Project description:High-mobility group A (HMGA) proteins are non-histone nuclear proteins that bind DNA and several transcription factors. They are involved in the regulation of chromatin structure and function. HMGA protein expression is low in normal adult tissues, but abundant during embryonic development and in several human tumours. Rearrangements of the HMGA genes have been frequently detected in human benign tumours of mesenchymal origin, e.g. lipomas, lung hamartomas and uterine leiomiomas. HMGA proteins have been implicated in the control of cell growth and differentiation of the pre-adipocytic cell line 3T3-L1. In an attempt to better understand the role of HMGA1 proteins in haematological neoplasias and in the differentiation of haematopietic cells, we have investigated their expression in human leukaemias and in leukaemic cell lines induced to terminal differentiation. Here we report HMGA1 overexpression in most fresh human leukaemias of different origin and in several leukaemic cell lines. Moreover, differentiation of three cell lines towards the megakaryocytic phenotype was associated with HMGA1 protein induction, whereas induction of erythroid and monocytic differentiation generally resulted in reduced HMGA1 expression.
Project description:High Mobility Group A1 (HMGA1) is an architectural chromatin protein whose overexpression is a feature of malignant neoplasias with a causal role in cancer initiation and progression. HMGA1 promotes tumor growth by several mechanisms, including increase of cell proliferation and survival, impairment of DNA repair and induction of chromosome instability. Autophagy is a self-degradative process that, by providing energy sources and removing damaged organelles and misfolded proteins, allows cell survival under stress conditions. On the other hand, hyper-activated autophagy can lead to non-apoptotic programmed cell death. Autophagy deregulation is a common feature of cancer cells in which has a complex role, showing either an oncogenic or tumor suppressor activity, depending on cellular context and tumor stage. Here, we report that depletion of HMGA1 perturbs autophagy by different mechanisms. HMGA1-knockdown increases autophagosome formation by constraining the activity of the mTOR pathway, a major regulator of autophagy, and transcriptionally upregulating the autophagy-initiating kinase Unc-51-like kinase 1 (ULK1). Consistently, functional experiments demonstrate that HMGA1 binds ULK1 promoter region and negatively regulates its transcription. On the other hand, the increase in autophagosomes is not associated to a proportionate increase in their maturation. Overall, the effects of HMGA1 depletion on autophagy are associated to a decrease in cell proliferation and ultimately impact on cancer cells viability. Importantly, silencing of ULK1 prevents the effects of HMGA1-knockdown on cellular proliferation, viability and autophagic activity, highlighting how these effects are, at least in part, mediated by ULK1. Interestingly, this phenomenon is not restricted to skin cancer cells, as similar results have been observed also in HeLa cells silenced for HMGA1. Taken together, these results clearly indicate HMGA1 as a key regulator of the autophagic pathway in cancer cells, thus suggesting a novel mechanism through which HMGA1 can contribute to cancer progression.
Project description:Plasticity is an essential condition for cancer cells to invade surrounding tissues. The nucleus is the most rigid cellular organelle and it undergoes substantial deformations to get through environmental constrictions. Nuclear stiffness mostly depends on the nuclear lamina and chromatin, which in turn might be affected by nuclear architectural proteins. Among these is the HMGA1 (High Mobility Group A1) protein, a factor that plays a causal role in neoplastic transformation and that is able to disentangle heterochromatic domains by H1 displacement. Here we made use of atomic force microscopy to analyze the stiffness of breast cancer cellular models in which we modulated HMGA1 expression to investigate its role in regulating nuclear plasticity. Since histone H1 is the main modulator of chromatin structure and HMGA1 is a well-established histone H1 competitor, we correlated HMGA1 expression and cellular stiffness with histone H1 expression level, post-translational modifications, and nuclear distribution. Our results showed that HMGA1 expression level correlates with nuclear stiffness, is associated to histone H1 phosphorylation status, and alters both histone H1 chromatin distribution and expression. These data suggest that HMGA1 might promote chromatin relaxation through a histone H1-mediated mechanism strongly impacting on the invasiveness of cancer cells.
