melitten and Adrenal-Cortex-Neoplasms

Lytic peptide Hecate (23-amino acid (AA)) fused with a 15-AA fragment of human chorionic gonadotropin-beta (CG-beta), Hecate-CGbeta conjugate (H-CGbeta-c) selectively binds to and destroys tumor cells expressing LH/chorionic gonadotropin receptor (Lhcgr). Transgenic mice (6.5 month old) expressing SV40 T-antigen under the inhibin-alpha promoter (inhalpha/Tag) presenting with Lhcgr expressing adrenal tumors were treated either with H-CGbeta-c, GnRH antagonist (GnRH-a), estradiol (E(2); only females) or their combinations for 1 month. We expected that GnRH-a or E(2) in combination with H-CGbeta-c could improve the treatment efficacy especially in females by decreasing circulating LH and eliminating the potential competition of serum LH with the H-CGbeta-c. GnRH-a and H-CGbeta-c treatments were successful in males (adrenal weights 14 +/- 2.8 mg and 60 +/- 26 vs 237 +/- 59 mg in controls; P < 0.05). Histopathologically, GnRH-a apparently destroyed the adrenal parenchyma leaving only the fibrotic capsule with few necrotic foci. In females, H-CGbeta-c was totally ineffective, whereas GnRH-a (19 +/- 5 mg) or E(2) (77 +/- 50 mg) significantly reduced the adrenal weights compared with controls (330 +/- 70 mg). Adrenal morphometry, cell proliferation markers, post-treatment suppression of serum progesterone, and quantitative RT-PCR of GATA-4, Lhcgr, and GATA-6 further supported the positive outcome. H-CGbeta-c selectively killed the Lhcgr expressing tumor cells, whereas GnRH-a blocked tumor progression through gonadotropin suppression, emphasizing the gonadotropin dependency of these adrenocortical tumors. If extrapolated to humans, H-CGbeta-c could be considered for the treatment of gonadotropin-dependent adrenal tumors in males, whereas in females gonadotropin suppression, but not H-CGbeta-c, would work better.

Topics: Adrenal Cortex Neoplasms; Animals; Antigens, Viral, Tumor; Cell Proliferation; Chorionic Gonadotropin, beta Subunit, Human; Female; Gonadotropin-Releasing Hormone; Gonadotropins; Humans; Immunoenzyme Techniques; Inhibins; Male; Melitten; Mice; Mice, Inbred C57BL; Mice, Transgenic; Progesterone; Promoter Regions, Genetic; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Simian virus 40

Novel strategies are needed for the treatment of adrenocortical tumors that are usually resistant to chemotherapy. Hecate, a 23-amino acid lytic peptide, was conjugated to the 15-amino acid (81-95) fragment of the human chorionic gonadotropin beta (CGbeta) chain, which would selectively kill cancer cells expressing the LH receptor (LHR) sparing the normal ones with LHR. To prove the principle that Hecate-CGbeta conjugate may eradicate tumors ectopically expressing plasma membrane receptors, transgenic (TG) inhibin alpha-subunit promoter (inhalpha)/Simian Virus 40 T-antigen mice, expressing LHR in their adrenal gland tumors, were used as the experimental model. Wild-type control littermates and TG mice with adrenal tumors were treated with either Hecate or Hecate-CGbeta conjugate at the age of 6.5 months for 3 weeks and killed 7 days after the last treatment. The Hecate-CGbeta conjugate reduced the adrenal tumor burden significantly in TG male but not in female mice, in comparison with Hecate-treated mice. Hecate-CGbeta conjugate treatment did not affect normal adrenocortical function as the serum corticosterone level between Hecate and Hecate-CGbeta conjugate groups were similar. The mRNA and protein expressions of GATA-4 and LHR colocalized only in tumor area, and a significant downregulation of gene expression was found after the Hecate-CGbeta conjugate in comparison with Hecate- and/or non-treated adrenal tumors by western blotting. This finding provides evidence for a selective destruction of the tumor cells by the Hecate-CGbeta conjugate. Hereby, our findings support the principle that Hecate-CGbeta conjugate is able to specifically destroy tumor cells that ectopically express LHR.

Topics: Adrenal Cortex Neoplasms; Adrenocortical Adenoma; Animals; Antineoplastic Agents; Chorionic Gonadotropin, beta Subunit, Human; Disease Models, Animal; Female; GATA4 Transcription Factor; Gene Expression Regulation, Neoplastic; Luteinizing Hormone; Male; Melitten; Mice; Mice, Inbred C57BL; Mice, Transgenic; Receptors, LH; RNA, Messenger