Functional characterization of the tumor-suppressor MARCKS in colorectal cancer and its association with survival

Spatial characterization and stratification of colorectal adenomas by deep visual proteomics

Colorectal adenomas (CRAs) are potential precursor lesions to adenocarcinomas, currently classified by morphological features. We aimed to establish a molecular feature-based risk allocation framework toward improved patient stratification. Deep visual proteomics (DVP) is an approach that combines image-based artificial intelligence with automated microdissection and ultra-high sensitive mass spectrometry. Here, we used DVP on formalin-fixed, paraffin-embedded (FFPE) CRA tissues from nine male patients, immunohistologically stained for caudal-type homeobox 2 (CDX2), a protein implicated in colorectal cancer, enabling the characterization of cellular heterogeneity within distinct tissue regions and across patients. DVP identified DMBT1, MARCKS, and CD99 as protein markers linked to recurrence, suggesting their potential for risk assessment. It also detected a metabolic shift to anaerobic glycolysis in cells with high CDX2 expression. Our findings underscore the potential of spatial proteomics to refine early stage detection and contribute to personalized patient management strategies and provided novel insights into metabolic reprogramming.

Antler-derived microRNA PC-5p-1090 inhibits HCC cell proliferation, migration, and invasion by targeting MARCKS, SMARCAD1, and SOX9

The capability of microRNAs (miRNAs) to regulate gene expression across species has opened new avenues for miRNA-based therapeutics. Here, we investigated the potential of PC-5p-1090 (miR-PC-1090), a miRNA found in deer antlers, to control the malignant phenotypes of hepatocellular carcinoma (HCC) cells. Using Cell Counting Kit-8 and transwell assays, we found that heterologous expression of miR-PC-1090 inhibited HCC cell proliferation, migration, and invasion. Bioinformatics analysis indicated that predicted miR-PC-1090 targets, including MARCKS, SMARCAD1, and SOX9, were significantly elevated in HCC tissues, and their high expressions were associated with poor overall survival of HCC patients. Moreover, mechanistic investigations revealed that miR-PC-1090 promoted the degradation of MARCKS and SMARCAD1 mRNAs and hindered the translation of SOX9 mRNA by recognizing their 3' untranslated regions. Subsequent loss-of-function and rescue experiments confirmed the involvement of MARCKS, SMARCAD1, and SOX9 in miR-PC-1090-suppressed HCC cell proliferation, migration, and invasion. Notably, MARCKS knockdown induced the downregulation of phosphorylated MARCKS and a corresponding upregulation of phosphorylated AKT in HCC. Conversely, miR-PC-1090 repressed MARCKS phosphorylation and effectively circumvented the activation of the PI3K/AKT pathway. Furthermore, miR-PC-1090 regulates the Wnt/β-catenin pathway through SMARCAD1- and SOX9-mediated reduction of β-catenin expression. Overall, our results illustrate the tumor-suppressive activity and molecular mechanism of antler-derived miR-PC-1090 in HCC cells, indicating its potential as a multiple-target agent for HCC treatment.

Small Extracellular Vesicles Containing miR-34c Derived from Bone Marrow Mesenchymal Stem Cells Regulates Epithelial Sodium Channel via Targeting MARCKS

Epithelial sodium channel (ENaC) is a pivotal regulator of alveolar fluid clearance in the airway epithelium and plays a key role in the treatment of acute lung injury (ALI), which is mainly composed of the three homologous subunits (α, β and γ). The mechanisms of microRNAs in small extracellular vesicles (sEVs) derived from mesenchymal stem cell (MSC-sEVs) on the regulation of lung ion transport are seldom reported. In this study, we aimed at investigating whether miR-34c had an effect on ENaC dysfunction induced by lipopolysaccharide and explored the underlying mechanism in this process. Primarily, the effect of miR-34c on lung edema and histopathology changes in an ALI mouse model was investigated. Then the uptake of PKH26-labeled sEVs was observed in recipient cells, and we observed that the overexpression of miR-34c in MSC-sEVs could upregulate the LPS-inhibited γ-ENaC expression. The dual luciferase reporter gene assay demonstrated that myristoylated alanine-rich C kinase substrate (MARCKS) was one of target genes of miR-34c, the protein expression of which was negatively correlated with miR-34c. Subsequently, either upregulating miR-34c or knocking down MARCKS could increase the protein expression of phospho-phosphatidylinositol 3-kinase (p-PI3K) and phospho-protein kinase B (p-AKT), implying a downstream regulation pathway was involved. All of the above suggest that miR-34c in MSC-sEVs can attenuate edematous lung injury via enhancing γ-ENaC expression, at least partially, through targeting MARCKS and activating the PI3K/AKT signaling pathway subsequently.

Advances in immune therapies for the treatment of microsatellite instability‑high/deficient mismatch repair metastatic colorectal cancer (Review)

Microsatellite instability-high/deficient mismatch repair colorectal cancer (MSI-H/dMMR CRC) is a molecular subtype characterized by high-frequency mutations within DNA mismatch repair genes. Defects in the DNA mismatch repair machinery lead to subsequent frame-shift mutations, resulting in the generation of frame-shift peptides that serve as neoantigens. This has translated into exquisite sensitivity to immune checkpoint inhibitors (ICIs) and a significant clinical benefit from immune therapies in this patient population. The present article provides a comprehensive review of the advances in the field of immune therapies for MSI-H/dMMR metastatic CRC, with a focus on the major randomized clinical trials that led to Food and Drug Administration approval of specific ICIs for this population, a detailed review of the molecular background responsible for tumor response, as well as the mechanisms of resistance to ICI therapy. Finally, ongoing investigations of other immunotherapeutic strategies to address and overcome the challenges that currently limit response and long-term response to ICIs were presented.

