Coexpression Of C-myc Research Articles

Investigating In Situ Expression of c-MYC and Candidate Ubiquitin-Specific Proteases in DLBCL and Assessment for Peptidyl Disruptor Molecule against c-MYC-USP37 Complex.

Diffuse Large B-Cell Lymphoma (DLBCL) is the most common form of non-Hodgkin's lymphoma (NHL). Elevated expression of c-MYC in DLBCL is associated with poor prognosis of the disease. In different cancers, c-MYC has been found regulated by different ubiquitin-specific proteases (USPs), but to date, the role of USPs in c-MYC regulation has not been investigated in DLBCL. In this study, in situ co expression of c-MYC and three candidates USPs, USP28, USP36 and USP37, have been investigated in both the ABC and GCB subtypes of DLBCL. This shows that USP37 expression is positively correlated with the c-MYC expression in the ABC subtype of DLBCL. Structurally, both c-MYC and USP37 has shown large proportion of intrinsically disordered regions, minimizing their chances for full structure crystallization. Peptide array and docking simulations has shown that N-terminal region of c-MYC interacts directly with residues within and in proximity of catalytically active C19 domain of the USP37. Given the structural properties of the interaction sites in the c-MYC-USP37 complex, a peptidyl inhibitor has been designed. Molecular docking has shown that the peptide fits well in the targeted site of c-MYC, masking most of its residues involved in the binding with USP37. The findings could further be exploited to develop therapeutic interventions against the ABC subtype of DLBCL.

ADHFE1 and C-MYC Association and Over-Expression in Different Stages of Human Breast Cancer Tissues

Chief enantiomer in breast tumors is D-2HG. Mitochondrial Alcohol Dehydrogenase (ADHFE I ) produces D-2HG. lt is the CA breast oncogene which leads to decreased patient survival. c-MYC can upregulate ADHFE I by changes in iron metabolism whereas co expression of c-MYC and ADHFE I greatly augment ort hotopic growth of tumor in MCF7 cells. Aims: To determine the expression levels and localization of c-M yc and ADHFE I in different stages of breast cancer tissue. Study Design: Cross-sectional comparative study. Methodology: Present study was conducted to enhance knowledge of c-Myc function in breast cancer by examination of relation between nuclear c-Myc and iron containing ADHFE I enz yme protein expression, using immunohist cichemistry. All this information was recorded on performa. Statistical analysis: Data was analyzed using SPSS version 25. Analysis of variance (ANOVA) test, was employed to observe mean difference between groups. Results: Nuclear c-Myc and cytoplasmic ADHFE I levels were significantly higher than controls and were positively correlated with each other in advancing stages of breast cancer. Conclusion: It was concluded that the association between the expression levels of c-Myc oncogene and ADHFE-1 enzyme existed in all advancing stages of CA Breast and the expression of both increased as the breast cancer advanced. Keywords: Breast cancer, c-Myc, ADHFE-I and Immunohistochemistry.

Immunohistochemical Characterisation of Cell of Origin in Diffuse Large B-cell Lymphoma and its Association with the Double Expressor Phenotype: A Retrospective Study

Introduction: Diffuse Large B-cell Lymphoma (DLBCL) is the most common type of Non Hodgkin Lymphoma (NHL) and is categorised into the Germinal Centre B-cell (GCB) and Activated B-cell (ABC/Non GCB) subtypes as per the Cell Of Origin (COO) model with the help of gene expression profiling/ immunohistochemistry. The non GCB subtype has been found to associate with the Double Expressor (DE) phenotype (i.e., co-expression of BCL-2 and c-myc by IHC and this association was substantiated and proven to be statistically significant in the present study. Aim: To categorise all DLBCL cases into GCB and Non GCB and further into DE and Non-DE by using Hans and Choi IHC alogrithm. Materials and Methods: A retrospective study of 50 patients was carried out with the help of archival material filed in the Department of Anatomic Pathology at Dharamshila Narayana Superspeciality Hospital, New Delhi, India from 1st January 2019 to 30th June 2020. The study was approved by Instituitional Ethics Committee (IEC). Chi-square test and Yates correction were used for statistical analysis. Results: The study cohort was divided into two Groups- group-A with nodal presentation and group-B with extranodal presentation. By using the Hans and Choi IHC algorithms, the cases were categorised into the GCB and non GCB subtypes in both the groups. The DE phenotype was determined in each case by the co-expression of c-myc (>40%) and BCL-2 (>50%) by IHC. By using the statistical chi-square test analysis and Yates correction, the association of DE was found to be statistically significant with non GCB type lymphomas and non DE with GCB lymphomas with p-value being 0.0005 and 0.00168, respectively. Conclusion: Due to the heterogeneity inherent in DLBCL, prediction of the DE phenotype and the COO by IHC is a sensitive tool and helps in the prognostication and therapeutic triage of patients. Hence, in all the cases diagnosed as DLBCL, a detailed morphological and IHC work up is mandatory to determine prognosis and possibly tailor therapy according to COO and DE phenotype.

