BRCA1 regulates transforming growth factor-β (TGF-β1) signaling through Gadd45a by enhancing the protein stability of Smad4

Discovery of Selective Histone Deacetylase 1 and 2 Inhibitors: Screening of a Focused Library Constructed by Click Chemistry, Kinetic Binding Analysis, and Biological Evaluation

Histone deacetylase 1 and 2 (HDAC1/2) inhibitors are potentially useful as tools for probing the biological functions of the isoforms and as therapeutic agents for cancer and neurodegenerative disorders. To discover potent and selective inhibitors, we screened a focused library synthesized by using click chemistry and obtained KPZ560 as an HDAC1/2-selective inhibitor. Kinetic binding analysis revealed that KPZ560 inhibits HDAC2 through a two-step slow-binding mechanism. In cellular assays, KPZ560 induced a dose- and time-dependent increase of histone acetylation and showed potent breast cancer cell growth-inhibitory activity. In addition, gene expression analyses suggested that the two-step slow-binding inhibition by KPZ560 regulated the expression of genes associated with cell proliferation and DNA damage. KPZ560 also induced neurite outgrowth of Neuro-2a cells and an increase in the spine density of granule neuron dendrites of mice. The unique two-step slow-binding character of o-aminoanilides such as KPZ560 makes them interesting candidates as therapeutic agents.

Plasma Protein Biomarkers Associated with Higher Ovarian Cancer Risk in BRCA1/2 Carriers

Simple Summary

Most hereditary ovarian cancer is associated with BRCA1/2 variants, and risk-reducing salpingo-oophorectomy during the follow-up monitoring of ovarian cancer development in heathy women with the BRCA1/2 variant reduces ovarian cancer incidence. The aim of this study was to identify plasma protein biomarkers that can indicate an increased risk of developing ovarian cancer using a proteomic approach based on a population of genetic variants. Two identified biomarkers among differentially expressed proteins, SPARC and THBS1, had lower plasma concentrations in healthy BRCA1/2 variant carriers than in ovarian cancer patients with the BRCA1/2 variant; concentration of two proteins increased at the onset of ovarian cancer. These protein markers from non-invasive liquid biopsy sampling could be used to help women with the BRCA1/2 variant determine whether to undergo an oophorectomy that could potentially affect the quality of life.

Abstract

Ovarian cancer (OC) is the most lethal gynecologic malignancy and in-time diagnosis is limited because of the absence of effective biomarkers. Germline BRCA1/2 genetic alterations are risk factors for hereditary OC; risk-reducing salpingo-oophorectomy (RRSO) is pursued for disease prevention. However, not all healthy carriers develop the disease. Therefore, identifying predictive markers in the BRCA1/2 carrier population could help improve the identification of candidates for preventive RRSO. In this study, plasma samples from 20 OC patients (10 patients with BRCA1/2 wild type (_wt) and 10 with the BRCA1/2 variant (_var)) and 20 normal subjects (10 subjects with BRCA1/2_wt and 10 with BRCA1/2_var) were analyzed for potential biomarkers of hereditary OC. We applied a bottom-up proteomics approach, using nano-flow LC-MS to analyze depleted plasma proteome quantitatively, and potential plasma protein markers specific to the BRCA1/2 variant were identified from a comparative statistical analysis of the four groups. We obtained 1505 protein candidates from the 40 subjects, and SPARC and THBS1 were verified by enzyme-linked immunosorbent assay. Plasma SPARC and THBS1 concentrations in healthy BRCA1/2 carriers were found to be lower than in OC patients with BRCA1/2_var. If plasma SPARC concentrations increase over 337.35 ng/mL or plasma THBS1 concentrations increase over 65.28 μg/mL in a healthy BRCA1/2 carrier, oophorectomy may be suggested.

TGFβ signaling networks in ovarian cancer progression and plasticity

Epithelial ovarian cancer (EOC) is a leading cause of cancer-related death in women. Late-stage diagnosis with significant tumor burden, accompanied by recurrence and chemotherapy resistance, contributes to this poor prognosis. These morbidities are known to be tied to events associated with epithelial-mesenchymal transition (EMT) in cancer. During EMT, localized tumor cells alter their polarity, cell-cell junctions, cell-matrix interactions, acquire motility and invasiveness and an exaggerated potential for metastatic spread. Key triggers for EMT include the Transforming Growth Factor-β (TGFβ) family of growth factors which are actively produced by a wide array of cell types within a specific tumor and metastatic environment. Although TGFβ can act as either a tumor suppressor or promoter in cancer, TGFβ exhibits its pro-tumorigenic functions at least in part via EMT. TGFβ regulates EMT both at the transcriptional and post-transcriptional levels as outlined here. Despite recent advances in TGFβ based therapeutics, limited progress has been seen for ovarian cancers that are in much need of new therapeutic strategies. Here, we summarize and discuss several recent insights into the underlying signaling mechanisms of the TGFβ isoforms in EMT in the unique metastatic environment of EOCs and the current therapeutic interventions that may be relevant.

