The tumor-associated gene HMGIC is expressed in normal and osteoarthritis-affected synovia

HMGA2 promotes cancer metastasis by regulating epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a complex physiological process that transforms polarized epithelial cells into moving mesenchymal cells. Dysfunction of EMT promotes the invasion and metastasis of cancer. The architectural transcription factor high mobility group AT-hook 2 (HMGA2) is highly overexpressed in various types of cancer (e.g., colorectal cancer, liver cancer, breast cancer, uterine leiomyomas) and significantly correlated with poor survival rates. Evidence indicated that HMGA2 overexpression markedly decreased the expression of epithelial marker E-cadherin (CDH1) and increased that of vimentin (VIM), Snail, N-cadherin (CDH2), and zinc finger E-box binding homeobox 1 (ZEB1) by targeting the transforming growth factor beta/SMAD (TGFβ/SMAD), mitogen-activated protein kinase (MAPK), and WNT/beta-catenin (WNT/β-catenin) signaling pathways. Furthermore, a new class of non-coding RNAs (miRNAs, circular RNAs, and long non-coding RNAs) plays an essential role in the process of HMGA2-induced metastasis and invasion of cancer by accelerating the EMT process. In this review, we discuss alterations in the expression of HMGA2 in various types of cancer. Furthermore, we highlight the role of HMGA2-induced EMT in promoting tumor growth, migration, and invasion. More importantly, we discuss extensively the mechanism through which HMGA2 regulates the EMT process and invasion in most cancers, including signaling pathways and the interacting RNA signaling axis. Thus, the elucidation of molecular mechanisms that underlie the effects of HMGA2 on cancer invasion and patient survival by mediating EMT may offer new therapeutic methods for preventing cancer progression.

Clinical and Radiologic Characteristics, Surgical Outcomes, and Its Possible Origins of Chondroma of the Dural Convexity

Chondroma of the dural convexity (CDC) is a benign and extremely rare type of intracranial chondroma. In this study, we reported five CDCs in a single center and reviewed the available literature to determine the clinical characteristics and surgical outcomes and possible origins of the disease. The clinical data of five patients (4 females) who confirmed to be CDC between 2000 and 2019 in our single center was collected together with 22 cases from literatures. The clinical characteristics and surgical outcomes were reviewed and analyzed. Among all the available CDC cases, the mean age was 31 ± 13.7 years; the mean tumor volume was 42.3 ± 40.9 cm³, showing a female predominance (63% vs. 37%). The tumors showed calcification in 88.2% cases (15/17) on CT scans and hypointense on T1WI (15/19, 78.9%), mixed intense on T2WI (10/18, 55.6%), and inhomogeneous enhancement without dural tail sign after administration of gadolinium (20/21, 95.2%). Almost all the tumors were misdiagnosed as meningiomas preoperatively. In addition, almost all image available CDC lesions (24/25, 96%) located across the cranial sutures indicating that the tumor originated from ectopic chondrocytes from adjacent skull sutures. No tumors recurred after total resection in follow-up. CDCs are characterized with female predominance and may originate from ectopic chondrocytes from adjacent skull sutures. The lesion with inhomogeneous contrast enhancement without dural tail sign and avascular in cerebral angiography are key points to be differentiated from meningioma. The most effective treatment is total resection.

High HMGA2 expression without gene rearrangement in meningiomas

High mobility group AT-hook 2 (HMGA2) is a non-histone transcriptional regulator protein. Aberrant expression of the HMGA2 gene (HMGA2) and structural rearrangement at the chromosomal region 12q14 with HMGA2 involvement have been reported in several mesenchymal tumors. We analyzed truncated and full-length HMGA2 expression in 55 cases of meningioma, the most common brain tumor of mesenchymal origin. Fluorescence in situ hybridization and 3'-rapid amplification of cDNA ends were used to investigate the possibility of gene rearrangements. Moreover, the relationship between HMGA2 expression and clinicopathological features was assessed. Compared with normal brain tissues, 95% of the meningioma tissues exhibited increased HMGA2 expression. In 14 cases, the expression of truncated HMGA2 was more than two-fold higher than that of paired full-length HMGA2. Chromosomal translocation involving the chromosomal region 12q14 was undetectable. No significant correlation was found between the Ki-67 labeling index and HMGA2 expression and between the HMGA2 expression and the clinicopathological features. The majority of the meningioma cases displayed increased HMGA2 expression, which was not attributed to the chromosomal rearrangement at the corresponding region. Similar to that in the other mesenchymal tumors, increased HMGA2 expression was not associated with tumor cell proliferation in meningiomas.

