Levels of active tyrosine kinase receptor determine the tumor response to Zalypsis

[Background] Zalypsis® is a marine compound in phase II clinical trials for multiple myeloma, cervical and endometrial cancer, and Ewing’s sarcoma. However, the determinants of the response to Zalypsis are not well known. The identification of biomarkers for Zalypsis activity would also contribute to broaden the spectrum of tumors by selecting those patients more likely to respond to this therapy.[Methods] Using in vitro drug sensitivity data coupled with a set of molecular data from a panel of sarcoma cell lines, we developed molecular signatures that predict sensitivity to Zalypsis. We verified these results in culture and in vivo xenograft studies.[Results] Zalypsis resistance was dependent on the expression levels of PDGFRα or constitutive phosphorylation of c-Kit, indicating that the activation of tyrosine kinase receptors (TKRs) may determine resistance to Zalypsis. To validate our observation, we measured the levels of total and active (phosphorylated) forms of the RTKs PDGFRα/β, c-Kit, and EGFR in a new panel of diverse solid tumor cell lines and found that the IC50 to the drug correlated with RTK activation in this new panel. We further tested our predictions about Zalypsis determinants for response in vivo in xenograft models. All cells lines expressing low levels of RTK signaling were sensitive to Zalypsis in vivo, whereas all cell lines except two with high levels of RTK signaling were resistant to the drug.[Conclusions] RTK activation might provide important signals to overcome the cytotoxicity of Zalypsis and should be taken into consideration in current and future clinical trials.The AC lab was supported by grants to from the Spanish Ministry of Economy and Competitivity, ISCIII (Fis: PI12/00137, RTICC: RD12/0036/0028), Consejeria de Ciencia e Innovacion (CTS-6844), and Consejeria de Salud of the Junta de Andalucia (PI-0135-2010 and PI-0306-2012). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer Reviewe

Levels of p27kip1 determine Aplidin sensitivity.

Aplidin (plitidepsin) is a novel anticancer drug isolated from themarine tunicate Aplidiumalbicans. Aplidin shows potent antitumor activity in preclinical models against awide variety of human tumors. Aplidin is currently inphase II clinical trials in a varietyof solid tumorsandhematologicmalignancies.Moreover,clinical studiesofAplidin incombinationwithother agentsare ongoingbecause itgenerally lackscross-resistancewith other known cytotoxic drugs. Themode of action of Aplidinintumorcellsisonlypartiallyunderstood.Aplidin inducesanearlyoxidativestressresponse,whichresults inarapidandsustainedactivationoftheepidermalgrowth factor receptor, thenonreceptor protein tyrosinekinase Src,andtheserinethreoninekinasesc-JunNH2-terminal kinaseandp38mitogen-activatedproteinkinase.Here, weshowthat sensitivity toAplidincorrelates inversely with the levels of expression of the cyclin-dependent kinase inhibitorp27kip1 (p27) inapanelof lowpassaged humansarcomacell lines.Aplidin inducesp27 through anoxidation-dependentmechanismandthereductionof p27levelsbyspecificshorthairpinRNAincreasesAplidin sensitivity.Weconfirmedtheseresultsinp27nullmouse embryonicfibroblastscorroboratingthespecificityof the p27roleinAplidinresponsebecausep21waf1nullmouse embryonic fibroblastsdonot showthis increasedsensitivity.We propose amechanismof action of Aplidin involving p27 and support the analysis of p27 in the responsetoAplidin incurrentlyongoingclinical trials to establishthe levelsof thisproteinasresponsepredictor.pre-print1,83 M

Chemical Interrogation of FOXO3a Nuclear Translocation Identifies Potent and Selective Inhibitors of Phosphoinositide 3-Kinases*

Activation of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway is one the most frequent genetic events in human cancer. A cell-based imaging assay that monitored the translocation of the Akt effector protein, Forkhead box O (FOXO), from the cytoplasm to the nucleus was employed to screen a collection of 33,992 small molecules. The positive compounds were used to screen kinases known to be involved in FOXO translocation. Pyrazolopyrimidine derivatives were found to be potent FOXO relocators as well as biochemical inhibitors of PI3Kα. A combination of virtual screening and molecular modeling led to the development of a structure-activity relationship, which indicated the preferred substituents on the pyrazolopyrimidine scaffold. This leads to the synthesis of ETP-45658, which is a potent and selective inhibitor of phosphoinositide 3-kinases and demonstrates mechanism of action in tumor cell lines and in vivo in treated mice