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Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
Published on: July 26, 2017
Functional pH-Responsive Nanoparticles for Immune Reprogramming in MSS Colorectal Cancer via ER Stress-Induced
Yu-Li Lo1,2,3, Hua-Ching Lin4,5, Ching-Yao Li1
1Department and Institute of Pharmacology, National Yang Ming Chiao Tung University, Taipei 112, Taiwan.
Abstract:
Background: Colorectal cancer (CRC), particularly the microsatellite-stable (MSS) subtype, remains largely unresponsive to immune checkpoint inhibitors (ICIs) due to immune escape, tumor-associated macrophage (TAM) enrichment, and cytokine-driven suppression that sustain a TAM-dominant tumor microenvironment (TME). To overcome these barriers, a pH-responsive solid lipid nanoparticle (SLN) system was engineered to co-deliver CB-5083 (a VCP/p97 inhibitor), miR-142 (a PD-L1-targeting microRNA), and imiquimod (R, a TLR7 agonist) for spatially confined induction of endoplasmic reticulum stress (ERS) and immune reprogramming in MSS CRC. Methods: The SLNs were coated with PEG-PGA for pH-triggered de-shielding and functionalized with PD-L1- and EGFR-binding peptides plus an ER-homing peptide, enabling tumor-selective and subcellular targeting. Results: The nanoplatform displayed acid-triggered PEG-PGA detachment, selective CRC/TAM uptake, and ER localization. CB-mediated VCP inhibition activated IRE1α/XBP1s/LC3II, PERK/eIF2α/ATF4/CHOP, and JNK/Beclin signaling, driving apoptosis and autophagy, while miR-142 suppressed PD-L1 expression and epithelial-mesenchymal transition markers. R facilitated dendritic cell maturation and M1 polarization. Combined CB + miR + R/SLN-CSW suppressed IL-17, G-CSF, and CXCL1, increased infiltration of CD4+ and CD8+ T cells, reduced Tregs and M2-TAMs, and inhibited tumor growth in CT-26 bearing mice. The treatment induced immunogenic cell death, reprogramming the TME into a T cell-permissive state and conferring resistance to tumor rechallenge. Biodistribution analysis confirmed tumor-preferential accumulation with minimal off-target exposure, and biosafety profiling demonstrated low systemic toxicity. Conclusions: This TME-responsive nanoplatform therefore integrates ERS induction, checkpoint modulation, and cytokine suppression to overcome immune exclusion in MSS CRC, representing a clinically translatable strategy for chemo-immunotherapy in immune-refractory tumors.
Insights
A novel pH-responsive nanoparticle delivers a VCP inhibitor, miR-142, and imiquimod to reprogram the tumor microenvironment. This combination therapy overcomes immune exclusion in microsatellite-stable colorectal cancer, enhancing anti-tumor immunity and reducing tumor growth.
Area of Science:
- Oncology
- Nanotechnology
- Immunotherapy
Background:
- Microsatellite-stable colorectal cancer (MSS CRC) exhibits resistance to immune checkpoint inhibitors (ICIs) due to immune evasion, tumor-associated macrophage (TAM) enrichment, and a suppressive tumor microenvironment (TME).
- Existing therapies struggle to overcome immune exclusion in MSS CRC, necessitating novel strategies to reprogram the TME and enhance anti-tumor immune responses.
Purpose of the Study:
- To engineer a pH-responsive solid lipid nanoparticle (SLN) system for co-delivery of CB-5083 (VCP/p97 inhibitor), miR-142 (PD-L1 inhibitor), and imiquimod (TLR7 agonist).
- To achieve spatially confined induction of endoplasmic reticulum stress (ERS) and immune reprogramming within the TME of MSS CRC.
- To develop a clinically translatable strategy for chemo-immunotherapy in immune-refractory tumors.
Main Methods:
- SLNs were coated with PEG-PGA for pH-triggered de-shielding and functionalized with targeting peptides (PD-L1, EGFR, ER-homing).
- The nanoplatform was designed for selective tumor uptake, TAM targeting, and subcellular ER localization.
- Combination therapy (CB-5083 + miR-142 + imiquimod) was evaluated in CT-26 bearing mice models.
Main Results:
- The nanoplatform demonstrated acid-triggered de-shielding, selective uptake by CRC and TAMs, and ER localization.
- CB-5083 induced apoptosis and autophagy via ERS signaling pathways; miR-142 suppressed PD-L1 and EMT markers; imiquimod promoted dendritic cell maturation and M1 polarization.
- Combined therapy significantly suppressed tumor growth, reduced immunosuppressive cytokines, increased CD4+/CD8+ T cell infiltration, decreased Tregs and M2-TAMs, induced immunogenic cell death, and conferred resistance to tumor rechallenge.
Conclusions:
- The developed TME-responsive nanoplatform effectively integrates ERS induction, checkpoint modulation, and cytokine suppression to overcome immune exclusion in MSS CRC.
- This strategy reprograms the TME into a T cell-permissive state, offering a promising approach for chemo-immunotherapy in immune-refractory tumors.
- The nanoplatform exhibited tumor-preferential accumulation, minimal off-target exposure, and low systemic toxicity, indicating clinical translatability.
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