WDR5 facilitates EMT and metastasis of CCA by increasing HIF-1α accumulation in Myc-dependent and independent pathways

Cholangiocarcinoma (CCA) is a highly aggressive malignancy with extremely poor prognoses. The oncogenic role and prognostic value of c-Myc in CCA is not well elucidated. WD repeat domain 5 (WDR5) is a critical regulatory factor directly interacting with c-Myc to regulate c-Myc recruitment at chromosomal locations, but the interaction of WDR5 and c-Myc in CCA was uncovered. In our study, we detected WDR5 and c-Myc expression in all CCA types, including intrahepatic (iCCA), perihilar (pCCA), and distal (dCCA) CCA, and evaluated their prognostic significance. Consequently, we demonstrated that WDR5 was significantly correlated with poor prognosis of CCA and that WDR5 and c-Myc co-expression was a more sensitive prognostic factor. With invitro and invivo experiments and bioinformatics, we showed that WDR5 interacted with the Myc box IIIb (MBIIIb) motif of c-Myc and facilitated Myc-induced HIF1A transcription, thereby promoting the epithelial-mesenchymal transition (EMT), invasion, and metastasis of CCA. Moreover, WDR5 enhanced hypoxia-inducible factor 1 subunit α (HIF-1α) accumulation by binding with histone deacetylase 2 (HDAC2) and increasing histone 3 lysine 4 acetylation (H3K4ac) deacetylation of the prolyl hydroxylase domain protein 2 (PHD2) promoter, resulting in the attenuation of chromatin opening and PHD2 expression, and eventually leading to HIF-1α stabilization and accumulation. In conclusion, WDR5 facilitated EMT and metastasis of CCA by increasing HIF-1α accumulation in a Myc-dependent pathway to promote HIF-1α transcription and a Myc-independent pathway to stabilize HIF-1α.

Double-Expressor Phenotype (BCL-2/c-MYC Co-expression) of Diffuse Large B-Cell Lymphoma and Its Clinicopathological Correlation.

IntroductionDiffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease, the spectrum of which is increasing with time. The 2016 World Health Organization (WHO) update on hematopoietic tumors recognized a prognostic subgroup of DLBCL called double-expressor DLBCL. Double-expressor DLBCL is defined by the co-expression of c-MYC and BCL-2 by using immunohistochemical (IHC) studies. To our knowledge, very few studies have looked into the pathological features of this newly defined prognostic category of DLBCL; therefore, in this study we evaluated the frequency of the double-expressor phenotype of DLBCL and its association with other clinicopathological parameters.MethodsWe conducted a retrospective observational study in the Department of Histopathology, Liaquat National Hospital and Medical College, from November 2017 till December 2020. Pathological and clinical records were retrieved from departmental archives. All cases diagnosed as DLBCL were included in the study. More than 40% c-MYC expression in the presence of more than 50% BCL-2 expression was defined as double-expressor DLBCL.ResultsThe mean age of the patients was 52.1±16.9 years. The mean Ki67 index was 73.0±17.0%. A total of 48.6% cases were of germinal center B-cell-like (GCB) subtype, and 59.6% cases were nodal. Double-expressor phenotype was noted in 35.8% of DLBCL cases. A significant association of double-expressor phenotype was noted with age, gender, Ki67 index and subtype of DLBCL. Double-expressor DLBCL had a higher mean age than non-double-expressor DLBCL. Similarly, double-expressor DLBCL had a higher Ki67 index. Moreover, double-expressor phenotype was associated with non-GCB subtype DLBCL.ConclusionWe found a high proportion of double-expressor phenotype DLBCL in our population. Moreover, double-expressor phenotype DLBCL was associated with female gender, higher age, higher Ki67 and non-GCB subtype. The association of double-expressor DLBCL with a high Ki67 index and non-GCB subtype confers a poor prognostic significance of this variant of DLBCL, requiring more aggressive therapy.

