Abstract 4619: PF-04449913 reverts multi drug resistance (MDR) by a strong down-regulation of ABCA2 and BCL2 on leukemia stem cells in phase I acute myeloid leukemia and chronic myeloid leukemia treated patients
Authors: Papayannidis Cristina , Guadagnuolo Viviana , Iacobucci Ilaria , Durante Sandra , Terragna Carolina , Ottaviani Emanuela , Abbenante Maria Chiara , Cattina Federica , Soverini Simona , Lama Barbara , Toni Lucia , Levin Wendy , Courtney Rachel , Baldazzi Carmen , Curti Antonio , Baccarani Michele , Jamieson Catriona , Cortes Jorge , Oehler Vivian , McLachlan Karen , VanArsdale Todd , Martinelli Giovanni 
Published: August 2012

PF-04449913 is a selective and potent inhibitor of the Hh pathway and leukemia self-renewal and is currently being evaluated in Phase I clinical trials. We studied leukemia stem cell population (CD34+ subpopulation) collected before and after 28 days treatment in a phase I dose escalation protocol (Clinical Trial Gov. NTC00953758) enrolling selected hematological malignancies including MF, MDS, CML, CMML and AML. We collected and separated highly purified (98%) bone marrow hematopoietic progenitor cells (CD34+ populations) in 5 AML, 1 MF and 2 CML patients, by immunomagnetic separation, and analyzed them for gene expression profile (GEP) using Affimetrix HG-U133 Plus 2.0 platform. We have observed that 1197 genes were differentially expressed between CD34+ cells collected before and after 28 days of PF-04449913 dose finding oral therapy. We demonstrated a down regulation of Bcl2 (fold change –1.03004; p value= 0.01), ABCA2 (fold change –1.08966; p value=0.03), Bcl2l13 (fold change –1,04259; p-value=0,027642), Bcl2l2 (fold change –1,17214; p-value=0,000768), Casp4 (fold change –1,06551; p-value=0,032428), Casp7 (fold change –1,01569; p-value=0,006688), Casp10 (fold-change –1,3076; p-value=0,050431), ABCF1 (fold change –1,04999; p-value=0,07213). On the contrary, ABCB1 (fold change 1,46592) and ABCG2 (fold change –1,16103) are respectively up and down regulated, with a not statistically significant p-value. Bcl2 (B-cell lymphoma 2), Bcl2l2 (Bcl2-like protein 2) and Bcl2l13 (Bcl2-like 13) are the founding members of the Bcl-2 family of apoptosis regulator proteins. Recent studies showed that Hh signals upregulate Bcl2 to promote cellular survival. Casp 4,7,10 (Caspases) are a family of cysteine proteases that play essential roles in apoptosis, necrosis, and inflammation. ABCA2 (ATP-binding cassette sub-family A member 2), ABCF1 (ATP-binding cassette sub-family F member 1), ABCB1 (ATP-binding cassette sub-family B member 1, MDR1), ABCG2 (ATP-binding cassette sub-family G member 2) belong to the superfamily of adenosine triphosphate-binding cassette (ABC) transporters. One mechanism of MDR is the increased expression of ABC drug transporters, resulting in low intracellular drug concentrations. We evaluated Gli1 and Smo expression by GEP, comparing data before and after 28 days of treatment with PF-04449913 and we observed a down regulation of both genes (fold changes –1.0775 and –1.07702 respectively). PF-04449913 is able to revert MRD mechanisms of LSC by a strong down regulation of genes (Bcl-2, Bcl-2l13, Bcl-2l2, ABCA2, and ABCF1), which are critical for chemoresistance in acute and chronic leukemia patients. Acknowledgments. Pfizer, European LeukemiaNet, FIRB 2006, AIRC, AIL, COFIN, University of Bologna and BolognAIL.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4619. doi:1538-7445.AM2012-4619