oleylamide and Liver-Neoplasms

Increasing gap junction activity in tumor cells provides a target by which to enhance antineoplastic therapies. Previously, several naturally occurring agents, including all-trans retinoic acid (ATRA) have been demonstrated to increase gap junctional intercellular communication (GJIC) in a number of types of cancer cells. In the present study, we investigated in vitro whether ATRA modulates the response of human hepatocellular carcinoma (HCC) cells to sorafenib, the only proven oral drug for advanced HCC, and the underlying mechanisms. HepG2 and SMMC-7721 cells were treated with sorafenib and/or ATRA, and cell proliferation and apoptosis were analyzed; the role of GJIC was also explored. We found that ATRA, at non-toxic concentrations, enhanced sorafenib-induced growth inhibition in both HCC cell lines, and this effect was abolished by two GJIC inhibitors, 18-α-GA and oleamide. Whereas lower concentrations of sorafenib (5 µM) or ATRA (0.1 or 10 µM) alone modestly induced GJIC activity, the combination of sorafenib plus ATRA resulted in a strong enhancement of GJIC. However, the action paradigm differed in the HepG2 and SMMC-7721 cells, with the dominant effect of GJIC dependent on the cell-specific connexin increase in protein amounts and relocalization. RT-PCR assay further revealed a transcriptional modification of the key structural connexin in the two cell lines. Thus, a connexin-dependent gap junction enhancement may play a central role in ATRA plus sorafenib synergy in inhibiting HCC cell growth. Since both agents are available for human use, the combination treatment represents a future profitable strategy for the treatment of advanced HCC.

Topics: Anti-Inflammatory Agents; Antineoplastic Agents; Apoptosis; Carcinoma, Hepatocellular; Cell Communication; Cell Line, Tumor; Cell Proliferation; Connexins; Drug Synergism; Gap Junctions; Glycyrrhetinic Acid; Hep G2 Cells; Humans; Liver Neoplasms; Niacinamide; Oleic Acids; Phenylurea Compounds; Protein Kinase Inhibitors; Sorafenib; Tretinoin

Functional intact liver organoid can be reconstructed in a radial-flow bioreactor when human hepatocellular carcinoma (FLC-5), mouse immortalized sinusoidal endothelial M1 (SEC) and A7 (HSC) hepatic stellate cell lines are cocultured. The structural and functional characteristics of the reconstructed organoid closely resemble the in vivo liver situation. Previous liver organoid studies indicated that cell-to-cell communications might be an important factor for the functional and structural integrity of the reconstructed organoid, including the expression of fenestrae. Therefore, we examined the possible relationship between functional intact gap junctional intercellular communication (GJIC) and fenestrae dynamics in M1-SEC cells. The fine morphology of liver organoid was studied in the presence of (1) irsogladine maleate (IM), (2) oleamide and (3) oleamide followed by IM treatment. Fine ultrastructural changes were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and compared with control liver organoid data. TEM revealed that oleamide affected the integrity of cell-to-cell contacts predominantly in FLC-5 hepatocytes. SEM observation showed the presence of fenestrae on M1-SEC cells; however, oleamide inhibited fenestrae expression on the surface of endothelial cells. Interestingly, fenestrae reappeared when IM was added after initial oleamide exposure. GJIC mediates the number of fenestrae in endothelial cells of the liver organoid.

Topics: Animals; Carcinoma, Hepatocellular; Cells, Cultured; Coculture Techniques; Endothelium, Vascular; Gap Junctions; Humans; Liver; Liver Neoplasms; Mice; Mice, Transgenic; Oleic Acids; Organoids