The downregulation of onzin expression by PKCɛ-ERK2 signaling and its potential role in AML cell differentiation

Phospholipid scramblase 1: a protein with multiple functions via multiple molecular interactors

Phospholipid scramblase 1 (PLSCR1) is the most studied protein of the scramblase family. Originally, it was identified as a membrane protein involved in maintaining plasma membrane asymmetry. However, studies conducted over the past few years have shown the involvement of PLSCR1 in several other cellular pathways. Indeed, PLSCR1 is not only embedded in the plasma membrane but is also expressed in several intracellular compartments where it interacts with a diverse repertoire of effectors, mediators, and regulators contributing to distinct cellular processes. Although most PLSCR1 interactors are thought to be cell-type specific, PLSCR1 often exerts its regulatory functions through shared mechanisms, including the trafficking of different molecules within intracellular vesicles such as endosomes, liposomes, and phagosomes. Intriguingly, besides endogenous proteins, PLSCR1 was also reported to interact with exogenous viral proteins, thereby regulating viral uptake and spread. This review aims to summarize the current knowledge about the multiple roles of PLSCR1 in distinct cellular pathways.

Multifaced roles of PLAC8 in cancer

The role of PLAC8 in tumorigenesis has been gradually elucidated with the development of research. Although there are common molecular mechanisms that enforce cell growth, the impact of PLAC8 is varied and can, in some instances, have opposite effects on tumorigenesis. To systematically understand the role of PLAC8 in tumors, the molecular functions of PLAC8 in cancer will be discussed by focusing on how PLAC8 impacts tumorigenesis when it arises within tumor cells and how these roles can change in different stages of cancer progression with the ultimate goal of suppressing PLAC8-relevant cancer behavior and related pathologies. In addition, we highlight the diversity of PLAC8 in different tumors and its functional output beyond cancer cell growth. The comprehension of PLAC8's molecular function might provide new target and lead to the development of novel anticancer therapies.

MAT2A as Key Regulator and Therapeutic Target in MLLr Leukemogenesis

Epigenetic dysregulation plays a pivotal role in mixed-lineage leukemia (MLL) pathogenesis, therefore serving as a suitable therapeutic target. S-adenosylmethionine (SAM) is the universal methyl donor in human cells and is synthesized by methionine adenosyltransferase 2A (MAT2A), which is deregulated in different cancer types. Here, we used our human CRISPR/Cas9-MLL-rearranged (CRISPR/Cas9-MLLr) leukemia model, faithfully mimicking MLLr patients’ pathology with indefinite growth potential in vitro, to evaluate the unknown role of MAT2A. Comparable to publicly available patient data, we detected MAT2A to be significantly overexpressed in our CRISPR/Cas9-MLLr model compared to healthy controls. By using non-MLLr and MLLr cell lines and our model, we detected an MLLr-specific enhanced response to PF-9366, a new MAT2A inhibitor, and small interfering (si) RNA-mediated knockdown of MAT2A, by alteration of the proliferation, viability, differentiation, apoptosis, cell cycling, and histone methylation. Moreover, the combinational treatment of PF-9366 with chemotherapy or targeted therapies against the SAM-dependent methyltransferases, disruptor of telomeric silencing 1 like (DOT1L) and protein arginine methyltransferase 5 (PRMT5), revealed even more pronounced effects. In summary, we uncovered MAT2A as a key regulator in MLL leukemogenesis and its inhibition led to significant anti-leukemic effects. Therefore, our study paves the avenue for clinical application of PF-9366 to improve the treatment of poor prognosis MLLr leukemia.

Placenta-Specific 8 Is Overexpressed and Regulates Cell Proliferation in Low-Grade Human Pancreatic Neuroendocrine Tumors

BACKGROUND/AIMS

Many aspects of the biology of pancreatic neuroendocrine tumors (PanNETs), including determinants of proliferative, invasive, and metastatic potential, remain poorly understood. Placenta-specific 8 (PLAC8), a gene with unknown molecular function, has been reported to have tumor-promoting roles in different human malignancies, including exocrine pancreatic cancer. Since preliminary data suggested deregulation of PLAC8 expression in PanNET, we have performed detailed analyses of PLAC8 expression and function in human PanNET.

METHODS

Primary tissue from PanNET patients was immunohistochemically stained for PLAC8, and expression was correlated with clinicopathological data. In vitro, PLAC8 expression was inhibited by siRNA transfection in PanNET cell lines and effects were analyzed by qRT-PCR, Western blot, and proliferation assays.