MARCKS on Tumor-Associated Macrophages is Correlated with Immune Infiltrates and Poor Prognosis in Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma is the fourth most common cause of cancer-related death. However, the cross-talk between tumor immune microenvironment and hepatocellular carcinoma (HCC) remains unclear.

MATERIAL AND METHODS

We analyzed the expression of miR-143-3p in exosomes from different HCC cell lines. Differentially expressed genes (DEGs) in Tumor-associated macrophages (TAMs) co-cultured with HCC cell lines were overlapped with miR-143-3p target genes. We used the Oncomine, Kaplan-Meier plotter, and The Cancer Genome Atlas (TCGA) databases to assess Myristoylated alanine-rich C-kinase substrate (MARCKS) expression in various types of cancers. The relationship between patient clinicopathological characteristics and MARCKS expression level was identified using the Kaplan-Meier plotter database. Last, we analyzed how MARCKS expression correlated with immune infiltration makers using the TCGA database, Tumor IMmune Estimation Resource (TIMER), and Gene Expression Profiling Interactive Analysis (GEPIA).

RESULTS

Exosomal miR-143-3p was elevated after IL-6 treatment in the HCC cell line. MARCKS, a target gene of miR-143-3p, was up-regulated in Tumor-associated macrophages co-cultured with high-metastatic-potential HCC cell line. MARCKS expression was identified as significantly correlated with outcome in multiple types of cancer, especially in HCC. High MARCKS expression level was associated with poorer overall survival (OS), Progress-free survival (PFS), and also with patient gender, race, hepatitis virus background, stage, grade, AJCC_T, and vascular invasion. MARCKS was positively associated with levels of T follicular helper cells (TFH) (R = .48, p < .001), T helper type 2 (Th2) cells (R = .47, p < .001), macrophages (R = .41, p ≤ .001), T helper cells (R = .40, p < .001), T helper type 1 (Th1) cells (R = .38, p < .001), T cells (R = .34, p < .001), NK CD56bright cells (R = .34, p < .001) and immature DC (iDC) (R = .33, p < .001), and negatively associated with levels of T helper 17 (Th17) cells. Also, MARCKS may influence the M2 polarization and immune escape.

CONCLUSION

The present study suggests that MARCKS on TAMs is associated with poor prognosis and immune cell infiltration in HCC.

Pathophysiological roles of myristoylated alanine-rich C-kinase substrate (MARCKS) in hematological malignancies

The myristoylated alanine-rich C-kinase substrate (MARCKS) protein has been at the crossroads of multiple signaling pathways that govern several critical operations in normal and malignant cellular physiology. Functioning as a target of protein kinase C, MARCKS shuttles between the phosphorylated cytosolic form and the unphosphorylated plasma membrane-bound states whilst regulating several molecular partners including, but not limited to calmodulin, actin, phosphatidylinositol-4,5-bisphosphate, and phosphoinositide-3-kinase. As a result of these interactions, MARCKS directly or indirectly modulates a host of cellular functions, primarily including cytoskeletal reorganization, membrane trafficking, cell secretion, inflammatory response, cell migration, and mitosis. Recent evidence indicates that dysregulated expression of MARCKS is associated with the development and progression of hematological cancers. While it is understood that MARCKS impacts the overall carcinogenesis as well as plays a part in determining the disease outcome in blood cancers, we are still at an early stage of interpreting the pathophysiological roles of MARCKS in neoplastic disease. The situation is further complicated by contradictory reports regarding the role of phosphorylated versus an unphosphorylated form of MARCKS as an oncogene versus tumor suppressor in blood cancers. In this review, we will investigate the current body of knowledge and evolving concepts of the physical properties, molecular network, functional attributes, and the likely pathogenic roles of MARCKS in hematological malignancies. Key emphasis will also be laid upon understanding the novel mechanisms by which MARCKS determines the overall disease prognosis by playing a vital role in the induction of therapeutic resistance. Additionally, we will highlight the importance of MARCKS as a valuable therapeutic target in blood cancers and will discuss the potential of existing strategies available to tackle MARCKS-driven blood cancers.

MicroRNA-142-3p attenuates hepatic ischemia/reperfusion injury via targeting of myristoylated alanine-rich C-kinase substrate

MiR-142-3p as one key molecule in oncogenesis and inflammation plays crucial roles in hepatic fibrosis, hepatocellular carcinoma and other liver disease. However, there have no literatures to report its effects on hepatic ischemia-reperfusion (HI/R) injury. In the present work, hypoxia reoxygenation (H/R) models on AML12 and HepG2 cells, and ischemia/reperfusion model in mice were established. The methods of real-time PCR, dual luciferase reporter, mimic, inhibitor, agomir, antagomir and siRNA transfection assays were used. The expression levels of miR-142-3p were decreased in model groups in vitro and in vivo compared with control group or Sham group, which directly targeted MARCKS to regulate its expression. Then, MARCKS activated p38/JNK signal, up-regulated NF-κB expression to accelerate inflammation, and inhibited PI3K/AKT signal to promote apoptosis. Moreover, miR-142-3p mimic in vitro and agomir in vivo lowered the expression levels of MARCKS, thereby alleviating apoptosis and inflammation to relieve HI/R injury. Furthermore, miR-142- 3p inhibitor in vitro and antagomir in vivo up-regulated the expression levels of MARCKS to aggravate HI/R damage via promoting inflammation and apoptosis. Consistently, MARCKS siRNA markedly inhibited HI/R injury by restraining apoptosis and inflamm- ation in mice. MiR-142-3p played a considerable part in adjusting HI/R injury by targeting MARCKS, and miR-142-3p/MARCKS should be a new therapeutic target for HI/R injury.

