T-cell acute lymphoblastic leukemia (T-ALL) is a neoplasia of thymocytes characterized by the rapid accumulation of the precursors of T lymphocytes. HMGA2 (high-mobility group AT-hook 2) gene expression is extremely low in normal adult tissues, but it is overexpressed in many tumors. To identify the biological function of HMGA2, we generated transgenic mice carrying the human HMGA2 gene under control of the VH promoter/Eμ enhancer. Approximately 90% of Eμ-HMGA2 transgenic mice became visibly sick between 4 and 8 months due to the onset and progression of a T-ALL-like disease. Characteristic features included severe alopecia (30% of mice); enlarged lymph nodes and spleen; and profound immunological abnormalities (altered cytokine levels, hypoimmunoglobulinemia) leading to reduced immune responsiveness. Immunophenotyping showed accumulation of CD5+CD4+, CD5+CD8+ or CD5+CD8+CD4+ T-cell populations in the spleens and bone marrow of sick animals. These findings show that HMGA2-driven leukemia in mice closely resembles spontaneous human T-ALL, indicating that HMGA2 transgenic mice should serve as an important model for investigating basic mechanisms and potential new therapies of relevance to human T-ALL.

The transient build-up of DNA supercoiling during the translocation of replication forks threatens genome stability and is controlled by DNA topoisomerases (TOPs). This crucial process has been exploited with TOP poisons for cancer chemotherapy. However, pinpointing cellular determinants of the best clinical response to TOP poisons still remains enigmatic. Here, we present an integrated approach and demonstrate that endogenous and exogenous expression of the oncofetal high-mobility group AT-hook 2 (HMGA2) protein exhibited broad protection against the formation of hydroxyurea-induced DNA breaks in various cancer cells, thus corroborating our previously proposed model in which HMGA2 functions as a replication fork chaperone that forms a protective DNA scaffold at or close to stalled replication forks. We now further demonstrate that high levels of HMGA2 also protected cancer cells against DNA breaks triggered by the clinically important TOP1 poison irinotecan. This protection is most likely due to the recently identified DNA supercoil constraining function of HMGA2 in combination with exclusion of TOP1 from binding to supercoiled substrate DNA. In contrast, low to moderate HMGA2 protein levels surprisingly potentiated the formation of irinotecan-induced genotoxic covalent TOP1-DNA cleavage complexes. Our data from cell-based and several in vitro assays indicate that, mechanistically, this potentiating role involves enhanced drug-target interactions mediated by HMGA2 in ternary complexes with supercoiled DNA. Subtelomeric regions were found to be extraordinarily vulnerable to these genotoxic challenges induced by TOP1 poisoning, pointing at strong DNA topological barriers located at human telomeres. These findings were corroborated by an increased irinotecan sensitivity of patient-derived xenografts of colorectal cancers exhibiting low to moderate HMGA2 levels. Collectively, we uncovered a therapeutically important control mechanism of transient changes in chromosomal DNA topology that ultimately leads to enhanced human subtelomere stability.

The high mobility group A2 (HMGA2; also called HMGI-C) gene is an architectural transcription factor that belonging to the high mobility group AT-hook (HMGA) gene family. HMGA2 is aberrantly regulated in several human tumors. Over-expression of HMGA2 is correlated with a higher risk of metastasis and an unfavorable prognosis in patients with cancer. We performed a meta-analysis to determine the clinic-pathological and prognostic value of HMGA2 overexpression in different human tumors. A comprehensive literature search was performed using PubMed, Embase, Cochrane Library, Scopus, MEDLINE, Google Scholar and ISI Web of Science. Hazard ratios (HRs)/odds ratios (ORs) and their 95% confidence intervals (CIs) were used to assess the strength of the association between HMGA2 expression and overall survival (OS)/progression free survival (PFS)/disease free survival (DFS). A total of 5319 patients with 19 different types of cancer from 35 articles were evaluated. Pooled data analysis indicated that increased HMGA2 expression in cancer patients predicted a poor OS (HR = 1.70; 95% CI = 1.6-1.81; P < 0.001; fixed-effect model). In subgroup analyses, high HMGA2 expression was particularly associated with poor OS in individuals with gastrointestinal (GI) cancer (HR = 1.89, 95% CI: 1.83-1.96; fixed-effect model) and HNSCC cancer (HR-1.78, 95%CI: 1.44-2.21; fixed-effect model). Over-expression of HMGA2 was associated with vascular invasion (OR = 0.16, 95% CI = 0.05-0.49; P = 0.001) and lymphatic invasion (OR = 1.89, 95% CI = 1.06-3.38; P = 0.032). Further studies should be conducted to validate the prognostic value of HMGA2 for patients with GI cancers.