RESULTS

We report that PLAC8 is expressed in the majority of well-differentiated human PanNETs, predominantly in early-stage and low-grade tumors. SiRNA-mediated knockdown of PLAC8 in PanNET cells resulted in decreased proliferation and viability, while apoptosis was not induced. Mechanistically, these effects were mediated by attenuation of cell cycle progression, as Western blot analyses demonstrated upregulation of the tumor suppressor p21/CDKN2A and downregulation of the cell cycle regulator Cyclin D1 as well as reduced levels of phosphorylated ribosomal protein s6 and retinoblastoma protein.

CONCLUSION

Our findings establish PLAC8 as a central mediator of cell growth in a subset of human PanNET, providing evidence for the existence of distinct molecular subtypes within this class of tumors.

Placenta-specific protein 8 promotes the proliferation of lung adenocarcinoma PC-9 cells and their tolerance to an epidermal growth factor receptor tyrosine kinase inhibitor by activating the ERK signaling pathway

Placenta-specific protein 8 (PLAC8) is a conserved protein with a molecular weight of 12.5 kDa. The specific function of this protein has not been fully elucidated, however, PLAC8 has been found to play an important tumor regulatory role in certain types of cancer, including colon, pancreatic and liver cancer. PLAC8 also participates in the regulation of the cell cycle, autophagy, epithelial-mesenchymal transition and other cellular functions, indicating its potential as a molecular target worth further investigation. The present study investigated the effect of PLAC8 on the proliferation of lung adenocarcinoma PC-9 cells and their sensitivity to gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). It was found that the inhibition of PLAC8 expression in PC-9 cells resulted in significantly decreased proliferation, whereas overexpression of PLAC8 significantly increased the proliferation (P<0.05) of PC-9 cells. Furthermore, inhibition of PLAC8 expression resulted in decreased activity of the ERK signaling pathway, while PLAC8 overexpression increased activity of this pathway. Inhibition of the ERK signaling pathway with U0126 reversed the effects induced by inhibiting or overexpressing PLAC8 on cell proliferation. In addition, overexpression of PLAC8 significantly decreased the sensitivity of PC-9 cells to gefitinib, and this effect was reversed by U0126. Overall, these results suggest that PLAC8 is involved in the regulation of proliferation of lung adenocarcinoma PC-9 cells and impacts their sensitivity to an EGFR-TKI. Thus, PLAC8 is a potential novel target in lung adenocarcinoma for future studies.

Yeast expression of mammalian Onzin and fungal FCR1 suggests ancestral functions of PLAC8 proteins in mitochondrial metabolism and DNA repair

The cysteine-rich PLAC8 domain of unknown function occurs in proteins found in most Eukaryotes. PLAC8-proteins play important yet diverse roles in different organisms, such as control of cell proliferation in animals and plants or heavy metal resistance in plants and fungi. Mammalian Onzin can be either pro-proliferative or pro-apoptotic, depending on the cell type, whereas fungal FCR1 confers cadmium tolerance. Despite their different role in different organisms, we hypothesized common ancestral functions linked to the PLAC8 domain. To address this hypothesis, and to investigate the molecular function of the PLAC8 domain, murine Onzin and fungal FCR1 were expressed in the PLAC8-free yeast Saccharomyces cerevisiae. The two PLAC8-proteins localized in the nucleus and induced almost identical phenotypes and transcriptional changes when exposed to cadmium stress. Like FCR1, Onzin also reduced DNA damage and increased cadmium tolerance by a DUN1-dependent pathway. Both proteins activated transcription of ancient mitochondrial pathways such as leucine and Fe-S cluster biosynthesis, known to regulate cell proliferation and DNA repair in yeast. These results strongly suggest a common ancestral function of PLAC8 proteins and open new perspectives to understand the role of the PLAC8 domain in the cellular biology of Eukaryotes.

