v-Myb represses the transcription of Ets-2

Polymorphisms of TP53 are markers of bladder cancer vulnerability and prognosis

OBJECTIVES

We have reported previously that the TP53 codon72 polymorphism (rs1042522) is associated with the incidence and invasiveness of bladder cancer in a Han Chinese population. Using an enlarged sample, we investigated the role of rs1042522 and of tagSNPs that were predicted to be in linkage disequilibrium with codon72 in relation to the incidence, invasiveness, and prognosis of bladder cancer.

METHODS AND MATERIALS

A sample of 201 patients and 311 controls without cancer were genotyped for 5 tagSNPs using tetra-primer ARMS and/or an allele-specific PCR technique.

RESULTS

The genotyped data were analyzed using Haploview 4.2, and a 10,000-permutation test showed that the rs9895829G allele (P = 0.003) and the rs1788227C allele (P = 0.027) were both associated with the incidence of bladder cancer. With respect to haplotype associations, after the data were adjusted for age, the haplotypes GTT (P = 0.001) and GGTC (P < 0.001) were correlated with a low incidence of bladder cancer. In contrast, none of the TP53 haplotypes were associated significantly with high tumor grade or muscle invasiveness. On the basis of Cox regression analysis, haplotype CGCC and invasiveness were associated with cancer-related death. Structural equation modeling showed that haplotypes GGCC and CGCC played opposing roles with respect to bladder cancer-related death; haplotype GGCC was a protective factor, whereas haplotype CGCC was a risk factor.

CONCLUSIONS

The TP53 codon72 polymorphism appears to play a crucial role in determining the association between TP53 haplotype and the incidence and prognosis of bladder cancer. Further functional assays to confirm whether these TP53 haplotypic variants interact with the proteins N-Myc and NDRG is necessary.

MiR-148a promotes apoptosis by targeting Bcl-2 in colorectal cancer

Apoptosis has a vital role in maintaining tissue homeostasis, and dysregulation of the apoptotic pathway is now widely recognized as a key step in tumourigenesis. Increasingly, evidence has demonstrated that microRNA (miRNA) can exert various biological functions in tumours by targeting oncogenes or tumour suppressors. Nevertheless, the role of miRNA in apoptosis remains unclear. Here we show that ectopical expression of miR-148a can induce apoptosis in colorectal cancer cells. In addition, MYB can inhibit miR-148a by directly acting on the transcription factor binding site in miR-148a gene and miR-148a can posttranscriptionally silence Bcl-2. Subsequently, the intrinsic apoptosis pathway is activated by releasing cytochrome c, cleaving caspase 9, caspase 3 and PARP, which eventually induce cancer-cell apoptosis. These findings are part of a hitherto undocumented apoptotic regulatory pathway in which a pleiotropic transcription factor controls the expression of a miRNA and the miRNA inhibits the target, leading to activation of an intrinsic mitochondrial pathway and tumour apoptosis.

Genomic tools for dissecting oncogenic transcriptional networks in human leukemia

Chromatin immunoprecipitation (ChIP)-chip and ChIP-seq technologies are rapidly expanding our capacity to interrogate the location of transcription factor-binding sites in the human genome and to map the pattern of chromatin modifications associated with the regulation of gene expression. The application of these techniques to the study of hematologic malignancies will complement gene expression profiling studies to elucidate the structure and function of oncogenic transcriptional networks involved in the pathogenesis of leukemias and lymphomas.

MYB function in normal and cancer cells

The transcription factor MYB has a key role as a regulator of stem and progenitor cells in the bone marrow, colonic crypts and a neurogenic region of the adult brain. It is in these compartments that a deficit in MYB activity leads to severe or lethal phenotypes. As was predicted from its leukaemogenicity in several animal species, MYB has now been identified as an oncogene that is involved in some human leukaemias. Moreover, recent evidence has strengthened the case that MYB is activated in colon and breast cancer: a block to MYB expression is overcome by mutation of the regulatory machinery in the former disease and by oestrogen receptor-alpha (ERalpha) in the latter.