, 26, 52 and 104 posttransplant were obtained from 91 transplant recipients. In a multivariate model, higher pretransplant plasma HIV RNA level (p < 0.0001) and a longer duration of follow-up posttransplant (p = 0.09) were associated with higher posttransplant plasma HIV RNA levels. A higher baseline HIV DNA (p < 0.0001) was significantly associated with higher HIV DNA levels posttransplant, while higher CD4+ T cell count (p = 0.001), sirolimus use (p = 0.04) and a longer duration of follow-up (p = 0.06) were associated with lower posttransplant HIV DNA levels. The association between sirolimus exposure and lower frequency of cells containing HIV DNA levels posttransplant suggest that the immune-modifying drugs may affect the level of HIV persistence during effect therapy. Future studies of sirolimus as a reservoir-modifying agent are warranted.

Targeted therapy for sarcomas

Sarcomas are tumors of mesenchymal origin that make up approximately 1% of human cancers. They may arise as primary tumors in either bone or soft tissue, with approximately 11,280 soft tissue tumors and 2,650 bone tumors diagnosed each year in the United States. There are at least 50 different subtypes of soft tissue sarcoma, with new ones described with ever-increasing frequency. One way to look at sarcomas is to divide them into categories on the basis of their genetic make-up. One group of sarcomas has an identifiable, relatively simple genetic signature, such as the X:18 translocation seen in synovial sarcoma or the 11:22 translocation seen in Ewing's sarcoma. These specific abnormalities often lead to the presence of fusion proteins, such as EWS-FLI1 in Ewing's sarcoma, which are helpful as diagnostic tools and may become therapeutic targets in the future. Another group of sarcomas is characterized by complex genetic abnormalities as seen in leiomyosarcoma, osteosarcoma, and undifferentiated sarcoma. It is important to keep these distinctions in mind when contemplating the development of targeted agents for sarcomas. Different abnormalities in sarcoma could be divided by tumor subtype or by the molecular or pathway abnormality. However, some existing drugs or drugs in development may interfere with or alter more than one of the presented pathways.

Anti-CD20 as the B-Cell Targeting Agent in a Combined Therapy to Modulate Anti-Factor VIII Immune Responses in Hemophilia a Inhibitor Mice

Neutralizing antibody formation against transgene products can represent a major complication following gene therapy with treatment of genetic diseases, such as hemophilia A. Although successful approaches have been developed to prevent the formation of anti-factor VIII (FVIII) antibodies, innovative strategies to overcome pre-existing anti-FVIII immune responses in FVIII-primed subjects are still lacking. Anti-FVIII neutralizing antibodies circulate for long periods in part due to persistence of memory B-cells. Anti-CD20 targets a variety of B-cells (pre-B-cells to mature/memory cells); therefore, we investigated the impact of B-cell depletion on anti-FVIII immune responses in hemophilia A mice using anti-CD20 combined with regulatory T (Treg) cell expansion using IL-2/IL-2mAb complexes plus rapamycin. We found that anti-CD20 alone can partially modulate anti-FVIII immune responses in both unprimed and FVIII-primed hemophilia A mice. Moreover, in mice treated with anti-CD20+IL-2/IL-2mAb complexes+rapamycin+FVIII, anti-FVIII antibody titers were significantly reduced in comparison to mice treated with regimens targeting only B or T cells. In addition, titers remained low after a second challenge with FVIII plasmid. Treg cells and activation markers were transiently and significantly increased in the groups treated with IL-2/IL-2mAb complexes; however, significant B-cell depletion was obtained in anti-CD20-treated groups. Importantly, both FVIII-specific antibody-secreting cells and memory B-cells were significantly reduced in mice treated with combination therapy. This study demonstrates that a combination regimen is highly promising as a treatment option for modulating anti-FVIII antibodies and facilitating induction of long-term tolerance to FVIII in hemophilia A mice.

