ABSTRACT
We investigated the status of the PI 3-kinase/AKT/PTEN signaling pathway in a series of 117 head and neck squamous cell carcinomas (HNSCC) in a search for molecular alterations in genes/proteins with potential prognostic value. For this purpose, PIK3CA and AKT2 gene amplification was assessed by multiplex and Quantitative Real-Time PCR. Protein expression of AKT, p-AKT, p110alpha and PTEN was determined by Western blot. PTEN allelic loss was evaluated by microsatellite analysis. PTEN-exon 5 was screened for point mutations by PCR-SSCP. Homozygous deletions were determined by multiplex PCR. PIK3CA gene was amplified in 43/117 (37%) fresh tumor samples, a frequency that did not differ from that found in archival premalignant tissues: 15/38 (39%); 12/40 (30%) fresh tumors harbored AKT2 gene amplification. AKT was found activated in 6/36 (17%) fresh tumor samples, when compared to their normal tissue counterparts. Of these 6 cases, 1 showed p110alpha overexpression and 5 displayed PTEN protein downregulation. Neither allelic loss (found in 11/77 informative cases) nor point mutations or homozygous deletions accounted for the reduced PTEN protein expression observed in our tumor series. The histologically normal mucosa of 4 patients displayed some of the molecular alterations analyzed. Dysregulation of the PI 3-K/AKT/PTEN pathway might contribute to early HNSCC tumorigenesis and might constitute a potential clinical target. Overall, 17/36 (47%) cases showed at least 1 of the molecular alterations studied here, which makes the PI 3-kinase-initiated signaling pathway one of the most frequently altered in HNSCC.
Subject(s)
Carcinoma, Squamous Cell/genetics , Head and Neck Neoplasms/genetics , Phosphatidylinositol 3-Kinases/genetics , Phosphoric Monoester Hydrolases/genetics , Protein Serine-Threonine Kinases/genetics , Proto-Oncogene Proteins/genetics , Tumor Suppressor Proteins/genetics , Base Sequence , Carcinoma, Squamous Cell/pathology , Carcinoma, Squamous Cell/surgery , DNA, Neoplasm/genetics , DNA, Neoplasm/isolation & purification , Female , Gene Amplification , Gene Deletion , Head and Neck Neoplasms/pathology , Head and Neck Neoplasms/surgery , Humans , Male , PTEN Phosphohydrolase , Phosphatidylinositol 3-Kinases/metabolism , Phosphoric Monoester Hydrolases/metabolism , Polymerase Chain Reaction , Polymorphism, Single-Stranded Conformational , Protein Serine-Threonine Kinases/metabolism , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins c-akt , Tumor Suppressor Proteins/metabolismABSTRACT
BACKGROUND: Aberrations of the p53 gene and overexpression of its protein are widely recognized markers of malignancy including oral squamous cell carcinomas. This study was performed to evaluate the relationship of immunoexpression of p53 protein in series of 91 squamous cell carcinomas of the oral cavity with clinicopathologic parameters and to investigate whether p53 immunoexpression might influence the clinical outcome of the disease. METHODS: From a group of 287 consecutive patients, 91 surgically treated ones were randomly selected. P53 protein expression was investigated by means of immunohistochemistry. Clinical and histopathologic data were gathered, and the patient survival was analyzed. RESULTS: Of the oral carcinomas, 52.7% (n = 48) overexpressed p53, using a threshold of 10% stained cell nuclei. There was a negative correlation of p53 immunoexpression with a histologic grade of differentiation (r = -0.236, p =.06) but not with clinical variables. Overall survival rate was 59% at 5 years. In univariate analysis, tumor size, node status, and advanced clinical stage were significantly associated with shortened overall survival. In patients without neck node metastases, p53 showed a strong correlation with survival (p =.01). In multivariate analysis performed only on N0 patients, tumor extension and p53 immunoexpression were found to be the only independent prognostic parameters with relative risks of 1.9 and 4.3, respectively. CONCLUSIONS: A strong relationship was observed between p53 immunoexpression and poor prognosis in patients with oral squamous cell carcinomas without neck node metastases.
