Gastrointestinal stromal tumors (GISTs) express somatostatin receptors and bind radiolabeled somatostatin analogs

Figures & data

Table I. Clinico-pathological and genetic characterization of 34 patients with gastrointestinal stromal tumor.

	Primary tumor				Therapy				Follow-up
Pat. no.	Age/Sex	Site	NIH risk	Mutation	Surgery	Imatinib setting	Observed response to imatinib	Second-line treatment	Disease status	Survival RFS/OAS (months)
1	82/F	S	inter.	KIT(11) D579 del	R0	no	n.d.	–	DOC	39/39
2	71/F	S	inter.	KIT(11) D579 del	R0	no	n.d.	–	NED	87/87
3	48/M	S	high	KIT(11) W557_E561 del	R2	P	resistant (secondary)	sunitinib	DOD	0/65
4	67/M	S	high	KIT(11) W557_E561 del	R0	A	responsive; rec/responsive	–	AWD	60/68
5	74/M	S	high	KIT(11) W557_K558 del	R1	N, A	responsive; rec/resistant	–	AWD	18/62
6	66/F	S	high	KIT(11) W557_Q575 del	R2	P	n.d.^e	–	DOD	0/60
7	63/M	S	high	KIT(11) E579_F591 dup	R0	N, A	responsive; rec/responsive	–	AWD	37/50
8	77/M	S	inter.	KIT(11) P573_Y578 dup	R0	no	n.d.	–	NED	31/31
9	71/M	S	high	KIT(11) Y578_H580 dup	R0	N, A	responsive	–	NED	103/103
10	59/F	S	high	KIT(11) V559A mis	R0	A	responsive	–	NED	66/66
11	65/M	S	low	KIT(11) V560D mis	R0	no	n.d.	–	NED	101/101
12^a	15/F	S	low	KIT/PDGFRA (wt)	R0	no	n.d.^f	–	AWD	131/552
13^b	10/F	S	high	KIT/PDGFRA (wt)	R0	no	n.d.^f	–	AWD	48/228
14	66/M	S	low	PDGFRA(18) D842V mis	R0	no	n.d.^f	–	NED	50/50
15	65/M	S	low	PDGFRA(18) D842V mis	R0	A	resistant (primary)^f	sunitinib	NED	24/24
16	60/F	S	low	PDGFRA(18) I843_D846 del	R0	A	responsive	–	NED	75/75
17	69/M	SI	high	KIT(9) A502_Y503 dup	R2	P	resistant (secondary)	sunitinib	DOD	0/33
18	68/M	SI	high	KIT(9) A502_Y503 dup	R0	N, A	responsive; rec/responsive	–	AWD	28/65
19	63/M	SI	high	KIT(9) A502_Y503 dup	R2	P	resistant (primary)	–	DOD	0/15
20	55/F	SI	high	KIT(11) P551_Q556 del	R0	A	responsive; rec/responsive	–	AWD	37/68
21	35/M	SI	high	KIT(11) V555_Q575 del	R0	A	responsive; rec n.d.	–	AWD	46/84
22	71/M	SI	high	KIT(11) V559_E561 del	R2	P	resistant (secondary)	–	DOD	0/67
23	36/M	SI	high	KIT(11) V560_D572 del	R0	A	responsive	–	NED	60/60
24	42/F	SI	high	KIT(11)P551_Y568 V579 del	R2	no	n.d.	–	DOD	0/24
25	74/M	SI	high	KIT(11) P573_Y578 dup	R2	P^d	responsive; rec/responsive	–	AWD	0/78
26	75/M	SI	inter.	KIT(11) W557R mis	R0	no	n.d.	–	NED	46/46
27	60/M	SI	low	KIT(11) V559D mis	R0	A	responsive	–	NED	60/60
28^c	64/M	SI	low	KIT/PDGFRA (wt)	R0	A	responsive^f	–	NED	94/94
29	70/M	SI	high	KIT/PDGFRA (wt)	R2	A	resistant (primary)^f	–	DOD	0/23
30	57/M	SI	high	KIT/PDGFRA (wt)	R2	P	resistant (primary)^f	–	DOD	0/18
31	75/M	SI	high	PDGFRA(18) D842V mis	R1	P	resistant (primary)^f	–	DOD	20/34
32	48/M	R	high	KIT(11) K558_V560 del	R0	A	responsive	–	NED	112/112
33	73/M	R	high	KIT(11) K558S W559 del	R2	P^d	resistant (secondary)	rapamycin	DOD	0/55
34	55/M	R	low	KIT(11) W557M mis	R1	A	responsive; rec/responsive	–	AWD	79/264

A, adjuvant treatment; AWD, alive with disease; del, deletion; DOC, dead of other cause; DOD, dead of disease; dup, duplication; F, female; inter., intermediate-risk; M, male; mis, missense; N, neoadjuvant treatment; n.d., not determined; NED, no evidence of disease; OAS, overall survival; P, palliative treatment; Pat. no., patient number; R, rectum; R0, radical surgery; R1, microscopically, not radical surgery; R2, macroscopically, not radical surgery; rec, late recurrence; RFS, recurrence-free survival; S, stomach; SI, small intestine; wt, wild-type.

