During the evolution of cancer, the incipient tumour experiences 'oncogenic stress', which evokes a counter-response to eliminate such hazardous cells. However, the nature of this stress remains elusive, as does the inducible anti-cancer barrier that elicits growth arrest or cell death. Here we show that in clinical specimens from different stages of human tumours of the urinary bladder, breast, lung and colon, the early precursor lesions (but not normal tissues) commonly express markers of an activated DNA damage response. These include phosphorylated kinases ATM and Chk2, and phosphorylated histone H2AX and p53. Similar checkpoint responses were induced in cultured cells upon expression of different oncogenes that deregulate DNA replication. Together with genetic analyses, including a genome-wide assessment of allelic imbalances, our data indicate that early in tumorigenesis (before genomic instability and malignant conversion), human cells activate an ATR/ATM-regulated DNA damage response network that delays or prevents cancer. Mutations compromising this checkpoint, including defects in the ATM-Chk2-p53 pathway, might allow cell proliferation, survival, increased genomic instability and tumour progression.

Purpose: Cisplatin-containing chemotherapy is the standard of care for patients with locally advanced and metastatic transitional cell carcinoma of the urothelium. The response rate is f50% and tumor-derived molecular prognostic markers are desirable for improved estimation of response and survival. Experimental Design: Affymetrix GeneChip expression profiling was carried out using tumor material from 30 patients. A set of genes with an expression highly correlated to survival time after chemotherapy was identified. Two genes were selected for validation by immunohistochemistry in an independent material of 124 patients receiving cisplatin-containing therapy. Results: Fifty-five differentially expressed genes correlated significantly to survival time. Two of the protein products (emmprin and survivin) were validated using immunohistochemistry.Multivariate analysis identified emmprin expression (hazard ratio, 2.23; P < 0.0001) and survivin expression (hazard ratio, 2.46; P < 0.0001) as independent prognostic markers for poor outcome, together with the presence of visceral metastases (hazard ratio, 2.62; P <0.0001). In the clinical good prognostic group of patients without visceral metastases, both markers showed significant discriminating power as supplemental risk factors (P < 0.0001). Within this group of patients, the subgroups of patients with no positive, one positive, or two positive immunohistochemistry scores (emmprin and survivin) had estimated 5-year survival rates of 44.0%, 21.1%, and 0%, respectively. Response to chemotherapy couldalso be predicted with anodds ratio of 4.41 (95% confidenceinterval,1.91-10.1) and 2.48 (95% confidence interval,1.1-5.5) for emmprin and survivin, respectively. Conclusions: Emmprin and survivin proteins were identified as strong independent prognostic factors for response and survival after cisplatin-containing chemotherapy in patients with advanced bladder cancer.

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Checkpoint kinase 2 (Chk2) is a tumour suppressor and signal transducer in genome integrity checkpoints that coordinate cell-cycle progression with DNA repair or cell death in response to DNA damage. Defects of Chk2 occur in subsets of diverse sporadic malignancies and predispose to several types of hereditary carcinomas. However, the status of Chk2 in tumours of the urinary bladder remains unknown. Here, we report that among 58 advanced (grade T2-T4) human bladder carcinomas, immunohistochemical analysis revealed tumour-specific reduction or lack of Chk2 protein in 6 (10.3%) cases. Genetic analysis of the latter subset showed that a Chk2-negative carcinoma #668 harboured a truncating mutation 1100delC, in one Chk2 allele and loss of the corresponding second allele. The 1100delC mutation was also found in the germ line of this patient. Sequencing of TP53 in tumour #668 identified two missense mutations. Furthermore, the vast majority of the tumours showed 'unscheduled' activatory phosphorylation on Thr68 of Chk2 in the absence of any DNA-damaging treatment. Our results indicate that the otherwise dormant DNA damage signal transducer Chk2 is aberrantly and constitutively activated in invasive urinary bladder carcinomas, and that such likely proapoptotic checkpoint signalling can be disabled by inactivation of Chk2 and/or p53 tumour suppressors in subsets of these tumours.

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