MRI Detection of Lymph Node Metastasis through Molecular Targeting of C-C Chemokine Receptor Type 2 and Monocyte Hitchhiking

Biopsy is the clinical standard for diagnosing lymph node (LN) metastasis, but it is invasive and poses significant risk to patient health. Magnetic resonance imaging (MRI) has been utilized as a noninvasive alternative but is limited by low sensitivity, with only ∼35% of LN metastases detected, as clinical contrast agents cannot discriminate between healthy and metastatic LNs due to nonspecific accumulation. Nanoparticles targeted to the C-C chemokine receptor 2 (CCR2), a biomarker highly expressed in metastatic LNs, have the potential to guide the delivery of contrast agents, improving the sensitivity of MRI. Additionally, cancer cells in metastatic LNs produce monocyte chemotactic protein 1 (MCP1), which binds to CCR2+ inflammatory monocytes and stimulates their migration. Thus, the molecular targeting of CCR2 may enable nanoparticle hitchhiking onto monocytes, providing an additional mechanism for metastatic LN targeting and early detection. Hence, we developed micelles incorporating gadolinium (Gd) and peptides derived from the CCR2-binding motif of MCP1 (MCP1-Gd) and evaluated the potential of MCP1-Gd to detect LN metastasis. When incubated with migrating monocytes in vitro, MCP1-Gd transport across lymphatic endothelium increased 2-fold relative to nontargeting controls. After administration into mouse models with initial LN metastasis and recurrent LN metastasis, MCP1-Gd detected metastatic LNs by increasing MRI signal by 30-50% relative to healthy LNs. Furthermore, LN targeting was dependent on monocyte hitchhiking, as monocyte depletion decreased accumulation by >70%. Herein, we present a nanoparticle contrast agent for MRI detection of LN metastasis mediated by CCR2-targeting and demonstrate the potential of monocyte hitchhiking for enhanced nanoparticle delivery.

Spotlight on Genetic Kidney Diseases: A Call for Drug Delivery and Nanomedicine Solutions

Nanoparticles as drug delivery carriers have benefited diseases, including cancer, since the 1990s, and more recently, their promise to quickly and efficiently be mobilized to fight against global diseases such as in the COVID-19 pandemic have been proven. Despite these success stories, there are limited nanomedicine efforts for chronic kidney diseases (CKDs), which affect 844 million people worldwide and can be linked to a variety of genetic kidney diseases. In this Perspective, we provide a brief overview of the clinical status of genetic kidney diseases, background on kidney physiology and a summary of nanoparticle design that enable kidney access and targeting, and emerging technological strategies that can be applied for genetic kidney diseases, including rare and congenital kidney diseases. Finally, we conclude by discussing gaps in knowledge remaining in both genetic kidney diseases and kidney nanomedicine and collective efforts that are needed to bring together stakeholders from diverse expertise and industries to enable the development of the most relevant drug delivery strategies that can make an impact in the clinic.

CD70-Targeted Micelles Enhance HIF2α siRNA Delivery and Inhibit Oncogenic Functions in Patient-Derived Clear Cell Renal Carcinoma Cells

The majority of clear cell renal cell carcinomas (ccRCCs) are characterized by mutations in the Von Hippel−Lindau (VHL) tumor suppressor gene, which leads to the stabilization and accumulation of the HIF2α transcription factor that upregulates key oncogenic pathways that promote glucose metabolism, cell cycle progression, angiogenesis, and cell migration. Although FDA-approved HIF2α inhibitors for treating VHL disease-related ccRCC are available, these therapies are associated with significant toxicities such as anemia and hypoxia. To improve ccRCC-specific drug delivery, peptide amphiphile micelles (PAMs) were synthesized incorporating peptides targeted to the CD70 marker expressed by ccRCs and anti-HIF2α siRNA, and the ability of HIF2α-CD27 PAMs to modulate HIF2α and its downstream targets was evaluated in human ccRCC patient-derived cells. Cell cultures were derived from eight human ccRCC tumors and the baseline mRNA expression of HIF2A and CD70, as well as the HIF2α target genes SLC2A1, CCND1, VEGFA, CXCR4, and CXCL12 were first determined. As expected, each gene was overexpressed by at least 63% of all samples compared to normal kidney proximal tubule cells. Upon incubation with HIF2α-CD27 PAMs, a 50% increase in ccRCC-binding was observed upon incorporation of a CD70-targeting peptide into the PAMs, and gel shift assays demonstrated the rapid release of siRNA (>80% in 1 h) under intracellular glutathione concentrations, which contributed to ~70% gene knockdown of HIF2α and its downstream genes. Further studies demonstrated that knockdown of the HIF2α target genes SLC2A1, CCND1, VEGFA, CXCR4, and CXCL12 led to inhibition of their oncogenic functions of glucose transport, cell proliferation, angiogenic factor release, and cell migration by 50−80%. Herein, the development of a nanotherapeutic strategy for ccRCC-specific siRNA delivery and its potential to interfere with key oncogenic pathways is presented.