Restoration of MARCKS enhances chemosensitivity in cancer

Purpose

Increased ATP-binding-cassette (ABC) transporter activity is a major cause of chemotherapy resistance in cancer. The ABC transporter family member ABCB1 is often overexpressed in colorectal cancer (CRC). Phosphatidylinositol-4,5-bisphosphat (PI(4,5)P₂)-dependent pathways are involved in the regulation of ABCB1 function. The protein Myristoylated Alanine-Rich C-Kinase Substrate (MARCKS) is a pivotal regulator of PI(4,5)P₂ and inactivated in many CRC cancers via genetic deletion or hyperphosphorylation. Therefore, MARCKS may critically impact ABCB1.

Methods

CRC samples as well as CRC cell lines were tested for a connection between MARCKS and ABCB1 via immunofluorescence and Western-blot analysis. ABCB1 function was studied via calcein influx assay under treatment with known ABCB1 inhibitors (verapamil, tariquidar) as well as the kinase inhibitor bosutinib. ABCB1 internalization and MARCKS translocation was analyzed via confocal microscopy exploiting the endocytosis inhibitors chlorpromazine and dynasore. Abundance of PI(4,5)P₂ was monitored by intramolecular fluorescence resonance energy transfer (FRET). Reproductive cell survival was studied via colorimetric WST-1 and clonogenic assays in combination with exposure to the chemotherapeutics doxorubicin and 5-fuorouracil (5-FU).

Results

We found increased ABCB1 expression in MARCKS negative CRC patient tumor samples and established CRC cell lines. Mechanistically, the reconstitution of MARCKS function via recombinant expression or the pharmacological inhibition of MARCKS phosphorylation led to a substantial decrease in ABCB1 activity. In CRC cells, bosutinib treatment resulted in a MARCKS translocation from the cytosol to the plasma membrane, while simultaneously, ABCB1 was relocated to intracellular compartments. Inhibition of MARCKS phosphorylation via bosutinib rendered cells more sensitive to the chemotherapeutics doxorubicin and 5-FU.

Conclusions

Cells devoid of MARCKS function showed incomplete ABCB1 internalization, leading to higher ABCB1 activity enhancing chemoresistance. Vice versa our data suggest the prevention of MARCKS inhibition by reversing hyperphosphorylation or genomic restoration after deletion as two promising approaches to overcome tumor cell resistance towards chemotherapeutic ABCB1 substrates.

Mutational landscape of T-cell lymphoma in mice lacking the DNA mismatch repair gene Mlh1: no synergism with ionizing radiation

Biallelic germline mutations in the DNA mismatch repair gene MLH1 lead to constitutional mismatch repair-deficiency syndrome and an increased risk for childhood hematopoietic malignancies, including lymphoma and leukemia. To examine how Mlh1 dysfunction promotes lymphoma as well as the influence of ionizing radiation (IR) exposure, we used an Mlh1-/- mouse model and whole-exome sequencing to assess genomic alterations in 23 T-cell lymphomas, including 8 spontaneous and 15 IR-associated lymphomas. Exposure to IR accelerated T-cell lymphoma induction in the Mlh1-/- mice, and whole-exome sequencing revealed that IR exposure neither increased the number of mutations nor altered the mutation spectrum of the lymphomas. Frequent mutations were evident in genes encoding transcription factors (e.g. Ikzf1, Trp53, Bcl11b), epigenetic regulators (e.g. Suv420h1, Ep300, Kmt2d), transporters (e.g. Rangap1, Kcnj16), extracellular matrix (e.g. Megf6, Lrig1), cell motility (e.g. Argef19, Dnah17), protein kinase cascade (e.g. Ptpro, Marcks) and in genes involved in NOTCH (e.g. Notch1), and PI3K/AKT (e.g. Pten, Akt2) signaling pathways in both spontaneous and IR-associated lymphomas. Frameshift mutations in mononucleotide repeat sequences within the genes Trp53, Ep300, Kmt2d, Notch1, Pten and Marcks were newly identified in the lymphomas. The lymphomas also exhibited a few chromosomal abnormalities. The results establish a landscape of genomic alterations in spontaneous and IR-associated lymphomas that occur in the context of mismatch repair dysfunction and suggest potential targets for cancer treatment.

Morphine contributed to the deterioration of cancer via miR-543/MARCKS/FcγR-mediated phagocytosis pathway

OBJECTIVES

It has been confirmed that morphine was detrimental to patients with cancers. Hence, we aimed to reveal a certain mechanism of morphine in cancer development.

METHODS

Microarray and GSEA analysis were utilized to seek for differently expressed genes and pathway.

KEY FINDINGS

Bioinformatics analysis identified that downregulation of MARCKS and upregulation of miR-543 in samples treated with morphine. FcγR-mediated phagocytosis pathway was illustrated to be upregulated in the control. PANC-1 and DU145 cell viability was increased but apoptosis was declined as morphine concentration went up from 10^-8 to 10^-6  mol/l. On the other curve, the viability was reduced and apoptosis was elevated from 10^-6 to 10^-5  mol/l. The expression of miR-543 ran the same trend as cell viability. Assays in vivo and in vitro validated that miR-543 facilitated cell viability, tumour growth, levels of CA199 and PSA, whereas inhibited apoptosis. MARCKS could target and inhibit miR-543 expression, which exhibited an opposite effect on cancer progression. MiR-543 blocked but MARCKS activated FcγR-mediated phagocytosis pathway.

CONCLUSIONS

Morphine at 10^-6  mol/l could benefit miR-543 expression to inhibit MARCKS expression, consequently, blocking FcγR-mediated phagocytosis pathway, which contributed to the cancer progression in vitro and in vivo.

