Part A: Synthesis and characterization of self-assembling peptides Part B: Studies of antiproliferative mechanisms of lamellarin D and lamellarin Chi in human breast cancer cell linesJarinee Maneekul
( M.Sc. )
This thesis is composed of two parts. The main aims of part A, the Self-Assembling Peptide Project, were to find the best candidate and the most appropriate system and conditions for self-assembly that could be further developed as a drug conjugating system in the future. The purpose of part B, the Lamellarins Project, was to investigate the antiproliferative mechanisms of selected lamellarin natural products in two breast cancer cell lines, which are different in their hormone dependency. For part A, four self-assembling peptides, namely KL8, EL8, TL8, and ELKL4, were designed, synthesized, and biophysically characterized by spectroscopic and microscopic techniques. Based on all the studies, KL8 was found to be the best candidate owing to its desirable structure and stability. It could form β-sheet secondary structure and assemble properly under both normal physiological and cancer-relevant conditions, but disassembled under strong acidic conditions. Furthermore, the results from the chaotrope-induced denaturation studies showed that assembly/disassembly of peptide occurred through the classical mechanism called “β-sheet induced peptide self-assembly”. For part B, there were three main steps in this study, starting with the determination of the fifty percent inhibitory concentration (IC50) of two lamellarins on in vitro growth of T47D and MDA-MB-231 human breast cancer cell lines. The second step involved protein expression study using western immunoblotting analysis technique. The third step was flow cytometry analysis to confirm the effect of lamellarins on cell cycle progression. The results showed that lamellarin D and lamellarin Chi inhibited the growth of breast cancer cells by down-regulating ERα, along with up-regulating ERβ. Additionally, lamellarin D arrested cell cycle progression mainly at G2/M transition in MDA-MB-231 cells, while lamellarin Chi could arrest at both G1 phase and G2/M transition in MDA-MB-231 cells. Furthermore, both compounds exhibited apoptotic promoting effect in breast cancer cell lines.
Self-assembling peptides / biophysical characterization / stability study / spectroscopy / peptide synthesis / lamellarin D / lamellarin Chi / T47D / MDA-MB-231 / antiproliferative mechanisms