Osteopontin regulates epithelial mesenchymal transition-associated growth of hepatocellular cancer in a mouse xenograft model.

Abstract

To determine the efficacy of osteopontin (OPN) targeting in hepatocellular cancer (HCC). SUMMARY/BACKGROUND: OPN is associated with HCC growth and metastasis and represents a unique therapeutic target. OPN and epithelial-mesenchymal transition (EMT) markers, α-smooth muscle actin (SMA), vimentin, and tenascin-c, were measured in archived human HCC tissues from metastatic (n = 4) and nonmetastatic (n = 4) settings. Additional studies utilized human Sk-Hep-1 (high OPN expression) and Hep3b (low OPN expression) HCC cells. An RNA aptamer (APT) that avidly binds (Kd = 18 nM; t1/2 = 7 hours) and ablates OPN binding was developed. Adhesion, migration/invasion, and EMT markers were determined with APT or a mutant control aptamer (Mu-APT). RFP-Luc-Sk-Hep-1 were implanted into NOD-scid mice livers and followed by using bioluminescence imaging. After verification of tumor growth, at week 3, APT (0.5 mg/kg; n = 4) or Mu-APT (0.5 mg/kg; n = 4) was injected q48h. When mice were killed at week 8, tumor cells were reisolated and assayed for EMT markers. OPN and EMT markers were significantly increased in the metastatic cohort. APT inhibited Sk-Hep-1 adhesion and migration/invasion by 5- and 4-fold, respectively. APT significantly decreased EMT protein markers, SMA, vimentin, and tenascin-c. In contrast, APT did not alter Hep3B adhesion, or migration/invasion. EMT markers were slightly decreased. In the in vivo model, at weeks 6 to 8, APT inhibited HCC growth by more than 10-fold. SMA, vimentin, and tenascin-c mRNAs were decreased by 60%, 40%, and 49%, respectively, in RFP-positive Sk-Hep-1 recovered by fluorescence-activated cell sorting (P < 0.04 vs Mu-APT for all). APT targeting of OPN significantly decreases EMT and tumor growth of HCC.