Visualization of Macropinocytosis in Prostate Fibroblasts

Macropinocytosis has emerged as an important mechanism for non-selective route to internalize extracellular fluids and dissolved molecules in eukaryotic cell. As fundamental cellular behavior, macropinocytosis plays specific and distinct roles in many physiological and pathological processes, such as nutrients uptake, antigen presentation, pathogen capture, and tumorigenesis. It supports tumorigenesis by providing metabolic needs to dividing cells in Ras driven cancer. In recent years, macropinocytosis has gained considerable interest in physiology and various diseases, including cancer, neurodegenerative diseases and atherosclerosis, which in turn has led to the discovery of new endocytic recycling systems. Approaches to assess macropinocytosis will provide insight into its underlying regulatory molecular mechanisms and enable the physiological control of macropinocytosis for controlled drug delivery and targeted cancer therapy. Macropinocytosis is an important phenomenon in Ras-expressing cancer cells and, recently, we have revealed a functional role for macropinocytosis in cancer associated fibroblasts (CAFs) fueling cancer cell growth. Here, we describe a protocol for detection of macropinocytosis in prostatic fibroblasts in vitro by utilizing fluorescently-labeled, lysine-fixable, 70 kDa high molecular weight dextran. Macropinosomes are visualized as fluorescent intracellular puncta either by confocal or fluorescent microscopy. To follow, subsequent intracellular events and their underlying mechanisms after macropinosomes formation, we perform co-localization of quenched BSA (DQ™-BSA) along with dextran labeling in cancer associated fibroblasts. Our protocol provides a consistent way to understand macropinocytosis in wild type or genetic manipulated prostatic fibroblast.

Drosophila Models of Cell Polarity and Cell Competition in Tumourigenesis

Cell competition is an important surveillance mechanism that measures relative fitness between cells in a tissue during development, homeostasis, and disease. Specifically, cells that are "less fit" (losers) are actively eliminated by relatively "more fit" (winners) neighbours, despite the less fit cells otherwise being able to survive in a genetically uniform tissue. Originally described in the epithelial tissues of Drosophila larval imaginal discs, cell competition has since been shown to occur in other epithelial and non-epithelial Drosophila tissues, as well as in mammalian model systems. Many genes and signalling pathways have been identified as playing conserved roles in the mechanisms of cell competition. Among them are genes required for the establishment and maintenance of apico-basal cell polarity: the Crumbs/Stardust/Patj (Crb/Sdt/Patj), Bazooka/Par-6/atypical Protein Kinase C (Baz/Par-6/aPKC), and Scribbled/Discs large 1/Lethal (2) giant larvae (Scrib/Dlg1/L(2)gl) modules. In this chapter, we describe the concepts and mechanisms of cell competition, with emphasis on the relationship between cell polarity proteins and cell competition, particularly the Scrib/Dlg1/L(2)gl module, since this is the best described module in this emerging field.

IRF1 inhibits the proliferation and metastasis of colorectal cancer by suppressing the RAS-RAC1 pathway

Background

Interferon regulatory factor 1 (IRF1) plays a role in the immune response, cellular necrosis, DNA damage, and DNA repair, offering an attractive target for anticancer treatment. However, little is known about the role of IRF1 in the regulation of CRC progression.

Methods

Quantitative reverse transcription-PCR, Western blot, and immunohistochemistry were used to examine the expression level of IRF1; Cell Counting Kit-8, migration assay, and xenograft mouse models were used to examine the function of IRF1 in CRC cell lines; a ChIP assay was used to examine the binding between IRF1 and Ras association domain-containing protein 5 (RASSF5).

Results

IRF1 expression was lower in colorectal cancer (CRC) than in normal mucosa and the IRF1 expression level was inversely associated with CRC metastasis. In addition, IRF1 could inhibit CRC cell proliferation, migration, and metastasis in vivo and in vitro; IRF1 also induced cell cycle arrest but had no effect on cell apoptosis. IRF1 enhanced the expression of RASSF5 by increasing its promoter activity. Moreover, this study revealed a novel mechanism for inhibiting the RAS-RAC1 pathway by overexpression of RASSF5.

