High Mobility Group A1 Gene Research Articles

High Mobility Group A1 Chromatin Remodeling Protein Regulates Self-Renewal, Niche Formation, and Regenerative Function in Adult Stem Cells through Wnt/β-Catenin Signaling

Introduction: Nuclear chromatin structure is a key determinant of stem cell function and cell fate, although factors that regulate this are only beginning to emerge. While High Mobility Group A1(HMGA1) chromatin remodeling proteins are among the most abundant, nonhistone chromatin binding proteins in adult stem cells (ASCs), their role in this setting has been unknown. HMGA1/2 proteins modulate gene expression by binding to DNA, bending chromatin, and recruiting transcription factor complexes to enhancers throughout the genome. The HMGA1 gene is highly expressed during embryogenesis with low or undetectable levels in mature, differentiated tissues. In cancer, HMGA1 re-expression occurs through oncogenic transcription factors, other epigenetic alterations, or in rare cases, chromosomal translocation events. Importantly, HMGA1 levels correlate with adverse clinical outcomes in diverse malignancies. We previously reported that Hmga1 transgenic mice develop leukemic transformation by inducing transcriptional networks involved in stem cell function and cell cycle progression.Methods: To elucidate the role of Hmga1 in normal development and ASCs in vivo, we generated mouse models with transgenic overexpression or deletion of Hmga1. To define the function of Hmga1 in adult stem cells (ASCs), we used gain-of-function (overexpression) and loss-of-function (silencing or genetic deletion) approaches in human and murine intestinal stem cells (ISCs) and hematopoietic stem and progenitor cells.Results:Transgenic mice overexpressing Hmga1 in ISCs develop hyperproliferation, aberrant crypt formation, and polyposis in the intestinal epithelium by expanding the ISC and niche compartments. Hmga1 enhances self-renewal in ISCs by amplifying Wnt/β-catenin signaling, inducing genes that encode both Wnt agonist receptors and downstream Wnt effectors. Surprisingly, Hmga1 also "builds" an epithelial niche by directly up-regulating Sox9 to induce Paneth cell differentiation. Paneth cells constitute the epithelial ISC niche by secreting Wnt agonists. This is the first example of Hmga1 fostering terminal differentiation to establish a stem cell niche. In human intestine, HMGA1 and SOX9 are highly correlated, and both become up-regulated in colorectal cancer.Human CD34+ cells engineered to overexpress Hmga1 expand more efficiently, while those with Hmga1 deficiency have defective proliferation and colony forming capability. Both colony number and size were decreased, and differentiation was skewed towards myeloid lineages. In mice, Hmga1 deletion causes partial embryonic lethality; over 50% of expected offspring die before mid-gestation. Those that survive develop premature aging phenotypes with early kyphosis, decreased bone density, grip strength, gait velocity, and hearing deficits. Knock-out mice also have early thymic aplasia, decreased numbers of early T-cell precursors, as well as decreased B-cell differentiation. Long-term (LT)-hematopoietic stem cells were decreased and preliminary data suggests aberrant regenerative function in serial, competitive transplant experiments.Preliminary ChIP-seq and gene expression studies in CD34+ cells suggest that Hmga1 regulates transcriptional networks involved in Wnt, JAK-STAT, and PI3K signaling.Conclusions:Our results in ASCs reveal a novel role for Hmga1 in tissue homeostasis by inducing pathways involved in Wnt and regenerative function. In ISCs, Hmga1 maintains both the stem cell pool and niche compartment whereas deregulated Hmga1 may perturb this equilibrium during carcinogenesis. Functional studies in HSCs suggest that Hmga1 also regulates self-renewal, regenerative potential, and the capacity for balanced differentiation. These findings indicate that HMGA1 is required for normal stem cell function, both during embryogenesis, and postnatally, in ASCs. Our prior work in tumor models demonstrates that a subset of HMGA1 stem cell pathways are hi-jacked by cancer cells to drive tumor progression. Together, these studies provide compelling rationale for further research to determine how to harness HMGA1 for regenerative medicine and to target it in cancer therapy. DisclosuresNo relevant conflicts of interest to declare.