Revising the PLAC8 gene family: from a central role in differentiation, proliferation, and apoptosis in mammals to a multifunctional role in plants

PLAC8 is a cysteine-rich protein described as a central mediator of tumor evolution in mammals; as such, it represents a promising candidate for diagnostic and therapeutic targeting. The human PLAC8 gene is also involved in contact hypersensitivity response and presents a role in psoriatic skin. In plants, PLAC8 motif-containing proteins are involved in the determination of organ size and growth, response to infection, Ca2+ influx, Cd resistance, and zinc detoxification. In general, PLAC8 motif-containing proteins present the conserved CCXXXXCPC or CLXXXXCPC region. However, there is no devised nomenclature for the PLAC8 motif-containing proteins. Here, through the analysis of 445 sequences, we show that PLAC8 motif-containing proteins constitute a unique gene family, and we propose a unified nomenclature. This is the first report indicating the existence of different groups of PLAC8 proteins, which we have called types I, II, and III. Type I genes are found in mammals, fungi, plants, and algae, and types II and III are exclusive to plants. Our study describes for the first time PLAC8 type III proteins. Whether these sequences maintain their known functional role or possess distinct functions of types I and II genes remains unclear.

Placenta specific 8 gene induces epithelial-mesenchymal transition of nasopharyngeal carcinoma cells via the TGF-β/Smad pathway

The present study aimed to investigate the effects and mechanisms of PLAC8 on the epithelial-mesenchymal transition (EMT) of Nasopharyngeal carcinoma (NPC). The expression of PLAC8 in NPC and nasopharyngitis (NPG) tissues from 150 patients was determined using immunohistochemistry. The levels of PLAC8 in five NPC cell lines and nasopharyngeal permanent epithelial cell line were measured using western blotting. We then knocked out or overexpressed PLAC8 in CNE2 cells. Cell proliferation, wound healing, migration, and invasion assays were used to analyze the effects of PLAC8 on the proliferation, migration, and invasion in vivo and vitro. The results showed that the expression of PLAC8 was much higher in NPC tissues than in NPG tissues. The expression of PLAC8 was higher in all the cell lines than in the nasopharyngeal permanent epithelial cells. PLAC8 knockout resulted in significant decreases in cell proliferation, migration, and invasion; associated with lower protein levels of N-cadherin; and increased levels of E-cadherin. Overexpression of PLAC8 had the opposite effect. Furthermore, knockout of PLAC8 inactivated TGF-β/SMAD signaling pathway and suppressed the growth of NPC xenografts. PLAC8 may promote the carcinogenesis and EMT of NPC via the TGF-β/Smad pathway, which suggests that PLAC8 may be a potential biomarker for NPC.

The novel KLF4/PLAC8 signaling pathway regulates lung cancer growth

Accumulating evidence suggests that placenta-specific 8 (PLAC8) plays an important role in normal cellular process and human diseases, including multiple types of human tumors, and its role is highly relied upon in cellular and physiologic contexts. However, there are no reports on its expression profile and biological roles during lung cancer development. In the current study, both the clinical implications and biological effects of PLAC8 in lung cancer (LC) progression were investigated, and we identified and described the novel Krüppel-like factor 4 (KLF4)/PLAC8 regulatory pathway in cancer progression. Elevated PLAC8 levels were positively correlated with tumor size, histological grade, and tumor node metasis (TNM) stage, and LC patients with high PLAC8 expression suffered poor outcomes. In vitro and in vivo assays further revealed that endogenous PLAC8 promoted cell proliferation and tumor formation. We also found downregulated PLAC8 protein in several LC cell lines following the induction of KLF4, and immunohistochemistry analysis of LC tissues by microarray indicated a potential inverse correlation between PLAC8 and KLF4 expression. Luciferase reporter analysis and chromatin immunoprecipitation assays determined that KLF4 negatively regulated PLAC8 promoter activity via directly binding to the promoter region. Furthermore, the growth inhibition resulting from KLF4 overexpression was partially rescued by ectopic PLAC8 expression. Together, our data uncovered a previously unidentified role of PLAC8 as a central mediator in LC progression. PLAC8 was transcriptionally repressed by KLF4, and the novel KLF4/PLAC8 axis may act as a promising candidate target for LC diagnosis and therapy.