Conclusion

Altogether, the results indicate that IRF1, which promotes RASSF5 expression, suppresses CRC metastasis and proliferation possibly through downregulation of the RAS-RAC1 pathway.

Ras-ERK1/2 signaling contributes to the development of colorectal cancer via regulating H3K9ac

BACKGROUNDS/AIMS

Ras is a control switch of ERK1/2 pathway, and hyperactivation of Ras-ERK1/2 signaling appears frequently in human cancers. However, the molecular regulation following by Ras-ERK1/2 activation is still unclear. This work aimed to reveal whether Ras-ERK1/2 promoted the development of colorectal cancer via regulating H3K9ac.

METHODS

A vector for expression of K-Ras mutated at G12 V and T35S was transfected into SW48 cells, and the acetylation of H3K9 was measured by Western blot analysis. MTT assay, colony formation assay, transwell assay, chromatin immunoprecipitation and RT-qPCR were performed to detect whether H3K9ac was contributed to K-Ras-mediated cell growth and migration. Furthermore, whether HDAC2 and PCAF involved in modification of H3K9ac following Ras-ERK1/2 activation were studied.

RESULTS

K-Ras mutated at G12 V and T35S induced a significant activation of ERK1/2 signaling and a significant down-regulation of H3K9ac. Recovering H3K9 acetylation by using a mimicked H3K9ac expression vector attenuated the promoting effects of Ras-ERK1/2 on tumor cells growth and migration. Besides, H3K9ac can be deacetylated by HDAC2 and MDM2-depedent degradation of PCAF.

CONCLUSION

H3K9ac was a specific target for Ras-ERK1/2 signaling pathway. H3K9 acetylation can be modulated by HDAC2 and MDM2-depedent degradation of PCAF. The revealed regulation provides a better understanding of Ras-ERK1/2 signaling in tumorigenesis.

Difference in Mono-O-Glucosylation of Ras Subtype GTPases Between Toxin A and Toxin B From Clostridioides difficile Strain 10463 and Lethal Toxin From Clostridium sordellii Strain 6018

Clostridioides difficile toxin A (TcdA) and Toxin B (TcdB) trigger inflammasome activation with caspase-1 activation in cultured cells, which in turn induce the release of IL-6, IFN-γ, and IL-8. Release of these proinflammatory responses is positively regulated by Ras-GTPases, which leads to the hypothesis that Ras glucosylation by glucosylating toxins results in (at least) reduced proinflammatory responses. Against this background, data on toxin-catalyzed Ras glucosylation are required to estimate of pro-inflammatory effect of the glucosylating toxins. In this study, a quantitative evaluation of the GTPase substrate profiles glucosylated in human colonic (Caco-2) cells treated with either TcdA, TcdB, or the related Clostridium sordellii lethal toxin (TcsL) was performed using multiple reaction monitoring (MRM) mass spectrometry. (H/K/N)Ras are presented to be glucosylated by TcsL and TcdA but by neither TcdB isoform tested. Furthermore, the glucosylation of (H/K/N)Ras was detected in TcdA-(not TcdB)-treated cells, as analyzed exploiting immunoblot analysis using the Ras glucosylation-sensitive 27H5 antibody. Furthermore, [¹⁴C]glucosylation of substrate GTPase was found to be increased in a cell-free system complemented with Caco-2 lysates. Under these conditions, (H/K/N)Ras glucosylation by TcdA was detected. In contrast, TcdB-catalyzed (H/K/N)Ras glucosylation was detected by neither MRM analysis, immunoblot analysis nor [¹⁴C]glucosylation in a cell-free system. The observation that TcdA (not TcdB) glucosylates Ras subtype GTPases correlates with the fact that TcdB (not TcdA) is primarily responsible for inflammatory responses in CDI. Finally, TcsL more efficaciously glucosylated Ras subtype GTPase as compared with TcdA, reinforcing the paradigm that TcsL is the prototype of a Ras glucosylating toxin.