A Unique Family of Neuronal Signaling Proteins Implicated in Oncogenesis and Tumor Suppression

The neuronal proteins GAP43 (neuromodulin), MARCKS, and BASP1 are highly expressed in the growth cones of nerve cells where they are involved in signal transmission and cytoskeleton organization. Although their primary structures are unrelated, these signaling proteins share several structural properties like fatty acid modification, and the presence of cationic effector domains. GAP43, MARCKS, and BASP1 bind to cell membrane phospholipids, a process reversibly regulated by protein kinase C-phosphorylation or by binding to the calcium sensor calmodulin (CaM). GAP43, MARCKS, and BASP1 are also expressed in non-neuronal cells, where they may have important functions to manage cytoskeleton architecture, and in case of MARCKS and BASP1 to act as cofactors in transcriptional regulation. During neoplastic cell transformation, the proteins reveal differential expression in normal vs. tumor cells, and display intrinsic tumor promoting or tumor suppressive activities. Whereas GAP43 and MARCKS are oncogenic, tumor suppressive functions have been ascribed to BASP1 and in part to MARCKS depending on the cell type. Like MARCKS, the myristoylated BASP1 protein is localized both in the cytoplasm and in the cell nucleus. Nuclear BASP1 participates in gene regulation converting the Wilms tumor transcription factor WT1 from an oncoprotein into a tumor suppressor. The BASP1 gene is downregulated in many human tumor cell lines particularly in those derived from leukemias, which display elevated levels of WT1 and of the major cancer driver MYC. BASP1 specifically inhibits MYC-induced cell transformation in cultured cells. The tumor suppressive functions of BASP1 and MARCKS could be exploited to expand the spectrum of future innovative therapeutic approaches to inhibit growth and viability of susceptible human tumors.

Myristoylated alanine-rich C-kinase substrate effector domain phosphorylation regulates the growth and radiation sensitization of glioblastoma

Glioblastoma harbors frequent alterations in receptor tyrosine kinases, phosphatidylinositol-3 kinase (PI3K) and phosphatase and tensin homolog (PTEN) that dysregulate phospholipid signaling driven tumor proliferation and therapeutic resistance. Myristoylated alanine-rich C-kinase substrate (MARCKS) is a 32 kDa intrinsically unstructured protein containing a polybasic (+13) effector domain (ED), which regulates its electrostatic sequestration of phospholipid phosphatidylinositol (4,5)-bisphosphate (PIP2), and its binding to phosphatidylserine, calcium/calmodulin, filamentous actin, while also serving as a nuclear localization sequence. MARCKS ED is phosphorylated by protein kinase C (PKC) and Rho-associated protein kinase (ROCK) kinases; however, the impact of MARCKS on glioblastoma growth and radiation sensitivity remains undetermined. In the present study, using a tetracycline-inducible system in PTEN-null U87 cells, we demonstrate that MARCKS overexpression suppresses growth and enhances radiation sensitivity in vivo. A new image cytometer, Xcyto10, was utilized to quantify differences in MARCKS ED phosphorylation on localization and its association with filamentous actin. The overexpression of the non-phosphorylatable ED mutant exerted growth-suppressive and radiation-sensitizing effects, while the pseudo-phosphorylated ED mutant exhibited an enhanced colony formation and clonogenic survival ability. The identification of MARCKS protein-protein interactions using co-immunoprecipitation coupled with tandem mass spectrometry revealed novel MARCKS-associated proteins, including importin-β and ku70. On the whole, the findings of this study suggest that the determination of the MARCKS ED phosphorylation status is essential to understanding the impact of MARCKS on cancer progression.

MARCKS regulates tonic and chronic active B cell receptor signaling

Tonic or chronic active B-cell receptor (BCR) signaling is essential for the survival of normal or some malignant B cells, respectively. However, the molecular mechanism regulating the strength of these two types of BCR signaling remains unknown. Here, using high-speed high-resolution single-molecule tracking in live cells, we identified that PKCβ, STIM1, and IP3R1/2/3 molecules affected the lateral Brownian mobile behavior of BCRs on the plasma membrane of quiescent B cells, which was correlated to the strength of BCR signaling. Further mechanistic studies revealed that these three molecules influenced BCR mobility by regulating the membrane tethering of MARCKS to the inner leaflet of the plasma membrane. Indeed, membrane-untethered or deficiency of MARCKS significantly decreased, while membrane-tethered or overexpression of MARCKS drastically increased the lateral mobility of BCRs. Functional experiments indicated that the membrane-tethered MARCKS suppressed the survival and/or proliferation in both B-cell tumor cells and mouse primary splenic B cells in vitro and in vivo. Mechanistically, we found that membrane-tethered MARCKS increased BCR lateral mobility, and thus decreased BCR nanoclustering by disturbing the interaction between cortical F-actin and the inner leaflet of the plasma membrane, resulting in the suppression of the strength of both tonic and chronic active BCR signaling. Conclusively, MARCKS is a newly identified molecule regulating the strength of BCR signaling by modulating cytoskeleton and plasma membrane interactions, both in the physiological and pathological conditions, suggesting that MARCKS is a putative target for drug design.

Prognostic Value of Upregulation of Myristoylated Alanine-Rich C-Kinase Substrate in Gastric Cancer

Background

Accumulating evidence suggests a connection of Myristoylated alanine-rich C-kinase substrate (MARCKS) with several physiological and pathological processes. However, the relevance of MARCKS in gastric cancer (GC) needs to be elucidated.

Material/Methods

The abundance of MARCKS in GC tissues was assessed using techniques of immunohistochemistry (IHC) and quantitative real-time PCR (qRT-PCR). Moreover, the MARCKS expression profile in the TCGA database was analyzed through an online website analysis. We also investigated MARCKS function using cell wounding and Matrigel invasion assays.

