EXPRESSION OF ABC TRANSPORTERS AND CHANGES IN LYMPHOCYTE SUBPOPULATIONS IN RESPONSE TO HYPERTHERMIC LIMB PERFUSION

Peter Hohenberger, MD (Robert-Roessle Hospital, Charité, Berlin, Germany)

Problem and approach: Multidrug resistance genes interfere with response to sarcoma chemotherapy. Hyperthermic limb perfusion (ILP) yields up to 30% pCRs. The contributing factors remain unclear: drug concentration, application of hyperthermia, stimulation of T-lymphocytes? We evaluated

• the involvement of ABC transporters (MDR1/PGP and MRP1) and
• leucocyte subpopulations prior, during, and after ILP

Methods: Snap-frozen tumor biopsies obtained prior and after 1LP were used to analyze the expression of MRP1 and MDR1/PGP on the mRNA level by quantitative real time RT-PCR after micro-dissection and at the protein level by ICH with antibodies MRK16 + C219 for PGP and MRPr1 + MRPm6 for MRP1. Sera were collected prior and 24h after ILP and from the perfusate and examined for CD3, CD4, CD8, CD20, CD45, CD56, CD68 + cells. Materials from 19 pts. were analyzed undergoing ILP with rhTNFa + melphalan, or melphalan+CDDP+/- adriamycin.

Results: An increase of MDR1/PGP as well as MRP gene expression could be detected, but maximum and duration of MDR1 or MRP induction varied between patients and drugs used. No clear influence of histological typing or the expression prior to ILP could be found. A significant rise in leuco- and a drop in lymphocytes after ILP could be observed. CD4:CD8 ratio remained unchanged, as well as B-cell and NK-cell count. Within the perfusate, monocytes completely disappeared.

Conclusion: Response to ILP is not uniform. The induction of MDR1/PGP and MRP by hyperthermia may interfere with the advantage of increased drug dosages. T-cell mediated tumor regression seems not to play a major role. Influencing factors such as hyperthermia and vascularity must be determined. Further analysis of the factors is important to select the right drugs applied in an optimized sequence.