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

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

ROS-dependent HMGA2 upregulation mediates Cd-induced proliferation in MRC-5 cells

Cadmium (Cd) is a heavy metal widely found in a number of environmental matrices, and the exposure to Cd is increasing nowadays. In this study, the role of high mobility group A2 (HMGA2) in Cd-induced proliferation was investigated in MRC-5 cells. Exposure to Cd (2μM) for 48h significantly enhanced the growth of MRC-5 cells, increased reactive oxygen species (ROS) production, and induced both mRNA and protein expression of HMGA2. Evidence for Cd-induced reduction of the number of G0/G1 phase cells and an increase in the number of cells in S phase and G2/M phase was sought by flow cytometric analysis. Western blot analysis showed that cyclin D1, cyclin B1, and cyclin E were upregulated in Cd-treated cells. Further study revealed that N-acetyl cysteine (NAC) markedly prevented Cd-induced proliferation of MRC-5 cells, ROS generation, and the increasing protein level of HMGA2. Silencing of HMGA2 gene by siRNA blocked Cd-induced cyclin D1, cyclin B1, and cyclin E expression and reduction of the number of G0/G1 phase cells. Combining, our data showed that Cd-induced ROS formation provoked HMGA2 upregulation, caused cell cycle changes, and led to cell proliferation. This suggests that HMGA2 might be an important biomarker in Cd-induced cell proliferation.

Association of ICAM-1 and HMGA1 Gene Variants with Retinopathy in Type 2 Diabetes Mellitus Among Chinese Individuals

ABSTRACTPurpose: To evaluate the association of intercellular cell-adhesion molecule 1 (ICAM-1) and high-mobility group A1 (HMGA1) gene variants with diabetic retinopathy (DR) in a Chinese type 2 diabetes mellitus (T2DM) cohort.Methods: A total of 792 patients with T2DM were enrolled and categorized into two groups: (1) the DR group consisted of 448 patients, which was further subclassified into the proliferative DR (PDR) group with 220 patients and the nonproliferative DR (NPDR) group with 228 patients; (2) the diabetes without retinopathy (DNR) group comprised 344 patients who had no signs of DR. The single-nucleotide polymorphism (SNP) rs5498 in ICAM-1 gene and IVS5-13insC variant in HMGA1 gene were genotyped.Results: No evident association was found in the allele frequencies between SNP rs5498 in ICAM-1 gene and DR patients; the combined p values for the additive, dominant, and recessive models in genotype were greater than 0.05. No significant association was identified between the IVS5-13insC variant in HMGA1 gene and DR individuals.Conclusions: Our results revealed that SNP rs5498 in ICAM-1 gene and IVS5-13insC variant in HMGA1 gene were not associated with the susceptibility of DR in the Chinese T2DM cohort.

A Novel Feed-Forward Loop Involving the High Mobility Group A1 (HMGA1) Chromatin Remodeling Protein and cMYC in Acute Myeloid Leukemia Is Targeted By JQ1

Acute myeloid leukemia (AML) comprises a heterogeneous group of highly lethal, clonal disorders of blood cell progenitors for which more effective therapies are urgently needed. The underlying genetic abnormalities transform hematopoietic progenitors into AML blasts that are resistant to apoptosis and fail to undergo normal differentiation. While conventional chemotherapy regimens frequently ablate actively cycling leukemic blasts and induce remissions, most patients relapse with abysmal outcomes. Recent studies highlight an important role for stem cell transcriptional networks in supporting survival and resistance to chemotherapy in leukemic blasts, although druggable targets that maintain these networks have remained elusive. We previously discovered that the cMYC oncoprotein activates HMGA1 expression in experimental models of lymphoid leukemia, while HMGA1 directly induces cMYC in embryonic stem cells. Here, we demonstrate for the first time that the HMGA1-cMYC network is a therapeutic target that is critical for leukemic cell survival and resistance to chemotherapy.In primary AML blasts, we found that both HMGA1 and cMYC gene expression are enriched relative to levels in normal CD34+ hematopoietic stem and progenitor cells and their expression is positively correlated. Silencing HMGA1 or cMYC in AML blasts dramatically halts cell growth, leading to rapid apoptotic cell death. HMGA1 transcriptionally activates cMYC in leukemic blasts, while the cMYC oncoprotein, in turn, induces HMGA1, resulting in potent feed-forward loop that maintains survival in AML blasts.We also discovered that AML blasts exposed to AraC (cytosine arabinoside), a standard cytotoxic agent used in AML, become resistant by up-regulating both HMGA1 and cMYC. Moreover, silencing either HMGA1 or cMYC restores sensitivity to AraC, demonstrating that induction of HMGA1 and cMYC is functionally important. Next, we sought to determine whether the inhibitor of the BET family of bromodomain proteins, JQ1, has anti-leukemic effects in AML blasts resistant to AraC because it functions, at least in part, by disrupting cMYC transcriptional complexes. We found that cMYC is repressed within 4 hours, while HMGA1 requires 24 hours for down-regulation following exposure to JQ1. Moreover, JQ1 restores sensitivity to AraC in the resistant AML blasts.Together, these studies reveal a novel role for HMGA1 and cMYC in a feed-forward loop that is critical for AML blast survival and chemoresistance. These findings also suggest that JQ1 will be effective therapy in AML blasts that are resistant to AraC. DisclosuresNo relevant conflicts of interest to declare.

