miRNA-mediated TUSC3 deficiency enhances UPR and ERAD to promote metastatic potential of NSCLC

Non-small cell lung carcinoma (NSCLC) is leading cause of cancer-related deaths in the world. The Tumor Suppressor Candidate 3 (TUSC3) at chromosome 8p22 known to be frequently deleted in cancer is often found to be deleted in advanced stage of solid tumors. However, the role of TUSC3 still remains controversial in lung cancer and context-dependent in several cancers. Here we propose that miR-224/-520c-dependent TUSC3 deficiency enhances the metastatic potential of NSCLC through the alteration of three unfolded protein response pathways and HRD1-dependent ERAD. ATF6α-dependent UPR is enhanced whereas the affinity of HRD1 to its substrates, PERK, IRE1α and p53 is weakened. Consequently, the alteration of UPRs and the suppressed p53-NM23H1/2 pathway by TUSC3 deficiency is ultimately responsible for enhancing metastatic potential of lung cancer. These findings provide mechanistic insight of unrecognized roles of TUSC3 in cancer progression and the oncogenic role of HRD1-dependent ERAD in cancer metastasis.

The TLR7/8/9 Antagonist IMO-8503 Inhibits Cancer-Induced Cachexia

: Muscle wasting is a feature of the cachexia syndrome, which contributes significantly to the mortality of patients with cancer. We have previously demonstrated that miR-21 is secreted through extracellular vesicles (EV) by lung and pancreatic cancer cells and promotes JNK-dependent cell death through its binding to the TLR7 receptor in murine myoblasts. Here, we evaluate the ability of IMO-8503, a TLR7, 8, and 9 antagonist, to inhibit cancer-induced cachexia. Using EVs isolated from lung and pancreatic cancer cells and from patient plasma samples, we demonstrate that IMO-8503 inhibits cell death induced by circulating miRNAs with no significant toxicity. Intraperitoneal administration of the antagonist in a murine model for Lewis lung carcinoma (LLC-induced cachexia) strongly impaired several cachexia-related features, such as the expression of Pax7 as well as caspase-3 and PARP cleavage in skeletal muscles, and significantly prevented the loss of lean mass in tumor-bearing mice. IMO-8503 also impaired circulating miRNA-induced cell death in human primary myoblasts. Taken together, our findings strongly indicate that IMO-8503 serves as a potential therapy for the treatment of cancer cachexia. SIGNIFICANCE: Cancer-associated cachexia is a significant problem for patients with cancer that remain poorly understood, understudied, and inadequately treated; these findings report a potential new therapeutic for the treatment of TLR7-mediated cancer cachexia.

Circulating Micrornas Predict Survival of Patients with Tumors of Glial Origin

The World Health Organization has recently introduced molecular prognostic-diagnostic biomarkers in the classification of Central Nervous System (CNS) tumors. In order to characterize subclasses of tumors that cannot find a precise location in the current classification, and, or cannot be tested because of scant material, it is important to find new molecular biomarkers in tissue and, or biological fluid samples. In this study, we identified serum microRNAs that could serve as biomarkers for the diagnosis and prognosis of patients with tumors of glial origin. We retrospectively analyzed microRNA expression in the serum extracellular vesicles of patients with tumors of glial origin. Extracellular vesicles RNA was analyzed by Nanostring. qRT-PCR confirmed 6 overexpressed microRNAs: hsa-miR-4443, hsa-miR-422a, hsa-miR-494-3p, hsa-miR-502-5p, hsa-miR-520f-3p, and hsa-miR-549a. Hsa-miR-4443 was the only microRNA that showed significant differences in most comparisons. In situ hybridization (ISH), confirmed that our signature was mostly expressed in cancer cells. Importantly, hsa-miR-549a and hsa-miR-502-5p expression predicted prognosis in patients with tumors of glial origin. Although more studies are needed, we demonstrated that serum vesicles microRNA profiles are promising diagnostic and prognostic molecular biomarkers that will find an actual application in the clinical practice of CNS tumors.

A Fhit-mimetic peptide suppresses annexin A4-mediated chemoresistance to paclitaxel in lung cancer cells

We recently reported that Fhit is in a molecular complex with annexin A4 (ANXA4); following to their binding, Fhit delocalizes ANXA4 from plasma membrane to cytosol in paclitaxel-resistant lung cancer cells, thus restoring their chemosensitivity to the drug. Here, we demonstrate that Fhit physically interacts with A4 through its N-terminus; molecular dynamics simulations were performed on a 3D Fhit model to rationalize its mechanism of action. This approach allowed for the identification of the QHLIKPS heptapeptide (position 7 to 13 of the wild-type Fhit protein) as the smallest Fhit sequence still able to preserve its ability to bind ANXA4. Interestingly, Fhit peptide also recapitulates the property of the native protein in inhibiting Annexin A4 translocation from cytosol to plasma membrane in A549 and Calu-2 lung cancer cells treated with paclitaxel. Finally, the combination of Tat-Fhit peptide and paclitaxel synergistically increases the apoptotic rate of cultured lung cancer cells and blocks in vivo tumor formation.

Our findings address to the identification of chemically simplified Fhit derivatives that mimic Fhit tumor suppressor functions; intriguingly, this approach might lead to the generation of novel anticancer drugs to be used in combination with conventional therapies in Fhit-negative tumors to prevent or delay chemoresistance.

miR-130a Deregulates PTEN and Stimulates Tumor Growth

H-RasV12 oncogene has been shown to promote autophagic cell death. Here, we provide evidence of a contextual role for H-RasV12 in cell death that is varied by its effects on miR-130a. In E1A-immortalized murine embryo fibroblasts, acute expression of H-RasV12 promoted apoptosis, but not autophagic cell death. miRNA screens in this system showed that miR-130a was strongly downregulated by H-RasV12 in this model system. Enforced expression of miR-130a increased cell proliferation in part via repression of PTEN. Consistent with this effect, miR-130a overexpression in human breast cancer cells promoted Akt phosphorylation, cell survival, and tumor growth. In clinical specimens of multiple human cancers, expression of miR-130 family members correlated inversely with PTEN expression. Overall, our results defined miR-130a as an oncogenic miRNA that targets PTEN to drive malignant cell survival and tumor growth. Cancer Res; 77(22); 6168-78. ©2017 AACR.

A novel fully human anti-NCL immunoRNase for triple-negative breast cancer therapy

Breast cancer is the most common cancer in women worldwide. A new promising anti-cancer therapy involves the use of monoclonal antibodies specific for target tumor-associated antigens (TAAs). A TAA of interest for immunotherapy of Triple Negative Breast Cancer (TNBC) is nucleolin (NCL), a multifunctional protein, selectively expressed on the surface of cancer cells, which regulates the biogenesis of specific microRNAs (miRNAs) involved in tumor development and drug-resistance. We previously isolated a novel human anti-NCL scFv, called 4LB5, that is endowed with selective anti-tumor effects. Here we report the construction and characterization of a novel immunoRNase constituted by 4LB5 and a human pancreatic RNase (HP-RNase) called "4LB5-HP-RNase". This immunoRNase retains both the enzymatic activity of human pancreatic RNase and the specific binding of the parental scFv to a panel of surface NCL-positive breast cancer cells. Notably, 4LB5-HP-RNase dramatically and selectively reduced the viability and proliferation of NCL-positive tumor cells in vitro and in vivo. Specifically, it induced apoptosis and reduced the levels of the tumorigenic miRNAs miR-21, -221 and -222. Thus, this novel immunoagent could be a valuable tool for the treatment of TNBC patients ineligible for currently available targeted treatments.

