Expression of MHC molecules and ICAM-1 on non-small cell lung carcinomas: association with early lymphatic spread of tumour cells.

Early microdissemination of tumour cells determines the prognosis of patients with apparently localised non-small cell lung cancer (NSCLC). Monoclonal antibodies to epithelial antigens can now be used to detect single carcinoma cells present in mesenchymal secondary organs such as bone marrow or lymph nodes. The present study was designed to obtain insights into the potential role of the immune system in lymphatic and haematogenous microdissemination of NSCLC cells. Using immunohistochemical staining of primary NSCLC, we assessed the expression pattern of molecules mediating an efficient cellular immune response, that is, MHC class I and class II antigens and the intercellular adhesion molecule-1 (ICAM-1). All 58 patients evaluated were staged as free of overt metastases by conventional clinico-pathological screening. Isolated tumour cells in bone marrow or lymph nodes were identified with mAb CK2 to cytokeratin component No. 18 and mAb BerEp-4 to glycoproteins of 34 and 39 kd present on epithelial cells, respectively. MHC class I expression on primary tumours was reduced or absent in 6/10 (60.0%) patients with isolated cancer cells in lymph nodes as compared to 6/33 tumours (18.1%) without such tumour cell dissemination (P = 0.01). MHC class II molecules on primary tumours were detected in 1/10 (10.0%) patients with micrometastases to regional lymph nodes and in 10/33 (30.3%) patients without such a tumour cell spread. None of the 10 patients with nodal microdissemination expressed ICAM-1 on their primary NSCLC, while such expression was detectable in 12/33 (36.4%) patients without this dissemination (P = 0.01). In contrast, the detection of tumour cells in bone marrow was not correlated to the expression of any of these immunoregulatory molecules. Our data suggest that escape caused by deficient expression of MHC class I antigens and ICAM-1 on tumour cells may support homing or survival of disseminated tumour cells in lymphoid tissue.