P-glycoprotein expression in human oesophageal squamous carcinoma cell lines

Several tumour types show resistance to a broad spectrum of anti-cancer dru gs and are referred to as expressing a multidrug-resistant phenotype. This has been associated with the overexpression of P-glycoprotein, a highly con served transmembrane protein. Increased levels of P-glycoprotein are genera ted In tumour cells resistant to a range of chemotherapeutic drugs. We have examined five cultured human oesophageal squamous carcinoma cell lines and one epidermoid carcinoma cell line for the expression of P-glycoprotein us ing a radioimmuno assay developed for the purpose. The radioimmuno assays i dentified significantly different (P = 0.05) levels of P-glycoprotein among the five oesophageal carcinoma cell lines. Treating the lines with epiderm al growth factor caused them to increase their P-glycoprotein expression ex ponentially. Exposing the lines to vinblastine identified four of the five oesophageal carcinoma cell fines as having some resistance to the drug. The SNO cell line expressed a drug-sensitive phenotype with cell death occurri ng at low drug concentrations. This drug sensitivity was reversed by prior treatment with epidermal growth factor. The high levels of P-glycoprotein g enerated by the cell lines may be linked to the poor success rate reported for chemotherapeutic treatment of oesophageal carcinoma.