The Association between HMGA1 rs146052672 Variant and Type 2 Diabetes: A Transethnic Meta-Analysis.

The high-mobility group A1 (HMGA1) gene has been previously identified as a potential novel candidate gene for susceptibility to insulin resistance and type 2 diabetes (T2D) mellitus. For this reason, several studies have been conducted in recent years examining the association of the HMGA1 gene variant rs146052672 (also designated IVS5-13insC) with T2D. Because of non-univocal data and non-overlapping results among laboratories, we conducted the current meta-analysis with the aim to yield a more precise and reliable conclusion for this association. Using predetermined inclusion criteria, MEDLINE, PubMed, Web of Science, Scopus, Google Scholar and Embase were searched for all relevant available literature published until November 2014. Two of the authors independently evaluated the quality of the included studies and extracted the data. Values from the single studies were combined to determine the meta-analysis pooled estimates. Heterogeneity and publication bias were also examined. Among the articles reviewed, five studies (for a total of 13,789 cases and 13,460 controls) met the predetermined criteria for inclusion in this meta-analysis. The combined adjusted odds ratio estimates revealed that the rs146052672 variant genotype had an overall statistically significant effect on increasing the risk of development of T2D. As most of the study subjects were Caucasian, further studies are needed to establish whether the association of this variant with an increased risk of T2D is generalizable to other populations. Also, in the light of this result, it would appear to be highly desirable that further in-depth investigations should be undertaken to elucidate the biological significance of the HMGA1 rs146052672 variant.

The critical role of HMGA2 in regulation of EMT in epithelial ovarian carcinomas.

The high mobility group A2 (HMGA2), an oncofetal protein, was shown to play a role in tumor development and progression. However, the molecular and clinical role of HMGA2 in epithelial ovarian carcinomas (EOCs) is still unknown. In the present study, EOC cell line SKOV3 was subjected to in vitro assays. Here, our findings showed that HMGA2 was highly expressed in EOC cell line SKOV3. HMGA2 knockdown promoted cell apoptosis and the cleavage of caspase 3, and decreased the B cell lymphoma 2 (Bcl-2)/Bax ratio in SKOV3. Functionally, HMGA2 knockdown resulted in reduction of SKOV3 cell migration and invasion. Mechanically, HMGA2 knockdown affected the occurrence of EMT by increasing E-cadherin gene and protein expression and decreasing the gene and protein expression of N-cadherin, slug, and vimentin. At the same time, HMGA2 also repressed the expression of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9), which was consistent with the decreased invasion capacity. In conclusion, HMGA2 is associated with migration and invasiveness and regulates the progression of EMT in the development of EOC, and HMGA2 gene and protein may be a novel therapeutic target against EOC in the clinical practice.

Dysregulated protease activated receptor 1 (PAR1) promotes metastatic phenotype in breast cancer through HMGA2.

