Exosomal αvβ6 integrin is required for monocyte M2 polarization in prostate cancer

Therapeutic approaches aimed at curing prostate cancer are only partially successful given the occurrence of highly metastatic resistant phenotypes that frequently develop in response to therapies. Recently, we have described αvβ6, a surface receptor of the integrin family as a novel therapeutic target for prostate cancer; this epithelial-specific molecule is an ideal target since, unlike other integrins, it is found in different types of cancer but not in normal tissues. We describe a novel αvβ6-mediated signaling pathway that has profound effects on the microenvironment. We show that αvβ6 is transferred from cancer cells to monocytes, including β6-null monocytes, by exosomes and that monocytes from prostate cancer patients, but not from healthy volunteers, express αvβ6. Cancer cell exosomes, purified via density gradients, promote M2 polarization, whereas αvβ6 down-regulation in exosomes inhibits M2 polarization in recipient monocytes. Also, as evaluated by our proteomic analysis, αvβ6 down-regulation causes a significant increase in donor cancer cells, and their exosomes, of two molecules that have a tumor suppressive role, STAT1 and MX1/2. Finally, using the Ptenpc−/− prostate cancer mouse model, which carries a prostate epithelial-specific Pten deletion, we demonstrate that αvβ6 inhibition in vivo causes up-regulation of STAT1 in cancer cells. Our results provide evidence of a novel mechanism that regulates M2 polarization and prostate cancer progression through transfer of αvβ6 from cancer cells to monocytes through exosomes

Small extracellular vesicle-mediated ITGB6 siRNA delivery downregulates the αVβ6 integrin and inhibits adhesion and migration of recipient prostate cancer cells

The αVβ6 integrin, an epithelial-specific cell surface receptor absent in normal prostate and expressed during prostate cancer (PrCa) progression, is a therapeutic target in many cancers. Here, we report that transcript levels of ITGB6 (encoding the β6 integrin subunit) are significantly increased in metastatic castrate-resistant androgen receptor-negative prostate tumors compared to androgen receptor-positive prostate tumors. In addition, the αVβ6 integrin protein levels are significantly elevated in androgen receptor-negative PrCa patient derived xenografts (PDXs) compared to androgen receptor-positive PDXs. In vitro, the androgen receptor-negative PrCa cells express high levels of the αVβ6 integrin compared to androgen receptor-positive PrCa cells. Additionally, expression of androgen receptor (wild type or variant 7) in androgen receptor-negative PrCa cells downregulates the expression of the β6 but not αV subunit compared to control cells. We demonstrate an efficient strategy to therapeutically target the αVβ6 integrin during PrCa progression by using short interfering RNA (siRNA) loaded into PrCa cell-derived small extracellular vesicles (sEVs). We first demonstrate that fluorescently-labeled siRNAs can be efficiently loaded into PrCa cell-derived sEVs by electroporation. By confocal microscopy, we show efficient internalization of these siRNA-loaded sEVs into PrCa cells. We show that sEV-mediated delivery of ITGB6-targeting siRNAs into PC3 cells specifically downregulates expression of the β6 subunit. Furthermore, treatment with sEVs encapsulating ITGB6 siRNA significantly reduces cell adhesion and migration of PrCa cells on an αVβ6-specific substrate, LAP-TGFβ1. Our results demonstrate an approach for specific targeting of the αVβ6 integrin in PrCa cells using sEVs encapsulating ITGB6-specific siRNAs

Small extracellular vesicles modulated by αVβ3 integrin induce neuroendocrine differentiation in recipient cancer cells

The ability of small extracellular vesicles (sEVs) to reprogram cancer cells is well established. However, the specific sEV components able to mediate aberrant effects in cancer cells have not been characterized. Integrins are major players in mediating sEV functions. We have previously reported that the αVβ3 integrin is detected in sEVs of prostate cancer (PαVβ3rCa) cells and transferred into recipient cells. Here, we investigate whether sEVs from -expressing cells affect tumour growth differently than sEVs from control cells that do not express αVβ3. We compared the ability of sEVs to stimulate tumour growth, using sEVs isolated from PrCa C4-2B cells by iodixanol density gradient and characterized with immunoblotting, nanoparticle tracking analysis, immunocapturing and single vesicle analysis. We incubated PrCa cells with sEVs and injected them subcutaneously into nude mice to measure in vivo tumour growth or analysed in vitro their anchorage-independent growth. Our results demonstrate that a single treatment with sEVs shed from C4-2B cells that express αVβ3, but not from control cells, stimulates tumour growth and induces differentiation of PrCa cells towards a neuroendocrine phenotype, as quantified by increased levels of neuroendocrine markers. In conclusion, the expression of αVβ3 integrin generates sEVs capable of reprogramming cells towards an aggressive phenotype

Differential expression of αVβ3 and αVβ6 integrins in prostate cancer progression