Radiation resistance of the lung adenocarcinoma is related to the AKT-Onzin-POU5F1 axis

Non-small cell lung carcinoma is the predominant type of lung cancer, and shows an easily developable tolerance to radiotherapy. Cancer stem cells are suggested to be involved in the resistance against therapies. Onzin might be accumulated during the process tumor overcoming the radiation stress. To address the relationship between Onzin, stemness and radiation resistance, we treated the lung cancer tumor bearing mice with radiaotherapy and observed the differences between radiation sensitive (RS) and resistant (RR) tumors. Immunohistochemistry and HE staining were used to observe Onzin and POU5F1 expression in tumor tissues. Quantitative realtime-PCR and Western blot were applied for Onzin and POU5F1 in tumors and cells. In-vitro cellular viability was assessed by CCK8 methods for tumor derived cells. The stably transfected A549 cell lines overexpressing Onzin were generated through lentivirus transfection. After radiotherapy, those RR adenocarcinoma tumors and cells derived from them showed an increased Onzin expression. Further, RR cells were found upregulated stemness, indicated by increased sphericity and proliferation, as well as POU5F1 expression. Next, we overexpressed Onzin in the A549 cells and found an elevated POU5F1 expression, increased proliferation, and enhanced sphericity. Moreover, this could be suppressed by the AKT inhibitor MK-2260. In vivo, the A549 cells overexpressing Onzin showed not only higher tumor formation capability and growth, but also a significant resistance to radiation. Taken together, RR tumors have upregulated Onzin and POU5F1 expression. Ectopic expression of Onzin promotes the POU5F1 expression as well as stemness functions, and confers adenocarcinomas the resistance to radiotherapy.

PLAC8, a new marker for human interstitial extravillous trophoblast cells, promotes their invasion and migration

Proper differentiation of trophoblast cells in the human placenta is a prerequisite for a successful pregnancy, and dysregulation of this process may lead to malignant pregnancy outcomes, such as preeclampsia. Finding specific markers for different types of trophoblast cells is essential for understanding trophoblast differentiation. Here, we report that placenta-specific protein 8 (PLAC8) is specifically expressed in the interstitial extravillous trophoblast cells (iEVTs) on the fetomaternal interface. Using model systems, including placental villi-decidua co-culture, iEVTs induction by using primary trophoblast cells or explants, etc., we found that PLAC8 promotes invasion and migration of iEVTs. Mechanistically, time-lapse imaging, GTPase activity assay, co-immunoprecipitation and RNA-seq studies show that PLAC8 increases the Cdc42 and Rac1 activities, and further induces the formation of filopodia at the leading edge of the migratory trophoblast cells. More interestingly, PLAC8 is significantly upregulated under hypoxia and expression of PLAC8 is higher in iEVTs from preeclamptic placentas when compared with those from the normal control placentas. Together, PLAC8 is a new marker for iEVTs and plays an important role in promoting trophoblast invasion and migration.

Highlighted Article: Oxygen tension-dependent expression of placenta-specific protein 8 positively regulates trophoblast invasion and migration partially through upregulating the activation of Rac1 and Cdc42.

Protein Kinase C Epsilon Is a Key Regulator of Mitochondrial Redox Homeostasis in Acute Myeloid Leukemia

Purpose: The intracellular redox environment of acute myeloid leukemia (AML) cells is often highly oxidized compared to healthy hematopoietic progenitors and this is purported to contribute to disease pathogenesis. However, the redox regulators that allow AML cell survival in this oxidized environment remain largely unknown.Experimental Design: Utilizing several chemical and genetically-encoded redox sensing probes across multiple human and mouse models of AML, we evaluated the role of the serine/threonine kinase PKC-epsilon (PKCε) in intracellular redox biology, cell survival and disease progression.Results: We show that RNA interference-mediated inhibition of PKCε significantly reduces patient-derived AML cell survival as well as disease onset in a genetically engineered mouse model (GEMM) of AML driven by MLL-AF9. We also show that PKCε inhibition induces multiple reactive oxygen species (ROS) and that neutralization of mitochondrial ROS with chemical antioxidants or co-expression of the mitochondrial ROS-buffering enzymes SOD2 and CAT, mitigates the anti-leukemia effects of PKCε inhibition. Moreover, direct inhibition of SOD2 increases mitochondrial ROS and significantly impedes AML progression in vivo Furthermore, we report that PKCε over-expression protects AML cells from otherwise-lethal doses of mitochondrial ROS-inducing agents. Proteomic analysis reveals that PKCε may control mitochondrial ROS by controlling the expression of regulatory proteins of redox homeostasis, electron transport chain flux, as well as outer mitochondrial membrane potential and transport.Conclusions: This study uncovers a previously unrecognized role for PKCε in supporting AML cell survival and disease progression by regulating mitochondrial ROS biology and positions mitochondrial redox regulators as potential therapeutic targets in AML. Clin Cancer Res; 24(3); 608-18. ©2017 AACR.

