The complex CBX7-PRMT1 has a critical role in regulating E-cadherin gene expression and cell migration

The Chromobox protein homolog 7 (CBX7) belongs to the Polycomb Group (PcG) family, and, as part of the Polycomb repressive complex (PRC1), contributes to maintain transcriptional gene repression. Loss of CBX7 expression has been reported in several human malignant neoplasias, where it often correlates with an advanced cancer state and poor survival, proposing CBX7 as a candidate tumor-suppressor gene in cancer progression. Indeed, CBX7 is able to positively or negatively regulate the expression of genes involved in cell proliferation and cancer progression, such as E-cadherin, cyclin E, osteopontin, EGR1. To understand the molecular mechanisms that underlie the involvement of CBX7 in cancer progression, we designed a functional proteomic experiment based on CHIP-MS to identify novel CBX7 protein partners. Among the identified CBX7-interacting proteins we focused our attention on the Protein Arginine Methyltransferase 1 (PRMT1) whose critical role in epithelial-mesenchymal transition (EMT), cancer cell migration and invasion has been already reported. We confirmed the interaction between CBX7 and PRMT1 and demonstrated that this interaction is crucial for PRMT1 enzymatic activity both in vitro and in vivo and for the regulation of E-cadherin expression, an important hallmark of EMT. These results suggest a general mechanism by which CBX7 interacting with histone modification enzymes like HDAC2 and PRMT1 enhances E-cadherin expression. Therefore, disruption of this equilibrium may induce impairment of E-cadherin expression and increased cell migration eventually leading to EMT and, then, cancer progression

miR-155 is positively regulated by CBX7 in mouse embryonic fibroblasts and colon carcinomas, and targets the KRAS oncogene

Background: Loss of CBX7 expression has been described in several malignant neoplasias, including human colon and thyroid carcinomas proposing CBX7 as a tumor suppressor gene with a key role in cancer progression. This role is supported from the development of benign and malignant neoplasias in Cbx7 null mice. The aim of our work has been to investigate the mechanisms underlying the CBX7 oncosuppressor activity by analyzing the microRNAs (miRNAs) regulated by CBX7. Methods: The miRNA expression profiles of the mouse embryonic fibroblasts (MEFs) null for Cbx7 and the wild-type counterpart were analyzed by the miRNACHIP microarray and then validated by qRT-PCR. To asses KRAS as target of miR-155 we evaluated the protein levels after transfection of the synthetic miR-155. Human colon carcinoma samples have been investigated for the expression of CBX7 and miR-155. Results: Twenty miRNAs were found upregulated and nine, including miR-155, downregulated in cbx7-null MEFS in comparison with the wild-type ones. Then, we focused on miR-155 since several studies have shown its deregulated expression in several human malignancies and, moreover, was the most downregulated miRNA. Subsequently, we searched for miR-155 target genes demonstrating that KRAS protein levels are directly modulated by miR-155. A direct significant correlation (r = 0.6779) between CBX7 and miR-155 expression levels was found in a set of human colon carcinoma tissue samples. Conclusion: miR-155 is positively regulated by CBX7 in MEFs and colon carcinomas, and has KRAS as one of the target genes likely accounting for the anti-apoptotic activity ascribed to miR-155 in some tissue contexts

HMGA1 overexpression is associated with a particular subset of human breast carcinomas

Breast cancer represents the second leading cause of cancer mortality among American women and accounts for more than 40 000 deaths annually. High-mobility group A1 (HMGA1) expression has been implicated in the pathogenesis and progression of human malignant tumours, including breast carcinomas. The aim of this study was to evaluate HMGA1 detection as an indicator for the diagnosis and prognosis of human breast carcinoma

The cl2/dro1/ccdc80 null mice develop thyroid and ovarian neoplasias

We have previously reported that the expression of the CL2/CCDC80 gene is downregulated in human papillary thyroid carcinomas, particularly in follicular variants. We have also reported that the restoration of CL2/CCDC80 expression reverted the malignant phenotype of thyroid carcinoma cell lines and that CL2/CCDC80 positively regulated E-cadherin expression, an ability that likely accounts for the role of the CL2/CCDC80 gene in thyroid cancer progression. In order to validate the tumour suppressor role of the CL2/CCDC80 gene in thyroid carcinogenesis we generated cl2/ccdc80 knock-out mice. We found that embryonic fibroblasts from cl2/ccdc80(-/-) mice showed higher proliferation rate and lower susceptibility to apoptosis. Furthermore, cl2/ccdc80(-/-) mice developed thyroid adenomas and ovarian carcinomas. Finally, ret/PTC1 transgenic mice crossed with the cl2/ccdc80 knock-out mice developed more aggressive thyroid carcinomas compared with those observed in the single ret/PTC1 transgenic mice. Together, these results indicate CL2/CCDC80 as a putative tumour suppressor gene in human thyroid carcinogenesis