Results

TCGA analysis and our data suggest that transcript abundance and protein level of MARCKS was higher in GC tumor samples compared with peri-tumor tissues. There was a remarkable association of upregulated MARCKS with the cell differentiation (P<0.001), T stage (P=0.034), and N stage (P=0.002) followed by advanced TNM phase (P=0.008). Furthermore, it was predicted that higher expression of MARCKS is linked to poor overall survival (P=0.015) and disease-free survival (P=0.020), and that high levels of MARCKS function as an independent prognostic marker, as shown by multivariate Cox regression analysis in prediction of poor overall (HR=0.408; 95% confidence interval=0.247–0.674; P<0.001) and disease-free survival rates (HR=0.525; 95% confidence interval=0.216–0.584; P<0.001). GC cells showed significant reduction in cell migration and invasion upon depletion of MARCKS as noted through Matrigel invasion and cell wounding assays. Further analyses showed that silencing MARCKS impeded the epithelial-mesenchymal transition (EMT).

Conclusions

Our study indicates that elevated expression of MARCKS is significantly associated with metastatic capability of GC cells, and MARCKS overexpression can serve as a biomarker of GC poor prognosis.

Overview of the oncogenic signaling pathways in colorectal cancer: Mechanistic insights

Colorectal cancer is a multifaceted disease which is therapeutically challenging. Based on insights gleaned from almost a quarter century of research, it is obvious that deregulation of spatio-temporally controlled signaling pathways play instrumental role in development and progression of colorectal cancer. High-throughput technologies have helped to develop a sharper and broader understanding of the wide ranging signal transduction cascades which also contribute to development of drug resistance, loss of apoptosis and, ultimately, of metastasis. In this review, we have set the spotlight on role of JAK/STAT, TGF/SMAD, Notch, WNT/β-Catenin, SHH/GLI and p53 pathways in the development and progression of colorectal cancer. We have also highlighted recent reports on TRAIL-mediated pathways and molecularly distinct voltage-gated sodium channels in colorectal cancer.

MiRNA-145 Induces Apoptosis in a Gallbladder Carcinoma Cell Line by Targeting DFF45

Bakcground

We measured expression of miRNA-145 in gallbladder carcinoma and its influence on propagation, invasion, and apoptosis of gallbladder carcinoma cells in vitro.

Methods

miRNA-145 expression was compared between normal gallbladder epithelial cells and GBS-SD (gallbladder series) cells using miRNA chip technology. Propagation, apoptosis, and invasion properties of each cell group were tested using MTT, a clone-formation assay, flow cytometry, Western blot, and Transwell assays.

Results

Expression of miRNA-145 was observed to be down-regulated and GBC-SD cell clones transiently transfected with hsa-miRNA-145 were substantially reduced compared with controls (p<0.01). We observed that GBC-SD cells transfected with hsa-miRNA-145 and double-positive (Annexin V and PI) for apoptosis were more numerous than controls. Moreover, GBC-SD cells over-expressing miRNA-145 had significantly greater expression of apoptosis-related protein, caspase-3. A Transwell assay confirmed that GBC-SD cells over-expressing miRNA-145 that migrated to the lower chamber were fewer compared with controls. Post-transcriptional regulation of gene expression was measured using dualluciferase reporter assays and data show that miRNA-145 facilitates the inhibition of GBC-SD cell growth and invasion while inducing apoptosis by targeting DFF45.

Conclusion

Thus, we speculate that miRNA-145 facilitates inhibition of GBC-SD cell growth and invasion while inducing apoptosis by targeting DFF45; however, miRNA-145 does not directly affect the GBC-SD cell cycle.

Myristoylated alanine-rich C kinase substrate (MARCKS): a multirole signaling protein in cancers

Emerging evidence implicates myristoylated alanine-rich C-kinase substrate (MARCKS), a major substrate of protein kinase C (PKC), in a critical role for cancer development and progression. MARCKS is tethered to the plasma membrane but can shuttle between the cytosol and plasma membrane via the myristoyl-electrostatic switch. Phosphorylation of MARCKS by PKC leads to its translocation from the plasma membrane to the cytosol where it functions in actin cytoskeletal remodeling, Ca²⁺ signaling through binding to calmodulin, and regulation of exocytic vesicle release in secretory cells such as neurons and airway goblet cells. Although the contribution of MARCKS to various cellular processes has been extensively studied, its roles in neoplastic disease have been conflicting. This review highlights the molecular and functional differences of MARCKS that exist between normal and tumor cells. We also discuss the recent advances in the potential roles of MARCKS in tumorigenesis, metastasis, and resistance to anti-cancer therapies, with a focus on addressing the inconsistent results regarding the function of MARCKS as a promoter or inhibitor of oncogenesis.

Carnosic acid protects mice from high-fat diet-induced NAFLD by regulating MARCKS

Non-alcoholic fatty liver disease (NAFLD) comprises a spectrum of liver damage characterized by abnormal hepatic fat accumulation and inflammatory response. Although the molecular mechanisms responsible for the disease are not yet fully understood, the pathogenesis of NAFLD likely involves multiple signals. The identification of effective therapeutic strategies to target these signals is of utmost importance. Carnosic acid (CA), as a phenolic diterpene with anticancer, anti-bacterial, anti-diabetic and neuroprotective properties, is produced by many species of the Lamiaceae family. Myristoylated alanine-rich C-kinase substrate (MARCKS) is a major protein kinase C (PKC) substrate in many different cell types. In the present study, wild-type C57BL/6 and MARCKS-deficient mice were randomly divided into the normal chow- or high-fat (HF) diet-fed groups. The HF diet increased the fasting glucose and insulin levels, and promoted glucose intolerance in the wild-type mice. MARCKS deficiency further upregulated intolerance, fasting glucose and insulin. The HF diet also promoted hepatic steatosis, serum alanine transaminase (ALT) and aspartate transaminase (AST) activity, inflammation and lipid accumulation in the wild-type mice. These responses were accelerated in the MARCKS-deficient mice. Importantly, increased inflammation and lipid accumulation were associated with phosphoinositide 3-kinase (PI3K)/AKT, NLR family pyrin domain containing 3 (NLRP3)/nuclear factor-κB (NF-κB) and sterol regulatory element binding protein-1c (SREBP-1c) signaling pathway activation. The mice treated with CA exhibited a significantly improved glucose and insulin tolerance. The production of pro-inflammatory cytokines and lipid accumulation were suppressed by CA. Significantly, MARCKS was reduced in mice fed the HF diet. CA treatment upregulated MARCKS expression compared to the HF group. Furthermore, the activation of the PI3K/AKT, NLRP3/NF-κB and SREBP-1c signaling pathways was inhibited by CA. Taken together, our data suggest that CA suppresses inflammation and lipogenesis in mice fed a HF diet through MARCKS regulation. Thus, CA may be prove to be a useful anti-NAFLD agent.

