Neuroblastoma xenograft models demonstrate the therapeutic potential of 177Lu-octreotate

Abstract

Background Neuroblastoma (NB) is one of the most frequently diagnosed tumors in infants. NB is a neuroendocrine tumor type with various characteristics and features, and with diverse outcome. The most malignant NBs have a 5-year survival rate of only 40–50%, indicating the need for novel and improved treatment options. 177Lu-octreotate is routinely administered for treatment of neuroendocrine tumors overexpressing somatostatin receptors (SSTR). The aim of this study was to examine the biodistribution of 177Lu-octreotate in mice bearing aggressive human NB cell lines, in order to evaluate the potential usefulness of 177Lu-octreotate for treatment of NB. Methods BALB/c nude mice bearing CLB-BAR, CLB-GE or IMR-32 tumor xenografts (n = 5–7/group) were i.v. injected with 0.15 MBq, 1.5 MBq or 15 MBq 177Lu-octreotate and sacrificed 1 h, 24 h, 48 h and 168 h after administration. The radioactivity concentration was determined for collected tissue samples, tumor-to-normal-tissue activity concentration ratios (T/N) and mean absorbed dose for each tissue were calculated. Immunohistochemical (IHC) staining for SSTR1–5, and Ki67 were carried out for tumor xenografts from the three cell lines. Results High 177Lu concentration levels and T/N values were observed in all NB tumors, with the highest for CLB-GE tumor xenografts (72%IA/g 24 h p.i.; 1.5 MBq 177Lu-octreotate). The mean absorbed dose to the tumor was 6.8 Gy, 54 Gy and 29 Gy for CLB-BAR, CLB-GE and IMR-32, respectively, p.i. of 15 MBq 177Lu-octreotate. Receptor saturation was clearly observed in CLB-BAR, resulting in higher concentration levels in the tumor when lower activity levels where administered. IHC staining demonstrated highest expression of SSTR2 in CLB-GE, followed by CLB-BAR and IMR-32. Conclusion T/N values for all three human NB tumor xenograft types investigated were high relative to previously investigated neuroendocrine tumor types. The results indicate a clear potential of 177Lu-octreotate as a therapeutic alternative for metastatic NB.

Adaptation of the Th-MYCN Mouse Model of Neuroblastoma for Evaluation of Disseminated Disease

“…The application of human NB xenografts has been useful for treatment evaluations [37][38][39]. Although recipient mice are profoundly immune-deficient, these models are amenable to assessment of some immune interventions, such as adoptive cell therapy [40,41].…”

Hyperfractionated Treatment with 177Lu-Octreotate Increases Tumor Response in Human Small-Intestine Neuroendocrine GOT1 Tumor Model

“…Saturation of SSTRs has been shown in studies on binding and internalization of 111 In-octreotide and 177 Lu-ocetrotate to various NET cells in primary culture, demonstrated as relatively higher binding after incubation with lower concentrations of the radiolabeled SS analogue [ 20 ]. SSTR saturation has also been shown in GOT1 and other NET animal models using radiolabeled SS analogues [ 17 , 25 , 36 ]. In SSTR-expressing normal tissues in rats, a bell-shaped binding curve for 111 In-octreotide was reported [ 24 ].…”

Synergistic Antitumor Effects of 177Lu-Octreotide Combined with an ALK Inhibitor in a High-Risk Neuroblastoma Xenograft Model

“…[31]. CLB-BAR cells were cultured as previously described [26]. A mixture of matrigel (Corning, 354248, VWR, USA) and 1.5×10 6 CLB-BAR cells were injected s.c. into the flank of 5-6 weeks old female BALB/c nude mice (Janvier Labs, France).…”

“…After fixation in formalin, tumor samples were embedded in paraffin, sectioned (thickness 4 µm), deparaffinized, rehydrated, and processed with the DAKO EnVision FLEX antigen retrieval EDTA buffer pH 9 using the DAKO PT Link (PT Link, Denmark) [26]. IHC staining was performed with anti-cleaved caspase-3 (CC3) (1:100, #9661, Cell Signaling Technology, MA, USA).…”

“…The closely related radiopharmaceutical, 177 Lu-octreotate, is FDA-and EMAapproved for treatment of gastroenteropancreatic neuroendocrine tumors. Previous preclinical and clinical studies have demonstrated selective uptake and therapeutic potential from the use of radiolabeled SSTAs for SSTR-positive HR-NB, however, the modest therapy effect in some of the studies highlights the need for optimization of these treatments [26][27][28][29]. An ongoing phase II study with 177 Lu-octreotate is now being conducted where an individualized treatment regimen is reviewed for children with relapsed HR-NB (Neuroblastoma-LuDO-N) [30].…”