Expression signature of human endogenous retroviruses in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is one of the most diagnosed forms of leukemia worldwide and it is usually classified into two forms: indolent and aggressive. These two forms are characterized by distinct molecular features that drive different responses to treatment and clinical outcomes. In this context, a better understanding of the molecular landscape of the CLL forms may potentially lead to the development of new drugs or the identification of novel biomarkers. Human endogenous retroviruses (HERVs) are a class of transposable elements that have been associated with the development of different human cancers, including different forms of leukemias. However, no studies about HERVs in CLL have ever been reported so far. Here, we present the first locus-specific profiling of HERV expression in both the aggressive and indolent forms of CLL. Our analyses revealed several dysregulations in HERV expression occurring in CLL and some of them were specific for either the aggressive or indolent form of CLL. Such results were also validated by analyzing an external cohort of CLL patients and by RT-qPCR. Moreover, in silico analyses have shown relevant signaling pathways associated with them suggesting a potential involvement of the dysregulated HERVs in these pathways and consequently in CLL development.

tRNA-derived fragments (tRFs) in cancer

tRNA fragments (tRNA derived fragments or tRFs) are small single stranded RNA molecules derived from pre-tRNAs and mature tRNAs. tRFs have been known for a number of years, but previously they were believed to be not important products of tRNA degradation. tRFs can be unique, like tRF-1 s, or redundant, like tRF-3 s and tRF-5 s. Scientific interest in tRFs has drastically increased in the last 5 years. Many studies have found that tRFs are differentially expressed in many normal cellular processes as well as in transformed cancer cells. Dysregulation of tRFs expression have been reported in multiple major types of cancer including solid cancers and lymphoid malignancies. However the exact molecular role of these molecules is not entirely clear. A number of studies proposed that tRFs can work as microRNAs by targeting gene expression. Here we discuss recent studies showing differential expression of tRFs in many cancers as well as what is currently known about tRFs biological functions in cancer cells.

Identification of tRNA-derived small RNA (tsRNA) responsive to the tumor suppressor, RUNX1, in breast cancer

Despite recent advances in targeted therapies, the molecular mechanisms driving breast cancer initiation, progression, and metastasis are minimally understood. Growing evidence indicate that transfer RNA (tRNA)-derived small RNAs (tsRNA) contribute to biological control and aberrations associated with cancer development and progression. The runt-related transcription factor 1 (RUNX1) transcription factor is a tumor suppressor in the mammary epithelium whereas RUNX1 downregulation is functionally associated with breast cancer initiation and progression. We identified four tsRNA (ts-19, ts-29, ts-46, and ts-112) that are selectively responsive to expression of the RUNX1 tumor suppressor. Our finding that ts-112 and RUNX1 anticorrelate in normal-like mammary epithelial and breast cancer lines is consistent with tumor-related activity of ts-112 and tumor suppressor activity of RUNX1. Inhibition of ts-112 in MCF10CA1a aggressive breast cancer cells significantly reduced proliferation. Ectopic expression of a ts-112 mimic in normal-like mammary epithelial MCF10A cells significantly increased proliferation. These findings support an oncogenic potential for ts-112. Moreover, RUNX1 may repress ts-112 to prevent overactive proliferation in breast epithelial cells to augment its established roles in maintaining the mammary epithelium.

Genetic dynamics in untreated CLL patients with either stable or progressive disease: a longitudinal study

Clonal evolution of chronic lymphocytic leukemia (CLL) often follows chemotherapy and is associated with adverse outcome, but also occurs in untreated patients, in which case its predictive role is debated. We investigated whether the selection and expansion of CLL clone(s) precede an aggressive disease shift. We found that clonal evolution occurs in all CLL patients, irrespective of the clinical outcome, but is faster during disease progression. In particular, changes in the frequency of nucleotide variants (NVs) in specific CLL-related genes may represent an indicator of poor clinical outcome.