ERK Activation Globally Downregulates miRNAs through Phosphorylating Exportin-5

MicroRNAs (miRNA) are mostly downregulated in cancer. However, the mechanism underlying this phenomenon and the precise consequence in tumorigenesis remain obscure. Here we show that ERK suppresses pre-miRNA export from the nucleus through phosphorylation of exportin-5 (XPO5) at T345/S416/S497. After phosphorylation by ERK, conformation of XPO5 is altered by prolyl isomerase Pin1, resulting in reduction of pre-miRNA loading. In liver cancer, the ERK-mediated XPO5 suppression reduces miR-122, increases microtubule dynamics, and results in tumor development and drug resistance. Analysis of clinical specimens further showed that XPO5 phosphorylation is associated with poor prognosis for liver cancer patients. Our study reveals a function of ERK in miRNA biogenesis and suggests that modulation of miRNA export has potential clinical implications.

HDAC inhibitor AR-42 decreases CD44 expression and sensitizes myeloma cells to lenalidomide

Multiple myeloma (MM) is a hematological malignancy of plasma cells in the bone marrow. Despite multiple treatment options, MM is inevitably associated with drug resistance and poor outcomes. Histone deacetylase inhibitors (HDACi's) are promising novel chemotherapeutics undergoing evaluation in clinical trials for the potential treatment of patients with MM. Although in preclinical studies HDACi's have proven anti-myeloma activity, but in the clinic single-agent HDACi treatments have been limited due to low tolerability. Improved clinical outcomes were reported only when HDACi's were combined with other drugs. Here, we show that a novel pan-HDACi AR-42 downregulates CD44, a glycoprotein that has been associated with lenalidomide and dexamethasone resistance in myeloma both in vitro and in vivo. We also show that this CD44 downregulation is in part mediated by miR-9–5p, targeting insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3), which directly binds to CD44 mRNA and increases its stability. Importantly, we also demonstrate that AR-42 enhances anti-myeloma activity of lenalidomide in primary MM cells isolated from lenalidomide resistant patients and in in vivo MM mouse model. Thus, our findings shed light on potential novel combinatorial therapeutic approaches modulating CD44 expression, which may help overcome lenalidomide resistance in myeloma patients.

A differentially expressed set of microRNAs in cerebro-spinal fluid (CSF) can diagnose CNS malignancies

Central Nervous System malignancies often require stereotactic biopsy or biopsy for differential diagnosis, and for tumor staging and grading. Furthermore, stereotactic biopsy can be non-diagnostic or underestimate grading. Hence, there is a compelling need of new diagnostic biomarkers to avoid such invasive procedures. Several biological markers have been proposed, but they can only identify specific prognostic subtype of Central Nervous System tumors, and none of them has found a standardized clinical application.The aim of the study was to identify a Cerebro-Spinal Fluid microRNA signature that could differentiate among Central Nervous System malignancies.CSF total RNA of 34 neoplastic and of 14 non-diseased patients was processed by NanoString. Comparison among groups (Normal, Benign, Glioblastoma, Medulloblastoma, Metastasis and Lymphoma) lead to the identification of a microRNA profile that was further confirmed by RT-PCR and in situ hybridization.Hsa-miR-451, -711, 935, -223 and -125b were significantly differentially expressed among the above mentioned groups, allowing us to draw an hypothetical diagnostic chart for Central Nervous System malignancies.This is the first study to employ the NanoString technique for Cerebro-Spinal Fluid microRNA profiling. In this article, we demonstrated that Cerebro-Spinal Fluid microRNA profiling mirrors Central Nervous System physiologic or pathologic conditions. Although more cases need to be tested, we identified a diagnostic Cerebro-Spinal Fluid microRNA signature with good perspectives for future diagnostic clinical applications.

Reduction in squamous cell carcinomas in mouse skin by dietary zinc supplementation

Inadequate dietary Zn consumption increases susceptibility to esophageal and other cancers in humans and model organisms. Since Zn supplementation can prevent cancers in rodent squamous cell carcinoma (SCC) models, we were interested in determining if it could have a preventive effect in a rodent skin cancer model, as a preclinical basis for considering a role for Zn in prevention of human nonmelanoma skin cancers, the most frequent cancers in humans. We used the 7,12-dimethyl benzanthracene carcinogen/phorbol myristate acetate tumor promoter treatment method to induce skin tumors in Zn-sufficient wild-type and Fhit (human or mouse protein) knockout mice. Fhit protein expression is lost in >50% of human cancers, including skin SCCs, and Fhit-deficient mice show increased sensitivity to carcinogen induction of tumors. We hypothesized that: (1) the skin cancer burdens would be reduced by Zn supplementation; (2) Fhit(-/-) (Fhit, murine fragile histidine triad gene) mice would show increased susceptibility to skin tumor induction versus wild-type mice. 30 weeks after initiating treatment, the tumor burden was increased ~2-fold in Fhit(-/-) versus wild-type mice (16.2 versus 7.6 tumors, P < 0.001); Zn supplementation significantly reduced tumor burdens in Fhit(-/-) mice (males and females combined, 16.2 unsupplemented versus 10.3 supplemented, P = 0.001). Most importantly, the SCC burden was reduced after Zn supplementation in both strains and genders of mice, most significantly in the wild-type males (P = 0.035). Although the mechanism(s) of action of Zn supplementation in skin tumor prevention is not known in detail, the Zn-supplemented tumors showed evidence of reduced DNA damage and some cohorts showed reduced inflammation scores. The results suggest that mild Zn supplementation should be tested for prevention of skin cancer in high-risk human cohorts.

Human anti-nucleolin recombinant immunoagent for cancer therapy

Nucleolin (NCL) is a nucleocytoplasmic protein involved in many biological processes, such as ribosomal assembly, rRNA processing, and mRNA stabilization. NCL also regulates the biogenesis of specific microRNAs (miRNAs) involved in tumor development and aggressiveness. Interestingly, NCL is expressed on the surface of actively proliferating cancer cells, but not on their normal counterparts. Therefore, NCL is an attractive target for antineoplastic treatments. Taking advantage of phage-display technology, we engineered a fully human single-chain fragment variable, named 4LB5. This immunoagent binds NCL on the cell surface, it is translocated into the cytoplasm of target cells, and it abrogates the biogenesis of NCL-dependent miRNAs. Binding of 4LB5 to NCL on the cell surface of a variety of breast cancer and hepatocellular carcinoma cell lines, but not to normal-like MCF-10a breast cells, dramatically reduces cancer cell viability and proliferation. Finally, in orthotopic breast cancer mouse models, 4LB5 administration results in a significant reduction of the tumor volume without evident side effects. In summary, here we describe, to our knowledge, the first anti-NCL single-chain fragment variable displaying antineoplastic activity against established solid tumors, which could represent the prototype of novel immune-based NCL-targeting drugs with clinical potential as diagnostic and therapeutic tools in a wide variety of human cancers.

The long journey of TCL1 transgenic mice: lessons learned in the last 15 years

The first transgenic mouse of the TCL1 oncogene was described more than 15 years ago, and since then, the overexpression of the gene in T- and B-cells in vivo has been extensively studied to reveal the molecular details in the pathogenesis of some lymphocytic leukemias. This review discusses the main features of the original TCL1 models and the different lines of research successively developed with particular attention to genetically compound mice and the therapeutic applications in drug development.

PTPROt-mediated regulation of p53/Foxm1 suppresses leukemic phenotype in a CLL mouse model

The gene encoding PTPROt is methylated and suppressed in Chronic Lymphocytc Leukemia. PTPROt exhibits in vitro tumor suppressor characteristics through the regulation of B-cell receptor signaling. Here, we generated transgenic (Tg) mice with B-cell specific expression of PTPROt. While lymphocyte development is normal in these mice, crossing them with TCL1 Tg mouse model of CLL results in a survival advantage compared to the TCL1 Tg mice. Gene expression profiling of splenic B-lymphocytes before detectable signs of CLL followed by Ingenuity Pathway Analysis revealed that the most prominently regulated functions in TCL1 Tg vs non-transgenic (NTg) and TCL1 Tg vs PTPROt/TCL1 double Tg are the same and also biologically relevant to this study. Further, enhanced expression of the chemokine Ccl3, the oncogenic transcription factor Foxm1 and its targets in TCL1 Tg mice were significantly suppressed in the double Tg mice suggesting a protective function of PTPROt against leukemogenesis. This study also showed that PTPROt mediated regulation of Foxm1 involves activation of p53, a transcriptional repressor of Foxm1, which is facilitated through suppression of B-cell receptor signaling. These results establish the in vivo tumor suppressive function of PTPROt, and identify p53/Foxm1 axis as a key downstream effect of PTPROt-mediated suppression of BCR signaling.