Generation of a Murine Model for c-MYC and BCL2 Co-expression B Cell Lymphomas.

Diffuse large B-cell lymphoma (DLBCL) is the most frequent lymphoma in adults, and is characterized as clinically and biologically heterogeneous lymphomas with diverse response to therapy and variation in clinical behavior. It's well-established that c-MYC and BCL2 play important roles in normal B-cell differentiation and tumorigenesis. B cell lymphoma with dual expression of c-MYC and BCL2 (double-expressor lymphoma, DEL) accounts for approximately one-third of DLBCL cases. DEL patients have poor outcomes after chemoimmunotherapy or autologous stem-cell transplantation. Lack of a genetic mouse tool for DEL hinders us from understanding the lymphogenesis mechanism and developing therapeutic strategies. Here, we investigated whether ectopic expression of c-MYC and BCL2 in different stages of B cells could lead to lymphoma and generate a mouse model for DEL. We observed that Co-expression of c-MYC and BCL2 in germinal center (GC) B cells, or pan-B cells could induce B cell lymphomas. The tumor-bearing mice have enlarged lymphoid organs, and B cells massively infiltrate into non-lymphoid organs including lung, liver and kidney. The tumor-bearing mice also manifested significantly shorter lifespan than the controls. In addition, adoptive transfer of Co-expression B cells leads to B cell lymphoma and host mice death. This model will provide us a tool to further explore the pathogenesis and treatment approaches for DEL.

Immunohistochemical overexpression of BCL-2 protein predicts an inferior survival in patients with primary central nervous system diffuse large B-cell lymphoma

This study was designed to analyze the clinical characteristics and prognostic value of c-MYC and BCL-2 proteins expression in patients with primary central nervous system diffuse large B-cell lymphoma (PCNS-DLBCL).82 patients newly diagnosed with PCNS-DLBCL, from January 2008 to November 2018, were enrolled in this study. Clinical characteristics, immunohistochemical features, laboratory examinations, and treatment outcome were analyzed among these patients.Among these 82 cases, 45 were males (54.9%) and 37 were females (45.1%). Age ranged from 16 to 78 years old, and 29 patients (35.4%) were elder than 60 years old, with median age at 57 years old. According to Hans classification, 25 were accounted for origin of germinal center B-cell (GCB) subtype (30.5%) and 49 were accounted for non-GCB subtype (59.8%), respectively. Eight patients were unclassified due to lack of detailed pathological results. The median survival of these 82 patients was 30 months, and 1-year, 3-year, and 5-year overall survival (OS) rate was 59.7%, 44.6%, and 34.1%, respectively. Patients treated with sequential HD-MTX based chemotherapies showed a superior prognosis than those without. In combination with rituximab, the outcome was further improved. The median OS was 55 months in HD-MTX + R group, 27 months in HD-MTX group, and 9 months in other groups, respectively. Univariate analysis identified age ≥60, ECOG score ≥ 2 points, and overexpression of BCL-2 protein (≥85%) were adverse prognostic factors for OS. Co-expression of c-MYC (≥40%) and BCL-2 (≥50%) proteins was associated with poor ECOG score, high Ki-67 expression, and trended towards an inferior outcome. Gender, lesion location, number of lesions, lactic dehydrogenase (LDH), cell of origin, BCL-6 protein expression, expression of c-MYC protein alone and Ki-67 ≥85% had no significant impact on OS.In patients with PCNS-DLBCL, age ≥60 years old, ECOG score ≥2 points, and overexpression of BCL-2 protein (≥85%) were associated with a poor survival. HD-MTX based chemotherapies in combination with rituximab could improve the prognosis.