MicroRNA dysregulation and multi-targeted therapy for cancer treatment

We established that loss of miR-15a/16-1 genes on chromosome 13q14 is the most common alteration in Chronic Lymphocytic Leukemia (CLL) and that miR-15/16 are crucial negative regulator of BCL-2, an antiapoptotic gene overexpressed in most CLLs and in many other malignancies. We have also shown that miR-15/16 target ROR1, a cell surface receptor for Wnt5a which can enhance growth/survival of CLL cells. Interestingly, ROR1 is expressed by many cancers, but not by normal adult tissues. Moreover, Venetoclax, the anti-Bcl-2 drug, and Cirmtuzumab, the monoclonal antibody against ROR1, are synergistic in killing CLL cells. Since an additional miR-15/16 locus exists on chromosome 3q25 (miR-15b/16-2), we generated a knocked out mouse model to study its the role in cancer. We observed that the KO mice developed predominantly CLL. Thus, we generated a double knock out mouse model where both miR-15/16 loci were deleted. Surprisingly we observed that 77% of double KO mice developed Acute Myeloid Leukemia (AML). Based on these evidences, we anticipate that also AMLs with low miR-15/16 expression, overexpression of BCL2 and expression of ROR1, would show an excellent response to a combination therapy with Venetoclax and Cirmtuzumab, since both drugs target the same malignant cells that have lost miR-15/16.

HNRNPL Restrains miR-155 Targeting of BUB1 to Stabilize Aberrant Karyotypes of Transformed Cells in Chronic Lymphocytic Leukemia

Aneuploidy and overexpression of hsa-miR-155-5p (miR-155) characterize most solid and hematological malignancies. We recently demonstrated that miR-155 sustains aneuploidy at early stages of in vitro cellular transformation. During in vitro transformation of normal human fibroblast, upregulation of miR-155 downregulates spindle checkpoint proteins as the mitotic checkpoint serine/threonine kinase budding uninhibited by benzimidazoles 1 (BUB1), the centromere protein F (CENPF) and the zw10 kinetochore protein (ZW10), compromising the chromosome alignment at the metaphase plate and leading to aneuploidy in daughter cells. Here we show that the heterogeneous nuclear ribonucleoprotein L (HNRNPL) binds to the polymorphic marker D2S1888 at the 3′UTR of BUB1 gene, impairs the miR-155 targeting, and restores BUB1 expression in chronic lymphocytic leukemia. This mechanism occurs at advanced passages of cell transformation and allows the expansion of more favorable clones. Our findings have revealed, at least in part, the molecular mechanisms behind the chromosomal stabilization of cell lines and the concept that, to survive, tumor cells cannot continuously change their genetic heritage but need to stabilize the most suitable karyotype.

Identification of tRNA-derived ncRNAs in TCGA and NCI-60 panel cell lines and development of the public database tRFexplorer

Next-generation sequencing is increasing our understanding and knowledge of non-coding RNAs (ncRNAs), elucidating their roles in molecular mechanisms and processes such as cell growth and development. Within such a class, tRNA-derived ncRNAs have been recently associated with gene expression regulation in cancer progression. In this paper, we characterize, for the first time, tRNA-derived ncRNAs in NCI-60. Furthermore, we assess their expression profile in The Cancer Genome Atlas (TCGA). Our comprehensive analysis allowed us to report 322 distinct tRNA-derived ncRNAs in NCI-60, categorized in tRNA-derived fragments (11 tRF-5s, 55 tRF-3s), tRNA-derived small RNAs (107 tsRNAs) and tRNA 5' leader RNAs (149 sequences identified). In TCGA, we were able to identify 232 distinct tRNA-derived ncRNAs categorized in 53 tRF-5s, 58 tRF-3s, 63 tsRNAs and 58 5' leader RNAs. This latter group represents an additional evidence of tRNA-derived ncRNAs originating from the 5' leader region of precursor tRNA. We developed a public database, tRFexplorer, which provides users with the expression profile of each tRNA-derived ncRNAs in every cell line in NCI-60 as well as for each TCGA tumor type. Moreover, the system allows us to perform differential expression analyses of such fragments in TCGA, as well as correlation analyses of tRNA-derived ncRNAs expression in TCGA and NCI-60 with gene and miRNA expression in TCGA samples, in association with all omics and compound activities data available on CellMiner. Hence, the tool provides an important opportunity to investigate their potential biological roles in absence of any direct experimental evidence. Database URL: https://trfexplorer.cloud/.

