GENETIC ALTERATIONS OF THE TP53 GENE, P53 PROTEIN EXPRESSION AND HPV INFECTION IN PRIMARY CERVICAL CARCINOMAS

Primary cervical carcinomas from 92 patients were investigated for gen etic alterations in the tumour suppressor gene TP53. Studies of alleli c imbalance (AI) were performed by Southern blot analysis and by using two PCR (polymerase chain reaction) polymorphisms within the TP53 gen e. AI in the tumour was observed in 22 per cent (11 of 52 informative patients) and was significantly associated with recurrence both in a u nivariate (P=0.013) and in a multivariate (P=0.045) analysis. The DNA samples were subjected to mutation analysis of four of the conserved d omains in the TP53 gene, using PCR followed by constant denaturant gel electrophoresis (CDGE). Mutations were observed in 2 of 92 tumours (2 per cent), of which one was a silent mutation and the other a framesh ift. Overexpression of the p53 protein was found by immunostaining of sections from formalin-fixed, paraffin-embedded material in 55 per cen t (51/92) of the tumours. In 88 per cent (45/51) of these, overexpress ion was present in less than 5 per cent of the tumour cells. Overexpre ssion was significantly associated with relapse-free survival only in a univariate analysis (P=0.045). AI of the TP53 locus did not correlat e with p53 expression or mutation. The important gene on 17p, responsi ble for the shorter disease-free survival for patients with AI of TP53 , may therefore be another gene closely linked to TP53. In addition, t he 92 tumour samples were tested for the presence of human papillomavi rus (HPV) types 16 and 18. Fifty-four per cent (50/92) of the samples were positive for HPV 16 using in situ hybridization, and 93 per cent (86/92) using the PCR technique. The numbers for HPV 18 were 15 per ce nt (14/92) and 23 per cent (21/92), respectively. Twenty-one per cent (19/92) were positive for both HPV 16 and HPV 18, while 4 per cent (4/ 92) were negative for both HPV 16 and 18. The tumour with the frameshi ft TP53 mutation was HPV 16-positive, and the four samples negative fo r HPV 16 and 18 did not contain TP53 mutations within the conserved do mains but had elevated p53 protein expression.