External beam radiotherapy synergizes ¹⁸⁸Re-liposome against human esophageal cancer xenograft and modulates ¹⁸⁸Re-liposome pharmacokinetics

Figures & data

Figure 1 Labeling efficiency of ¹⁸⁸Re-BMEDA.

Notes: Labeling efficiency of ¹⁸⁸Re-BMEDA was analyzed by using silica gel–impregnated glass fiber sheets. Before labeling with BMEDA (A), ¹⁸⁸Re, R_f value: 0.8–1.0. After labeling with BMEDA (B), ¹⁸⁸Re-BMEDA migrated slower than ¹⁸⁸Re and R_f value: 0.2, separating from ¹⁸⁸Re. The labeling efficiency of ¹⁸⁸ Re-BMEDA was approximately 96.7%±5.8%.

Abbreviation: ¹⁸⁸Re-BMEDA, ¹⁸⁸Re-N,N-bis(2-mercapatoethyl)-N′,N′-diethylenediamine.

Figure 2 Uptake of ¹⁸⁸Re-liposome in human esophageal cancer xenografts.

Notes: Esophageal tumor cells CE81T/VGH (A) and BE-3 (B) were inoculated in the hind limbs of nude mice. After tumors grew over 200 mm³ in size, the mice were intravenously injected with 18.5 MBq (500 μCi) of ¹⁸⁸Re-liposome and NanoSPECT/CT imaging was carried out at 24 hours after injection. Arrow indicates the uptake of ¹⁸⁸Re-liposome in the BE-3 tumor-bearing mice model (n=3).

Abbreviations: NanoSPECT/CT, nano single photon emission computed tomography/computed tomography; ¹⁸⁸Re, Rhenium-188.

Table 1 Impact of EBRT on biodistribution of ¹⁸⁸Re-liposome

^188Re-liposome	0 Gy				3 Gy
Organ	1 hour	4 hours	24 hours	48 hours	1 hour	4 hours	24 hours	48 hours
Brain	1.99±0.87	1.23±0.65	0.14±0.02	0.05±0.01	1.66±0.98	1.63±1.24	0.18±0.04	0.05±0.01
Heart	3.21±0.37	2.55±0.78	0.93±0.04	0.36±0.10	3.38±0.61	2.82±0.15	1.08±0.07	0.40±0.04
Lung	8.02±1.17	4.75±0.99	1.60±0.24	0.53±0.09	8.13±3.40	5.27±0.82	1.81±0.18	0.58±0.03
Tongue	3.13±0.36	2.43±0.52	1.14±0.11	0.64±0.14	2.42±0.19	2.98±0.47	1.27±0.28	0.43±0.08*
Oral cavity	2.13±0.40	1.28±0.16	0.57±0.02	0.35±0.07	1.70±0.40	1.30±0.34	0.55±0.12	0.27±0.02*
Esophagus	3.26±0.86	2.37±0.91	1.02±0.32	0.73±0.23	2.10±0.63	1.60±0.41	1.09±0.32	0.46±0.13*
Liver	20.10±2.34	15.12±2.47	12.06±0.93	7.27±1.74	16.96±2.08*	16.78±1.17	13.29±1.31	6.06±1.09
Stomach	1.17±0.15	1.43±0.17	1.85±0.29	0.67±0.19	1.40±0.18	1.35±0.18	2.03±0.27	0.83±0.10
SI	5.32±3.40	6.68±0.79	5.72±1.05	1.59±0.45	5.50±1.42	5.15±2.59	7.46±3.47	2.26±0.24*
LI	2.56±1.57	1.34±0.31	1.25±0.36	0.57±0.26	1.49±0.82	2.15±1.94	1.60±0.34	0.61±0.16
Pancreas	1.85±0.32	1.20±0.36	0.60±0.13	0.22±0.04	1.65±0.70	1.39±0.28	0.75±0.16	0.31±0.04*
Spleen	5.33±0.30	7.78±1.64	6.16±0.40	4.15±0.85	7.30±0.75*	7.88±0.67	9.23±1.50*	4.76±0.57
Kidney	6.73±0.16	5.46±1.13	3.36±0.11	1.40±0.21	5.44±1.44	5.25±0.36	3.36±0.35	1.55±0.14
Testis	0.59±0.11	0.50±0.15	0.24±0.01	0.13±0.03	0.66±0.21	0.59±0.10	0.30±0.04	0.12±0.02
Muscle	0.64±0.36	0.35±0.09	0.24±0.04	0.18±0.06	0.64±0.18	0.44±0.06	0.31±0.05	0.13±0.01
Skin	0.45±0.07	0.33±0.05	0.19±0.07	0.08±0.03	0.36±0.09	0.27±0.07	0.27±0.12	0.11±0.03
Bone	0.60±0.22	0.27±0.15	0.23±0.09	0.06±0.03	0.59±0.17	0.53±0.36	0.33±0.14	0.08±0.08
Bone marrow	6.55±6.08	1.64±1.15	0.98±0.78	0.34±0.30	8.75±5.22	2.39±1.74	1.56±0.80	0.14±0.14
Lymph node	0.61±0.75	1.01±0.09	1.32±0.15	0.60±0.23	1.16±0.44	1.05±0.40	1.60±0.30	0.66±0.20
Urine	5.69±2.01	5.69±3.37	9.78±1.13	4.49±0.76	5.90±2.12	4.58±2.07	15.90±1.90*	8.58±2.70*
Blood	38.17±2.24	23.12±4.47	6.66±1.03	1.22±0.35	36.96±7.25	30.85±3.10*	6.60±1.53	0.72±0.12
Feces	0.20±0.13	8.96±6.37	35.60±2.83	8.38±3.08	0.42±0.49	9.65±1.93	46.93±11.81	12.28±1.56
Tumor	2.60±0.41	3.16±0.68	2.80±0.28	1.48±0.52	2.60±0.49	2.83±0.25	3.13±0.78	1.30±0.36
T/M ratio	4.07	9.02	11.83	8.41	4.06	6.36	10.24	10.27