As the majority of patients with basal-like breast carcinoma present with invasive, metastatic disease that do not respond to available therapies, it is essential to identify new therapeutic targets that impact invasion and metastasis. Protease-activated receptor 1 (PAR1), a G-protein coupled receptor has been shown to act as an oncogene, but underlying mechanisms are not well understood. Here, we show that ectopic expression of functionally active PAR1 in MCF-7 cells induced a hormone-refractory, invasive phenotype representative of advanced basal-like breast carcinoma that readily formed metastatic lesions in lungs of mice. PAR1 was found to globally upregulate mesenchymal markers, including vimentin, a direct target of PAR1, and downregulate the epithelial markers including E-cadherin, as well as estrogen receptor. In contrast, non-signaling PAR1 mutant receptor did not lead to an invasive, hormone refractory phenotype. PAR1 expression increased spheroid formation and the level of stemness markers and self-renewal capacity in human breast cancer cells. We identified HMGA2 (high mobility group A2) as an important regulator of PAR1-mediated invasion. Inhibition of PAR1 signaling suppresses HMGA2-driven invasion in breast cancer cells. HMGA2 gene and protein are highly expressed in metastatic breast cancer cells. Overall, our results show that PAR1/HMGA2 pathway may present a novel therapeutic target.

HMGA1 promotes metastatic processes in basal-like breast cancer regulating EMT and stemness

Breast cancer is a heterogeneous disease that progresses to the critical hallmark of metastasis. In the present study, we show that the High Mobility Group A1 (HMGA1) protein plays a fundamental role in this process in basal-like breast cancer subtype. HMGA1 knockdown induces the mesenchymal to epithelial transition and dramatically decreases stemness and self-renewal. Notably, HMGA1 depletion in basal-like breast cancer cell lines reduced migration and invasion in vitro and the formation of metastases in vivo. Mechanistically, HMGA1 activated stemness and key migration-associated genes which were linked to the Wnt/beta-catenin, Notch and Pin1/mutant p53 signalling pathways. Moreover, we identified a specific HMGA1 gene expression signature that was activated in a large subset of human primary breast tumours and was associated with poor prognosis. Taken together, these data provide new insights into the role of HMGA1 in the acquisition of aggressive features in breast cancer.

HMGA2 and high-grade serous ovarian carcinoma.

HMGA2, the High Mobility Group A2 gene, plays a very important role in fetal development and carcinogenesis. As an oncofetal gene, it is upregulated in tumors of both epithelial and mesenchymal tissue origin. Chromosomal translocations of HMGA2 are common in mesenchymal tumors, whereas the regulatory mechanisms of HMGA2 in malignant epithelial tumors are much more complex. As an architectural transcription factor, it is involved in multiple biological pathways by targeting different downstream genes in different cancers. HMGA2 is upregulated in both the early and late stages of high-grade serous ovarian carcinoma (HGSOC) and, according to The Cancer Genomic Atlas, is among a signature of genes overexpressed in ovarian cancer. Recent identification of miR-182 as a mediator of BRCA1 and HMGA2 deregulation in ovarian cancer cells may guide us toward a better understanding of the roles of HMGA2 in ovarian carcinogenesis. In this article, we will review recent developments and findings related to HMGA2, including its regulation, oncogenic properties, major functional pathways associated with the tumorigenesis of HGSOC, and its potential role as a biomarker for clinical application.

Knockdown of HMGA1 inhibits human breast cancer cell growth and metastasis in immunodeficient mice

The high mobility group A1 gene (HMGA1) has been previously implicated in breast carcinogenesis, and is considered an attractive target for therapeutic intervention because its expression is virtually absent in normal adult tissue. Other studies have shown that knockdown of HMGA1 reduces the tumorigenic potential of breast cancer cells in vitro. Therefore, we sought to determine if silencing HMGA1 can affect breast cancer development and metastatic progression in vivo. We silenced HMGA1 expression in the human breast cancer cell line MDA-MB-231 using an RNA interference vector, and observed a significant reduction in anchorage-independent growth and tumorsphere formation, which respectively indicate loss of tumorigenesis and self-renewal ability. Moreover, silencing HMGA1 significantly impaired xenograft growth in immunodeficient mice, and while control cells metastasized extensively to the lungs and lymph nodes, HMGA1-silenced cells generated only a few small metastases. Thus, our results show that interfering with HMGA1 expression reduces the tumorigenic and metastatic potential of breast cancer cells in vivo, and lend further support to investigations into targeting HMGA1 as a potential treatment for breast cancer.

Lack of association of the HMGA1 IVS5-13insC variant with type 2 diabetes in an ethnically diverse hypertensive case control cohort.

