Peptide inhibition of cytokine-stimulated aromatase activity in breast tissue fibroblasts

• Published in: Journal of steroid biochemistry and molecular biology Vol. 79; no. 1; pp. 165 - 172
• Main Authors: Parish, D, Purohit, A, Singh, A, Rosankiewicz, J, Ghilchik, M.W, Reed, M.J
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2001; Elsevier Science
• Subjects: Amino Acid Sequence; Aromatase; Aromatase - metabolism; Aromatase Inhibitors; Biological and medical sciences; Breast - drug effects; Breast - enzymology; Breast cancer; Cytokine; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - pharmacokinetics; Enzyme Inhibitors - pharmacology; Female; Fibroblasts - drug effects; Fibroblasts - enzymology; Humans; In Vitro Techniques; Interleukin-6 (IL-6); Interleukin-6 - antagonists & inhibitors; Interleukin-6 - pharmacology; Molecular Sequence Data; Peptides - chemistry; Peptides - pharmacokinetics; Peptides - pharmacology; Receptors, Interleukin-6 - antagonists & inhibitors; Receptors, Interleukin-6 - metabolism; Breast cancer; Interleukin-6 (IL-6); Aromatase; Cytokine
• ISSN: 0960-0760; 1879-1220
• DOI: 10.1016/S0960-0760(01)00155-8

The cytokine interleukin-6 (IL-6) and its soluble receptor (IL-6sR) can act synergistically to stimulate aromatase activity in cultured stromal fibroblasts derived from breast tissues. In this study, a 16 amino acid peptide, AROHIB, has been used in an attempt to block the ability of IL-6 plus IL-6sR to stimulate aromatase activity in stromal fibroblasts. Pre-incubation of cells with AROHIB for a 3-h period before the addition of IL-6 and IL-6sR resulted in a marked (67%) reduction in the ability of these factors to stimulate aromatase activity. AROHIB was found to be rapidly degraded when exposed to MCF-7 breast cancer cells or fibroblasts. Analysis by FAB-MS was used to identify the site of peptide cleavage. Subsequently, a series of 10 amino acid peptides, DP1–DP4, were designed, synthesised and tested for their ability to resist proteolytic degradation and to inhibit IL-6 plus IL-6sR-stimulated aromatase activity. Peptide DP2, a modified version of the active fragment of AROHIB, had N-acetyl and C-amino terminal protection and an internal d-amino acid (instead of l form) at the site of proteolytic cleavage. Using cells cultured in the presence of 2% stripped foetal calf serum, peptide DP2 resulted in a 74% reduction in cytokine-stimulated aromatase activity. Under serum-free conditions, peptides DP1–DP3 showed modest inhibitory properties. Results from this study suggest that it may be possible to develop small peptides to inhibit cytokine-stimulated aromatase activity in a tissue-specific manner.