Discrepant flow cytometric expression and function of P-glycoprotein in neuroblastic tumors

Background: Patients suffering from neuroblastic tumors are currently being classified into prognostic subsets based on different clinical and biologi c features. In this study, a triple-color flow cytometric assay and a funct ional test were applied to neuroblastoma cell lines and patients with a neu roblastic tumor, and the value of P-glycoprotein expression and function as potential prognostic characteristics, was determined. Methods: Twenty-two single-cell suspensions prepared from tumors, and neuro blasts from four bone marrow samples were analyzed by triple-color flow cyt ometry. Neuroblasts were identified by NB84-positivity and absence of CD45. P-glycoprotein expression was evaluated using 4E3 and MRK16 antibodies. Ei ghteen samples were tested with a functional assay, based on accumulation a nd retention of rhodamine-123 with and without the inhibitor verapamil. Six neuroblastoma cell lines were also evaluated. Results: P-glycoprotein expression was seen in 18 of 26 patient samples and in three of six cell lines. The highest expression levels were found in lo w stage neuroblastoma and well-differentiated tumors; whereas the highest a ctivities were found in stage 4 neuroblastoma and the lowest in ganglioneur oblastoma and ganglioneuroma patients. In 10 of 17 samples, concordant resu lts were found between the flow cytometric immunological test and immunocyt ochemistry. Conclusions: The described flow cytometric technique is a new, alternative approach to detect P-glycoprotein expression and function in neural crest t umors. Based on the expression level and the activity value, patients can b e segregated into different phenotypic groups. In particular, those patient s with high P-glycoprotein activity might benefit from treatment regimens c ontaining reversal agents. Cytometry 37:125-132, 1999. (C) 1999 Wiley-Liss, Inc.