Expression of the HMGI(Y) gene in human colorectal cancer

HMGA1 promotes gastric cancer growth and metastasis by transactivating SUZ12 and CCDC43 expression

HMGA1 protein is an architectural transcription factor that has been implicated in the progression of multiple malignant tumors. However, the role of HMGA1 in the growth and metastasis of gastric cancer (GC) has not yet been elucidated. Here, we show that HMGA1 is overexpressed in GC cells and the high expression of HMGA1 was correlated with worse survival in GC patients using a bioinformatics assay. Functionally, HMGA1 affected the EdU incorporation, colony formation, migration and invasion of GC cells by exogenously increasing or decreasing the expression of HMGA1. Mechanistically, HMGA1 directly bound to the SUZ12 and CCDC43 promoter and transactivated its expression in GC cells. Inhibition of SUZ12 and CCDC43 attenuated the proliferation, migration and invasiveness of HMGA1-overexpressing GC cells in vitro. Moreover, both HMGA1 and SUZ12/CCDC43 were highly expressed in cancer cells but not in normal gastric tissues, and their expressions were positively correlated. Finally, a tail vein metastatic assay showed that HMGA1 promoted SUZ12/CCDC43-mediated GC cell metastasis in vivo. Our findings suggest that HMGA1 promotes GC growth and metastasis by transactivating SUZ12 and CCDC43 expression, highlighting HMGA1 as a potential prognostic biomarker in the treatment of GC.

Role of High-mobility Group Protein A Isoforms and Their Clinicopathologic Significance in Primary Retinoblastoma

BACKGROUND

High-mobility group proteins A (HMGA) are more abundant in rapidly dividing and transformed cells. These are a group of proteins regulating tumorigenesis and tumor invasion. Increased expression of HMGA1 and HMGA2 has been reported in various benign and malignant tumors. The aim of the present study was to analyze expression of HMGA1 and HMGA2 proteins in retinoblastoma.

METHODS

Protein expression of HMGA1 and HMGA2 in 80 formalin-fixed retinoblastoma tissues was performed by immunohistochemistry, and their mRNA expressions were analyzed on 40 fresh primary enucleated retinoblastoma samples by semiquantitative reverse transcription polymerase chain reaction. Results were then correlated with clinicopathologic parameters.

RESULTS

Immunohistochemical analysis of HMGA1 and HMGA2 was seen in 56.25% and 58.75% of retinoblastoma cases, respectively. mRNA expressions of HMGA1 and HMGA2 was found to be 57.55% and 62.5%, respectively. The mRNA results correlated well with immunostaining results. Expression of both HMGA1 and HMGA2 was significantly associated with choroidal invasion and poor tumor differentiation.

CONCLUSIONS

HMGA1 and HMGA2 proteins may contribute to tumorigenesis of Rb. Expression of HMGA1 and HMGA2 predicts poor prognosis and could serve as a therapeutic target in the management of RB. Further experiments are needed to determine the role of these proteins as therapeutic targets in tumorigenesis.

Clinicopathological and prognostic significance of HMGA2 overexpression in gastric cancer: a meta-analysis

Background

High mobility group protein A2 (HMGA2) overexpression has been reported to be closely related to tumor progression [1-4] and indicate significantly worse overall survival in gastric cancer [5-8]. However, a final consensus regarding this issue has not yet been reached. Thus, we conducted a meta-analysis to evaluate the association between HMGA2 expression and prognosis of gastric cancer patients.

Methods

The Cochrane Library, Embase, PubMed, Web of Science and China Biology Medicine databases were searched to identify eligible literature published prior to September 2016. In the included studies, the level of HMGA2 amplification was evaluated by immunohistochemistry. We performed a meta-analysis, and pooled relative risk (RRs), hazard ratio (HRs), and 95% confidence intervals (CIs) were analyzed using Review Manager 5.3.

Results

Six studies [5-7, 9-11] involving 712 gastric cancer patients were included and stratified by HMGA2 amplification magnitude. The results of the analysis indicated that higher HMGA2 levels were associated with several clinicopathological parameters and predicted poor prognosis in terms of overall survival (OS).

Conclusions

The results of the present study indicate that higher HMGA2 levels were significantly associated with TNM stage, lymph node status, vascular invasion, and poor OS in patients with gastric cancer. In conclusion, HMGA2 may serve as a promising prognostic biomarker in gastric cancer.