Hmga2 protein, a transcription factor involved in chromatin architecture, is expressed chiefly during development, where it has many key biological functions. When expressed in adult tissues from in various organs, Hmga2 is always related to cancer development. The role of Hmga2 in skin tumorigenesis is, however, not yet understood. We demonstrated that Hmga2 can be found in non-transformed epidermis, specifically located to the membrane of keratinocytes (KCs) in epidermis. Ex vivo culture of KCs and development of skin carcinomas in DMBA and TPA mouse models was associated with translocation of the Hmga2 protein from the membrane into the nucleus, where Hmga2 induced its own expression by binding to the Hmga2 promoter. Panobinostat, an HDAC inhibitor, downregulated Hmga2 expression by preventing Hmga2 to bind its own promoter, and thus inhibiting Hmga2 promoter activity. Hmga2 translocation to the nucleus could in part be prevented by an inhibitor for ROCK1. Our findings demonstrate that upon program of benign papilloma to malignant cSCC of skin tumorigenesis, Hmga2 translocates in a ROCK-dependent manner from the membrane to the nucleus, where it serves as an autoregulatory transcription factor, causing cell transformation.

We describe two cases of extraskeletal osteochondroma in which chromosome bands 12q14~15 were visibly rearranged through a pericentric inv(12). Molecular analysis of the first tumor showed that both transcript 1 (NM_003483) and transcript 2 (NM_003484) of HMGA2 were expressed. In the second tumor, the inv(12) detected by karyotyping had resulted in an HMGA2-SOX5 fusion transcript in which exons 1-3 of HMGA2 were fused with a sequence from intron 1 of SOX5. The observed pattern is similar to rearrangements of HMGA2 found in several other benign mesenchymal tumors, i.e., disruption of the HMGA2 locus leaves intact exons 1-3 which encode the AT-hook domains and separates them from the 3'-terminal part of the gene. Our data therefore show that a subset of soft tissue osteochondromas shares pathogenetic involvement of HMGA2 with lipomas, leiomyomas and other benign connective tissue neoplasms.

The high mobility group AT‑hook 2 (HMGA2) protein has been found to be upregulated in the majority of tumor types and is associated with a poor prognosis. Previous studies have suggested the oncogenic role of HMGA2 in gallbladder cancer (GBC). The present study aimed to investigate the effects of HMGA2 on the invasion, migration and angiogenesis of GBC cells. To achieve this aim, HMGA2 was overexpressed or silenced in the GBC cell line, EH‑GB1, and then the proliferation, migration, invasion and epithelial‑mesenchymal transition (EMT) abilities of EH‑GB1 cells were investigated using Cell Counting Kit‑8, wound healing, Transwell and western blotting assays. In addition, the expression levels of VEGFA were determined in EH‑GB1 cells using western blotting and reverse transcription‑quantitative PCR following HMGA2 overexpression or silencing. Furthermore, HMGA2‑silenced EH‑GB1 cells were transfected with VEGFA overexpression plasmids to evaluate the tube formation ability of HUVECs using tube formation assay. The results demonstrated that HMGA2 silencing inhibited GBC cell proliferation, migration, invasion and EMT, as evidenced by the downregulated expression of Ki67, proliferating cell nuclear antigen, MMP2, MMP9, N‑cadherin, snail family transcriptional repressor 2 and zinc finger E‑box‑binding homeobox 1, and attenuated cell migration and invasion. However, the opposite results were obtained following HMGA2 overexpression. Moreover, HMGA2 knockdown and overexpression downregulated and upregulated VEGFA expression, respectively. In addition, the tube formation ability of HUVECs and the expression levels of CD31, VEGFR1 and VEGFR2 were downregulated following HMGA2 silencing. However, these effects were partially rescued by simultaneous VEGFA overexpression. In conclusion, the findings of the present study revealed that HMGA2 may promote GBC cell migration, invasion, EMT and angiogenesis. Therefore, inhibiting HMGA2 expression could be considered as a possible therapeutic approach for GBC.

