Abstract

Aims—Apoptosis is recognised as a physiological mechanism for controlling cell numbers and its subversion is thought to contribute to carcinogenesis. The aims of this study were to measure the apoptotic index (AI) in a series of squamous cell carcinomas (SCCs) of the lung using standard histological staining and confirm this by immunohistology using an antibody to an apoptosis specific protein (ASP), and to seek to correlate the AI with clinicopathological parameters.

Methods—Sections of 134 SCCs were stained by haematoxylin and eosin (H&E) for counting apoptotic bodies to determine the AI (number of apoptotic bodies/10 000 tumour cells); 26 of these were also stained with anti-ASP antibody and the proportion of ASP positive cells counted. Clinical data were obtained from hospital notes.

Results—The mean AI obtained by H&E staining of all 134 SCCs was 30.3 (SD, 24.75). Anti-ASP staining allowed easy identification of apoptotic bodies, and generated a somewhat higher index (mean, 51.4; SD 39); this was not a result of the selection of tumours because the AI by H&E in the subset stained with anti-ASP was 31.1. Regression analysis showed that the correlation between the two values of AI was highly significant (Rs = 0.9760; p < 0.001), indicating that the two methods were both reliable measures of apoptosis but that the anti-ASP staining is the more sensitive method. The tumours were grouped into high AI (> 50) and low AI (< 50) and survival analysis was carried out. The mean survival of the high AI group was 109 weeks and of the low AI group 72 weeks (p = 0.036).

Conclusions—Anti-ASP staining is a reliable, easy, and sensitive method for assessing apoptosis in tumour sections and confirms the validity of the AI obtained by H&E staining. AI is a guide to the behaviour of SCCs of the lung.