Evidence that GTP-binding domain but not catalytic domain of transglutaminase 2 is essential for epithelial-to-mesenchymal transition in mammary epithelial cells

INTRODUCTION: The expression of proinflammatory protein tissue transglutaminase 2 (TG2) is frequently upregulated in multiple cancer cell types. However, the exact role of TG2 in cancer cells is not well-understood. We recently initiated studies to determine the significance of TG2 in cancer cells and observed that sustained expression of TG2 resulted in epithelial-to-mesenchymal transition (EMT) and promoted cancer stem cell (CSC) traits in mammary epithelial cells. These results suggested that TG2 could serve as a promising therapeutic target for overcoming chemoresistance and inhibiting metastatic spread of cancer cells. METHODS: Using various mutant constructs, we analyzed the activity of TG2 that is essential for promoting the EMT-CSC phenotype. RESULTS: Our results suggest that catalytically inactive TG2 (TG2-C277S) is as effective as wild-type TG2 (TG2-WT) in inducing the EMT-CSC in mammary epithelial cells. In contrast, overexpression of a GTP-binding-deficient mutant (TG2-R580A) was completely incompetent in this regard. Moreover, TG2-dependent activation of the proinflammatory transcription factor NF-κB is deemed essential for promoting the EMT-CSC phenotype in mammary epithelial cells. CONCLUSIONS: Our results suggest that the transamidation activity of TG2 is not essential for promoting its oncogenic functions and provide a strong rationale for developing small-molecule inhibitors to block GTP-binding pockets of TG2. Such inhibitors may have great potential for inhibiting the TG2-regulated pathways, reversing drug resistance and inhibiting the metastasis of cancer cells

Effect of kidney donation on bone mineral metabolism.

Kidney donation results in reductions in kidney function and lasting perturbations in phosphate homeostasis, which may lead to adverse cardiovascular sequelae. However, the acute effects of kidney donation on bone mineral parameters including regulators of calcium and phosphate metabolism are unknown. We conducted a prospective observational controlled study to determine the acute effects of kidney donation on mineral metabolism and skeletal health. Biochemical endpoints were determined before and after donation on days 1, 2 and 3, 6 weeks and 12 months in donors and at baseline, 6 weeks and 12 months in controls. Baseline characteristic of donors (n = 34) and controls (n = 34) were similar: age (53±10 vs 50±14 years, p = 0.33), BMI (26.3±2.89 vs 25.9±3.65, p = 0.59), systolic BP (128±13 vs 130±6 mmHg, p = 0.59), diastolic BP (80±9 vs 81±9 mmHg, p = 0.68) and baseline GFR (84.4±20.2 vs 83.6±25.2 ml/min/1.73m2, p = 0.89). eGFR reduced from 84.4±20.2 to 52.3±17.5 ml/min/1.73m2 (p<0.001) by day 1 with incomplete recovery by 12 months (67.7±22.6; p = 0.002). Phosphate increased by day 1 (1.1(0.9-1.2) to 1.3(1.1-1.4) mmol/L, p <0.001) but declined to 0.8(0.8-1.0) mmol/L (p<0.001) before normalizing by 6 weeks. Calcium declined on day 1 (p = 0.003) but recovered at 6 weeks or 12 months. PTH and FGF-23 remained unchanged, but α-Klotho reduced by day 1 (p = 0.001) and remained low at 6 weeks (p = 0.02) and 1 year (p = 0.04). In this study, we conclude that kidney donation results in acute disturbances in mineral metabolism characterised by a reduced phosphate and circulating α-Klotho concentration without acute changes in the phosphaturic hormones FGF23 and PTH

Anti-Inflammatory ent-Kaurane Diterpenoids from Isodon serra

Ten new ent-kaurane diterpenoids, including two pairs of epimers 1/2 and 4/5 and a 6,7-seco-ent-kauranoid 10, were obtained from the aerial parts of Isodon serra. The structures of the new compounds were confirmed by extensive spectroscopic methods and electronic circular dichroism (ECD) data analysis. An anti-inflammatory assay was applied to evaluate their nitric oxide (NO) inhibitory activities by using LPS-stimulated BV-2 cells. Compounds 1 and 9 exhibited notable NO production inhibition with IC50 values of 15.6 and 7.3 μM, respectively. Moreover, the interactions of some bioactive diterpenoids with inducible nitric oxide synthase (iNOS) were explored by employing molecular docking studies.https://pubs.acs.org/journal/jnprdf2021-09-29hj2021Plant Production and Soil Scienc

Evidence That Aberrant Expression of Tissue Transglutaminase Promotes Stem Cell Characteristics in Mammary Epithelial Cells