The Signaling Network Controlling C. elegans Vulval Cell Fate Patterning

EGF, emitted by the Anchor Cell, patterns six equipotent C. elegans vulval precursor cells to assume a precise array of three cell fates with high fidelity. A group of core and modulatory signaling cascades forms a signaling network that demonstrates plasticity during the transition from naïve to terminally differentiated cells. In this review, we summarize the history of classical developmental manipulations and molecular genetics experiments that led to our understanding of the signals governing this process, and discuss principles of signal transduction and developmental biology that have emerged from these studies.

Ras-Dependent Cell Fate Decisions Are Reinforced by the RAP-1 Small GTPase in Caenorhabditiselegans

The notoriety of the small GTPase Ras as the most mutated oncoprotein has led to a well-characterized signaling network largely conserved across metazoans. Yet the role of its close relative Rap1 (Ras Proximal), which shares 100% identity between their core effector binding sequences, remains unclear. A long-standing controversy in the field is whether Rap1 also functions to activate the canonical Ras effector, the S/T kinase Raf. We used the developmentally simpler Caenorhabditis elegans, which lacks the extensive paralog redundancy of vertebrates, to examine the role of RAP-1 in two distinct LET-60/Ras-dependent cell fate patterning events: induction of 1° vulval precursor cell (VPC) fate and of the excretory duct cell. Fluorescence-tagged endogenous RAP-1 is localized to plasma membranes and is expressed ubiquitously, with even expression levels across the VPCs. RAP-1 and its activating GEF PXF-1 function cell autonomously and are necessary for maximal induction of 1° VPCs. Critically, mutationally activated endogenous RAP-1 is sufficient both to induce ectopic 1°s and duplicate excretory duct cells. Like endogenous RAP-1, before induction GFP expression from the pxf-1 promoter is uniform across VPCs. However, unlike endogenous RAP-1, after induction GFP expression is increased in presumptive 1°s and decreased in presumptive 2°s. We conclude that RAP-1 is a positive regulator that promotes Ras-dependent inductive fate decisions. We hypothesize that PXF-1 activation of RAP-1 serves as a minor parallel input into the major LET-60/Ras signal through LIN-45/Raf.

Ras activation in retinal progenitor cells induces tumor formation in the eye

The RAS gene family members, H-RAS, K-RAS, and N-RAS, are frequently mutated in human cancer. A subset of retinal tumors displays K-RAS mutations; however, the specific role of RAS activation on retinal tumor formation is unclear. To examine the role of RAS in retinal development, we overexpressed the mutant H-RAS gene (G12V) in retinal progenitor cells (RPCs), a multipotent progenitor cell population that gives rise to all six neuron types in the retina and to the Muller glia. The Msi1^CreER mouse strain was used to induce mosaic activation of Ras (RasV12) in the RPCs of the postnatal retina. RAS-activated RPCs translocated to the basal part of the retina, differentiated into cells with glial characteristics, and underwent apoptosis. We next induced RAS activation in a large population of RPCs in the embryonic retina using the Pax6^Cre mouse strain. In contrast to the phenotype observed in Msi1^CreER;RasV12 mice, Ras-activated cells retained their apical attachment. Basal translocation was partially suppressed in the retina of Pax6^Cre;RasV12 mice, indicating that basal translocation of Ras-activated cells was not cell autonomous. Notably, RAS-activated retinal cells were highly proliferative and promoted the formation of eye tumors in Pax6^Cre;RasV12 mice. Together, our data indicate that the tumorigenicity of RAS activation in RPCs is context dependent, with tumor formation occurring when RAS activity is present in a large cluster of embryonic RPCs.

