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.
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.


CONCLUSIONS
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.
Günthert
Andreas R
AR
Department of Gynecology and Obstetrics, Georg-August-University, Göttingen, Germany.
Gründker
Carsten
C
Bongertz
Till
T
Nagy
Attila
A
Schally
Andrew V
AV
Emons
Günter
G
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D019450:Genes, MDR / Q000187:drug effects; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D007986:Luteinizing Hormone; D009376:Neoplasms, Hormone-Dependent / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000903:Antibiotics, Antineoplastic; C080883:LHRH, lysine(6)-doxorubicin; D007987:Gonadotropin-Releasing Hormone; D004317:Doxorubicin; D007986:Luteinizing Hormone