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Representative 3D-rendering of segmented MCF-7, MDA-MB-468 and MDA-MB-231 xenografts following PET/CT image acquisition 3 h after 89Zr-DFO-ZHER3:8698 injection.

Purpose: Recent studies have highlighted a role of HER3 in HER2-driven cancers (e.g., breast cancer), implicating the upregulation of the receptor in resistance to HER-targeted therapies and Hsp90 inhibitors (e.g., AUY922). Therefore, we have developed an affibody-based PET radioconjugate that quantitatively assesses HER3 changes induced by Hsp90 inhibition in vivo.Experimental Design: ZHER3:8698 affibody molecules were conjugated via the C-terminus cysteine to DFO-maleimide for 89Zr radiolabeling. The probe was characterized in vitro and in vivo in a panel of human breast cell lines and xenograft models with varying HER3 receptor levels. In addition, the radioconjugate was investigated as a tool to monitor the outcome of AUY922, an Hsp90 inhibitor, in an MCF-7 xenograft model.Results: We demonstrated that 89Zr-DFO-ZHER3:8698 can track changes in receptor expression in HER3-positive xenograft models and monitor the outcome of AUY922 treatment. Our in vitro findings showed that MCF-7 cells, which are phenotypically different from BT474, develop resistance to treatment with AUY922 through HER3/IGF-1Rβ–mediated signaling. Of note, the lack of response in vitro due to HER3 recovery was confirmed in vivo using 89Zr-DFO-ZHER3:8698–based imaging. Upon AUY922 treatment, higher radioconjugate uptake was detected in treated MCF-7 xenografts, correlating with an AUY922-induced HER3 upregulation concomitant with an increase in IGF-1Rβ expression.Conclusions: These data underline the potential of HER3-based PET imaging to noninvasively provide information about HER3 expression and to identify patients not responding to targeted therapies due to HER3 recovery. Clin Cancer Res; 24(8); 1853–65. ©2018 AACR.

Materials and Methods Fig. S1. Time course of AUY922 treatment in BT-474 and MCF-7 cells. Fig. S2. Effects of AUY922 and PPP treatment in low and high HER2-expressing breast cancer cell lines. Fig. S3. Effect of HRG stimulation in AUY922 and PPP treated MCF-7 cells. Fig. S4. AUY922 and PPP treatment effect on the proliferative and invasive phenotype of BT-474 and MCF-7 breast cancer cells. Fig. S5. HPLC chromatograms of purified DFO-affibody conjugates. Fig. S6. MALDI-MS spectra of purified DFO-ZHER3:8698 (A) and DFO-ZTAQ (B). Fig. S7. Representative radio-ITLC of the crude radiolabelling mixture of 89Zr-DFO-ZHER3:8698. Fig. S8. Representative radio-ITLC of the 89Zr-DFO-ZHER3:8698 serum stability at 0, 3 and 24 h. Fig. S9. In vivo 89Zr-DFO-ZHER3:8698 tumour uptake quantification by image analysis. Fig. S10. Ex vivo biodistribution of 89Zr-DFO-ZHER3:8698 following AUY922 treatment in MCF-7 xenografts. Fig. S11. Microvessel density analysis in response to AUY922 treatment in MCF-7 xenografts. Fig. S12. Tumour volume estimation in response to AUY922 treatment in MCF-7 xenografts. Fig. S13. AUY922 treatment response monitoring in BT-474 xenografts by 89Zr-DFO-ZHER3:8698 PET/CT imaging. Fig. S14. Texture analysis of 89Zr-DFO-ZHER3:8698 PET imaging data following AUY922 treatment in MCF-7 xenografts. Fig. S15. Correlation between %ID/g ratios obtained from 89Zr-DFO-ZHER3:8698 PET images and HER3 protein expression per control and AUY922-treated MCF-7 xenografts. Fig. S16. HER3 intra-tumoral heterogeneity highlighted by histopathological analysis of control and AUY922-treated MCF-7 xenografts. Fig. S17. HER2-HER3 interaction in BT-474 and MCF-7 cells following AUY922 treatment. Fig. S18. Scheme illustrating the proposed effect of AUY922-induced Hsp90 inhibition in MCF-7 breast cancer xenografts. Table S1. Densitometric analysis of Western blots related to the treatment of BT-474, MCF-7, MCF-7 HER2+++ (-dox), and MCF-7 HER2+ (+dox) following 48 h treatment with AUY922 and PPP alone, or in combination. Table S2. Biodistribution results for 89Zr-DFO-ZHER3:8698 and 89Zr-DFO-ZTAQ (3 µg, 7.2-8.1 MBq/mouse) at 3 h after injection. Table S3. Biodistribution results for 89Zr-DFO-ZHER3:8698 at 3 h and 24 h after injection in MCF-7 and MDA-MB-468 tumour-bearing mice. Table S4. Tumour/organ ratios for 89Zr-DFO-ZHER3:8698 at 3 h and 24 h after injection in MCF-7 and MDA-MB-468 tumour-bearing mice. Table S5. HER3 and IGF1R co-occurrence in breast invasive carcinoma samples. Table S6. HER3 and IGF1R alterations lead to a shorter overall survival in breast invasive carcinoma samples. Table S7. HER3 and IGF1R alterations lead to a shorter disease free survival in breast invasive carcinoma samples. Table S8. HER3 and IGF1R co-occurrence in HER2 up-regulated breast invasive carcinoma samples.