BackgroundRecently, the high-mobility group A1 gene (HMGA1) variant IVS5-13insC has been associated with type 2 diabetes, but reported associations are inconsistent and data are lacking in Hispanic and African American populations. We sought to investigate the HMGA1-diabetes association and to characterize IVS5-13insC allele frequencies and linkage disequilibrium (LD) in 3,070 Caucasian, Hispanic, and African American patients from the INternational VErapamil SR-Trandolapril STudy (INVEST).MethodsINVEST was a randomized, multicenter trial comparing two antihypertensive treatment strategies in an ethnically diverse cohort of hypertensive, coronary artery disease patients. Controls, who were diabetes-free throughout the study, and type 2 diabetes cases, either prevalent or incident, were genotyped for IVS5-13insC using Taqman®, confirmed with Pyrosequencing and Sanger sequencing. For LD analysis, genotyping for eight additional HMGA1 single nucleotide polymorphisms (SNPs) was performed using the Illumina® HumanCVD BeadChip. We used logistic regression to test association of the HMGA1 IVS5-13insC and diabetes, adjusted for age, gender, body mass index, and percentage European, African, and Native American ancestry.ResultsWe observed IVS5-13insC minor allele frequencies consistent with previous literature in Caucasians and African Americans (0.03 in cases and 0.04 in controls for both race/ethnic groups), and higher frequencies in Hispanics (0.07 in cases and 0.07 in controls). The IVS5-13insC was not associated with type 2 diabetes overall (odds ratio 0.98 [0.76-1.26], p=0.88) or in any race/ethnic group. Pairwise LD (r2) of IVS5-13insC and rs9394200, a SNP previously used as a tag SNP for IVS5-13insC, was low (r2=0.47 in Caucasians, r2=0.25 in Hispanics, and r2=0.06 in African Americans). Furthermore, in silico analysis suggested a lack of functional consequences for the IVS5-13insC variant.ConclusionsOur results suggest that IVS5-13insC is not a functional variant and not associated with type 2 diabetes in an ethnically diverse, hypertensive, coronary artery disease population. Larger, more adequately powered studies need to be performed to confirm our findings.Trial registrationclinicaltrials.gov (NCT00133692)

Effect of silencing of high mobility group A2 gene on gastric cancer MKN-45 cells

To investigate the effect of high mobility group A2 (HMGA2) gene silencing on gastric cancer MKN-45 cells in vitro. HMGA2 short hairpin RNA (shRNA) expression plasmids were constructed, including a pair of random scrambled sequences. Human gastric cancer cell line MKN-45 cells were divided into three groups: blank control group (non-transfected cells), transfected group (cells transfected with HMGA2 shRNA recombinant plasmid) and scrambled sequence group (transfected with random scrambled plasmid). Cells were transfected with HMGA2 shRNA recombinant plasmids and scrambled plasmid in vitro, and the cells transfection efficiency was assayed by fluorescence microscopy. The HMGA2 messenger RNA (mRNA) expression was detected by reverse transcription polymerase chain reaction, gastric cancer cells apoptosis was detected by flow cytometry, cell proliferation was detected by methyl thiazol tetrazolium, and the protein expression of phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt), P27, caspase-9 and B-cell leukemia/lymphoma-2 (Bcl-2) were analyzed by Western blotting. Compared with the blank control group and the scrambled sequence group, the levels of HMGA2 mRNA and protein expression in the transfected group were significantly reduced (P < 0.05). The relative HMGA2 mRNA expression levels of the blank control group, transfected group and scrambled sequence group were 0.674 ± 0.129, 0.374 ± 0.048 and 0.689 ± 0.124, respectively. The relative HMGA2 protein expression levels of the blank control group, transfected group and scrambled sequence group were 0.554 ± 0.082, 0.113 ± 0.032 and 0.484 ± 0.123, respectively. Moreover, transfection with the scrambled sequence had no effect on the expression of HMGA2. After being transfected with shRNA for 24, 48 and 72 h, the cell apoptotic rates of the transfected group were 21.65% ± 0.28%, 39.98% ± 1.82% and 24.51% ± 0.93%, respectively, which significantly higher than those of blank control group (4.72% ± 1.34%, 5.83% ± 0.13% and 5.22% ± 1.07%) and scrambled sequence group (4.28% ± 1.33%, 7.87% ± 1.43% and 6.71% ± 0.92%). After 24, 48 and 72 h, the cell proliferation inhibition rates in the transfected group were 31.57% ± 1.17%, 39.45% ± 2.07% and 37.56% ± 2.32%, respectively; the most obvious cell proliferation inhibition appeared at 48 h after transfection. Compared with the blank control group and scrambled sequence group, after transfection of shRNA for 72 h, the protein expression levels of PI3K (0.042 ± 0.005 vs 0.069 ± 0.003, 0.067 ± 0.05), Akt (0.248 ± 0.004 vs 0.489 ± 0.006, 0.496 ± 0.104) and Bcl-2 (0.295 ± 0.084 vs 0.592 ± 0.072, 0.594 ± 0.109) were significantly reduced. The protein expression levels of P27 (0.151 ± 0.010 vs 0.068 ± 0.014, 0.060 ± 0.013) and caspase-9 (0.136 ± 0.042 vs 0.075 ± 0.010, 0.073 ± 0.072) were significantly upregulated. HMGA2 shRNA gene silencing induces apoptosis and suppresses proliferation of MKN-45 cells.

