Abstract B55: The impact of inactivation of p53 and PTEN tumor suppressors on promotion and progression of human non-small cell lung carcinoma

Abstract

Abstract Lung cancer is the major cause of cancer-related death worldwide and the five-year survival rate is not improving significantly, remaining at about 15% for all stages. Inactivation of p53 and PTEN (phosphatase and tensin homolog deleted on chromosome 10) tumor suppressors are molecular events highly related to the pathogenesis of lung cancer, particularly to non-small cell lung carcinoma (NSCLC). However, we still do not have clear image of the sequence of events in NSCLC promotion and progression, that is, whether inactivation of either of these tumor suppressors is early or late event and what the impact of these events is on NSCLC pathogenesis and patients survival. Therefore, we analyzed mutational inactivation of p53 and inactivation of PTEN by loss of heterozygosity (LOH) in 30 NSCLC patients and correlated obtained data with histopathological parameters that are indicators of initiation and progression of the disease: histological subtype, tumor grade, tumor stage, lymph node invasion and necrosis. PCR-single strand conformation polymorphism (PCR-SSCP) analyses revealed and sequencing procedures confirmed that 33.3% of patients had mutationaly inactivated p53 while fragment analysis of PTEN showed that 43.3% had inactivated PTEN by LOH. In total population of analyzed patients, 13.3% of them carried inactivated p53 only, 23.3% had inactivated PTEN only, while 20.0% of patients had inactivated both tumor suppressors. These data suggest that inactivation of PTEN, either alone or in combination with the inactivation of p53, prevalently occurs in NSCLC. Correlation analyses imply that inactivation of either p53 or PTEN is an early event in pathogenesis of NSCLC, while inactivation of both tumor-suppressors contributes to further tumor progression. In addition, correlation analysis of inactivated PTEN and p53 with the degree of genomic instability of each patient (obtained in previous study) disclosed that mutated p53 is associated with high genomic instability while inactivated PTEN was more frequent in patients with low genomic instability confirming important role of p53 in maintaining the stability of the genome. Finally, Kaplan & Meyer survival analyses revealed that patients with inactivated p53 have much worse prognoses. In order to conclude the study of p53 and PTEN inactivation, analyses of hypermetylation of PTEN promoter and LOH of p53 gene are underway. Citation Information: Cancer Res 2009;69(23 Suppl):B55.