Often
cancer relapses after an initial response to
chemotherapy because of the
tumor's heterogeneity and the presence of progenitor stem cells, which can renew. To overcome drug resistance,
metastasis, and relapse in
cancer, a promising approach is the inhibition of
cancer stemness. In this study, the expression of the
neuropilin-1 receptor in both pancreatic and
prostate cancer stem cells was identified and targeted with a stimuli-responsive, polymeric nanocarrier to deliver a stemness inhibitor (
napabucasin) to cancer stem cells. Reduction-sensitive amphiphilic block copolymers PEG1900-S-S-PLA6000 and the N3-PEG1900-PLA6000 were synthesized. The
tumor penetrating
iRGD peptide-hexynoic
acid conjugate was linked to the N3-PEG1900-PLA6000
polymer via a Cu2+ catalyzed "Click" reaction. Subsequently, this
peptide-
polymer conjugate was incorporated into polymersomes for
tumor targeting and tissue penetration. We prepared polymersomes containing 85% PEG1900-S-S-PLA6000, 10% iRGD-
polymer conjugate, and 5%
DPPE-lissamine
rhodamine dye. The iRGD targeted polymersomes encapsulating the
cancer stemness inhibitor
napabucasin were internalized in both prostate and
pancreatic cancer stem cells. The
napabucasin encapsulated polymersomes significantly (p < .05) reduced the viability of both prostate and
pancreatic cancer stem cells and decreased the stemness
protein expression notch-1 and nanog compared to the control and vesicles without any drug. The
napabucasin encapsulated polymersome formulations have the potential to lead to a new direction in prostate and
pancreatic cancer therapy by penetrating deeply into the
tumors, releasing the encapsulated stemness inhibitor, and killing cancer stem cells.