MicroRNA-128-2 targets the transcriptional repressor E2F5 enhancing mutant p53 gain of function

Abstract

p53 mutations have profound effects on non-small-cell lung cancer (NSCLC) resistance to chemotherapeutic treatments. Mutant p53 proteins are usually expressed at high levels in tumors, where they exert oncogenic functions. Here we show that p53R175H, a hotspot p53 mutant, induces microRNA (miRNA)-128-2 expression. Mutant p53 binds to the putative promoter of miR128-2 host gene, ARPP21, determining a concomitant induction of ARPP21 mRNA and miR-128-2. miR-128-2 expression in lung cancer cells inhibits apoptosis and confers increased resistance to cisplatin, doxorubicin and 5-fluorouracyl treatments. At the molecular level, miR-128-2 post-transcriptionally targets E2F5 and leads to the abrogation of its repressive activity on p21 waf1 transcription. p21 waf1 protein localizes to the cytoplasmic compartment, where it exerts an anti-apoptotic effect by preventing pro-caspase-3 cleavage. This study emphasizes miRNA-128-2 role as a master regulator in NSCLC chemoresistance. Cell Death and Differentiation (2012) 19, 1038-1048 doi:10.1038/cdd.2011 published online 23 December 2011 Mutations in the TP53 gene are the most frequent type of gene-specific alterations in human cancers. 1 The majority of cancer-associated mutations in TP53 gene are missense mutations that reside mainly in the exons encoding for p53 DNA-binding domain. 2 These mutations frequently result in full-length mutant p53 proteins incapable of activating p53 target genes and suppressing tumorigenesis. 3 Most TP53 mutations can be classified into two main categories according to their effect on the thermodynamic stability of the p53 protein. 4 These two mutation categories are commonly referred to as DNA-contact and conformational mutations. The first group includes mutations in residues directly involved in DNA binding, such as R248Q and R273H. The second group comprises mutations that cause local (such as R249S and G245S) or global (such as R175H and R282W) conformational distortions.Besides losing their wild-type (wt) activities, mutant p53 proteins have also dominant-negative effects that inactivate wt p53 protein expressed from the remaining wt allele. Moreover, some mutant p53 forms also acquire new oncogenic properties -'gain of function' -that overrule those due to loss of wt p53 activity by gene deletion. 5-7 These properties range from enhanced proliferation in culture and resistance to a variety of anticancer drugs commonly used in the clinical practice, to increased tumorigenicity in vivo. [8][9][10] Recent work indicates that mutant p53 protein can augment in vitro and in vivo cell migration and invasion. 11 Fontemaggi et al. 12 showed that mutant p53 increases also the angiogenic potential of cancer cells by modulating, at the transcriptional level, Id4 expression.The existing knowledge regarding the molecular mechanisms whereby mutant p53 regulates gene expression is still lacking. To date, we can depict the three following molecular scenarios to explain gain-of-function of mutant p53 proteins: (i) mutant p53 binds to the promoter of ...

MicroRNA-128-3p is a novel oncomiR targeting PHF6 in T-cell acute lymphoblastic leukemia

“…However, no significant effects on the expression levels of these four genes were detected upon miR-128-3p over-expression in T-ALL cell lines (Online Supplementary Figure S4), thus excluding miR-128-3p from broader interaction in the T-ALL regulatory network. Next, we also looked at other validated miR-128-3p target tumor suppressor genes in other tumor entities including BAX 13 and E2F5 14 (as well as SUZ 1215 and NF1…”

Impact of microRNAs in Resistance to Chemotherapy and Novel Targeted Agents in Non-Small Cell Lung Cancer

“…Recently, Donzelli and collaborators showed that miR-128-2 expression, induced by a mutant p53 protein, inhibits apoptosis and causes increased resistance to doxorubicin, cisplatin and 5-fluorouracil in NSCLC cells. MiR-128-2, by targeting E2F5, inhibits its repressive activity on transcription of p21 waf1 , which exerts an anti-apoptotic effect by reducing pro-caspase-3 cleavage [87]. Additionally, miR-330 expression was correlated with resistance to gemcitabine in various lung cancer cell lines, since gemcitabine-sensitive cells showed a lower expression of miR-330 than gemcitabine-resistant cells.…”

Molecular dynamics of the full-length p53 monomer

“…23 This results in the regulation of cell death 24 or cell cycle. [25][26][27] A relevant metabolic role of p53 is exerted during hypoxia, as oxygen relative pressure reaches particularly lower levels at the center of the tumors, where p53 protein interplays with mTOR 28 as well as with the more classic pathways of HIF-1a and VHL. 29 A distinct role occurs during re-oxygenation, as during miocardial infartion or trombosis in the central nervous system.…”