TP53 mutational pattern in Spanish and Polish non-small cell lung cancer patients: null mutations are associated with poor prognosis

Abstract

Inactivation of TP53 tumor suppressor gene is the most frequent molecular alteration in NSCLC, involving up to 60% of cases. Furthermore, TP53 mutational spectrum is related to the type of mutagen exposure, as well as racial and/or diet di erences. Nearly 95% of TP53 perturbations a ect codons included within exons 5 ± 8 which encode for almost the entire DNA-binding domain. In this study we addressed the possible prognostic value of the molecular alterations identi®ed in exons 5 ± 8 of the TP53 gene in DNAs from 151 para n-embedded NSCLC sections corresponding to 59 Spanish and 92 Polish stage I-IIIA resected patients. PCR/single-strand conformation polymorphism (SSCP) analysis revealed that the occurrence of TP53 exon 5 ± 8 mutations was 17/59 (29%) in the Spanish cohort and 17/92 (18%) in the Polish group. However, when DNA sequencing analysis was performed, these frequencies were reduced because of the presence of SSCP-false positive, intronic and silent mutations and polymorphisms. Fifteen of the 59 Spanish NSCLC tumors (25%) harbored TP53 mutations a ecting exons 5 ± 8 coding sequences, whereas only 12 of 92 Polish neoplasms (13%) contained alterations in the central hydrophobic region of p53. Our results indicate that the occurrence of TP53 mutations a ecting exon 5 ± 8 coding sequences in some European NSCLC populations may be lower than previously reported, and that the TP53 mutational patterns of these cohorts di er somewhat. The Spanish NSCLC patients contained missense mutations (9/59, 15%) and a relatively high percentage of null mutations (5/59, 8%) while the Polish patients mostly harbored missense mutations (9/92, 10%) and only one tumor contained a null type (1/92, 1%). Moreover, most TP53 missense mutations in the Spanish group were located outside the conserved regions, whereas the same mutations in the Polish group a ected conserved amino acids. Furthermore, the Polish patients harbored a high percentage of G?A transitions (most of them at non-CpG sites), while G?T transversions were predominant in the Spanish group. Our ®ndings suggest that there may be di erent racial or exogenous factors in these two populations which may help to explain both the distinct TP53 mutational pattern and the lower frequency obtained in the Polish group. The presence of missense mutations did not confer a worse clinical outcome in these subsets of NSCLC patients. However, patients whose tumors contained null TP53 gene mutations had a 5 month median disease-free survival time in contrast with 42 months in those patients without mutations (P=0.008). These ®ndings suggest that loss of p53 function may enhance tumor progression in NSCLC patients independently of whether dominant negative TP53 missense mutations are present.

Correlation between the status of the p53 gene and survival in patients with stage I non-small cell lung carcinoma

“…d P, log-rank test correlate with prognosis, while patients with missense mutations signi®cantly correlated with prognosis. This result was not consistent with the previous study (de Anta et al, 1997). However, since the previous study was restricted to the analysis of exons 5 ± 8 alone, a substantial number of p53 mutations, in particular null mutations which were dominant outside exons 5 ± 8, were overlooked.…”

“…There was not a signi®cant dierence between the analysis of p53 mutations through exons two to 11 and the analysis of p53 mutations through exons 5 ± 8. Recently it was reported that null mutations were associated with poor prognosis (de Anta et al, 1997). Then, we also analysed the correlation between the types of p53 mutations and prognosis (Table 4).…”

“…The discordance of the results among these studies could be due to the dierences in methods of detection of p53 abnormalities. Previous studies on the prognostic signi®cance of p53 mutations in NSCLC have been restricted to the analysis of the hot-spot region alone (Horio et al, 1993;Mitsudomi et al, 1993;Carbone et al, 1994;Isobe et al, 1994;Fong et al, 1995;Mitsudomi et al, 1995;de Anta et al, 1997;Fukuyama et al, 1997;Ohno et al, 1997), and none of the studies analysed correlation of p53 mutations in the entire coding region with prognosis.…”

“…Thus, to evaluate the clinical performance of p53 abnormalities, it is necessary to critically assess the status of the p53 gene and protein expression by a more comprehensive analysis. A recent study indicated that null mutations are associated with poor prognosis of NSCLC patients, while missense mutations are not associated with prognosis (de Anta et al, 1997). However, the number of patients with mutations was small and the disease stage was not adjusted.…”

Nondisruptive p53 Mutations Are Associated with Shorter Survival in Patients with Advanced Non–Small Cell Lung Cancer

“…In studies of early-stage NSCLC, a prognostic value for particular types of TP53 mutations is usually found, although results are contradictory. Truncated, but not missense, mutations have been associated with shorter PFS or OS in some studies (34,35), whereas others have reached the opposite conclusion (36). Finally, some authors have reported an association between shorter OS and the presence of particular types of TP53 mutations, such as "severe flexible and contact" mutants (37), "truncated, structural, and DNA contact mutations" (38), or mutations in particular exons and codons (39,40).…”