In head and neck squamous cell cancer, the human epidermal growth factor receptor 1 (EGFR) is the dominant signaling molecule among all members of the family. So far, cetuximab is the only approved anti-EGFR monoclonal antibody used for the treatment of head and neck squamous cell cancer, but despite the benefits of adding it to standard treatment regimens, attempts to define a predictive biomarker to stratify patients for cetuximab treatment have been unsuccessful. We hypothesized that imaging with EGFR-specific radioligands may facilitate noninvasive measurement of EGFR expression across the entire tumor burden and allow for dynamic monitoring of cetuximab-mediated changes in receptor expression. Methods: EGFR-specific Affibody molecule (ZEGFR:03115) was radiolabeled with 89Zr and 18F. The radioligands were characterized in vitro and in mice bearing subcutaneous tumors with varying levels of EGFR expression. The protein dose for imaging studies was assessed by injecting 89Zr-deferoxamine-ZEGFR:03115 (2.4–3.6 MBq, 2 μg) either together with or 30 min after increasing amounts of unlabeled ZEGFR:03115 (1, 5, 10, 15, and 20 μg). PET images were acquired at 3, 24, and 48 h after injection, and the image quantification data were correlated with the biodistribution results. The EGFR expression and biodistribution of the tracer were assessed ex vivo by immunohistochemistry, Western blot, and autoradiography. To downregulate the EGFR level, treatment with cetuximab was performed, and 18F-aluminium fluoride-NOTA-ZEGFR:03115 (12 μg, 1.5–2 MBq/mouse) was used to monitor receptor changes. Results: In vivo studies demonstrated that coinjecting 10 μg of nonlabeled molecules with 89Zr-deferoxamine-ZEGFR:03115 allows for clear tumor visualization 3 h after injection. The radioconjugate tumor accumulation was EGFR-specific, and PET imaging data showed a clear differentiation between xenografts with varying EGFR expression levels. A strong correlation was observed between PET analysis, ex vivo estimates of tracer concentration, and receptor expression in tumor tissues. Additionally, 18F-aluminium fluoride-NOTA-ZEGFR:03115 could measure receptor downregulation in response to EGFR inhibition. Conclusion: ZEGFR:03115-based radioconjugates can assess different levels of EGFR level in vivo and measure receptor expression changes in response to cetuximab, indicating a potential for assessment of adequate treatment dosing with anti-EGFR antibodies.