MicroRNA Profiling of Salivary Duct Carcinoma Versus Her2/Neu Overexpressing Breast Carcinoma Identify miR-10a as a Putative Breast Related Oncogene

Salivary duct carcinomas (SDC) and Her2/Neu3-overexpressing invasive breast carcinomas (HNPIBC/IBC) are histologically indistinguishable. We investigated whether common histopathologic and immunophenotypic features of SDC and IBC are mirrored by a similar microRNA (miRNA) profile. MiRNA profiling of 5 SDCs, 6 IBCs Her2/Neu3+, and 5 high-grade ductal breast carcinoma in situ (DCIS) was performed by NanoString platform. Selected miRNAs and HOXA1 gene were validated by RT-PCR. We observed similar miRNA expression profiles between IBC and SDC with the exception of 2 miRNAs, miR-10a and miR-142-3p, which were higher in IBC tumors. DCIS tumors displayed increased expression of miR-10a, miR-99a, miR-331-3p and miR-335, and decreased expression of miR-15a, miR-16 and miR-19b compared to SDC. The normal salivary gland and breast tissues also showed similar expression profiles. Interestingly, miR-10a was selectively increased in both IBC and normal breast tissue compared to SDC and normal salivary gland tissue. Moreover, our NanoString and RT-PCR data confirmed that miR-10a was upregulated in IBC and DCIS compared to SDC. Finally, we show downregulation of HOXA1, a miR-10 target, in IBC tumors compared to normal breast tissue. Taken together, our data demonstrates that, based on miRNA profiling, SDC is closely related to HNPIBC. Our results also suggest that miR-10a is differentially expressed in IBC compared to SDC and may have potential utility as a diagnostic biomarker in synchronous or metachronous malignant epithelial malignancies involving both organs. In addition, miR-10a could be playing an important role as a mammary-specific oncogene, involved in breast cancer initiation (DCIS) and progression (IBC), through mechanisms that include modulation of HOXA1 gene expression.

BCL2 and miR-15/16: from gene discovery to treatment

In 1984, we investigated the t(14;18) chromosomal translocations that frequently occur in patients with follicular lymphoma. We first identified a locus on chromosome 18 involved in these translocations with the chromosome 14 containing the immunoglobulin heavy chain locus. Within this region on chromosome 18, we then discovered a gene that we called BCL2, which was activated by the translocations. Since that time, many studies determined that BCL2 is one of the most important oncogenes involved in cancer by inhibiting apoptosis. In 2002, we studied 13q deletions in chronic lymphocytic leukemia (CLL) and found that the microRNA cluster miR-15a/miR-16-1 (miR-15/16) is deleted by 13q deletions. In 2005, we discovered that miR-15/16 function as tumor suppressors by directly targeting BCL2. Thus the loss of two negative regulators of BCL2 expression results in overexpression of BCL2. Very recently, a specific BCL2 inhibitor ABT-199 (Venetoclax) was developed and approved by FDA for CLL treatment. Thus it took 32 years from fundamental discovery of a critical oncogene to the development of a drug capable to cure CLL. In this review, we discuss the discovery, functions and clinical relevance of miR-15/16 and BCL2.

Role of the tRNA-Derived Small RNAs in Cancer: New Potential Biomarkers and Target for Therapy

Noncoding RNAs are untranslated RNA molecules that can be divided into two main types: infrastructural, including transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), and regulatory, including long ncRNAs (lncRNAs) and small ncRNAs (sRNA). Among small ncRNA, the role of microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs) in cancer is well documented. Recently, other small ncRNAs have been described. In particular, tRNA-derived small RNAs (tsRNA) have been found to be frequently dysregulated in cancer. Since tsRNAs can be considered unique sequences and are able to bind both Argonaute proteins (like miRNAs) and Piwi proteins (like piRNAs), their dysregulation could play a critical role in cancer by interfering with gene expression regulation at different levels. Like microRNAs, ts-53 (previously known as miR-3676) interacts with the 3'UTR of TCL1, therefore supporting a role for tsRNAs on the posttranscriptional regulation of gene expression. Like piRNAs, tsRNAs are produced as single-stranded molecules and can interact with DNA and histone methylation machinery, suggesting a role in the pretranscriptional regulation of gene expression. Herein, we describe the most recent findings about the role of tsRNAs in cancer.