Effects of miR-23b on hypoxia-induced cardiomyocytes apoptosis

OBJECTIVES

The aim of this study was to investigate the role of miR-23b in hypoxic cardiomyocytes and the potential mechanism.

METHODS

Myocardial samples of patients with cyanotic or acyanotic congenital heart disease (CHD) were collected to evaluate miR-23b expression. Agomir or antagomir of miR-23b was transfected into H9C2 cells. MTT, LDH assay and TUNEL staining were used to determine the cell proliferation and apoptosis under hypoxic conditions. Besides, the expression levels of cleaved-caspase-3, cleaved-PARP, Bad, Bcl-2 and Bax in hypoxic H9C2 cells were determined by western blot and qRT-PCR, respectively.

RESULTS

Higher miR-23b expression levels were found in the patients with cyanotic CHD compared with the patients with acyanotic CHD. In addition, the expression of miR-23b was gradually up-regulated with prolonged hypoxia time in the H9C2 cells. Using MTT and LDH assays, cell growth was significantly decreased in the agomir group than that in the agomir-negative control (NC) group, while antagomir increased the cell growth. Using TUNEL staining and flow cytometry analysis, miR-23b promoted hypoxia-induced apoptosis. The expression levels of pro-apoptotic proteins, such as cleaved-caspase-3, cleaved-PARP and Bad, were significantly increased in the agomir group, while the Bcl-2 levels and Bcl-2/Bax ratio were decreased. Opposite tendency was observed in the antagomir group. Dual luciferase reporter assay and western blot analysis confirmed that Smad3 was a direct target of miR-23b.

CONCLUSION

Over-expression of miR-23b may increase cardiomyocyte apoptosis and reduce cell growth under hypoxic conditions.

Roles of microRNA let-7b in papillary thyroid carcinoma by regulating HMGA2

The incidence of thyroid cancer has increased significantly in the last decade, and the most frequent type of this cancer is papillary thyroid carcinoma. MicroRNAs have been demonstrated to be abnormally expressed in tumors and associated with the development of the tumors. Our aim was to analyze the role and molecular mechanisms of tumor suppressor let-7b in the papillary thyroid carcinoma. Expression of let-7b and high-mobility group A2 in papillary thyroid carcinoma tissues and cell lines was assessed using quantitative reverse transcription polymerase chain reaction and western blot analysis. To explore the role of let-7b or high-mobility group A2 in the BCPAP and TPC-1 cells, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and Transwell methods were used. Let-7b expression was significantly downregulated while expression of high-mobility group A2 was upregulated dramatically in papillary thyroid carcinoma tissues and cells compared with that in normal thyroid tissues and cells. In addition, overexpression of let-7b or knockdown of high-mobility group A2 inhibited cell migration and invasion compared with that of control. Besides, high-mobility group A2 was negatively regulated by let-7b in BCPAP cells. Moreover, high-mobility group A2 reintroduction reversed the anti-proliferation, anti-migration, and anti-invasion roles of let-7b. Let-7b might function as a tumor suppressor in papillary thyroid carcinoma by suppressing the expression of high-mobility group A2, and therefore might provide a promising therapeutic target for patients with papillary thyroid carcinoma.

Overexpression of placenta specific 8 is associated with malignant progression and poor prognosis of clear cell renal cell carcinoma

BACKGROUND

Placenta specific 8 (PLAC8) plays an important role in many different cellular processes and human diseases, including multiple types of cancer. However, the functional role of PLAC8 in clear cell renal cell carcinoma (ccRCC) has never been elucidated.

METHODS

PLAC8 mRNA expression was investigated in 31 pairs of fresh ccRCC tumor tissues and matched adjacent non-tumor tissues by RT-qPCR and confirmed by analyzing the TCGA KRCC dataset which contains RNA-seq data of 534 ccRCC and 72 solid normal tissues. Protein level of PLAC8 expression was also investigated using immunohistochemistry in 129 ccRCC samples. Correlations with clinicopathological factors and overall survival were analyzed. To examine its effect on the biological activity, PLAC8 siRNAs were transfected into ccRCC cells. Cell proliferation was assessed by CCK8 cell viability assays, clone formation assays, and EdU incorporation assays. Cell invasion was examined using transwell assays. RNA sequencing was then performed to further elucidate the mechanisms by which PLAC8 regulates the cancer.