The High Mobility Group A1 (HMGA1) Transcriptome in Cancer and Development

BACKGROUND & OBJECTIVES

Chromatin structure is the single most important feature that distinguishes a cancer cell from a normal cell histologically. Chromatin remodeling proteins regulate chromatin structure and high mobility group A (HMGA1) proteins are among the most abundant, nonhistone chromatin remodeling proteins found in cancer cells. These proteins include HMGA1a/HMGA1b isoforms, which result from alternatively spliced mRNA. The HMGA1 gene is overexpressed in cancer and high levels portend a poor prognosis in diverse tumors. HMGA1 is also highly expressed during embryogenesis and postnatally in adult stem cells. Overexpression of HMGA1 drives neoplastic transformation in cultured cells, while inhibiting HMGA1 blocks oncogenic and cancer stem cell properties. Hmga1 transgenic mice succumb to aggressive tumors, demonstrating that dysregulated expression of HMGA1 causes cancer in vivo. HMGA1 is also required for reprogramming somatic cells into induced pluripotent stem cells. HMGA1 proteins function as ancillary transcription factors that bend chromatin and recruit other transcription factors to DNA. They induce oncogenic transformation by activating or repressing specific genes involved in this process and an HMGA1 "transcriptome" is emerging. Although prior studies reveal potent oncogenic properties of HMGA1, we are only beginning to understand the molecular mechanisms through which HMGA1 functions. In this review, we summarize the list of putative downstream transcriptional targets regulated by HMGA1. We also briefly discuss studies linking HMGA1 to Alzheimer's disease and type-2 diabetes.

CONCLUSION

Further elucidation of HMGA1 function should lead to novel therapeutic strategies for cancer and possibly for other diseases associated with aberrant HMGA1 expression.

The Wnt/β-catenin/T-cell factor 4 pathway up-regulates high-mobility group A1 expression in colon cancer

High-mobility group A1 (HMGA1) encodes proteins that act as mediators in viral integration, modification of chromatin structure, neoplastic transformation and metastatic progression. Because HMGA1 is overexpressed in most cancers and has transcriptional relationships with several Wnt-responsive genes, we explored the involvement of HMGA1 in Wnt/β-catenin/TCF-4 signalling. In adenomatous polyposis coli (APC(Min/+)) mice, we observed significant up-regulation of HMGA1 mRNA and protein in intestinal tumours when compared with normal intestinal mucosa. Conversely, restoration of Wnt signalling by the zinc induction of wild-type APC resulted in HMGA1 down-regulation in HT-29 cells. Because APC mutations are associated with mobilization of the β-catenin/TCF-4 transcriptional complex and subsequent activation of downstream oncogenic targets, we analyzed the 5'-flanking sequence of HMGA1 for putative TCF-4 binding elements. We identified two regions that specifically bind the β-catenin/TCF-4 complex in vitro and in vivo, identifying HMGA1 as an immediate target of the β-catenin/TCF-4 signalling pathway in colon cancer. Collectively, these findings strongly implicate Wnt/β-catenin/TCF-4 signalling in regulating HMGA1 to further expand the extensive regulatory network affected by Wnt/β-catenin/TCF-4 signalling.

Overexpression of HMGA1 deregulates tumor growth via cdc25A and alters migration/invasion through a cdc25A-independent pathway in medulloblastoma

Overexpression of high mobility group AT-hook 1 (HMGA1) is common in human cancers. Little is known about the mechanisms underlying its deregulation and downstream targets, and information about its clinical and biological significance in medulloblastoma (MB) is lacking. Here, we demonstrated frequent genomic gain at 6p21.33-6p21.31 with copy number increase leading to overexpression of HMGA1 in MB. The overexpression correlated with a high proliferation index and poor prognosis. Moreover, we found that hsa-miR-124a targeted 3'UTR of HMGA1 and negatively modulated the expression in MB cells, indicating that loss/downregulation of hsa-miR-124a reported in our previous study could contribute to the overexpression. Regarding the biological significance of HMGA1, siRNA knockdown and ectopic expression studies revealed the crucial roles of HMGA1 in controlling MB cell growth and migration/invasion through modulation of apoptosis and formation of filopodia and stress fibers, respectively. Furthermore, we identified cdc25A as a target of HMGA1 and showed that physical interaction between HMGA1 and the cdc25A promoter is required for transcriptional upregulation. In clinical samples, HMGA1 and cdc25A were concordantly overexpressed. Functionally, cdc25A is involved in the HMGA1-mediated control of MB cell growth. Finally, netropsin, which competes with HMGA1 in DNA binding, reduced the expression of cdc25A by suppression of its promoter activity and inhibited in vitro and in vivo intracranial MB cell growth. In conclusion, our results delineate the mechanisms underlying the deregulation and reveal the functional significance of HMGA1 in controlling MB cell growth and migration/invasion. Importantly, the results highlight the therapeutic potential of targeting HMGA1 in MB patients.

