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.

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.