Background: Natural antisense long non-coding RNAs (lncRNAs) are regulatory RNAs transcribed from the opposite strand of either protein coding or non-coding genes, able to modulate their own sense gene expression. Hence, their dysregulation can lead to pathologic processes. Cancer is a complex class of diseases determined by the aberrant expression of a variety of factors, among them, the oncofetal chromatin architectural proteins High Mobility Group A (HMGA) modulate several cancer hallmarks. Thus, we decided to investigate the presence of natural antisense lncRNAs in HMGA1 and HMGA2 loci, and their possible involvement in gene expression regulation. Methods: We used FANTOM5 data resources, FANTOM-CAT genome browser and Zenbu visualization tool, which employ 1,829 human CAGE and RNA-sequencing libraries, to determine expression, ontology enrichment, and dynamic regulation of natural antisense lncRNAs in HMGA1 and HMGA2 loci. We then performed qRT-PCR in different cancer cell lines to validate the existence of HMGA2-AS1 transcripts. We depleted HMGA2-AS1 transcripts with siRNAs and investigated HMGA2 expression by qRT-PCR and western blot analyses. Moreover, we evaluated cell viability and migration by MTS and transwell assays, and EMT markers by qRT-PCR and immunofluorescence. Furthermore, we used bioinformatics approaches to evaluate HMGA2 and HMGA2-AS1 correlation and overall survival in tumor patients. Results: We found the presence of a promoter-associated lncRNA (CATG00000088127.1) in the HMGA1 gene and three antisense genes (RPSAP52, HMGA2-AS1, and RP11-366L20.3) in the HMGA2 gene. We studied the uncharacterized HMGA2-AS1 transcripts, validating their existence in cancer cell lines and observing a positive correlation between HMGA2 and HMGA2-AS1 expression in a cancer-derived patient dataset. We showed that HMGA2-AS1 transcripts positively modulate HMGA2 expression and migration properties of PANC1 cells through HMGA2. In addition, Kaplan-Meier analysis showed that high level of HMGA2-AS1 is a negative prognostic factor in pancreatic cancer patients. Conclusions: Our results describe novel antisense lncRNAs associated with HMGA1 and HMGA2 genes. In particular, we demonstrate that HMGA2-AS1 is involved in the regulation of its own sense gene expression, mediating tumorigenesis. Thus, we highlight a new layer of complexity in the regulation of HMGA2 expression, providing new potential targets for cancer therapy.

The high mobility group protein 2 (HMGA2) regulates gene expression by binding to AT-rich regions of DNA. Akin to other DNA architectural proteins, HMGA2 is highly expressed in embryonic stem cells during embryogenesis, while its expression is more limited at later stages of development and in adulthood. Importantly, HMGA2 is re-expressed in nearly all human malignancies, where it promotes tumorigenesis by multiple mechanisms. HMGA2 increases cancer cell proliferation by promoting cell cycle entry and inhibition of apoptosis. In addition, HMGA2 influences different DNA repair mechanisms and promotes epithelial-to-mesenchymal transition by activating signaling via the MAPK/ERK, TGFβ/Smad, PI3K/AKT/mTOR, NFkB, and STAT3 pathways. Moreover, HMGA2 supports a cancer stem cell phenotype and renders cancer cells resistant to chemotherapeutic agents. In this review, we discuss these oncogenic roles of HMGA2 in different types of cancers and propose that HMGA2 may be used for cancer diagnostic, prognostic, and therapeutic purposes.

Cell number in the mouse thymus increases steadily during the first two weeks after birth. It then plateaus and begins to decline by seven weeks after birth. The factors governing these dramatic changes in cell production are not well understood. The data herein correlate levels of High mobility group A 2 protein (Hmga2) expression with these temporal changes in thymopoiesis. Hmga2 is expressed at high levels in murine fetal and neonatal early T cell progenitors (ETP), which are the most immature intrathymic precursors, and becomes almost undetectable in these progenitors after 5 weeks of age. Hmga2 expression is critical for the initial, exponential expansion of thymopoiesis, as Hmga2 deficient mice have a deficit of ETPs within days after birth, and total thymocyte number is repressed compared to wild type littermates. Finally, our data raise the possibility that similar events occur in humans, because Hmga2 expression is high in human fetal thymic progenitors and falls in these cells during early infancy.