"Stealth dissemination" of macrophage-tumor cell fusions cultured from blood of patients with pancreatic ductal adenocarcinoma

Here we describe isolation and characterization of macrophage-tumor cell fusions (MTFs) from the blood of pancreatic ductal adenocarcinoma (PDAC) patients. The MTFs were generally aneuploidy, and immunophenotypic characterizations showed that the MTFs express markers characteristic of PDAC and stem cells, as well as M2-polarized macrophages. Single cell RNASeq analyses showed that the MTFs express many transcripts implicated in cancer progression, LINE1 retrotransposons, and very high levels of several long non-coding transcripts involved in metastasis (such as MALAT1). When cultured MTFs were transplanted orthotopically into mouse pancreas, they grew as obvious well-differentiated islands of cells, but they also disseminated widely throughout multiple tissues in "stealth" fashion. They were found distributed throughout multiple organs at 4, 8, or 12 weeks after transplantation (including liver, spleen, lung), occurring as single cells or small groups of cells, without formation of obvious tumors or any apparent progression over the 4 to 12 week period. We suggest that MTFs form continually during PDAC development, and that they disseminate early in cancer progression, forming "niches" at distant sites for subsequent colonization by metastasis-initiating cells.

MARCKS promotes invasion and is associated with biochemical recurrence in prostate cancer

BACKGROUND

Overtreatment of low-grade prostate cancer is a recognised problem for clinicians and patients. However, under-treatment runs the risk of missing the opportunity for cure in those who could benefit. Identification of new biomarkers of disease progression, including metastases, is required to better stratify and appropriately treat these patients. The ability to predict if prostate cancer will recur is an important clinical question that would impact treatment options for patients. Studies in other cancers have associated MARCKS with metastasis.

METHODS

Tissue microarrays of local prostatectomy samples from a cohort of biochemical recurrent and non-biochemical recurrent tumours were assayed for MARCKS protein expression. Prostate cancer cell lines were transfected with siRNA targeting MARCKS or a control and functional endpoints of migration, invasion, proliferation, viability and apoptosis were measured. Actin was visualised by fluorescent microscopy and evidence of a cadherin switch and activation of the AKT pathway were assayed.

RESULTS

MARCKS was upregulated in biochemical recurrent patients compared to non-biochemical recurrent. Knockdown of MARCKS reduced migration and invasion of prostate cancer cells, reduced MMP9 mRNA expression, as well as decreasing cell spreading and increased cell:cell adhesion in prostate cancer cell colonies. Knockdown of MARCKS had no effect on proliferation, viability or apoptosis of the prostate cancer cells.

CONCLUSIONS

In conclusion, MARCKS promotes migration and invasion and is associated with biochemical recurrence in localised prostate cancer tumours. The mechanisms by which this occurs have yet to be fully elucidated but lack of a cadherin switch indicates it is not via epithelial-to-mesenchymal transition. Actin rearrangement indicates that MARCKS promotes invasion through regulating the architecture of the cell.

Upregulation of MARCKS in kidney cancer and its potential as a therapeutic target

Targeted therapeutics, such as those abrogating hypoxia inducible factor (HIF)/vascular endothelial growth factor signaling, are initially effective against kidney cancer (or renal cell carcinoma, RCC); however, drug resistance frequently occurs via subsequent activation of alternative pathways. Through genome-scale integrated analysis of the HIF-α network, we identified the major protein kinase C substrate MARCKS (myristoylated alanine-rich C kinase substrate) as a potential target molecule for kidney cancer. In a screen of nephrectomy samples from 56 patients with RCC, we found that MARCKS expression and its phosphorylation are increased and positively correlate with tumor grade. Genetic and pharmacologic suppression of MARCKS in high-grade RCC cell lines in vitro led to a decrease in cell proliferation and migration. We further demonstrated that higher MARCKS expression promotes growth and angiogenesis in vivo in an RCC xenograft tumor. MARCKS acted upstream of the AKT/mTOR pathway, activating HIF-target genes, notably vascular endothelial growth factor-A. Following knockdown of MARCKS in RCC cells, the IC50 of the multikinase inhibitor regorafenib was reduced. Surprisingly, attenuation of MARCKS using the MPS (MARCKS phosphorylation site domain) peptide synergistically interacted with regorafenib treatment and decreased survival of kidney cancer cells through inactivation of AKT and mTOR. Our data suggest a major contribution of MARCKS to kidney cancer growth and provide an alternative therapeutic strategy of improving the efficacy of multikinase inhibitors.

