Human epidermal growth factor receptor 2 (HER2) status is one of the major tumor characteristics in breast cancer to guide therapy. Anti-HER2 treatment has clear survival advantages in HER2-positive breast carcinoma patients. Heterogeneity in HER2 expression between primary tumor and metastasis has repeatedly been described, resulting in the need to reassess HER2 status during the disease course. To avoid repeated biopsy with potential bias due to tumor heterogeneity, Nanobodies directed against HER2 have been developed as probes for molecular imaging. Nanobodies, which are derived from unique heavy-chain-only antibodies, are the smallest antigen-binding antibody fragments and have ideal characteristics for PET imaging. The primary aims were assessment of safety, biodistribution, and dosimetry. The secondary aim was to investigate tumor-targeting potential. Methods: In total, 20 women with primary or metastatic breast carcinoma (score of 2+ or 3+ on HER2 immunohistochemical assessment) were included. Anti-HER2-Nanobody was labeled with ⁶⁸Ga via a NOTA derivative. Administered activities were 53–174 MBq (average, 107 MBq). PET/CT scans for dosimetry assessment were obtained at 10, 60, and 90 min after administration. Physical evaluation and blood analysis were performed for safety evaluation. Biodistribution was analyzed for 11 organs using MIM software; dosimetry was assessed using OLINDA/EXM. Tumor-targeting potential was assessed in primary and metastatic lesions. Results: No adverse reactions occurred. A fast blood clearance was observed, with only 10% of injected activity remaining in the blood at 1 h after injection. Uptake was seen mainly in the kidneys, liver, and intestines. The effective dose was 0.043 mSv/MBq, resulting in an average of 4.6 mSv per patient. The critical organ was the urinary bladder wall, with a dose of 0.406 mGy/MBq. In patients with metastatic disease, tracer accumulation well above the background level was demonstrated in most identified sites of disease. Primary lesions were more variable in tracer accumulation. Conclusion: ⁶⁸Ga-HER2-Nanobody PET/CT is a safe procedure with a radiation dose comparable to other routinely used PET tracers. Its biodistribution is favorable, with the highest uptake in the kidneys, liver, and intestines but very low background levels in all other organs that typically house primary breast carcinoma or tumor metastasis. Tracer accumulation in HER2-positive metastases is high, compared with normal surrounding tissues, and warrants further assessment in a phase II trial.

Camelidae possess an unusual class of antibodies devoid of light chains. Nanobodies are intact antigen-binding fragments that are stable, easily generated against different targets, and fully functional. Their rapid clearance from the blood circulation favors their use as imaging agents. We compared the in vivo tumor uptake and biodistribution of 2 anti–epidermal growth factor receptor (anti-EGFR) Nanobodies, ^99mTc-7C12 and ^99mTc-7D12. Methods: Nanobodies were labeled via their hexahistidine tail with ^99mTc-tricarbonyl (^99mTc(CO)₃) generated from a kit. Mice bearing subcutaneous A431 (EGFR-positive) and R1M (EGFR-negative) xenografts were intravenously injected with ^99mTc-7C12 and ^99mTc-7D12 on separate days. Pinhole SPECT/micro-CT images were acquired at 1 h after administration to assess noninvasively the biodistribution and tumor targeting of the labeled compounds. Pinhole SPECT and micro-CT images from the same mouse were automatically fused on the basis of a mathematic rigid-body-transformation algorithm using six ⁵⁷Co sources. Images were quantified, and tracer uptake was expressed as percentage injected activity per gram per cubic centimeter (%IA/cm³) of tissue. Ex vivo biodistribution of mice bearing A431 injected with either ^99mTc-7C12 or ^99mTc-7D12 was also assessed; activity in the tumor and organs was recorded and expressed as percentage injected activity per gram (%IA/g). Results: Binding of both tracers was receptor-specific. Image analysis showed high and similar tumor uptake values for both ^99mTc-7C12 and ^99mTc-7D12 (4.55 ± 0.24 %IA/cm³ and 4.62 ± 0.36 %IA/cm³, respectively) in A431 xenografts, whereas the uptake in the negative tumor (R1M) was low (1.16 ± 0.14 for ^99mTc-7C12 and 1.49 ± 0.60 for ^99mTc-7D12). ^99mTc-7C12 showed significantly higher kidney uptake (63.48 ± 2.36 vs. 56.25 ± 2.46 %IA/cm³) and lower liver uptake (2.55 ± 0.26 vs. 4.88 ± 0.86 %IA/cm³) than did ^99mTc-7D12. The ex vivo analysis confirmed the image quantification with high tumor-to-background ratio; however, ^99mTc-7C12 showed higher tumor uptake (9.11 ± 1.12 %IA/g) than did ^99mTc-7D12 (6.09 ± 0.77 %IA/g). ^99mTc-7D12 demonstrated significantly higher blood activity than did ^99mTc-7C12, but both showed short plasma half-lives (<10 min).Conclusion: The Nanobody fragments used here show high tumor uptake, low liver uptake, and rapid blood clearance. Nanobodies are promising probes for noninvasive radioimmunodetection of specific targets early after administration. On the basis of its favorable biodistribution, ^99mTc-7C12 was selected for further studies.

