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Yang et al.
MDB5 was in the range of 30–50 mM. This means the IC50 and MDB5 could synergistically treat chemoresistant prostate
values of these two drugs have an approximately 300- to cancer in vivo, and mPEG-p(TMC-MBC) could serve as an
600-fold difference. Therefore, we used 1:200, 1:300, and 1:400 effective delivery vehicle to boost anticancer activity of the two
ratios for vitro combination therapy with QW-296 and MDB5. drugs rather than cosolvent.
We determined the synergism between these two drugs
Conclusion
strengthened our hypothesis. In the cell cycle analysis,
QW-296 and MDB5 made distinct impacts on the cell cycle;
MDB5 treatment caused G0/G1 phase arrest while QW-296
treatment led to G2/M phase arrest (Fig. 4, B and C), which
demonstrated the two anticancer agents worked at a comple-
mentary mechanism of action against PC3-TXR cells. This
result was in agreement with the previous reports.
Further, we analyzed the change in protein expression to
highlight the combination advantage at the molecular level.
We observed down-regulation of Shh (Fig. 4D), a key compo-
nent of the Hh signaling pathway, after MDB5 monotherapy
or the combination of QW-296 and MDB5.
Although QW-296 and MDB5 have demonstrated excel-
lent synergy in anticancer activity against chemoresistant
prostate cancer, their clinical translation will be limited due
to their intrinsic poor aqueous solubility, like many other
anticancer agents. To solve this problem, nanocarrier-based
therapeutic systems have emerged over several decades as a
promising platform for delivering hydrophobic drugs. In this study,
we developed an amphiphilic copolymer mPEG-p(TMC-MBC)
to encapsulate two hydrophobic small molecules, thereby form-
ing polymeric micelles in aqueous solution that are suitable for
systemic drug delivery.
In the present study, we successfully synthesized and
screened the novel microtubule destabilizer QW-296 and an
Hh pathway inhibitor MDB5 and demonstrated their anti-
cancer activities in combination or individually. We success-
fully synthesized mPEG-p(TMC-MBC) and formed polymeric
micelles to encapsulate QW-296 and MDB5 with payloads of
8.13% 6 0.75% and 9.12% 6 0.69% (w/w), respectively. The
overall findings indicated that the combination of QW-296
and MDB5 exhibited a synergistic therapeutic effect against
chemoresistant prostate cancer via different mechanisms,
and with the help of mPEG-p(TMC-MBC) the combination
could effectively inhibit the growth of chemoresistant prostate
cancer.
Authorship Contributions
Participated in research design: Yang, Chen, Guo, Li, Mahato.
Conducted experiments: Yang, Chen, Guo, Dong.
Contributed new reagents or analytic tools: Yang, Dong, Miller, Li.
Performed data analysis: Yang, Chen, Miller, Li, Mahato.
Wrote or contributed to the writing of the manuscript: Yang, Li,
Mahato.
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We used mPEG as the hydrophilic backbone, and the long
length enabled us to synthesize the copolymer with a molec-
ular mass in the range of 10,000–11,000 Da. Its stealth-like
property is expected to prolong the circulation time of mi-
celles and consequently increase the drug’s accumulation in
tumor tissue. On the other hand, TMC and MBC are both
cyclic carbonate blocks that provide desired hydrophobicity
to encapsulate lipophilic molecules in the core and balance
hydrophilic composition. Furthermore, polycarbonates have
been proven to be nontoxic, biocompatible, and biodegradable,
which provides potential for future clinical translation. They
degrade into carbon dioxide and benzyl alcohol, which have
less effect on microenvironment pH and as such will not result
in local inflammation and are easily cleared from the body.
Our results also confirmed that mPEG-p(TMC-MBC) poly-
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and sustained the drug release in acidic or neutral conditions
(Fig. 6).
To better investigate the combination efficacy and confirm
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treatment groups exhibited excellent tumor inhibitory results
(Fig. 7). However, combination therapy in micelles showed
significantly enhanced reduction in tumor size compared with
the combination in cosolvent as well as QW-296 or MDB5
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Apart from tumor growth suppression, H&E stain of vital
organs demonstrated the micelles carrying QW-296 and
MDB5 were well tolerated, as the other healthy organs
showed no obvious histologic changes after the treatments.
These results strongly support our hypothesis that QW-296