RESULTS

PLAC8 expression was positively correlated with tumor size, metastasis, and clinical stage of ccRCC. Additionally, high PLAC8 expression was closely associated with a shorter overall survival time. Knockdown of PLAC8 with siRNAs significantly reduced the proliferation and invasion of RCC cells and increased the sensitivity of RCC cells to cisplatin. RNA-seq analysis revealed that knockdown of PLAC8 down-regulated the expression of a panel of inflammatory mediators, which suggested that PLAC8 is associated with the ccRCC inflammatory microenvironment. Patients with high expression of PLAC8 had a significantly higher number of infiltrative lymphocytes than patients with low expression of PLAC8.

CONCLUSION

Our findings suggest that PLAC8 may be a potential prognostic indicator and therapeutic target for ccRCC.

Transcriptome Display During Testicular Differentiation of Channel Catfish (Ictalurus punctatus) as Revealed by RNA-Seq Analysis

Channel catfish (Ictalurus punctatus) has been recognized as a dominant freshwater aquaculture species in the United States. It is also a suitable model for studying the mechanisms of sex determination and differentiation because of its sexual plasticity and exhibition of both genetic and environmental sex determination. The testicular differentiation in male channel catfish normally starts between 90 and 102 days postfertilization (dpf), while the ovarian differentiation starts early from 19 dpf. As such, efforts to better understand the postponed testicular development at the molecular level are needed. Toward that end, we conducted transcriptomic comparison of gene expression of male and female gonads at 90, 100, and 110 dpf using high-throughput RNA-Seq. Transcriptomic profiles of male gonads on 90 and 100 dpf exhibited high similarities except for a small number of significantly up-regulated genes that were involved in development of germ cell-supporting somatic cells, while drastic changes were observed during 100-110 dpf, with a group of highly up-regulated genes that were involved in germ cells development, including nanog and pou5f1 Transcriptomic comparison between testes and ovaries identified male-preferential genes, such as gsdf, cxcl12, as well as other cytokines mediated the development of the gonad into a testis. Co-expression analysis revealed highly correlated genes and potential pathways underlying germ cell differentiation and spermatogonia stem cell development. The candidate genes and pathways identified in this study set the foundation for further studies on sex determination and differentiation in catfish as well as other teleosts.

Analysis of regulatory T cells frequency in peripheral blood and tumor tissues in papillary thyroid carcinoma with and without Hashimoto's thyroiditis

PURPOSE

Regulatory T cells (Treg) suppress the immune reaction. The aim of the present study was to investigate the clinicopathologic significance and roles of Treg in papillary thyroid carcinoma (PTC) patients with and without Hashimoto's thyroiditis.

METHODS

Flow cytometry was used to detect the percentage of CD4+CD25+CD127low/- Treg among CD4+ T cells in peripheral blood. FoxP3+ Treg were detected by immunohistochemistry in the tumor tissues.

RESULTS

The percentage of CD4+CD25+CD127low/- Treg among CD4+ T cells was significantly higher in PTC patients than that in multinodular goiter (MNG) patients. There were large numbers of tumor-infiltrating FoxP3+ Treg in primary PTC and metastatic lymph nodes tissues; however, there was no FoxP3 expression in the MNG tissues. Higher percentage of Treg both in peripheral blood and tumor tissues was associated with extrathyroidal extension and lymph nodes metastasis. The percentage of CD4+CD25+CD127low/- Treg among CD4+ T cells in peripheral blood of PTC patients with Hashimoto's thyroiditis (HT) was significantly lower, whereas the infiltration of FoxP3+ Treg in tissues of PTC with HT tended to be increased.

CONCLUSIONS

We concluded that the percentage of Treg increased in peripheral blood as well as in the tumor tissues of PTC patients compared with that of MNG patients. The high percentage of Treg was associated with aggressiveness. There may be a compensatory expansion of Treg at the sites of inflammation in tissues of PTC with HT contributing to the immune response suppression.