HMGA1 induces intestinal polyposis in transgenic mice and drives tumor progression and stem cell properties in colon cancer cells

BACKGROUND

Although metastatic colon cancer is a leading cause of cancer death worldwide, the molecular mechanisms that enable colon cancer cells to metastasize remain unclear. Emerging evidence suggests that metastatic cells develop by usurping transcriptional networks from embryonic stem (ES) cells to facilitate an epithelial-mesenchymal transition (EMT), invasion, and metastatic progression. Previous studies identified HMGA1 as a key transcription factor enriched in ES cells, colon cancer, and other aggressive tumors, although its role in these settings is poorly understood.

METHODS/PRINCIPAL FINDINGS

To determine how HMGA1 functions in metastatic colon cancer, we manipulated HMGA1 expression in transgenic mice and colon cancer cells. We discovered that HMGA1 drives proliferative changes, aberrant crypt formation, and intestinal polyposis in transgenic mice. In colon cancer cell lines from poorly differentiated, metastatic tumors, knock-down of HMGA1 blocks anchorage-independent cell growth, migration, invasion, xenograft tumorigenesis and three-dimensional colonosphere formation. Inhibiting HMGA1 expression blocks tumorigenesis at limiting dilutions, consistent with depletion of tumor-initiator cells in the knock-down cells. Knock-down of HMGA1 also inhibits metastatic progression to the liver in vivo. In metastatic colon cancer cells, HMGA1 induces expression of Twist1, a gene involved in embryogenesis, EMT, and tumor progression, while HMGA1 represses E-cadherin, a gene that is down-regulated during EMT and metastatic progression. In addition, HMGA1 is among the most enriched genes in colon cancer compared to normal mucosa.

CONCLUSIONS

Our findings demonstrate for the first time that HMGA1 drives proliferative changes and polyp formation in the intestines of transgenic mice and induces metastatic progression and stem-like properties in colon cancer cells. These findings indicate that HMGA1 is a key regulator, both in metastatic progression and in the maintenance of a stem-like state. Our results also suggest that HMGA1 or downstream pathways could be rational therapeutic targets in metastatic, poorly differentiated colon cancer.

HMGA1 expression in human gliomas and its correlation with tumor proliferation, invasion and angiogenesis

High-mobility group A1 (HMGA1) protein is an architectural transcription factor widely expressed during embryonic development and tumor progression. The purpose of this research was to investigate the expression of HMGA1 in malignant gliomas with different WHO classification and to study the correlation of HMGA1 expression with tumor proliferation, invasion, and angiogenesis. Expression of HMGA1, Ki-67, MMP-9, VEGF-A, and MVD in malignant gliomas and their correlation were studied in 60 samples of different WHO classification by use of immunohistochemistry, and in 27 randomly selected samples by use of real-time quantitative PCR. Immunohistochemistry results showed that nuclear immunostaining of HMGA1 protein was not observed in normal brain tissues but was observed in 96.7% (58 of 60) of malignant gliomas including high (+++) in 15 (25.0%), moderate (++) in 28 (46.7%), and negligible to low (0-+) in 17 (28.3%) samples. Expression of HMGA1 protein was significantly higher in glioblastoma multiforme than in WHO grade II (P = 0.002) and WHO grade III gliomas (P = 0.024). HMGA1 protein expression correlated significantly with expression of Ki-67 (r = 0.530, P = 0.000), MMP-9 (r = 0.508, P = 0.000), VEGF-A (r = 0.316, P = 0.014), and MVD (r = 0.321, P = 0.012), but not with sex (r = 0.087, P = 0.510) and age (r = -0.121, P = 0.358). Real-time quantitative PCR results, also, were indicative of HMGA1 overexpression in glioblastoma multiforme compared with WHO grade II (P = 0.043) and WHO grade III (P = 0.031) gliomas. HMGA1 gene expression correlated significantly with gene expression of Ki-67 (r = 0.429, P = 0.025), MMP-9 (r = 0.443, P = 0.024), and VEGF-A (r = 0.409, P = 0.034). These results indicated that expression of HMGA1 correlates significantly with malignancy, proliferation, invasion, and angiogenesis of gliomas. We conclude that HMGA1 may be a potential biomarker and rational therapeutic target for human tumors.

