In Vitro Study of Synergism between 90Yttrium-EDTA and CHOP Regimen in Ramos Cells

Abstract

To demonstrate the in vitro synergistic antiproliferation between ⁹⁰Yttrium-EDTA and standard treatment for lymphoma-CHOP regimen including cyclophosphamide, doxorubicin, and vincristine. Ramos cell line, CD20-bearing lymphoma cells, was used as representative for aggressive type non-Hodgkin’s lymphoma. Cells were treated with chemotherapy alone or with sequential therapy of chemotherapy and 2 or 4 μCi/ml ⁹⁰Yttrium-EDTA for 24 hours. After further 72 and 96 hours incubation in standard condition, changes in proliferation were determined by Rezasulin. Antiproliferation IC50 and IC90 of each drug were estimated and dose modifying factors were calculated. The results showed that ⁹⁰Yttrium at 2 and 4 μCi/ml had no antiproliferative effect. Sequential use of ⁹⁰Yttrium and cyclophosphamide or vincristine inhibited cell proliferation over 60 or 80%, respectively. On the contrary, IC50 due to combined ⁹⁰Yttriumdoxorubicin was not significantly different from those treated with doxorubicin alone. Besides, no viable cell was found after treatment with sequential of 90Yttrium-cyclophosphamide, doxorubicin, and vincristine. This in vitro study suggests that sequential combination of ⁹⁰Yttrium and the standard CHOP regimen provide more benefit for aggressive lymphoma than chemotherapy alone.