TGFB1 and cancer: It has been reported that CAFs may be the critical factor in this phenomenon.[13, 20] CAFs activated by TGF‐β secreted from cancer cells could produce a dense ECM to increase the interstitial fluid pressure within the tumor and limit the delivery of NPs.[21] This activated status of CAFs was mainly achieved through reactive oxygen species (ROS) generated by the TGF‐β signaling pathway,[22] which is illustrated in Figure 5A.