Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy with dire prognosis due to aggressive biology, lack of effective tools for diagnosis at an early stage, and limited treatment options. Detection of PDAC using conventional radiographic imaging is limited by the dense, hypovascular stromal component and relatively scarce neoplastic cells within the tumor microenvironment (TME). The CC motif chemokine 2 (CCL2) and its cognate receptor CCR2 (CCL2/CCR2) axis are critical in fostering and maintaining this kind of TME by recruiting immunosuppressive myeloid cells such as the tumor-associated macrophages, thereby presenting an opportunity to exploit this axis for both diagnostic and therapeutic purposes. We engineered CCR2-targeting ultrasmall copper nanoparticles (Cu@CuO x ) as nanovehicles not only for targeted positron emission tomography imaging by intrinsic radiolabeling with 64 Cu but also for loading and delivery of the chemotherapy drug gemcitabine to PDAC. This 64 Cu-radiolabeled nanovehicle allowed sensitive and accurate detection of PDAC malignancy in autochthonous genetically engineered mouse models. The ultrasmall Cu@CuO x showed efficient renal clearance, favorable pharmacokinetics, and minimal in vivo toxicity. Systemic administration of gemcitabine-loaded Cu@CuO x effectively suppressed the progression of PDAC tumors in a syngeneic xenograft mouse model and prolonged survival. These CCR2-targeted ultrasmall nanoparticles offer a promising image-guided therapeutic agent and show great potential for translation.

Objective: vMIP-II (viral macrophage inflammatory protein 2)/vCCL2 (viral chemotactic cytokine ligand 2) binds to multiple chemokine receptors, and vMIP-II-based positron emission tomography tracer ( 64 Cu-DOTA-vMIP-II: vMIP-II tracer) accumulates at atherosclerotic lesions in mice. Given that it would be expected to react with multiple chemokine receptors on monocytes and macrophages, we wondered if its accumulation in atherosclerosis lesion-bearing mice might correlate with overall macrophage burden or, alternatively, the pace of monocyte recruitment. Approach and Results: We employed a mouse model of atherosclerosis regression involving adenoassociated virus 8 vector encoding murine Apoe (AAV-mApoE) treatment of Apoe −/− mice where the pace of monocyte recruitment slows before macrophage burden subsequently declines. Accumulation of 64 Cu-DOTA-vMIP-II at Apoe −/− plaque sites was strong but declined with AAV- mApoE -induced decline in monocyte recruitment, before macrophage burden reduced. Monocyte depletion indicated that monocytes and macrophages themselves were not the only target of the 64 Cu-DOTA-vMIP-II tracer. Using fluorescence-tagged vMIP-II tracer, competitive receptor blocking with CXCR4 antagonists, endothelial-specific Cre-mediated deletion of CXCR4, CXCR4-specific tracer 64 Cu-DOTA-FC131, and CXCR4 staining during disease progression and regression, we show endothelial cell expression of CXCR4 is a key target of 64 Cu-DOTA-vMIP-II imaging. Expression of CXCR4 was low in nonplaque areas but strongly detected on endothelium of progressing plaques, especially on proliferating endothelium, where vascular permeability was increased and monocyte recruitment was the strongest. Conclusions: Endothelial injury status of plaques is marked by CXCR4 expression and this injury correlates with the tendency of such plaques to recruit monocytes. Furthermore, our findings suggest positron emission tomography tracers that mark CXCR4 can be used translationally to monitor the state of plaque injury and monocyte recruitment.

Chemokines and chemokine receptors play an important role in the initiation and progression of atherosclerosis by mediating the trafficking of inflammatory cells. Chemokine receptor 5 (CCR5) has major implications in promoting the development of plaques to advanced stage and related vulnerability. CCR5 antagonist has demonstrated the effective inhibition of atherosclerotic progression in mice, making it a potential biomarker for atherosclerosis management. To accurately determine CCR5 in vivo, we synthesized CCR5 targeted Comb nanoparticles through a modular design and construction strategy with control over the physiochemical properties and functionalization of CCR5 targeting peptide D-Ala-peptide T-amide (DAPTA-Comb). In vivo pharmacokinetic evaluation through 64 Cu radiolabeling showed extended blood circulation of 64 Cu-DAPTA-Combs conjugated with 10%, 25%, and 40% DAPTA. The different organ distribution profiles of the three nanoparticles demonstrated the effect of DAPTA on not only physicochemical properties but also targeting efficiency. In vivo positron emission tomography/ computed tomography (PET/CT) imaging in an apolipoprotein E knockout mouse atherosclerosis model (ApoE −/− ) showed that the three 64 Cu-DAPTA-Combs could sensitively and specifically detect CCR5 along the progression of atherosclerotic lesions. In an ApoE-encoding adenoviral vector (AAV) induced plaque regression ApoE −/− mouse model, decreased monocyte recruitment, CD68+ macrophages, CCR5 expression, and plaque size were all associated with reduced PET signals, which not only further confirmed the targeting efficiency of 64 Cu-DAPTA-Combs but also highlighted the potential of these targeted nanoparticles for atherosclerosis imaging. Moreover, the up-regulation of CCR5 and colocalization with CD68+ macrophages in the necrotic core of ex vivo human plaque specimens warrant further investigation for atherosclerosis prognosis.

Diffuse intrinsic pontine glioma (DIPG) is an invasive pediatric brainstem malignancy exclusively in children without effective treatment due to the often-intact blood−brain tumor barrier (BBTB), an impediment to the delivery of therapeutics. Herein, we used focused ultrasound (FUS) to transiently open BBTB and delivered radiolabeled nanoclusters ( 64 Cu-CuNCs) to tumors for positron emission tomography (PET) imaging and quantification in a mouse DIPG model. First, we optimized FUS acoustic pressure to open the blood−brain barrier (BBB) for the effective delivery of 64 Cu-CuNCs to pons in wild-type mice. Then, the optimized FUS pressure was used to deliver radiolabeled agents in DIPG mouse. Magnetic resonance imaging (MRI)-guided FUS-induced BBTB opening was demonstrated using a low-molecular-weight, short-lived 68 Ga-DOTA-ECL1i radiotracer and PET/CT before and after treatment. We then compared the delivery efficiency of 64 Cu-CuNCs to DIPG tumor with and without FUS treatment and demonstrated the FUS-enhanced delivery and time-dependent diffusion of 64 Cu-CuNCs within the tumor.

Bronchiolitis obliterans syndrome (BOS) is a major impediment to lung transplant survival and is generally resistant to medical therapy. Extracorporeal photophoresis (ECP) is an immunomodulatory therapy that shows promise in stabilizing BOS patients, but its mechanisms of action are unclear. In a mouse lung transplant model, we show that ECP blunts alloimmune responses and inhibits BOS through lowering airway TGF-β bioavailability without altering its expression. Surprisingly, ECP-treated leukocytes were primarily engulfed by alveolar macrophages (AMs), which were reprogrammed to become less responsive to TGF-β and reduce TGF-β bioavailability through secretion of the TGF-β antagonist decorin. In untreated recipients, high airway TGF-β activity stimulated AMs to express CCL2, leading to CCR2 + monocyte-driven BOS development. Moreover, we found TGF-β receptor 2–dependent differentiation of CCR2 + monocytes was required for the generation of monocyte-derived AMs, which in turn promoted BOS by expanding tissue-resident memory CD8 + T cells that inflicted airway injury through Blimp-1–mediated granzyme B expression. Thus, through studying the effects of ECP, we have identified an AM functional plasticity that controls a TGF-β–dependent network that couples CCR2 + monocyte recruitment and differentiation to alloimmunity and BOS.