Rituximab but not Other anti-CD20 Antibodies Reverses Multidrug Resistance in 2 B lymphoma Cell Lines, Blocks the Activity of P-glycoprotein (P-gp), and Induces P-gp to Translocate out of Lipid Rafts

Abstract

The objective of this study was to investigate the ability of the anti-CD20 antibody, Rituximab (RTX), to inhibit the activity of P-glycoprotein (P-gp), and reverse multidrug resistance (MDR) in 2 P-gp/CD20 lymphoma cell lines. We determined whether RTX would chemosensitize the 2 P-gp cell lines in vitro, and inhibit the ability of the cells to efflux Rhodamine 123. One cell line was infected with an MDR1 vector and the other was generated by drug selection. We also determined whether RTX induced P-gp to translocate out of lipid rafts. RTX chemosensitized 2 different MDR cell lines, inhibited the activity of P-gp in both, and induced P-gp to translocate out of lipid rafts in the 1 cell line that was studied in greater detail. In contrast, 3 other anti-CD20 antibodies did not chemosensitize, inhibit the activity of P-gp, or induce it to translocate out of rafts, despite the fact that 1 antibody recognized the same epitope on CD20. Our results suggest that RTX can chemosensitize 2 CD20/P-gp cell lines in vitro by inhibiting the activity of the P-gp pump. The inhibition of P-gp activity correlated with the ability of RTX to induce P-gp to translocate out of lipid rafts. Although the mechanisms by which RTX effects P-gp translocation and activity are not yet known, they are not associated with acid-sphingomyelinase activation in raft microdomains, as described for the antiproliferative activity of RTX.

Rituximab therapy in malignant lymphoma

“…In cell lines, the Pglycoprotein pump is translocated out of the lipids rafts. This activity seems independent of the classical antiproliferative effect of rituximab (Ghetie et al, 2006).…”

“…In one hypothesis, this synergism is mediated, at least in part, via downregulation of interleukin-10 (IL-10) by rituximab, which in turn causes downregulation of the antiapoptotic protein bcl2 and increased sensitivity to apoptosis (Vega et al, 2004). Another mechanism involves the inhibition of the activity of P-glycoprotein and, thus, the efflux of drugs like doxorubicin or vincristine (Ghetie et al, 2006). In cell lines, the Pglycoprotein pump is translocated out of the lipids rafts.…”

MDR1 in immunity: friend or foe?

“…In addition to their therapeutic effect based on complement-mediated and antibody-dependent cell-mediated cytotoxicity, both mAbs, could increase chemotherapy efficacy, by limiting MDR1 activity as fixation to their target could favor MDR1 re-localization outside of the lipid rafts where it is much less efficient. 98,99 More recently, PI substrates of MDR1 have also been used as unconventional competitive inhibitors in MM to improve efficacy of carfilzomib (proteasome inhibitor). 93 Understanding MDR1 regulation processes in normal and neoplastic immune cells therefore appears as an interesting lead to improve combination therapy options in hematological tumors and discover new molecules efficiently blocking MDR1 activity with limited side effects.…”

A double blinded, placebo-controlled pilot study to examine reduction of CD34+/CD117+/CD133+ lymphoma progenitor cells and duration of remission induced by neoadjuvant valspodar in dogs with large B-cell lymphoma

“…In addition, the variable sensitivity to verapamil and other ABC transporter inhibitors by LPCs and side population cells in leukemia and lymphoma suggests that these cells might rely on alternative mechanisms of drug export and/or drug resistance. Still, it has been shown that clinically relevant anti-lymphoma immunotherapies including rituximab 58 and anti-CD19 antibodies 59 induce ABCB1 to translocate out of lipid rafts, reducing its ability to extrude chemotherapy agents such as vincristine and doxorubicin and increasing the chemosensitivity of drug-resistant lymphoma cell lines. We propose that the totality of data continues to support the rationale for implementing treatment approaches for non-Hodgkin lymphoma that target ABCB1 and ABCG2 in the neoadjuvant or the adjuvant settings.…”