AGR2 is a SMAD4-suppressible gene that modulates MUC1 levels and promotes the initiation and progression of pancreatic intraepithelial neoplasia

Engineering a synthetic cell panel to identify signalling components reprogrammed by the cell growth regulator anterior gradient-2

AGR2 forms an ER-resident signalling axis in cell development, limb regeneration, and in human diseases like asthma and cancer, yet molecular mechanisms underlying its effects remain largely undefined. A single integrated Flippase recombination target (FRT) site was engineered within the AGR2-non expressing A375 cell line to allow integration of a constitutively expressed AGR2 alleles. This allows an analysis of how AGR2 protein expression reprogrammes intracellular signalling. The engineered expression of AGR2 had marginal impact on global transcription signalling, compared to its paralogue AGR3. However, expression of AGR2 had a significant impact on remodelling the cellular proteome using a triple-labelled SILAC protocol. 29 045 peptides were detected for the identification and relative quantitation of 3003 proteins across the experimental conditions. Ingenuity Pathway annotation highlighted the dominant pathway suppressed by wt-AGR2 was the p53-signalling axis. DNA damage induced p53 stabilization and p21 induction by cisplatin treatment confirmed that wt-AGR2 expression suppressed the p53 pathway. The furthest outlying SILAC protein expression change induced by AGR2 was the anti-viral and cell cycle regulator tumour susceptibility gene 101 (TSG101), confirmed by immunoblotting. Transfection of TSG101 into MCF7 (AGR2+, oestrogen dependent), A549 (AGR2+, oestrogen independent) or A375 (AGR2-) cells confirmed that TSG101 attenuates p53 signalling. These systems wide screens suggest that the most dominant landscape reprogrammed by low levels of AGR2 protein is the cellular proteome, rather than the transcriptome, and provide focus for evaluating its role in proteostasis.

Complex temporal changes in TGFβ oncogenic signaling drive thyroid carcinogenesis in a mouse model

Despite recent advances, understanding of molecular genetic alterations underlying thyroid carcinogenesis remains unclear. One key question is how dynamic temporal changes in global genomic expression affect carcinogenesis as the disease progresses. To address this question, we used a mouse model that spontaneously develops follicular thyroid cancer similar to human cancer (Thrb (PV/PV) mice). Using complementary DNA microarrays, we compared global gene expression profiles of thyroid tumors of Thrb (PV/PV) mice with the age- and gender-matched thyroids of wild-type mice at 3 weeks and at 2, 4, 6 and 14 months. These time points covered the pathological progression from early hyperplasia to capsular invasion, vascular invasion and eventual metastasis. Microarray data indicated that 462 genes were upregulated (Up-cluster genes) and 110 genes were downregulated (Down-cluster genes). Three major expression patterns (trending up, cyclical and spiking up and then down) and two (trending down and cyclical) were apparent in the Up-cluster and Down-cluster genes, respectively. Functional clustering of tumor-related genes followed by Ingenuity Pathways Analysis identified the transforming growth factor β (TGF β)-mediated network as key signaling pathways. Further functional analyses showed sustained activation of TGFβ receptor-pSMAD2/3 signaling, leading to decreased expression of E-cadherin and increased expression of fibronectin, vimentin, collagens and laminins. These TGFβ-induced changes facilitated epithelial-to-mesenchymal transition, which promotes cancer invasion and migration. Thus, complex temporal changes in gene expression patterns drive thyroid cancer progression, and persistent activation of TGFβ-TGFRβII-pSMAD2/3 signaling leads to EMT, thus promoting metastasis. This study provides new understanding of progression and metastatic spread of human thyroid cancer.

The estrogen-regulated anterior gradient 2 (AGR2) protein in breast cancer: a potential drug target and biomarker

Initially discovered as an estrogen-responsive gene in breast cancer cell lines, anterior gradient 2 (AGR2) is a developmentally regulated gene belonging to the protein disulfide isomerase (PDI) gene family. Developmentally, AGR2 is expressed in the mammary gland in an estrogen-dependent manner, and AGR2 knockout and overexpression mouse models indicate that the gene promotes lobuloalveolar development by stimulating cell proliferation. Although AGR2 overexpression alone seems insufficient for breast tumorigenesis in mice, several lines of investigations suggest that AGR2 promotes breast tumorigenesis. Overexpression of AGR2 in several breast cancer cell lines increases cell survival in clonogenic assays and cell proliferation, whereas AGR2 loss of function leads to decreased cell cycle progression and cell death. In addition, AGR2 was shown to promote metastasis of breast epithelial cells in an in vivo metastasis assay. As a PDI, AGR2 is thought to be involved in the unfolded protein response that alleviates endoplasmic reticulum stress. Since cancer has to overcome proteotoxic stress due to excess protein production, AGR2 may be one of many pro-survival factors recruited to assist in protein folding or degradation or both. When AGR2 is secreted, it plays a role in cellular adhesion and dissemination of metastatic tumor cells. In breast cancer, AGR2 expression is associated with estrogen receptor (ER)-positive tumors; its overexpression is a predictor of poor prognosis. The AGR2 gene is directly targeted by ER-alpha, which is preferentially bound in tumors with poor outcome. Whereas aromatase inhibitor therapy decreases AGR2 expression, tamoxifen acts as an agonist of AGR2 expression in ER-positive tumors, perhaps contributing to tamoxifen resistance. AGR2 is also overexpressed in a subset of ER-negative tumors. Furthermore, AGR2 expression is associated with the dissemination of metastatic breast cancer cells and can be used as a marker to identify circulating tumor cells and metastatic cells in sentinel lymph nodes. In conclusion, AGR2 is a promising drug target in breast cancer and may serve as a useful prognostic indicator as well as a marker of breast cancer metastasis.