Abstract
Antibodies specific for human p53 were analysed in sera of lung cancer patients. We detected p53 antibodies in the sera of 24% (10/42) of patients with lung carcinoma. The distribution was as follows: 4/9 small-cell lung carcinomas (SCLCs), 2/18 squamous cell lung carcinomas (SCCs), 2/10 adenocarcinomas (ADCs) and 2/5 large-cell lung carcinomas (LCCs). p53 antibodies were always present at the time of diagnosis and did not appear during progression of the disease. Using an original peptide-mapping procedure, we precisely localised the p53 epitopes recognised by p53 antibodies. Immunodominant epitopes reacting with antibodies were localised in the amino and carboxy termini of the protein, similar to those found in breast carcinoma patients or in animals immunised with p53. In light of these data, we suggest that p53 antibodies occur via a self-immunisation process that is the consequence of p53 accumulation in tumour cells. p53 antibodies were also detected in two patients without detected malignant disease. One of these patients died 6 months later of lung carcinoma, suggesting that p53 antibodies may be a precocious marker of p53 alteration.
Highlights
Small-cell lung carcinoma (SCLC) accounts for approximately 20% of lung cancers, while the remaining 80% fall into the broad category of non-small-cell carcinomas (NSCLCs), which include squamous cell carcinomas, adenocarcinomas and large-cell carcinomas
Well-defined regions of human p53 were amplified by polymerase chain reaction (PCR) and subcloned in the pLIP4 vector in fusion with the phoA gene (Schlichtholz et al, 1992). p53 was divided into six welldefined fragments
Since initial experiments showed that different human sera can lead to various background levels with sharp variations, we devised an ELISA procedure in which each serum was tested on both human p53 and irrelevant antigen
Summary
SeraSera were collected from May 1992 to October 1992, on the occasion of routine blood analysis; 7 ml of whole blood was centrifuged at 3,000 r.p.m. for 15 min and supernatant was stored at - 80°C until use.All analyses were done in duplicate. Patients' and control subjects' sera were analysed in random order and with the observer blind to the patient/control status. The pLip vector (Gillet et al, 1992; Schlichtholz et al, 1992) used for the production of hybrid proteins has been described previously. Well-defined regions of human p53 were amplified by polymerase chain reaction (PCR) and subcloned in the pLIP4 vector in fusion with the phoA gene (Schlichtholz et al, 1992). Fragments 1 (residues 1-112) and 6 (residues 306-393) corresponded to the amino and carboxy termini of the protein and were usually devoid of mutations (Caron de Fromentel & Soussi, 1992). The antigenicity of the expressed hybrid protein was assessed by its reactivity with various MAbs with a known specificity (Schlichtholz et al, 1992)
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