Neuroendocrine prostate cancer (NEPrCa) arises de novo or after accumulation of genomic alterations in pre-existing adenocarcinoma tumors in response to androgen deprivation therapies. We have provided evidence that small extracellular vesicles released by PrCa cells and containing the αVβ3 integrin promote neuroendocrine differentiation of PrCa in vivo and in vitro. Here, we examined αVβ3 integrin expression in three murine models carrying a deletion of PTEN (SKO), PTEN and RB1 (DKO), or PTEN, RB1 and TRP53 (TKO) genes in the prostatic epithelium; of these three models, the DKO and TKO tumors develop NEPrCa with a gene signature comparable to those of human NEPrCa. Immunostaining analysis of SKO, DKO and TKO tumors shows that αVβ3 integrin expression is increased in DKO and TKO primary tumors and metastatic lesions, but absent in SKO primary tumors. On the other hand, SKO tumors show higher levels of a different αV integrin, αVβ6, as compared to DKO and TKO tumors. These results are confirmed by RNA-sequencing analysis. Moreover, TRAMP mice, which carry NEPrCa and adenocarcinoma of the prostate, also have increased levels of αVβ3 in their NEPrCa primary tumors. In contrast, the αVβ6 integrin is only detectable in the adenocarcinoma areas. Finally, analysis of 42 LuCaP patient-derived xenografts and primary adenocarcinoma samples shows a positive correlation between αVβ3, but not αVβ6, and the neuronal marker synaptophysin; it also demonstrates that αVβ3 is absent in prostatic adenocarcinomas. In summary, we demonstrate that αVβ3 integrin is upregulated in NEPrCa primary and metastatic lesions; in contrast, the αVβ6 integrin is confined to adenocarcinoma of the prostate. Our findings suggest that the αVβ3 integrin, but not αVβ6, may promote a shift in lineage plasticity towards a NE phenotype and might serve as an informative biomarker for the early detection of NE differentiation in prostate cancer

Irradiation of Prostate Cancer Alters Circulating Small Extracellular Vesicle Functions

It is known that β1 integrins and a downstream signaling molecule c-Src are upregulated in prostate cancer (PrCa) tissues, are co-expressed in circulating small extracellular vesicles (sEVs) and contribute to cancer progression. Here, we demonstrate that sEVs from PrCa patients show robust expression of both β1 integrins and c-Src. The impact of irradiation, a widely used therapy for the treatment of PrCa, on circulating sEVs is however not fully understood. We show that sEVs isolated from the plasma of transgenic adenocarcinoma of mouse prostate (TRAMP) mice, stimulate migration and anchorage-independent growth of recipient cancer cells, but sEVs are not active when isolated from mice that had undergone pelvic irradiation of PrCa. In addition, circulating sEVs from irradiated mice do not show co-sedimentation of β1 integrins and either c-Src or sEV markers, previously observed in sEVs from non-irradiated mice, but show reduced expression of c-Src. To rule out that the observed effect of irradiation on sEVs is not due to reduced tumor size, we demonstrate that irradiation of PrCa cells in vitro diminishes sEV capability to stimulate recipient cell anchorage-independent growth. Irradiation-induced changes in the composition of circulating sEVs illustrate a tumor-suppressive effect of radiation, which may have potential therapeutic implications

The αvβ6 integrin in cancer cell-derived small extracellular vesicles enhances angiogenesis.

Prostate cancer (PrCa) cells crosstalk with the tumour microenvironment by releasing small extracellular vesicles (sEVs). sEVs, as well as large extracellular vesicles (LEVs), isolated via iodixanol density gradients from PrCa cell culture media, express the epithelial-specific αvβ6 integrin, which is known to be induced in cancer. In this study, we show sEV-mediated protein transfer of αvβ6 integrin to microvascular endothelial cells (human microvascular endothelial cells 1 - HMEC1) and demonstrate tha

Myc-mediated transcriptional regulation of the mitochondrial chaperone TRAP1 controls primary and metastatic tumor growth.

The role of mitochondria in cancer continues to be debated, and whether exploitation of mitochondrial functions is a general hallmark of malignancy or a tumor- or context-specific response is still unknown. Using a variety of cancer cell lines and several technical approaches, including siRNA-mediated gene silencing, ChIP assays, global metabolomics and focused metabolite analyses, bioenergetics, and cell viability assays, we show that two oncogenic Myc proteins, c-Myc and N-Myc, transcriptionally control the expression of the mitochondrial chaperone TNFR-associated protein- 1 (TRAP1) in cancer. In turn, this Myc-mediated regulation preserved the folding and function of mitochondrial oxidative phosphorylation (OXPHOS) complex II and IV subunits, dampened reactive oxygen species production, and enabled oxidative bioenergetics in tumor cells. Of note, we found that genetic or pharmacological targeting of this pathway shuts off tumor cell motility and invasion, kills Myc-expressing cells in a TRAP1-dependent manner, and suppresses primary and metastatic tumor growth in vivo. We conclude that exploitation of mitochondrial functions is a general trait of tumorigenesis and that this reliance of cancer cells on mitochondrialOXPHOSpathways could offer an actionable therapeutic target in the clinic

