Label-free identification and characterization of living human primary and secondary tumour cells

Abstract

We used three label-free minimally invasive methods to characterize individual cells derived from primary and secondary tumours from the same patient, and of the same type – colorectal. Raman spectroscopy distinguished cells by their biochemical 'fingerprint' in a vibrational spectrum with 100% accuracy, and revealed that the primary cell line contains more lipids and alpha-helix proteins, whereas the secondary cell line contains more porphyrins and beta-sheet proteins. Stimulated Raman scattering (SRS) microscopy distinguished cells in chemically-specific images of CH2 bonds which revealed lipid droplets in secondary tumour cells. Atomic force microscopy (AFM) was used to distinguish cells with 80% accuracy by measuring their elasticity – secondary tumour cells (SW620) are around 3 times softer than primary ones (SW480). As well as characterizing the physical and biochemical differences between cell lines in vitro, these techniques offer three novel methods which could potentially be used for diagnosis – to assign a tumour as primary or secondary.

Biochemical fingerprint of colorectal cancer cell lines using label‐free live single‐cell Raman spectroscopy

“…The –CH 2 and –CH 3 stretching contributions in the region of 2,800–3,200 cm −1 showed higher overall intensity for SW480 cells and a greater CH 2 : CH 3 ratio for SW620 cells, indicating differences in lipid composition between the two cell lines with higher lipid content for the larger size cells SW480 (SW480 diameter = 16.9 ± 0.4 μm cf. SW620 diameter = 14.4 ± 0.3 μm) and in agreement with previous reports on fixed SW480/SW620 cells . The fits of these peaks are shown in Figure S3a and S3b.…”

“…Peaks at around 1,128; 1,310; and 1,585 cm −1 have previously been labelled as cytochrome C resonance and can be used to monitor early signs of apoptosis . Peaks at 1,157; 1,517; 1,525; and 1,620 cm −1 reveal higher contributions of double bonds to the SW620 normalized spectra and have previously been reported as cancer biomarkers in different biological samples, assigning them to carotenoids or porphyrins …”

“…Using these cell lines can help isolate metastasis variability from the person‐to‐person variation. Previous reports of vibrational spectroscopy on the SW620 or SW480 model system at the single‐cell level have been undertaken using synchrotron Fourier transform infrared microspectroscopy on live cells and Raman spectroscopy of a small number of fixed cells combined with stimulated Raman scattering …”

Label‐free live cell imaging by Confocal Raman Microscopy identifies CHO host and producer cell lines

“…Confocal Raman microscopy has been introduced recently as a promising tool for label free analysis of cells and 3D tissue cultures 37, and has been used to detect stem cell differentiation 38, tumor cells 39 and particle uptake 40. In the field of biotechnology and bioengineering, Raman spectroscopy has been used to monitor CHO cell characteristics for on‐line process monitoring 41, 42.…”

Distinguishing Different Cancerous Human Cells by Raman Spectroscopy Based on Discriminant Analysis Methods

“…It is known that cellular biochemical components vary depending upon the cancer cells coming from different organs, and different malignancy degrees. The difference is critical for the development of Raman spectroscopy as a new clinical diagnostic approach [10,11,[13][14][15]. The main objective of the present experimental study was to investigate the biochemical difference in these different cancer cells (SH-SY5Y, HeLa, HO-8910, MDA-MB-231, U87, A549), the cells of distinct malignancy degree (MDA-MB-231 and MCF-7) and the normal cell line and cancer cells (HEB and U87) utilizing Raman spectroscopy.…”