2 research outputs found
Doxorubicin conjugated with a trastuzumab epitope and an MMP-2 sensitive peptide linker for the treatment of HER2-positive breast cancer
<p>HER2-positive breast cancer correlates with more aggressive tumor growth, a poorer prognosis and reduced overall survival. Currently, trastuzumab (Herceptin), which is an anti-HER2 antibody, is one of the key drugs. There is evidence indicating that conjugation of trastuzumab with chemotherapy drugs, such as doxorubicin (DOX), for multiple targets could be more effective. However, incomplete penetration into tumors has been noted for those conjugates. Compared to an antibody, peptides may represent an attractive alternative. For HER2, a similar potency has been observed for a 12-amino-acid anti-HER2 peptide mimetic Y<u>C</u>DGFYA<u>C</u>YMDV-NH<sub>2</sub> (AHNP, disulfide-bridged) and full-length trastuzumab. Thus, a peptide, GPLGLAGDDY<u>C</u>DGFYA<u>C</u>YMDV-NH<sub>2</sub>, which consists of AHNP and an MMP-2 cleavable linker GPLGLAGDD, was first designed, followed by conjugation with DOX <i>via</i> a glycine residue at the N-terminus to form a novel DOX-peptide conjugate MAHNP-DOX. Using HER2-positive human breast cancer cells BT474 and SKBR3 as <i>in vitro</i> model systems and nude mice with BT474 xenografts as an <i>in vivo</i> model, this conjugate was comprehensively characterized, and its efficacy was evaluated and compared with that of free DOX. As a result, MAHNP-DOX demonstrated a much lower <i>in vitro</i> IC<sub>50</sub>, and its <i>in vivo</i> extent of inhibition in mice was more evident. During this process, enzymatic cleavage of MAHNP-DOX is critical for its activation and cellular uptake. In addition, a synergistic response was observed after the combination of DOX and AHNP. This effect was probably due to the involvement of AHNP in the PI3K–AKT signaling pathway, which can be largely activated by DOX and leads to anti-apoptotic signals.</p
Acid-Sensitive Peptide-Conjugated Doxorubicin Mediates the Lysosomal Pathway of Apoptosis and Reverses Drug Resistance in Breast Cancer
The extended use of doxorubicin (DOX)
could be limited because
of the emergence of drug resistance associated with its treatment.
To reverse the drug resistance, two thiol-modified peptide sequences
HAIYPRHGGC and THRPPMWÂSPVWPGGC were, respectively, conjugated
to DOXO-EMCH, forming a maleimide bridge in this study (i.e., T10-DOX
and T15-DOX). The structures and properties of peptide–DOX
conjugates were characterized using <sup>1</sup>H NMR, <sup>13</sup>C NMR, mass spectrometry, and high-performance liquid chromatography.
Their stability was also evaluated. By using MCF-7/ADR cells as an <i>in vitro</i> model system and nude mice bearing MCF-7/ADR xenografts
as an <i>in vivo</i> model, the ability of these novel peptide–DOX
conjugates to reverse drug resistance was accessed as compared with
free DOX. As a result, the IC<sub>50</sub> values for T10-DOX and
T15-DOX significantly decreased (31.6 ± 1.6 μM and 27.2
± 0.8 μM), whereas the percentage of apoptotic cell population
increased (35.4% and 39.3%). The <i>in vivo</i> extent of
inhibition was more evident in the mice groups treated with peptide–DOX
conjugates (59.6 ± 8.99% and 46.4 ± 6.63%), which had DOX
primarily accumulated in tumor. These conjugates also showed a longer
half-life in plasma and cleared much more slowly from the body. Furthermore,
T10-DOX may be more effective than T15-DOX with a higher efficacy
and a lower side effect. Most importantly, evidence was provided to
support the enhanced intracellular drug accumulation and the induction
of lysosomal pathway of apoptosis underlying the drug resistance.
As an endosomal/lysosomal marker, cathepsin D permealized the destabilized
organelle membrane and was detected in the cytoplasm, leading to the
activation of the effector caspase-3 in cell apoptosis. This report
is among the first to demonstrate that peptide–DOX-like conjugates
promote apoptosis through the initiation of the lysosomal pathway