In single photon emission computed tomography, the choice of the collimator has a major impact on the sensitivity and resolution of the system. Traditional parallel‐hole and fan‐beam collimators used in clinical practice, for example, have a relatively poor sensitivity and subcentimeter spatial resolution, while in small‐animal imaging, pinhole collimators are used to obtain submillimeter resolution and multiple pinholes are often combined to increase sensitivity. This paper reviews methods for production, sensitivity maximization, and task‐based optimization of collimation for both clinical and preclinical imaging applications. New opportunities for improved collimation are now arising primarily because of (i) new collimator‐production techniques and (ii) detectors with improved intrinsic spatial resolution that have recently become available. These new technologies are expected to impact the design of collimators in the future. The authors also discuss concepts like septal penetration, high‐resolution applications, multiplexing, sampling completeness, and adaptive systems, and the authors conclude with an example of an optimization study for a parallel‐hole, fan‐beam, cone‐beam, and multiple‐pinhole collimator for different applications.

Preoperative radiotherapy (RT) is a mainstay in the management of rectal cancer, a tumor characterized by desmoplastic stroma containing cancer-associated fibroblasts (CAF). Although CAFs are abundantly present, the effects of RT to CAF and its impact on cancer cells are unknown. We evaluated the damage responses of CAF to RT and investigated changes in colorectal cancer cell growth, transcriptome, metabolome, and kinome in response to paracrine signals emerging from irradiated CAF. RT to CAF induced DNA damage, p53 activation, cell-cycle arrest, and secretion of paracrine mediators, including insulin-like growth factor-1 (IGF1). Subsequently, RT-activated CAFs promoted survival of colorectal cancer cells, as well as a metabolic switch favoring glutamine consumption through IGF1 receptor (IGF1R) activation. RT followed by IGF1R neutralization in orthotopic colorectal cancer models reduced the number of mice with organ metastases. Activation of the downstream IGF1R mediator mTOR was significantly higher in matched (intrapatient) samples and in unmatched (interpatient) samples from rectal cancer patients after neoadjuvant chemoradiotherapy. Taken together, our data support the notion that paracrine IGF1/IGF1R signaling initiated by RT-activated CAF worsens colorectal cancer progression, establishing a preclinical rationale to target this activation loop to further improve clinical responses and patient survival. Significance: These findings reveal that paracrine IGF1/IGF1R signaling promotes colorectal cancer progression, establishing a preclinical rationale to target this activation loop. Cancer Res; 78(3); 659–70. ©2017 AACR.

Increasing evidence supports the critical roles played by adipose tissue in breast cancer progression. Yet, the mediators and mechanisms are poorly understood. Here, we show that breast cancer–associated adipose tissue from freshly isolated tumors promotes F-actin remodeling, cellular scattering, invasiveness, and spheroid reorganization of cultured breast cancer cells. A combination of techniques, including transcriptomics, proteomics, and kinomics enabled us to identify paracrine secretion of oncostatin M (OSM) by cancer-associated adipose tissue. Specifically, OSM, expressed by CD45+ leucocytes in the stromal vascular fraction, induced phosphorylation of STAT3 (pSTAT3-) Y705 and S727 in breast cancer cells and transcription of several STAT3-dependent genes, including S100 family members S100A7, S100A8, and S100A9. Autocrine activation of STAT3 in MCF-7 cells ectopically expressing OSM-induced cellular scattering and peritumoral neovascularization of orthotopic xenografts. Conversely, selective inhibition of OSM by neutralizing antibody and Jak family kinases by tofacitinib inhibited STAT3 signaling, peritumoral angiogenesis, and cellular scattering. Importantly, nuclear staining of pSTAT3-Y705 identified at the tumor invasion front in ductal breast carcinomas correlates with increased lymphovascular invasion. Our work reveals the potential of novel therapeutic strategies targeting the OSM and STAT3 axis in patients with breast cancer harboring nuclear pSTAT3-Y705. Cancer Res; 74(23); 6806–19. ©2014 AACR.