# Taming the Tumor Stroma: A Two-Stage Targeted Nanocapsule for Potent Deep Chemo-Immunotherapy in Triple-Negative Breast Cancer

## TL;DR

A new two-stage nanocapsule targets both tumor cells and cancer-associated fibroblasts in triple-negative breast cancer, improving drug delivery and immune response.

## Contribution

A TME-responsive nanocapsule that sequentially targets CAFs and cancer cells in TNBC is developed.

## Key findings

- NPC-ABS/FDS showed 2.5-fold and 4.3-fold increased uptake of baicalein and doxorubicin, respectively.
- The nanocapsule reduced CAF activation and improved immune cell infiltration in tumors.
- It demonstrated prolonged tumor retention and enhanced drug penetration in TNBC.

## Abstract

Background: The tumor microenvironment (TME) poses significant challenges to effective therapy, with cancer-associated fibroblasts (CAFs) playing a key role in tumor progression and drug resistance in triple-negative breast cancer (TNBC). Herein, a TME responsive nanocapsule, NPC-ABS/FDS, was developed utilizing baicalein, a CAFs modulator, and the cytotoxic drug doxorubicin to selectively target CAFs and tumor cells, respectively, in a stepwise manner. Methods: NPC-ABS/FDS was designed with CD13-mediated primary targeting for tumor accumulation and secondary targeting via σ-receptor binding (ABS nanoparticles) for CAFs and folate modification (FDS nanoparticles) for cancer cells. Physicochemical properties were assessed using TEM, particle size, and ζ-potential analyses. Fluorescence imaging evaluated tumor retention, while cellular uptake and TME modulation were analyzed in vitro and in vivo. Results: The successful preparation of NPC-ABS/FDS was demonstrated by its uniform morphology, stable characteristics, charge reversal, and increased particle size. Fluorescence imaging confirmed prolonged peritumoral retention. Cellular uptake increased 2.5-fold for baicalein in CAFs and 4.3-fold for doxorubicin in cancer cells. NPC-ABS/FDS downregulated α-SMA and FAP, reducing CAFs activation, improving intratumoral drug penetration, and enhancing CD8+ and CD4+ T cell infiltration while decreasing regulatory T cells. Conclusions: NPC-ABS/FDS effectively modulates multiple TME components, including CAFs and immune cells, and improves drug delivery in TNBC. These findings may support the development of improved therapeutic approaches for TNBC.