Neuropeptide Antagonists for Cancer Treatment.
Small Cell Lung Cancer (SCLC) is an aggressive form
of cancer accounting for 25% of lung cancer deaths worldwide.
Treatment relies on combination chemotherapy (etoposide and
cisplatin or carboplatin) with or without radiation therapy.
However, disease relapse and resistance occurs quickly, prompting
unmet need for alternative treatment options. One such option is
the use of broad-spectrum antagonists, known as Substance P (SP)
analogues. Historically, these analogues have not succeeded
clinically due to low potency and bioavailability. In this project,
novel SP analogues were developed to address these shortfalls. A
chemical strategy was designed to synthesise novel short peptides
including DMePhe-DTrp-Phe-DTrp-Leu-NH2 (25) as the new lead. Fmoc
and Boc D-Trp derivatives with indole nitrogen having substituents
(methyl, ethyl, propyl, butyl, pentyl, propargyl, benzyl and
tert-prenyl) were made and characterised by 1H and 13C NMR
spectroscopy and mass spectrometry (MS). These building blocks were
incorporated into the first series of peptides, substituting the
D-Trp residue located near the C-terminal of 25, via solid and/or
liquid phase procedures. Final products were purified by RP-HPLC to
>90% purity and structures verified by MS and/or 1H NMR. Cell
viability assays were conducted to evaluate cytotoxicity against
two SCLC cell lines: H69 (chemo-naive) and DMS79 (from a patient
after treatment). The IC50 values for the D-Trp residue modified
peptides were <5 ÂµM. One of the earliest candidates to emerge
from this work was DMePhe-DTrp-Phe-DTrp(N-tert-prenyl)-Leu-NH2
(33). Subsequently, the most potent peptide was the one bearing
D-Trp(N-butyl) (29) with IC50 values of 1.0 ÂµM (H69) and 1.4 ÂµM
(DMS79), compared to the lead 25 with IC50 values of 30.7 ÂµM (H69)
and 23.0 ÂµM (DMS79). A second series of peptides were produced to
optimise 29 by incorporating a D-Trp(N-butyl) residue. The study
focused on peptides by (a) modifying the N-terminal D-Trp residue,
(b) modifying both D-Trp residues, (c) changing the C-terminal
amide to free carboxylic acid, and (d) adding a charged amino acid
(arginine) or removing a hydrophobic amino acid (leucine) to
additionally aid in solubility. The most potent candidate was found
to bear dual D-Trp(N-butyl) residues (35) with IC50 value of 0.6
ÂµM (H69) and 2.3 ÂµM (DMS79). Peptides 29 and 35 were at least 26
times more potent than SP antagonist G (SPG, previously subjected
to a Phase I clinical trial), as revealed by in vitro screening in
this project. Both sequences induced apoptosis as evident from
fluorescence staining. Flow cytometric analysis of 29 with the
DMS79 cell line showed that the level of late apoptotic cells rose
from 36% at 2 ÂµM to 96% at 6 ÂµM, compared to 25 that exhibited no
effect. Efficacy of peptide 33 was separately evaluated in vivo
using DMS79 xenografts. A low dose (1.5 mg/kg) was found to reduce
tumour growth by âˆ¼30% (p < 0.05) at day 7, relative to the
control group. Higher doses could not be used due to limited
aqueous solubility. Furthermore, these…
Advisors/Committee Members: FREEMAN, SALLY S, Aojula, Harmesh.
to Zotero / EndNote / Reference
APA (6th Edition):
Abusara, O. (2017). Neuropeptide Antagonists for Cancer Treatment. (Doctoral Dissertation). University of Manchester. Retrieved from http://www.manchester.ac.uk/escholar/uk-ac-man-scw:310464
Chicago Manual of Style (16th Edition):
Abusara, Osama. “Neuropeptide Antagonists for Cancer Treatment.” 2017. Doctoral Dissertation, University of Manchester. Accessed May 20, 2018.
MLA Handbook (7th Edition):
Abusara, Osama. “Neuropeptide Antagonists for Cancer Treatment.” 2017. Web. 20 May 2018.
Abusara O. Neuropeptide Antagonists for Cancer Treatment. [Internet] [Doctoral dissertation]. University of Manchester; 2017. [cited 2018 May 20].
Available from: http://www.manchester.ac.uk/escholar/uk-ac-man-scw:310464.
Council of Science Editors:
Abusara O. Neuropeptide Antagonists for Cancer Treatment. [Doctoral Dissertation]. University of Manchester; 2017. Available from: http://www.manchester.ac.uk/escholar/uk-ac-man-scw:310464