Abstract 511: Intrinsic Self-reactive T Cells To ApoB-100 Peptide P210 In Acute Coronary Syndrome Patients Are Associated With T Effector/Memory Response

Background: Antibodies to the apoB-100 peptide P210 have been reported in coronary artery disease (CAD) patients yet the nature of intrinsic self-reactive T cell response in these patients remains to be investigated. Given the reported presence of antibodies to P210 in CAD, we hypothesized that the P210 peptide would provoke T cell activation in peripheral blood mononuclear cells (PBMCs) of acute coronary syndrome (ACS) patients and would manifest as T Effector/Memory cells, previously demonstrated to correlate with atherosclerotic disease.

Methods and Results: PBMCs from ACS patients were collected under an approved IRB and kept viable in cryo-preservation until assays. Cryo-preserved viable PBMCs from self-reported controls were purchased from a commercial vendor with their own IRB. T cell activation was assessed by stimulating PBMCs in vitro for 16 hours with P210 peptide. Negative control was no treatment and positive controls were stimulation with pooled CMV peptides or PMA/ionomycin cocktail. The Activation Induced Marker (AIM) flow cytometric assay was performed with the following antibodies: CD4, CD8, CD25, CD69, CD134, CD137, and CD154 using non-viable cells and CD14, CD16 and CD19 as dump gates. AIM+ cells were expressed as the ratio relative to no stimulation. T Effector/Memory responses were assessed after 72 hours of stimulation with P210. Negative control was no stimulation and positive control was stimulation with PMA/ionomycin. Viable T Effector/Memory cells were identified as positive for CD3, CD4, CD8, and CD45RO, but CD45RA(-), CD62L(-) and CCR7(-) by flow cytometry. T Effector/Memory cells were expressed as Response Index (negative control subtracted from P210 stimulation divided by the positive control for each sample). P210 stimulation significantly increased CD4+CD69+CD134+ (AIM+) cells in ACS (P<0.05; n=12) compared to controls (N=6). No other AIM+ cells were noted. P210 stimulation induced persistent CD8+ T Effector and T Effector Memory responses in ACS (N=13; P<0.05) compared to controls (N=14).

Conclusion: P210 provokes self-reactive T cell activation and Effector/Memory responses in ACS patients consistent with the immunogenic role of P210 in coronary artery disease pathophysiology.

Abstract 510: Immune-regulatory Mechanism Of P210-complexed Nanoparticle Immunization For Atherosclerosis

Background: The use of nanoparticles for efficient delivery of therapeutic modalities in humans is rapidly increasing. We have previously reported that a nanovaccine consisting of apoB-100 peptide P210 complexed with amphiphilic micelles (P210-PAM) significantly reduces atherosclerosis in apoE-/- mice. In this study, we defined the mechanistic pathway for the atheroprotective effect of P210-PAM.

Methods and Results: Seven-week male apoE-/- mice were immunized with P210-PAM or mouse serum albumin peptide amphiphile micelles (MSA-PAM) at a dose of 100ug per injection at 7, 10, and 12 weeks of age. One week after the second booster, mice were euthanized and the splenocytes were collected for immune profiling and immune assays. A second group of immunized mice were injected with thioglycolate to elicit peritoneal macrophages. Splenocytes from P210-PAM mice collected 1 week after the second booster had significantly increased CD4+CD25+FoxP3+ Treg cells and CD8+CTLA-4+ T cells compared to MSA-PAM mice (N=9 each; P≤0.05). Splenocytes from P210-PAM mice had reduced CD4+ T cell proliferation and CD8+CD107a+ T cells in response to P210 recall compared to MSA-PAM (N=8 and 9, respectively; P<0.05). No effects were observed with non-specific PMA/ionomycin stimulation indicating antigen-specificity. Splenic mRNA expression of IL-1β was unchanged but there was significant reduction in IL-1R1, IL-6, and IL-17a in P210-PAM mice (N=12 each; P<0.05). Flow cytometric analysis indicated that the reduced IL-1R1 expression was specific to F4/80+ macrophages (N=10 each; P<0.05). Macrophages enriched from the peritoneal exudate showed significantly reduced iNOS, IL-6, IL-12 and IL-10 mRNA expression in P210-PAM mice compared to MSA-PAM (N=4 each; P<0.05).