The different HMGA1 expression of total population of glioblastoma cell line U251 and glioma stem cells isolated from U251

The high-mobility group A1 (HMGA1) protein is a non-histone architectural nuclear factor and participates in diverse biological processes, including gene transcription, embryogenesis, cell cycle regulation, apoptosis, and even neoplastic transformation. In our study, glioma stem cells (GSCs) expressing the surface marker CD133 from human glioblastoma cell line U251 were isolated using MACS column and were analyzed using immunofluorescence and flow cytometry (FCM). The different expression of HMGA1 was detected using real-time RT-PCR and Western blot at transcriptional and translational levels between U251 and isolated GSCs. The results show that GSCs were successfully isolated from U251 and cultured in serum-free medium (SMF). The percentage of GSCs in U251 was 0.32%±0.07%. HMGA1 expression was significantly higher in GSCs than in glioblastoma cells (P<0.05), up to 6.13±0.25-fold and 2.75±0.99-fold at transcriptional and translational levels, respectively. These results indicated HMGA1 is overexpressed in GSCs as compared to glioblastoma cell line U251, which points to the expression of HMGA1 being closely related to malignant proliferation, invasion, and differentiation of tumors from the prospective of tumor stem cells (TSCs). We conclude that HMGA1 may be a potential biomarker and rational therapeutic target for glioblastoma and GSC.

Increased expression of HMGA1 correlates with tumour invasiveness and proliferation in human pituitary adenomas

AIMS

High-mobility group A1 (HMGA1) is highly expressed in various benign and malignant tumours. The development of pituitary adenoma in Hmga1 transgenic mice has been reported. However, no studies have investigated HMGA1 expression and its clinical significance in human pituitary adenomas.

METHODS AND RESULTS

Immunohistochemical expression of HMGA1 was analysed with respect to various clinicopathological factors in 95 pituitary adenomas. Nuclear expression of HMGA1 was observed in 62% of pituitary adenomas, whereas normal adenohypophysial tissues were negative. Although HMGA1 expression was frequently detected in clinically non-functioning adenomas - 90% of silent adrenocorticotropic hormone (ACTH), 76.2% of follicle-stimulating hormone/luteinizing hormone and 100% of null cell adenomas - it was also detected in 48.1% of growth hormone (GH), 60% of mixed GH/prolactin (PRL), 62.5% of PRL, 66.6% of thyroid-stimulating hormone and 37.5% of ACTH adenomas. HMGA1 expression was significantly higher in invasive adenomas or macroadenomas than in non-invasive adenomas or microadenomas (invasive versus non-invasive, P < 0.05; macroadenoma versus microadenoma, P < 0.05). In addition, HMGA1 showed the highest level in grade IV, more aggressive pituitary adenomas, than in grades I, II and III (IV versus I, P = 0.01; IV versus II, P = 0.01; IV versus III, P = 0.07). Furthermore, a significant correlation between HMGA1 expression and MIB-1 labelling index was observed (R = 0.368, P < 0.0002).

CONCLUSIONS

These findings suggest that HMGA1 up-regulation has an important oncogenic role in pituitary tumorigenesis, as well as being a novel molecular marker of tumour proliferation and invasiveness.

Gene expressions of HMGI-C and HMGI(Y) are associated with stage and metastasis in colorectal cancer

PURPOSE

The high mobility group proteins (HMGs) include the HMGI family members HMGI-C and HMGI(Y), whose expressions in adult tissues generally correlate with malignant tumor phenotypes. The aim of this study was to assess the relationship of HMGI-C or HMGI(Y) gene expression and prognosis in colorectal cancer patients.

