Gas1 and Kif27 Genes Are Strongly up-Regulated Biomarkers of Hedgehog Inhibition (PF-04449913) on Leukemia Stem Cells in Phase I Acute Myeloid Leukemia and Chronic Myeloid Leukemia Treated Patients

• Published in: Blood 2011-11, Vol.118 (21), p.1535-1535
• Main Authors: Guadagnuolo, Viviana, Papayannidis, Cristina, Iacobucci, Ilaria, Durante, Sandra, Terragna, Carolina, Ottaviani, Emanuela, Abbenante, Maria Chiara, Cattina, Federica, Soverini, Simona, Lama, Barbara, Toni, Lucia, Levin, Wendy J., Courtney, Rachel, Baldazzi, Carmen, Curti, Antonio, Baccarani, Michele, Jamieson, Catriona, Cortes, Jorge E., Oehler, Vivian, McLachlan, Karen, Van Arsdale, Todd, Martinelli, Giovanni
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V118.21.1535.1535

Abstract 1535 Recent studies show that uncontrolled Hedgehog (Hh) pathway activation contributes to leukemia development and growth, and that targeted pathway inhibition is likely to offer an efficient therapeutic opportunity. PF-04449913, a Hh pathway inhibitor, is a new selective and potent inhibitor of leukemia self-renewal and is currently being evaluated in phase I clinical trials. In order to identify new potential clinical biomarkers for the PF-04449913 (Hh inhibitor), 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. This experimental clinical trial enrolled Myelofibrosis (MF), MDS, blastic phases Chronic Myeloid Leukemia (CML), chronic myelomonocytic leukemia (CMML) and Acute Myeloid Leukemia (AML) patients. We were able to collect and separate highly purified (98%) bone marrow hematopoietic progenitor cells (CD34+ populations) from 5 AML, 1 MF and 2 CML patients by immunomagnetic separation, and analysed 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. Clustering of their expression profiles showed that mostly genes differentially expressed are mainly related to Hh signaling,this providing further evidences that PF-04449913 really therapeutically targets the Hh pathway. Regarding genes involved in Hh signaling pathway, Gas1 and Kif27 were strongly upregulated (fold change 1.0947 and 1.12757 respectively; p-value 0.01 and 0.02 respectively) in CD34+ leukemia stem cells after 28 days exposure to PF-04449913 as compared to baseline, suggesting these two genes have potential as new biomarkers of activity. GAS-1 (growth arrest specific 1 gene) is a Sonic Hedgehog (Shh)-binding protein; it acts to sequester Shh and inhibit the Shh signalling pathway. Kif27 (kinesin family member 27) mainly acts as a negative regulator in the Hh signaling pathway, and inhibits the transcriptional activator activity of Gli1 by inhibiting its nuclear translocation. Other genes were differentially expressed after ‘ex- vivo' treatment with PF-04449913 as compared to baseline: we observed a down regulation of Bcl2 (fold change −1.03004), ABCA2 (fold change −1.08966), LEF1 (fold change −1.28457), Gli1 (fold chan