Project description:HMGA1 (high-mobility-group A1) proteins are architectural transcription factors that are found overexpressed in embryogenesis and malignant tumours. We have shown previously that they have a role in lymphopoiesis, since the loss of HMGA1 expression leads to an impairment of T-cell development and to an increase in B-cell population. Since RAGs (recombination activating genes) are key regulators of lymphoid differentiation, in the present study we investigate whether RAG2 expression is dependent on HMGA1 activity. We show that RAG2 gene expression is up-regulated in Hmga1-/- ES (embryonic stem) cells and EBs (embryoid bodies) as well as in yolk sacs and fibroblasts from Hmga1-/- mice, suggesting that HMGA1 proteins control RAG2 gene expression both in vitro and in vivo. We show that the effect of HMGA1 on RAG2 expression is direct, identify the responsible region in the RAG2 promoter and demonstrate binding to the promoter in vivo using chromatin immunoprecipitation. Since RAG2 is necessary for lymphoid cell development, our results suggest a novel mechanism by which HMGA1 might regulate lymphoid differentiation.
Project description:Background & objectivesChromatin 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.ConclusionFurther elucidation of HMGA1 function should lead to novel therapeutic strategies for cancer and possibly for other diseases associated with aberrant HMGA1 expression.
Project description:Expression of miR-4730 in hepatocellular carcinoma suppresses tumor progression, and might be a prognostic marker or a therapeutic target of miRNA-based therapies.
Project description:Fine needle aspiration biopsies (FNABs) of breast cancers were taken before and after surgeries from 16 patients. The cDNA microarray data were used to determine the gene expression profile responding to patient's clinical finding and tumor's pathological changes. A gene profile was generated as Estrogen Receptor Gene Signature (ERGS). The ERGS was verified in a reference dataset and correlated with patient's prognosis significantly. Keywords: Breast cancer, fine needle biopsy, estrogen receptor, prognostic gene signature Dye-swap technical replicates were included both FNABs taken before and after surgeries for every patient, then the four replicated array data per patient were combined for analysis.
Project description:Fine needle aspiration biopsies (FNABs) of breast cancers were taken before and after surgeries from 16 patients. The cDNA microarray data were used to determine the gene expression profile responding to patient's clinical finding and tumor's pathological changes. A gene profile was generated as Estrogen Receptor Gene Signature (ERGS). The ERGS was verified in a reference dataset and correlated with patient's prognosis significantly. Keywords: Breast cancer, fine needle biopsy, estrogen receptor, prognostic gene signature
Project description:Fine needle aspiration biopsies (FNABs) of breast cancers were taken before and after surgeries from 16 patients. The cDNA microarray data were used to determine the gene expression profile responding to patient's clinical finding and tumor's pathological changes. A gene profile was generated as Estrogen Receptor Gene Signature (ERGS). The ERGS was verified in a reference dataset and correlated with patient's prognosis significantly. Keywords: Breast cancer, fine needle biopsy, estrogen receptor, prognostic gene signature Dye-swap technical replicates were included both FNABs taken before and after surgeries for every patient, then the four replicated array data per patient were combined for analysis.
Project description:Cancer is a very heterogeneous disease, and biological variability adds a further level of complexity, thus limiting the ability to identify new genes involved in cancer development. Oncogenes whose expression levels control cell aggressiveness are very useful for developing cellular models that permit differential expression screenings in isogenic contexts. HMGA1 protein has this unique property because it is a master regulator in breast cancer cells that control the transition from a nontumorigenic epithelial-like phenotype toward a highly aggressive mesenchymal-like one. The proteins extracted from HMGA1-silenced and control MDA-MB-231 cells were analyzed using label-free shotgun mass spectrometry. The differentially expressed proteins were cross-referenced with DNA microarray data obtained using the same cellular model and the overlapping genes were filtered for factors linked to poor prognosis in breast cancer gene expression meta-data sets, resulting in an HMGA1 protein signature composed of 21 members (HRS, HMGA1 reduced signature). This signature had a prognostic value (overall survival, relapse-free survival, and distant metastasis-free survival) in breast cancer. qRT-PCR, Western blot, and immunohistochemistry analyses validated the link of three members of this signature (KIFC1, LRRC59, and TRIP13) with HMGA1 expression levels both in vitro and in vivo and wound healing assays demonstrated that these three proteins are involved in modulating tumor cell motility. Combining proteomic and genomic data with the aid of bioinformatic tools, our results highlight the potential involvement in neoplastic transformation of a restricted list of factors with an as-yet-unexplored role in cancer. These factors are druggable targets that could be exploited for the development of new, targeted therapeutic approaches in triple-negative breast cancer.