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.

Genetic Variation in Candidate Genes Like the HMGA2 Gene in the Extremely Tall

Background/Aims: Genetic variation in several candidate genes has been associated with short stature. Recently, a high-mobility group A2 (HMGA2) gene SNP has been robustly associated with height in the general population. Only few have attempted to study these genes in extremely tall stature. We therefore studied common genetic variation in candidate genes for height in extremely tall Dutch. Methods: We included 116 constitutionally tall cases with height >2 SD and 103 controls with normally distributed height <2 SD. We genotyped 10 common polymorphisms previously associated with height variation. Results: The HMGA2 gene SNP was significantly associated with tall stature. Using a logistic regression model, we calculated that carrying the HMGA2 (rs1042725) C allele significantly increased the odds of being tall (OR = 1.53, 95% CI 1.02–2.28; p = 0.03). In addition, controls with one or two copies of the C allele were significantly taller than controls carrying the TT genotype [TC: mean (SD) +0.61 (0.21) SDS; p = 0.004, and CC: +0.77 (0.25) SDS; p = 0.003]. Conclusion: Our study shows that a common polymorphism in the HMGA2 gene is not only associated with height variation in the general population but also plays an important role in one of the extremes of the height distribution.

Isolated GH deficiency: mutation screening and copy number analysis of HMGA2 and CDK6 genes

In most patients, the genetic cause of isolated GH deficiency (IGHD) is unknown. By identifying several genes associated with height variability within the normal population, three separate genome-wide association studies provided new candidate genes for human growth disorders. We selected two of them for genetic screening of our IGHD population. We aimed to determine whether high-mobility group A2 (HMGA2) and cyclin-dependent protein kinase 6 (CDK6) are involved in the pathogenicity of IGHD. We directly sequenced coding regions and exon-intron boundaries of the genes HMGA2 and CDK6 in 105 Caucasian IGHD patients from the Dutch HYPOPIT study. In addition, we developed a new probe set of multiplex ligation-dependent probe amplification for both genes in order to detect copy number variations. In one patient with classical IGHD phenotype, we identified a new heterozygous 20 bp deletion in the intronic region of HMGA2 (c.250-29_-9del), which was absent in the databases and healthy controls. Together, with recently published data concerning the 12q14 microdeletion syndrome, where patients with an HMGA2 haploinsufficiency had proportionate short stature, this study provides further support of the important role for HMGA2 in growth. In CDK6, we found only known polymorphisms. This study provides the first report of a deletion in the HMGA2 gene that might be related to IGHD. We suggest that this gene is investigated as a second screening in patients with a classical IGHD phenotype in which mutations in classical candidate genes have been excluded.