Pituitary somatolactotropes evade an oncogenic response to Ras

Distinct cell types have been shown to respond to activated Ras signaling in a cell-specific manner. In contrast to its pro-tumorigenic role in some human epithelial cancers, oncogenic Ras triggers differentiation of pheochromocytoma cells and medullary thyroid carcinoma cells. Furthermore, we have previously demonstrated that in pituitary somatolactotropes, activated Ras promotes differentiation and is not sufficient to drive tumorigenesis. These findings demonstrate that lactotrope cells have the ability to evade the tumorigenic fate that is often associated with persistent activation of Ras/ERK signaling, and suggest that there may be differential expression of inhibitory signaling molecules or negative cell cycle regulators that act as a brake to prevent the tumorigenic effects of sustained Ras signaling. Here we aim to gain further insight into the mechanisms that allow GH4T2 cells to evade an oncogenic response to Ras. We show that Ral, but likely not menin, plays a key role in directing Ras-mediated differentiation of somatolactotropes, which may allow these cells to escape the tumorigenic fate that is often associated with activated Ras signaling. We also show that dominant negative Ras expression results in reduced GH4T2 cell proliferation and transformation, but does not influence differentiation. Taken together, the data presented here begin to shed light on the mechanisms by which pituitary somatolactotropes evade an oncogenic response to persistently activated Ras signaling and suggest that the architecture of the Ras signaling cascade in some endocrine cell types may be distinct from that of cells that respond to Ras in an oncogenic manner.

Anti-colorectal cancer effects of anti-p21Ras scFv delivered by the recombinant adenovirus KGHV500 and cytokine-induced killer cells

BACKGROUND

Colorectal cancer (CRC) is the most common type of gastrointestinal cancer. CRC gene therapy mediated by adenovirus holds great promise for the treatment of malignancies. However, intravenous delivery of adenovirus exhibits limited anti-tumor activity in vivo when used alone.

METHODS

In this study, the antitumor activity of the recombinant adenovirus KGHV500 was assessed with the MTT, TUNEL, Matrigel invasion and cell migration assays. To enhance the intravenous delivery of KGHV500 in vivo, cytokine-induced killer (CIK) cells were used as a second vector to carry KGHV500. We explored whether CIK cells could carry the recombinant adenovirus KGHV500 containing the anti-p21Ras single chain fragment variable antibody (scFv) gene into tumors and enhance antitumor potency.

RESULTS

Our results showed that KGHV500 exhibited significant antitumor activity in vitro. In the nude mouse SW480 tumor xenograft model, the combination of CIK cells with KGHV500 could induce higher antitumor activity against colorectal cancer in vivo than that induced by either CIK or KGHV500 alone. After seven days of treatment, adenovirus and scFv were detected in tumor tissue but were not detected in normal tissues by immunohistochemistry. Therefore, KGHV500 replicates in tumors and successfully expresses anti-p21Ras scFv in a colorectal cancer xenograft model.

CONCLUSIONS

Our study provides a novel strategy for the treatment of colorectal cancer by combining CIK cells with the recombinant adenovirus KGHV500 which carried anti-p21 Ras scFv.

Prp8 regulates oncogene-induced hyperplastic growth in Drosophila

Although developmental signalling pathways control tumourigenic growth, the cellular mechanisms that abnormally proliferating cells rely on are still largely unknown. Drosophila melanogaster is a genetically tractable model that is used to study how specific genetic changes confer advantageous tumourigenic traits. Despite recent efforts, the role of deubiquitylating enzymes in cancer is particularly understudied. We performed a Drosophila in vivo RNAi screen to identify deubiquitylating enzymes that modulate Ras^V12-induced hyperplastic growth. We identified the spliceosome core component Prp8 as a crucial regulator of Ras-, EGFR-, Notch- or RET-driven hyperplasia. Loss of prp8 function alone decreased cell proliferation, increased cell death, and affected cell differentiation and polarity. In hyperplasia, Prp8 supported tissue overgrowth independently of caspase-dependent cell death. The depletion of prp8 efficiently blocked Ras-, EGFR- and Notch-driven tumours but, in contrast, enhanced tumours that were driven by oncogenic RET, suggesting a context-specific role in hyperplasia. These data show, for the first time, that Prp8 regulates hyperplasia, and extend recent observations on the potential role of the spliceosome in cancer. Our findings suggest that targeting Prp8 could be beneficial in specific tumour types.

