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Enzymatic stability, solution structure, and antiproliferative effect on prostate cancer cells of leuprolide and new gonadotropin‐releasing hormone peptide analogs
Author(s) -
Pappa Eleni V.,
Zompra Aikaterini A.,
Spyranti Zinovia,
Diamantopoulou Zoi,
Pairas George,
Lamari Fotini N.,
Katsoris Panagiotis,
Spyroulias Georgios A.,
Cordopatis Paul
Publication year - 2011
Publication title -
peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.21521
Subject(s) - chemistry , prostate cancer , peptide , enzyme , hormone , gonadotropin releasing hormone , prostate , peptide hormone , medicine , biochemistry , endocrinology , cancer research , cancer , luteinizing hormone , biology
Analogs of GnRH, including [DLeu 6 , des Gly 10 ]‐GnRH‐NHEt (leuprolide, commercial product), have been widely used in oncology to induce reversible chemical castration. Several studies have provided evidence that, besides their pituitary effects, GnRH analogs may exert direct antiproliferative effects on tumor cells. To study the effect of modifications in positions 4 and 6 of leuprolide on prostate cancer cell proliferation, we synthesized 12 new leuprolide analogs. All GnRH analogs lacked the carboxy‐terminal Gly 10 ‐amide of GnRH, and an ethylamide residue was added to Pro 9 . Gly 6 was substituted by DLys, N ε ‐modified DLys, Glu, and DGlu. To improve the enzymatic stability, NMeSer was incorporated in position 4, and the rate of hydrolysis by α‐chymotrypsin and subtilisin was investigated. Our results demonstrate that this incorporation increases enzymatic stability in all analogs of GnRH, whereas the antiproliferative effect on PC3 and LNCaP prostate cancer cells is similar to that of leuprolide. Conformational studies were performed to elucidate structural changes occurring on substitution of native residues and to study structure–activity relationship for these analogs. The solution models of [DLeu 6 , des Gly 10 ]‐GnRH‐NHEt (leuprolide), [NMeSer 4 , DGlu 6 , des Gly 10 ]‐GnRH‐NHEt, [Glu 6 , des Gly 10 ]‐GnRH‐NHEt, and [DGlu 6 , des Gly 10 ]‐GnRH‐NHEt peptides were determined through two‐dimensional nuclear magnetic resonance spectroscopy in dimethylsulfoxide. Nuclear magnetic resonance data provide experimental evidence for the U‐turn‐like structure appeared in all four analogs, which could be characterized as β‐hairpin conformation. The most stable analog [NMeSer 4 , DGlu 6 , des Gly 10 ]‐GnRH‐NHEt against proteolytic cleavage forms a second extra backbone turn observed for residues 1–4. © 2010 Wiley Periodicals,Inc. Biopolymers (Pept Sci) 96: 260–272, 2011.