Transplantation of bone marrow cells from transgenic mice expressing the human MDR1 gene results in long-term protection against the myelosuppressive effect of chemotherapy in mice

Abstract

Many human cancers that are initially responsive to chemotherapy eventually fail to respond to treatment. For some drugs, dose escalation that may be required for a cure cannot be achieved because sensitive tissues such as bone marrow (BM) limit cytotoxic therapy. Approaches to prevent or circumvent BM toxicity are therefore a high priority of research on dose escalation protocols. In this study, we have transplanted BM cells from transgenic mice that constitutively express physiologic amounts of a functional human multidrug resistance (MDR1) cDNA to lethally irradiated C57BL/6 x SJL F1 mice (n = 36). From 6 weeks to 10 months after the transplant, all animals contained MDR1 DNA in spleen and BM specimens as indicated by Southern blot analysis, and expressed MDR1 messenger RNA in BM samples as detected by slot blot analysis. In addition, these animals were resistant to the myelosuppressive effect of doxorubicin, daunomycin, taxol, vinblastine, vincristine, etoposide, and actinomycin D, whereas control animals that were reconstituted with normal BM were drug sensitive. Finally, the chemoprotection afforded by the MDR1 gene could readily be reversed by adding chemosensitizers such as cyclosporin A and R-verapamil to chemotherapy. Hence, it appears that BM cells expressing the human MDR1 gene maintain this function after transplantation to host animals for a minimum of 10 months, and confer multidrug resistance to these BM recipients. This selective advantage conferred by expression of the MDR1 cDNA suggests a strategy for the use of MDR1 gene therapy in cancer chemotherapy and for the introduction of otherwise nonselectable genes into BM.

Ligand-directed Cancer Gene Therapy to Angiogenic Vasculature

“…For example, bone marrow depletion remains a major side effect of chemotherapy. Transfection of bone marrow cells with multidrug-resistant 1 gene enhances cellular resistance to chemotherapy and allows patients to receive higher doses of conventional agents (Culver, 1996;Huber and Margrath, 1998;Lattime and Gerson, 2001;Mickisch et al, 1992;Templeton and Lasic, 2000).…”

Protection and selection for gene therapy in the hematopoietic system

“…Treatment of these animals with a known p‐glycoprotein inhibitor restored the sensitivity of the bone marrow to chemotherapeutic agents, thus implicating MDR‐1 in the protective effect 32. Subsequent studies showed that transplantation of control animals with bone marrow from transgenic donors led to inhibitor‐sensitive chemoprotection of hematopoiesis in the recipient animals 33.…”

Rekombinante DNA-Technologie zur Unterstützung klinisch orientierter Forschung: Die MDR-transgene Maus

“…Differentialblutbilder von normalen und von MDR-transgenen Mäusen ergaben, daß alle wesentlichen peripheren Blutzellen der MDR-transgenen Tiere durch den Schutz des MDR 1-Transgenes unter Chemotherapie einen Selektionsvorteil gegenüber Normalzellen aufwiesen (20). Dieser MDR1 -Knochenmarkschutz konnte durch Knochenmarktransplantation auf Empfängertiere übertragen werden, so daß der Effekt als intrinsisch für das Knochenmark gedeutet werden muß (24)…”

“…Differentialblutbilder der MDR-transgenen Mäuse bestätigen, daß alle wesentlichen Bestandteile des peripheren weißen Blutbildes zu den dramatischen Veränderungen der Zellzahlen beitrugen, die unter medikamentös verstärkter Chemotherapie beobachtet wurden (20). (24). Knochenmarksuppression ist für viele Formen klassischer Chemotherapie ein wesentliches Merkmal und der wichtigste dosislimitierende Faktor.…”

“…Aktuelle Untersuchungen an unserem MDR-transgenen Mausmodell haben gezeigt, daß die Transplantation von Knochenmarkzellen mit dem menschlichen MDR 1 -Gen sicher und wirkungsvoll ist. Das Knochenmark der Empfänger weist eine hohe und stabile Expression des MDR1 -Genes auf, wobei eine angemessene Chemotherapietoleranz resultiert (24).…”