Detection of Lipid-Rich Prostate Circulating Tumour Cells with Coherent Anti-Stokes Raman Scattering Microscopy

Abstract

BackgroundCirculating tumour cells (CTC) are an important indicator of metastasis and associated with a poor prognosis. Detection sensitivity and specificity of CTC in the peripheral blood of metastatic cancer patient remain a technical challenge.MethodsCoherent anti-Stokes Raman scattering (CARS) microscopy was employed to examine the lipid content of CTC isolated from the peripheral blood of metastatic prostate cancer patients. CARS microscopy was also employed to evaluate lipid uptake and mobilization kinetics of a metastatic human prostate cancer cell line.ResultsOne hundred CTC from eight metastatic prostate cancer patients exhibited strong CARS signal which arose from intracellular lipid. In contrast, leukocytes exhibited weak CARS signal which arose mostly from cellular membrane. On average, CARS signal intensity of prostate CTC was 7-fold higher than that of leukocytes (P<0.0000001). When incubated with human plasma, C4-2 metastatic human prostate cancer cells exhibited rapid lipid uptake kinetics and slow lipid mobilization kinetics. Higher expression of lipid transport proteins in C4-2 cells compared to non-transformed RWPE-1 and non-malignant BPH-1 prostate epithelial cells further indicated strong affinity for lipid of metastatic prostate cancer cells.ConclusionsIntracellular lipid could serve as a biomarker for prostate CTC which could be sensitively detected with CARS microscopy in a label-free manner. Strong affinity for lipid by metastatic prostate cancer cells could be used to improve detection sensitivity and therapeutic targeting of prostate CTC.

Androgen control of lipid metabolism in prostate cancer: novel insights and future applications

“…These mobile lipids largely correspond to phosphatidylcholine and particularly triglycerides and cholesterol esters found in cellular deposits now known as lipid droplets. Accumulation of lipid droplets has also been demonstrated by other methods including histological staining and Raman spectromicroscopy in more aggressive clinical prostate tumors and metastatic deposits (Yue et al 2014), and in circulating prostate tumor cells (CTCs) (Mitra et al 2012). While altered lipid metabolism is acknowledged as a hallmark of many cancers, until relatively recently, it was commonly regarded as an epiphenomenon that accompanied tumorigenesis.…”

“…While most research attention has focused on the actions of androgens on de novo lipogenesis, AR signaling may also regulate cellular uptake of exogenous lipids by prostate cancer cells (Pinthus et al 2007, Liu et al 2010, Mitra et al 2012, Sacca et al 2012, Taylor et al 2015. These lipids can be derived from dietary lipoproteins in the circulation, which are hydrolyzed by lipoprotein lipase to free fatty acids, or be released by lipolysis from stores in local adipose tissue depots that comprises a major component of the tumor microenvironment (Ribeiro et al 2012).…”

Beyond the borders — Biomedical applications of non-linear Raman microscopy

“…CARS microscopy in the CH-stretch vibration region therefore also found use as a diagnostic tool to identify circulating tumor cells both in a mouse model [118] and in blood samples from prostate cancer patients [119]. In both cases, CARS microscopy was employed in a multimodal experiment, in which results from two photon fluorescence microscopy complemented the CARS microscopy data.…”

Coherent anti-Stokes Raman scattering for label-free biomedical imaging

“…biomedical studies evaluating steatosis and fibrosis in liver (83,86), progression of atherosclerosis in cardiac disease (80,87), demyelination of the central nervous system (CNS) (88,89), cancer classification (77,90) and assessing the pharmacodynamics, delivery and efficiency of therapeutic drugs (91,92). In subsequent sections we describe CARS studies in various biomedical areas.…”