To overcome this problem, Liu et al. developed a matrixmetalloproteinase-2 (MMP-2) responsive tumor-penetrable nanosystem(EALP) to enhance photodynamic cancer immunotherapy by interveningthe cholesterol metabolism in T cells and cancer cells (Table 4).168 The EALP was fabricated by loading AVA and the MMP-2-activatablepeptide (PPa-PLGLAG-iRGD) into liposomes. Here, MMP2 is linked to cancer.