Plac8 links oncogenic mutations to regulation of autophagy and is critical to pancreatic cancer progression

Mutations in p53 and RAS potently cooperate in oncogenic transformation, and correspondingly, these genetic alterations frequently coexist in pancreatic ductal adenocarcinoma (PDA) and other human cancers. Previously, we identified a set of genes synergistically activated by combined RAS and p53 mutations as frequent downstream mediators of tumorigenesis. Here, we show that the synergistically activated gene Plac8 is critical for pancreatic cancer growth. Silencing of Plac8 in cell lines suppresses tumor formation by blocking autophagy, a process essential for maintaining metabolic homeostasis in PDA, and genetic inactivation in an engineered mouse model inhibits PDA progression. We show that Plac8 is a critical regulator of the autophagic machinery, localizing to the lysosomal compartment and facilitating lysosome-autophagosome fusion. Plac8 thus provides a mechanistic link between primary oncogenic mutations and the induction of autophagy, a central mechanism of metabolic reprogramming, during PDA progression.

Identification of verrucarin a as a potent and selective steroid receptor coactivator-3 small molecule inhibitor

Members of the steroid receptor coactivator (SRC) family are overexpressed in numerous types of cancers. In particular, steroid receptor coactivator 3 (SRC-3) has been recognized as a critical coactivator associated with tumor initiation, progression, recurrence, metastasis, and chemoresistance where it interacts with multiple nuclear receptors and other transcription factors to enhance their transcriptional activities and facilitate cross-talk between pathways that stimulate cancer progression. Because of its central role as an integrator of growth signaling pathways, development of small molecule inhibitors (SMIs) against SRCs have the potential to simultaneously disrupt multiple signal transduction networks and transcription factors involved in tumor progression. Here, high-throughput screening was performed to identify compounds able to inhibit the intrinsic transcriptional activities of the three members of the SRC family. Verrucarin A was identified as a SMI that can selectively promote the degradation of the SRC-3 protein, while affecting SRC-1 and SRC-2 to a lesser extent and having no impact on CARM-1 and p300 protein levels. Verrucarin A was cytotoxic toward multiple types of cancer cells at low nanomolar concentrations, but not toward normal liver cells. Moreover, verrucarin A was able to inhibit expression of the SRC-3 target genes MMP2 and MMP13 and attenuated cancer cell migration. We found that verrucarin A effectively sensitized cancer cells to treatment with other anti-cancer drugs. Binding studies revealed that verrucarin A does not bind directly to SRC-3, suggesting that it inhibits SRC-3 through its interaction with an upstream effector. In conclusion, unlike other SRC SMIs characterized by our laboratory that directly bind to SRCs, verrucarin A is a potent and selective SMI that blocks SRC-3 function through an indirect mechanism.

Let-7b expression determines response to chemotherapy through the regulation of cyclin D1 in glioblastoma

Background

Glioblastoma is the most common type of primary brain tumors. Cisplatin is a commonly used chemotherapeutic agent for Glioblastoma patients. Despite a consistent rate of initial responses, cisplatin treatment often develops chemoresistance, leading to therapeutic failure. Cellular resistance to cisplatin is of great concern and understanding the molecular mechanisms is an utter need.

Methods

Glioblastoma cell line U251 cells were exposed to increasing doses of cisplatin for 6 months to establish cisplatin-resistant cell line U251R. The differential miRNA expression profiles in U251 and U251R cell lines were identified by microarray analysis and confirmed by Q-PCR. MiRNA mimics were transfected into U251R cells, and cellular response to cisplatin-induced apoptosis and cell cycle distribution were examined by FACS analysis.

Results

U251R cells showed 3.1-fold increase in cisplatin resistance compared to its parental U251 cells. Microarray analysis identified Let-7b and other miRNAs significantly down-regulated in U251R cells compared to U251 cells. Transfection of Let-7b mimics greatly re-sensitized U251R cells to cisplatin, while transfection of other miRNAs has no effect or slightly effect. Cyclin D1 is predicted as a target of Let-7b through bioinformatics analysis. Over-expression of Let-7b mimics suppressed cyclin D1 protein expression and inhibited cyclin D1-3’-UTR luciferase activity. Knockdown of cyclin D1 expression significantly increased cisplatin-induced G1 arrest and apoptosis.

Conclusions

Collectively, our results indicated that cisplatin treatment leads to Let-7b suppression, which in turn up-regulates cyclin D1 expression. Let-7b may serve as a marker of cisplatin resistance, and can enhance the therapeutic benefit of cisplatin in glioblastoma cells.

