Adenosine deaminase, a key enzyme in DNA precursors control, is a new p73 target.

The discovery of the p73 and p63 genes, homologous to p53 tumor suppressor has uncovered a family of transcription factors and widened the scenario of cell cycle control and apoptosis. We have identified a putative p53-responsive element in the human adenosine deaminase (ADA) gene, an important enzyme involved in nucleotide metabolism, the deficit of which causes the inhibition of DNA synthesis and repair. Here, we demonstrate that the ectopic expression of p73 isoforms leads to the ADA gene upregulation, showing for the first time a correlation between p73 and ADA. We found that p73 promotes ADA gene expression following a dNTP unbalance generated by ADA enzyme deficiency and 2'deoxyadenosine accumulation. The abrogation of p73 transcriptional activity by the specific dominant-negative p73DD abolishes ADA induction. By contrast, the ADA gene does not appear to be a functional p53 target in the physiological conditions we tested. On the whole, our results contribute to the emerging picture that p73 could play a different role from p53 in normal growth and development by inducing alternative target genes, which are not shared by p53.

Survival outcomes in breast cancer patients with low estrogen/progesterone receptor expression.

INTRODUCTION: The prognostic value of low estrogen and progesterone receptors expression (ER/PgR 1%-10%) in early breast cancer patients is still unclear. PATIENTS AND METHODS: We retrospectively analyzed 1424 consecutive patients with HER2/neu-negative and low endocrine receptors expression early breast cancer, submitted to surgery at the European Institute of Oncology between January 1995 and December 2009. Patients were classified according to the percentage of ER/PgR expression using immunohistochemistry. Group 1 with ER/PgR < 1%, and group 2 with ER/PgR 1% to 10%. RESULTS: Group 1 (ER/PgR < 1%) included 1300 patients, and group 2 (ER/PgR 1%-10%) 124 patients. Median follow-up time was 74 months (range, 3-192 months). The 5-year disease-free survival (DFS) rate was 74% (95% confidence interval [CI], 72%-77%) for group 1, and 79% (95% CI, 70%-86%) for group 2 (P = .16). The 5-year overall survival (OS) rate was 86% (95% CI, 84%-88%) in group 1 and 90% (95% CI, 83%-95%) in group 2 (P = .13). In patients without lymph node involvement, the 5-year OS rate was 92% (95% CI, 89.5%-93.6%) for group 1 and 98% (95% CI, 90.2%-99.8%) for group 2 (P = .061). One hundred ten patients received endocrine therapy with no significant effect on DFS (P = .36) and OS (P = .30). CONCLUSION: The ER/PgR 1%-10% group had a slight, but not statistically significant, better prognosis than the ER/PgR <1% group. Further studies are needed to identify the appropriate clinical approach in this subset of patients with low ER/PgR expression (ER/PgR 1%-10%), HER2-negative early breast cancer.

Connecting p63 to cellular proliferation: the example of the adenosine deaminase target gene.

An unresolved issue regards the role of p73 and p63, the two homologs of the p53 oncosuppressor gene, in normal cells and in tumor development. Specific target genes for each protein need to be identified and characterized in order to understand the specific role of each protein in tumor initiation and progression as well as in oncosuppression and development. We tested whether p63 is implicated in transcriptional events related to sustaining cell proliferation by transactivation of antiapoptotic and cell survival target genes such as Adenosine Deaminase (ADA), an important gene involved in cell proliferation. We demonstrate that ADA is a direct target gene of p63 isoforms. In human keratinocytes, the rate of proliferation and the high level of ADA transcript diminished upon elimination of p63 by small interfering RNA. Reporter assays and chromatin immunoprecipitation experiments indicate a physical interaction of p63 with the two putative p53 binding sites we identified in the ADA gene. Moreover, in response to p53 stabilization and DeltaNp63 downregulation in normal keratinocytes after U.V. treatment, we found a change in the transcriptional pattern of the p53 family target genes, consistent with the different roles played by p53 and p63 in tumor suppression and cellular proliferation. In fact p53 upregulation determined an increase in p21, which in turn mediated the cell cycle arrest, while the downregulation of DeltaNp63 determined a marked decrease in ADA transcript. The experiments reported here support the hypothesis that TAp63 and DeltaNp63 might contribute to tumor genesis not exclusively by antagonizing p53, but by conferring a proliferative potential on cancer cells through the transactivation of target genes indispensable for cell division, such as the Adenosine Deaminase gene.