Novel mechanisms of regulation of miRNAs in CLL

B-cell chronic lymphocytic leukemia (CLL) is the most common adult human leukemia. Although, the molecular alterations leading to CLL onset and progression are still under investigation (specifically, the interplay and exact role of oncogenes and tumor suppressors in CLL pathogenesis). MicroRNAs are small non-coding RNAs that regulate gene expression and are expressed in a tissue specific manner. Deregulation of microRNAs can alter expression levels of genes involved in the development and/or progression of tumors. In CLL, microRNAs can function as oncogenes or tumor suppressors. Here, we review the most recent findings on the role of microRNAs in the onset/progression of CLL, and how this knowledge can be used to identify new biomarkers and targets to treat this leukemia.

Role of microRNA in chronic lymphocytic leukemia onset and progression

B-cell chronic lymphocytic leukemia (CLL) is the most common human leukemia occurring as indolent or aggressive form. CLL clinical features and genetic abnormalities are well documented, but molecular details are still under investigation. MicroRNAs are small non-coding RNAs involved in several cellular processes and expressed in a tissue-specific manner. MicroRNAs regulate gene expression, and their deregulation can alter expression levels of genes involved in development/progression of tumors. In CLL, microRNAs can function as oncogenes or tumor suppressors and can also serve as markers for CLL onset/progression. Here, we discuss the most recent findings about the role of microRNAs in CLL and how this knowledge can be used to identify new biomarkers and treatment approaches.

A Sleeping Beauty screen reveals NF-kB activation in CLL mouse model

TCL1 oncogene is overexpressed in aggressive form of human chronic lymphocytic leukemia (CLL) and its dysregulation in mouse B cells causes a CD5-positive leukemia similar to the aggressive form of human CLLs. To identify oncogenes that cooperate with Tcl1, we performed genetic screen in Eμ-TCL1 mice using Sleeping Beauty transposon-mediated mutagenesis. Analysis of transposon common insertion sites identified 7 genes activated by transposon insertions. Overexpression of these genes in mouse CLL was confirmed by real time reverse transcription-polymerase chain reaction. Interestingly, the main known function of 4 of 7 genes (Nfkb1, Tab2, Map3K14, and Nfkbid) is participation in or activation of the nuclear factor-kB (NF-kB) pathway. In addition, activation of the NF-kB is 1 of main functions of Akt2, also identified in the screen. These findings demonstrate cooperation of Tcl1 and the NF-kB pathway in the pathogenesis of aggressive CLL. Identification cooperating cancer genes will result in the development of combinatorial therapies to treat CLL.

In vivo NCL targeting affects breast cancer aggressiveness through miRNA regulation

Numerous studies have described the altered expression and the causal role of microRNAs (miRNAs) in human cancer. However, to date, efforts to modulate miRNA levels for therapeutic purposes have been challenging to implement. Here we find that nucleolin (NCL), a major nucleolar protein, posttranscriptionally regulates the expression of a specific subset of miRNAs, including miR-21, miR-221, miR-222, and miR-103, that are causally involved in breast cancer initiation, progression, and drug resistance. We also show that NCL is commonly overexpressed in human breast tumors and that its expression correlates with that of NCL-dependent miRNAs. Finally, inhibition of NCL using guanosine-rich aptamers reduces the levels of NCL-dependent miRNAs and their target genes, thus reducing breast cancer cell aggressiveness both in vitro and in vivo. These findings illuminate a path to novel therapeutic approaches based on NCL-targeting aptamers for the modulation of miRNA expression in the treatment of breast cancer.