METHODS

The gene expressions of HMGI-C and HMGI(Y) in 31 paired samples of colorectal tumor and corresponding non-tumor were determined by real-time reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

The expression of HMGI(Y) in a colorectal cancer tumor was associated with Dukes staging (p = 0.044), while, in non-tumor, the expression of this gene was significant with metastasis (p = 0.003). Patients with Dukes stage A and B present high HMGI(Y) expression in non-tumor of colorectal cancer (p = 0.006). However, patients with Dukes stage C and D present high HMGI-C expression in colorectal tumor (p = 0.023). In the non-metastasis group, HMGI(Y) was highly expressed in non-tumor of colorectal cancer. However, in the metastasis group, there was no significant difference between tumor and non-tumor tissues in both HMGI-C and HMGI(Y) gene expressions.

CONCLUSIONS

The HMGI-C and HMGI(Y) quantitations by real-time RT-PCR are associated with Dukes staging and metastasis; hence, the gene expression levels may be useful in clinical practice.

Transcriptional Control of the HumanHigh Mobility Group A1Gene: Basal and Oncogenic Ras-Regulated Expression

Several studies have already shown that the high mobility group A1 (HMGA1) gene is up-regulated in most common types of cancer and immortalized tissue culture cell lines. HMGA1 expression is also much higher during embryonic development than in adult life. The elevated expression of HMGA1 in cancer thus likely occurs through oncofetal transcriptional mechanisms, which to date have not been well characterized. In the present study, we have cloned and functionally analyzed the TATA-less 5'-flanking regulatory region of human HMGA1. We identified two proximal regulatory regions that are important for basal transcription and in which specificity protein 1 (SP1) and activator protein 1 (AP1) transcription factors seem to be the regulating elements. In addition, we showed that the HMGA1 promoter is strongly inducible by oncogenic Ras, via a distal regulatory region. An AP1 site and three SP1-like sites are responsible for this inducible activity. An even more convincing finding for a role of oncogenic Ras in the regulation of HMGA1 in cancers is the discovery that HMGA1 up-regulation in the HCT116 colon cancer cell line is abolished when the mutated Ras allele is removed from these cells. Our data constitute the first extensive study of the regulation of basal and Ras-induced human HMGA1 gene expression and suggest that the elevated expression of HMGA1 in cancer cells requires, among others, a complex cooperation between SP1 family members and AP1 factors by the activation of Ras GTPase signaling.

High mobility group HMGI(Y) protein expression in head and neck squamous cell carcinoma

CONCLUSION

We conclude that increased expression level of the high mobility group I (HMGI(Y)) is closely associated with malignant transformation in head and neck squamous cell carcinomas (HNSCCs), and the measurement of HMGI(Y) levels in HNSCCs may be useful as a prognostic marker.

OBJECTIVES

To investigate whether HMGI overexpression is observed in HNSCCs, and its value as a prognostic marker in HNSCCs.

MATERIALS AND METHODS

HMGI(Y) expression was determined at the protein level by immunohistochemisty using a HMGI(Y)-specific antibody and RT-PCR in 10 surgically resected specimens of non-neoplastic tissue (normal palatal tissue) and 40 HNSCCs. We also evaluated the association of HMGI(Y) overexpression within clinicopathologic parameters, i.e. clinical stage, pathologic grade, status of cervical lymph node metastasis, recurrence rate.

RESULTS

Expression of HMGI(Y) by immunohistochemical staining was observed in 35 of 40 (87.5%) HNSCC samples, whereas normal mucosa and/or the mucosa adjacent to the tumor tissue showed negative or weakly positive staining (p<0.05). Semi-quantification of HMGI(Y) by RT-PCR was 2.98+/-2.24 in cancer and 0.47+/-0.25 in normal tissue (p<0.001). High expression of HMGI(Y) was observed in recurrent cases, compared with non-recurrent cases (p<0.05). However, no significant correlation was observed between the levels of HMGI(Y) expression and other clinical factors such as clinical stage, pathologic grade, and status of cervical lymph node metastasis.

Determination of high mobility group A1 (HMGA1) expression in hepatocellular carcinoma: a potential prognostic marker

Our objective was to investigate the expression of HMGA1 mRNA and protein in hepatocellular carcinoma (HCC) and the correlation between its expression and clinical pathological characteristics and prognosis. HMGA1 expression was determined at both the mRNA level and the protein level in 30 HCC tissues and their corresponding paracancer liver tissues (PCLTs) and 2 normal liver tissues by RT-PCR and IHC. Follow-up study was done on the 30 patients involved in this research. HMGA1 mRNA was detected in nine cases of HCC tissues and two PCLTs, for a positivity rate of 30% and 6.7%, respectively (P < 0.05), whereas no HMGA1 mRNA expression was found in normal liver tissues. Clinicopathological analysis revealed that HMGA1 mRNA expression was significantly correlated with Edmondson's grade (P < 0.05). HMGA1 protein was detected in four HCC tissues by IHC and located mainly in the nuclei; no positive staining was found in PCLTs. Follow-up study showed that HMGA1 mRNA-positive patients had a higher risk of recurrence/metastasis and a shorter survival than negative cases (P < 0.05). Our findings indicate that HMGA1 may be involved in the carcinogenesis and invasiveness of HCC and the determination of HMGA1 can be of great value in predicting the prognosis of patients with HCC.