Plac8-dependent and inducible NO synthase-dependent mechanisms clear Chlamydia muridarum infections from the genital tract

Chlamydia trachomatis urogenital serovars replicate predominantly in genital tract epithelium. This tissue tropism poses a unique challenge for host defense and vaccine development. Studies utilizing the Chlamydia muridarum mouse model have shown that CD4 T cells are critical for clearing genital tract infections. In vitro studies have shown that CD4 T cells terminate infection by upregulating epithelial inducible NO synthase (iNOS) transcription and NO production. However, this mechanism is not critical, as iNOS-deficient mice clear infections normally. We recently showed that a subset of Chlamydia-specific CD4 T cell clones could terminate replication in epithelial cells using an iNOS-independent mechanism requiring T cell degranulation. We advance that work using microarrays to compare iNOS-dependent and iNOS-independent CD4 T cell clones. Plac8 was differentially expressed by clones having the iNOS-independent mechanism. Plac8-deficient mice had delayed clearance of infection, and Plac8-deficient mice treated with the iNOS inhibitor N-monomethyl-l-arginine were largely unable to resolve genital tract infections over 8 wk. These results demonstrate that there are two independent and redundant T cell mechanisms for clearing C. muridarum genital tract infections: one dependent on iNOS, and the other dependent on Plac8. Although T cell subsets are routinely defined by cytokine profiles, there may be important subdivisions by effector function, in this case CD4(Plac8).

Plac8 is an inducer of C/EBPβ required for brown fat differentiation, thermoregulation, and control of body weight

Brown adipocytes oxidize fatty acids to produce heat in response to cold or to excessive energy intake; stimulation of brown fat development and function may thus counteract obesity. Brown adipogenesis requires activation of the transcription factor C/EBPβ and recruitment of the zinc finger protein Prdm16, but upstream inducers of these proteins are incompletely defined. Here, we show that genetic inactivation of Plac8, a gene encoding an evolutionarily conserved protein, induces cold intolerance, and late-onset obesity, as well as abnormal morphology and impaired function of brown adipocytes. Using brown preadipocyte lines we show that Plac8 is required for brown fat differentiation, that its overexpression induces C/EBPβ and Prdm16, and that upon induction of differentiation Plac8 associates with C/EBPβ and binds to the C/EBPβ promoter to induce its transcription. Thus, Plac8 is a critical upstream regulator of brown fat differentiation and function that acts, at least in part, by inducing C/EBPβ expression.

A PLAC8-containing protein from an endomycorrhizal fungus confers cadmium resistance to yeast cells by interacting with Mlh3p

Cadmium is a genotoxic pollutant known to target proteins that are involved in DNA repair and in antioxidant defence, altering their functions and ultimately causing mutagenic and carcinogenic effects. We have identified a PLAC8 domain-containing protein, named OmFCR, by a yeast functional screen aimed at identifying genes involved in cadmium resistance in the endomycorrhizal fungus Oidiodendron maius. OmFCR shows a remarkable specificity in mediating cadmium resistance. Both its function and its nuclear localization in yeast strictly depend on the interaction with Mlh3p, a subunit of the mismatch repair (MMR) system. Although proteins belonging to the PLAC8 family are widespread in eukaryotes, they are poorly characterized and their biological role still remains elusive. Our work represents the first report about the potential role of a PLAC8 protein in physically coupling DNA lesion recognition by the MMR system to appropriate effectors that affect cell cycle checkpoint pathways. On the basis of cell survival assays and yeast growth curves, we hypothesize that, upon cadmium exposure, OmFCR might promote a higher rate of cell division as compared to control cells.

Ikaros is degraded by proteasome-dependent mechanism in the early phase of apoptosis induction

Ikaros is an important transcription factor involved in the development and differentiation of hematopoietic cells. In this work, we found that chemotherapeutic drugs or ultraviolet radiation (UV) treatment could reduce the expression of full-length Ikaros (IK1) protein in less than 3h in leukemic NB4, Kasumi-1 and Jurkat cells, prior to the activation of caspase-3. Etoposide treatment could not alter the mRNA level of IK1 but it could shorten the half-life of IK1. Co-treatment with the proteasome inhibitor MG132 or epoxomicin but not calpain inhibitor calpeptin inhibited etoposide-induced Ikaros downregulation. Overexpression of IK1 could accelerate etoposide-induced apoptosis in NB4 cells, as evidenced by the increase of Annexin V positive cells and the more early activation of caspase 3. To our knowledge, this is the first report to show that upon chemotherapy drugs or UV treatment, IK1 could be degraded via the proteasome system in the early phase of apoptosis induction. These data might shed new insight on the role of IK1 in apoptosis and the post-translational regulation of IK1.