Abstract 1122: In vivo NCL-targeting affects breast cancer aggressiveness through miRNA regulation

MicroRNAs (miRNAs) are noncoding single-stranded RNA molecules of ∼22 nucleotides in length. They have a critical role in regulating gene expression by targeting messenger RNAs (mRNAs) in a sequence-specific manner. Active mature miRNAs are produced from primary miRNA transcripts (pri-miRNAs) through sequential cleavages by the microprocessor complex, which includes DROSHA, DGCR8, and DICER proteins. Several miRNAs are specifically up-regulated in various types of tumors, and a wide range of studies have demonstrated how their down-regulation could potentially affect tumorigenesis, metastasis formation and drug resistance. However, most of these studies have indicated the possibility of modulating miRNA expression at the transcriptional level, while only a few focused on post-transcriptional control. Nucleolin (NCL) is a highly conserved multifunctional protein involved in ribosomal RNA (rRNA) biogenesis and in the stabilization of different mRNAs, in the nucleus and in the cytoplasm of normal and cancer cells. NCL was also found on the surface of different types of cancer cells, but not on their normal counterparts, shuttling between the inner and the outer part of the cell membrane. These observations suggested that NCL might be considered a cancer cell specific receptor, able to mediate tumor-selective uptake of specific ligands such as RNA and DNA G-rich aptamers. Here we show that NCL binds the terminal loop and promotes the maturation of a specific set of miRNAs, including miR-21, miR-103, miR-221 and miR-222, whose over-expression is causally associated with greater aggressiveness and resistance to anti-neoplastic therapies of several kind of tumors, such as breast cancer. Accordingly, a direct correlation between the expression levels of NCL and NCL-dependent miRNAs in human breast cancer samples was also observed. Conversely, NCL impairment down-regulated NCL-dependent miRNAs and up-regulates their target in vitro, affecting cancer cell proliferation, migration and anti-neoplastic drug resistance. Finally, we used AS1411, the first NCL-targeting G-rich aptamer that has reached phase II clinical trials for cancer therapy, to inhibit NCL activity in orthotopc xenograft models of breast cancer. Our in vivo data demonstrate that AS1411 down-regulates NCL-dependent miRNAs, hindering breast cancer metastasis. These findings provide insights into the molecular function of NCL in miRNA biology, as well as one of the first realistic strategies for miRNA regulation in cancer therapy.

Citation Format: Dario Palmieri, Luciana De Luca, Jessica Consiglio, Alberto Rocci, Tiffany Talabere, Claudia Piovan, Alessandro Lagana, Luciano Cascione, Jingwen Guan, Pierluigi Gasparini, Veronica Balatti, Vincenzo Coppola, Craig Hofmeister, Guido Marcucci, John Byrd, Stefano Volinia, Charles Shapiro, Michael Freitas, Carlo Croce, Flavia Pichiorri. In vivo NCL-targeting affects breast cancer aggressiveness through miRNA regulation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1122. doi:10.1158/1538-7445.AM2013-1122

miR deregulation in CLL

B-cell chronic lymphocytic leukemia (CLL) is the most frequent human leukemia and it occurs in two forms, indolent and aggressive. Although clinical features and genetic abnormalities in CLL are well documented, molecular details underlying the disease are still under investigation.MicroRNAs are small noncoding RNAs involved in a variety of cellular processes and expressed in a tissue-specific manner. MicroRNAs have the ability to regulate gene expression. In physiological conditions, microRNAs act as gene expression controllers by targeting the mRNA or inhibiting its translation. Their deregulation can lead to an alteration of the expression level of many genes which can induce the development or promote the progression of tumors.In CLL, microRNAs can function as oncogenes, tumor suppressor genes, and/or can be used as markers for disease onset/progression. For example, in indolent CLL, 13q14 deletions targeting miR-15/16 initiate the disease, while in aggressive CLL miR-181 targets the critical TCL1 oncogene and can also be used as a progression marker.Here we discuss the foremost findings about the role of microRNAs in CLL pathogenesis, and how this knowledge can be used to identify new approaches to treat CLL.