Clinicopathological features of long-term tumor-free survival of patients with untreated primary tonsillar diffuse large B-cell lymphoma

Objective: To investigate the clinicopathological features of long-term tumor-free survival in patients with untreated primary diffuse large B-cell lymphoma (DLBCL) of the tonsil. Methods: The study included 80 consultation cases of primary tonsillar DLBCL from April 2006 to July 2017 in the Department of Pathology, Beijing Friendship Hospital, Capital Medical University. The patients were divided into two groups: experimental groups of 10 untreated patients with long-term tumor-free survival, and 70 patients who had been treated (control group). The clinical data, histopathological features, immunohistochemical staining, and molecular biology test results of the patients were analyzed retrospectively. Results: Patients who had long-term tumor-free survival with untreated primary diffuse large B-cell lymphoma had the disease mostly confined to the tonsil. Biopsy showed that the tonsil structure was only partially effaced and the lesions were relatively "fresh". EBER and FISH test for t (14;18) results were negative. Gene rearrangement detection showed monoclonality. There was statistically significant difference between the age, bcl-2 expression, CMYC protein expression and co-expression of CMYC and bcl-2 between the untreated group and the treated group(P<0.05). Patient gender, tumor site, histological type and clinical stage showed no difference between the untreated group and the treated group (P>0.05); The median overall survival of the untreated group and treated group was 81 months and 20 months, respectively, and the difference was not statistically significant (P>0.05).In patients younger than 40 years of age, the untreated group had a statistically significant difference in primary site and CMYC protein expression compared with the treated group (P<0.05), and there was no statistical significance in other aspects. Conclusions: Long-term tumor-free survival patients with untreated tonsillar primary DLBCL have relatively unique clinical characteristics. There is no significant difference in the prognosis between the untreated and treated groups, indicating radiotherapy and chemotherapy may not be required and therefore, avoiding related side effects.

Novel cooperative pathway of c-Myc and Furin, a pro-protein convertase, in cell proliferation as a therapeutic target in ovarian cancers.

c-Myc is a master regulator of various oncogenic functions in many types of human cancers. However, direct c-Myc-targeted therapy has not been successful in the clinic. Here, we explored a novel therapeutic target, which shows synthetic lethality in c-Myc-driven ovarian cancers, and examined the molecular mechanism of the synthetic lethal interaction. By high throughput siRNA screening with a library of 6,550 genes, Furin, a pro-protein convertase, was identified as the top hit gene. Furin inhibition by siRNA or a Furin inhibitor significantly suppressed cell proliferation in high c-Myc-expressing ovarian cancer cells compared with low c-Myc-expressing cells. Conversely, Furin overexpression in the presence of high c-Myc significantly promoted cell proliferation compared with only c-Myc or Furin overexpression. Notch1, one of the Furin substrates, was upregulated by c-Myc, and Notch1 cleaved by Furin increased cell proliferation of high c-Myc-expressing ovarian cancer cells. Notch1 was involved in the cooperative pathway of c-Myc and Furin in cell proliferation. In clinical ovarian cancer specimens, co-expression of c-Myc and Furin correlated with poor survival. In conclusion, we found that c-Myc cooperates with Furin to promote cell proliferation. Furin may be a promising therapeutic target in c-Myc-driven ovarian cancer.

Primary central nervous system diffuse large B-cell lymphoma shows an activated B-cell-like phenotype with co-expression of C-MYC, BCL-2, and BCL-6

Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma, whose main prognostic factor is closely related to germinal center B-cell-like subtype (GCB- DLBCL) or activated B-cell-like type (non-GCB-DLBCL). The most common type of primary central nervous system lymphoma is diffuse large B-cell type with poor prognosis and the reason is unclear. This study aims to stratify primary central nervous system diffuse large B-cell lymphoma (PCNS-DLBCL) according to the cell-of-origin (COO) and to investigate the multiple proteins expression of C-MYC, BCL-6, BCL-2, TP53, further to elucidate the reason why primary central nervous system diffuse large B-cell lymphoma possesses a poor clinical outcome as well. Nineteen cases of primary central nervous system DLBCL were stratified according to immunostaining algorithms of Hans, Choi and Meyer (Tally) and we investigated the multiple proteins expression of C-MYC, BCL-6, BCL-2, TP53. The Epstein-Barr virus and Borna disease virus infection were also detected. Among nineteen cases, most (15–17 cases) were assigned to the activated B-cell-like subtype, highly expression of C-MYC (15 cases, 78.9%), BCL-2 (10 cases, 52.6%), BCL-6 (15 cases, 78.9%). Unfortunately, two cases were positive for PD-L1 while PD-L2 was not expressed in any case. Two cases infected with BDV but no one infected with EBV. In conclusion, most primary central nervous system DLBCLs show an activated B-cell-like subtype characteristic and have multiple expressions of C-MYC, BCL-2, BCL-6 protein, these features might be significant factor to predict the outcome and guide treatment of PCNS-DLBCLs.