MARCKS phosphorylation is modulated by a peptide mimetic of MARCKS effector domain leading to increased radiation sensitivity in lung cancer cell lines

Lung cancer is the leading cause of cancer-associated mortality in the United States. Kinase hyperactivation is a known mechanism of tumorigenesis. The phosphorylation status of the plasma membrane-associated protein myristoylated alanine rich C-kinase substrate (MARCKS) effector domain (ED) was previously established as being important in the sensitivity of lung cancer to radiation. Specifically, when MARCKS ED was in a non-phosphorylated state, lung cancer cells were more susceptible to ionizing radiation and experienced prolonged double-strand DNA breaks. Additional studies demonstrated that the phosphorylation status of MARCKS ED is important for gene expression and in vivo tumor growth. The present study used a peptide mimetic of MARCKS ED as a therapeutic intervention to modulate MARCKS phosphorylation. Culturing A549, H1792 and H1975 lung cancer cell lines with the MARCKS ED peptide led to reduced levels of phosphorylated MARCKS and phosphorylated Akt serine/threonine kinase 1. Further investigation demonstrated that the peptide therapy was able to reduce lung cancer cell proliferation and increase radiation sensitivity. In addition, the MARCKS peptide therapy was able to prolong double-strand DNA breaks following ionizing radiation exposure. The results of the present study demonstrate that a peptide mimetic of MARCKS ED is able to modulate MARCKS phosphorylation, leading to an increase in sensitivity to radiation.

Pathway Implications of Aberrant Global Methylation in Adrenocortical Cancer

Context

Adrenocortical carcinomas (ACC) are a rare tumor type with a poor five-year survival rate and limited treatment options.

Objective

Understanding of the molecular pathogenesis of this disease has been aided by genomic analyses highlighting alterations in TP53, WNT, and IGF signaling pathways. Further elucidation is needed to reveal therapeutically actionable targets in ACC.

Design

In this study, global DNA methylation levels were assessed by the Infinium HumanMethylation450 BeadChip Array on 18 ACC tumors and 6 normal adrenal tissues. A new, non-linear correlation approach, the discretization method, assessed the relationship between DNA methylation/gene expression across ACC tumors.

Results

This correlation analysis revealed epigenetic regulation of genes known to modulate TP53, WNT, and IGF signaling, as well as silencing of the tumor suppressor MARCKS, previously unreported in ACC.

Conclusions

DNA methylation may regulate genes known to play a role in ACC pathogenesis as well as known tumor suppressors.

MARCKS Signaling Differentially Regulates Vascular Smooth Muscle and Endothelial Cell Proliferation through a KIS-, p27kip1- Dependent Mechanism

Background

Overexpression of the myristolated alanine-rich C kinase substrate (MARCKS) occurs in vascular proliferative diseases such as restenosis after bypass surgery. MARCKS knockdown results in arrest of vascular smooth muscle cell (VSMC) proliferation with little effect on endothelial cell (EC) proliferation. We sought to identify the mechanism of differential regulation by MARCKS of VSMC and EC proliferation in vitro and in vivo.

Methods and Results

siRNA-mediated MARCKS knockdown in VSMCs inhibited proliferation and prevented progression from phase G₀/G₁ to S. Protein expression of the cyclin-dependent kinase inhibitor p27^kip1, but not p21^cip1 was increased by MARCKS knockdown. MARCKS knockdown did not affect proliferation in VSMCs derived from p27^kip1-/- mice indicating that the effect of MARCKS is p27^kip1-dependent. MARCKS knockdown resulted in decreased phosphorylation of p27^kip1 at threonine 187 and serine 10 as well as, kinase interacting with stathmin (KIS), cyclin D1, and Skp2 expression. Phosphorylation of p27^kip1 at serine 10 by KIS is required for nuclear export and degradation of p27^kip1. MARCKS knockdown caused nuclear trapping of p27^kip1. Both p27^kip1 nuclear trapping and cell cycle arrest were released by overexpression of KIS, but not catalytically inactive KIS. In ECs, MARCKS knockdown paradoxically increased KIS expression and cell proliferation. MARCKS knockdown in a murine aortic injury model resulted in decreased VSMC proliferation determined by bromodeoxyuridine (BrdU) integration assay, and inhibition of vascular wall thickening. MARCKS knockdown increased the rate of re-endothelialization.

Conclusions

MARCKS knockdown arrested VSMC cell cycle by decreasing KIS expression. Decreased KIS expression resulted in nuclear trapping of p27^kip1 in VSMCs. MARCKS knockdown paradoxically increased KIS expression in ECs resulting in increased EC proliferation. MARCKS knockdown significantly attenuated the VSMC proliferative response to vascular injury, but accelerated reestablishment of an intact endothelium. MARCKS is a novel translational target with beneficial cell type-specific effects on both ECs and VSMCs.

A conserved polybasic domain mediates plasma membrane targeting of Lgl and its regulation by hypoxia

The plasma membrane targeting of Lgl, a key polarity and tumor suppressor protein, is mediated by electrostatic interactions between a polybasic motif in Lgl and phospholipids on the plasma membrane, and this mechanism is regulated by hypoxia and aPKC-phosphorylation.

Lethal giant larvae (Lgl) plays essential and conserved functions in regulating both cell polarity and tumorigenesis in Drosophila melanogaster and vertebrates. It is well recognized that plasma membrane (PM) or cell cortex localization is crucial for Lgl function in vivo, but its membrane-targeting mechanisms remain poorly understood. Here, we discovered that hypoxia acutely and reversibly inhibits Lgl PM targeting through a posttranslational mechanism that is independent of the well-characterized atypical protein kinase C (aPKC) or Aurora kinase–mediated phosphorylations. Instead, we identified an evolutionarily conserved polybasic (PB) domain that targets Lgl to the PM via electrostatic binding to membrane phosphatidylinositol phosphates. Such PB domain–mediated PM targeting is inhibited by hypoxia, which reduces inositol phospholipid levels on the PM through adenosine triphosphate depletion. Moreover, Lgl PB domain contains all the identified phosphorylation sites of aPKC and Aurora kinases, providing a molecular mechanism by which phosphorylations neutralize the positive charges on the PB domain to inhibit Lgl PM targeting.