Pluripotent stem cell miRNAs and metastasis in invasive breast cancer

BACKGROUND

The purpose of this study is to determine whether microRNA for pluripotent stem cells are also expressed in breast cancer and are associated with metastasis and outcome.

METHODS

We studied global microRNA profiles during differentiation of human embryonic stem cells (n =26) and in breast cancer patients (n = 33) and human cell lines (n = 35). Using in situ hybridization, we then investigated MIR302 expression in 318 untreated breast cancer patients (test cohort, n = 22 and validation cohort, n = 296). In parallel, using next-generation sequencing data from breast cancer patients (n = 684), we assessed microRNA association with stem cell markers. All statistical tests were two-sided.

RESULTS

In healthy tissues, the MIR302 (high)/MIR203 (low) asymmetry was exclusive for pluripotent stem cells. MIR302 was expressed in a small population of cancer cells within invasive ductal carcinoma, but not in normal breast (P < .001). Furthermore, MIR302 was expressed in the tumor cells together with stem cell markers, such as CD44 and BMI1. Conversely, MIR203 expression in 684 breast tumors negatively correlated with CD44 (Spearman correlation, Rho = -0.08, P = .04) and BMI1 (Rho = -0.11, P = .004), but positively correlated with differentiation marker CD24 (Rho = 0.15, P < .001). Primary tumors with lymph node metastasis had cancer cells showing scattered expression of MIR302 and widespread repression of MIR203. Finally, overall survival was statistically significantly shorter in patients with MIR302-positive cancer cells (P = .03).

CONCLUSIONS

In healthy tissues the MIR302(high)/MIR203(low) asymmetry was characteristic of embryonic and induced pluripotency. In invasive ductal carcinoma, the MIR302/MIR203 asymmetry was associated with stem cell markers, metastasis, and shorter survival.

MicroRNA profiles discriminate among colon cancer metastasis

MicroRNAs are being exploited for diagnosis, prognosis and monitoring of cancer and other diseases. Their high tissue specificity and critical role in oncogenesis provide new biomarkers for the diagnosis and classification of cancer as well as predicting patients' outcomes. MicroRNAs signatures have been identified for many human tumors, including colorectal cancer (CRC). In most cases, metastatic disease is difficult to predict and to prevent with adequate therapies. The aim of our study was to identify a microRNA signature for metastatic CRC that could predict and differentiate metastatic target organ localization. Normal and cancer tissues of three different groups of CRC patients were analyzed. RNA microarray and TaqMan Array analysis were performed on 66 Italian patients with or without lymph nodes and/or liver recurrences. Data obtained with the two assays were analyzed separately and then intersected to identify a primary CRC metastatic signature. Five differentially expressed microRNAs (hsa-miR-21, -103, -93, -31 and -566) were validated by qRT-PCR on a second group of 16 American metastatic patients. In situ hybridization was performed on the 16 American patients as well as on three distinct commercial tissues microarray (TMA) containing normal adjacent colon, the primary adenocarcinoma, normal and metastatic lymph nodes and liver. Hsa-miRNA-21, -93, and -103 upregulation together with hsa-miR-566 downregulation defined the CRC metastatic signature, while in situ hybridization data identified a lymphonodal invasion profile. We provided the first microRNAs signature that could discriminate between colorectal recurrences to lymph nodes and liver and between colorectal liver metastasis and primary hepatic tumor.

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.

Abstract 5326: MicroRNA profiles discriminate among colon cancer metastasis

MicroRNAs are being exploited for diagnosis, prognosis and monitoring of cancer and other diseases. Their small non immunogenic size, high tissue specificity, and critical role in oncogenesis provide new biomarkers for diagnosing and classifying cancer as well as predicting patients’ outcomes. MicroRNAs signatures have been identified for many human tumors, including colorectal cancer. This tumor affects about one million individuals in developed countries, and about half of them die for recurrences. In most cases, metastatic disease is difficult to predict and to prevent with adequate therapies. The identification of microRNAs signatures for metastatic disease, could aid to define the risk and localization of recurrences in patients with unknown micrometastasis.

In this study, tissues of three different groups of colorectal cancer (CRC) patients were analyzed: microarray and cards analysis were performed on 66 patients with or without lymph nodes and/or liver recurrences; a second group of 16 metastatic patients were selected for RT-PCR; finally, in situ hybridization was carried out on tissue cores arrays belonging to a different set of patients with and without positive lymph nodes and/or liver metastasis.

MicroRNA-31, 21, 93, and 103 up-regulation together with miR-566 down-regulation defined the CRC metastatic signature. Moreover, in situ hybridization data defined metastatic localization: miR-200c up-regulation together with miR-566 down-regulation characterized lynphonodal invasion, while liver recurrences were defined by miR-31, 93 and 103 over-expression.

Citation Format: Mario Acunzo, Jerry G. Nuovo, Nicola Zanesi, Giampiero Di Leva, Flavia Pichiorri, Stefano Volinia, Cecilia Fernandez, Stefan Costinenan, Arianna Bottoni, Aaron Burch, Hansjuerg Alder, Laura Conti, Anna Antenucci, Immacolata A. Rosito, Antonio Ciardi, Chang G. Liu, Alessandra Drusco, Carlo M. Croce. MicroRNA profiles discriminate among colon cancer metastasis. [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 5326. doi:10.1158/1538-7445.AM2013-5326

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.

Cytotoxic and mutagenic effects of anti- and syn-benzo[a]pyrene diol epoxide in human lymphocytes

Cytotoxicity and mutagenicity were measured in human lymphocytes after treatment in vitro with anti- or syn-benzo[a]pyrene diolepoxide, two diastereoisomer metabolites of benzo[a]pyrene. These compounds were incubated with resting and cycling lymphocytes to determine the inhibition of cell proliferation induced by phytohemoagglutinin and interleukin2 at different times after treatment. Anti-benzo[a]pyrene diolepoxide was more cytotoxic than the syn-adduct under all conditions, and its effect on cell growth was more marked in cycling lymphocytes. In contrast, neither of the compounds induced alteration of the ATP intracellular pool. Cytotoxic effects of anti- and syn-benzo[a]pyrene diolepoxide were also assessed by determining the cloning efficiency. Both compounds affected the cloning efficiency in human lymphocytes and the effect of anti-benzo[a]pyrene was particularly marked. Mutagenic potency of anti- and syn-benzo[a]pyrene diolepoxide at the hgprt locus was measured both in the V79 cell line and in human lymphocytes by selection of mutant cells in medium containing 6-thioguanine. Both compounds increased the mutant frequency in comparison with the control and anti-benzo[a]pyrene diolepoxide was more active than the syn-metabolite.

