p53 Signaling on Microenvironment and Its Contribution to Tissue Chemoresistance.

Chemoresistance persists as a significant, unresolved clinical challenge in many cancer types. The tumor microenvironment, in which cancer cells reside and interact with non-cancer cells and tissue structures, has a known role in promoting every aspect of tumor progression, including chemoresistance. However, the molecular determinants of microenvironment-driven chemoresistance are mainly unknown. In this review, we propose that the TP53 tumor suppressor, found mutant in over half of human cancers, is a crucial regulator of cancer cell-microenvironment crosstalk and a prime candidate for the investigation of microenvironment-specific modulators of chemoresistance. Wild-type p53 controls the secretion of factors that inhibit the tumor microenvironment, whereas altered secretion or mutant p53 interfere with p53 function to promote chemoresistance. We highlight resistance mechanisms promoted by mutant p53 and enforced by the microenvironment, such as extracellular matrix remodeling and adaptation to hypoxia. Alterations of wild-type p53 extracellular function may create a cascade of spatial amplification loops in the tumor tissue that can influence cellular behavior far from the initial oncogenic mutation. We discuss the concept of chemoresistance as a multicellular/tissue-level process rather than intrinsically cellular. Targeting p53-dependent crosstalk mechanisms between cancer cells and components of the tumor environment might disrupt the waves of chemoresistance that spread across the tumor tissue, increasing the efficacy of chemotherapeutic agents.

3-D Endoluminal Ultrasound Biomicroscopic Imaging and Volumetry of Mouse Colon Tumors.

Currently, colonoscopy is considered the gold standard procedure for diagnosis of colorectal cancer (CRC), the third most common cancer in the United States. However, this technique fails to detect flat adenomas, serrated polyps and advanced adenomas, with miss rates of 34%, 27% and 14%, respectively. These miss rates, more frequent than previously supposed, suggest the need for new CRC screening tools. In the work described here, the potential application of a 40-MHz ultrasound system to generate a sequence of 2-D endoluminal ultrasound biomicroscopy (eUBM-2-D) images of a mouse model of colon cancer was investigated, and this image sequence was used to render eUBM-3-D images and to measure tumor volume. The technique was validated with tissue-mimicking phantoms and used in vivo with mice bearing colon polypoid tumors. Estimated volumes ranged from 0.174-7.909 mm3 for targets in validation phantoms and from 0.066-6.082 mm3 for mouse colon tumors.

Detection of Mice Colorectal Tumors by Endoluminal Ultrasound Biomicroscopic Images and Quantification of Image Augmented Gray Values Following Injection of VEGFR-2 Targeted Contrast Agent.

RATIONALE AND OBJECTIVES: Ultrasound biomicroscopy (UBM) is a noninvasive imaging technique that can be applied in detecting colonic tumors and, once associated with an ultrasound contrast agent (UCA), can identify the molecular expression of cancer-related biomarkers, such as the vascular endothelial growth factor receptor 2 (VEGFR-2). The present work aimed to detect colonic tumors and quantify augmented gray values of endoluminal UBM (eUBM) images from colonic tumors following the injection of VEGFR-2 targeted UCA (VEGFR2-UCA) into a mouse model of colorectal cancer. MATERIAL AND METHODS: A 40 MHz miniprobe catheter inserted through the biopsy channel of a pediatric flexible bronchofiberscope was used to obtain colonoscopic and B-mode eUBM images simultaneously. Seventeen tumor-bearing mice had their colons inspected and six of them were subjected to a VEGFR2-UCA injection to predict VEGFR-2 expression. RESULTS: All animals developed distal colon tumors and eUBM was able to detect all of them and also to characterize the tumors, with 71.4% being in situ lesions and 28.6% being tumors invading the mucosa + muscularis mucosae + submucosa layers, as confirmed by histopathology. After VEGFR2-UCA injection, gray values from the eUBM tumoral images increased significantly (p < 0.01). Tumor sites with increased eUBM image gray values corresponded to areas with increased VEGFR-2 expression, as confirmed by immunohistochemistry. CONCLUSION: The results confirm eUBM as a powerful noninvasive and real-time tool for detecting colon tumor and its invasiveness and once associated with VEGFR2-UCA may become a tool for the detection of VEGFR-2 expression in colonic tumors.