^apediatric GIST patient with Carney triad [17].

^bpediatric GIST patient.

^cpatient with NF1 and Carney-Stratakis syndrome [17].

^dpatient on imatinib treatment at time for surgery.

^etreatment terminated due to adverse effects of TKI.

^fprimary resistance expected from mutational status.

Figure 1. (A) Comparison of tumor-to blood activity concentrations between patients with GIST and NE tumors, i.e. medullary thyroid carcinoma (MTC) and midgut carcinoids (MC). The ratios are classified as groups dependent on disease type and time after injection. Data on T/B values in MTC and MC were from Forssell-Aronsson et al. [18]. In general MC had higher ratios than MTC (biopsied according to the same time scale). On the other hand, GIST were biopsied according to a protracted time scale making direct comparison difficult. However, the GIST patient with highest T/B ratio (96) long time after injection (13 days) seemed to be suitable for PRRT. (B) Comparison of SSTR mRNA values in GIST tumors (n = 34) compared to NE tumors (MTC, n = 5; MC, n = 12). MTC and MC showed high expression of SSTR2&5 (with high affinity for octreotide/octreotate), while GIST have much lower expression of these two receptor subtypes.

Table II. Expression profiles of somatostatin receptors in gastrointestinal stromal tumors. Biopsies from 34 patients with GIST were analyzed by real-time qPCR and IHC. qPCR values are expressed as fold change of target gene per 1000 ACTB copies. IHC labeling was scored as the number of positive tumor cells: - = no labeling, 1+ = 10–25%, 2+ = 25–75%, 3+ = > 75%.

		qPCR						IHC
Pat. no.	Tumor tissue	SSTR1	SSTR2	SSTR3	SSTR4	SSTR5	SSTR1	SSTR2	SSTR3	SSTR4	SSTR5
1	P	99.20	0.01	–	0.10	0.02	3+	3+	–	–	–
2	P	0.06	0.31	0.01	–	–	3+	2+	–	–	–
3	P	–	0.26	–	–	0.07	3+	3+	–	–	–
4	P	0.01	0.15	–	–	0.03	3+	3+	–	–	–
5	P	0.06	1.50	–	–	–	3+	3+	–	–	–
6	P	0.29	0.14	–	0.14	–	3+	2+	–	–	–
7	P	196.15	0.08	–	–	–	3+	3+	–	–	–
8^a,b	P	110.85	0.66	–	–	–	3+	3+	–	–	–
9	P	1.84	1.17	–	–	–	3+	3+	3+	–	–
10	P	0.01	1.42	–	–	–	3+	3+	–	–	–
11	P	1.16	0.17	–	0.01	–	3+	3+	–	–	–
12	R	34.99	1.32	–	–	–	3+	3+	3+	–	2+
13	R	0.27	1.19	–	0.09	0.01	3+	3+	1+	–	3+
14	P	85.36	0.12	–	–	–	3+	3+	1+	–	–
15^c	P	107.09	0.38	–	–	–	3+	3+	1+	–	–
16	P	15.18	1.34	–	–	–	3+	3+	2+	–	–
17	R	90.11	0.28	–	–	–	3+	2+	1+	–	–
18	P	0.04	0.36	–	–	0.11	3+	3+	–	–	–
19^a,b	P	0.27	0.10	–	–	–	3+	3+	–	–	2+
20	R	0.27	2.34	–	–	0.22	3+	2+	–	–	–
21	P	2.09	3.26	–	–	0.16	3+	3+	–	–	2+
22	P	0.27	0.46	–	0.08	–	3+	3+	–	–	–
23	P	0.12	0.64	–	0.01	0.11	3+	3+	–	–	–
24	R	0.05	0.22	–	0.04	0.10	3+	3+	–	–	–
25^a,b,c	R	444.88	0.60	–	0.01	0.01	3+	3+	–	–	3+
26	P	0.07	0.14	–	–	–	3+	3+	–	–	–
27	P	1.05	0.17	–	–	0.01	3+	3+	1+	–	–
28	P	0.18	0.63	–	0.01	0.11	3+	3+	1+	–	–
29^a,b	P	0.13	0.38	–	0.01	–	3+	2+	–	–	–
30	P	0.51	0.18	–	–	0.01	3+	3+	–	–	–
31^a	P	243.26	0.18	–	–	–	3+	3+	2+	–	–
32^b	P	403.72	0.16	–	12.23	–	3+	2+	–	–	–
33	R	3.34	0.76	0.06	0.03	0.05	3+	3+	–	–	–
34^a	P	0.04	0.08	–	0.03	–	3+	2+	–	–	–

