Intermittent and continuous imatinib in a human GIST xenograft model carrying KIT exon 17 resistance mutation D816H

Figures & data

Figure 1. The three-compartment model used for extracting pharmacokinetic information from dynamic ¹⁸F-FDG PET. C_P is the concentration of ¹⁸F-FDG in plasma, and the tissue concentration C_T is composed of non-metabolized, or free, ¹⁸F-FDG CF, and metabolized, or bound, ¹⁸F-FDG, CB. C_T is further separated into not metabolised or free ¹⁸F-FDG, C_F, and metabolised or bound ¹⁸F-FDG, C_B. The kinetic parameters k₁ (min⁻¹) and k₂ (min⁻¹) describe the forward and backward ¹⁸F-FDG diffusion, respectively. The k₃ (min⁻¹) and k₄ (min⁻¹) parameters signify the rates of ¹⁸F-FDG phosphorylation and dephosphorylation, respectively, i.e., reflecting protein binding or glucose metabolism.

Table I. The primary antibodies used for immunohistochemistry.

Antibody target	Company	Catalogue number	Dilution	Retrieval solution pH*	Positive control
GLUT-1	Abcam, Cambridge, UK	Ab652	1:200	Low pH	Kidney cancer
GLUT-2	Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA	Sc-9117	1:100	Low pH	Pancreas
GLUT-3	Abcam, Cambridge, UK	Ab53095	1:200	High pH	Testis
GLUT-4	AbD Serotec, Oxford, UK	4670-1704	1:1000	High pH	Salivary gland
HIF-1α	Novus Biologicals, Cambridge, UK	NB100–499	1:300	High pH	Placenta
Caspase-3	Cell Signaling Technology, Danvers, MA, USA	9664	1:100	High pH	Large cell lymphoma

*Low pH: citrate buffer, pH 6.1 (K8005, Dako, Glostrup, Denmark). High pH: Tris/EDTA, pH 9 (K8004, Dako, Glostrup, Denmark).

Figure 2. Normalised tumour volume growth of the human GIST AHAX xenograft in mice receiving either imatinib (100 mg/kg/day) continuously, intermittently (one week on, one week off) or placebo (water). At the end of experiment, mice with particularly large tumours were scarified, causing a dip in tumour volume growth (the light grey symbols). The data are given as means and standard errors of the means.

Figure 3. An example of cumulative ¹⁸F-FDG uptake with time in a human GIST AHAX xenograft model (A). The white arrows point at the tumour. ¹⁸F-FDG uptake as a function of time for two selected voxels within the xenograft is shown in (B). The uptake curves for the free and bound ¹⁸F-FDG components obtained from kinetic modeling are provided.

Table II. Results from pharmacokinetic modelling of dynamic ¹⁸F-FDG PET data. Data are given as median values.

	Treatment group
Parameter	Intermittent imatinib	Continuous imatinib	p*
k1 (min^−1)	0.066	0.050	0.005
k2 (min^−1)	0.100	0.087	0.386
k3 (min^−1)	0.007	0.013	0.011
MRFDG (min^−1)	0.004	0.006	0.028
vB	0.007	0.002	0.149

k₁, k₂ and k₃ are the kinetic rate constants from the three-compartment model shown in Figure 1; MR_FDG, the metabolic rate of ¹⁸F-FDG; v_B, the estimated blood volume.

*p for the difference between the intermittent and continuous imatinib groups.