n-caproylsphingosine and Colorectal-Neoplasms

Colorectal cancer (CRC) is highly metastatic, significantly so to liver, a characteristic that embodies one of the most challenging aspects of treatment. The integrin family of cell-cell and cell-matrix adhesion receptors plays a central role in migration and invasion, functions that underlie metastatic potential. In the present work we sought to determine the impact of ceramide, which plays a key modulatory role in cancer suppression, on integrin cell surface expression and function in CRC cells in order to reveal possible ceramide-centric effects on tumor cell motility. Human CRC cells LoVo, HT-29, and HCT-116 were employed, which represent lines established from primary and metastatic sites. A cell-permeable, short-chain analog, C6-ceramide, was used as ceramide mimic. Exposure of cells to C6-ceramide (24 h) promoted a dose-dependent (2.5-10 µM) decrease in the expression of cell surface β1 and β4 integrin subunits in all cell lines; at 10 µM C6-ceramide, the decreases ranged from 30 to 50% of the control. Expression of cell surface αVβ6 integrin, which is associated with advanced invasion in CRC, was also suppressed by C6-ceramide. Decreases in integrin expression translated to diminished cellular adhesion, 50% of the control at 5 µM C6-ceramide, and markedly reduced cellular migration, approximately 30-40% of the control in all cell lines. Physicochemical examination revealed potent efficacy of nano-formulated C6-ceramide, but inferior activity of dihydro-C6-ceramide and L-C6-ceramide, compared to the unsaturated counterpart and the natural d-enantiomer, respectively. These studies demonstrate novel actions of ceramides that may have application in suppression of tumor metastasis, in addition to their known tumor suppressor effects.

Topics: Antigens, Neoplasm; Antineoplastic Agents; Cell Adhesion; Cell Movement; Cell Survival; Ceramides; Colorectal Neoplasms; Dose-Response Relationship, Drug; Down-Regulation; Drug Compounding; HCT116 Cells; HT29 Cells; Humans; Integrin beta1; Integrin beta4; Integrins; Molecular Structure; Neoplasm Metastasis; Signal Transduction; Time Factors

Autophagy, a catabolic survival pathway, is gaining attention as a potential target in cancer. In human liver and colon cancer cells, treatment with an autophagy inducer, nanoliposomal C6-ceramide, in combination with the autophagy maturation inhibitor, vinblastine, synergistically enhanced apoptotic cell death. Combination treatment resulted in a marked increase in autophagic vacuole accumulation and decreased autophagy maturation, without diminution of the autophagy flux protein P62. In a colon cancer xenograft model, a single intravenous injection of the drug combination significantly decreased tumor growth in comparison to the individual treatments. Most importantly, the combination treatment did not result in increased toxicity as assessed by body weight loss. The mechanism of combination treatment-induced cell death both in vitro and in vivo appeared to be apoptosis. Supportive of autophagy flux blockade as the underlying synergy mechanism, treatment with other autophagy maturation inhibitors, but not autophagy initiation inhibitors, were similarly synergistic with C6-ceramide. Additionally, knockout of the autophagy protein Beclin-1 suppressed combination treatment-induced apoptosis in vitro. In conclusion, in vitro and in vivo data support a synergistic antitumor activity of the nanoliposomal C6-ceramide and vinblastine combination, potentially mediated by an autophagy mechanism.

Topics: Adaptor Proteins, Signal Transducing; Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Apoptosis Regulatory Proteins; Autophagy; Beclin-1; Carcinoma, Hepatocellular; Caspase 3; Caspase 7; Cell Survival; Ceramides; Colorectal Neoplasms; Dose-Response Relationship, Drug; Drug Synergism; Hep G2 Cells; Humans; Injections, Intravenous; Liposomes; Liver Neoplasms; Membrane Proteins; Mice; Mice, Nude; Nanoparticles; RNA Interference; Sequestosome-1 Protein; Transfection; Tumor Burden; Vinblastine; Xenograft Model Antitumor Assays