Zika virus infection leads to mitochondrial failure, oxidative stress and DNA damage in human iPSC-derived astrocytes.

Zika virus (ZIKV) has been extensively studied since it was linked to congenital malformations, and recent research has revealed that astrocytes are targets of ZIKV. However, the consequences of ZIKV infection, especially to this cell type, remain largely unknown, particularly considering integrative studies aiming to understand the crosstalk among key cellular mechanisms and fates involved in the neurotoxicity of the virus. Here, the consequences of ZIKV infection in iPSC-derived astrocytes are presented. Our results show ROS imbalance, mitochondrial defects and DNA breakage, which have been previously linked to neurological disorders. We have also detected glial reactivity, also present in mice and in post-mortem brains from infected neonates from the Northeast of Brazil. Given the role of glia in the developing brain, these findings may help to explain the observed effects in congenital Zika syndrome related to neuronal loss and motor deficit.

Immunohistochemical analysis of retinoblastoma and ß-catenin as an assistant tool in the differential diagnosis between Crohn's disease and ulcerative colitis.

In about 10-15% of patients with inflammatory bowel diseases (IBD) there is no clear definitive differential diagnosis between Crohn's disease (CD) and ulcerative colitis (UC) and the disease is classified as indeterminate colitis. Since pharmacological and surgical treatments differ in CD and UC, establishing a correct diagnosis is critical. The aim of this work was to access the expression profile of proteins involved in colonic inflammation and cancer in samples from CD and UC. For that, colon samples from 24 CD, 21 UC and 10 control patients were processed for immunohistochemistry using anti-phosphorylated RB at Ser(807/811) and anti-ß-catenin. Crypts were blinded, analyzed and counted for phosphorylated RB-positive (phospho-RB) cells or scored for positive ß-catenin staining. Western blot was used for confirming immuhistochemical results: RB phosphorylation was significantly greater in colon samples from patients with CD compared with UC (p<0.005). In contrast, the expression of ß-catenin was significantly increased in UC compared with CD (p<0.005) samples. Phospho-RB and ß-catenin are negatively correlated (CC: -0.573; p = 0.001). A positive phospho-RB test yielded high levels of sensitivity, specificity, negative and positive predictive values, and accuracy for the diagnosis of CD against UC. This work indicates that RB phosphorylation and ß-catenin nuclear translocation are differently expressed in CD and UC, and provide novel insights into the pathogenic mechanisms of IBD. In particular, rates of phospho-RB-positive cells in mucosal samples emerge as a promising tool for the differential diagnosis of patients with IBD.

DNA damage-induced cell death: lessons from the central nervous system.

DNA damage can, but does not always, induce cell death. While several pathways linking DNA damage signals to mitochondria-dependent and -independent death machineries have been elucidated, the connectivity of these pathways is subject to regulation by multiple other factors that are not well understood. We have proposed two conceptual models to explain the delayed and variable cell death response to DNA damage: integrative surveillance versus autonomous pathways. In this review, we discuss how these two models may explain the in vivo regulation of cell death induced by ionizing radiation (IR) in the developing central nervous system, where the death response is regulated by radiation dose, cell cycle status and neuronal development.

Signal-dependent protection from apoptosis in mice expressing caspase-resistant Rb.

The retinoblastoma tumour suppressor protein RB is cleaved by caspases during apoptosis. Here we have mutated the caspase cleavage site in the carboxy terminus of the murine Rb protein in the mouse germ line to create the Rb-MI allele. After endotoxic shock, expression of Rb-MI inhibits apoptosis in the intestines, but not in the spleen, and promotes the survival of male mice. Fibroblasts expressing Rb-MI protein are protected from apoptosis induced by the tumour-necrosis factor-alpha type I receptor (TNFRI) but remain sensitive to cell death induced by DNA damage. Correspondingly, the release of cytochrome c and the activation of caspase-3 induced by TNFRI, but not by DNA damage, are defective in cells expressing Rb-MI. Our results highlight the importance of Rb cleavage in TNFRI-induced apoptosis.