HMGA2 is an architectonic transcription factor abundantly expressed during embryonic and fetal development and it is associated with the progression of malignant tumors. The protein harbours three basically charged DNA binding domains and an acidic protein binding C-terminal domain. DNA binding induces changes of DNA conformation and hence results in global overall change of gene expression patterns. Recently, using a PCR-based SELEX (Systematic Evolution of Ligands by Exponential Enrichment) procedure two consensus sequences for HMGA2 binding have been identified.

Chronic hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC), and HBV X protein (HBx) serves an essential role in the development of HCC. However, its mechanism remains to be elucidated. The aim of the present study was to investigate the role and mechanism of the HBx protein in the epithelial-mesenchymal transition (EMT) and metastasis of HCC. The HCCLM3 cell line was transfected with a HBx-expressing vector. The effects of HBx overexpression on proliferation, migration, invasion and EMT capacities of the HCCLM3 cell line were evaluated using MTT, migration and invasion assays, and western blotting, respectively. Furthermore, the impact of High mobility group AT-hook 2 (HMGA2) knockdown on HBx-mediated metastasis was investigated in the HCC cell line HCCLM3. The results demonstrated that HBx significantly upregulated HMGA2 expression, and enhanced the proliferation, EMT, invasion and migration in HCC cells. Furthermore, HMGA2 knockdown almost abolished HBx-induced EMT and metastasis in HCC. The results of the present study suggest that HBx promotes the proliferation, EMT, invasion and migration of HCC cells by targeting HMGA2. HMGB2 may serve as a potential therapeutic target for HBV-associated HCC.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that exhibits a high proliferation rate and early metastasis leading to a poor prognosis. HMGA2 is a DNA binding transcriptional regulator implicated in tumorigenesis. Here, we demonstrate that the HMGA2 promoter is demethylated in TNBC tumors, leading to increased expression of HMGA2 at both mRNA and protein levels. Importantly, high HMGA2 levels in TNBC tumors are correlated with poor prognosis. To detail the role of HMGA2 in TNBC development and progression, we studied its effect on core cancer phenotypes. Stable knockdown of HMGA2 in TNBC cells revealed that HMGA2 may support cell proliferation, cell migration and invasion. In addition, HMGA2 knockdown decreased cancer stem cell (CSC) features. Importantly, we found that silencing HMGA2 inhibited NF-kB signaling and lead to decreased expression of the downstream molecules IL-6 and IL-8 and reduced STAT3 pathway activation. Our results demonstrate that HMGA2 supports cancer hallmarks in TNBC and may represent a promising target for TNBC treatment.

Increased vascular permeability facilitates metastasis. Cancer-secreted exosomes are emerging mediators of cancer-host crosstalk. Epstein-Barr virus (EBV), identified as the first human tumor-associated virus, plays a crucial role in metastatic tumors, especially in nasopharyngeal carcinoma (NPC). To date, whether and how exosomes from EBV-infected NPC cells affect vascular permeability remains unclear. Here, we show that exosomes from EBV-positive NPC cells, but not exosomes from EBV-negative NPC cells, destroy endothelial cell tight junction (TJ) proteins, which are natural barriers against metastasis, and promote endothelial-to-mesenchymal transition (EndMT) in endothelial cells. Proteomic analysis revealed that the level of HMGA2 protein was higher in exosomes derived from EBV-positive NPC cells compared with that in exosomes derived from EBV-negative NPC cells. Depletion of HMGA2 in exosomes derived from EBV-positive NPC cells attenuates endothelial cell dysfunction and tumor cell metastasis. In contrast, exosomes from HMGA2 overexpressing EBV-negative NPC cells promoted these processes. Furthermore, we showed that HMGA2 upregulates the expression of Snail, which contributes to TJ proteins reduction and EndMT in endothelial cells. Moreover, the level of HMGA2 in circulating exosomes is significantly higher in NPC patients with metastasis than in those without metastasis and healthy negative controls, and the level of HMGA2 in tumor cells is associated with TJ and EndMT protein expression in endothelial cells. Collectively, our findings suggest exosomal HMGA2 from EBV-positive NPC cells promotes tumor metastasis by targeting multiple endothelial TJ and promoting EndMT, which highlights secreted HMGA2 as a potential therapeutic target and a predictive marker for NPC metastasis.