Favorable prognosis in colorectal cancer patients with co-expression of c-MYC and ß-catenin.

BackgroundThe purpose of our research was to determine the prognostic impact and clinicopathological feature of c-MYC and β-catenin overexpression in colorectal cancer (CRC) patients.MethodsUsing immunohistochemistry (IHC), we measured the c-MYC and β-catenin expression in 367 consecutive CRC patients retrospectively (cohort 1). Also, c-MYC expression was measured by mRNA in situ hybridization. Moreover, to analyze regional heterogeneity, three sites of CRC including the primary, distant and lymph node metastasis were evaluated in 176 advanced CRC patients (cohort 2).ResultsIn cohort 1, c-MYC protein and mRNA overexpression and ß-catenin nuclear expression were found in 201 (54.8 %), 241 (65.7 %) and 221 (60.2 %) of 367 patients, respectively, each of which was associated with improved prognosis (P = 0.011, P = 0.012 and P = 0.033, respectively). Moreover, co-expression of c-MYC and ß-catenin was significantly correlated with longer survival by univariate (P = 0.012) and multivariate (P = 0.048) studies. Overexpression of c-MYC protein was associated with mRNA overexpression (ρ, 0.479; P < 0.001) and nuclear ß-catenin expression (ρ, 0.282; P < 0.001). Expression of c-MYC and ß-catenin was heterogeneous depending on location in advanced CRC patients (cohort 2). Nevertheless, both c-MYC and ß-catenin expression in primary cancer were significantly correlated with improved survival in univariate (P = 0.001) and multivariate (P = 0.002) analyses. c-MYC and ß-catenin expression of lymph node or distant metastatic tumor was not significantly correlated with patients’ prognosis (P > 0.05).ConclusionsCo-expression of c-MYC and ß-catenin was independently correlated with favorable prognosis in CRC patient. We concluded that the expression of c-MYC and ß-catenin might be useful predicting indicator of CRC patient’s prognosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2770-7) contains supplementary material, which is available to authorized users.

Abstract P2-04-01: The role of Jmjd1a in mammary gland development and breast tumor growth

Abstract Histone modification alters chromatin architecture and thereby influences gene transcription. Histone methylation status is reversible and counter-regulated by methyltransferases and demethylases. Jmjd1a (also known as KDM3A, TSGA, JMJD1, JHDM2A and JHMD2A) is a histone demethylase. It belongs to JmjC domain-containing protein family and could specifically remove di- and mono- methyl residues from di or mono-methylated histone H3K9 (H3K9me2/me1). Recent studies showed that Jmjd1a plays an important role in embryonic stem cell self-renewal, spermatogenesis, regulation of metabolic gene expression and body weight, sex determination, tumor angiogenesis, and macrophage infiltration. However, its role in mammary gland (MG) development, breast carcinogenesis and breast cancer progression hasn't been systemically investigated. In this study, we found that Jmjd1a is expressed in mouse luminal epithelial cells. Genetic disruption of the Jmjd1a gene significantly slowed down MG development as indicated by retarded MG elongation and decreased ductal density in virgin mice observed at the ages of 4, 6 and 8 weeks. In agreement with the retarded MG development, the expression of Ki67 and cyclinD1 in epithelial cells of MGs from Jmjd1a knockout (KO) mice dramatically reduced compared with that from wild type (WT) mice. H3K9me1 and H3K9me2 levels in the epithelial cells of KO MGs are much higher than that in WT MGs. To assess the role of Jmjd1a in breast cancer progression, we crossbred Tg(Jmjd1a-/-) mice with MMTV-TVA(RCAS-PyMT) mice and obtained Tg(Jmjd1a-/-)×MMTV-TVA(RCAS-PyMT) mice. Infection of the TVA-expressing MG epithelial cells with the RCAS-PyMT virus induced mammary tumors in these mice and MMTV-TVA(RCAS-PyMT) control mice. We found that KO of Jmjd1a slightly accelerated mammary tumor initiation but significantly decreased tumor growth. Ki67 and cyclinD1 expression statistically reduced in KO tumors versus WT tumors. At the molecular level, Jmjd1a expression positively correlated with cyclin D1 expression in mammary epithelial cells and mammary tumors. Knockdown of Jmjd1a in MCF-7 cells significantly reduced cyclin D1 expression, while ectopic expression of Jmjd1a in MCF-7 cells increased cyclin D1 expression. ChIP assay revealed that Jmjd1a is associated with a promoter region of cyclin D1. Co-expression of c-Myc and Jmjd1a boosted the activity of the cyclin D1 reporter. In conclusion, our study indicated that Jmjd1a plays an important role in promoting mammary gland development and breast tumor growth by up-regulating cyclin D1 expression. Targeting Jmjd1a may inhibit breast cancer progression. Citation Format: Qin L, Xu Y, Wu Y, Yu X, Toneff MJ, Liao L, Li Y, Xu J. The role of Jmjd1a in mammary gland development and breast tumor growth. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-04-01.

