A database of DNA fingerprint profiles from permanently established human and animal cell lines was prepared with a computer program originally designed for numerical taxonomy of bacteria. Identifications of cell line DNA profiles were performed, both by the Pearson product-moment correlation coefficient and by band matching. Under the conditions used the Pearson product-moment correlation coefficient was consistently more reliable.

IntroductionThe hypereosinophilic syndrome (HES) is a hematologic disease characterized by prolonged eosinophilia, exclusion of reactive eosinophilia, and organ damage. 1,2 HES is reclassified as chronic eosinophilic leukemia (CEL) when clonality is demonstrated. 3 We recently identified the kinase FIP1L1-platelet-derived growth factor receptor ␣ (PDGFR␣) as the cause and the therapeutic target of imatinib in 56% of HES cases. 4 These results demonstrate that most HES cases are clonal in origin and could be reclassified as FIP1L1-PDGFRA-positive CEL. The FIP1L1-PDGFRA fusion gene is created by an interstitial chromosomal deletion on chromosome 4q12 that is not apparent using standard karyotypic analysis. 4 Expression of the FIP1L1-PDGFRA fusion is under control of the ubiquitous FIP1L1 promoter, suggesting the possibility that FIP1L1-PDGFR␣ may be involved in the pathogenesis of other hematologic malignancies. To get insight into this, we screened 87 leukemia cell lines for the presence of the FIP1L1-PDGFRA fusion gene. Leukemia cell lines have been proven to be a valuable resource for the study of hematologic malignancies, 5 and our results now identify the EOL-1 cell line as an in vitro model for the study of FIP1L1-PDGFRA-positive CEL. Study design PCR and RT-PCRFIP1L1-PDGFRA fusion was amplified from DNA with primers FIP1L1-F9 (5Ј-tggggcaattgatgttatcg) and PDGFRA-RI12 (5Ј-gtgcaagggaaaagggagtct). RNA was isolated from cell lines from the DSMZ collection (http:// www.dsmz.de), as described. 6 Reverse transcription-polymerase chain reaction (RT-PCR) was performed with primers FIP1L1-F7 (5Ј-acctggtgctgatctttctgat) and PDGFRA-R14 (5Ј-tgagagcttgtttttcactgga) for the detection of FIP1L1-PDGFRA and primers PDGFRA-F11 (5Ј-ggtgctgttggtgattgtga) and FIP1L1-R10 (5Ј-cagctcctggagggaaaaac) for the detection of PDGFRA-FIP1L1. Primers PDGFRA-F11 and PDGFRA-R14 were used to detect PDGFRA expression, and primers FIP1L1-F7 and FIP1L1-R10 were used to detect FIP1L1 expression. Cell culture and dose-response curvesThe EOL-1 cell line (DSMZ ACC386) was grown in RPMI 1640 medium with 10% fetal bovine serum. Imatinib and PKC412 were kindly provided by Novartis; SU5614 was purchased from Calbiochem (San Diego, CA). Kinase inhibitors were stored in water (imatinib) or dimethyl sulfoxide (DMSO) (PKC412, SU5614) and diluted in RPMI 1640 medium. For dose-response curves, EOL-1 cultures were initiated at 3 ϫ 10 5 cells/mL, and viable cell numbers were determined at the beginning and after 48 hours using the Celltiter AQueousOne solution (Promega, Madison, WI). Dose-response curves were fitted using Origin (OriginLab, Northampton, MA). Detection of apoptosisApoptotic cells were detected by flow cytometric analysis using a FACSCalibur Cytometer (Becton Dickinson, Mountain View, CA) after staining with annexin V-fluorescein and propidium iodide (Roche, Indianapolis, IN). Western blotting and immunoprecipitationEOL-1 cells were treated with kinase inhibitors for 3 hours and then lysed in lysis buffer (Cell Signaling Technology, Beverly, MA) f...