Oncogenic Ras pushes (and pulls) cell cycle progression through ERK activation

NF1 deficiency drives metabolic reprogramming in ER+ breast cancer

OBJECTIVE

NF1 is a tumor suppressor gene and its protein product, neurofibromin, is a negative regulator of the RAS pathway. NF1 is one of the top driver mutations in sporadic breast cancer such that 27 % of breast cancers exhibit damaging NF1 alterations. NF1 loss-of-function is a frequent event in the genomic evolution of estrogen receptor (ER)+ breast cancer metastasis and endocrine resistance. Individuals with Neurofibromatosis type 1 (NF) - a disorder caused by germline NF1 mutations - have an increased risk of dying from breast cancer [1-4]. NF-related breast cancers are associated with decreased overall survival compared to sporadic breast cancer. Despite numerous studies interrogating the role of RAS mutations in tumor metabolism, no study has comprehensively profiled the NF1-deficient breast cancer metabolome to define patterns of energetic and metabolic reprogramming. The goals of this investigation were (1) to define the role of NF1 deficiency in estrogen receptor-positive (ER+) breast cancer metabolic reprogramming and (2) to identify potential targeted pathway and metabolic inhibitor combination therapies for NF1-deficient ER + breast cancer.

METHODS

We employed two ER+ NF1-deficient breast cancer models: (1) an NF1-deficient MCF7 breast cancer cell line to model sporadic breast cancer, and (2) three distinct, Nf1-deficient rat models to model NF-related breast cancer [1]. IncuCyte proliferation analysis was used to measure the effect of NF1 deficiency on cell proliferation and drug response. Protein quantity was assessed by Western Blot analysis. We then used RNAseq to investigate the transcriptional effect of NF1 deficiency on global and metabolism-related transcription. We measured cellular energetics using Agilent Seahorse XF-96 Glyco Stress Test and Mito Stress Test assays. We performed stable isotope labeling and measured [U-13C]-glucose and [U-13C]-glutamine metabolite incorporation and measured total metabolite pools using mass spectrometry. Lastly, we used a Bliss synergy model to investigate NF1-driven changes in targeted and metabolic inhibitor synergy.

RESULTS

Our results revealed that NF1 deficiency enhanced cell proliferation, altered neurofibromin expression, and increased RAS and PI3K/AKT pathway signaling while constraining oxidative ATP production and restricting energetic flexibility. Neurofibromin deficiency also increased glutamine influx into TCA intermediates and dramatically increased lipid pools, especially triglycerides (TG). Lastly, NF1 deficiency alters the synergy between metabolic inhibitors and traditional targeted inhibitors. This includes increased synergy with inhibitors targeting glycolysis, glutamine metabolism, mitochondrial fatty acid transport, and TG synthesis.

CONCLUSIONS

NF1 deficiency drives metabolic reprogramming in ER+ breast cancer. This reprogramming is characterized by oxidative ATP constraints, glutamine TCA influx, and lipid pool expansion, and these metabolic changes introduce novel metabolic-to-targeted inhibitor synergies.

ADAM17 regulates the proliferation and extracellular matrix of keloid fibroblasts by mediating the EGFR/ERK signaling pathway

To investigate the role of a disintegrin and metalloprotease protein 17 (ADAM17) in regulating the proliferation and extracellular matrix (ECM) expression of keloid fibroblasts (KFs) via the epidermal growth factor receptor (EGFR)/extracellular signal-regulated kinase (ERK) pathway. ADAM17 expression in keloid tissues was detected by western blotting. KFs were isolated, cultured and divided into the control, shNC (negative control), shADAM17, transforming growth factor-β1 (TGF-β1), TGF-β1 + shNC and TGF-β1 + shADAM17 groups. The expression of ECM was detected by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Western blotting was performed to detect the expression of proteins. Cell proliferation was detected by a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, while cell invasion and migration were examined by Transwell and wound healing assays. The expression of ADAM17 was increased in keloid tissues and KFs. Compared with the control group, the expression of p-EGFR and p-ERK/1/2/ERK1/2, as well as the expression of collagen I, collagen III, connective tissue growth factor (CTGF) and α-smooth muscle actin (α-SMA), were decreased in KFs from the shADAM17 group, with decreased cell proliferation, invasion and migration. In contrast, the TGF-β1 group presented the opposite trend in these aspects. In addition, compared with the TGF-β1 group, KFs from the TGF-β1 + shADAM17 group had decreased ECM expression, proliferation, invasion and migration. ADAM17 expression was upregulated in keloid tissues. Silencing ADAM17 may inhibit the activity of the EGFR/ERK pathway to limit the deposition of ECM in KFs with reduced proliferation, invasion and migration.