Expression of c-myc in anaplastic large cell lymphoma and its significance

Objective To investigate the protein expression and genetic alterations of c-myc in primary systemic anaplastic large cell lymphoma(ALCL)and discuss its relationship with clinicopathologic features and immunophenotypes. Methods 87 cases of ALCL were selected. Immunohistochemical method was used to detect the protein expression of c-myc, ALK, CD3, CD10, CD20, CD30 and EMA. c-myc and ALK genetic alterations were detected by using fluorescence in situ hybridization(FlSH). The interrelationships between protein expression, genetic alterations and clinicopathological parameters were analysed statistically. Results Immunohistochemical results: of 87 cases, ALK protein was expressed in 54 cases(62.1 %). c-myc protein was expressed in 27 cases(31.0 %). ALK and c-myc were co-expressed in 20 cases(23.0 %). c-myc protein expression, ALK and c-myc co-expression increased with the upgrade of ALCL clinical stages, and the expression was higher in International Prognostic Index(IPI)high-risk groups than in low-risk groups(P 0.05), while they were statistically significant in c-myc groups(P < 0.05)and in different IPI groups(P < 0.05). Conclusion c-myc protein expression and aneuploidy were related with ALCL clinical stages and IPI, which could be used as an indicator of estimating ALCL malignant degree and predicting prognosis. Key words: Anaplastic large cell lymphoma; c-myc; Immunohistochemistry; Fluorescence in situ hybridization

Minimal cooperation between mutant Hras and c‐myc or TGFα in the regulation of mouse hepatocyte growth or transformation in vivo

Liver carcinogenesis is associated with multiple genetic changes in affected cells, including alterations in the Hras signalling pathway. To define the biological contributions of Hras to mouse hepatocarcinogenesis, we quantified in vivo interactions between mutant Hras and other genetic alterations frequently associated with liver cancer, including overexpression of the transcription factor c-myc and the epidermal growth factor receptor ligand transforming growth factor alpha (TGFα). To accomplish this aim, we initiated expression of an activated Hras in hepatocytes of adult mice with or without simultaneous overexpression of either c-myc or TGFα. Potential interactions also were assessed through the use of the comparative hepatocyte growth assay, a hepatocyte transplantation assay that measures effects of altered gene expression on hepatocyte growth in vivo. Hras expression caused diffuse liver enlargement (hepatomegaly), and this phenotype was not changed by coexpression of c-myc or TGFα. Using the transplant system, we found that expression of mutant Hras alone was sufficient to induce hepatocyte focus growth in a quiescent liver. Paradoxically, adding expression of TGFα or c-myc reversed this Hras effect. Finally, the frequencies of transplant foci with the preneoplastic feature of extreme growth potential and of liver neoplasms were increased for Hras and both combinations when compared with control hepatocytes, but did not differ among oncogene-expressing groups. Hras-associated hepatocyte growth deregulation is not complemented by activation of c-myc or TGFα growth signalling pathways in mouse liver. This finding emphasizes the tissue-specific character of molecular growth regulation.

