Hmga1 is differentially expressed and mediates silencing of the CD4/CD8 loci in T cell lineages and leukemic cells

HMGA Proteins in Hematological Malignancies

The high mobility group AT-Hook (HMGA) proteins are a family of nonhistone chromatin remodeling proteins known as "architectural transcriptional factors". By binding the minor groove of AT-rich DNA sequences, they interact with the transcription apparatus, altering the chromatin modeling and regulating gene expression by either enhancing or suppressing the binding of the more usual transcriptional activators and repressors, although they do not themselves have any transcriptional activity. Their involvement in both benign and malignant neoplasias is well-known and supported by a large volume of studies. In this review, we focus on the role of the HMGA proteins in hematological malignancies, exploring the mechanisms through which they enhance neoplastic transformation and how this knowledge could be exploited to devise tailored therapeutic strategies.

LncRNA GACAT3 acts as a competing endogenous RNA of HMGA1 and alleviates cucurbitacin B-induced apoptosis of gastric cancer cells

Long non-coding RNAs (lncRNAs) have been demonstrated to perform important roles in cancer development. Previously, we have shown that lncRNA gastric cancer-associated transcript 3 (GACAT3) is overexpressed in gastric cancer and acts as a downstream target of interleukin 6/signal transducer and activator of transcription 3 (IL-6/STAT3) signaling. However, the role of GACAT3 in regulating gastric cancer cell growth remains unclear. In this study, we demonstrate that GACAT3 acts as a competing endogenous RNA of high mobility group A1 (HMGA1), a typical oncogene that is overexpressed in most types of cancer, based on a search for common miRNA-binding sites and on experiments involving in vitro cell transfection with synthesized miRNA mimics. Furthermore, knockdown of GACAT3 by its specific siRNA resulted in significantly decreased cell proliferation in gastric cancer cells, similar to the effect of an HMGA1 knockdown. Moreover, GACAT3 overexpression alleviated the apoptosis induced by cucurbitacin B, which is a widely used anticancer drug. Mechanistically, GACAT3 amplified STAT3 expression and decreased the level of the apoptosis gene bcl-2-associated X protein (BAX). Thus, our study provides fundamental information regarding GACAT3, which could be a valuable target for gastric cancer therapy.

A plausibly causal functional lupus-associated risk variant in the STAT1-STAT4 locus

Systemic lupus erythematosus (SLE or lupus) (OMIM: 152700) is a chronic autoimmune disease with debilitating inflammation that affects multiple organ systems. The STAT1-STAT4 locus is one of the first and most highly replicated genetic loci associated with lupus risk. We performed a fine-mapping study to identify plausible causal variants within the STAT1-STAT4 locus associated with increased lupus disease risk. Using complementary frequentist and Bayesian approaches in trans-ancestral Discovery and Replication cohorts, we found one variant whose association with lupus risk is supported across ancestries in both the Discovery and Replication cohorts: rs11889341. In B cell lines from patients with lupus and healthy controls, the lupus risk allele of rs11889341 was associated with increased STAT1 expression. We demonstrated that the transcription factor HMGA1, a member of the HMG transcription factor family with an AT-hook DNA-binding domain, has enriched binding to the risk allele compared with the non-risk allele of rs11889341. We identified a genotype-dependent repressive element in the DNA within the intron of STAT4 surrounding rs11889341. Consistent with expression quantitative trait locus (eQTL) analysis, the lupus risk allele of rs11889341 decreased the activity of this putative repressor. Altogether, we present a plausible molecular mechanism for increased lupus risk at the STAT1-STAT4 locus in which the risk allele of rs11889341, the most probable causal variant, leads to elevated STAT1 expression in B cells due to decreased repressor activity mediated by increased binding of HMGA1.

Novel long non-coding RNA GACAT3 promotes gastric cancer cell proliferation through the IL-6/STAT3 signaling pathway

Long non-coding RNAs (lncRNAs) play an important role in cancer occurrence and development. We previously demonstrated that lncRNA gastric cancer-associated transcript 3 (GACAT3) was positively correlated with TNM stages, tumor size, and distant metastasis of patients with gastric cancer. However, the role of GACAT3 in gastric cancer remains unclear. In this study, to investigate its function, we synthesized small interference RNAs (siRNAs) against GACTA3 and developed a GACAT3 overexpression vector (pcDNA3-GACAT3), respectively. The siRNA-mediated knockdown of GACAT3 significantly decreased cell proliferation of the gastric cancer HGC-27 cells, in which GACAT3 is overexpressed. Furthermore, GACAT3 overexpression in gastric cancer SGC-7901 cells promoted cell growth. Moreover, GACAT3 expression in HGC-27 cells was greatly upregulated by IL-6 treatment in a concentration-dependent manner. In contrast, siRNA-mediated knockdown of STAT3 decreased GACAT3 expression even in the presence of IL-6. These results demonstrated that as a downstream target of the IL6/STAT3 signaling, lncRNA GACAT3 promotes gastric cancer cell growth suggesting that GACAT3 is an inflammatory response gene and may be served as a valuable potential target for the treatment of gastric cancer.