Rapamycin induces ILT3(high)ILT4(high) dendritic cells promoting a new immunoregulatory pathway

ILT3(high)ILT4(high) dendritic cells (DCs) may cause anergy in CD4(+)CD45RO(+)CD25(+) T cells transforming them into regulatory T cells (Tregs). Here, we tested whether chronic exposure to rapamycin may modulate this immunoregulatory pathway in renal transplant recipients. Forty renal transplant patients with biopsy-proven chronic allograft nephropathy and receiving calcineurin inhibitors were randomly assigned to either calcineurin inhibitor dose reduction or withdrawal with rapamycin introduction. At conversion and 2 years thereafter, we measured the rapamycin effects on circulating DCs (BDCA1/BDCA2 and ILT3/ILT4 expression), CD4(+)/CD25(high)/Foxp3(+) Tregs, CD8(+)/CD28(-) T cells, and the Th1/Th2 balance in graft biopsies. In rapamycin-treated patients, peripheral BDCA2(+) cells were significantly increased along with ILT3/ILT4(+) DCs. The number of circulating CD4(+)/CD25(high)/Foxp3(+)/CTLA4(+) Tregs, CD8(+)CD28(-) T cells, and HLA-G serum levels were higher in the rapamycin-treated group. The number of ILT3/ILT4(+)BDCA2(+) DC was directly and significantly correlated with circulating Tregs and CD8(+)CD28(-) T cells. ILT3/ILT4 expression was increased in kidney biopsies at the end of the study period along with a significant bias toward a Th2 response within the graft only in the rapamycin-treated patients. Thus, rapamycin induces the upregulation of ILT3 and ILT4 on the DC surface, and this effect is associated with an increase in the number of Tregs and expansion of the CD8(+)CD28(-) T cell population. This suggests that mTOR inhibition may promote a novel immunoregulatory pathway.

Biotic acts of antibiotics

Biological functions of antibiotics are not limited to killing. The most likely function of antibiotics in natural microbial ecosystems is signaling. Does this signaling function of antibiotics also extend to the eukaryotic – in particular mammalian – cells? In this review, the host modulating properties of three classes of antibiotics (macrolides, tetracyclines, and β-lactams) will be briefly discussed. Antibiotics can be effective in treatment of a broad spectrum of diseases and pathological conditions other than those of infectious etiology and, in this capacity, may find widespread applications beyond the intended antimicrobial use. This use, however, should not compromise the primary function antibiotics are used for. The biological background for this inter-kingdom signaling is also discussed.

Inhibition of the mitochondrial Hsp90 chaperone network: a novel, efficient treatment strategy for cancer?

Research has shown that cancer cells exhibit multiple deregulated pathways, involving proliferation, migration and cell death. Heat-shock-proteins have evolved as "central regulators" and are implicated in the modulation of these pathways and in organelle-specific signaling. In this instance, heat-shock-proteins (Hsps) assist cancer cells in the maturation of proteins. Hsp90 is of particular interest because its enzymatic ATPase activity is elevated in malignant cells as compared to non-neoplastic counterparts. Consistent with its high-activity in cancer cells, Hsp90 stabilizes a considerable number of proteins being instrumental in carcinogenesis and the maintenance and growth of highly malignant cancers. Among its distribution Hsp90 is also localized within mitochondria of neoplastic cells of various origin, interacting with another chaperone, TRAP1 (Tumor necrosis factor type 1 receptor-associated protein or Heat-shock-protein 75) to antagonize the cell death promoting properties of the matrix protein, Cyclophilin-D. Several preclinical studies, including in vivo studies in both orthotopic and genetic animal models, have confirmed that targeting mitochondrial Hsp90 may be a novel efficient treatment method for highly recalcitrant tumors. This review summarizes the most recent findings of mitochondrial Hsp90 signaling and its potential implications for cancer therapy.

Targeting the PI3K/Akt/mTOR pathway for breast cancer therapy

Recent advances in genetics and genomics have revealed new pathways that are aberrantly activated in many breast cancers. Chief among these genetic changes are somatic mutations and/or gains and losses of key genes within the phosphoinositide 3-kinase (PI3K) pathway. Since breast cancer cell growth and progression is often dependent upon activation of the PI3K pathway, there has been intense research interest in finding therapeutic agents that can selectively inhibit one or more constituents of this signaling cascade. Here we review key molecules involved with aberrant PI3K pathway activation in breast cancers and current efforts to target these components for therapeutic gain.

