A single in vivo administration of bombesin antagonist RC-3095 reduces the levels and mRNA expression of epidermal growth factor receptors in MXT mouse mammary cancers

Karoly Szepeshazi, Andrew V. Schally, Gabor Halmos, Najib Lamharzi, Kate Groot, Judit E. Horvath

Research output: Contribution to journalArticle

41 Scopus citations


Epidermal growth factor (EGF) and its receptors (EGFR) play important roles in tumorigenesis. In various experimental cancers, treatment with antagonists of bombesin/gastrin-releasing peptide (BN/GRP) produces a reduction in EGFRs, concomitant to inhibition of tumor growth. To investigate the mechanisms involved, we monitored concentrations of BN/GRP antagonist RC- 3095 in serum of mice, rats, and hamsters given a single subcutaneous or intravenous injection of this analog. In parallel studies, we measured levels and mRNA expression of EGFRs in estrogen-dependent and independent MXT mouse mammary cancers, following a single subcutaneous administration of RC-3095 to tumor-bearing mice. Peak values of RC-3095 in serum were detected 2 min after intravenous or 15 min after subcutaneous injection. The levels of RC-3095 declined rapidly and became undetectable after 3-5 hr. In the estrogen- dependent MXT tumors, the concentration of EGF receptors was reduced by about 60% 6 hr following injection and returned to original level after 24 hr. Levels of mRNA for EGFR fell parallel with the receptor number and were nearly normal after 24 hr. In the hormone-independent MXT cancers, the number of EGFRs decreased progressively, becoming undetectable 6 hr after injection of RC-3095, and returned to normal values at 24 hr, but EGFR mRNA levels remained lower for 48 hr. Thus, in spite of rapid elimination from serum, BN/GRP antagonist RC-3095 can induce a prolonged decrease in levels and mRNA expression of EGFRs. These findings may explain how single daily injections of BN/GRP antagonists can maintain tumor growth inhibition.

Original languageEnglish (US)
Pages (from-to)10913-10918
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number20
StatePublished - Sep 30 1997
Externally publishedYes



  • Blood levels of bombesin antagonist
  • Gastrin releasing peptide antagonist
  • Receptor down-regulation

ASJC Scopus subject areas

  • Genetics
  • General

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