A Comparative Analysis of Fibroblast Activation Protein-Targeted Small Molecule-Drug, Antibody-Drug, and Peptide-Drug Conjugates.

We present the first in vivo comparative evaluation of chemically defined antibody-drug conjugates (ADCs), small molecule-drug conjugates (SMDCs), and peptide-drug conjugates (PDCs) targeting and activated by fibroblast activation protein (FAP) in solid tumors. Both the SMDC (OncoFAP-Gly-Pro-MMAE) and the ADC (7NP2-Gly-Pro-MMAE) candidates delivered high amounts of active payload (i.e., MMAE) selectively at the tumor site, thus producing a potent antitumor activity in a preclinical cancer model.

Immunomodulatory Responses of Subcapsular Sinus Floor Lymphatic Endothelial Cells in Tumor-Draining Lymph Nodes.

Tumor-draining lymph nodes (LNs), composed of lymphocytes, antigen-presenting cells, and stromal cells, are highly relevant for tumor immunity and the efficacy of immunotherapies. Lymphatic endothelial cells (LECs) represent an important stromal cell type within LNs, and several distinct subsets of LECs that interact with various immune cells and regulate immune responses have been identified. In this study, we used single-cell RNA sequencing (scRNA-seq) to characterize LECs from LNs draining B16F10 melanomas compared to non-tumor-draining LNs. Several upregulated genes with immune-regulatory potential, especially in LECs lining the subcapsular sinus floor (fLECs), were identified and validated. Interestingly, some of these genes, namely, podoplanin, CD200, and BST2, affected the adhesion of macrophages to LN LECs in vitro. Congruently, lymphatic-specific podoplanin deletion led to a decrease in medullary sinus macrophages in tumor-draining LNs in vivo. In summary, our data show that tumor-derived factors induce transcriptional changes in LECs of the draining LNs, especially the fLECs, and that these changes may affect tumor immunity. We also identified a new function of podoplanin, which is expressed on all LECs, in mediating macrophage adhesion to LECs and their correct localization in LN sinuses.