High number of tumour-infiltrating lymphocytes is associated with apoptosis in non-small cell lung carcinoma

Aim: To test whether the number of tumour-infiltrating mononuclear cells (M NC), namely T-lymphocytes (TIL) and, to a lesser degree, B-lymphocytes and macrophages, is associated with tumour cell apoptosis in non-small cell lun g carcinoma (NSCLC). Methods and results: Eighty-four non-small cell lung t umours were analysed with specific antibodies and the extent of apoptosis w as determined using 3'-end labelling of fragmented DNA (TUNEL). All paramet ers were determined from the same tumour areas. In general, adenocarcinomas showed a higher number of MNC than squamous cell carcinomas (p=0.04). The number of MNC increased concurrently with the grade of tumour, occurrence b eing highest in high grade (III) tumours (p=0.05). The number of apoptotic cells was significantly higher in tumours with a high number of CD3+ and CD 8+ lymphocytes (p=0.01) and B-cells (p=0.05). Tumours showing abnormal p53 protein expression had a significantly lower count of CD8+ T-cells compared to p53-negative tumours (p=0.03). Conclusions: Our results showed an assoc iation between lymphocytic infiltration and extent of apoptosis in NSCLC, s uggesting that an attempt to suppress the growth of transformed tumour cell s exists even when the tumour has reached an advanced stage.