CD51 x α5β1

Integrin α5β1 and αv cross-talk in chemotaxis, and clonogenic survival of prostate cancer cells is abrogated by a bispecific α5β1/αv antibody (BsAbα5β1/αv), which uniquely induces internalization and lysosomal degradation of target integrins. We hypothesized that the BsAbα5β1/αv inactivates pathologic mechanosignaling pathways that correlate with integrin expression from patient samples. Mechanistic studies indicate that the BsAbα5β1/αv uniquely reverses Yes-associated protein, β-catenin, and focal adhesion kinase nuclear localization compared with monospecific integrin α5β1 and αv antibody controls in basal-type androgen receptor–negative prostate cancer cells. Dual integrin αv and α5 knockdown alone phenocopied the BsAbα5β1/αv effect. Following BsAbα5β1/αv treatment, Assay for Transposase-Accessible Chromatin using sequencing studies indicated the chromatin accessibility to TEAD and AP-1 family members was markedly reduced. In vitro and in vivo RNA sequencing indicated downregulation of Myc/E2F, TGF-β, and epithelial–mesenchymal transition and upregulation of type I and II IFN transcriptomic pathways. The BsAbα5β1/αv induced CXCL10 and CCL5 cytokine secretion, immune-infiltration of tumors, and NK cell–mediated elimination of the basal-type prostate cancer xenografts in nude mice. αv integrin was highly expressed and principally correlated with the Myc signaling pathway in rapid autopsy tissue microarrays, consistent with correlative data from the SU2C metastatic castration-resistant prostate cancer and Deutsches Krebsforschungszentrum early-onset prostate cancer cohorts. These studies connect integrin signaling with the central biology of basal-type and castration-resistant prostate cancers and define a novel therapeutic strategy that controls critical immunosuppressive pathways.

Dual integrin α5β1/αv targeting with a bispecific antibody represents a novel therapeutic strategy that reprograms the epigenetic and transcriptomic signatures of basal-type prostate cancer with induction of immunologic tumor control.

Integrins play a central role in myofibroblast pathological adhesion, over-contraction, and TGFβ activation. Previously, we demonstrated that after corneal wounding, αv integrins are protected from intracellular degradation by upregulation of the deubiquitinase USP10, leading to cell-surface integrin accumulation. Because integrins bind to and internalize extracellular matrix (ECM), we tested whether extracellular fibronectin (FN) accumulation can result from an increase in integrin and matrix recycling in primary human corneal fibroblasts (HCFs).

Primary HCFs were isolated from cadaver eyes. HCFs were transfected with either USP10 cDNA or control cDNA by nucleofection. Internalized FN was quantified with a FN ELISA. Recycled extracellular integrin and FN were detected with streptavidin-488 by live cell confocal microscopy (Zeiss LSM 780). Endogenous FN extra domain A was detected by immunocytochemistry. Cell size and removal of FN from the cell surface was determined by flow cytometry.

USP10 overexpression increased α5β1 (1.9-fold; P < 0.001) and αv (1.7-fold; P < 0.05) integrin recycling, with a concomitant increase in biotinylated FN internalization (2.1-fold; P < 0.05) and recycling over 4 days (1.7-2.2-fold; P < 0.05). The dependence of FN recycling on integrins was demonstrated by α5β1 and αv integrin blocking antibodies, which, compared with control IgG, decreased biotinylated FN recycling (62% and 84%, respectively; P < 0.05). Overall, we established that extracellular FN was composed of approximately 1/3 recycled biotinylated FN and 2/3 endogenously secreted FN.

Our data suggest that reduced integrin degradation with a subsequent increase in integrin/FN recycling after wounding may be a newly identified mechanism for the characteristic accumulation of ECM in corneal scar tissue.

Cyclic RGD peptides are well‐known ligands of integrins. The integrins αVβ3 and α5β1 are involved in angiogenesis, and integrin αVβ3 is abundantly present on cancer cells, thus representing a therapeutic target. Hence, synthetic and biophysical studies continuously are being directed towards the understanding of ligand‐integrin interaction. In this context, the development of versatile synthetic strategies to obtain fluorescent building blocks that can add molecular diversity and modular spectral characteristics while not compromising binding affinity or selectivity is a relevant task. An on‐resin intramolecular Suzuki–Miyaura cross‐coupling (SMC) between l‐ or d‐7‐bromotryptophan (7BrTrp) and a phenothiazine (Ptz) boronic acid affords fluorescent cyclic RGD pseudopeptides, c(RGD(W/w)Ptz). Ring closure by SMC establishes a phenothiazine–indole moiety with axial chirality. An array of eight novel compounds has been synthesized, among them one fluorescent compound with good affinity to integrin αVβ3. The fluorescence properties of the analogues can be efficiently tuned depending on the substituents in Ptz moiety even for fluorescence emission in the visible (red) spectral range.