Genomic modeling of tumor onset and progression in a mouse model of aggressive human liver cancer

A comprehensive understanding of molecular mechanisms driving cancer onset and progression should provide a basis for improving early diagnosis, biomarker discovery and treatment options. A key value of genetically engineered mice for modeling human cancer is the possibility to analyze the entire process of tumor development. Here, we applied functional genomics approach to study step-by-step development of hepatocellular carcinoma (HCC) in the c-Myc/Tgfα transgenic mouse model of aggressive human liver cancer. We report that coexpression of c-Myc and Tgfα induces progressive and cumulative transcriptional alterations in the course of liver oncogenesis. Functional analysis of deregulated genes at the early stage of HCC disease supports a model of active hepatocyte proliferation on the background of chronic oxidative stress generated by a general metabolic disorder. In addition, early and persistent deregulation of numerous immune-related genes suggested that disruption of immune microenvironment may contribute to oncogenic process in this model of accelerated liver carcinogenesis. In particularly, by flow cytometry analysis, we found loss of the major histocompatibility complex class I expression in dysplastic hepatocytes followed by upregulation of numerous activating ligands for natural killer (NK) cells concomitant with a drastic decrease in hepatic NK cell frequency. In conclusion, our study provides a comprehensive characterization of sequential molecular changes during a stepwise progression of preneoplastic lesions toward HCC and highlights a critical role of metabolic disorders and innate immunity at the early stages of liver cancer.

Pim1 kinase synergizes with c-MYC to induce advanced prostate carcinoma

The oncogenic PIM1 kinase has been implicated as a cofactor for c-MYC in prostate carcinogenesis. Here we show that in human prostate tumors, coexpression of c-MYC and PIM1 is associated with higher Gleason grades. Using a tissue recombination model coupled with lentiviral-mediated gene transfer we find that Pim1 is weakly oncogenic in naïve adult mouse prostatic epithelium. However, it cooperates dramatically with c-MYC to induce prostate cancer within 6-weeks. Importantly, c-MYC/Pim1 synergy is critically dependent on Pim1 kinase activity. c-MYC/Pim1 tumors showed increased levels of the active serine-62 (S62) phosphorylated form of c-MYC. Grafts expressing a phosphomimetic c-MYCS62D mutant had higher rates of proliferation than grafts expressing wild type c-MYC but did not form tumors like c-MYC/Pim1 grafts, indicating that Pim1 cooperativity with c-MYC in vivo involves additional mechanisms other than enhancement of c-MYC activity by S62 phosphorylation. c-MYC/Pim1-induced prostate carcinomas demonstrate evidence of neuroendocrine (NE) differentiation. Additional studies, including the identification of tumor cells coexpressing androgen receptor and NE cell markers synaptophysin and Ascl1 suggested that NE tumors arose from adenocarcinoma cells through transdifferentiation. These results directly demonstrate functional cooperativity between c-MYC and PIM1 in prostate tumorigenesis in vivo and support efforts for targeting PIM1 in prostate cancer.

Regulation of Cell Proliferation and Apoptosis in CHO-K1 Cells by the Coexpression of c-Myc and Bcl-2

Proliferation and cell death are regarded as key targets for the optimization of animal cell culture processes and for the maximization of product yield. Although chemical and physical factors are vitally important, of primary interest is the utilization of genetic engineering to regulate cellular processes. CHO cells were first genetically modified to enhance proliferation rate in both suspension and monolayer cultures. Under the constitutive control of c-myc overexpression the CHO cultures showed an increase in growth rate and maximum cell number accompanied by a similar decrease in specific glucose consumption rate. Although the c-myc transfected cell line exhibited apoptosis at much lower rates than is widely reported and associated with the overexpression of c-Myc, it was nevertheless apparent that c-Myc was responsible for the induction of higher apoptotic rates when compared with the control cell line. Hence, the anti-apoptotic gene bcl-2 was also used to transfect the c-Myc CHO cell line, to reduce cell death. Overexpression of both oncoproteins resulted in a cell line that exhibited higher proliferation rates and maximum cell numbers, with a decrease in apoptosis when compared to the parental cell line. In conclusion, it was shown that Bcl-2 protein overexpression specifically abrogates c-Myc-induced apoptosis without affecting the c-Myc mitogenic function.