IHC, immunohistochemistry; P, primary tumor analyzed; pPCR, quantitative real-time polymerase chain reaction; R, recurrent tumor analyzed; SSTR, somatostatin receptors; -, not detectable.

^aanalyzed by SSTR scintigraphy (OctreoScan^®).

^banalyzed for tumor-to-blood (T/B) ratio.

^canalyzed in cell culture.

Figure 2. Expression of somatostatin receptor protein in GIST. SSTR1, 2, 3, and 5 proteins localized to tumor cell cytoplasm. SSTR4 protein was undetectable. Immunoperoxidase staining of consecutive sections from tumor biopsy from patient no. 12 (small intestinal, low-risk, wt in KIT and PDGFRA). Brown = antibody labeling. Blue = nuclear counter staining. Left panel (A, C, E, G, I): low power (bar equals 50 μm). Right panel (B, D, F, H, J): high power (bar equals 20 μm). *indicates luminal side of vascular profile.

Figure 3. GIST in primary culture. Tumor cells were positive for the GIST markers KIT and DOG1 (ANO1). The marker CD34 was positive in one tumor. Tumor cells also expressed SSTR1 and 2 with membrane and cytoplasmic labeling. (A–E) Patient no. 15 (gastric, low-risk, PDGFRA exon 18 (D842V) missense mutation). (F–J) Patient no. 25 (small intestinal, high-risk, KIT exon 11 (P573_Y578) duplication mutation). Immunofluorescent labeling and confocal laser microscopy; antibody labeling in green color and DAPI-stained nuclei in blue color. Bar equals 20 μm.

Figure 4. SSTR scintigraphy and tumor-to-blood ¹¹¹In activity concentration ratios (T/B) in tumor biopsies from GIST patients injected with ¹¹¹In-DTPA-D-Phe¹-octreotide. (A) Tumor imaging of patient no. 25 with primary small intestinal GIST non-radically resected, and multiple abdominal (arrows) and liver (double arrow) recurrences four years after primary surgery. The primary tumor had KIT exon 11 duplication mutation and responded to imatinib. (B) Tumor imaging of patient no. 29 with primary GIST close to the ligament of Treitz (arrow) and multiple liver metastases in the right liver lobe (double arrow). This patient was wt for KIT and PDGFRA and resistant to imatinib. The patient survived for only two years after surgery. (C) Summary of observations at SSTR-scintigraphy and maximal T/B values in GIST patients.

Figure 5. Binding and internalization of ¹⁷⁷Lu-DOTA-Tyr³-octreotate in cultured GIST cells. Tumor cells were cultured with ¹⁷⁷Lu-octreotate (10 nM) with or without unlabeled octreotide (5 μM). The fraction of unbound, surface-bound, and internalized ¹⁷⁷Lu in GIST tumor cells was measured after 4, 24, and 48 hours. Values represent mean of 4–8 replicates. Error bars are smaller than symbols. Internalization of ¹⁷⁷Lu was significantly higher in ¹⁷⁷Lu-octreotate-incubated tumor cells than in controls (p < 10^-15). The amount of internalized ¹⁷⁷Lu increased steadily during the incubation period. (A–C) Patient no. 15 (gastric, low-risk, PDGFRA exon 18 (D842V) missense mutation; SSTR1/2 mRNA values: 107/0.38). (D–F) Patient no. 25 [small intestine, high-risk, KIT exon 11 (P573_Y578) duplication mutation; SSTR1/2 mRNA values: 445/0.60; clearly positive imaging; T/B: 96]. Further statistical details are presented in Supplementary Table 2 to be found online at http://informahealthcare.com/doi/abs/10.3109/0284186X.2012.733075.

Nilsson O, Kölby L, Wängberg B, Wigander A, Billig H, William-Olsson L, et al. Comparative studies on the expression of somatostatin receptor subtypes, outcome of octreotide scintigraphy and response to octreotide treatment in patients with carcinoid tumours. Br J Cancer 1998;77:632–7.

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