Blood vessels in the tumor periphery have high pericyte coverage and are resistant to vascular disrupting agents (VDAs). VDA treatment resistance leads to a viable peripheral tumor rim that contributes to treatment failure and disease recurrence. Here, we provide evidence to support a hypothesis that shifting the target of VDAs from tumor vessel endothelial cells to pericytes disrupts tumor peripheral vessels and the viable rim, circumventing VDA treatment resistance. Through chemical engineering, we developed Z-GP-DAVLBH (from the tubulin-binding VDA desacetylvinblastine monohydrazide [DAVLBH]) as a prodrug that can be selectively activated by fibroblast activation protein α (FAPα) in tumor pericytes. Z-GP-DAVLBH selectively destroys the cytoskeleton of FAPα-expressing tumor pericytes, disrupting blood vessels both within the core and around the periphery of tumors. As a result, Z-GP-DAVLBH treatment eradicated the otherwise VDA-resistant tumor rim and led to complete regression of tumors in multiple lines of xenografts without producing the drug-related toxicity that is associated with similar doses of DAVLBH. This study demonstrates that targeting tumor pericytes with an FAPα-activated VDA prodrug represents a potential vascular disruption strategy in overcoming tumor resistance to VDA treatments.

Photoaffinity labeling (PAL) has been widely applied in various research areas such as medicinal chemistry, chemical biology and structural biology, owing to its capability of investigating non-covalent ligand–protein interactions under native environments and elucidating protein structures, functions etc. One important application of this technique is to use affinity-based proteome profiling (AfBP) coupled with bioimaging for profiling drug–target interactions in situ. In order to accurately report drug–target interactions via these approaches, several considerations as follows need to be made: (1) maximally retaining bioactivities of photoprobes upon functionalization with a photoreactive group and a reporter tag from a parental compound; (2) performing proteome profiling and imaging in situ simultaneously, to monitor drug–target interactions in different manners; and (3) developing excellent photo-crosslinkers capable of photo-crosslinking and fluorescence turn-on at the same time. With these considerations in mind, we have developed three versions of “minimalist” bioorthogonal handle-containing photo-crosslinkers (L3–L6) during the years and successfully applied them in all kinds of small bioactive molecules for protein labeling and cellular imaging studies. In this mini-review, the features and functions of these linkers are specifically highlighted and summarized.