Who’s Who? Discrimination of Human Breast Cancer Cell Lines by Raman and FTIR Microspectroscopy

Abstract

(1) Breast cancer is presently the leading cause of death in women worldwide. This study aims at identifying molecular biomarkers of cancer in human breast cancer cells, in order to differentiate highly aggressive triple-negative from non-triple-negative cancers, as well as distinct triple-negative subtypes, which is currently an unmet clinical need paramount for an improved patient care. (2) Raman and FTIR (Fourier transform infrared) microspectroscopy state-of-the-art techniques were applied, as highly sensitive, specific and non-invasive methods for probing heterogeneous biological samples such as human cells. (3) Particular biochemical features of malignancy were unveiled based on the cells’ vibrational signature, upon principal component analysis of the data. This enabled discrimination between TNBC (triple-negative breast cancer) and non-TNBC, TNBC MSL (mesenchymal stem cell-like) and TNBC BL1 (basal-like 1) and TNBC BL1 highly metastatic and low-metastatic cell lines. This specific differentiation between distinct TNBC subtypes—mesenchymal from basal-like, and basal-like 1 with high-metastatic potential from basal-like 1 with low-metastatic potential—is a pioneer result, of potential high impact in cancer diagnosis and treatment.

Diagnosing molecular subtypes of breast cancer by means of Raman spectroscopy

“…As expected, the LA and LB samples have similar spectral profiles, suggesting similar constitution, as they have similar gene expression and biochemical constituents, with higher intensities in virtually all peaks compared to the normal tissue spectrum, but increased peaks of lipids, whereas the TN samples have higher intensities in peaks found approximately at 1100, 1300, and 1440 cm −1 , assigned to proteins (collagen). These results are consistent with the literature of Raman spectroscopy in evaluating molecular subtypes of breast cancer 38–44 . Bi et al 38 differentiated breast cancer cells HER2‐enriched and HER2 nonenriched, obtaining a sensitivity and specificity of 99%, respectively, and showed that HER2‐enriched cells had a higher lipid content due to exacerbated fatty acid and phospholipid synthesis.…”

“…These results are consistent with the literature of Raman spectroscopy in evaluating molecular subtypes of breast cancer. [38][39][40][41][42][43][44] Bi et al 38 differentiated breast cancer cells HER2enriched and HER2 nonenriched, obtaining a sensitivity and specificity of 99%, respectively, and showed that HER2-enriched cells had a higher lipid content due to exacerbated fatty acid and phospholipid synthesis. Bendau et al 39 differentiated the collagen molecular characteristics between TN metastatic tumors and nonmetastatic tumors that are ER-positive.…”

“…In addition, breast cancer cells showed higher levels of collagen and lipids (peak at 1333 and 1304 cm −1 , respectively). Santos et al 44 applied Raman microspectroscopy and FTIR (Fourier transform infrared) and after analyzing the principal component of the data, they were able to discriminate between TN and non‐TN breast cancer, as well as TNBCMSL (cell‐like mesenchymal trunk) and highly metastatic and little metastatic TNBC BL1 (basal‐like 1) and TNBC BL1 cell lines. A PCA analysis allowed to discriminate between TNBC (MDA‐MB‐231, HCC‐1143 and MDA‐MB‐468) compared to non‐TNBC cell lines (MCF‐7).…”

“…Raman spectroscopy is also suitable to unveil the compositional differences between molecular subtypes. Differences in the amount of lipids and proteins, as well as in the amount of nucleic acids, may be able to identify the molecular subtypes as reported in several studies 38–44 …”

“…Differences in the amount of lipids and proteins, as well as in the amount of nucleic acids, may be able to identify the molecular subtypes as reported in several studies. [38][39][40][41][42][43][44] The aim of this study was to evaluate the compositonal differences between the molecular subtypes of carcinoma (LA, LB, HER2, and TN) in ex vivo breast tissues versus normal tissues (NT) by means of dispersive Raman spectroscopy compared to anatomopathological (gold standard) and molecular evaluations through IHC, FISH, and other molecular methods. Then, exploratory analysis by means of PCA was used to unveil the spectral differences between the molecular subtypes to correlate these differences with the biochemical components and morphological structures responsible for these cellular alterations.…”