Abstract
Previous studies have shown that intensive macropinocytosis occurs in cancer cells and neutral red (NR) is noted for its capability to enter into the cell massively through a process mimetic to macropinocytosis. In addition, trans-cinnamic acid (tCA) has been found to be an inhibitor of histone deacetylase (HDAC). In the present study, cinnamoylphenazine (CA-PZ) that consists of NR and tCA moieties was synthesized and evaluated. As shown, CA-PZ massively entered into colon carcinoma HT-29 cells and pancreatic carcinoma MIA PaCa-2 cells and this entry was blocked by 5-(N-ethyl-N-isopropyl) amiloride (EIPA, an inhibitor of macropinocytosis), indicating a macropinocytosis-mediated uptake. Furthermore, CA-PZ markedly increased the protein expression levels of acetyl-H3, acetyl-H4 and p21 in HT-29 cells and MIA PaCa-2 cells. CA-PZ significantly inhibited the growth of colon carcinoma HT-29 and pancreatic carcinoma MIA PaCa-2 xenografts. By in vivo imaging, CA-PZ displayed prominent accumulation in the tumor xenografts. The study indicates that the newly synthesized CA-PZ acts as an HDAC inhibitor in association with intensive macropinocytosis-mediated intracellular delivery in cancer cells. The use of neutral red for preparation of chimeric molecules with the attribute of macropinocytosis-mediated intracellular delivery might open an alternative way for development of HDAC inhibitors.