Abstract 5032: New insights of miR-221 and miR-222 cluster functions in Burkitt lymphoma

Burkitt lymphoma (BL) is a mature aggressive B-cell neoplasm, with a characteristic clinical presentation, morphology and immunophenotype. Several studies have indicated the importance of miRNAs in B cell maturation and in the development of B cell lymphomas. MicroRNAs (miRNA) are a class of naturally occurring, small, non-coding RNA that can control gene expression by targeting mRNA molecules for translational repression or cleavage. They are usually expressed in a tissue-specific manner and play important roles in apoptosis, differentiation and cell proliferation; therefore their deregulation may be involved in carcinogenesis or tumor progression by altering normal gene expression patterns. Over the past years microRNAs signatures have been described to characterize and classify different types of BL or to investigate the expression of miRNAs possibly regulated by c-Myc in BL cases positive or negative for Myc traslocation. Howhever, it remained unclear the functional role of miRNAs that have been found differentially expressed and no further studies have been conducted. We performed miRNA expression profile to gain further insights into the molecular pathology of BL. We conducted array analysis on a set of 5 sporadic BL patients, 3 endemic BL patients, 9 reactive tissues and 11 cases of mononucleosis. A common trend of miRNAs altered expression was also observed by NanoString analysis in 10 BL cell lines compared to 5 normal CD-19+ B cells. Among several miRNAs previously described be deregulated in BL we identified a severe down-regulation of miR-221, miR-222 in all classes of comparisons we analyzed. The down-regulation of miR-221 and miR-222 associated to BL has been also confirmed by q-RT-PCR method in a different cohort of BL patients (20) compared to the healthy controls (6). When miR-221 and miR-222 expressions have been restored in BL cancer cell lines, lacking of their expression, by gene expression profile we identified the differentially expression of several genes involved in ncRNAs processing, ncRNA metabolic process and also in the regulation of cell differentiation and cell cycle. Furthermore, functional experiments identified many of these genes as new direct targets of miR-221 and miR-222. In conclusion, our study reveals new insights into the functional significance in loss of miR-221 and miR-222 expression in BL pathogenesis.

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 5032. doi:1538-7445.AM2012-5032

Abstract 1351: Analysis of the in vivo tumor suppressive potential of PTPROt (truncated protein tyrosine phosphatase receptor-type O) in CLL using a transgenic mouse model

Protein tyrosine phosphatases (PTPs) and kinases (PTKs) and their corresponding substrates are integrated within elaborate signal transduction networks essential for regulating several important cellular functions including growth, differentiation, cell cycle, gene transcription, the immune response and survival. Defective operation of these networks leads to aberrant tyrosine phosphorylation that contributes to the development of many human diseases including cancer. Importantly, as observed with PTKs, deregulation of PTPs plays a key role in the pathogenesis of these diseases. Thus, PTPs and their substrates represent novel molecular targets for the development of agents in the treatment of these diseases. We have previously demonstrated that the gene encoding the hematopoietic-specific truncated isoform of protein tyrosine phosphatase receptor-type O (PTPROt), a phosphatase demonstrating growth suppressor characteristics, is suppressed in chronic lymphocytic leukemia (Clin Cancer Res. 2007 Jun 1;13(11):3174-81). We have further shown that expression of PTPROt is severely impeded by T-cell leukemia 1 (TCL1), an oncoprotein aberrantly expressed in CLL B-cells (Blood. 2011 Oct 14. [Epub ahead of print]). Additionally, PTPROt plays an important role in regulating B-cell receptor (BCR) signaling (J Cell Biochem. 2010 Jul 1;110(4):846-56; Blood. 2006 Nov 15;108(10):3428-33). To comprehend the physiological relevance of PTPROt we have now generated transgenic (Tg) mice expressing PTPROt in B-cells. These mice live their normal life span and exhibit normal B- and T-cell development. Lyn and SYK kinases, the established substrates of PTPROt, are hypo-phosphorylated in B-lymphocytes from the spleen of PTPROt Tg mice relative to those from NTg mice. Because expression of PTPROt is significantly lower in splenic B-lymphocytes from TCL1 Tg mouse model of CLL relative to splenic B-cells from non-transgenic (NTg) mice (Blood. 2011 Oct 14. [Epub ahead of print]), we crossed the TCL1 Tg and PTPROt Tg mice to determine whether expression of PTPROt will inhibit/delay TCL1-mediated leukemogenesis and utilize this model to elucidate the mechanism of PTPROt function in maintaining normal cell physiology. Preliminary gene expression analysis performed on splenic B-cells from NTg, TCL1 Tg and PTPROt/TCL1 double Tg mice demonstrated that the key positive regulators of cell cycle elevated in the TCL1 Tg mice (relative to the NTg mice) are downregulated in the PTPROt/TCL1 double Tg mice (relative to the TCL1 Tg mice). Further, the spleen size as well as the total number of spleen cells was significantly lower in the PTPROt/TCL1 double Tg group relative to the TCL1 Tg group. We are currently in the process of assessing the function of the altered genes in the TCL1 Tg mouse model as well as in human CLL. [Supported by grant CA101956]

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 1351. doi:1538-7445.AM2012-1351

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 2185: DLEU7 is a putative tumor suppressor in glioblastoma

DLEU7 was first identified as a tumor suppressor in B-CLL. We previously showed that Dleu7 functions as a potent NF-kappaB and NFAT inhibitor. To investigate possible function of Dleu7 in brain tumorigenesis we carried out the real-time PCR of RNAs isolated from different parts of human brain, brain tumors and brain tumor cell lines and found that expression of DLEU7 significantly decreased in brain tumor cell lines and brain tumors (glioblastoma) in comparison with normal brain tissues. We further investigated the effect of DLEU7 expression in HTB-15 glioblastoma cell line. Our results showed that Dleu7 overexpression resulted in apoptosis and cell cycle halt. In addition, adenovirus-mediated DLEU7 expression resulted in 100 percent increase of caspase 3/7 activation compared to AdenoGFP control in HTB-15 cells. Our data indicate that DLEU7 may play a tumor suppressor role in glioblastoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2185. doi:10.1158/1538-7445.AM2011-2185

Abstract 276: Role of AP1 elements and TCL1 protein in regulation of the gene encoding PTPROt (protein tyrosine phosphatase receptor-type O) in chronic lymphocytic leukemia

The gene for protein tyrosine phosphatase receptor-type O encodes two functional isoforms in a tissue-specific manner. The full-length form is expressed in epithelial cells, particularly in the brain and kidney, whereas the truncated form (PTPROt) is primarily expressed in hematopoietic cells. We have previously demonstrated that PTPROt is a bona fide tumor suppressor (J Biol Chem. 2009 Jan 2;284(1):455-64) and is down-regulated in primary CLL samples (Clin Cancer Res. 2007 Jun 1;13(11):3174-81). Further, studies from two laboratories including ours have shown that Syk and Lyn, two key protein tyrosine kinases involved in B-cell receptor signaling, are substrates of PTPROt, igniting interest in understanding deregulation of this tyrosine phosphatase in CLL. While the PTPRO promoter is methylated, the mechanism of its silencing in the pathogenesis of CLL is unexplored. Here, we utilized the Tcl1 transgenic (Tg) mouse model of CLL and a cell line with TPA-inducible expression of PTPROt to elucidate the mechanism of PTPROt silencing. This study demonstrates that PTPROt is transcriptionally silenced in CD19+ spleen B cells from Tcl1 transgenic (Tg) mouse when compared to wild type mice. As observed with primary human CLL, the methylation of PTPRO CGI (CpG island) is significantly higher in Tcl1 Tg CLL B-lymphocytes than in normal B lymphocytes. Significant suppression of PTPROt is also observed at very early time-point (∼7 wks) in CD19+ spleen B-cells from Tcl1 Tg mice compared to normal spleen B-lymphocytes from age-matched WT mice in the absence of detectable methylation at CGI. This data suggests that transcriptional silencing occurs prior to methylation. To understand further the potential transcriptional mechanism of PTPROt suppression in CLL, the role of AP1 in the expression of this gene was explored. We first demonstrate that AP-1 activation by TPA in U937 cells induces PTPROt expression with concurrent recruitment of c-fos and c-jun to its promoter. PTPROt promoter is also responsive to over- and under-expression of AP-1 confirming the role of AP-1 in PTPROt expression. Next, we demonstrate that Tcl1 can repress PTPROt promoter by altering c-fos expression and c-jun activation state. These findings further substantiate the importance of TCL1 in the pathogenesis of CLL.

[Supported, in part, by grants CA101956 and CA086978].

