Expression of thrombospondin in non-small cell lung cancer

Initially considered as an inhibitor of angiogenesis, the role of thrombospondin is currently controversial. The primary purpose of our study was to determine the expression of thrombospondin (TSP) in invasive lung tumours. The secondary objectives were to investigate its relationship with other factors related to angiogenesis and to assess their clinicopathological significance.

From January 1993 to September 1998, we collected non-small cell lung cancer (NSCLC) and normal nearby-matched tissues from surgical specimens of 64 patients. Using these specimens, we assessed the expression of TSP by immunohistochemistry with monoclonal antibody to human TSP (clone 11.4). This expression was also correlated with other factors directly or indirectly related to angiogenesis:p53, Ki-67 as proliferation factor and microvessel count determined with anti-CD-31 antibody.

The resected tumours (stages I-IIIB) consisted of 30 adenocarcinomas, 24 squamous cell carcinomas, 5 bronchioalveolar carcinomas, 4 adenosquamous carcinomas and 1undifferentiated NSCLC. The mean values of TSP expression in neoplastic and normal related tissues were 63.08% and 86.57 %, respectively. This difference was statistically significant (p = 0.02). There was a higher level of variability of TSP expression between tumours than between normal tissues. The expression of TSP in NSCLC was statistically correlated to the expression of TSP in normal matched tissues (coefficient correLation rate = 0.31, p<0.01). The median expression of p53, Ki-67 and microvessel count in tumours was 45.00%, 38.80% and 8.33%, respectively. The correlations between TSP and the other biological variables and between these latter variables themselves were not statistically significant. No statistically significant difference was observed in survival according to TSP expression.

TSP appeared to be decreased in NSCLC in comparison with normal matched tissue. The TSP expression was not correlated with the other studied variables and was not associated with a significant difference in survival.