Immunohistochemical study of P-glycoprotein distribution in lung cancer

Indirect immunoperoxidase was used to determine the reactivity of C219 (P-glycoCHEK C219, Centocor Diagnostics, Malvern, PA), a monoclonal antibody (Mab) with high affinity for an internal epitope of the P-glycoprotein encoded by the multidrug resistance (MDR1) gene, in 40 surgically resected primary lung tumours. C219 reactivity was qualitatively classified in seven small cell lung cancers (SCLC), 29 non small cell lung cancers (NSCLC), and four carcinoid tumours. Ploidy was analysed by means of static cytometry using a computer-assisted image processor following Feulgen staining of cytologic prints of 32/40 lung tumours. Indirect immunoperoxidase reactivities of Mabs S-L 11.14 and MOC-1 were also studied to characterize the expression of cluster 1 lung cancer antigens and hence to determine among the NSCLC those which expressed the neural cell adhesion molecule (NCAM). Eighteen (45%) lung tumours strongly expressed P-glycoprotein as an immunostaining of many islets of malignant cells or almost all malignant cells. In addition, 8/40 tumours (20%) showed a weak reactivity (few immunostained cells) and 14/40 (35%) no reactivity. There was no difference of reactivity when NSCLC were compared with SCLC. The expression of P-glycoprotein in NSCLC did not vary significantly when the stage of disease was considered. Among the 29 NSCLC, 10 (36%) expressed S-L 11.14 and MOC-1. The NCAM positive NSCLC did not show any difference of P-glycoprotein expression in comparison with NCAM negative ones. Finally, C219 immunoperoxidase reactivity did not significantly differ according to the ploidy status. In conclusion, the internal epitope of the P-glycoprotein encoded by the MDR1 gene is frequently expressed by lung tumours of any histological type. This expression is not higher in Stage III and IV lung cancers in comparison with Stage I and II ones, or in NSCLC in comparison with SCLC either. Thus, the C219 related epitope seems to have a weak implication in the lower chemosensitivity of both advanced stages and NSCLC.