Background: Reduction of intracellular drug accumulation plays an important role in resistance to chemotherapy in neoplasms. MDR-proteins regulate this cell activity.
Material and method: A total of 147 tumor samples were collected from 143 patients. Thirty-five samples were obtained by bronchoscopy and 112 were surgical specimens. One hundred and one samples from 99 patients were valid for the study. The samples underwent cryopreservation and immunohistochemistry for detection of three multiple-drug resistant proteins (MDR-proteins): Pgp, Mrp1 and Lrp.
Results: No proteins were expressed in 16 patients. A single protein was expressed in 32 patients: 3 Pgp, 11 Mrp1 and 18 Lrp=0. Two proteins were expressed in 34 patients: 24 Pgp and Lrp, 5 Mrp1 and Pgp, 5 Mrp1 and Lrp=0. All three proteins were expressed in 17 patients. No differences were observed in expression according to age (Pgp [p=0.74], Mrp1 [p=0.95], Lrp [p=0.26]). No differences were found according to sex, when both the number (p=0.72) and type (p=0.39) of simultaneously expressed proteins were analyzed. No differences were observed according to tumoral stage [number (p=0.55), type (p=0.21)] or histological grade [number (p=0.59), type (p=0.51)]. The tendency toward simultaneous expression of Pgp and Lrp was highly significant (p<0.01). The same tendency was not observed in the association between Mrp1 and Lrp (p=0.26).
Conclusions: MDR-proteins are frequently expressed in lung cancer. Of the three MDR-proteins studied, Lrp was the most frequent. Adenocarcinoma expressed less Mrp1 than other histological types. Squamous carcinoma expressed less Lrp than adenocarcinomas and large-cell undifferentiated carcinomas. In a considerable number of patients, more than two proteins were expressed simultaneously. Squamous-cell carcinomas tended to express Pgp, Mrp1 and Lrp simultaneously. Pgp was usually expressed in association with Lrp.