Linear Desferrichrome-Linked Silicon-Rhodamine Antibody Conjugate Enables Targeted Multimodal Imaging of HER2 in Vitro and in Vivo.

We report the nuclear and optical in vitro and in vivo imaging of SKOV-3 cells by targeting HER2 with a bimodal trastuzumab conjugate. Previously, we have shown that desferrichrome derivatives provide a robust and versatile radiolabeling platform for the radioisotope zirconium-89. Here, we appended silicon-rhodamine functionalized linear desferrichrome to trastuzumab. This construct was radiolabeled and used to image cellular binding and antibody uptake in vitro and in vivo. The robust extinction coefficient of the SiR deep-red emissive fluorophore enables direct quantification of the number of appended chelators and fluorophore molecules per antibody. Subsequent radiolabeling of the multifunctional immunoconjugate with 89Zr was achieved with a 64 ± 9% radiochemical yield, while the reference immunoconjugate desferrioxamine (DFO)-trastuzumab exhibited a yield of 84 ± 9%. In vivo PET imaging (24, 48, 72, and 96 h post injection) and biodistribution experiments (96 h post injection) in HER2+ tumor bearing mice revealed no statistically significant difference of the two 89Zr-labeled conjugates at each time point evaluated. The bimodal conjugate permitted successful in vivo fluorescence imaging (96 h post injection) and subsequent fluorescence-guided, surgical resection of the tumor mass. This report details the first successful application of a fluorophore-functionalized desferrichrome derivative for targeted imaging, motivating further development and application of this scaffold as a multimodal imaging platform.

Targeting the Hemopexin-like Domain of Latent Matrix Metalloproteinase-9 (proMMP-9) with a Small Molecule Inhibitor Prevents the Formation of Focal Adhesion Junctions.

A lack of target specificity has greatly hindered the success of inhibitor development against matrix metalloproteinases (MMPs) for the treatment of various cancers. The MMP catalytic domains are highly conserved, whereas the hemopexin-like domains of MMPs are unique to each family member. The hemopexin-like domain of MMP-9 enhances cancer cell migration through self-interaction and heterointeractions with cell surface proteins including CD44 and α4ß1 integrin. These interactions activate EGFR-MAP kinase dependent signaling that leads to cell migration. In this work, we generated a library of compounds, based on hit molecule N-[4-(difluoromethoxy)phenyl]-2-[(4-oxo-6-propyl-1H-pyrimidin-2-yl)sulfanyl]-acetamide, that target the hemopexin-like domain of MMP-9. We identify N-(4-fluorophenyl)-4-(4-oxo-3,4,5,6,7,8-hexahydroquinazolin-2-ylthio)butanamide, 3c, as a potent lead (Kd = 320 nM) that is specific for binding to the proMMP-9 hemopexin-like domain. We demonstrate that 3c disruption of MMP-9 homodimerization prevents association of proMMP-9 with both α4ß1 integrin and CD44 and results in the dissociation of EGFR. This disruption results in decreased phosphorylation of Src and its downstream target proteins focal adhesion kinase (FAK) and paxillin (PAX), which are implicated in promoting tumor cell growth, migration, and invasion. Using a chicken chorioallantoic membrane in vivo assay, we demonstrate that 500 nM 3c blocks cancer cell invasion of the basement membrane and reduces angiogenesis. In conclusion, we present a mechanism of action for 3c whereby targeting the hemopexin domain results in decreased cancer cell migration through simultaneous disruption of α4ß1 integrin and EGFR signaling pathways, thereby preventing signaling bypass. Targeting through the hemopexin-like domain is a powerful approach to antimetastatic drug development.

A Novel Collagen Dot Assay for Monitoring Cancer Cell Migration.

Cell migration is a critical determinant of cancer invasion and metastasis. Drugs targeting cancer cell migration have been hindered due to the lack of effective assays for monitoring cancer cell migration. Here we describe a novel method to microscopically monitor cell migration in a quantitative fashion. This assay can be used to study genes involved in cancer cell migration, as well as screening anticancer drugs that target this cellular process.