The human epidermal growth factor receptor 3 (HER3) is overexpressed in several cancers, being linked to a more resistant phenotype and hence leading to poor patient prognosis. Imaging HER3 is challenging owing to the modest receptor number (50000 receptors/cell) in overexpressing cancer cells. Therefore, to image HER3 in vivo, high target affinity PET probes need to be developed. This work describes two different [(18)F]AlF radiolabeling strategies of the ZHER3:8698 affibody molecule specifically targeting HER3. The one-pot radiolabeling of ZHER3:8698 performed at 100 °C and using 1,4,7-triazanonane-1,4,7-triacetate (NOTA) as chelator resulted in radiolabeled products with variable purity attributed to radioconjugate thermolysis. An alternative approach based on the inverse electron demand Diels-Alder (IEDDA) reaction between a novel tetrazine functionalized 1,4,7-triazacyclononane-1,4-diacetate (NODA) chelator and the trans-cyclooctene (TCO) functionalized affibody molecule was also investigated. This method enabled the radiolabeling of the protein at room temperature. The [(18)F]AlF-NOTA-ZHER3:8698 and [(18)F]AlF-NODA-ZHER3:8698 conjugates showed a specific uptake at 1 h after injection in high HER3-expressing MCF-7 tumors of 4.36 ± 0.92% ID/g and 4.96 ± 0.65% ID/g, respectively. The current results are encouraging for further investigation of [(18)F]AlF-NOTA-ZHER3:8698 as a HER3 imaging agent.

Although radiotherapy is used to treat more than 50% of all cancer patients, in glioblastomas the percentage of success is limited due to the radioresistance of glioma cells. Reports have shown that part of this phenomenon has to be attributed to the deregulation of the PI3K/mTOR pathway (AC Begg, Nat Rev, 2011). Furthermore, p110α isoform specific PI3K inhibitors produced additive cytotoxic effects in combination with radiation therapy in in vitro and in vivo glioblastoma models (Chen JS et al. MCT. 2008). Based on this, we have decided to study if the treatment with the dual PI3K/mTOR inhibitor NVP-BEZ235 potentiates the effects of the irradiation and whether the combination would result in metabolic changes that can be evaluated by MRS and hence may be utilized as non-invasive biomarkers for the detection of response to combination therapy during early stage clinical trials in children with glioma. For this purpose we treated the paediatric high-grade glioma SF188 cell line with a low dose of X-ray irradiation (5 Gy) and NVP-BEZ235 (2xGI50, 28nM) both as single treatments and in combination. Our results showed a higher decrease in the number of treated cells with the combination (P MRS spectra from NVP-BEZ235 treated cells showed a significant (P As expected, we observed inhibition of the PI3K/mTOR pathway. Protein expression levels of pAKT (Ser473) and pS6RP (Ser240/244) in NVP-BEZ235 and combination treated cells were decreased. Irradiation induced-apoptosis was detected by increased levels of cleaved PARP in cells treated with X-ray or combination but not with NVP-BEZ235 alone. We also explored the causes of metabolic changes detected by MRS. Both in the NVP-BEZ235 and combination treatments, the decrease in PC levels was associated with a decrease in the expression of ChoKα, the enzyme responsible for choline phosphorylation into PC. Furthermore, a decrease in the levels of the glycolytic enzymes HKII and LDH-A was detected following NVP-BEZ235 treatment and the combination. These enzymes were not affected by X-ray alone. We have shown that inhibition of the PI3K/mTOR pathway increases the cytotoxic activity of the irradiation in paediatric glioblastoma. MRS allows monitoring of changes occurring during the combination treatment, suggesting that PC and Lac may be used as non-invasive biomarkers to detect response to PI3K/mTOR inhibition in combination with radiotherapy. Citation Format: Alice Agliano, Geetha Balaragah, Daniela M. Ciobota, Florence l. Raynaud, Paul A. Clarke, Chris Jones, Paul Workman, Andrew D. Pearson, Martin O. Leach, Nada M.S. Al-Saffar. Inhibition of the PI3K/mTOR pathway potentiates irradiation effects in paediatric glioblastoma inducing metabolic alterations detected by MRS. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5399. doi:10.1158/1538-7445.AM2013-5399