| Summary: | <p>Tumours are composed of cancer cells with various phenotypes and metabolic activities. Even though cells are from the same tumour with the same genotypes, they can manifest distinct phenotypic states in different locations. It is one of the key challenges to understand cancer metabolism and intratumorally heterogeneity using accurate, reliable, and non-destructive approaches. Single-cell Raman micro-spectroscopy (SCRM) is a label-free biochemical profiling technology that can reveal intrinsic chemical information of individual cells and give insight into metabolic profiles at the single cell and subcellular level. An informative approach to the application of Raman spectroscopy is to use stable isotope probing (Raman–SIP) to study single cell metabolism, heterogeneity, interactions in cancer cells.</p>
<p>Here, I applied SCRM and Raman–SIP to the study of bicarbonate, glycogen, and glutamine metabolism in the U87 and SUM159 cell lines and analysed metabolic reprogramming in Caco-2, which showed resistance to cancer therapy by an oncolytic virus – Newcastle disease virus.</p>
<p>Our findings indicate that the 1043-cm–1 band is a characteristic band of intracellular HCO3–. Carbonic anhydrase 9 and mitochondria are the two main factors regulating external/internal HCO3– amounts, respectively. The metabolism of bicarbonate is also upregulated by hypoxia and low glucose concentration. Glycogen has three characteristic Raman peaks, and the assignments of the bands are related to its structure. 13C labelling shows the dynamic turnover of glycogen and its distribution at the single-cell level. Glutamine is rapidly metabolised in the synthesis of endogenous cellular molecules and is heavily involved in the synthesis of proteins, lipids and nucleic acids, but the carbon in glutamine is not directly responsible for the synthesis of glycogen.</p>
<p>To conclude, Raman techniques are invaluable to analyse the metabolic response in cancers at single cell level. It provides thousands of data points for subcellular localisation, which could be exploited to develop metabolic targeting therapies and may become a key approach to future clinical developments of novel anticancer treatment.</p>
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