Nuclear phosphoproteins HMGA and their relationship with chromatin structure and cancer

The structural characteristics of the three nuclear phosphoproteins of the high mobility group A family are outlined and related to their participation in chromatin structure alteration in many biological processes such as gene expression, neoplastic transformation, differentiation, and apoptosis. The elevated expression of these proteins in tumor cells and their post-translational modifications, such as phosphorylation, acetylation and methylation, are discussed and suggested as suitable targets for cancer chemotherapy.

HMGI(Y) gene expression in colorectal cancer: comparison with some histological typing, grading, and clinical staging

We investigated HMGI(Y) gene expression in 81 pairs of frozen samples obtained from colorectal carcinomas and adjacent normal colorectal mucosas and in four samples from colorectal mucosa from patients without neoplastic diseases. In this group, HMGI(Y)-positive/-negative expression was compared with some histological features, grading, and clinical staging of neoplasms investigated to assess its potential role as a prognostic marker for colorectal cancer. Expression of HMGI(Y) gene was found in 51 of 81 cases of colorectal cancers, while, in normal mucosa, expression of this gene was not observed. HMGI(Y) gene expression was associated with more advanced tumors (T3, T4) and metastases to lymph nodes (N1, N2). The most interesting finding was that expression of this gene correlated with distant metastases. HMGI(Y) gene expression was detected in all cases classified as M1 (n = 19, p = 0.0008). We did not find any association between age, gender, tumor localization, histological type and this gene expression.

Expression of the high mobility group proteins HMGI(Y) correlates with malignant progression in Barrett's metaplasia

Expression of the high mobility group proteins HMGI(Y) has been shown to be a marker of malignancy in thyroid and pancreatic lesions and to correlate significantly with malignant progression in the colon. The aim of this study was to determine whether HMGI(Y) expression is associated with malignant progression in Barrett's metaplasia (BM). Immunoperoxidase staining for HMGI(Y) was performed on sections of formalin-fixed paraffin-embedded endoscopic esophageal biopsies from 42 patients with BM. These consisted of 19 biopsies negative for dysplasia (ND), 16 with low-grade dysplasia (LGD)/indeterminate for dysplasia (IND), and 7 with high-grade dysplasia (HGD)/adenocarcinoma (CA). The percentage of positive cells was recorded, and nuclear HMGI(Y) immunoreactivity in >10% of the cells was considered positive. Statistical analysis was performed using Fisher's exact test. Positive HMGI(Y) staining was detected in 2 of 19 (11%) cases ND, 5 of 16 (30%) LGD/IND cases, and 7 of 7 (100%) HGD/CA cases. Biopsies with HGD/CA were significantly more likely to be positive for HMGI(Y) than biopsies ND (P < 0.0001) or with LGD/IND (P = 0.0046). We conclude that HMGI(Y) expression is significantly associated with malignant progression in BM. Additional studies are needed to determine whether BM biopsies that are ND or LGD/IND and positive for HMGI(Y) are more likely to progress to adenocarcinoma.

High-mobility group protein 1(Y): Metastasis-associated or metastasis-inducing?

Metastasis is the major cause of mortality and morbidity for patients with cancer. The high-mobility group protein 1(Y) [HMG-1(Y)] has a role in the transcription of many genes involved at different steps in the metastatic cascade and has been linked with cancer in human and animal models. This may represent a potential therapeutic target for patients. The following review summarizes and critically appraises the evidence for the role of HMG-1(Y) in metastasis.

Expression of HMGI(Y) associated with malignant phenotype of human gastric tissue

AIMS

We evaluated the association between HMGI(Y) expression and the detection of malignant cells by simple reverse transcriptase-polymerase chain reaction (RT-PCR) and correlated the level of HMGI(Y) expression and the clinicopathological data in gastric cancer.