Conclusion: The mechanism of the protective effect of P210-PAM nanoparticles in reducing the immune-inflammatory response in atherosclerosis is at the level of both adaptive T cell response as well as innate macrophage response. The use of P210-PAM in future investigations as potential clinical therapy for atherosclerosis is thus warranted.

Overcoming physiological barriers by nanoparticles for intravenous drug delivery to the lymph nodes

The lymph nodes are major sites of cancer metastasis and immune activity, and thus represent important clinical targets. Although not as well-studied compared to subcutaneous administration, intravenous drug delivery is advantageous for lymph node delivery as it is commonly practiced in the clinic and has the potential to deliver therapeutics systemically to all lymph nodes. However, rapid clearance by the mononuclear phagocyte system, tight junctions of the blood vascular endothelium, and the collagenous matrix of the interstitium can limit the efficiency of lymph node drug delivery, which has prompted research into the design of nanoparticle-based drug delivery systems. In this mini review, we describe the physiological and biological barriers to lymph node targeting, how they inform nanoparticle design, and discuss the future outlook of lymph node targeting.

CCR2-targeted micelles for anti-cancer peptide delivery and immune stimulation

Signaling between the CC chemokine receptor 2 (CCR2) with its ligand, monocyte chemoattractant protein-1 (MCP-1) promotes cancer progression by directly stimulating tumor cell proliferation and downregulating the expression of apoptotic proteins. Additionally, the MCP-1/CCR2 signaling axis drives the migration of circulating monocytes into the tumor microenvironment, where they mature into tumor-associated macrophages (TAMs) that promote disease progression through induction of angiogenesis, tissue remodeling, and suppression of the cytotoxic T lymphocyte (CTL) response. In order to simultaneously disrupt MCP-1/CCR2 signaling and target CCR2-expressing cancer cells for drug delivery, KLAK-MCP-1 micelles consisting of a CCR2-targeting peptide sequence (MCP-1 peptide) and the apoptotic KLAKLAK peptide were synthesized. In vitro, KLAK-MCP-1 micelles were observed to bind and induce cytotoxicity to cancer cells through interaction with CCR2. In vivo, KLAK-MCP-1 micelles inhibited tumor growth (34 ± 11%) in a subcutaneous B16F10 murine melanoma model despite minimal tumor accumulation upon intravenous injection. Tumors treated with KLAK-MCP1 demonstrated reduced intratumor CCR2 expression and altered infiltration of TAMs and CTLs as evidenced by immunohistochemical and flow cytometric analysis. These studies highlight the potential application of CCR2-targeted nanotherapeutic micelles in cancer treatment.

Collagenase-Cleavable Peptide Amphiphile Micelles as a Novel Theranostic Strategy in Atherosclerosis

Atherosclerosis is an inflammatory disease characterized by plaques that can cause sudden myocardial infarction upon rupture. Such rupture-prone plaques have thin fibrous caps due to collagenase degradation, and a noninvasive diagnostic tool and targeted therapy that can identify and treat vulnerable plaques and may inhibit the onset of acute cardiac events. Toward this goal, monocyte-binding, collagenase-inhibiting, and gadolinium-modified peptide amphiphile micelles (MCG PAMs) are developed. Monocyte chemoattractant protein-1 (MCP-1) binds to C-C chemokine receptor-2 expressed on pathological cell types present within plaques. Through the peptide binding motif of MCP-1, MCG PAMs bind to monocytes and vascular smooth muscle cells in vitro. Moreover, using magnetic resonance imaging, MCG PAMs show enhanced targeting and successful detection of plaques in diseased mice in vivo and act as contrast agents for molecular imaging. Through the collagenase-cleaving peptide sequence of collagen [VPMS-MRGG], MCG PAMs can compete for collagenases that degrade the fibrous cap of plaques, providing therapy. MCG PAM-treated mice show increased fibrous cap thickness by 61% and 113% histologically compared to nontargeting micelle- or PBS-treated mice (p = 0.0075 and 0.001, respectively). Overall, this novel multimodal nanoparticle offers new theranostic opportunities for noninvasive diagnosis and treatment of atherosclerotic plaques.