Lipomas are the most common soft tissue tumors in adults. They often carry chromosome aberrations involving 12q13~15 leading to rearrangements of the HMGA2 gene in 12q14.3, with breakpoints occurring within or outside of the gene. Here, we present eleven lipomas and one osteochondrolipoma with a novel recurrent chromosome aberration, t(12;18)(q14~15;q12~21). Molecular studies on eight of the tumors showed that full-length HMGA2 transcript was expressed in three and a chimeric HMGA2 transcript in five of them. In three lipomas and in the osteochondrolipoma, exons 1-3 of HMGA2 were fused to a sequence of SETBP1 on 18q12.3 or an intragenic sequence from 18q12.3 circa 10 kbp distal to SETBP1. In another lipoma, exons 1-4 of HMGA2 were fused to an intronic sequence of GRIP1 which maps to chromosome band 12q14.3, distal to HMGA2. The ensuing HMGA2 fusion transcripts code for putative proteins which contain amino acid residues of HMGA2 corresponding to exons 1-3 (or exons 1-4 in one case) followed by amino acid residues corresponding to the fused sequences. Thus, the pattern is similar to the rearrangements of HMGA2 found in other lipomas, i.e., disruption of the HMGA2 locus leaves intact exons 1-3 which encode the AT-hooks domains and separates them from the 3'-terminal part of the gene. The fact that the examined osteochondrolipoma had a t(12;18) and a HMGA2-SETBP1 fusion identical to the findings in the much more common ordinary lipomas, underscores the close developmental relationship between the two tumor types.

A group of genes that are highly and specifically expressed in proliferating skeletal myoblasts during myogenesis was identified. Expression of one of these genes, Hmga2, increases coincident with satellite cell activation, and later its expression significantly declines correlating with fusion of myoblasts into myotubes. Hmga2 knockout mice exhibit impaired muscle development and reduced myoblast proliferation, while overexpression of HMGA2 promotes myoblast growth. This perturbation in proliferation can be explained by the finding that HMGA2 directly regulates the RNA-binding protein IGF2BP2. Add-back of IGF2BP2 rescues the phenotype. IGF2BP2 in turn binds to and controls the translation of a set of mRNAs, including c-myc, Sp1, and Igf1r. These data demonstrate that the HMGA2-IGF2BP2 axis functions as a key regulator of satellite cell activation and therefore skeletal muscle development.

Regulator of chromosome condensation 2 (RCC2) is highly involved in the development of tumor malignancies. The underlying mechanisms remain to be elucidated. The present study aimed to explore the role of RCC2 in the development of tumor malignancies and explore the underlying mechanisms in colorectal cancer (CRC). RCC2 expression and survival analysis were performed in human pan-cancer. The results of searching its mRNA expression in The Cancer Genome Atlas (TCGA) database showed that RCC2 was highly expressed in different types of cancer. High RCC2 expression levels were significantly correlated with poor survival outcomes by the Kaplan-Meier analysis in the TCGA database. Immunohistochemistry revealed that RCC2 was higher expressed in 36 CRC tissues than in adjacent normal tissues. Co-immunoprecipitation revealed that RCC2 bound to high mobility group A2 (HMGA2). Ectopic expression of RCC2 promoted cell proliferation, migration and invasion, whereas knockdown of HMGA2 exerted the opposite effects. Collectively, the data provided a novel biomarker of RCC2 in various types of cancer. High RCC2 expression levels were correlated with poor prognosis in different types of cancer. In addition, RCC2 may combine with HMGA2 to promote CRC malignancy.