Summary: Prp8 has been identified as a modulator of oncogenic growth in multiple Drosophila cancer models, which suggests the spliceosome as a potential context-dependent target in cancers.

Apatinib exerts anti-tumor activity to non-Hodgkin lymphoma by inhibition of the Ras pathway

Apatinib is a tyrosine kinase inhibitor that selectively targets vascular endothelial growth factor receptor-2 (VEGFR-2). Although apatinib has shown promising anti-tumor activity against several types of tumor, its role and underlying mechanism against non-Hodgkin lymphoma (NHL) remain to be explored. Here, we report that apatinib dramatically inhibited in vitro the proliferation of various human NHL cell lines, including Burkitt lymphoma (BL), mantle cell lymphoma (MCL), and diffuse large B-cell lymphoma (DLBCL), in a dose-dependent manner. Moreover, administration of apatinib markedly delayed tumor growth in vivo in a xenograft mouse model derived from human DLBCL OCI-ly3 cells, in association with significantly prolonged survival of tumor-bearing mice. Mechanistically, apatinib suppressed activation of VEGFR2 (manifested by reduced VEGFR2 phosphorylation), accompanied by inhibition of the Ras pathway (reflected by down-regulation Ras, Raf, pMEK1/2, pERK1/2) in OCI-ly1 (GCB subtype of DLBCL) and SU-DHL2 (ABC subtype of DLBCL) cells. Of note, apatinib sharply impaired angiogenesis in vivo in tumor tissues. Together, these results indicate that apatinib displays a marked cytotoxic activity against various types of NHL cells (including BL, MCL, and GCB- or ABC-DLBCL) both in vitro and in vivo. They also suggest that anti-NHL activity of apatinib might be associated with inhibition of tumor cell growth and induction of apoptosis as well as anti-angiogenesis by targeting VEGFR2 and its downstream Ras/Raf/MEK/ERK pathway.

Comprehensive Analysis of the Relationship Between RAS and RAF Mutations and MSI Status of Colorectal Cancer in Northeastern China

BACKGROUND/AIMS

Colorectal cancer (CRC) is mainly caused by chromosomal instability (CIN) and microsatellite instability (MSI). The RAS and RAF genes are essential components of the CIN pathway, and several studies have found that RAS and RAF mutations are associated with MSI status in CRC. Here, we examined these three factors in CRC in Northeast China and aimed to reveal new details of the relationship between these mutations and MSI status.

METHODS

This study involved 290 patients with CRC who had RAS or RAF gene mutation detected using fluorescence-based allele-specific polymerase chain reaction or Sanger sequencing. The majority of the identified patients were found to harbor MSI (MSI status). Accurate molecular detection was carried out using formalin-fixed paraffin-embedded tissue or blood samples.

RESULTS

The rates of RAS and RAF mutations were 58.5% and 4.1%, respectively. The prevalence of RAS mutation in CRC was clearly higher and that of RAF mutation was lower in Northeast China compared with previously reported cohorts in other locations. High MSI level (MSI-H status) was more complex, at around 10%. This was consistent with previous data from China. However, compared with data reported from other continents, MSI-H was higher than that of Japan or South Korea in Asia, and lower than that of Europe or the United States.

CONCLUSION

RAS/RAF mutations and MSI status in CRC are closely associated with tumor location and ethnicity. Further studies investigating the relationship between these three factors can help in the development of treatment strategies for patients with CRC.

Is Ras a potential target in treatment against cutaneous squamous cell carcinoma?

Hyperactive retrovirus-associated DNA sequence (Ras) genes have been found in human cancers and are involved in cancer pathogenesis. Salirasib, one anti-Ras compound, was reported to exhibit antitumoral effects, but its role remains unclear in cutaneous squamous cell carcinoma (cSCC). In our study, salirasib treatment led to deregulation of c-Raf, ERK and Akt signaling, blockage of MTOR signaling, interruption on Beclin 1-related autophagy regulation, activation of apoptosis and down-regulation of some cell cycle regulatory proteins in primary human epidermal keratinocyte (HEK)s, but did not exhibit similar effects in the human cSCC cell line COLO-16. MEK inhibitor U0126 can lead to dephosphorylation of MTOR and Rictor in COLO-16 cells; however, c-Raf was not yet down-regulated after salirasib treatment in the presence of U0126. Furthermore, we verified that the Ras activity could be suppressed by salirasib, and there was no loss-of-function mutation in c-Raf in HEKs and COLO-16 cells. In summary, salirasib does not exhibit antitumoral effects in the cSCC cells in assays in vitro. We speculated that the disability of signaling transmission from Ras to c-Raf in COLO-16 cells might contribute to the ineffective performance of salirasib.