Cross talk between estradiol and mTOR kinase in the regulation of ovarian granulosa proliferation

Treatment of ovarian granulosa cells and follicles with the mammalian target of rapamycin (mTOR) kinase inhibitor results in biphasic effects where nanomolar rapamycin (RAP) results in reduced proliferation, mitotic anomalies, and attenuated follicle growth, while the picomolar RAP results in accelerated follicle growth. Here, we tested whether such effects are specific to RAP or could be mimicked by 2 alternative mTOR inhibitors, everolimus (EV) and temsirolimus (TEM), and whether these effects were dependent on the presence of estradiol (E2). Spontaneously immortalized rat granulosa cells (SIGCs) were cultured in dose curves of RAP, EV, TEM, or vehicle with or without E2. Proliferation and phosphorylation of mTOR targets p70S6 kinase and 4E-binding protein (BP) were determined. Cell cycle gene array analysis and confirmatory quantitative reverse transcriptase polymerase chain reaction were performed upon cells treated with picomolar RAP versus controls. Nanomolar RAP, EV, and TEM reduced SIGC proliferation and decreased phospho-p70 and 4E-BP. Picomolar concentrations accelerated proliferation without affecting mTOR substrate phosphorylation. Acceleration of growth by picomolar inhibitor required E2. Picomolar drug treatment altered the transcription of cell cycle regulators, increasing Integrin beta 1 and calcineurin expression, and decreasing inhibin alpha, Chek1, p16ARF, p27/Kip1, and Sestrin2 expression. At nanomolar concentrations, mTOR inhibitors attenuated granulosa proliferation. Accelerated growth and alterations in cell cycle gene transcription found with picomolar concentrations required E2 within the intrafollicular concentration range. The low concentrations of inhibitors required to increase granulosa proliferation suggest a novel use to support the growth of ovarian follicles.

The inhibitory effect of rapamycin on the oval cell response and development of preneoplastic foci in the rat

Oval cell activation occurs under conditions of severe liver injury when normal hepatocyte proliferation is blocked. Recent studies have shown that a subset of hepatocellular carcinomas expresses oval cell markers, suggesting that these cells are targets of hepatocarcinogens. However, the signaling pathways that control oval cell activation and proliferation are not well characterized. Based on the role of the nutrient signaling kinase complex, mTORC1, in liver development, we investigated the role of this pathway in oval cell activation. Oval cell proliferation was induced in male Fisher rats by a modification of the traditional choline deficient plus ethionine model (CDE) or by 2-acetylaminoflourene treatment followed by 2/3 partial hepatectomy with or without initiation by diethylnitrosamine. To assess the role of mTOR in the oval cell response and development of preneoplastic foci, the effect of the mTORC1 inhibitor, rapamycin, was studied in all models. Rapamycin induced a significant suppression of the oval cell response in both models, an effect that coincided with a decrease in oval cell proliferation. Rapamycin administration did not affect the abundance of neutrophils or natural killer cells in CDE-treated liver or the expression of key cytokines. Gene expression studies revealed the fetal hepatocyte marker MKP-4 to be expressed in oval cells. In an experimental model of hepatic carcinogenesis, rapamycin decreased the size of preneoplastic foci and the rate of cell proliferation within the foci. mTORC1 signaling plays a key role in the oval cell response and in the development of preneoplastic foci. This pathway may be a target for the chemoprevention of hepatocellular carcinoma.

Gastric cancer cell lines AGS before and after CD40 signal activating

The aim of this study was to investigate the molecular mechanisms underlying the antitumour effects of CD40L through analysing the change of genes expression profile in AGS using Affymetrix Gene Chip. Human gastric carcinoma AGS cells were first incubated with 2 μg/ml sCD40L or equal volume of medium (control) in F12 medium. RNA was isolated from AGS and were reverse transcribed, labeled with digoxigenin-11-dUTP, and then hybridized with Clontech Atlas mouse cDNA expression arrays for comparison. Performing clustering analysis, we found that 7 detected genes were down-regulated and 38 were upregulated as the sCD40L acted on AGS. To further verify the results of gene chip screening, Gene Database was searched, finding that the most significantly up-regulated genes were Gadd45a, c-Jun and Bcl-2, and the most significantly down-regulated genes were Cyclin D1, CDC6, TNFR10B, c-IAP2 and ORC5L. Based upon these findings, the signalling pathways that possibly mediate CD40-induced apoptosis are proposed.

Should diabetic women with breast cancer have their own intervention studies?

This commentary on 'Calorie restriction and rapamycin inhibit MMTV-Wnt-1 mammary tumor growth in a mouse model of postmenopausal obesity' by Nogueira et al., published in this issue of Endocrine-Related Cancer, addresses the challenges of translating diet, exercise, and pharmacologic trials in diabetic mouse mammary tumor models to human studies. We propose that trials specifically designed to test such interventions in diabetic women with breast cancer would be valuable and informative.