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 276. doi:10.1158/1538-7445.AM2011-276

Abstract B62: Zinc supplementation reduces forestomach tumor burden in N-nitrosomethylbenzylamine-treated mice

Zinc deficiency is associated with high incidences of esophageal and other human cancers. In addition, zinc status in plasma and white blood cells is a better indicator of tumor burden and stage of the disease in head and neck cancer patients than overall nutritional status. Research in rodents found that zinc insufficiency leads to a highly proliferative hyperplastic condition in the upper gastrointestinal tract. Zn replenishment reduces the incidence of lingual, esophageal, and forestomach tumors in Zn-deficient rats and mice. While previous animal studies focused on the effect of Zn deficiency on cancer prevention and development, in this study we investigated the effect of Zn supplementation on carcinogenesis in Zn-sufficient mice of wild type and three tumor suppressor-deficient mouse strains, Fhit−/−, Fhit−/−Nit1−/−, and Fhit−/−Rassf1a−/−. About fifty mice from each strain received 6-8 doses of N-nitrosomethylbenzylamine (NMBA). Half the mice then received Zn supplemented water while another half received regular water. Sixteen weeks after last NMBA administration, mice were sacrificed and tumors were found only in forestomach. Mice without Zn supplementation had developed more tumors than Zn-supplemented mice: wild type C57BL/6 mice developed an average of 7.0 vs 5.0 tumors for Zn supplemented (p&lt;0.05); Zn-supplemented Fhit−/− mice averaged 5.7 vs 8.0 for control mice (p&lt; 0.01); Zn-supplemented Fhit−/−Nit1−/− mice averaged 5.4 vs 9.2 for control mice (p&lt; 0.01); and Zn-supplemented Fhit−/−Rassf1a−/−mice averaged 5.9 vs 9.1 for control mice (p&lt; 0.01). Zn supplementation reduced tumor burdens by 28% (wild type) to 42% (Fhit−/−Nit1−/−). Histological analysis of forestomach tissues also showed significant decreases in severity of preneoplastic and neoplastic lesions in Zn-supplemented cohorts of each mouse strain. Thus, Zn supplementation significantly reduced tumor burdens in mice with multiple tumor suppressor deficiencies. When Zn supplementation was begun at 7 weeks after the final carcinogen dose, the reduction in tumor burden was the same as observed when supplementation began immediately after carcinogen dosing, suggesting that Zn supplementation may affect tumor progression rather than tumor initiation. Our study suggests that Zn could have an important role in tumor prevention and perhaps treatment of specific human cancers and should be more thoroughly studied in preclinical models.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):B62.

Molecular basis of CLL

B-cell chronic lymphocytic leukemia (CLL), the most common leukemia in the Western world, results from an expansion of a rare population of CD5+ mature B-lymphocytes. CLL occurs in two forms, aggressive and indolent. For the most part indolent CLL is characterized by low ZAP-70 expression and mutated IgH V(H); aggressive CLL shows high ZAP-70 expression and unmutated IgH V(H). Although clinical features and genomic abnormalities in CLL have been studied extensively, molecular mechanisms underlying disease development are still emerging. In the last few years, several important insights were reported in this area. MiR-15/16 targeting BCL2 and MCL1 and DLEU7 targeting TNF pathway were proposed as tumor suppressors at 13q14, a commonly deleted region in indolent CLL. Molecular details of how activation of TCL1, a critical oncogene in aggressive CLL, results in the initiation of this malignancy were clarified. Importance of these pathways was supported by investigations of several mouse models of CLL. Here, we present what has been learned from these new pathways, discuss mouse CLL models and how these mouse models recapitulate the molecular mechanisms of this common leukemia.

Effect of zinc supplementation on N-nitrosomethylbenzylamine-induced forestomach tumor development and progression in tumor suppressor-deficient mouse strains

Zinc deficiency is associated with high incidences of esophageal and other cancers in humans and leads to a highly proliferative hyperplastic condition in the upper gastrointestinal tract in laboratory rodents. Zn replenishment reduces the incidence of lingual, esophageal and forestomach tumors in Zn-deficient rats and mice. While previous animal studies focused on Zn deficiency, we have investigated the effect of Zn supplementation on carcinogenesis in Zn-sufficient mice of wild-type and tumor suppressor-deficient mouse strains. All mice received N-nitrosomethylbenzylamine and half the mice of each strain then received Zn supplementation. At killing, mice without Zn supplementation had developed more tumors than Zn-supplemented mice: wild-type C57BL/6 mice developed an average of 7.0 versus 5.0 tumors for Zn supplemented (P < 0.05); Zn-supplemented Fhit-/- mice averaged 5.7 versus 8.0 for control mice (P < 0.01); Zn-supplemented Fhit-/-Nit1-/- mice averaged 5.4 versus 9.2 for control mice (P < 0.01) and Zn-supplemented Fhit-/-Rassf1a-/- (the murine gene) mice averaged 5.9 versus 9.1 for control mice (P < 0.01). Zn supplementation reduced tumor burdens by 28% (wild-type) to 42% (Fhit-/-Nit1-/-). Histological analysis of forestomach tissues also showed significant decreases in severity of preneoplastic and neoplastic lesions in Zn-supplemented cohorts of each mouse strain. Thus, Zn supplementation significantly reduced tumor burdens in mice with multiple tumor suppressor deficiencies. When Zn supplementation was begun at 7 weeks after the final carcinogen dose, the reduction in tumor burden was the same as observed when supplementation began immediately after carcinogen dosing, suggesting that Zn supplementation may affect tumor progression rather than tumor initiation.

Reprogramming of miRNA networks in cancer and leukemia

We studied miRNA profiles in 4419 human samples (3312 neoplastic, 1107 nonmalignant), corresponding to 50 normal tissues and 51 cancer types. The complexity of our database enabled us to perform a detailed analysis of microRNA (miRNA) activities. We inferred genetic networks from miRNA expression in normal tissues and cancer. We also built, for the first time, specialized miRNA networks for solid tumors and leukemias. Nonmalignant tissues and cancer networks displayed a change in hubs, the most connected miRNAs. hsa-miR-103/106 were downgraded in cancer, whereas hsa-miR-30 became most prominent. Cancer networks appeared as built from disjointed subnetworks, as opposed to normal tissues. A comparison of these nets allowed us to identify key miRNA cliques in cancer. We also investigated miRNA copy number alterations in 744 cancer samples, at a resolution of 150 kb. Members of miRNA families should be similarly deleted or amplified, since they repress the same cellular targets and are thus expected to have similar impacts on oncogenesis. We correctly identified hsa-miR-17/92 family as amplified and the hsa-miR-143/145 cluster as deleted. Other miRNAs, such as hsa-miR-30 and hsa-miR-204, were found to be physically altered at the DNA copy number level as well. By combining differential expression, genetic networks, and DNA copy number alterations, we confirmed, or discovered, miRNAs with comprehensive roles in cancer. Finally, we experimentally validated the miRNA network with acute lymphocytic leukemia originated in Mir155 transgenic mice. Most of miRNAs deregulated in these transgenic mice were located close to hsa-miR-155 in the cancer network.

Frequent attenuation of the WWOX tumor suppressor in osteosarcoma is associated with increased tumorigenicity and aberrant RUNX2 expression

The WW domain-containing oxidoreductase (WWOX) is a tumor suppressor that is deleted or attenuated in most human tumors. Wwox-deficient mice develop osteosarcoma (OS), an aggressive bone tumor with poor prognosis that often metastasizes to lung. On the basis of these observations, we examined the status of WWOX in human OS specimens and cell lines. In human OS clinical samples, WWOX expression was absent or reduced in 58% of tumors examined (P < 0.0001). Compared with the primary tumors, WWOX levels frequently increased in tumors resected following chemotherapy. In contrast, tumor metastases to lung often exhibited reduced WWOX levels relative to the primary tumor. In human OS cell lines having reduced WWOX expression, ectopic expression of WWOX inhibited proliferation and attenuated invasion in vitro, and suppressed tumorigenicity in nude mice. Expression of WWOX was associated with reduced RUNX2 expression in OS cell lines, whereas RUNX2 levels were elevated in femurs of Wwox-deficient mice. Furthermore, WWOX reconstitution in HOS cells was associated with downregulation of RUNX2 levels and RUNX2 target genes, consistent with the ability of WWOX to suppress RUNX2 transactivation activity. In clinical samples, RUNX2 was expressed in the majority of primary tumors and undetectable in most tumors resected following chemotherapy, whereas most metastases were RUNX2 positive. Our results deepen the evidence of a tumor suppressor role for WWOX in OS, furthering its prognostic and therapeutic significance in this disease.