High Mobility Group AT-hook 2 (HMGA2) is a nonhistone chromatin-binding protein which acts as a transcriptional regulating factor involved in gene transcription. In particular, overexpression of HMGA2 has been demonstrated to associate with neoplastic transformation and tumor progression in Colorectal Cancer (CRC). Thus, HMGA2 is a potential therapeutic target in cancer therapy. Heat Shock Protein 90 (Hsp90) is a chaperone protein required for the stability and function for a number of proteins that promote the growth, mobility, and survival of cancer cells. Moreover, it has shown strong positive connections were observed between Hsp90 inhibitors and CRC, which indicated their potential for use in CRC treatment by using combination of data mining and experimental designs. However, little is known about the effect of Hsp90 inhibition on HMGA2 protein expression in CRC. In this study, we tested the hypothesis that Hsp90 may regulate HMGA2 expression and investigated the relationship between Hsp90 and HMGA2 signaling. The use of the second-generation Hsp90 inhibitor, NVP-AUY922, considerably knocked down HMGA2 expression, and the effects of Hsp90 and HMGA2 knockdown were similar. In addition, Hsp90 knockdown abrogates colocalization of Hsp90 and HMGA2 in CRC cells. Moreover, the suppression of HMGA2 protein expression in response to NVP-AUY922 treatment resulted in ubiquitination and subsequent proteasome-dependant degradation of HMGA2. Furthermore, RNAi-mediated silencing of HMGA2 reduced the survival of CRC cells and increased the sensitivity of these cells to chemotherapy. Finally, we found that the NVP-AUY922-dependent mitigation of HMGA2 signaling occurred also through indirect reactivation of the tumor suppressor microRNA (miRNA), let-7a, or the inhibition of ERK-regulated HMGA2 involved in regulating the growth of CRC cells. Collectively, our studies identify the crucial role for the Hsp90-HMGA2 interaction in maintaining CRC cell survival and migration. These findings have significant implications for inhibition HMGA2-dependent tumorigenesis by clinically available Hsp90 inhibitors.

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma. There are two subtypes, fusion gene-positive RMS (FP-RMS) and fusion gene-negative RMS (FN-RMS), depending on the presence of a fusion gene, either PAX3-FOXO1 or PAX7-FOXO1. These fusion genes are thought to be oncogenic drivers of FP-RMS. By contrast, the underlying mechanism of FN-RMS has not been thoroughly investigated. It has recently been shown that HMGA2 is specifically positive in pathological tissue from FN-RMS, but the role of HMGA2 in FN-RMS remains to be clarified.

The high-mobility-group (HMG) proteins are the most abundant non-histone chromatin-associated proteins. HMG proteins are present at high levels in various undifferentiated tissues during embryonic development and their levels are strongly reduced in the corresponding adult tissues, where they have been implicated in maintaining and activating stem/progenitor cells. Here we deciphered the role of the high-mobility-group AT-hook protein 2 (HMGA2) during lung development by analyzing the lung of Hmga2-deficient mice (Hmga2(-/-)).

Epithelial-to-mesenchymal transition (EMT) is an important event during tumorigenesis. The human high-mobility group A2 (HMGA2) is a chromatin-binding protein, which contains three AT-hook domains that enable its binding to the minor groove of DNA. HMGA2 organizes protein complexes on enhancers of various genes to regulate gene expression and cell differentiation. The HMGA2 protein has been reported to be overexpressed in many types of cancer. It is not known, however, whether HMGA2 regulates EMT in human hepatocellular carcinoma (HCC) cell lines, and the mechanism(s) have not been fully elucidated. In this study, the expression of HMGA2 in five HCC cell lines was examined. The levels of HMGA2 expression among the five HCC cell lines coincided with their invasiveness. The variation in HMGA2 expression significantly correlated with the expression of several putative EMT markers. In addition, assessment of the invasive potential, following transfection with HMGA2-siRNA, demonstrated that the rate of cell migration was significantly reduced, suggesting that HMGA2 may be an important contributor to the invasion of tumor cells and that expression levels of HMGA2 influence the metastatic behavior of HCC cells. To further confirm the conclusion and explore the molecular mechanism through which HMGA2 induces EMT, we found that HMGA2 upregulates the expression of Twist and Snail in HCC cell lines. In conclusion, this present study is the first to show that HMGA2 effectively regulates EMT to induce invasion and metastasis in HCC cells. The function of HMGA2 as an oncoprotein may be associated with several important molecules involved in invasion and metastasis of cancer cells.