The Effector Domain of MARCKS Is a Nuclear Localization Signal that Regulates Cellular PIP2 Levels and Nuclear PIP2 Localization

Translocation to the nucleus of diacylglycerol kinase (DGK)– ζ is dependent on a sequence homologous to the effector domain of Myristoylated Alanine Rich C-Kinase Substrate (MARCKS). These data would suggest that MARCKS could also localize to the nucleus. A single report demonstrated immunofluorescence staining of MARCKS in the nucleus; however, further experimental evidence confirming the specific domain responsible for this localization has not been reported. Here, we report that MARCKS is present in the nucleus in GBM cell lines. We then over-expressed wild-type MARCKS (WT) and MARCKS with the effector domain deleted (ΔED), both tagged with V5-epitope in a GBM cell line with low endogenous MARCKS expression (U87). We found that MARCKS-WT localized to the nucleus, while the MARCKS construct without the effector domain remained in the cytoplasm. We also found that over-expression of MARCKS-WT resulted in a significant increase in total cellular phosphatidyl-inositol (4,5) bisphosphate (PIP₂) levels, consistent with prior evidence that MARCKS can regulate PIP₂ levels. We also found increased staining for PIP₂ in the nucleus with MARCKS-WT over-expression compared to MARCKS ΔED by immunofluorescence. Interestingly, we observed MARCKS and PIP₂ co-localization in the nucleus. Lastly, we found changes in gene expression when MARCKS was not present in the nucleus (MARCKS ΔED). These data indicate that the MARCKS effector domain can function as a nuclear localization signal and that this sequence is critical for the ability of MARCKS to regulate PIP₂ levels, nuclear localization, and gene expression. These data suggests a novel role for MARCKS in regulating nuclear functions such as gene expression.

Global Analysis of Mouse Polyomavirus Infection Reveals Dynamic Regulation of Viral and Host Gene Expression and Promiscuous Viral RNA Editing

Mouse polyomavirus (MPyV) lytically infects mouse cells, transforms rat cells in culture, and is highly oncogenic in rodents. We have used deep sequencing to follow MPyV infection of mouse NIH3T6 cells at various times after infection and analyzed both the viral and cellular transcriptomes. Alignment of sequencing reads to the viral genome illustrated the transcriptional profile of the early-to-late switch with both early-strand and late-strand RNAs being transcribed at all time points. A number of novel insights into viral gene expression emerged from these studies, including the demonstration of widespread RNA editing of viral transcripts at late times in infection. By late times in infection, 359 host genes were seen to be significantly upregulated and 857 were downregulated. Gene ontology analysis indicated transcripts involved in translation, metabolism, RNA processing, DNA methylation, and protein turnover were upregulated while transcripts involved in extracellular adhesion, cytoskeleton, zinc finger binding, SH3 domain, and GTPase activation were downregulated. The levels of a number of long noncoding RNAs were also altered. The long noncoding RNA MALAT1, which is involved in splicing speckles and used as a marker in many late-stage cancers, was noticeably downregulated, while several other abundant noncoding RNAs were strongly upregulated. We discuss these results in light of what is currently known about the MPyV life cycle and its effects on host cell growth and metabolism.

Mouse polyomavirus (MPyV) is a small 5.3kb circular double-stranded DNA virus capable of causing tumors in a variety of tissues in immunocompromised mice. It has been a subject of study for over 60 years, yielding insights into a number of processes including tumorigenesis, cell cycle signaling, and transformation. This study serves to provide a global view of the MPyV infection by utilizing Illumina sequencing to observe changes in total RNA from both the virus and the host cell as well as applying new methods to more directly confirm the extent of A-to-I editing of viral RNA by host ADAR enzymes. This allows for a simultaneous observation of both host and viral transcriptional changes that occur as a result of early gene expression and the viral switch from early to late genes that occurs coincident with the initiation of DNA replication.

Mutations in POLE and survival of colorectal cancer patients--link to disease stage and treatment

Recent molecular profiling studies reported a new class of ultramutated colorectal cancers (CRCs), which are caused by exonuclease domain mutations (EDMs) in DNA polymerase ϵ (POLE). Data on the clinical implications of these findings as to whether these mutations define a unique CRC entity with distinct clinical outcome are lacking. We performed Sanger sequencing of the POLE exonuclease domain in 431 well-characterized patients with microsatellite stable (MSS) CRCs of a population-based patient cohort. Mutation data were analyzed for associations with major epidemiological, clinical, genetic, and pathological parameters including overall survival (OS) and disease-specific survival (DSS). In 373 of 431 MSS CRC, all exons of the exonuclease domain were analyzable. Fifty-four mutations were identified in 46 of these samples (12.3%). Besides already reported EDMs, we detected many new mutations in exons 13 and 14 (corresponding to amino acids 410-491) as well as in exon 9 and exon 11 (corresponding to aa 268-303 and aa 341-369). However, we did not see any significant associations of EDMs with clinicopathological parameters, including sex, age, tumor location and tumor stage, CIMP, KRAS, and BRAF mutations. While with a median follow-up time of 5.0 years, survival analysis of the whole cohort revealed nonsignificantly different adjusted hazard ratios (HRs) of 1.35 (95% CI: 0.82-2.25) and 1.44 (0.81-2.58) for OS and DSS indicating slightly impaired survival of patients with EDMs, subgroup analysis for patients with stage III/IV disease receiving chemotherapy revealed a statistically significantly increased adjusted HR (1.87; 95%CI: 1.02-3.44). In conclusion, POLE EDMs do not appear to define an entirely new clinically distinct disease entity in CRC but may have prognostic or predictive implications in CRC subgroups, whose significance remains to be investigated in future studies.