Nucleophosmin suppresses oncogene-induced apoptosis and senescence and enhances oncogenic cooperation in cells with genomic instability

Cells from patients with genomic instability syndromes have high predisposition to cancer. However, little is known about whether these mutant cells have high susceptibility to oncogenic transformation. We have tested the hypothesis that a defect in maintaining genome integrity is necessary but not sufficient alone for oncogenic transformation and needs to collaborate with other signals in order to produce full oncogenic transformation. Using genetically matched primary cells deficient for the Fanconi complementation group C gene (Fancc) and the ataxia telangiectasia mutated gene (Atm), we found that certain forms of oncogenic activation and cooperation require a combination of genomic instability with increased expression of nucleophosmin (NPM) to prevent oncogenic stress-induced apoptosis or senescence. Intriguingly, co-expression of c-Myc and NPM leads to a synergistic increase in the proliferation rate in Fancc-/- or Atm-/- cells. Analysis of p53 stabilization and activation by c-Myc demonstrates that over-expression of NPM significantly reduces the accumulation of the activated p53 but not the stability of p53. Moreover, NPM is shown to enhance transforming activity of co-expressed Myc and Ras in wild-type and, to a greater degree, in Fancc-/- or Atm-/- cells, suggesting a role in oncogenic cooperation. Finally, a partial knockdown of NPM is sufficient to cause massive apoptosis in Fancc-/- or Atm-/- cells co-expressing c-Myc and Ras while sparing untransformed cells. Our study demonstrates a novel mechanism of NPM tumorigenesis by establishing NPM as a crucial inhibitor of oncogene-induced apoptosis and senescence.

Bcl-6 and c-Myc are rarely co-expressed in adult diffuse large B-cell lymphoma

Bcl-6 is expressed in germinal centre derived B-cell non-Hodgkin lymphomas including diffuse large B-cell lymphoma (DLBCL) and is likely to play a major role in driving proliferation of a subset of DLBCLs, especially those of germinal centre B-cell subtype, but the role of c-Myc, which is important for proliferation in various lineages is not known. We used the highly standardised staining conditions of a tissue microarray to characterise co-expression of c-Myc and Bcl-6 in DLBCL. We carried out immunohistochemistry of 73 arrayed cases. The majority (62/73) did not express c-Myc, but 11 cases (15%) showed nuclear staining. 5/53 (9%) of Bcl-6 expressing cases co-expressed c-Myc, whereas a much higher proportion, 6/20 (30%), of Bcl-6 negative cases were positive for c-Myc. Overall survival of c-Myc expressing cases was the same as those that had absent expression. There was no significant correlation between c-Myc expression and DLBCL subtype (germinal centre or non-germinal centre subtypes).

An Essential Role of Alternative Splicing of c-myc Suppressor FUSE-Binding Protein–Interacting Repressor in Carcinogenesis

Elevated expression of c-myc has been detected in a broad range of human cancers, indicating a key role for this oncogene in tumor development. Recently, an interaction between FUSE-binding protein-interacting repressor (FIR) and TFIIH/p89/XPB helicase was found to repress c-myc transcription and might be important for suppressing tumor formation. In this study, we showed that enforced expression of FIR induced apoptosis. Deletion of the NH(2)-terminal repression domain of FIR rescued the cells from apoptosis as did coexpression of c-Myc with FIR; thus, repression of Myc mediates FIR-driven apoptosis. Surprisingly, a splicing variant of FIR unable to repress c-myc or to drive apoptosis was frequently discovered in human primary colorectal cancers but not in the adjacent normal tissues. Coexpression of this splicing variant with repressor-competent FIR, either in HeLa cells or in the colon cancer cell line SW480, not only abrogated c-Myc suppression but also inhibited apoptosis. These results strongly suggest the expression of this splicing variant promotes tumor development by disabling FIR repression and sustaining high levels of c-Myc and opposing apoptosis in colorectal cancer.