Non-invasive longitudinal imaging of tumor progression using an (111)indium labeled CXCR4 peptide antagonist

Abstract

The chemokine receptor 4 (CXCR4) is a biomarker that is over-expressed in ductal carcinoma in situ (DCIS). Hence, CXCR4-targeted (molecular) imaging approaches may have diagnostic value in such a challenging, premalignant lesion. The indium labeled CXCR4 peptide-antagonist, (111)In-DTPA-Ac-TZ14011, was used to visualize CXCR4-expression in a mammary intraepithelial neoplastic outgrowth (MIN-O) mouse tumor model resembling human DCIS. MIN-O lesion development was longitudinally monitored using SPET/CT and tracer uptake was compared to uptake in control lesions. Expression of CXCR4 was validated using immunohistochemistry and flow cytometric analysis. The uptake of (111)In-DTPA-Ac-TZ14011 was related to tumor angiogenesis using (111)In-cDTPA-[RGDfK]. Twenty-four hours after tracer injection, MIN-O lesions could be discriminated from low CXCR4-expressing control tumors, while the degree of angiogenesis based on the α(v)β(3) integrin expression in both tumor types was similar. The uptake of (111)In-DTPA-Ac-TZ14011 in early MIN-O lesions was significantly lower than in larger intermediate and late-stage lesions, two-and-a-half-times (p=0.03) and seven-times (p=0.002), respectively. Intermediate and late stage lesions show a higher degree of membranous CXCR4-staining at immunohistochemistry and flow cytometric analysis. From this study we can conclude that (111)In-DTPA-Ac-TZ14011 can be used to visualize the CXCR4-expression in MIN-O lesions longitudinally.

Keywords: Chemokine receptor 4 (CXCR4); ductal carcinoma in situ (DCIS); longitudinal imaging; mouse model; single photon emission computed tomography (SPECT); tumor progression.

Figure 1

Longitudinal SPECT/CT imaging of ¹¹¹In-DTPA-AC-TZ14011. A) Chemical structure of DTPA-Ac-TZ14011. Tumor uptake of ¹¹¹In-DTPA-Ac-TZ14011 measured at B) 1 hour and C) 24 hours after injection was set out against the tumor volume. D) Uptake in tumors within the same size range was compared. E) SPECT/CT images (MIP) of MIN-O and 4T1 tumor lesions at 24 hours after injection. F) Ex vivo tracer distribution in a 4T1 (i) and MIN-O (ii) tumor lesion after SPECT/CT imaging. Significance between uptake values was determined using a T-test. Not significant was noted as ns, p-values < 0.02 for comparison with late stage MIN-O lesions were noted as ** and p-values < 0.002 as ***. n.d. = not determined.

Figure 2

Immunohistochemistry: CXCR4 staining in 4T1 and MIN-O tumor tissue. A) Distribution of the CXCR4 staining of the different MIN-O tumor stages. B) At a 25x magnification, in 4T1 tumor tissue only cytoplasmatic staining can be seen. In MIN-O tumor tissue, next to cytoplasmatic staining, an increasing level of membranous staining is observed. C) Membranous staining at 40x magnification.

Figure 3

Longitudinal SPECT/CT imaging of ¹¹¹In-DTPA-c[RGDfK]. A) Tumor uptake of ¹¹¹In-DTPA-c[RGDfK] was longitudinally monitored at 24 hours after injection. B) Uptake in tumors of tumors within the same size range were compared.