Comparative analysis of the expression profiles of genes related to the Gadd45α signaling pathway in four kinds of liver diseases

Gadd45α (growth arrest and DNA damage inducible alpha) is a member of a group of genes whose transcript levels are increased following stressful conditions that lead to growth arrest and treatment with agents that lead to DNA damage. Gadd45α is upregulated in liver cirrhosis (LC), hepatic cancer (HC), acute liver failure (AHF) and non-alcoholic fatty liver disease(NAFLD). Here, we investigated the essential differences in the Gadd45α signaling pathway in these diseases at the transcriptional level. The results showed that 44, 46, 71 and 27 genes significant changes in these diseases, and the H-cluster showed that the expression of the Gadd45α signaling-related genes was significantly different in the four liver diseases. DAVID functional analysis showed that the Gadd45α signaling pathway-related genes were mainly involved in cell adhesion and migration, cell proliferation, apoptosis, stress and inflammatory responses, etc. Ingenuity pathway analysis (IPA) software was used to predict the functions of the Gadd45α signaling-related genes, and the results indicated that there were significant changes in cell differentiation, DNA damage repair, autophagy, apoptosis and necrosis. Gadd45α signaling pathway is involved in four kinds of liver disease and regulates a variety of activities via P38 MAPK, NF-κB, mTOR/STAT3, P21, PCNA, PI3K/Akt and other signaling pathways. Modulation of Gadd45α may be exploited to prevent the progression of liver disease, and to identify specific treatments for different stages of liver disease. In summary, the Gadd45α signaling pathway is involved in four kinds of liver disease and regulates a variety of physiological activities through various signaling pathways.

Derivate isocorydine inhibits cell proliferation in hepatocellular carcinoma cell lines by inducing G2/M cell cycle arrest and apoptosis

We have previously demonstrated that isocorydine (ICD) can be served as a potential antitumor agent in hepatocellular carcinoma (HCC). A novel derivate of isocorydine (d-ICD) could significantly improve its anticancer activity in tumors. However, the molecular mechanisms of d-ICD on HCC cells remain to be unclear. In this study, we observed that d-ICD inhibited cell proliferation and induced apoptosis of HCC cells in a concentration-dependent manner. We found d-ICD induced G2/M cycle arrest of HCC cells via DNA damage 45 alpha (GADD45A) and p21 pathway in vitro and in vivo. In d-ICD-treated cells, cell cycle-related proteins cyclin B1 and p-CDC2 were upregulated and p-cyclin B1, CDC2, and E2F1 were inhibited. p21 expression can be reversed by knockdown of GADD45A in d-ICD-treated HCC cells. Enforced expression of CCAAT/enhancer-binding protein β (C/EBPβ) in combination with d-ICD enhanced the p21 expression in HCC cells. Furthermore, the luciferase reporter assay showed that upregulation of GADD45A by C/EBPβ was achieved through the increase of GADD45A promoter activity. These findings indicate that d-ICD inhibits cell proliferation and induces cell cycle arrest through activation of C/EBPβ-GADD45A-p21 pathway in HCC cells. d-ICD might be a promising chemotherapeutic agent for the treatment of HCC.

BRCA1 regulates transforming growth factor-β (TGF-β1) signaling through Gadd45a by enhancing the protein stability of Smad4

BRCA1 is a well established tumor suppressor gene, which is involved in many cellular processes, including DNA damage repair, cell cycle control, apoptosis, as well as transcriptional control. In this work, we have found that BRCA1 is involved in regulating TGF-β1/Smad pathway. The loss of endogenous BRCA1 greatly attenuated TGF-β1-induced growth inhibition and cell cycle G1 arrest. BRCA1 greatly maintains stability of Smad4 protein, and the loss of BRCA1 results in Smad4 down-regulation, which is likely related to its downstream gene Gadd45a. Gadd45a is able to interact with β-Trcp1, a-F-box protein of SCF E3 ligase, and consequently suppresses the ubiquitin-degradation of Smad4 by SCF(β-trcp1), as reflected by the observations that the induction of Gadd45a substantially stabilizes Smad4 protein. In addition, exogenous expression of Gadd45a can largely rescue the protein level of Smad4 in BRCA1 deficient cells. These results further demonstrate that BRCA1 may act as an important negative regulator in cell cycle progression and tumorigenesis through regulating the stability of Smad4, and define a novel link that connects BRCA1 to TGF-β1/Smad pathway.