Notes:

Biodistribution of ¹⁸⁸Re-liposome after intravenous injections with or without 3 Gy irradiation in BE-3 tumor-bearing mice was assessed. Values are expressed as percentages of injected dose per gram (% ID/g ± SD, n=3–4 at each time point).

* P<0.05 compared with no irradiation control.

Abbreviations: EBRT, external beam radiotherapy; SI, small intestine; Gy, gray; LI, larger intestine; SD, standard deviation; T/M, tumor/muscle.

Figure 3 Effect of ¹⁸⁸Re-liposome uptake by EBRT.

Notes: BE-3 tumor-bearing mice (n=3–4) were irradiated with 3, 6, and 9 Gy followed by intravenous injection of ¹⁸⁸Re-liposome (2.22 MBq, 60 μCi), and mice with no irradiation (0 Gy) indicated control group. The radioactivity of ¹⁸⁸Re-liposome in tumor, liver, and feces was measured at 24 hours postinjection and detected by using auto-gamma counter. The uptake of ¹⁸⁸Re-liposomes was expressed as the percentage of injected dose per gram of indicated tissue (% ID/g). *P<0.05 compared with 0, 3, or 6 Gy groups.

Abbreviations: EBRT, external beam radiotherapy; Gy, gray; IR, ionizing radiation.

Figure 4 Therapeutic effect of EBRT and ¹⁸⁸Re-liposome.

Notes: For combination treatment, BE-3 tumor-bearing mice received external beam radiotherapy (IR, 3 Gy) followed by radionuclide therapy (¹⁸⁸Re-liposome, 13.2 MBq [360 μCi]). Single treatments of EBRT and RNT and injections of normal saline and liposomes were used for comparison. Tumor volume was recorded twice weekly, except for the first week after injection in the BE-3 tumor-bearing mice (n=5). *P<0.05 compared with single treatment groups.

Abbreviations: EBRT, external beam radiotherapy; IR, ionizing radiation; PBS, phosphate buffer saline; RNT, radionuclide therapy.

Figure 5 Biological toxicity of EBRT and ¹⁸⁸Re-liposome.

Notes: For combination treatment, BE-3 tumor-bearing mice received EBRT (IR, 3 Gy) followed by radionuclide therapy (¹⁸⁸Re-liposome, 13.2 MBq [360 μCi]). Single treatments of EBRT and RNT and injections of normal saline and liposomes were used for comparison. Mice weight (A), white blood cells (WBC) (B), liver function markers alanine aminotransferase (ALT) (C), and kidney function markers creatinine, (CRE) (D) were freshly analyzed twice weekly, except for the first week after injection in BE-3 tumor-bearing mice (n=5).

Abbreviations: EBRT, external beam radiotherapy; IR, ionizing radiation; PBS, phosphate buffer saline; RNT, radionuclide therapy.