Confirmation that SNPs in the high mobility group‐A2 gene (HMGA2) are associated with adult height in the Japanese population; wide‐ranging population survey of height‐related SNPs in HMGA2

Adult height is a highly heritable trait in that multiple genes are involved. Recent genome-wide association studies have identified a novel single-nucleotide polymorphism (SNP) rs1042725 in the high mobility group-A2 gene (HMGA2) and shown it to be associated with human height in Caucasian populations. We performed a replication study to examine the associations between SNPs in HMGA2 and adult height in the Japanese population based on autopsy cases. Although we could not confirm a significant association between rs1042725 in HMGA2 and adult height, another SNP, rs7968902, in the gene achieved significance for its association in the same populations, and the effect was the same as that documented previously. These findings permit us to conclude that the SNPs in HMGA2 are common variants influencing human height across different populations. Moreover, a worldwide population study of these SNPs using 14 different populations including Asians, Africans and Caucasians demonstrated that both haplotypes and genotypes for three height-related SNPs (rs1042725, rs7968682 and rs7968902) in HMGA2 were distributed in an ethnicity-dependent manner. This information will be useful for clarifying the genetic basis of human height.

Abstract 2905: The HMGA1-MMP-2 pathway in poorly differentiated uterine tumors

Abstract Uterine cancer is the most common cancer of the female genital tract and the fourth most frequent cause for cancer death in women in the United States. Thus, further study has the potential to significantly benefit women's health worldwide. Despite the high prevalence of this disease, the molecular events that lead to uterine cancers are poorly understood. We are studying the role of the high mobility group A1 (HMGA1) gene in the pathogenesis of uterine cancer. The HMGA1 gene encodes the HMGA1a and HMGA1b chromatin remodeling proteins, which function in modulating gene expression. In a previously published pilot study, we showed that HMGA1 is overexpressed in poorly differentiated uterine cancers, but not in normal uterine tissue, benign tumors, or most low-grade neoplasms of the uterus. We also engineered HMGA1 transgenic mice and found that all females develop uterine sarcomas by 9 months of age. In lung cancer, we reported that HMGA1 induces expression of the matrix metalloproteinase-2 (MMP-2) gene, but only in poorly differentiated tumors, suggesting that this pathway could drive tumor progression and a poorly differentiated state. Here, we investigated the role of the HMGA1-MMP-2 pathway in the pathogenesis of uterine tumorigenesis. Using a genetic approach, we crossed our HMGA1 transgenic mice with mice that are null for the MMP-2 gene. We found that the uterine tumors were significantly smaller in the HMGA1 transgenic mice that are also null for MMP-2. To determine if this pathway is involved in human uterine tumorigenesis, we assessed expression of the HMGA1 and MMP-2 genes in primary, human uterine tumors. We studied: 1.) endometrioid tumors, which are derived from the endometrial epithelium and tend to be low-grade (well-differentiated), 2.) serous tumors, which are also derived from the endometrial epithelium, but tend to be high-grade (poorly differentiated), and, 3.) carcinosarcomas (or mixed malignant, mullerian tumors), which are derived from the endometrial epithelium and stroma and tend to by high-grade. We found that HMGA1 expression was highest in the high-grade serous tumors and carcinosarcomas, with lower levels in the endometrioid tumors. Moreover, we found that there was a significant correlation between HMGA1 and MMP-2, but only in the high-grade carcinosarcomas and serous tumors. Taken together, our studies demonstrate that HMGA1 induces expression of MMP-2 during uterine tumorigenesis and suggest that this pathway is important in aggressive, poorly differentiated tumors. Although further studies are needed, our findings also suggest that the HMGA1-MMP-2 pathway could serve as a rational therapeutic target in poorly differentiated uterine cancer. 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 2905. doi:10.1158/1538-7445.AM2011-2905

Functional Variants of the &lt;emph type="ital"&gt;HMGA1&lt;/emph&gt; Gene and Type 2 Diabetes Mellitus

