Detection of Live Circulating Tumor Cells by a Class of Near-Infrared Heptamethine Carbocyanine Dyes in Patients with Localized and Metastatic Prostate Cancer

Abstract

Tumor cells are inherently heterogeneous and often exhibit diminished adhesion, resulting in the shedding of tumor cells into the circulation to form circulating tumor cells (CTCs). A fraction of these are live CTCs with potential of metastatic colonization whereas others are at various stages of apoptosis making them likely to be less relevant to understanding the disease. Isolation and characterization of live CTCs may augment information yielded by standard enumeration to help physicians to more accurately establish diagnosis, choose therapy, monitor response, and provide prognosis. We previously reported on a group of near-infrared (NIR) heptamethine carbocyanine dyes that are specifically and actively transported into live cancer cells. In this study, this viable tumor cell-specific behavior was utilized to detect live CTCs in prostate cancer patients. Peripheral blood mononuclear cells (PBMCs) from 40 patients with localized prostate cancer together with 5 patients with metastatic disease were stained with IR-783, the prototype heptamethine cyanine dye. Stained cells were subjected to flow cytometric analysis to identify live (NIR+) CTCs from the pool of total CTCs, which were identified by EpCAM staining. In patients with localized tumor, live CTC counts corresponded with total CTC numbers. Higher live CTC counts were seen in patients with larger tumors and those with more aggressive pathologic features including positive margins and/or lymph node invasion. Even higher CTC numbers (live and total) were detected in patients with metastatic disease. Live CTC counts declined when patients were receiving effective treatments, and conversely the counts tended to rise at the time of disease progression. Our study demonstrates the feasibility of applying of this staining technique to identify live CTCs, creating an opportunity for further molecular interrogation of a more biologically relevant CTC population.

Review on near-infrared heptamethine cyanine dyes as theranostic agents for tumor imaging, targeting, and photodynamic therapy

“…5,6,15,16,20,22 For example, Pz 247, a chiral porphyazine NIRF agent without chemical conjugation, show tumor-targeting property and exhibited preferential retention in the tumor cells of human breast tumor xenografts subcutaneously implanted in mice. 46 Heptamethine cyanine dyebased NIRF imaging is becoming an attractive modality for cancer detection with the acquisition of real-time pathophysiologic information.…”

“…At the cellular level, these NIRF agents also show preferential uptake in cancer cells but not normal cells, as demonstrated in many different types of cancer cells including cultured, circulating and disseminated tumor cells. 5,6,16 …”

“…19 The analysis of malignant tumor cells in splanchnocoele fluid by NIRF imaging has become a fast and reliable method to monitor disease progression in cancer patients. 6,47 In recent years, patientderived tumor xenograft (PDX) models established by transplanting human fresh tumor tissues into immunodeficient mice have become another valuable tool for maintaining intact tumor profiles, such as tumor heterogeneity. They can be used to screen and test anticancer drug efficacy tailored for individualized treatment.…”

“…Their considerable advantages for in vivo imaging include stronger ligand labeling, signal strength and tissue absorbance, a wider range of imaging materials for coupling, and less background fluorescence. [2][3][4] Several NIRF dyes have become commercially available, such as Cy5.5 5 and IRDye800-CW, 6 which have been coupled with peptides or antibodies and successfully used for targeted visualization of neoplastic cancers in animal models. Indocyanine green (ICG), the only NIRF agent approved by the FDA in the United States for medical diagnostic application, has been widely used to differentiate benign from the malignant diseases in the clinic.…”

“…14 Recently, a group of NIRF heptamethine cyanine dyes have emerged as more promising tools for cancer imaging and targeted therapy. These agents are heterocyclic polymethine cyanines with dual imaging and targeting properties, including IR-780, 5 IR-783, 6 IR-808, 15 and MHI-148. 16 They have demonstrated preferential accumulation and retention indifferent types of cancer cells (Table 1), with increased uptake in the mitochondria and lysosomes, but no accumulation in normal cells, enabling cancer-specific targeting without the need for chemical conjugation.…”