Hyaluronic Acid Receptor-RHAMM Mediates Renal Carcinoma Metastasis

The surface proteoglycan/glycoprotein layer (glycocalyx) on tumor cells has been associated with cellular functions that can potentially enable invasion and metastasis. In addition, aggressive renal carcinoma cells (SN12L1) with high metastatic potential have enhanced invasion rates compared to low metastatic (SN12C) cells in response to interstitial flow stimuli in vitro. Our previous studies suggest that heparan sulfate (HS) and hyaluronic acid (HA) in the glycocalyx play important roles in this flow mediated mechanotransduction and upregulation of invasive and metastatic potential. We examined HA receptor‐RHAMM protein levels in both SN12L1 and SN12C cell lines. We observed significantly higher RHAMM levels, but not CD44 levels, in flow dependent SN12L1 cells compared to SN12C cells suggesting that RHAMM may be transmitting the mechanical signal from hyaluronic acid to the cell. To examine this, we knocked down the expression of RHAMM by siRNA in SN12L1 cells. RHAMM knock‐down cells displayed suppression of flow induced migration suggesting that RHAMM receptor transmits the flow signal to the cell. SAHA (Suberoylanilide Hydroxamic Acid) is a small molecule drug (Vorinostat) that, in addition to functioning as an HDAC inhibitor, has been reported to inhibit the HS synthetic enzyme NDST1. We have previously demonstrated that NDST1 knockdown in highly metastatic SN12L1 cells blocked flow‐induced migration in vitro and reduced metastasis from the kidney by 95% in a mouse model [1] . We conducted flow induced migration assays in highly metastatic SN12L1 cells in the presence of 1.0 uM SAHA. SN12L1 cells treated with 1.0 uM SAHA displayed suppression of flow induced migration consistent with previous results showing NDST1 knockdown in highly metastatic SN12L1 cells blocked flow induced migration in vitro. We also examined the effect of flow on the glycocalyx and found that SN12L1 cells exposed to 24 hours of flow increased their HS expression by 3‐fold compared to static control. We have previously shown that flow sensed by HS is transmitted to the cell by glypican‐1 [2] . All of our data are consistent with the hypothesis that RHAMM is transmitting the mechanical signal from hyaluronic acid to the cell and HS is a flow sensor linked to glypican‐1. Support or Funding Information Funding information Grant: RO1CA204949 Targeting glycocalyx mediated mechanisms of tumor metastasis