Mitogen-activated protein (MAP) kinase cascades represent one of the major signal systems used by eukaryotic cells to transduce extracellular signals into cellular responses. Four MAP kinase subgroups have been identified in humans: ERK, JNK (SAPK), ERK5 (BMK), and p38. Here we characterize a new MAP kinase, p38␤. p38␤ is a 372-amino acid protein most closely related to p38. It contains a TGY dual phosphorylation site, which is required for its kinase activity. Like p38, p38␤ is activated by proinflammatory cytokines and environmental stress. A comparison of events associated with the activation of p38␤ and p38 revealed differences, most notably in the preferred activation of p38␤ by MAP kinase kinase 6 (MKK6), whereas p38 was activated nearly equally by MKK3, MKK4, and MKK6. Moreover, in vitro and in vivo experiments showed a strong substrate preference by p38␤ for activating transcription factor 2 (ATF2). Enhancement of ATF2-dependent gene expression by p38␤ was ϳ20-fold greater than that of p38 and other MAP kinases tested. The data reported here suggest that while closely related, p38␤ and p38 may be regulated by differing mechanisms and may exert their actions on separate downstream targets.

SUMMARY The tumor stroma is believed to contribute to some of the most malignant characteristics of epithelial tumors. However, signaling between stromal and tumor cells is complex and remains poorly understood. Here we show that the genetic inactivation of Pten in stromal fibroblasts of mouse mammary glands accelerated the initiation, progression and malignant transformation of mammary epithelial tumors. This was associated with the massive remodeling of the extra-cellular matrix (ECM), innate immune cell infiltration and increased angiogenesis. Loss of Pten in stromal fibroblasts led to increased expression, phosphorylation (T72) and recruitment of Ets2 to target promoters known to be involved in these processes. Remarkably, Ets2 inactivation in Pten stroma-deleted tumors ameliorated disruption of the tumor microenvironment and was sufficient to decrease tumor growth and progression. Global gene expression profiling of mammary stromal cells identified a Pten-specific signature that was highly represented in the tumor stroma of breast cancer patients. These findings identify the Pten-Ets2 axis as a critical stroma-specific signaling pathway that suppresses mammary epithelial tumors.

We developed stromal-and epithelial-specific cre-transgenic mice to directly visualize epithelial-mesenchymal transition (EMT) during cancer progression in vivo. Using three different oncogene-driven mouse mammary tumor models and cell-fate mapping strategies, we show in vivo evidence for the existence of EMT in breast cancer and show that myc can specifically elicit this process. Hierarchical cluster analysis of genomewide loss of heterozygosity reveals that the incidence of EMT in invasive human breast carcinomas is rare, but when it occurs it is associated with the amplification of MYC. These data provide the first direct evidence for EMT in breast cancer and suggest that its development is favored by myc-initiated events. [Cancer Res 2008;68(3):937-45]

The ras/Raf/Mek/Erk pathway plays a central role in coordinating endothelial cell activities during angiogenesis. Transcription factors Ets1 and Ets2 are targets of ras/Erk signaling pathways that have been implicated in endothelial cell function in vitro, but their precise role in vascular formation and function in vivo remains ill-defined. In this work, mutation of both Ets1 and Ets2 resulted in embryonic lethality at midgestation, with striking defects in vascular branching having been observed. The action of these factors was endothelial cell autonomous as demonstrated using Cre/loxP technology. Analysis of Ets1/Ets2 target genes in isolated embryonic endothelial cells demonstrated down-regulation of Mmp9, Bcl-X L , and cIAP2 in double mutants versus controls, and chromatin immunoprecipitation revealed that both Ets1 and Ets2 were loaded at target promoters. Consistent with these observations, endothelial cell apoptosis was significantly increased both in vivo and in vitro when both Ets1 and Ets2 were mutated. These results establish essential and overlapping functions for Ets1 and Ets2 in coordinating endothelial cell functions with survival during embryonic angiogenesis. (Blood. 2009;114:1123-1130) IntroductionAngiogenesis, the biologic process by which endothelial cells (ECs) form new blood vessels from an existing vascular network, is a critical process in normal vertebrate embryonic development, as well as in processes like wound healing and inflammation in adults. Angiogenesis is also an essential element in many pathologic conditions, including cancer. 1,2 Angiogenesis is regulated by a balance of both positive and negative signaling events mediated by growth factors and their receptors as well as by cell adhesion to the extracellular matrix. [1][2][3][4] These complex signaling and cell adhesion interactions alter the growth, migration, survival, and differentiation of ECs through modulation of the intracellular signaling pathways that control these processes. [1][2][3][4][5] Among these pathways, the ras/Raf/Mek/Erk pathway has been proposed to play a central role in coordinating these cellular activities during development and tumor angiogenesis. For example, gene knockouts of B-raf and Mek-1 point to their role in placental vascular formation during extraembryonic development, although their action in embryonic development is redundant. 6,7 Expression of dominant-negative Raf in the tumor vasculature in a transplantation model increases EC apoptosis and decreases tumor growth, 8 and sustained Erk activity is critical for EC migration and angiogenesis in the chick chorioallantoic membrane assay. 9 In cell culture studies, Erk signaling has been implicated in EC survival. [10][11][12] ECs are especially sensitive to apoptotic signals during angiogenesis, and the sustained activation of Erk signaling by the combination of growth factor receptors and integrin adhesion may be important in preventing cell death during this process. 9,10 The downstream targets of Erks that mediate these effects on ECs re...

