Induction of apoptosis by AN-152, a cytotoxic analog of luteinizing hormone-releasing hormone (LHRH), in LHRH-R positive human breast cancer cells is independent of multidrug resistance-1 (MDR-1) system*

Günthert, Andreas R.
Gründker, Carsten
Bongertz, Till
Nagy, Attila
Schally, Andrew V.
Emons, Günter

¹Department of Gynecology and Obstetrics, Georg-August-University, Göttingen, Germany; ²Tulane University Medical Center and Veterans Affairs Medical Center, New Orleans, LA, USA

* This study was supported by the Deutsche Krebshilfe, Dr Mildred Scheel Stiftung, Germany.

Address for offprints and correspondence: Günter Emons, Department of Gynecology and Obstetrics, Robert-Koch-Street 40, D-37075 Göttingen, Germany; Tel.: +49-551-396501; Fax: +49-551-396585; E-mail:[email protected]

Breast Cancer Research & Treatment 87(3):p 255-264, October 2004.

Summary

Objective.

More than 50% of human breast cancers express receptors for luteinizing hormone-releasing hormone (LHRH-R). These receptors can be used for targeted chemotherapy with agents like AN-152, in which doxorubicin is linked to analog [D-Lys⁶]LHRH. We compared the effects of AN-152 and doxorubicin in human breast cancer cells.

Methods.

MCF-7, T47D, HCC-70 and ZR-75-1 cells were analysed for expression of LHRH-R using RT-PCR, immunostaining and flow cytometry. Apoptosis and expression of MDR-1 gene product Pgp were measured by flow cytometry. Cleavage of doxorubicin from AN-152 by serum carboxylesterase (CE) was inhibited by DFP.

Results.

In MCF-7, T47D and HCC-70 cells we found cell surface expression of LHRH-R. In ZR-75-1 cells only sparse surface expression was found. In HCC-70 cells, induction of apoptosis by AN-152 was stronger than by doxorubicin in medium containing fetal calf serum (FCS). Pretreatment with DFP increased AN-152-induced apoptosis in LHRH-R positive MCF-7 and HCC-70 cells and reduced apoptosis in ZR-75-1 cells. In serum-free medium apoptosis induced by AN-152 was stronger than that induced by doxorubicin in HCC-70, T47D and MCF-7 cells, but weaker in ZR-75-1 cells. In medium containing FCS, both AN-152 and doxorubicin induced surface expression of MDR-1 gene product Pgp, but the effect of AN-152 was weaker. Pgp-expression induced by AN-152 was inhibited by pretreatment with DFP. AN-152 did not induce Pgp-expression in serum-free medium.

Conclusion.

The cytotoxic LHRH analog AN-152 induces apoptosis independent of MDR-1 in LHRH-R positive breast cancer cells. The efficacy and/or specificity of AN-152 is improved by suppression or absence of CE activity.