Phase I/II trial of dexverapamil (DEX), epirubicin (EPI) plus GM-CSF in advanced pancreatic cancer

Scheithauer, Werner; Kornek, Gabriela; Raderer, Markus; Menschik, M.; Koperna, K; Karner, J.

doi:10.1097/00001813-199409001-00142

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“…Haematological toxicity of modulators has been reported in clinical trials (Figueredo et al, 1990;Scheithauer et al, 1993;Bartlett et al, 1994). Pgp modulation on haemopoietic progenitors and also pharmacokinetic changes of the cytotoxic drug due to Pgp modulation on liver or kidney have been suggested.…”

Section: Discussionmentioning

confidence: 99%

A low but functionally significant MDR1 expression protects primitive haemopoietic progenitor cells from anthracycline toxicity

et al. 1997

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Summary.Pgp is expressed on normal haemopoietic progenitor cells. The significance of the efflux pump in protecting normal progenitors for anthracycline toxicity is not defined and is the subject of this study. Pgp was measured in CD34 þ progenitors with a rhodamine efflux assay. A high efflux, modulated by verapamil, was only found in a distinct subpopulation (20-30%). Pgp measured by the monoclonal antibody antibody (MoAb) MRK-16 was low in the rhodamine dull, but significantly (P < 0 . 04) higher than in the rhodamine bright cells. Reverse transcriptase polymerase chain reaction (RT-PCR) of MDR1 mRNA showed a very weak signal in both populations. In a single-cell clonogenic assay, rhodamine dull cells appeared less sensitive to anthracyclines (IC 50 daunorubicin 0 . 005 mg/ml; adriamycin 0 . 03 mg/ml) compared to rhodamine bright cells (IC 50 daunorubicin 0 . 0025 mg/ml; adriamycin 0 . 01 mg/ml). Furthermore, verapamil significantly (P < 0 . 05) potentiated anthracycline toxicity only in the rhodamine dull cells, proving its Pgp-specific modulating effect. Rhodamine dull cells gave larger and more mixed colonies compatible with a more primitive origin. Although detection with MoAbs and RT-PCR revealed a low Pgp level, functionally this Pgp appeared to be very important in protecting primitive progenitors against anthracycline toxicity. This protection can be jeopardized by administration of Pgp modulators.

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Section: Discussionmentioning

confidence: 99%