PATZ1 acts as a tumor suppressor in thyroid cancer via targeting p53-dependent genes involved in EMT and cell migration

PATZ1, a POZ-Zinc finger protein, is emerging as an important regulator of development and cancer, but its cancer-related function as oncogene or tumor-suppressor is still debated. Here, we investigated its possible role in thyroid carcinogenesis. We demonstrated PATZ1 is down-regulated in thyroid carcinomas compared to normal thyroid tissues, with an inverse correlation to the degree of cell differentiation. In fact, PATZ1 expression was significantly further down-regulated in poorly differentiated and anaplastic thyroid cancers compared to the papillary histotype, and it resulted increasingly delocalized from the nucleus to the cytoplasm proceeding from differentiated to undifferentiated thyroid carcinomas. Restoration of PATZ1 expression in three thyroid cancer-derived cell lines, all characterized by fully dedifferentiated cells, significantly inhibited their malignant behaviors, including in vitro proliferation, anchorage-independent growth, migration and invasion, as well as in vivo tumor growth. Consistent with recent studies showing a role for PATZ1 in the p53 pathway, we showed that ectopic expression of PATZ1 in thyroid cancer cells activates p53-dependent pathways opposing epithelial-mesenchymal transition and cell migration to prevent invasiveness. These results provide insights into a potential tumor-suppressor role of PATZ1 in thyroid cancer progression, and thus may have potential clinical relevance for the prognosis and therapy of thyroid cancer

Identification of genes regulated by CBX7 protein and characterization of the transcriptional regulation mechanism of the SPP1 gene

CBX7 is a member of the Polycomb Repressive Complex 1 (PRC1) involved in the process of human and mouse tumorigenesis. Recently, we have demonstrated that CBX7 is drastically decreased in several human carcinomas and that CBX7 protein levels progressively decreased in relation with the malignant grade and the neoplastic stage. To characterize the mechanisms by which the loss of CBX7 contributes to the process of carcinogenesis, we analyzed the gene expression profiling of an anaplastic thyroid carcinoma cell line in which the expression of CBX7 was restored and found that CBX7 was able to negatively or positively regulate the expression of several genes (such as SPP1, SPINK1, STEAP1, and FOS, FOSB, EGR1, respectively) associated with cancer progression. By quantitative (q)RT-PCR, we confirmed these data in mouse and rat system in which the expression of Cbx7 was silenced. Then, we showed that CBX7 was able to physically interact with the promoter region of these genes, thus regulating their activity. qRT-PCR analysis performed on thyroid and lung carcinoma samples with different degree of malignancy, showed a negative correlation between CBX7 and its down-regulated genes, while a positive correlation was observed between CBX7 and its up-regulated genes. Recently, we have demonstrated that CBX7 protein is able to interact with the High Mobility Group A 1 (HMGA1) protein. Therefore, we asked whether this interaction could be involved in the transcriptional regulation of the SPP1 gene.qRT-PCR analysis demonstrated that HMGA1 protein is able to increase the SPP1 expression in several cellular systems. Moreover, by chromatin immunoprecipitation assays, we found that HMGA1 binds together with CBX7 protein to the SPP1 promoter and that the two proteins compete for the binding. Finally, functional assays showed that CBX7 is able to negatively regulate cellular migration by repressing transcriptional activation of the SPP1promoter. In conclusion, the loss of CBX7 expression might play a critical role in cancer progression by deregulating the expression of specific effector genes

High mobility group a proteins as tumor markers

Almost 30 years ago, overexpression of HMGA proteins was associated with malignant phenotype of rat thyroid cells transformed with murine retroviruses. Thereafter, several studies have analyzed HMGA expression in a wide range of human neoplasias. Here, we summarize all these results that, in the large majority of the cases, confirm the association of HMGA overexpression with high malignant phenotype as outlined by chemoresistance, spreading of metastases, and a global poor survival. Even though HMGA proteins' overexpression indicates a poor prognosis in almost all malignancies, their detection may be particularly useful in determining the prognosis of breast, lung, and colon carcinomas, suggesting for the treatment a more aggressive therapy. In particular, the expression of HMGA2 in lung carcinomas is frequently associated with the presence of metastases. Moreover, recent data revealed that often the cause for the high HMGA proteins levels detected in human malignancies is a deregulated expression of non-coding RNA. Therefore, the HMGA proteins represent tumor markers whose detection can be a valid tool for the diagnosis and prognosis of neoplastic diseases

