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 & PLUSMN; 0.12 kcal/mol) and the lowest inhibition constant (2.16 & PLUSMN; 0.49 & mu;M). 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, & UDelta;EGFR-overexpressing tumor cells and p53 knockout cells were sensitive to these two com-pounds. 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 gel-danamycin 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-& kappa;B 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-& kappa;B pathway as the top network among these genes. Finally, NF-& kappa;B reporter assays confirmed the bioinformatic prediction, and both geldanamycin and 17-DMAG significantly inhibited NF-& kappa;B 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.

Automated summary

Geldanamycin is a benzoquinone-derived ansamycin that inhibits tyrosine kinases and heat shock protein 90 (HSP90). Among its derivatives, 17-desmethoxy-17-N,N-dimethylamino-geldanamycin (17-DMAG) has the highest binding affinity and lowest inhibition constant to HSP90. Both geldanamycin and 17-DMAG show cytotoxic activity against different tumor cell lines, with resistance observed in multidrug-resistant cells and sensitivity in certain tumor cells. Bioinformatic analysis suggests the involvement of the NF-KB pathway in their mechanism of action, which was confirmed by NF-KB reporter assays.