Targeted destruction of prostate cancer cells and xenografts by lytic peptide-betaLH conjugates
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Published on: September 3, 2013
W Hansel1, C Leuschner, B Gawrońska
1Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, USA. hanselw@pbrc.edu
Abstract:
In series of experiments conducted in vitro, we have established the concept that conjugates of the lytic peptides Hecate or Phor14 with a fragment of the beta chain of LH (amino acids 80-94) selectively destroy both androgen sensitive and insensitive human prostate cancer cells. Extraction of steroids from the culture medium by charcoal reduced the ability of the conjugates to kill LNCaP, BRF41T and PC-3 cells. Addition of hormones known to up-regulate LH receptors (estradiol, testosterone or FSH) to the culture medium restored the ability of the conjugates to kill these cell lines. The toxicity of the conjugates (EC(50)) to these cell lines was closely correlated to their LH binding capacities (f mol/10(6) cells). In series of in vivo experiments we have shown that both the Hecate and Phor14-betaLH conjugates are remarkably effective in causing tumor cell necrosis and cessation of tumor growth in nude athymic mice. Treatment with Hecate-betaLH (12 mg/kg body weight) resulted in a reduction of tumor burden (mg tumor/g body weight) from 60 to 14 (P<0.0001); treatment with Phor14-betaLH (12 mg/kg body weight) reduced tumor burden to 27 mg (P<0.0001). Treatment with a high dose of Phor14-betaLH (24 mg/kg body weight) reduced the tumor burden from 60 to 12 mg/kg P<0.0001). Pretreatment of animals receiving a low dose of Phor14-betaLH (12 mg/kg) with either estradiol or follicle stimulating hormone, (FSH) resulted in reduction of tumor burden from 60 to 11 mg/kg. Administration of a second 3-week treatment after a one month recovery period caused complete regression of more than 75 percent of the tumors. No changes in body weight or histological abnormalities were found in any of the organs examined, except the testes.
Insights
Novel peptide conjugates targeting luteinizing hormone (LH) receptors selectively destroy prostate cancer cells in vitro and in vivo. Hormonal regulation of LH receptors influences conjugate efficacy, suggesting a targeted therapy approach for prostate cancer.
Area of Science:
- Oncology
- Molecular Biology
- Endocrinology
Background:
- Prostate cancer cells, both androgen-sensitive and insensitive, present a significant therapeutic challenge.
- Targeting specific cell surface receptors offers a potential strategy for selective cancer cell destruction.
- Luteinizing hormone (LH) receptors are expressed on prostate cancer cells, indicating a potential therapeutic target.
Purpose of the Study:
- To investigate the efficacy of lytic peptide conjugates (Hecate or Phor14) linked to a beta-chain fragment of LH (betaLH) in targeting and destroying prostate cancer cells.
- To explore the role of steroid hormones and LH receptor expression in the therapeutic activity of these conjugates.
- To evaluate the in vivo efficacy and safety of Hecate-betaLH and Phor14-betaLH conjugates in a mouse model.
Main Methods:
- In vitro studies using human prostate cancer cell lines (LNCaP, BRF41T, PC-3) treated with Hecate-betaLH and Phor14-betaLH conjugates.
- Steroid extraction and hormone addition (estradiol, testosterone, FSH) to assess the influence on conjugate-mediated cell killing.
- In vivo experiments in nude athymic mice bearing prostate tumors, evaluating tumor burden reduction, and assessing toxicity.
Main Results:
- Conjugates of Hecate or Phor14 with betaLH selectively destroyed androgen-sensitive and insensitive prostate cancer cells in vitro.
- Conjugate efficacy correlated with LH receptor binding capacity and was modulated by steroid hormones.
- In vivo administration of Hecate-betaLH and Phor14-betaLH conjugates significantly reduced tumor burden and induced tumor regression, with no significant systemic toxicity observed except in testes.
Conclusions:
- Lytic peptide-betaLH conjugates represent a promising targeted therapy for prostate cancer, effectively killing cancer cells both in vitro and in vivo.
- The efficacy of these conjugates is dependent on LH receptor expression and can be enhanced by hormonal modulation.
- Further investigation into these conjugates could lead to novel therapeutic strategies for prostate cancer treatment.
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