Apoptosis is not correlated with the presence of CD57+ NK-cells in brain metastases.

Background: Cell apoptosis in solid tumours has been related to immunological attack by NK-cells. The purpose of the present study is to verify in the tissue of brain metastases a possible relationship among the degree of NK-cell infiltration and the number of apoptotic tumour cells.
Methods: Twenty brain metastases whose tumour cells expressed CD95 (Fas/APO1) have been studied. NK-cells were identified by using the monoclonal antibody to CD57, and apoptotic tumour cells by means of the immunostain with the anti-ssDNA monoclonal antibody F7-26. The Spearman rank correlation test was used to study the relationship between the degree of CD57-NK-cell infiltration and the apoptosis labelling-index.
Findings: Positivity to F7-26 was present in all tumour samples, but the number of immunostained cells showed a wide variability, with a mean apoptosis labelling-index of 11.48%. All the studied tumours showed CD57 immunostained cells, with a number that ranged between 4 and 20 per microscopical field at 200x (mean+/-standard deviation: 8.4+/-3.7). Statistical studies showed that there was no correlation between the number of CD57 immunostained NK-cells and the apoptosis labelling-index (p>0.05).
Interpretation: These findings suggest that in brain metastases, apoptosis related to immune response is mainly mediated by activated tumour-infiltrating mononuclear cells other than CD57(+) NK-cells.