Abstract 2087: miR-483-3p is an oncogene involved in nephroblastoma and in adult tumors with activated β-catenin

The hsa-mir-483 locus is located within intron 2 of the IGF2 locus. Here, we show that the mature microRNA (miRNA) miR-483-3p is over-expressed and co-regulated with IGF2 in 100% of Wilms’ tumors. Additionally, several types of common adult cancers exhibit high or even extremely high levels of miR-483-3p. We show that the mutation status of the oncoprotein β-catenin is correlated with the expression of the miR-483-3p in hepatocarcinoma and colorectal cancer. These findings suggested an autonomous oncogenic function for this miRNA. Indeed, anti-microRNA oligonucleotide (AMO) against miR-483-3p could inhibit tumorigenicity of HepG2 cells. At the same time, no anti-tumor effect was elicited by inhibition of IGF2. The oncogenic properties of miR-483-3p were further supported by the finding that its ectopic expression could protect cells from apoptosis through the regulation of one important pro-apoptotic protein, Puma. Our results indicate that miR-483-3p can function as an anti-apoptotic oncogene in various human cancers and reveal a new potentially important target for anti-cancer therapy.

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 2087.

Abstract 401: CD5+CD23+ leukemic cell populations in Tcl1 transgenic mice show significantly increased proliferation and Akt phosphorylation

B-cell chronic lymphocytic leukemia (B-CLL) is the most common human leukemia. Deregulation of the T-cell leukemia/lymphoma 1 (TCL1) oncogene in mouse B-cells causes a CD5 positive leukemia similar to aggressive human B-CLLs. We recently reported that TCL1 expression in B-CLL is regulated by miR29 and miR181. To determine whether treatment with microRNAs can inhibit

B-CLL in mice by targeting TCL1 we generated TCL1 transgenic mice using a construct containing 3’ and 5’ UTRs of TCL1 under B-cell specific Eμ promoter (Eμ-TCL1fl). At the age of 12-18 months these mice showed B-CLL like disease. Immunophenotyping revealed accumulation of CD5+CD23+B220+ population in spleens and lymph nodes. Our results show that CD5+CD23+ B-cell populations from Eμ-TCL1fl mice actively proliferate and display significantly increased levels of phospho-Akt. Eμ-TCL1fl mice showed immunological abnormalities similar to human B-CLL, including hypoimmunoglobulinemia, abnormal levels of cytokines, and impaired immune response. These findings revealed biochemical and immunological similarities between Tcl1 driven B-CLL in mice and human B-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 401.

Abstract LB-352: B-CLL phenotype in Eµ-miR-29 transgenic mice

B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in the western world. Human B-CLL occurs in two forms: aggressive (showing high ZAP-70 expression and unmutated IgH VH) and indolent (showing low ZAP-70 expression and mutated IgH VH). We found that miR-29a is upregulated in indolent human B-CLL compared to aggressive B-CLL and normal CD19+ B-cells. To study the role of miR-29 in B-CLL, we generated Eµ-miR-29 transgenic mice overexpressing miR-29 in mouse B-cells. Flow cytometric analysis revealed a markedly expanded CD5+ population in the spleen of these mice starting at 2 months of age. Over 80% of miR-29 transgenic mice exhibited an expanded population of CD5+ B-cells, a characteristic of the B-CLL phenotype. An average of 56% of the B-cell population in these transgenics were CD5 positive. At the age of 2 years these mice showed significantly enlarged spleens and an increase in CD5+ B-cell population of up to 100% of B-cells. Over 8% (3/36) of Eµ-miR-29 transgenic mice developed frank leukemia and prematurely died from the disease at the age of 24-26 months. The expanded CD5+ B-cell population was found to be proliferative, with an increased number of cells in the S-phase of the cell cycle, compared to wild type CD19+ B-cells. These results suggest that deregulation of miR-29 can cause, or at least significantly contribute to the pathogenesis of indolent B-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 LB-352.

Oncogenic role of miR-483-3p at the IGF2/483 locus

hsa-mir-483 is located within intron 2 of the IGF2 locus. We found that the mature microRNA (miRNA) miR-483-3p is overexpressed in 100% of Wilms' tumors. In addition, colon, breast, and liver cancers exhibit high or even extremely high levels of miR-483-3p in approximately 30% of the cases. A coregulation with IGF2 mRNA was detected, although some tumors exhibited high expression of miR-483-3p without a concomitant increase of IGF2. These findings suggested that miR-483-3p could cooperate with IGF2 or act as an autonomous oncogene. Indeed, here we prove that an anti-miRNA oligonucleotide against miR-483-3p could inhibit the miRNAs without affecting IGF2 mRNA and it could suppress tumorigenicity of HepG2 cells, a cell line that overexpresses miR-483-3p and IGF2. Conversely, no antitumor effect was elicited by inhibition of IGF2. The oncogenic mechanism of miR-483-3p was at least partially clarified by the finding that it could modulate the proapoptotic protein BBC3/PUMA and miR-483-3p enforced expression could protect cells from apoptosis. Our results indicate that miR-483-3p could function as an antiapoptotic oncogene in various human cancers and reveal a new, potentially important target for anticancer therapy.

MicroRNAs in mouse models of lymphoid malignancies

The discovery of microRNAs (miRNAs) has revealed a new layer of gene expression regulation that affects many normal and pathologic biological systems. Among the malignancies affected by the dysregulation of miRNAs there are cancers of lymphoid origin, in which miRNAs are thought to have tumor suppressive or tumor promoting activities, depending on the nature of their specific targets. In the last 4-5 years, the experimental field that provided the deepest insights into the in vivo biology of miRNAs is that of mouse modeling in which transgenic and knockout animals mimic, respectively, over-expression or down-regulation of specific miRNAs involved in human leukemia/lymphoma. This review discusses recent advances in our understanding of lymphoid malignancies based on the natural and engineered mouse models of three different miRNAs, miR-15a/16-1 cluster, miR-155, and miR-17-92 cluster.

Oncosuppressor proteins of fragile sites are reduced in cervical cancer

FHIT and WWOX are tumor suppressor genes that span the common fragile sites FRA3B and FRA16D, respectively. To analyze possible synergisms among these genes in cervical cancer progression, we considered 159 cervical intraepithelial neoplasias, and 58 invasive squamous cell carcinomas of the uterine cervix. All cases were previously selected as high risk HPV. FHIT and WWOX proteins were examined by immunohistochemistry and their expression was inversely correlated with precancerous vs. invasive lesions. Statistics among biological markers indicated an association between FHIT and WWOX. Protein expression of these two genes was also absent or reduced in cancer cell lines. Thus, WWOX may be considered as a novel important genetic marker in cervical cancer and the association between the altered expression of FHIT and WWOX may be a critical event in the progression of this neoplasia.

Influence of a nonfragile FHIT transgene on murine tumor susceptibility

FHIT, at a constitutively active chromosome fragile site, is often a target of chromosomal aberrations and deletion in a large fraction of human tumors. Inactivation of murine Fhit allelessignificantly increases susceptibility of mice to spontaneous and carcinogen-induced tumorigenesis. In this study, transgenic mice, carrying a human FHIT cDNA under control of the endogenous promoter, were produced to determine the effect of Fhit expression, from a nonfragile cDNA transgene outside the fragile region, on carcinogen-induced tumor susceptibility of wildtype and Fhit heterozygous mice. Mice received sufficient oral doses of N-nitrosomethybenzylamine (NMBA) to cause forestomach tumors in >80% of nontransgenic control mice. Although the level of expression of the FHIT transgene in the recombinant mouse strains was much lower than the level of endogenous Fhit expression, the tumor burden in NMBA-treated male transgenic mice was significantly reduced, while female transgenic mice were not protected. To determine if the difference in protection could be due to differences in epigenetic changes at the transgene loci in male versus female mice, we examined expression, hypermethylation and induced re-expression of FHIT transgenes in male and female mice or cells derived from them. The transgene was methylated in male and female mice and in cell lines established from male and female transgenic kidneys, the FHIT locus was both hypermethylated and deacetylated. It is likely that the FHIT transgene is more tightly silenced in female transgenic mice, leading to a lack of protection from tumor induction.