METHODS AND RESULTS

We analysed HMGI(Y) expression in 62 gastric cancer tissues and 28 normal gastric tissues by RT-PCR and immunohistochemical study. HMGI(Y) expression evidenced by RT-PCR was observed in 42 (67.7%) of 62 gastric cancer samples, whereas eight (28.6%) of 28 normal gastric tissues were positive (P = 0.001). In immunohistochemical staining for HMGI(Y), 48 (77.4%) of 62 gastric cancers were positive for HMGI(Y), whereas four (6.5%) of 62 normal gastric mucosae around the tumour were weakly positive, particularly in cells of some hyperplastic glands (P < 0.001). There was no significant correlation between the levels of HMGI(Y) expression and stage, tumour size, histological grade, invasion depth, or lymph node metastasis.

CONCLUSIONS

Our results suggest that HMGI(Y) expression could be associated with malignant phenotype in human gastric tissue, and that HMGI(Y) may contribute to gastric tumorigenesis.

Diagnostic significance of high mobility group I(Y) protein expression in intraductal papillary mucinous tumors of the pancreas

INTRODUCTION

Overexpression of the high mobility group I(Y), [HMGI(Y)], gene/proteins has been demonstrated in many types of human malignancies, suggesting that HMGI(Y) may play a vital role in the oncogenic transformation of cells.

AIMS

To analyze HMGI(Y) expression in intraductal papillary mucinous tumor (IPMT) of the pancreas to verify whether determination of the HMGI(Y) expression level could provide any diagnostic advantages in the pathological diagnosis of IPMT.

METHODOLOGY

Thirty-three different lesions from 25 patients with IPMT, including 20 with mild dysplasia, 7 with moderate dysplasia, and 6 with carcinoma, were analyzed immunohistochemically with use of an HMGI(Y)-specific antibody.

RESULTS

Immunohistochemical analysis revealed that, although no significant immunoreactivity was found in cases of normal pancreatic duct or mild dysplasia, 28.6% (2/7) of moderate dysplasia showed multifocal immunoreactivity with moderate intensity. In contrast, in 50% (3/6) of the cases of carcinoma, intense multifocal or diffuse immunoreactivity occurred, almost equivalent to that observed in cases of duct cell carcinoma, whereas in the remaining 3 cases of carcinoma only a faint focal immunoreactivity occurred. Histologic examination revealed that these HMGI(Y)-positive carcinomas had an invasive growth pattern, whereas the HMGI(Y)-negative carcinomas were either carcinomas in situ or tumors with minimal invasion. Thus, an increased expression level of HMGI(Y) proteins was closely associated with the malignant phenotype in IPMT.

CONCLUSION

On the basis of these findings, we propose that HMGI(Y) proteins could play an important role(s) in a multistage process of carcinogenesis of IPMT and that the HMGI(Y) protein level could serve as a potential diagnostic marker, which may enable the identification of tumor cells with potential to be biologically malignant.

HMGI/Y proteins: flexible regulators of transcription and chromatin structure

The mammalian HMGI/Y (HMGA) non-histone proteins participate in a wide variety of cellular processes including regulation of inducible gene transcription, integration of retroviruses into chromosomes and the induction of neoplastic transformation and promotion of metastatic progression of cancer cells. Recent advances have contributed greatly to our understanding of how the HMGI/Y proteins participate in the molecular mechanisms underlying these biological events. All members of the HMGI/Y family of 'high mobility group' proteins are characterized by the presence of multiple copies of a conserved DNA-binding peptide motif called the 'AT hook' that preferentially binds to the narrow minor groove of stretches of AT-rich sequence. The mammalian HMGI/Y proteins have little, if any, secondary structure in solution but assume distinct conformations when bound to substrates such as DNA or other proteins. Their intrinsic flexibility allows the HMGI/Y proteins to participate in specific protein-DNA and protein-protein interactions that induce both structural changes in chromatin substrates and the formation of stereospecific complexes called 'enhanceosomes' on the promoter/enhancer regions of genes whose transcription they regulate. The formation of such regulatory complexes is characterized by reciprocal inductions of conformational changes in both the HMGI/Y proteins themselves and in their interacting substrates. It may well be that the inherent flexibility of the HMGI/Y proteins, combined with their ability to undergo reversible disordered-to-ordered structural transitions, has been a significant factor in the evolutionary selection of these proteins for their functional role(s) in cells.