Using Transcriptomes as Mutant Phenotypes Reveals Functional Regions of a Mediator Subunit in Caenorhabditis elegans

Although transcriptomes have recently been used as phenotypes with which to perform epistasis analyses, they are not yet used to study intragenic function/structure relationships. We developed a theoretical framework to study allelic series using transcriptomic phenotypes. As a proof-of-concept, we apply our methods to an allelic series of dpy-22, a highly pleiotropic Caenorhabditis elegans gene orthologous to the human gene MED12, which encodes a subunit of the Mediator complex. Our methods identify functional units within dpy-22 that modulate Mediator activity upon various genetic programs, including the Wnt and Ras modules.

Receptor tyrosine kinase-Ras-PI 3 kinase-Akt signaling network in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most malignant form of the brain tumors and shows different genetic and epigenetic abnormalities. Gene amplification, genetic instability, disruption of apoptotic pathways, deregulated oncogene expression, invasive phenotypical changes, abnormal angiogenesis, and epigenetic changes have all been described in GBMs. These abnormalities indicate that a number of different signaling pathways are deregulated in GBM. Increasing number of studies provide a better understanding of the tumor biology, genetic, and epigenetic background of the GBM. Also, current research provides us useful approaches in designing novel therapies for GBM. In this review, we summarize the receptor tyrosine kinase-Ras-PI 3 kinase-Akt signaling network, focusing on the potential molecular targets for anti-signaling molecular therapies in this pathway.

Small GTPases: Structure, biological function and its interaction with nanoparticles

Small GTPase is a kind of GTP-binding protein commonly found in eukaryotic cells. It plays an important role in cytoskeletal reorganization, cell polarity, cell cycle progression, gene expression and many other significant events in cells, such as the interaction with foreign particles. Therefore, it is of great scientific significance to understand the biological properties of small GTPases as well as the GTPase-nano interplay, since more and more nanomedicine are supposed to be used in biomedical field. However, there is no review in this aspect. This review summarizes the small GTPases in terms of the structure, biological function and its interaction with nanoparticles. We briefly introduced the various nanoparticles such as gold/silver nanoparticles, SWCNT, polymeric micelles and other nano delivery systems that interacted with different GTPases. These current nanoparticles exhibited different pharmacological effect modes and various target design concepts in the small GTPases study. This will help to elucidate the conclusion that the therapeutic strategy targeting small GTPases might be a new research direction. It is believed that the in-depth study on the functional mechanism of GTPases can provide insights for the design and study of nanomedicines.

Cutaneous squamous cell carcinoma: Incidence, risk factors, diagnosis, and staging

Cutaneous squamous cell carcinoma (cSCC), a malignant proliferation of cutaneous epithelium, represents 20% to 50% of skin cancers. Although the majority of cSCCs are successfully eradicated by surgical excision, a subset of cSCC possesses features associated with a higher likelihood of recurrence, metastasis, and death. The proper identification of these aggressive cSCCs can guide additional work-up and management. In the first article in this continuing medical education series, we discuss the incidence, recurrence rates, mortality rates, and risk factors associated with cSCC and review the staging systems used to stratify patients into high- and low-risk groups. The second article in this series reviews the treatment options for cSCC, with focused attention on the management of high-stage tumors.