CBX7 Expression in Oncocytic Thyroid Neoplastic Lesions (Hürthle Cell Adenomas and Carcinomas)

Previous analysis of CBX7 expression in a large number of thyroid adenoma and carcinoma samples revealed a progressive reduction of CBX7 levels that was well related with the malignant grade of thyroid neoplasias. Hürthle cell tumors are unusual thyroid neoplasms characterized by the presence of particular cells called oncocytes

CBX7 Modulates the Expression of Genes Critical for Cancer Progression

<div><p>Background</p><p>We have previously shown that the expression of CBX7 is drastically decreased in several human carcinomas and that its expression progressively decreases with the appearance of a highly malignant phenotype. The aim of our study has been to investigate the mechanism by which the loss of CBX7 expression may contribute to the emergence of a more malignant phenotype.</p><p>Methods</p><p>We analyzed the gene expression profile of a thyroid carcinoma cell line after the restoration of CBX7 and, then, analyzed the transcriptional regulation of identified genes. Finally, we evaluated the expression of CBX7 and regulated genes in a panel of thyroid and lung carcinomas.</p><p>Results</p><p>We found that CBX7 negatively or positively regulates the expression of several genes (such as SPP1, SPINK1, STEAP1, and FOS, FOSB, EGR1, respectively) associated to cancer progression, by interacting with their promoter regions and modulating their transcriptional activity. Quantitative RT-PCR analyses in human thyroid and lung carcinoma tissues revealed a negative correlation between CBX7 and its down-regulated genes, while a positive correlation was observed with up-regulated genes.</p><p>Conclusion</p><p>In conclusion, the loss of CBX7 expression might play a critical role in advanced stages of carcinogenesis by deregulating the expression of specific effector genes.</p></div

CBX7 and HMGA1b proteins act in opposite way on the regulation of the SPP1 gene expression

Several recent studies have reported the Polycomb Repressive Complex 1 member CBX7 as a tumor-suppressor gene whose expression progressively decreases in different human carcinomas in relation with tumor grade, malignant stage and poor prognosis. We have previously demonstrated that CBX7 is able to inhibit the expression of the SPP1 gene, encoding the chemokine osteopontin that is over-expressed in cancer and has a critical role in cancer progression.Here, we have analyzed the mechanism by which CBX7 regulates the SPP1 gene expression. We show that the SPP1 transcriptional regulation mechanism involves the CBX7-interacting protein HMGA1b, that acts as a positive regulator of the SPP1 gene. In fact, we demonstrate that, in contrast with the transcriptional activity of CBX7, HMGA1b is able to increase the SPP1 expression by inducing the activity of its promoter. Moreover, we show that CBX7 interferes with HMGA1b on the SPP1 promoter and counteracts the positive transcriptional activity of HMGA1b on the SPP1 expression.Furthermore, since we found that also the NF-kappa B complex resulted involved in the modulation of the SPP1 expression in thyroid cells, we suppose that CBX7/HMGA1b/NF-kappa B could take part in the same transcriptional mechanism that finally leads to the regulation of the SPP1 gene expression.Taken together, our data show the important role played by CBX7 in the negative regulation of the SPP1 gene expression, thus contributing to prevent the acquisition of a malignant phenotype.Associazione Italiana per la Ricerca sul Cancro-AIRCMinistero dell'Istruzione, dell'Universita e della Ricerca MIURP.O.R. Campania FSE Progetto CREMeProgetto di Interesse strategico Invecchiamento (PNR-CNR Aging Program) PNR-CNRProgetto Nuove strategie nanotecnologiche per la messa a punto di farmaci e presidi diagnostici diretti verso cellule cancerose circolantiCNR Epigenomics Flagship Project EPIGENCNR Nanomax Progetto Bandiera DESIREDUniv Naples Federico II, Dipartimento Med Mol & Biotecnol Med DMMBM, CNR, Ist Endocrinol & Oncol Sperimentale IEOS G Salvat, I-80131 Naples, ItalyUniv Fed Sao Paulo UNIFESP, Disciplina Genet, Lab Bases Genet Tumores Tiroide, BR-04039032 Sao Paulo, SP, BrazilInst Nacl Canc INCA, BR-20230130 Rio De Janeiro, RJ, BrazilUniv Fed Sao Paulo UNIFESP, Disciplina Genet, Lab Bases Genet Tumores Tiroide, BR-04039032 Sao Paulo, SP, BrazilAssociazione Italiana per la Ricerca sul Cancro-AIRC: IG 11477Progetto Nuove strategie nanotecnologiche per la messa a punto di farmaci e presidi diagnostici diretti verso cellule cancerose circolanti: PON01-02782Web of Scienc