The cancer glycocalyx mediates intravascular adhesion and extravasation during metastatic dissemination

Abstract

The glycocalyx on tumor cells has been recently identified as an important driver for cancer progression, possibly providing critical opportunities for treatment. Metastasis, in particular, is often the limiting step in the survival to cancer, yet our understanding of how tumor cells escape the vascular system to initiate metastatic sites remains limited. Using an in vitro model of the human microvasculature, we assess here the importance of the tumor and vascular glycocalyces during tumor cell extravasation. Through selective manipulation of individual components of the glycocalyx, we reveal a mechanism whereby tumor cells prepare an adhesive vascular niche by depositing components of the glycocalyx along the endothelium. Accumulated hyaluronic acid shed by tumor cells subsequently mediates adhesion to the endothelium via the glycoprotein CD44. Trans-endothelial migration and invasion into the stroma occurs through binding of the isoform CD44v to components of the sub-endothelial extra-cellular matrix. Targeting of the hyaluronic acid-CD44 glycocalyx complex results in significant reduction in the extravasation of tumor cells. These studies provide evidence of tumor cells repurposing the glycocalyx to promote adhesive interactions leading to cancer progression. Such glycocalyx-mediated mechanisms may be therapeutically targeted to hinder metastasis and improve patient survival.

Personalized models of breast cancer desmoplasia reveal biomechanical determinants of drug penetration

“…At the same time, direct targeting of HA through CD44 can achieve greater normalizing responses for other patients, as seen in our results for models of advanced, aggressive breast cancer (MDA-MB-468 TC line and primary basal TCs). This observation is consistent with the identification of HA and CD44 as markers of metastatic breast cancer 54,56 , and that their inhibition can prevent vascular colonization by TCs 47 . Importantly, our results show that the vascularized tumoroid models can capture these variations in desmoplastic ECM deposition and resulting impaired MVN perfusion, allowing the assessment of different therapeutic strategies to improve drug penetration.…”

“…At the same time, direct targeting of HA through CD44 can achieve greater normalizing responses for other patients, as seen in our results for models of advanced, aggressive breast cancer (MDA-MB-468 TC line and primary basal TCs). This observation is consistent with the identification of HA and CD44 as markers of metastatic breast cancer 54,56 , and that their inhibition can prevent vascular colonization by TCs 47 .…”

“…Additionally, the lack of mechanical cues from flow in poorly perfusable tumoroid MVNs may decrease glycocalyx expression 45 . While we observed increased HAS2 expression for MVNs subjected to physiological vascular flow for 48 hours (Figure 2f) and increased vascular HA concentration (Supplementary Figure 6e), consistent with a decreased MVN permeability to dextran (4.1 × 10 −9 cm s −1 compared to 1.1 × 10 −8 cm s −1 in static conditions, Supplementary Figure 6d), we have previously observed functional vascular glycocalyx expression even under static MVN culture conditions 46,47 , as confirmed here by measurable expression levels for HAS2. In addition, no change in permeability or vascular HA was observed in the vicinity of the tumoroids irrespective of flow (Supplementary Figure 6d, e).…”

“…Because the three TC line tumoroids show different expression and localization of HA, we next assessed how the treatments can affect stromal HA concentrations in the different tumoroids. We found increased protein expression of CD44v, the CD44 isoform associated with TC invasion 47,54 , in the SKBR3 and, more pronouncedly, MDA-MB-468 tumoroids (as opposed to the more benign isoform CD44s, which does not change from controls MVNs), and TGFβ in all three tumoroids, though highest in MCF7 (Figure 4d). Likely as a result of the different target concentrations, the treatments affected the tumoroids differently: All three treatments successfully and severely decreased stromal HA concentrations in the tumoroids, although the effect was greater by blocking TGFβ in the MCF7 and SKBR3 tumoroids and by blocking CD44 in the MDA-MB-468 tumoroids (Figure 4e).…”

“…Notably, using our models we have shown that HA exists in two forms in the desmoplastic microenvironment: vascular HA and stromal HA, both of which constitute biomechanical barriers to drug penetration. Vascular HA degradation in the tumoroid microenvironment may not only impair vascular barrier function, but also favor TC vascular migration and metastatic colonization 47 . Stromal HA degradation, instead, can prove beneficial to treatment by improving interstitial transport of therapeutic molecules to TCs.…”