A quantitative model of developmental RTK signaling

Receptor tyrosine kinases (RTKs) control a wide range of developmental processes, from the first stages of embryogenesis to postnatal growth and neurocognitive development in the adult. A significant share of our knowledge about RTKs comes from genetic screens in model organisms, which provided numerous examples demonstrating how specific cell fates and morphologies are abolished when RTK activation is either abrogated or significantly reduced. Aberrant activation of such pathways has also been recognized in many forms of cancer. More recently, studies of human developmental syndromes established that excessive activation of RTKs and their downstream signaling effectors, most notably the Ras signaling pathway, can also lead to structural and functional defects. Given that both insufficient and excessive pathway activation can lead to abnormalities, mechanistic analysis of developmental RTK signaling must address quantitative questions about its regulation and function. Patterning events controlled by the RTK Torso in the early Drosophila embryo are well-suited for this purpose. This mini review summarizes current state of knowledge about Torso-dependent Ras activation and discusses its potential to serve as a quantitative model for studying the general principles of Ras signaling in development and disease.

Leishmania donovani infection differentially regulates small G-proteins

Leishmania is a protozoan parasite that resides and replicates in macrophages and causes leishmaniasis. The parasite alters the signaling cascade in host macrophages and evades the host machinery. Small G-proteins are GTPases, grouped in 5 different families that play a crucial role in the regulation of cell proliferation, cell survival, apoptosis, intracellular trafficking, and transport. In particular, the Ras family of small G-proteins has been identified to play a significant role in the cellular functions mentioned before. Here, we studied the differential expression of the most important small G-proteins during Leishmania infection. We found major changes in the expression of different isoforms of Ras, mainly in N-Ras. We observed that Leishmania donovani infection led to enhanced N-Ras expression, whereas it inhibited K-Ras and H-Ras expression. Furthermore, an active N-Ras pull-down assay showed enhanced N-Ras activity. L donovani infection also increased extracellular signal-regulated kinase 1/2 phosphorylation and simultaneously decreased p38 phosphorylation. In contrast, pharmacological inhibition of Ras led to reduction in the phosphorylation of extracellular signal-regulated kinase 1/2 and enhanced the phosphorylation of p38 in Leishmania-infected cells, which could lead to increased interleukin-12 expression and decreased interleukin-10 expression. Indeed, farnesylthiosalicyclic acid (a Ras inhibitor), when used at the effective level in L donovani-infected macrophages, reduced amastigotes in the host macrophages. Thus, upregulated N-Ras expression during L donovani infection could be a novel immune evasion strategy of Leishmania and would be a potential target for antileishmanial immunotherapy.

MLL4 Is Required to Maintain Broad H3K4me3 Peaks and Super-Enhancers at Tumor Suppressor Genes

Super-enhancers are large clusters of enhancers that activate gene expression. Broad trimethyl histone H3 lysine 4 (H3K4me3) often defines active tumor suppressor genes. However, how these epigenomic signatures are regulated for tumor suppression is little understood. Here we show that brain-specific knockout of the H3K4 methyltransferase MLL4 (a COMPASS-like enzyme, also known as KMT2D) in mice spontaneously induces medulloblastoma. Mll4 loss upregulates oncogenic Ras and Notch pathways while downregulating neuronal gene expression programs. MLL4 enhances DNMT3A-catalyzed DNA methylation and SIRT1/BCL6-mediated H4K16 deacetylation, which antagonize expression of Ras activators and Notch pathway components, respectively. Notably, Mll4 loss downregulates tumor suppressor genes (e.g., Dnmt3a and Bcl6) by diminishing broad H3K4me3 and super-enhancers and also causes widespread impairment of these epigenomic signatures during medulloblastoma genesis. These findings suggest an anti-tumor role for super-enhancers and provide a unique tumor-suppressive mechanism in which MLL4 is necessary to maintain broad H3K4me3 and super-enhancers at tumor suppressor genes.