Rearrangements involving 12q in myeloproliferative disorders: possible role of HMGA2 and SOCS2 genes

We report two cases of translocation associated with deletion on derivative chromosomes in atypical myeloproliferative disorder (MPD). In a MPD with t(3;12)(q29;q14), the rearrangement targeted the HMGA2 locus at 12q14 and deleted a region of about 1.5 megabases (Mb) at 3q29. In an MPD with t(9;12)(q13 approximately q21;q22) and JAK2 V617F mutation, array comparative genomic hybridization delineated a deletion of about 3 Mb at 9q13 approximately q21 and a deletion of about 2 Mb at 12q22 containing SOCS2. These results show that close examination of translocations in hematopoietic diseases may reveal associated microdeletions. The role of these deletions is discussed.

Deregulation of HMGA2 in an aggressive angiomyxoma with t(11;12)(q23;q15)

Aggressive angiomyxoma is a soft-tissue neoplasm with a predilection for the pelvic and perineal regions and a tendency to recur locally. Cytogenetic data on this tumor type are limited to five cases, three of which showed rearrangement of chromosomal bands 12q13-15. Molecular investigation of two of the tumors identified the HMGA2 gene as the target of the 12q rearrangements. However, the two previously analyzed tumors were different at the molecular level: in one, the rearrangement of 12q13-15 resulted in a fusion product, whereas, in the second case, the breakpoint was telomeric (3') to the HMGA2, leaving the gene intact although expressed in its entire length. To shed more light on the pathobiology of aggressive angiomyxoma and to investigate the molecular mechanisms behind the involvement of the HMGA2 gene in this tumor type (fusion transcript vs deregulated expression), we investigated, cytogenetically and with molecular techniques, one such tumor which presented a t(11;12)(q23;q15) as the sole karyotypic aberration. FISH analyses demonstrated no structural alteration of HMGA2 at the cytogenetic level; however, expression of the full-length gene was detected molecularly.

Constitutional rearrangement of the architectural factor HMGA2: a novel human phenotype including overgrowth and lipomas

Although somatic mutations in a number of genes have been associated with development of human tumors, such as lipomas, relatively few examples exist of germline mutations in these genes. Here we describe an 8-year-old boy who has a de novo pericentric inversion of chromosome 12, with breakpoints at p11.22 and q14.3, and a phenotype including extreme somatic overgrowth, advanced endochondral bone and dental ages, a cerebellar tumor, and multiple lipomas. His chromosomal inversion was found to truncate HMGA2, a gene that encodes an architectural factor involved in the etiology of many benign mesenchymal tumors and that maps to the 12q14.3 breakpoint. Similar truncations of murine Hmga2 in transgenic mice result in somatic overgrowth and, in particular, increased abundance of fat and lipomas, features strikingly similar to those observed in the child. This represents the first report of a constitutional rearrangement affecting HMGA2 and demonstrates the role of this gene in human growth and development. Systematic genetic analysis and clinical studies of this child may offer unique insights into the role of HMGA2 in adipogenesis, osteogenesis, and general growth control.

