Molecular determinants of the response of cancer cells towards geldanamycin and its derivatives.

Geldanamycin is an ansamycin-derivative of a benzoquinone isolated from Streptomyces hygroscopicus. It inhibits tyrosine kinases and heat shock protein 90 (HSP90). Geldanamycin and 11 derivatives were subjected to molecular docking to HSP90, and 17-desmethoxy-17-N,N-dimethylamino-geldanamycin (17-DMAG) was the compound with the highest binding affinity (-7.73 ± 0.12 kcal/mol) and the lowest inhibition constant (2.16 ± 0.49 µM). Therefore, 17-DMAG was selected for further experiments in comparison to geldanamycin. Multidrug resistance (MDR) represents a major problem for successful cancer therapy. We tested geldanamycin and 17-DMAG against various drug-resistant cancer cell lines. Although geldanamycin and 17-DMAG inhibited the proliferation in all cell lines tested, multidrug-resistant P-glycoprotein-overexpressing CEM/ADR5000 cells were cross-resistant, ΔEGFR-overexpressing tumor cells and p53 knockout cells were sensitive to these two compounds. COMPARE and hierarchical cluster analyses were performed, and 60 genes were identified to predict the sensitivity or resistance of 59 NCI tumor cell lines towards geldanamycin and 17-DMAG. The distribution of cell lines according to their mRNA expression profiles indicated sensitivity or resistance to both compounds with statistical significance. Moreover, bioinformatic tools were used to study possible mechanisms of action of geldanamycin and 17-DMAG. Galaxy Cistrome analyses were carried out to predict transcription factor binding motifs in the promoter regions of the candidate genes. Interestingly, the NF-ĸB DNA binding motif (Rel) was identified as the top transcription factor. Furthermore, these 60 genes were subjected to Ingenuity Pathway Analysis (IPA) to study the signaling pathway interactions of these genes. Interestingly, IPA also revealed the NF-ĸB pathway as the top network among these genes. Finally, NF-ĸB reporter assays confirmed the bioinformatic prediction, and both geldanamycin and 17-DMAG significantly inhibited NF-κB activity after exposure for 24 h. In conclusion, geldanamycin and 17-DMAG exhibited cytotoxic activity against different tumor cell lines. Their activity was not restricted to HSP90 but indicated an involvement of the NF-KB pathway.

In Vitro and In Silico Studies of Two 1,4-Naphthoquinones and Their Topical Formulation in Bigels.

BACKGROUND: 1,4-Naphthoquinones (1,4-NQs) are secondary plant metabolites with numerous biological activities. 1,4-NQs display low water solubility and poor bioavailability. Bigels are a new technology with great potential, which are designated as drug delivery systems. Biphasic bigels consisting of solid and liquid components represent suitable formulations improving diffusion and bioavailability of NQs into the skin. OBJECTIVE: We evaluated the in silico and in vitro activity of 5,8-dihydroxy-1,4-naphthoquinone (M1) and 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (M2) on elastase and assessed their cytotoxicity towards COLO38 melanoma cells. The 1,4-NQs were loaded into bigels for topical application. METHODS: Molecular docking was performed, and cytotoxicity was evaluated on COLO38 cells using the resazurin assay. M1 and M2 were separately incorporated into bigels consisting of hydrogel organogel with sweet almond oil as the non-polar solvent and span 65 as an organogelator. Their rheological behavior and microscopic properties were characterized. The diffusion kinetics and permeation of 1,4-NQs from bigels were studied by a paddle-over-extraction cell and a "Franz cell" in vitro permeation model. RESULTS: Molecular docking data predicted high interactions between elastase and ligands. Hydrogen bonds with LYS233 were observed for M1, M2, and phosphoramidon (positive control). The average binding energies were -8.5 and -9.7 kcal/mol for M1 and M2 and -12.6 kcal/mol for phosphoramidon. M1 and M2 inhibited the elastase activity by 58.9 and 56.6%, respectively. M1 and M2 were cytotoxic towards COLO38 cells (IC50 value: 2.6 and 9.8 µM). The M1 release from bigels was faster and more efficient than that of M2. CONCLUSION: M1 and M2 are promising for skin disease treatment. Biphasic organogel-hydrogel bigels are efficient and safe formulations to overcome their low bioavailability.