Pre-treatment diagnostics of TKI for CML therapeutics utilizing fluorescence bioimaging technology (Förster Resonance Energy Transfer: FRET)

CML, chronic myelogenous leukemia, is a blood cancer that develops when the causative protein BCR-ABL appears in cells. TKIs, molecular targeted drugs that suppress the tyrosine kinase activity of BCR-ABL, have been used for treatment of CML. However, the problem is that a successful drug response is not known until treatment is actually started and follow-up is conducted. We have developed "opto-diagnostics" to detect the activity of BCR-ABL, utilizing the principle of Förster resonance energy transfer (FRET), with the substrate CrkL of BCR-ABL. This makes it possible to analyze the drug sensitivity of CML cells collected from patients at the single-cell level, prior to the start of treatment.

Förster Resonance Energy Transfer (FRET) Principle and Pickless

Fluorescence:Light of a specific wavelength is emitted by excitation light of a specific wavelength.
FRET:Fluorescence properties are changed by energy transfer when other fluorescent molecules are present in the vicinity, i.e., a phenomenon of color change.
i.e., a phenomenon of color change. blue yellow
Opto-diagnostics “Pickles” Pickles:Phosphorylation indicator of CrkL en substrate
Unphosphorylated form = TKI is effective → Blue, Phosphorylated form = TKI is ineffective → Yellow blue yellow

Procedure for determining drug efficacy

Day 0

0.bone marrow sampling

Day 1

1.Isolation of CML cells by density gradient centrifugation

2.Introduction of Opto-diagnostics “Pickles” into the CML cells by electroporation

Day 2

3.TKI treatment


Day 3

5.Image analysis

6. Determination of drug efficacy

Ineffective Effective

Preliminary Clinical Performance Tests

1.Typical samples from incipient patients
“Quick Responders” (patients who can achieve treatment-free remission): approx. 50%)12,000 patients × 0.5 × ¥2.5m/year= Medical cost reduction approx. ¥15 B/y in Japan.

Fluorescence bioimaging technology enables highly sensitive and
quantitative measurement of protein movement and
function in living cells.
Our goal is to apply this technology to clinical testing.