Differential Expression of HMGA1 and HMGA2 in Dermatofibroma and Dermatofibrosarcoma Protuberans: Potential Diagnostic Applications, and Comparison with Histologic Findings, CD34, and Factor XIIIa Immunoreactivity

The histologic distinction of dermatofibrosarcoma protuberans (DFSP) and dermatofibroma (DF) may be difficult, especially in the case of DF extending into the subcutaneous fat (deep DF). CD34 and Factor XIIIa staining is commonly used in separating DF from DFSP, but is not always helpful. HMGA1 and HMGA2 genes, members of the high mobility group protein family genes, encode proteins that act as architectural transcription factors and are frequently dysregulated in a variety of benign or locally aggressive mesenchymal tumors. In this study, we evaluated the immunoreactivity of HMGA1 and HMGA2 in a series of DF and DFSP to determine the possible utility for these markers in the differential diagnosis of these two entities. Immunohistochemical stains were performed on paraffin-embedded tissues from 22 cases of DF, including 14 cases of deep DF and 14 cases of DFSP, using antibodies against HMGA1 and HMGA2. CD34 and Factor XIIIa immunoreactivity was also evaluated in these lesions and compared with the results of HMGA immunostaining. Immunopositivity for both HMGA1 and HMGA2 was seen in 21of 22 (96%) DFs, but in only 3 (21%) and 1 (7%) of 14 DFSPs, respectively. While 100% of DFSP stained for CD34, 36% of DF also labeled for CD34. The immunoreactivity of HMGA1 and HMGA2 in DF was generally strong and diffuse, in contrast to weak and focal staining seen in DFSP. The proportion of cases with positive immunoreactivity for both markers was significantly higher in DF and in deep DF than in DFSP (P < 0.001). We conclude that HMGA1 and HMGA2 expression can be used to distinguish DF from DFSP with a degree of accuracy that is fully equivalent to that of Factor XIIIa and CD34.

Dysregulation and overexpression ofHMGA2in myelofibrosis with myeloid metaplasia

Among cytogenetic studies of patients affected with myelofibrosis with myeloid metaplasia (MMM), a rare chronic myeloproliferative disorder, we found several reports of structural abnormalities of the long arm of chromosome 12. Two MMM patients had a balanced translocation involving 12q: t(4;12)(q32;q15) and t(5;12)(p14;q15), respectively. FISH (fluorescence in situ hybridization) analysis showed that BAC (bacterial artificial chromosome) RP11-366L20 overlaps the breakpoint in both cases. A gene, HMGA2, most of which is included in that BAC, thus was identified as a potential candidate. Using reserves transcriptase-polymerase chain reaction (RT-PCR), we looked for expression of HMGA2 in blood mononuclear cells from these 2 patients and demonstrated a transcript in both. Moreover, we found the gene expressed in the hematopoietic cells of 10 of 10 additional patients bearing no 12q anomalies. HMGA2, not expressed in normal subjects, is implicated in benign solid tumors such as lipomas, leiomyomas, and other rare tumors of mesenchymal origin. We postulate that its dysregulation and overexpression in myeloid progenitors contribute also to the pathogenesis of MMM.

HMGIC alterations in smooth muscle tumors of soft tissues and other sites

The HMGIC gene, which codes a protein that acts as an architectural transcription factor, is frequently rearranged in a variety of benign or locally aggressive mesenchymal tumors. In tumors of smooth muscle differentiation, only uterine leiomyoma and lipoleiomyoma are known to be associated with the altered HMGIC. We investigated molecular and genetic alterations of the HMGIC in 36 benign and malignant smooth muscle tumors arising at various anatomical sites, including 13 uterine leiomyomas, two leiomyomas of the kidney with a t(12;14), one pelvic lipoleiomyoma, one vascular leiomyoma of the foot, two uterine leiomyosarcomas, six retroperitoneal leiomyosarcomas, one leiomyosarcoma of the urinary bladder, and 10 leiomyosarcomas of external soft tissues. HMGIC gene expressions were detected in both uterine (73.3%) and extrauterine (57.1%) smooth muscle tumors by reverse transcriptase polymerase chain reaction (RT-PCR), and benign tumors (70.5%) more frequently expressed the HMGIC than leiomyo-sarcomas (57.8%). Variant transcripts of the HMGIC containing cryptic exonic sequences previously described were found in one renal and three uterine leiomyomas and four leiomyosarcomas arising in the uterus and soft tissues by RT-PCR. Southern blot analysis identified a rearranged HMGIC in one soft tissue leiomyosarcoma. Thus, the HMGIC alterations in smooth muscle tumors are not confined only to uterine leiomyoma or lipoleiomyoma. Our data expand the variety of mesenchymal tumors associated with HMGIC alterations.