MicroRNA-29 family reverts aberrant methylation in lung cancer by targeting DNA methyltransferases 3A and 3B

MicroRNAs (miRNAs) are small, noncoding RNAs that regulate expression of many genes. Recent studies suggest roles of miRNAs in carcinogenesis. We and others have shown that expression profiles of miRNAs are different in lung cancer vs. normal lung, although the significance of this aberrant expression is poorly understood. Among the reported down-regulated miRNAs in lung cancer, the miRNA (miR)-29 family (29a, 29b, and 29c) has intriguing complementarities to the 3'-UTRs of DNA methyltransferase (DNMT)3A and -3B (de novo methyltransferases), two key enzymes involved in DNA methylation, that are frequently up-regulated in lung cancer and associated with poor prognosis. We investigated whether miR-29s could target DNMT3A and -B and whether restoration of miR-29s could normalize aberrant patterns of methylation in non-small-cell lung cancer. Here we show that expression of miR-29s is inversely correlated to DNMT3A and -3B in lung cancer tissues, and that miR-29s directly target both DNMT3A and -3B. The enforced expression of miR-29s in lung cancer cell lines restores normal patterns of DNA methylation, induces reexpression of methylation-silenced tumor suppressor genes, such as FHIT and WWOX, and inhibits tumorigenicity in vitro and in vivo. These findings support a role of miR-29s in epigenetic normalization of NSCLC, providing a rationale for the development of miRNA-based strategies for the treatment of lung cancer.

Animal models for chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL), the most common leukemia in the Western world, results from an expansion of a rare population of CD5+ mature B-lymphocytes. Although clinical features and genomic abnormalities in B-CLL have been studied in considerable detail, the molecular mechanisms underlying disease development has remained unclear until recently. In the last 4 years, several transgenic mouse models for B-CLL were generated. Investigations of these mouse models revealed that deregulation of three pathways, Tcl1-Akt pathway, TNF-NF-kB pathway, and Bcl2-mediated anti-apoptotic pathway, result in the development of B-CLL. While deregulation of TCL1 alone caused a B-CLL phenotype in mice, overexpression of Bcl2 required aberrantly activated TNF-NF-kB pathway signaling to yield the disease phenotype. In this article, we present what has been learned from mice with B-CLL phenotype and how these mouse models of B-CLL were used to test therapeutic treatments for this common leukemia.

Fez1/Lzts1 absence impairs Cdk1/Cdc25C interaction during mitosis and predisposes mice to cancer development

The FEZ1/LZTS1 (LZTS1) protein is frequently downregulated in human cancers of different histotypes. LZTS1 is expressed in normal tissues, and its introduction in cancer cells inhibits cell growth and suppresses tumorigenicity, owing to an accumulation of cells in G2/M. Here, we define its role in cell cycle regulation and tumor progression by generating Lzts1 knockout mice. In Lzts1(-/-) mouse embryo fibroblasts (MEFs), Cdc25C degradation was increased during M phase, resulting in decreased Cdk1 activity. As a consequence, Lzts1(-/-) MEFs showed accelerated mitotic progression, resistance to taxol- and nocodazole-induced M phase arrest, and improper chromosome segregation. Accordingly, Lzts1 deficiency was associated with an increased incidence of both spontaneous and carcinogen-induced cancers in mice.

Targeted deletion of Wwox reveals a tumor suppressor function

The WW domain-containing oxidoreductase (WWOX) spans the second most common fragile site of the human genome, FRA16D, located at 16q23, and its expression is altered in several types of human cancer. We have previously shown that restoration of WWOX expression in cancer cells suppresses tumorigenicity. To investigate WWOX tumor suppressor function in vivo, we generated mice carrying a targeted deletion of the Wwox gene and monitored incidence of tumor formation. Osteosarcomas in juvenile Wwox(-/-) and lung papillary carcinoma in adult Wwox(+/-) mice occurred spontaneously. In addition, Wwox(+/-) mice develop significantly more ethyl nitrosourea-induced lung tumors and lymphomas in comparison to wild-type littermate mice. Intriguingly, these tumors still express Wwox protein, suggesting haploinsuffiency of WWOX itself is cancer predisposing. These results indicate that WWOX is a bona fide tumor suppressor.

Molecular and cytogenetical alterations induced by environmental cigarette smoke in mice heterozygous for Fhit

Previous studies in humans and animal models provided evidence that the Fhit gene is an early target for cigarette smoke. We compared the induction of a variety of molecular and cytogenetical alterations in B6-129(F(1)) mice, either wild type or Fhit(+/-), after whole-body exposure to environmental cigarette smoke (ECS) for 15 consecutive days. Both mouse genotypes responded to ECS with a loss of Fhit protein in the bronchial epithelium, accompanied by induction of apoptosis and stimulation of cell proliferation. ECS induced formation of bulky DNA adducts in whole lung. In addition, ECS caused cytogenetical damage both in the respiratory tract and at a systemic level, as shown by a significant increase of micronucleus frequency in pulmonary alveolar macrophages, bone marrow polychromatic erythrocytes, and peripheral blood normochromatic erythrocytes of both wild-type and Fhit(+/-) mice. These results are compared with those generated in other species, strains, and genotypes of rodents exposed to ECS that we investigated previously. Although the loss of Fhit protein in the bronchial epithelium of ECS-exposed B6-129(F(1)) mice provides further evidence that the Fhit gene is an early molecular target for ECS, heterozygosity for Fhit does not seem to confer an increased susceptibility of mice in terms of the investigated early biomarkers.

FHIT-proteasome degradation caused by mitogenic stimulation of the EGF receptor family in cancer cells

The tumor suppressor gene FHIT is inactivated by genetic and epigenetic changes in the majority of common human cancers. The human Fhit protein undergoes phosphorylation on tyrosine residue 114 by Src and related kinases both in vitro and in vivo. Src is a key cytoplasmic tyrosine kinase downstream to several growth factor receptors, including those of the EGF receptor family, which are overexpressed and activated in about one-third of human breast and ovarian carcinomas. However, the biological significance of Fhit phosphorylation by Src has remained elusive. In the present study, we demonstrate that FHIT acts as a checkpoint in cell proliferation mediated by activated tyrosine kinase receptors that recruit Src. Activation of EGF receptor family members induced Fhit phosphorylation by Src and the subsequent proteasome degradation of the phosphorylated Fhit protein. Indeed, the use of the Fhit mutant Y114F, which carries a phenylalanine instead of a tyrosine at position 114, unable to be phosphorylated on tyrosine 114 by Src, prevents Fhit degradation. Moreover, Fhit protein reduction is transient and occurs in a specific temporal window. During the signaling pathway of activated tyrosine kinase receptors, the phosphorylation of Fhit induces its degradation and the subsequent reduction in Fhit protein levels allows the transmission of the mitogenic signal; immediately thereafter, Fhit protein levels are restored. Such a scenario would suggest a key role for Fhit in the balance of proliferation/survival/apoptosis signals.