The NOGO Receptor NgR2, A Novel αVβ3 Integrin Effector, Induces Neuroendocrine Differentiation in Prostate Cancer

Androgen deprivation therapies aimed to target prostate cancer (PrCa) are only partially successful given the occurrence of neuroendocrine PrCa (NEPrCa), a highly aggressive and highly metastatic form of PrCa, for which there is no effective therapeutic approach. Our group has demonstrated that while absent in prostate adenocarcinoma, the αVβ3 integrin expression is increased during PrCa progression toward NEPrCa. Here, we show a novel pathway activated by αVβ3 that promotes NE differentiation (NED). This novel pathway requires the expression of a GPI-linked surface molecule, NgR2, also known as Nogo-66 receptor homolog 1. We show here that NgR2 is upregulated by αVβ3, to which it associates; we also show that it promotes NED and anchorage-independent growth, as well as a motile phenotype of PrCa cells. Given our observations that high levels of αVβ3 and, as shown here, of NgR2 are detected in human and mouse NEPrCa, our findings appear to be highly relevant to this aggressive and metastatic subtype of PrCa. This study is novel because NgR2 role has only minimally been investigated in cancer and has instead predominantly been analyzed in neurons. These data thus pave new avenues toward a comprehensive mechanistic understanding of integrin-directed signaling during PrCa progression toward a NE phenotype

Characterizing Bone Tunnel Placement in Medial Ulnar Collateral Ligament Reconstruction Using Patient-Specific 3-Dimensional Computed Tomography Modeling

Background:Medial ulnar collateral ligament (MUCL) reconstruction is successful in restoring valgus elbow stability, but variability in bone tunnel characteristics exists among surgical techniques.Hypothesis:Tunnel parameters such as diameter, drill angle, and starting location in MUCL reconstruction affect tunnel length and bone bridge size between tunnels.Study Design:Descriptive laboratory study.Methods:Three-dimensional models were created from elbow computed tomography scans of 10 throwing athletes and analyzed using Mimics (Materialise) software. The MUCL reconstructions were simulated on each elbow with 3 techniques: Jobe, humeral docking, and DANE TJ. Humeral central tunnels were modified by diameter, medial-lateral epicondylar starting point, and angle with respect to the humeral axis. Ulnar tunnels were varied by diameter and angle with respect to the ulnar axis. Humeral tunnel length, humeral and ulnar bone bridge sizes, and ulnar tunnel aperture and distance from the articular surface of the olecranon were measured. Comparisons were made using 1- and 2-way analysis of variance and Student-Newman-Keuls multiple comparison tests.Results:Mean central humeral tunnel length varied significantly by starting point and angulation of the tunnel both in sagittal and coronal planes, ranging from 14.2 ± 2.3 mm to 25.5 ± 4.3 mm ( P &lt; .05). Mean bone bridge size between humeral exit tunnels ranged from 9.0 ± 2.5 mm to 15.1 ± 3.1 mm, varying by central humeral tunnel orientation and exit tunnel diameter ( P &lt; .05). Bone bridge size between ulnar tunnels with the Jobe and docking techniques averaged 6.7 ± 0.9 mm (3.2-mm tunnels) and 6.4 ± 0.8 mm (3.5-mm tunnels), respectively. Angle of ulnar tunnels affected distance from the articular surface with the Jobe and docking techniques ( P &lt; .0001) and affected tunnel aperture size with the interference screw technique ( P &lt; .0001).Conclusion:Humeral and ulnar tunnel angles, starting points, and diameters affect tunnel length, distance from the articular surface, and bone bridge size in MUCL reconstructions. Maximal humeral tunnel length is achieved by starting central or lateral to the midpoint of the epicondyle, angulated 30° to the humeral axis in the sagittal plane and 15° in the coronal plane. A reasonable goal tunnel depth should range from 15 to 20 mm. Ulnar tunnels should be placed on the anterior and posterior aspects of the sublime tubercle, directed away from the joint to minimize the likelihood of breaching the articular cartilage. A bone bridge of 6 to 8 mm between these tunnels can be reasonably achieved. Tunnels with the ulnar interference screw fixation technique should also be directed away from the joint but at an angle more perpendicular than 45° to minimize tunnel aperture size. Regardless of angle of the tunnel drilled for the ulnar interference screw employed in the DANE TJ technique, the tunnel length is sufficient to fully contain a 15-mm screw.Clinical Relevance:Computer models can guide MUCL reconstruction technique by indicating tunnel placement for maximizing the bone bridge and tunnel length.</jats:sec