Multiple Myeloma: Expression of Nucleoside Transporters on Malignant Plasma Cells and Their Relationship to Cellular Proliferation

Abstract

The expression of nucleoside transporters is a limiting factor in the pharmacology of the nucleoside analogue, cytosine arabinoside (AraC) and is associated with cellular proliferation. We investigated the expression of nucleoside transporters on plasma cells from the bone marrow of 51 patients with multiple myeloma by 2-colour immunofluorescence flow cytometry, utilising 5-(SAENTA-x8)-fluorescein, a fluorescent ligand for the nucleoside transporter and anti-CD38 conjugated to phycoerythrin, as CD38 expression has unique characteristics on plasma cells. Mean nucleoside transporter expression on bone marrow plasma cells from patients with myeloma (1777 +/- 2181 transporters/plasma cell) was not significantly different from expression on plasma cells from normal bone marrow (997 +/- 1096 transporters/plasma cell). However, analysis of disease subgroups revealed a significant trend towards increased transporter expression in patients with progressive disease compared to those with stable disease (chi 2 = 4.0, p < 0.05). Nucleoside transporter expression correlated significantly with the plasma cell labeling index (LI) (r = 0.45, p < 0.01) and serum thymidine kinase levels (r = 0.66, p < 0.01), both markers of cellular proliferation but not with c-myc oncoprotein expression. These findings suggest that flow cytometric measurement of nucleoside transporter expression on plasma cells provides a rapid and convenient measurement of disease activity or quiescence in myeloma.

The Labelling Index of Primitive Plasma Cells Determines the Clinical Behaviour of Patients with Myelomatosis

“…Extensive studies have demonstrated that a LI of 0 . The LI is an indicator of disease activity and has been shown to correlate with other markers of proliferation, such as serum thymidine kinase levels (STK) (Brown et al, 1989) and nucleoside transporter levels (Petersen et al, 1994). The combination of LI with serum b 2 -microglobulin level provides the most significant prognostic information of any of the known prognostic factors (Griepp et al, 1988).…”

“…The cell suspension was incubated in RPMI-1640 (ICN Biomedicals, Costa Mesa, Calif., U.S.A.) with 10% fetal calf serum (ICN Biomedicals) and 10 M bromodeoxyuridine (BrdUrd, Boehringer Mannheim, Penzburg, Germany) at 378C for 1 h. Cells were then tested for BrdUrd incorporation using either an immunofluorescent slide technique or by flow cytometry (Griepp et al, 1983;Petersen et al, 1994). The cell suspension was incubated in RPMI-1640 (ICN Biomedicals, Costa Mesa, Calif., U.S.A.) with 10% fetal calf serum (ICN Biomedicals) and 10 M bromodeoxyuridine (BrdUrd, Boehringer Mannheim, Penzburg, Germany) at 378C for 1 h. Cells were then tested for BrdUrd incorporation using either an immunofluorescent slide technique or by flow cytometry (Griepp et al, 1983;Petersen et al, 1994).…”

Nucleoside analogues: mechanisms of drug resistance and reversal strategies

“…High cellular proliferation rates are associated with high levels of hENT1-mediated activity that increase the nucleoside drug uptake. 217,218 Wiley et al 219 determined that in vitro treatment of isolated human leukemic cells with GM-CSF, resulted in an increase in hENT1 expression. Reuter et al 220 established that blasts from AML patients treated with GM-CSF displayed an enhanced drug uptake after low or SDAC doses.…”

Dose escalation therapy in previously untreated patients with multiple myeloma following Z‐Dex induction treatment

“…Although this remains unproven, in␣vitro studies demonstrate that cisplatin targets proliferating myeloma cells (Ghanta et al , 1977; Barlogie et al , 1989) and Ara‐C is likely to be effective in cells which express nucleoside transporter complexes in high numbers. In myeloma, nucleoside transporter complex levels correlate with plasma cell labelling index and aggressive disease (Petersen et al , 1994). EDAP (etoposide, dexamethasone, Ara‐C, cisplatin) appears to have antitumour effect in some studies in this context (Barlogie et al , 1989).…”