Tal1 transgenic expression reveals absence of B lymphocytes

TAL1 oncogene encodes a helix-loop-helix transcription factor, Tal1, which is required for blood cell development, and its activation is a frequent event in T-cell acute lymphoblastic leukemia. Tal1 interacts and inhibits other helix-loop-helix factors such as E47 and HEB. To investigate the function of Tal1 in B cells, we generated Emu-TAL1 transgenic mouse line, expressing Tal1 in mouse B-cell lineage. Fluorescence-activated cell sorting (FACS) analysis of lymphocytes isolated from spleens of five out of five founders reveals complete absence of IgM- or CD19-expressing cells. Only 2% to 3% of these cells were B220+ and 100% of B220+ cells were CD43+, indicating that these mice were able to make pro-B cells. Similarly, FACS analysis of bone marrow cells in Emu-TAL1 mice revealed complete absence of B220+IgM+ and B220+CD19+ cells. Analysis of the recombination status of IgH genes revealed the presence of D-J but absence or drastic reduction of V-D-J rearrangements. Our results suggest that Tal1 overexpression in B cells results in a phenotype similar to that of B cells of E47/E2A knockout animals. This represents first in vivo evidence that Tal1 can completely inhibit E47/E2A function.

Genetic ablation of Ptprj, a mouse cancer susceptibility gene, results in normal growth and development and does not predispose to spontaneous tumorigenesis

Ptprj is a ubiquitously expressed murine gene encoding a receptor-type protein tyrosine phosphatase, which has recently been proposed as a candidate gene on the locus Scc1 for colon cancer susceptibility. It has been demonstrated that PTPRJ, the human homologue of Ptprj, is involved in the control of cell growth and adhesion, being furthermore altered in several types of cancer including mammary, thyroid, lung, colon, and pancreatic cancers. To investigate the biological functions of Ptprj, we have generated mice deficient in this receptor protein tyrosine phosphatase. Ptprj-deficient mice are viable, fertile, and show no gross anatomical alterations. Furthermore, neither changes in life span nor spontaneous tumor appearance were observed in Ptprj-null mice. Our results indicate that Ptprj is dispensable for normal growth and development in mice.

B cell receptors in TCL1 transgenic mice resemble those of aggressive, treatment-resistant human chronic lymphocytic leukemia

B cell chronic lymphocytic leukemia (B-CLL) is a clonal overgrowth of CD5(+) B lymphocytes. In this disease, the B cell antigen receptor (BCR) is intimately linked to disease severity, because patients with BCRs, comprised of unmutated V(H) genes, follow a much more aggressive course. This and related observations suggest that B-CLL derives from a B cell subset comprised of restricted BCR structural diversity and that antigen-selection and drive are major factors promoting the disease. Nevertheless, the initiating event(s) that lead to the development of B-CLL are still unclear, in part because of the lack of an animal model that spontaneously evolves the molecular abnormalities that occur in the human disease. Because overexpression of the TCL1 gene in murine B cells leads to a CD5(+) B cell lymphoproliferative disorder with many of the features of human B-CLL, we studied leukemias emerging in these mice to examine the extent to which their BCRs resemble those in B-CLL. Our data indicate that the immunoglobulin heavy and light chain rearrangements in TCL1 mice display minimal levels of somatic mutations and exhibit several molecular features found in the human disease. Like human B-CLL, TCL1 leukemic rearrangements from different mice can be very similar structurally and closely resemble autoantibodies and antibodies reactive with microbial antigens. Antigen-binding analyses confirm that selected TCL1 clones react with glycerophospholipid, lipoprotein, and polysaccharides that can be autoantigens and be expressed by microbes. This (auto)antigen-driven mouse model reliably captures the BCR characteristics of aggressive, treatment-resistant human B-CLL.

Early loss of Fhit in the respiratory tract of rodents exposed to environmental cigarette smoke

The Fhit gene, encompassing the most active common human chromosomal fragile region, FRA3B, has been shown to act as a tumor suppressor. Several studies have shown significant Fhit alterations or Fhit protein loss in lung cancers from smokers compared with lung cancers from nonsmokers. To evaluate the role of Fhit under controlled experimental conditions, we exposed rodents to environmental cigarette smoke (ECS) and evaluated Fhit expression or Fhit protein in the respiratory tract. After 14 days of exposure to ECS, loss of Fhit protein in the bronchial/bronchiolar epithelium affected half of the tested B6-129(F(1)) mice, either wild type or Fhit(+/-). After 28 days, it affected the vast majority of the tested SKH-1 hairless mice and of A/J mice and all (UL53-3 x A/J)F(1) mice, either wild type or P53(+/-). In Sprague-Dawley rats, exposure to ECS for up to 30 days caused a time-dependent loss of Fhit in pulmonary alveolar macrophages. Moreover, ECS down-regulated Fhit expression and significantly decreased Fhit protein in the rat bronchial epithelium. The oral administration of N-acetylcysteine attenuated the ECS-related loss of Fhit, whereas oltipraz, 5,6-benzoflavone, phenethyl isothiocyanate, and indole 3-carbinol, and their combinations had no significant effect. Parallel studies evaluated a variety of molecular, biochemical, and cytogenetic alterations in the respiratory tract of the same animals. In conclusion, there is unequivocal evidence that Fhit is an early, critical target in smoke-related lung carcinogenesis in rodents, and that certain chemopreventive agents can attenuate the occurrence of this gene alteration.

Influence of FHIT on benzo[a]pyrene-induced tumors and alopecia in mice: chemoprevention by budesonide and N-acetylcysteine

The FHIT gene has many hallmarks of a tumor-suppressor gene and is involved in a large variety of cancers. We treated A/J mice and (C57BL/6J x 129/SvJ)F1 (B6/129 F1) mice, either wild-type or FHIT+/-, with multiple doses of benzo[a]pyrene (B[a]P) by gavage. B[a]P caused a time-related increase of micronuclei in peripheral blood erythrocytes. Both A/J and B6/129 F1 mice, irrespective of their FHIT status, were sensitive to induction of forestomach tumors, whereas B[a]P induced glandular stomach hyperplasia and a high multiplicity of lung tumors in A/J mice only. Preneoplastic lesions of the uterus were more frequent in FHIT+/- mice. B6/129 F1 mice underwent spontaneous alopecia areata and hair bulb cell apoptosis, which were greatly accelerated either by FHIT heterozygosity or by B[a]P treatment, thus suggesting that FHIT plays a role in the pathogenesis of alopecia areata. The oral administration of either budesonide or N-acetyl-L-cysteine (NAC) inhibited the occurrence of this inflammatory skin disease. In addition, these agents prevented B[a]P-induced glandular stomach hyperplasia and decreased the size of both forestomach tumors and lung tumors in A/J mice. Budesonide also attenuated lung tumor multiplicity. In B6/129 F1 mice, NAC significantly decreased the proliferating cell nuclear antigen in lung tumors. Both budesonide and NAC inhibited B[a]P-induced forestomach tumors and preneoplastic lesions of the respiratory tract in B6/129 F1 mice. In conclusion, heterozygosity for FHIT affects susceptibility of mice to spontaneous alopecia areata and B[a]P-induced preneoplastic lesions of the uterus and does not alter responsiveness to budesonide and NAC.

Pre-B cell proliferation and lymphoblastic leukemia/high-grade lymphoma in E(mu)-miR155 transgenic mice

MicroRNAs (miRNAs) represent a newly discovered class of posttranscriptional regulatory noncoding small RNAs that bind to targeted mRNAs and either block their translation or initiate their degradation. miRNA profiling of hematopoietic lineages in humans and mice showed that some miRNAs are differentially expressed during hematopoietic development, suggesting a role in hematopoietic cell differentiation. In addition, recent studies suggest the involvement of miRNAs in the initiation and progression of cancer. miR155 and BIC, its host gene, have been reported to accumulate in human B cell lymphomas, especially in diffuse large B cell lymphomas, Hodgkin lymphomas, and certain types of Burkitt lymphomas. Here, we show that E(mu)-mmu-miR155 transgenic mice exhibit initially a preleukemic pre-B cell proliferation evident in spleen and bone marrow, followed by frank B cell malignancy. These findings indicate that the role of miR155 is to induce polyclonal expansion, favoring the capture of secondary genetic changes for full transformation.