Necrosis avid near infrared fluorescent cyanines for imaging cell death and their use to monitor therapeutic efficacy in mouse tumor models

Abstract

Quantification of tumor necrosis in cancer patients is of diagnostic value as the amount of necrosis is correlated with disease prognosis and it could also be used to predict early efficacy of anti-cancer treatments. In the present study, we identified two near infrared fluorescent (NIRF) carboxylated cyanines, HQ5 and IRDye 800CW (800CW), which possess strong necrosis avidity. In vitro studies showed that both dyes selectively bind to cytoplasmic proteins of dead cells that have lost membrane integrity. Affinity for cytoplasmic proteins was confirmed using quantitative structure activity relations modeling. In vivo results, using NIRF and optoacoustic imaging, confirmed the necrosis avid properties of HQ5 and 800CW in a mouse 4T1 breast cancer tumor model of spontaneous necrosis. Finally, in a mouse EL4 lymphoma tumor model, already 24 h post chemotherapy, a significant increase in 800CW fluorescence intensity was observed in treated compared to untreated tumors. In conclusion, we show, for the first time, that the NIRF carboxylated cyanines HQ5 and 800CW possess strong necrosis avid properties in vitro and in vivo. When translated to the clinic, these dyes may be used for diagnostic or prognostic purposes and for monitoring in vivo tumor response early after the start of treatment.

Optoacoustic Detection of Early Therapy-Induced Tumor Cell Death Using a Targeted Imaging Agent

“…Cell death, whether by apoptosis or necrosis, has attracted considerable attention as an imaging target as it is a generic marker for the presence of disease and additionally, in the case of cancer, a marker of response to treatment (4,29). A number of cell death imaging agents have been developed, with some interacting with intracellular targets, such as CC3 (30), cytosolic proteins (31,32), and the mitochondrial membrane potential (33); or with extracellular targets, including exposed extracellular DNA (34), histones (35) and plasma membrane phospholipids (6,36). Plasma membrane phospholipids, such as PS and phosphatidylethanolamine (PE), which are normally present on the inner leaflet of the plasma membrane bilayer, are exposed on the surface of apoptotic cells and in necrotic cells by permeabilization of the plasma membrane to the imaging agent (37,38).…”

The Necrosis-Avid Small Molecule HQ4-DTPA as a Multimodal Imaging Agent for Monitoring Radiation Therapy-Induced Tumor Cell Death

“…The NIRF properties of carboxylated cyanine HQ4-DTPA and its radioactive labeled variant [ 111 In]DTPA-HQ4 have been previously demonstrated by our group ( 38 ). Although nuclear imaging overcomes the limited tissue penetration depth of NIRF imaging ( 40 , 52 ), it has its drawbacks, including radiation safety, cost of radioactive materials, limited temporal sensitivity, and the lack of anatomical detail ( 53 ). Photoacoustic imaging overcomes such limitations and offers a novel and clinically relevant means of imaging HQ4-DTPA in vivo .…”

Advanced optoacoustic methods for multiscale imaging of in vivo dynamics

“…In fact, some therapeutic approaches that are initially designed for inducing apoptosis may often result in the so-called secondary necrosis. An approach to assess the amount of necrosis during tumour progression or therapy is based on near infrared fluorescent carboxylated cyanine dyes with strong necrosis avidity [319]. By using non-invasive MSOT imaging in a mouse model, these dyes have been shown to accumulate in the deoxy-haemoglobin-rich tumour core (Fig.…”

“…(d) Multispectral optoacoustic tomography (MSOT) images of spontaneous 4T1-luc2 tumour necrosis with the carboxylated cyanine HQ5. Adapted with permission from [319]. © 2015 Impact Journals.…”