EXPRESSION OF MHC MOLECULES AND ICAM-1 ON NON-SMALL-CELL LUNG CARCINOMAS - ASSOCIATION WITH EARLY LYMPHATIC SPREAD OF TUMOR-CELLS

Early microdissemination of tumour cells determines the prognosis of p atients 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 a s bone marrow or lymph nodes. The present study was designed to obtain insights into the potential role of the immune system in lymphatic an d haematogenous microdissemination of NSCLC cells. Using immunohistoch emical staining of primary NSCLC, we assessed the expression pattern o f molecules mediating an efficient cellular immune response, that is, MHC class I and class II antigens and the intercellular adhesion molec ule-1 (ICAM-1). All 58 patients evaluated were staged as free of overt metastases by conventional clinico-pathological screening. Isolated t umour cells in bone marrow or lymph nodes were identified with mAb CK2 to cytokeratin component No. 18 and mAb BerEp-4 to glycoproteins of 3 4 and 39 kd present on epithelial cells, respectively. MHC class I exp ression on primary tumours was reduced or absent in 6/10 (60.0%) patie nts with isolated cancer cells in lymph nodes as compared to 6/33 tumo urs (18.1%) without such tumour cell dissemination (P = 0.01). MHC cla ss II molecules on primary tumours were detected in 1/10 (10.0%) patie nts with micrometastases to regional lymph nodes and in 10/33 (30.3%) patients without such a tumour cell spread. None of the 10 patients wi th nodal microdissemination expressed ICAM-1 on their primary NSCLC, w hile such expression was detectable in 12/33 (36.4%) patients without this dissemination (P = 0.01). In contrast, the detection of tumour ce lls in bone marrow was not correlated to the expression of any of thes e immunoregulatory molecules. Our data suggest that escape caused by d eficient expression of MHC class I antigens and ICAM-1 on tumour cells may support homing or survival of disseminated tumour cells in lympho id tissue.