Novel insights in molecular mechanisms of CLL

B-cell chronic lymphocytic leukemia (CLL), the most common leukemia, originates from an expansion of a rare population of CD5+CD19+ mature B-cells. CLL occurs in two forms, aggressive and indolent. For the most part aggressive CLL shows high ZAP-70 expression and unmutated IgH V(H), while indolent CLL is characterized by low ZAP-70 expression and mutated IgH V(H). Despite detailed studies of clinical features and chromosomal abnormalities in CLL, molecular details underlying disease development are still not entirely clear. In the past several years, more and more such mechanisms have emerged. Recent studies clarified mechanistic details of how activation of TCL1, a critical molecule in aggressive CLL, initiates this malignancy. In indolent CLL characterized by 13q14 deletions, MiR-15/16 targeting BCL2 and MCL1 and DLEU7 targeting TNF pathway were proposed as tumor suppressors. Analysis of CLL coding genome identified NOTCH1 as a frequent target of activating mutations. Interestingly most of these pathways have downstream activating effects on the NF-kB family transcription factors. Several mouse models of CLL, confirmed importance of these pathways in the pathogenesis of CLL. Here, we discuss what has been learned from these new pathways, and analyze how CLL mouse models confirm newly discovered molecular mechanisms of CLL.

MiR-181b: new perspective to evaluate disease progression in chronic lymphocytic leukemia

Over the past decades numerous markers of the tumor burden have been discovered in chronic lymphocytic leukemia (CLL). Among these, the microRNAs seem to have a promising role. The development and validation of miRNAs as biomarkers should have significant impact in improving early cancer detection and diagnosis, enhancing therapeutic success, and increasing the life expectancy of patients. We identified miR-181b as a biomarker for the progression of this disease from indolent to aggressive. For this study we used sequential samples from patients with either progressive or stable course of the illness. Here, we discuss more extensively this issue by adding novel findings and introducing a novel approach for monitoring CLL patients.

Abstract 2947: B-cell lymphoma in eα-miR-17∼92 transgenic mice

The miR-17∼92 is a polycistronic miRNA cluster, consisting of six miRNAs: miR-17, miR-18a, miR-19a, miR-19b, miR-20a and miR-92a encoded from last exon of a non-coding RNA. It is frequently overexpressed in variety of solid and lymphoid malignancies and has been appropriately called Oncomir-1. Loss-of-function studies revealed a role of miR-17∼92 in heart and lung development, and gain-of-function studies have shown its role in myc induced B-cell lymphomas. In addition to its role in tumorigenesis, the cluster is involved in regulation of lymphocyte development. Some of the key targets of this miRNA include the tumor suppressor, Pten and the proapoptotic, Bim gene. In order to study the mechanisms by which miR-17∼92 overexpression induce tumorigenesis, we generated a B-cell specific transgenic mouse model. The miR-17∼92 overexpression was driven by the eμ enhancer and immunoglobulin heavy chain promoter with a 3′ Green Fluorescent Protein (GFP) tag in order to track the miRNA expression. Expression analysis using Northern Blot and qRT-PCR yielded four founders with significant overexpression of all six miRNAs in their spleens. Quantitative RT-PCR analysis showed significant overexpression of all six miRNAs ranging from 2.5 to 25-fold in spleen cells. Flow cytometry analysis of spleens from 9-month old healthy transgenic mice showed significantly increased CD43+TCR- population as compared to wild type mice. In older mice (18-months) the symptoms are more pronounced with mice developing ascites, enlarged spleen and lymph nodes. The flow analysis of spleens from these mice showed CD19+CD5+ B-cell population similar to human chronic lymphocytic leukemia (CLL). Histological analysis showed multiple organs (lungs, kidney, brain) infiltrated by these lymphoma cells. Southern Blot analysis showed these cells to be oligoclonal B cells, while no T cell clonality was observed. Total mRNA profiling from these malignant cells showed that 782 genes are up- and 1019 genes are down-regulated in transgenic B-cells versus wild type CD19+ B-cells. Ingenuity pathway analysis showed majority of the downregulated genes are represented by Hematological System Development and Function, and Inflammatory Response pathways, while the upregulated genes are represented by cell cycle pathway. Some of the upregulated genes in miR-17∼92 over-expressing malignant B-cells as compared to normal CD19+ B-cells included ZAP-70, CCL5, NONO, previously reported in B-CLL gene signature. Among other overexpressed genes, cJun, cFos and ATF3, were upregulated 5-fold, 67-fold and 18-fold, respectively. We hypothesize that AP-1 dependent transcription may be one of the key survival factors in the miR-17∼92 driven lymphomas. Currently, we are exploring the negative regulators of the oncogenic cJun signaling pathway which may be miR-17∼92 targets. Overall, we found that miR-17∼92 overexpression in mice has the ability to induce B-cell lymphoma which can develop into CLL at an older age.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2947. doi:1538-7445.AM2012-2947

