Table 3.

CAR-T cell therapy Challenges and strategies in breast cancer.

Challenge	Strategies
Trafficking and infiltration	Designing better matched chemokine receptors on CAR-T cell.
	Using oncolytic viruses to drive CAR-T cells traffic to tumor sites.
	Local administration.
	Constructing CARs to degrades extracellular matrix of tumor cells.
	Targeting the fibroblast activation protein.
Tumor immunosuppressive microenvironment	Constructing T cells with TGFβ receptor.
	Introducing cytokines (such as IL-2, IL-15, IL-12) neutralize immunosuppressive factors.
	Combing with checkpoint inhibitors.
Tumor antigen heterogeneity	Developing multitarget CAR-T cells.
Toxicities	Developing multitarget CAR-T cells.
	Developing affinity-tuned CAR-T cells.
	Developing inhibitory CAR-T cells.
	Introducing suicide genes to CAR-T cells.
	Using transient RNA expression of CARs.