Src Cooperates with Oncogenic Ras in Tumourigenesis via the JNK and PI3K Pathways in Drosophila epithelial Tissue

The Ras oncogene (Rat Sarcoma oncogene, a small GTPase) is a key driver of human cancer, however alone it is insufficient to produce malignancy, due to the induction of cell cycle arrest or senescence. In a Drosophila melanogaster genetic screen for genes that cooperate with oncogenic Ras (bearing the Ras^V12 mutation, or Ras^ACT), we identified the Drosophila Src (Sarcoma virus oncogene) family non-receptor tyrosine protein kinase genes, Src42A and Src64B, as promoting increased hyperplasia in a whole epithelial tissue context in the Drosophila eye. Moreover, overexpression of Src cooperated with Ras^ACT in epithelial cell clones to drive neoplastic tumourigenesis. We found that Src overexpression alone activated the Jun N-terminal Kinase (JNK) signalling pathway to promote actin cytoskeletal and cell polarity defects and drive apoptosis, whereas, in cooperation with Ras^ACT, JNK led to a loss of differentiation and an invasive phenotype. Src + Ras^ACT cooperative tumourigenesis was dependent on JNK as well as Phosphoinositide 3-Kinase (PI3K) signalling, suggesting that targeting these pathways might provide novel therapeutic opportunities in cancers dependent on Src and Ras signalling.

PIASy antagonizes Ras-driven NSCLC survival by promoting GATA2 SUMOylation

GATA2 regulated transcriptional network has been validated requisite for RAS oncogene-driven non-small cell lung cancer (NSCLC). GATA2 has been reported as a SUMOylated protein. In endothelial cells, its transcriptional activity is attenuated by SUMO-2 conjugation, which is specifically catalyzed by its E3 ligase PIASy. In this study, we found a decreased expression of PIASy in RAS mutant NSCLC cell lines and specimens with RAS mutations. Forced expression of PIASy in NSCLC cells inhibits their viability in vitro, as well as tumorigenesis and growth in vivo. Mechanistically, we demonstrated overexpression of PIASy in A549 cells altered the regulated transcriptional network of GATA2, including proteasome, IL-1-signaling, and Rho-signaling pathways. Forced expression of PIASy resulted in the accumulated SUMOylation of GATA2, attenuating its transcriptional activity in A549 cells. These results collectively suggest that PIASy plays an antagonistic role in RAS-driven NSCLC survival, by enhancing the SUMOylation of GATA2 and inhibiting its transcriptional activity.

A novel tricarbonylmethane agent (CMC2.24) reduces human pancreatic tumor growth in mice by targeting Ras

Pancreatic Cancer (PC) is a deadly disease in need of new therapeutic options. We recently developed a novel tricarbonylmethane agent (CMC2.24) as a therapeutic agent for PC, and evaluated its efficacy in preclinical models of PC. CMC2.24 inhibited the growth of various human PC cell lines in a concentration and time-dependent manner. Normal human pancreatic epithelial cells were resistant to CMC2.24, indicating selectivity. CMC2.24 reduced the growth of subcutaneous and orthotopic PC xenografts in mice by up to 65% (P < 0.02), and the growth of a human patient-derived tumor xenograft by 47.5% (P < 0.03 vs vehicle control). Mechanistically, CMC2.24 inhibited the Ras-RAF-MEK-ERK pathway. Based on Ras Pull-Down Assays, CMC2.24 inhibited Ras-GTP, the active form of Ras, in MIA PaCa-2 cells and in pancreatic acinar explants isolated from Kras mutant mice, by 90.3% and 89.1%, respectively (P < 0.01, for both). The inhibition of active Ras led to an inhibition of c-RAF, MEK, and ERK phosphorylation by 93%, 91%, and 87%, respectively (P < 0.02, for all) in PC xenografts. Furthermore, c-RAF overexpression partially rescued MIA PaCa-2 cells from the cell growth inhibition by CMC2.24. In addition, downstream of ERK, CMC2.24 inhibited STAT3 phosphorylation levels at the serine 727 residue, enhanced the levels of superoxide anion in mitochondria, and induced intrinsic apoptosis as shown by the release of cytochrome c from the mitochondria to the cytosol and the further cleavage of caspase 9 in PC cells. In conclusion, CMC2.24, a potential Ras inhibitor, is an efficacious agent for PC treatment in preclinical models, deserving further evaluation.