Expression patterns of human DAB2IP protein in fetal tissues

DAB2IP stabilizes p27Kip1 via suppressing PI3K/AKT signaling in clear cell renal cell carcinoma

Renal cell carcinoma (RCC) is the most lethal of the urologic malignancies. We previously discovered that DAB2IP, a novel Ras GTPase-activating protein, was frequently epigenetically silenced in RCC, and DAB2IP loss was correlated with the overall survival of RCC patients. In this study, we determined the biological functions of DAB2IP in clear cell RCC (ccRCC) and its potential mechanisms of action. Correlations between DAB2IP expression level and ccRCC tumor size and patient survival were analyzed, and the results showed that ccRCC patients with high DAB2IP mRNA level exhibited smaller tumor size and better survival than the patients with low DAB2IP. Compared to control, DAB2IP knockdown significantly increased cell proliferation, promoted cell cycle progression in G1/S phase, and decreased p27 expression. Mechanism studies demonstrated that loss of DAB2IP promoted p27 protein phosphorylation, cytosolic sequestration, and subsequently ubiquitination-mediated degradation in ccRCC cells. Further studies confirmed that the proline-rich domain in C terminal (CPR) of DAB2IP suppressed AKT phosphorylation and p27 phosphorylation on S10. Hence, DAB2IP is essential for p27 protein stabilization in ccRCC, which is at less partly mediated by PI3K/AKT signaling pathway.

Pumping the brakes on RAS - negative regulators and death effectors of RAS

Mutations that activate the RAS oncoproteins are common in cancer. However, aberrant upregulation of RAS activity often occurs in the absence of activating mutations in the RAS genes due to defects in RAS regulators. It is now clear that loss of function of Ras GTPase-activating proteins (RasGAPs) is common in tumors, and germline mutations in certain RasGAP genes are responsible for some clinical syndromes. Although regulation of RAS is central to their activity, RasGAPs exhibit great diversity in their binding partners and therefore affect signaling by multiple mechanisms that are independent of RAS. The RASSF family of tumor suppressors are essential to RAS-induced apoptosis and senescence, and constitute a barrier to RAS-mediated transformation. Suppression of RASSF protein expression can also promote the development of excessive RAS signaling by uncoupling RAS from growth inhibitory pathways. Here, we will examine how these effectors of RAS contribute to tumor suppression, through both RAS-dependent and RAS-independent mechanisms.

Block one, unleash a hundred. Mechanisms of DAB2IP inactivation in cancer

One of the most defining features of cancer is aberrant cell communication; therefore, a molecular understanding of the intricate network established among tumor cells and their microenvironment could significantly improve comprehension and clinical management of cancer. The tumor suppressor DAB2IP (Disabled homolog 2 interacting protein), also known as AIP1 (ASK1 interacting protein), has an important role in this context, as it modulates signal transduction by multiple inflammatory cytokines and growth factors. DAB2IP is a Ras-GAP, and negatively controls Ras-dependent mitogenic signals. In addition, acting as a signaling adaptor, DAB2IP modulates other key oncogenic pathways, including TNFα/NF-κB, WNT/β-catenin, PI3K/AKT, and androgen receptors. Therefore, DAB2IP inactivation can provide a selective advantage to tumors initiated by a variety of driver mutations. In line with this role, DAB2IP expression is frequently impaired by methylation in cancer. Interestingly, recent studies reveal that tumor cells can employ other sophisticated mechanisms to disable DAB2IP at the post-transcriptional level. We review the mechanisms and consequences of DAB2IP inactivation in cancer, with the purpose to support and improve research aimed to counteract such mechanisms. We suggest that DAB2IP reactivation in cancer cells could be a strategy to coordinately dampen multiple oncogenic pathways, potentially limiting progression of a wide spectrum of tumors.

Spontaneous Preterm Delivery, Particularly with Reduced Fetal Growth, is Associated with DNA Hypomethylation of Tumor Related Genes

Background

Preterm delivery and sub-optimal fetal growth are associated with each other and affect both mother and infant. Our aim was to determine (i) whether there are detectable differences in DNA methylation between early and late gestation and (ii) whether changes in DNA methylation from entry are associated with spontaneous preterm delivery with and without reduced fetal growth.

Methods

We conducted a case-control study nested within a large prospective cohort. Gene specific methylation was measured by Methyl-Profiler PCR Array in a Human Breast Cancer Signature Panel of 24 genes from maternal peripheral leukocytes genomic DNA at entry and 3^rd trimester (sampled at 16 and 30 weeks of gestation, respectively). Clonal bisulfite DNA sequencing was performed to confirm the changes in selected genes (CYP1B1, GADD45A and CXCL12). Multivariable analysis was used for data analysis.

Results

There was significantly decrease in DNA methylation in 15 of 24 genes during the 3^rd trimester in cases of spontaneous preterm delivery (n=23) as compared to the controls (n=19) (p<0.05–p<0.01 for each gene). Similar results were observed by bisulfite sequencing for 3 genes. The change in DNA methylation between late and early gestation was significantly different in cases (overall decrease in methylation was −4.0 ± 1.5%) compared to the controls (overall increase in methylation was 12.6 ± 2.19%, p<0.0001). A graded pattern of DNA methylation was observed in 15 genes. Cases who delivered preterm with reduced fetal growth had the lowest level of methylation, cases delivering preterm without reduced fetal growth were next and term controls were highest in methylation (p for trend <0.05 to p<0.01 for each gene). Cases of preterm delivery also had significantly lower dietary choline intake.

Conclusions

These data suggest that epigenetic modification is associated with an increased risk of spontaneous preterm delivery, spontaneous preterm delivery with reduced fetal growth in particular.

Expression of estrogen receptor α and β in esophageal squamous cell carcinoma

Estrogen receptors (ERs) are frequently expressed in human tumor tissues. There have been several studies concerning ER expression in esophageal cancers, yet the results are inconsistent, and the prognostic value of the receptors remains unclear. In the present study, we investigated the expression of ER protein and its correlation with clinical features of esophageal squamous cell carcinoma (ESCC) patients. Immunohistochemical staining for the ERs was carried out on paraffin-embedded primary tumor tissue sections from 89 patients with ESCC. Quantitative analyses were performed to determine the prognostic value of the expression of ERs, and Pearson's correlation was used to examine the relationship between ERα and ERβ expression levels. Our results showed that ERα immunoreactivity was significantly lower in ESCC than that in the non-neoplastic epithelium (P=0.0445), whereas the ERβ status was much stronger in ESCC than that in the non-neoplastic epithelium (P=0.0243). A significant inverse correlation was observed between ERα expression and depth of tumor invasion (P=0.0426). Correlation analysis revealed a statistically significant inverse correlation between the expression of ERα and ERβ in ESCC (r=-0.2902, P=0.0058). Kaplan-Meier survival analysis showed that the patients with ERα expression (21/89) had a better outcome than patients without ERα expression (P=0.0280), whereas patients with high ERβ immunoreactivity (44/89) were significantly associated with worse survival (P=0.0366). In conclusion, ERα and ERβ levels were inversely correlated, and the downregulation of ERα and upregulation of ERβ may indicate unfavorable prognosis of ESCC.