The Ellipticine Derivative NSC 338258 Has Anti-Myeloma Activity.

We recently discovered that amplification and overexpression of the CKS1B gene, which regulates the ubiquitination and proteasomal degradation of the cyclin-dependent kinase inhibitor p27^Kip1, is linked to a poor prognosis in myeloma. We used the COMPARE algorithm (NCI, Developmental Therapeutics Program) to identify correlations between the expression of CKS1B in the NCI 60 cell line panel and the GI50 of nearly 50,000 anticancer compounds. This analysis revealed a strong correlation between CKS1B expression and the anticancer activity of Ellipticine and multiple derivatives of it. Ellipticine (5,11-Dimethyl-6H-Pyrido[4,3]Carbazole, MW=246.3), an alkaloid isolated from Apocyanaceae, is a topoisomerase II poison that induces topoisomerase II-dependent DNA cleavages. Previous studies have shown that the anti-neoplastic mechanism of Ellipticine is to form covalent DNA adducts mediated by human cytochromes P450. We obtained Ellipticine and twelve other CKS1B-correlated antineoplastic compounds from the NCI-DTP. In vitro analyses were carried out with 12 myeloma cell lines. Cell viability was detected using CellTiter-Glo Luminescent Assay (Promega, Co.). We found that one of the Ellipticine derivatives, NSC 338258 (EPED3) showed significant cell kill activity not observed with Ellipticine or the other compounds in all cell lines tested. In a dose response analysis of cell kill using 0.2, 0.02, and 0.002 uM EPED3, 12 out of 12 myeloma cell lines showed at least 50% reduction in cell viability within 24 hrs at 0.2 uM compared to no treatment controls. By 48 hours essentially all cell growth was inhibited. Only weak to moderate cell kill was noted at 0.02 and 0.002 uM at all time points tested. We next tested the activity of the topoisomerase II inhibitor VP-16-213 at the same concentrations and time periods and found only modest reduction of cell viability at day 5 at 0.2uM. Essentially no effect on cell viability was observed at 0.02 and 0.002 uM at any of the time points tested. We next tested whether EPED3 had a comparable anti-myeloma activity as Adriamycin at the same concentrations. Twelve myeloma cell lines were exposed to EPED3, VP-16-213, and Adriamycin at 0.2mM for a total of 5 days. Results of the mean relative luminescence showed that EPED3 promoted an immediate cell proliferation arrest within the first 24 hours of culture, with almost complete cell kill within 3 days. The other drugs were less effective with Adriamycin inducing a > 90% reduction only after 4 days and VP-16 a > 70% reduction at day 5. These data suggests that EPED3 may represent a potential new therapeutic for myeloma. Studies are currently underway to test the efficacy of EPED3 in our in-vivo SCID-Hu mouse model of primary myeloma and results of these studies will be presented.