RASless MEFs as a Tool to Study RAS-Dependent and RAS-Independent Functions

RAS proteins are key players in multiple cellular processes. To study the role of RAS proteins individually or in combination, we have developed MEFs that can be rendered RASless, i.e., devoid of all endogenous RAS isoforms. These cells have significantly contributed to our understanding of the requirements for RAS functions in cell proliferation as well as their implications in diverse cellular processes. Here, we describe methods using RASless MEFs to study RAS-dependent cellular activities with special emphasis on proliferation. We provide the details to identify inducers of RAS-independent proliferation in colony assays. We recommend following these stringent guidelines to avoid false-positive results. Moreover, this protocol can be adapted to generate RASless MEFs ectopically expressing RAS variants to interrogate their function in the absence of endogenous RAS isoforms or to perform experiments in the absence of RAS. Finally, we also describe protocols to generate and use RASless MEFs for cell cycle analyses using the FUCCI cell cycle indicator.

Essential role of Salmonella Enteritidis DNA adenine methylase in modulating inflammasome activation

Background

Salmonella Enteritidis (SE) is one of the major foodborne zoonotic pathogens of worldwide importance which can induce activation of NLRC4 and NLRP3 inflammasomes during infection. Given that the inflammasomes play an essential role in resisting bacterial infection, Salmonella has evolved various strategies to regulate activation of the inflammasome, most of which largely remain unclear.

Results

A transposon mutant library in SE strain C50336 was screened for the identification of the potential factors that regulate inflammasome activation. We found that T3SS-associated genes invC, prgH, and spaN were required for inflammasome activation in vitro. Interestingly, C50336 strains with deletion or overexpression of Dam were both defective in activation of caspase-1, secretion of IL-1β and phosphorylation of c-Jun N-terminal kinase (Jnk). Transcriptome sequencing (RNA-seq) results showed that most of the differentially expressed genes and enriched KEGG pathways between the C50336-VS-C50336Δdam and C50336-VS-C50336::dam groups overlapped, which includes multiple signaling pathways related to the inflammasome. C50336Δdam and C50336::dam were both found to be defective in suppressing the expression of several anti-inflammasome factors. Moreover, overexpression of Dam in macrophages by lentiviral infection could specifically enhance the activation of NLRP3 inflammasome independently via promoting the Jnk pathway.

Conclusions

These data indicated that Dam was essential for modulating inflammasome activation during SE infection, there were complex and dynamic interplays between Dam and the inflammasome under different conditions. New insights were provided about the battle between SE and host innate immunological mechanisms.

FABP7 promotes cell proliferation and survival in colon cancer through MEK/ERK signaling pathway

Colon cancer (CC), one of the most frequently diagnosed malignancies deriving from the digestive system, has greatly threatened human health and life. Fatty acid binding protein 7 (FABP7), an intracellular protein with the tissue-specific expression pattern, has been reported to be implicated in diverse types of human tumors. However, the biological role of FABP7 in CC is still poorly understood. The current study aimed to investigate the role of FABP7 in CC and illuminate the potential molecular mechanisms. In this present study, we found that FABP7 was highly expressed in CC tissues and cell lines, suggesting the possible involvement of FABP7 in CC tumorigenesis. Moreover, functional investigations showed that FABP7-overexpression promoted CC cell proliferation, colony formation, cell cycle progression and inhibited cell apoptosis; on the contrary, FABP7 knockdown produced an inhibitory effects on CC cell proliferation and survival. Notably, FABP7 knockdown inhibited colon tumor growth in vivo. In addition, mechanistic investigations demonstrated that FABP7 exerted its promoting effects on CC cell proliferation and survival through activation of the MEK/ERK signaling pathway. Collectively, our data indicate that FABP7 may be used as a novel diagnostic bio-marker and a potential therapeutic target for CC.

BRAF inhibitors stimulate inflammasome activation and interleukin 1 beta production in dendritic cells

Melanoma is the most dangerous form of skin cancer with a growing incidence over the last decades. Fourty percent of all melanomas harbor a mutation in the signaling adaptor BRAF (V600E) that results in ERK hyperactivity as an oncogenic driver. In these cases, treatment with the BRAF^V600E inhibitors Vemurafenib (VEM) or Dabrafenib (DAB) coapplied with the MEK1/2 inhibitors Cobimetinib (COB) or Trametinib (TRA) can result in long-term suppression of tumor growth. Besides direct suppression of ERK activity, these inhibitors have been reported to also modulate tumor immune responses, and exert pro-inflammatory side effects such as fever and rash in some patients. Here we asked for potential effects of BRAF^V600E inhibitors on dendritic cells (DC) which are essential for the induction of adaptive anti-tumor responses. Both splenic and bone marrow-derived (BM) mouse dendritic cells (DC) up-regulated costimulator expression (CD80, CD86) in response to DAB but not VEM treatment. Moreover, DAB and to lesser extent VEM enhanced IL-1β (interleukin 1 beta) release by splenic DC, and by LPS-stimulated BMDC. We demonstrate that DAB and VEM activated the NLRC4/Caspase-1 inflammasome. At high concentration, DAB also induced inflammasome activation independent of Caspase-1. TRA and COB elevated MHCII expression on BMDC, and modulated the LPS-induced cytokine pattern. Immunomodulatory activity of DAB and VEM was also observed in human monocyte-derived DC, and DAB induced IL-1β in human primary DC. Altogether, our study shows that BRAF^V600E inhibitors upregulate IL-1β release by mouse and human DC which may affect the DC-mediated course of anti-tumor immune responses.