HMGA2 promotes adipogenesis by activating C/EBPβ-mediated expression of PPARγ

Adipogenesis is orchestrated by a highly ordered network of transcription factors including peroxisome-proliferator activated receptor-gamma (PPARγ) and CCAAT-enhancer binding protein (C/EBP) family proteins. High mobility group protein AT-hook 2 (HMGA2), an architectural transcription factor, has been reported to play an essential role in preadipocyte proliferation, and its overexpression has been implicated in obesity in mice and humans. However, the direct role of HMGA2 in regulating the gene expression program during adipogenesis is not known. Here, we demonstrate that HMGA2 is required for C/EBPβ-mediated expression of PPARγ, and thus promotes adipogenic differentiation. We observed a transient but marked increase of Hmga2 transcript at an early phase of differentiation of mouse 3T3-L1 preadipocytes. Importantly, Hmga2 knockdown greatly impaired adipocyte formation, while its overexpression promoted the formation of mature adipocytes. We found that HMGA2 colocalized with C/EBPβ in the nucleus and was required for the recruitment of C/EBPβ to its binding element at the Pparγ2 promoter. Accordingly, HMGA2 and C/EBPβ cooperatively enhanced the Pparγ2 promoter activity. Our results indicate that HMGA2 is an essential constituent of the adipogenic transcription factor network, and thus its function may be affected during the course of obesity.

Global characterization of differential gene expression profiles in mouse Vγ1+ and Vγ4+ γδ T cells

Peripheral γδ T cells in mice are classified into two major subpopulations, Vγ1⁺ and Vγ4⁺, based on the composition of T cell receptors. However, their intrinsic differences remain unclear. In this study, we analyzed gene expression profiles of the two subsets using Illumina HiSeq 2000 Sequencer. We identified 1995 transcripts related to the activation of Vγ1⁺ γδ T cells, and 2158 transcripts related to the activation of Vγ4⁺ γδ T cells. We identified 24 transcripts differentially expressed between the two subsets in resting condition, and 20 after PMA/Ionomycin treatment. We found that both cell types maintained phenotypes producing IFN-γ, TNF-α, TGF-β and IL-10. However, Vγ1⁺ γδ T cells produced more Th2 type cytokines, such as IL-4 and IL-5, while Vγ4⁺ γδ T cells preferentially produced IL-17. Our study provides a comprehensive gene expression profile of mouse peripheral Vγ1⁺ and Vγ4⁺ γδ T cells that describes the inherent differences between them.

Transcriptional profiling of melanoma sentinel nodes identify patients with poor outcome and reveal an association of CD30(+) T lymphocytes with progression

Sentinel lymph nodes set the stance of the immune system to a localized tumor and are often the first site to be colonized by neoplastic cells that metastasize. To investigate how the presence of neoplastic cells in sentinel lymph nodes may trigger pathways associated with metastatic progression, we analyzed the transcriptional profiles of archival sentinel node biopsy specimens obtained from melanoma patients. Biopsies from positive nodes were selected for comparable tumor infiltration, presence or absence of further regional node metastases, and relapse at 5-year follow-up. Unsupervised analysis of gene expression profiles revealed immune response to be a major gene ontogeny represented. Among genes upregulated in patients with progressing disease, the TNF receptor family member CD30/TNFRSF8 was confirmed in biopsy specimens from an independent group of patients. Immunohistochemical analysis revealed higher numbers of CD30(+) lymphocytes in nodes from progressing patients compared with nonprogressing patients. Phenotypic profiling demonstrated that CD30(+) lymphocytes comprised a broad population of suppressive or exhausted immune cells, such as CD4(+)Foxp3(+) or PD1(+) subpopulations and CD4(-)CD8(-) T cells. CD30(+) T lymphocytes were increased in peripheral blood lymphocytes of melanoma patients at advanced disease stages. Our findings reinforce the concept that sentinel nodes act as pivotal sites for determining progression patterns, revealing that the presence of CD30(+) lymphocytes at those sites associate positively with melanoma progression.