Reciprocal correlation between expression of P-glycoprotein and accumulation of rhodamine 123 in human tumors.

The aim of this investigation was to determine whether a correlation exists between expression of the multi-drug-resistance associated P-glycoprotein 170 (P-gp170) and the accumulation of rhodamine 123 in human tumors. We investigated a panel of inherently resistant cell lines originating from human kidney tumor specimens and chemotherapeutically pretreated leukemias. The expression of P-gp170 was evaluated by means of two different immunohistological methods using two monoclonal antibodies against P-gp170. We found a significant reciprocal correlation between expression of P-gp170 and accumulation of rhodamine 123. This supports the view that P-gp170 might function as efflux pump in human tumors, as previously described for experimental models.