Myc, Aurora Kinase A, and mutant p53(R172H) co-operate in a mouse model of metastatic skin carcinoma.

Clinical observations, as well as data obtained from the analysis of genetically engineered mouse models, firmly established the gain-of-function (GOF) properties of certain p53 mutations. However, little is known about the underlying mechanisms. We have used two independent microarray platforms to perform a comprehensive and global analysis of tumors arising in a model of metastatic skin cancer progression, which compares the consequences of a GOF p53(R172H) mutant vs p53 deficiency. DNA profiling revealed a higher level of genomic instability in GOF vs loss-of-function (LOF) p53 squamous cell carcinomas (SCCs). Moreover, GOF p53 SCCs showed preferential amplification of Myc with a corresponding increase in its expression and deregulation of Aurora Kinase A. Fluorescent in situ hybridization confirmed amplification of Myc in primary GOF p53 SCCs and its retention in metastatic tumors. We also identified by RNA profiling distinct gene expression profiles in GOF p53 tumors, which included enriched integrin and Rho signaling, independent of tumor stage. Thus, the progression of GOF p53 papillomas to carcinoma was marked by the acquisition of epithelial-to-mesenchymal transition and metastatic signatures. In contrast, LOF p53 tumors showed enrichment of genes associated with cancer proliferation and chromosomal instability. Collectively, these observations suggest that genomic instability has a prominent role in the early stages of GOF p53 tumor progression (that is, papillomas), whereas it is implicated at a later stage in LOF p53 tumors (that is, SCCs). This model will allow us to identify specific targets in mutant p53 SCCs, which may lead to the development of new therapeutic agents for the treatment of metastatic SCCs.

Sistematização da assistência de enfermagem a pacientes crônicos / Systematization of nursing care to chronic patients

As doenças crônicas são definidas como doenças cardiovasculares e cerebrovasculares, neoplasias, doenças respiratórias crônicas e diabetes mellitus. A sistematização da Assistência de Enfermagem está incluída no processo de enfermagem...(AU)

Sistematização da assistência de enfermagem a pacientes crônicos / Systematization of nursing care to chronic patients

As doenças crônicas são definidas como doenças cardiovasculares e cerebrovasculares, neoplasias, doenças respiratórias crônicas e diabetes mellitus. A sistematização da Assistência de Enfermagem está incluída no processo de enfermagem...

p53-dependent senescence delays Emu-myc-induced B-cell lymphomagenesis.

The effect of p53-dependent cell-cycle arrest and senescence on Emu-myc-induced B-cell lymphoma development remains controversial. To address this question, we crossed Emu-myc mice with the p53(515C) mutant mouse, encoding the mutant p53R172P protein that retains the ability to activate the cell-cycle inhibitor and senescence activator p21. Importantly, this mutant lacks the ability to activate p53-dependent apoptotic genes. Hence, Emu-myc mice that harbor two p53(515C) alleles are completely defective for p53-dependent apoptosis. Both Emu-myc::p53(515C/515C) and Emu-myc::p53(515C/+) mice survive significantly longer than Emu-myc::p53(+/-) mice, indicating the importance of the p53-dependent non-apoptotic pathways in B-cell lymphomagenesis. In addition, the p53(515C) allele is deleted in several Emu-myc::p53(515C/+) lymphomas, further emphasizing the functionality of p53R172P in tumor inhibition. Lymphomas from both Emu-myc::p53(515C/515C) and Emu-myc::p53(515C/+) mice retain the ability to upregulate p21, resulting in cellular senescence. Senescence-associated beta-galactosidase (SA beta-gal) activity was observed in lymphomas from Emu-myc::p53(+/+), Emu-myc::p53(515C/515C) and Emu-myc::p53(515C /+) mice but not in lymphomas isolated from Emu-myc::p53(+/-) mice. Thus, in the absence of p53-dependent apoptosis, the ability of p53R172P to induce senescence leads to a significant delay in B-cell lymphoma development.

Mtbp haploinsufficiency in mice increases tumor metastasis.

Mdm2 inhibits the function of the p53 tumor suppressor. Mdm2 is overexpressed in many tumors with wild-type p53 suggesting an alternate mechanism of loss of p53 activity in tumors. An Mdm2-binding protein (MTBP) was identified using a yeast two-hybrid screen. In tissue culture, MTBP inhibits Mdm2 self-ubiquitination, leading to stabilization of Mdm2 and increased degradation of p53. To address the role of MTBP in the regulation of the p53 pathway in vivo, we deleted the Mtbp gene in mice. Homozygous disruption of Mtbp resulted in early embryonic lethality, which was not rescued by loss of p53. Mtbp+/- mice were not tumor prone. When mice were sensitized for tumor development by p53 heterozygosity, we found that the Mtbp+/-p53+/- mice developed significantly more metastatic tumors (18.2%) as compared to p53+/- mice (2.6%). Results of in vitro migration and invasion assays support the in vivo findings. Downmodulation of Mtbp in osteosarcoma cells derived from p53+/- mice resulted in increased invasiveness, and overexpression of Mtbp in Mtbp+/-p53+/- osteosarcoma cells inhibited invasiveness. These results suggest that MTBP is a metastasis suppressor. These results advance our understanding of the cellular roles of MTBP and raise the possibility that MTBP is a novel therapeutic target for metastasis.

The p53-Mdm2 network in progenitor cell expansion during mouse postnatal development.

Mdm2, an E3 ubiquitin ligase, negatively regulates the tumour suppressor p53. Loss of Mdm2 in mice results in p53-dependent apoptosis and embryonic lethality. This phenotype was rescued by the p53(515C) allele, which encodes an apoptosis-deficient p53R172P protein. However, these mice died within 2 weeks of birth, due to a severe impairment of progenitor cell expansion during postnatal haematopoiesis and cerebellar development, leading to p53-dependent cell cycle arrest. Loss of Mdm2 led to phosphorylation of the p53R172P protein, p53R172P stability and activation of the cell cycle inhibitor p21 in proliferating cells, but not in differentiated cells, in multiple tissue compartments. Proliferating cells of epithelial origin were not affected. The haematopoietic and neural defects were alleviated in mice lacking Mdm2 and containing one p53(515C) and one p53-null allele, but spermatogenesis was arrested. These findings establish a crucial role for the p53-Mdm2 network in regulating proliferation and progenitor expansion in many cell lineages and have important implications for the use of drugs that aim to disrupt the p53-Mdm2 interaction.

Creatine kinase isoenzymes specificities: histidine 65 in human CK-BB, a role in protein stability, not in catalysis.

Creatine kinases (CK) play a prominent role in cell energy distribution through an energy shuttle between mitochondria and other organelles. Human brain CK was cloned and overexpressed in COS-7 cells. We then deleted His-65 and/or Pro-66 situated near the center of a flexible loop as shown by X-ray crystallography on mitochondrial and cytosolic CK. The DeltaH65 mutant had nearly the same affinity for its substrates as wild isoenzyme, but its stability was very low. Unlike DeltaH65, DeltaH65P66 had a eightfold decreased affinity for creatine phosphate and was unable to dephosphorylate cyclocreatine phosphate. Our results demonstrate that, despite an overall similar shape of the proteins, this loop accounts for some subtle differences in isoenzyme functions.