CD44 and neoplasm: Ren et al.27 designed and synthesized a tumor-targeting and hypoxia-responsive peptide-photosensitizer coupling, A6-dMP-VP, which consists of a CD44 targeting motif, A6, a tumor lysing peptide, dMP, a hypoxia-responsive motif, and a photosensitizer, vitexoporfin (VP), which self-assembles into nanoparticles and is preferentially enriched in 4T1 tumors.