The Role of Tinzaparin in Oncology

Current guidelines recommend low-molecular-weight heparin treatment in patients with cancer with established venous thromboembolism (VTE). The aim of this article was to study the pharmacological properties and effectiveness of tinzaparin in patients with cancer as well as its potential anticancer properties. A search of PubMed and ScienceDirect databases up to March 2016 was carried out to identify published studies that detect the properties and use of tinzaparin in oncology. Protamine sulfate partially (60% to 65%) neutralized tinzaparin’s anti-Xa activity. No dose adjustment of tinzaparin is needed even in patients with severe renal impairment and Creatinine Clearance ≥20 mL/min. Tinzaparin demonstrated a statistically significant decline in VTE recurrence at 1 year post the index thromboembolic event. A statistically significant reduction in minor bleeding rates was also described, whereas major bleeding events did not decrease in patients with cancer treated with tinzaparin versus those who received vitamin K antagonists. Tinzaparin treatment in patients suffering from deep vein thrombosis reduced the incidence of postthrombotic syndrome and venous ulcers. Tinzaparin’s ability to prevent both metastatic dissemination of cancer cells and tumor angiogenesis has been delineated in preclinical research. Current data show that tinzaparin is safe and efficacious either for short-term or for long-term treatment of VTE in patients with cancer. Clinical trials are needed in order to examine the utility of tinzaparin in primary prevention of VTE and validate its potential anticancer advantages exhibited in preclinical research.

MiR-148a impairs Ras/ERK signaling in B lymphocytes by targeting SOS proteins

Although microRNAs have been recognized as central cellular regulators, there is an evident lack of knowledge about their targets. Here, we analyzed potential target genes for miR-148a functioning in Ras signaling in B cells, including SOS1 and SOS2. A dual-luciferase reporter assay showed significantly decreased luciferase activity upon ectopic overexpression of miR-148a in HEK-293T cells that were co-transfected with the 3′UTR of either SOS1 or SOS2. Each of the 3′UTRs of SOS1 and SOS2 contained two binding sites for miR-148a both of which were necessary for the decreased luciferase activity. MiR-148a overexpression in HEK-293T lead to significantly reduced levels of both endogenous SOS1 and SOS2 proteins. Likewise, reduced levels of SOS proteins were found in two B cell lines that were transfected with miR-148a. The level of ERK1/2 phosphorylation as one of the most relevant downstream members of the Ras/ERK signaling pathway was also reduced in cells with miR-148a overexpression. The data show that miR-148a impairs the Ras/ERK signaling pathway via SOS1 and SOS2 proteins in B cells.

The RNA-Binding Protein, Polypyrimidine Tract-Binding Protein 1 (PTBP1) Is a Key Regulator of CD4 T Cell Activation

We have previously shown that the RNA binding protein, polypyrimidine tract-binding protein (PTBP1) plays a critical role in regulating the expression of CD40L in activated CD4 T cells. This is achieved mechanistically through message stabilization at late times of activation as well as by altered distribution of CD40L mRNA within distinct cellular compartments. PTBP1 has been implicated in many different processes, however whether PTBP1 plays a broader role in CD4 T cell activation is not known. To examine this question, experiments were designed to introduce shRNA into primary human CD4 T cells to achieve decreased, but not complete ablation of PTBP1 expression. Analyses of shPTB-expressing CD4 T cells revealed multiple processes including cell proliferation, activation-induced cell death and expression of activation markers and cytokines that were regulated in part by PTBP1 expression. Although there was an overall decrease in the steady-state level of several activation genes, only IL-2 and CD40L appeared to be regulated by PTBP1 at the level of RNA decay suggesting that PTBP1 is critical at different regulatory steps of expression that is gene-specific. Importantly, even though the IL-2 protein levels were reduced in cells with lowered PTBP1, the steady-state level of IL-2 mRNA was significantly higher in these cells suggesting a block at the translational level. Evaluation of T cell activation in shPTB-expressing T cells revealed that PTBP1 was linked primarily to the activation of the PLCγ1/ERK1/2 and the NF-κB pathways. Overall, our results reveal the importance of this critical RNA binding protein in multiple steps of T cell activation.

LB100, a small molecule inhibitor of PP2A with potent chemo- and radio-sensitizing potential

Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that plays a significant role in mitotic progression and cellular responses to DNA damage. While traditionally viewed as a tumor suppressor, inhibition of PP2A has recently come to attention as a novel therapeutic means of driving senescent cancer cells into mitosis and promoting cell death via mitotic catastrophe. These findings have been corroborated in numerous studies utilizing naturally produced compounds that selectively inhibit PP2A. To overcome the known human toxicities associated with these compounds, a water-soluble small molecule inhibitor, LB100, was recently developed to competitively inhibit the PP2A protein. This review summarizes the pre-clinical studies to date that have demonstrated the anti-cancer activity of LB100 via its chemo- and radio-sensitizing properties. These studies demonstrate the tremendous therapeutic potential of LB100 in a variety of cancer types. The results of an ongoing phase 1 trial are eagerly anticipated.