In general, hematological malignancies show consistent and recurrent balanced chromosomal translocations and a number of genes have been identified from their breakopoints. (http://cgap.nci.nih.gov/Chromosomes) Philadelphia chromosome (Ph) resulting from t(9;22)(q34;q11.2) is detected in 95% of patients with chronic myelogeneous leukemia (CML) and 20% of those with acute lymphocytic leukemia (ALL), and the three alterations in acute myelogeneous leukemia (AML), t(8;21)(q22;q22), t(15;17)(q22;q12) and inv(16)(p13q22), constitute 65% in unselected cases bearing a recurrent balanced chromosome translocations^.1,2) Those cancer-specific chromosome translocations can generate chimeric genes and their transcribed products or can deregulate expression of oncogenes located on the breakpoints themselves.¹⁾

The functional characterization of those genes important for understanding the pathogenesis of cancer and for clinical applications including optimal targets for cancer therapy to succeed the personalized medicine.³⁾ Indeed, detections of Ph chromosome, BCR/ABL rearrangements and expression of its aberrant transcript are now routinely utilized as the definite diagnosis of CML. Furthermore, imatinib mesylate (imatinib) (formerly STI571), a selective inhibitor of the protein tyrosine kinase associated with BCR/ABL and specifically inhibits proliferation of Ph-expressing cells, is widely used in the treatment of CML.⁴⁾ This drug is now a promising treatment option for CML that targets the molecular cause of the disease.

On the other hand, a limited number of recurrent aberrations has been clarified in epithelial solid tumors so far, although extensive cytogenetic analysis of them had been carried out as similar in hematological malignancies.^1,2) Conventional cytogenetics of epithelial solid tumors is difficult, because very few metaphase spreads are obtained after cell culture and their quality is often inadequate and/or complex to allow recognition of banding patterns. Therefore, in order to overcome this difficulty, for a long period, we had been looking forward to development of innovation in technique to identify specific chromosome aberrations associated with carcinogenesis in solid tumors.