Μελέτη του γονιδίου APC και της έκφρασης της β-κατενίνης σε ασθενείς με καρκίνο του ουροθηλίου που υποβλήθηκαν σε χημειοθεραπεία με carboplatin και paclitaxel μετά από κυστεκτομή: συσχέτιση των γενετικών μεταβολών του APC με την συσσώρευση της β-κατενίνης και η προγνωστική τους σημασία

Abstract

Urothelial cancer (UC) is a common malignancy. The standard treatment for muscle-invasive bladder cancer is radical cystectomy however relapses are common. Adding systemic adjuvant chemotherapy has been used in order to improve prognosis but not all patients benefit from this treatment. Thus, markers that can improve our ability to select patients most probably to benefit are highly desirable. The expression of biologically important molecular factors may be used to define groups of patients with different prognosis and, hence, requiring different therapeutic approaches. The canonical Wnt/beta-catenin signalling pathway plays an important role in embryogenesis and cell fate determination but it has also been implicated in tumorigenesis. The role of Wnt pathway in urothelial carcinogenesis has not been extensively studied and conflicting results have been published regarding the presence of mutations in key regulators of the pathway, like APC and b-catenin. Within this context, we performed a mutational analysis in APC and searched for subsequent alterations in b-catenin expression and their relationships with other markers of proliferation, apoptosis and angiogenesis in patients with muscle invasive disease treated with cystectomy and adjuvant chemotherapy. Paraffin embedded tissue blocks from the cystectomies of patients with muscle invasive disease were collected. All patients were at high risk for relapse, i.e. pathological stages pT3b, pT4a or had histologically involved regional lymph nodes and there was no evidence of distant metastases and had received adjuvant chemotherapy with the combination of paclitaxel and carboplatin. Direct sequencing of the MCR region of APC of 70 patients revealed mutations in 11 (16%) patients (9 with point missesnse mutations and 2 with frameshift base deletions). Furthermore nonsense SNPs were found in ~80%. There was no correlation of mutations in APC and Immunohistochemistry findings for p53, Ki-67, Bcl-2 , COX-2 , b-catenin , VEGF and MVD. Patients with either APC mutations or accumulation of b-catenin had shorter disease free interval (13.4 vs 28. months) than patients without mutations and with normal or reduced staining for b-catenin (p=0.07). Patients with reduced b-catenin staining had significantly better overall survival than patients with normal or nuclear accumulation of b-catenin (not reached vs 24 months, p=0.05). The interaction of APC missense mutations with b-catenin nuclear accumulation identified groups with significantly different outcome: 23 (32%) patients had either APC missense mutations or nuclear accumulation of b-catenin and they had significantly worse survival (60.5 vs 20.6 months, p=0.03) than patients without mutations who had normal or reduced b-catenin staining. . In multivariate analysis both the presence of APC missense mutation or b-catenin accumulation (p=0.048) and positive surgical margins (p=0.01) were significant predictors of survival. Our results provide for the first time mutational data for APC in muscle invasive disease and identify patients with muscle invasive urothelial cancer with worse outcome due to modulations in Wnt signalling pathway