Tcl1 protein functions as an inhibitor of de novo DNA methylation in B-cell chronic lymphocytic leukemia (CLL)

B-cell chronic lymphocytic leukemia (CLL) is the most common human leukemia. Deregulation of the T-cell leukemia/lymphoma 1 oncogene (TCL1) in mouse B cells causes a CD5(+) leukemia similar to aggressive human CLL. To examine the mechanisms by which Tcl1 protein exerts its oncogenic activity in B cells, we performed proteomics experiments to identify its interacting partners. We found that Tcl1 physically interacts with de novo DNA methylthansferases Dnmt3A and Dnmt3B. We further investigated the effects of Tcl1 up-regulation on the enzymatic activity of Dnmt3A and found that Tcl1 overexpression drastically inhibits Dnmt3A function. In addition, B cells from TCL1 transgenic mice showed a significant decrease in DNA methylation compared with WT controls. Similarly, CLL samples with high Tcl1 expression showed a decrease in DNA methylation compared with CLL samples with low Tcl1 expression. Given the previous reports of inactivating mutations of DNMT3A in acute myelogenous leukemia and myelodysplastic syndrome, our results suggest that inhibition of de novo DNA methylation may be a common oncogenic mechanism in leukemogenesis.

Abstract 4051: MiR-181b expression levels decreases during the progression of the Chronic Lymphocytic Leukemia: a new potential prognostic tool

In patients with Chronic Lymphocytic Leukemia (CLL) the prognosis is extremely variable, ranging from a very short to a normal lifespan. Classic clinical stages, based on biologic and clinical parameters, have been the most important factor for assessing prognosis in CLL patients; however, they are not devoid of limitations. Therefore, investigations are ongoing for searching new parameters in an attempt to add prognostic power to clinical stages. In this study we performed a genome-wide microRNA expression profiling to investigate the role of microRNA genes in the progression of CLL and to develop better prognostic indicators of these disease. We compared paired samples from CLL patients having an indolent and stable disease with their progressed aggressive form. We found that miR-181b was consistently down-regulated in the aggressive form of the disease compared to its previous stable counterpart. Further studies on serial time points from the same patient demonstrated that the strong decrease of the miR-181b expression levels occurs before the disease is clearly aggressive Moreover, we observed that the miR-181b expression remain constant over the time in two time points from CLL patients having a stable course; entailing a decreased levels of the miR-181b in the aggressive form of the CLL as a specific effect due to the progression of the disease. Finally in this study we investigate the biological role of the putative prognostic indicator related to the TCL1A, which is a critical gene in the pathogenesis of the CLL. In conclusion our data hint a prognostic role of the miR-181b in CLL.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4051.

Simian virus 40 in humans

Simian virus 40 (SV40) is a monkey virus that was administered to human populations by contaminated vaccines which were produced in SV40 naturally infected monkey cells. Recent molecular biology and epidemiological studies suggest that SV40 may be contagiously transmitted in humans by horizontal infection, independently from the earlier administration of SV40-contaminated vaccines.SV40 footprints in humans have been found associated at high prevalence with specific tumor types such as brain and bone tumors, mesotheliomas and lymphomas and with kidney diseases, and at lower prevalence in blood samples from healthy donors. Contrasting reports appeared in the literature on the circulation of SV40 in humans by contagious transmission and its association, as a possible etiologic cofactor, with specific human tumors. As a consequence of the conflicting results, a considerable debate has developed in the scientific community. In the present review we consider the main results obtained by different groups investigating SV40 sequences in human tumors and in blood specimens, the putative role of SV40 in the onset/progression of specific human tumors, and comment on the hypotheses arising from these data.