Cancer stem cells (CSCs) or tumor initiating cells (TICs) make up only a small fraction of total tumor cell population, but recent evidence suggests that they are responsible for tumor initiation and the maintenance of tumor growth. Whether CSCs/TICs originate from normal stem cells or result from the dedifferentiation of terminally differentiated cells remains unknown. Here we provide evidence that sustained expression of the proinflammatory protein tissue transglutaminase (TG2) confers stem cell like properties in non-transformed and transformed mammary epithelial cells. Sustained expression of TG2 was associated with increase in CD44high/CD24low/- subpopulation, increased ability of cells to form mammospheres, and acquisition of self-renewal ability. Mammospheres derived from TG2-transfected mammary epithelial cells (MCF10A) differentiated into complex secondary structures when grown in Matrigel cultures. Cells in these secondary structures differentiated into Muc1-positive (luminal marker) and integrin α6-positive (basal marker) cells in response to prolactin treatment. Highly aggressive MDA-231 and drug-resistant MCF-7/RT breast cancer cells, which express high basal levels of TG2, shared many traits with TG2-transfected MCF10A stem cells but unlike MCF10A-derived stem cells they failed to form the secondary structures and to differentiate into Muc1-positive luminal cells when grown in Matrigel culture. Downregulation of TG2 attenuated stem cell properties in both non-transformed and transformed mammary epithelial cells. Taken together, these results suggested a new function for TG2 and revealed a novel mechanism responsible for promoting the stem cell characteristics in adult mammary epithelial cells

Tissue Transglutaminase Promotes Drug Resistance and Invasion by Inducing Mesenchymal Transition in Mammary Epithelial Cells

Recent observations that aberrant expression of tissue transglutaminase (TG2) promotes growth, survival, and metastasis of multiple tumor types is of great significance and could yield novel therapeutic targets for improved patient outcomes. To accomplish this, a clear understanding of how TG2 contributes to these phenotypes is essential. Using mammary epithelial cell lines (MCF10A, MCF12A, MCF7 and MCF7/RT) as a model system, we determined the impact of TG2 expression on cell growth, cell survival, invasion, and differentiation. Our results show that TG2 expression promotes drug resistance and invasive functions by inducing epithelial-mesenchymal transition (EMT). Thus, TG2 expression supported anchorage-independent growth of mammary epithelial cells in soft-agar, disrupted the apical-basal polarity, and resulted in disorganized acini structures when grown in 3D-culture. At molecular level, TG2 expression resulted in loss of E-cadherin and increased the expression of various transcriptional repressors (Snail1, Zeb1, Zeb2 and Twist1). Tumor growth factor-beta (TGF-β) failed to induce EMT in cells lacking TG2 expression, suggesting that TG2 is a downstream effector of TGF-β-induced EMT. Moreover, TG2 expression induced stem cell-like phenotype in mammary epithelial cells as revealed by enrichment of CD44+/CD24-/low cell populations. Overall, our studies show that aberrant expression of TG2 is sufficient for inducing EMT in epithelial cells and establish a strong link between TG2 expression and progression of metastatic breast disease

Stiatistical Issues in Meta-Analysis

In statistical meta-analysis paradigm dealing with the techniques of pooling of evidence across several studies, the notion of effect size is fundamental and it is necessary to perform appropriate tests for the equality of population effect sizes arising out of these studies before performing any meta-analysis. A well known test for homogeneity in this context is based on Cochran's chi-square statistic. However Cochran's test might be inaccurate in testing homogeneity for some effect sizes in the sense of not maintaining the stipulated Type I errors. In this dissertation, three such scenarios are identified: 1) testing homogeneity of standardized mean difference, 2) testing homogeneity of correlations and correlation matrices, and 3) testing homogeneity of proportions with low event rates, and in each case the severe inadequacy of Cochran's homogeneity test is demonstrated. Apppropriate bootstrap procedures for testing homogeneity hypotheses are suggested, and applications in each problem are indicated. Two additional problems are also dealt with in the dissertation: Mantel-Haenszel and Peto weights in random effects meta-analysis, and extraction methods in statistical meta-analysis

Stiatistical Issues in Meta-Analysis

In statistical meta-analysis paradigm dealing with the techniques of pooling of evidence across several studies, the notion of effect size is fundamental and it is necessary to perform appropriate tests for the equality of population effect sizes arising out of these studies before performing any meta-analysis. A well known test for homogeneity in this context is based on Cochran's chi-square statistic. However Cochran's test might be inaccurate in testing homogeneity for some effect sizes in the sense of not maintaining the stipulated Type I errors. In this dissertation, three such scenarios are identified: 1) testing homogeneity of standardized mean difference, 2) testing homogeneity of correlations and correlation matrices, and 3) testing homogeneity of proportions with low event rates, and in each case the severe inadequacy of Cochran's homogeneity test is demonstrated. Apppropriate bootstrap procedures for testing homogeneity hypotheses are suggested, and applications in each problem are indicated. Two additional problems are also dealt with in the dissertation: Mantel-Haenszel and Peto weights in random effects meta-analysis, and extraction methods in statistical meta-analysis