High-mobility group A1 (HMGA1) protein is a key regulator of insulin receptor (INSR) gene expression. We previously identified a functional HMGA1 gene variant in 2 insulin-resistant patients with decreased INSR expression and type 2 diabetes mellitus (DM). To examine the association of HMGA1 gene variants with type 2 DM. Case-control study that analyzed the HMGA1 gene in patients with type 2 DM and controls from 3 populations of white European ancestry. Italian patients with type 2 DM (n = 3278) and 2 groups of controls (n = 3328) were attending the University of Catanzaro outpatient clinics and other health care sites in Calabria, Italy, during 2003-2009; US patients with type 2 DM (n = 970) were recruited in Northern California clinics between 1994 and 2005 and controls (n = 958) were senior athletes without DM collected in 2004 and 2009; and French patients with type 2 DM (n = 354) and healthy controls (n = 50) were enrolled at the University of Reims in 1992. Genomic DNA was either directly sequenced or analyzed for specific HMGA1 mutations. Messenger RNA and protein expression for HMGA1 and INSR were measured in both peripheral lymphomonocytes and cultured Epstein-Barr virus-transformed lymphoblasts from patients with type 2 DM and controls. The frequency of HMGA1 gene variants among cases and controls. Odds ratios (ORs) for type 2 DM were estimated by logistic regression analysis. The most frequent functional HMGA1 variant, IVS5-13insC, was present in 7% to 8% of patients with type 2 DM in all 3 populations. The prevalence of IVS5-13insC variant was higher among patients with type 2 DM than among controls in the Italian population (7.23% vs 0.43% in one control group; OR, 15.77 [95% confidence interval {CI}, 8.57-29.03]; P < .001 and 7.23% vs 3.32% in the other control group; OR, 2.03 [95% CI, 1.51-3.43]; P < .001). In the US population, the prevalence of IVS5-13insC variant was 7.7% among patients with type 2 DM vs 4.7% among controls (OR, 1.64 [95% CI, 1.05-2.57]; P = .03). In the French population, the prevalence of IVS5-13insC variant was 7.6% among patients with type 2 DM and 0% among controls (P = .046). In the Italian population, 3 other functional variants were observed. When all 4 variants were analyzed, HMGA1 defects were present in 9.8% of Italian patients with type 2 DM and 0.6% of controls. In addition to the IVS5 C-insertion, the c.310G>T (p.E104X) variant was found in 14 patients and no controls (Bonferroni-adjusted P = .01); the c.*82G>A variant (rs2780219) was found in 46 patients and 5 controls (Bonferroni-adjusted P < .001); the c.*369del variant was found in 24 patients and no controls (Bonferroni-adjusted P < .001). In circulating monocytes and Epstein-Barr virus-transformed lymphoblasts from patients with type 2 DM and the IVS5-13insC variant, the messenger RNA levels and protein content of both HMGA1 and the INSR were decreased by 40% to 50%, and these defects were corrected by transfection with HMGA1 complementary DNA. Compared with healthy controls, the presence of functional HMGA1 gene variants in individuals of white European ancestry was associated with type 2 DM.

Abstract 4098: The HMGA1-COX-2 axis: A molecular pathway leading to tumor progression in human pancreatic adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma is a highly lethal cancer accounting for over 160,000 deaths worldwide each year. Despite the high prevalence of pancreatic cancer, the molecular events that lead to tumor progression are poorly understood. The high-mobility group A1 gene (HMGA1) is enriched in diverse, high-grade cancers and embryonic stem cells. This gene encodes the HMGA1a and HMGA1b chromatin remodeling proteins, which function in regulating gene expression. We previously showed that HMGA1 induces oncogenic transformation in cultured cells and causes aggressive cancers in transgenic mice. Moreover, we found that high HMGA1 protein levels correlate with poor differentiation status and decreased survival in a study of &amp;gt; 100 primary pancreatic ductal adenocarcinomas. These findings suggest that HMGA1 could drive a poorly differentiated, stem cell-like state and tumor progression in pancreatic ductal adenocarcinoma. In cultured, human pancreatic cells that overexpress K-RAS (HPNE-K-RAS cells), forced overexpression of HMGA1a leads to increased migration, invasion, and a transformed phenotype with anchorage-independent cell growth in soft agar. Because cyclooxygenase-2 (COX-2) is a downstream gene directly activated by HMGA1a in uterine cancers, we investigated the role of the HMGA1-COX-2 pathway in pancreatic adenocarcinoma. Our preliminary data suggest that HMGA1a and COX-2 mRNA levels are positively correlated in a pancreatic cancer cell lines. By chromatin immunoprecipitation, we found that HMGA1a binds to the COX-2 promoter in human pancreatic adenocarcinoma cells. Moreover, COX-2 inhibitors block tumorigenesis in human pancreatic cancer xenografts in nude mice. Taken together, our studies suggest that HMGA1a promotes tumor progression through up-regulation of COX-2 and this pathway could be targeted to treat or prevent human pancreatic adenocarcinoma. 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 4098.