Matrix metalloproteinases (MMPs) are proteolytic enzymes that regulate various cell behaviors in cancer biology, via their basic function of degradation of proteins. Genetic variations in several MMP promoters may influence transcription and expression of MMPs. The aim of this study is to assess the effects of the two single nucleotide polymorphisms (SNPs), the guanine insertion polymorphism in the MMP1 promoter and the adenosine insertion polymorphism in the MMP3 promoter, on risk of the development and lymphatic metastasis of non-small cell lung carcinoma (NSCLC). The MMP1 and MMP3 SNPs were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis in 243 NSCLC patients and 350 control subjects in North China. The overall genotype and allelotype distribution of both the variants in cancer patients and controls was not significantly different (all P values are above 0.05). However, stratification analysis showed that smoking individuals with the MMP3 5A allele had a >1.5-fold increased risk to develop NSCLC, compared with those harboring the 6A homozygous [the age and gender adjusted odds ratio (OR) = 1.68, 95% confidence interval (CI) = 1.04-2.70]. In addition, the frequency of the MMP3 5A homozygote in NSCLC patients with lymphatic metastasis was significantly higher than that in lymph node negative ones (5.7 versus 0%, P = 0.04). Moreover, the MMP 1G/5A haplotype significantly increased the risk of lymphatic metastasis (OR = 3.36, 95% CI = 1.42-7.94), compared with the 2G/6A haplotype. The present result suggested that the MMP3 promoter polymorphism may modify susceptibility to NSCLC, and the MMP 1G/5A haplotype may predicate the risk of lymphatic metastasis of this tumor.

An A to G transition at the 181 base pair position upstream of the transcription initiation site of the matrix metalloproteinase-7 (MMP-7) gene (-181A/G) may modify the development and progression of some diseases via influencing the transcription activity of the promoter. To assess the effects of the functional single nucleotide polymorphism on cancer susceptibility and progression, the MMP-7 -181A/G genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism analysis among 258 patients with esophageal squamous cell carcinoma (ESCC), 201 patients with gastric cardiac carcinoma (GCA), 243 patients with non-small cell lung carcinoma (NSCLC) and 350 healthy individuals without cancer. The result showed that the frequency of the -181G allele in ESCC, GCA and NSCLC patients was significantly higher than that in healthy controls (P = 0.019, 0.023 and 0.004, respectively). Compared with the A/A genotype, genotypes with the -181G allele (A/G + G/G) significantly increased susceptibility to all three tumors, with adjusted odds ratio of 1.83 (95% CI = 1.12-2.99) for ESCC, 1.96 (95% CI = 1.17-3.29) for GCA and 2.00 (95% CI = 1.23-3.24) for NSCLC. Stratification analysis showed that smoking did not significantly influence the association between the MMP-7-181A/G and GCA or NSCLC, while the -181G allele only significantly increased susceptibility to ESCC among smokers. In addition, association between the -181G allele and susceptibility to ESCC and GCA showed significance only among individuals with family history of upper gastrointestinal cancer. The correlation of the MMP-7-181A/G polymorphism with potential of lymphatic metastasis was not observed in all three tumors. The study suggested that, the MMP-7-181A/G polymorphism might be a candidate marker for predicting individuals who are at higher risk to certain tumors but might not be used to predict potential of lymphatic metastasis in ESCC, GCA and NSCLC.

Maternally expressed gene 3 (MEG3), a long non-coding RNA (lncRNA), has tumor-suppressor properties and its expression is lost in several human tumors. However, its biological role in esophageal squamous cell carcinoma (ESCC) tumorigenesis is poorly defined. The present study determined the role and methylation status of MEG3 in esophageal cancer cells and ESCC clinical specimens, and further observed the competing endogenous RNA (ceRNA) activity of MEG3 in the pathogenesis and development of ESCC. Significant downregulation of MEG3 was detected in esophageal cancer cells and ESCC tissues and the expression level of MEG3 was significantly increased in cancer cells after treated with the DNA methyltransferase inhibitor 5-Aza-dC. Upregulation of MEG3 led to the inhibition of proliferation and invasiveness of the cancer cells. The aberrant promoter hypermethylation of MEG3 indicates silencing of its expression. Furthermore, MEG3 acts as a ceRNA to regulate the expression of E-cadherin and FOXO1 by binding hsa-miR-9. Upregulation of miR-9 was detected in esophageal cancer cell lines and ESCC tissues, and miR-9 promoted esophageal cancer cell proliferation and invasion. Finally, downregulation and hypermethylation of MEG3 was associated with ESCC patients' survival. MEG3 functions as a tumor-suppressive lncRNA and aberrant promoter hypermethylation is critical for MEG3 gene silencing in ESCC. In addition, MEG3 acts as a ceRNA to regulate expression of E-cadherin and FOXO1 by competitively binding miR-9 and may be used as a potential biomarker in predicting ESCC patients' progression and prognosis. .

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