Sensitivity to imatinib therapy may be predicted by testing Wilms tumor gene expression and colony growth after a short in vitro incubation.
BACKGROUND
The objective of the current study was to verify the ability to predict response to imatinib therapy using in vitro assays to evaluate the inhibition of Wilms tumor gene (WT1) expression and colony growth after samples obtained from patients with chronic myelogenous leukemia (CML) before the start of treatment were subjected to short-term incubation with imatinib.


METHODS
WT1 transcript levels and colony growth in bone marrow (BM) samples from 23 patients with CML that was later identified as being responsive to imatinib and from 13 patients with CML that was later identified as not being responsive to imatinib were evaluated after incubation of these samples with imatinib at a concentration of 1 microM for 18 hours. In addition, real-time quantitative polymerase chain reaction (RQ-PCR) analysis of WT1 expression was performed during follow-up, and the results were analyzed for associations with cytogenetic response and with BCR/ABL transcript levels as determined using RQ-PCR analysis.


RESULTS
Before treatment, it was found that WT1 expression was elevated in BM samples obtained from all patients with CML. WT1 expression and colony growth were reduced significantly after an 18-hour incubation with imatinib in samples obtained from patients who were later identified as responders to treatment, but not in samples obtained from patients who did not experience responses to treatment. Inhibition of WT1 expression in vitro was associated with inhibition of imatinib-induced BCR-ABL tyrosine kinase activity, a finding that also has been made in studies involving certain Philadelphia chromosome (Ph)-positive and Ph-negative cell lines.


CONCLUSIONS
Inhibition of WT1 transcript levels after a short period of in vitro exposure of pretherapy BM samples to imatinib was correlated with inhibition of colony growth and may represent the basis for an easy test that is capable of predicting the sensitivity of CML to treatment with imatinib for individual patients.
Cilloni
Daniela
D
Division of Hematology and Internal Medicine, Department of Clinical and Biological Sciences, University of Turin, Italy. daniela.cilloni@unito.it
Messa
Francesca
F
Gottardi
Enrico
E
Fava
Milena
M
Arruga
Francesca
F
Defilippi
Ilaria
I
Carturan
Sonia
S
Messa
Emanuela
E
Morotti
Alessandro
A
Giugliano
Emilia
E
Rege-Cambrin
Giovanna
G
Alberti
Daniele
D
Baccarani
Michele
M
Saglio
Giuseppe
G
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis; D001549:Benzamides; D001853:Bone Marrow / Q000473:pathology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D019008:Drug Resistance, Neoplasm; D005500:Follow-Up Studies; D016044:Fusion Proteins, bcr-abl / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000068877:Imatinib Mesylate; D066298:In Vitro Techniques; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D054438:Leukemia, Myeloid, Chronic, Atypical, BCR-ABL Negative / Q000378:metabolism; D010879:Piperazines / Q000627:therapeutic use*; D011379:Prognosis; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011743:Pyrimidines / Q000627:therapeutic use*; D012333:RNA, Messenger / Q000032:analysis*; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D025721:WT1 Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D025721:WT1 Proteins; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl