Label-Free Raman Imaging to Monitor Breast Tumor Signatures

Abstract

Although not yet ready for clinical application, methods based on Raman spectroscopy have shown significant potential in identifying, characterizing, and discriminating between noncancerous and cancerous specimens. Real-time and accurate medical diagnosis achievable through this vibrational optical method largely benefits from improvements in current technological and software capabilities. Not only is the acquisition of spectral information now possible in milliseconds and analysis of hundreds of thousands of data points achieved in minutes, but Raman spectroscopy also allows simultaneous detection and monitoring of several biological components. Besides demonstrating a significant Raman signature distinction between nontumorigenic (MCF-10A) and tumorigenic (MCF-7) breast epithelial cells, our study demonstrates that Raman can be used as a label-free method to evaluate epidermal growth factor activity in tumor cells. Comparative Raman profiles and images of specimens in the presence or absence of epidermal growth factor show important differences in regions attributed to lipid, protein, and nucleic acid vibrations. The occurrence, which is dependent on the presence of epidermal growth factor, of new Raman features associated with the appearance of phosphothreonine and phosphoserine residues reflects a signal transduction from the membrane to the nucleus, with concomitant modification of DNA/RNA structural characteristics. Parallel Western blotting analysis reveals an epidermal growth factor induction of phosphorylated Akt protein, corroborating the Raman results. The analysis presented in this work is an important step toward Raman-based evaluation of biological activity of epidermal growth factor receptors on the surfaces of breast cancer cells. With the ultimate future goal of clinically implementing Raman-guided techniques for the diagnosis of breast tumors (e.g., with regard to specific receptor activity), the current results just lay the foundation for further label-free optical tools to diagnose the disease.

Applications of Raman spectroscopy in cancer diagnosis

“…EGF addition resulted in modifications in lipid pool and DNA/RNA and vibrations from phosphorylated threonine and serine suggesting phosphorylation of signaling molecules upon addition of EFG to MCF-7 cells. This was confirmed by gel electrophoresis [150].…”

Raman Microscopy: Progress in Research on Cancer Cell Sensing

“…Raman imaging has been used to monitor breast tumor signatures. In general, human epidermal growth factor receptor 1 (EGFR or erbB1) sensing in the breast cancer cells is directly achieved by RM, which is responsible for HER2+ overexpression [ 41 ]. The Raman images were constructed (using multivariate processing methods) using untreated MCF-7 and MCF-7 cells treated with EGF (well known to contribute to cell proliferation).…”

“…The same color code is maintained for images and for spectra. Reproduced with permission from the SAGE publications [ 41 ].…”

Confocal Raman Spectral Imaging Study of DAPT, a γ-secretase Inhibitor, Induced Physiological and Biochemical Reponses in Osteosarcoma Cells

“…Compared with the mean spectra of untreated osteosarcoma cell, both DAPT-treated groups showed a decrease in the spectral features at 787 cm -1 (uracil, thymine, and cytosine, DNA backbone O-P-O stretching) [27,28], 840 cm -1 (carbohydrate, glucose) [29], 1320 cm -1 (protein, C-H) [30,31], 1656 cm -1 (protein, amide I, α-spiral) [19,32] and 2934 cm -1 (lipid, CH 3 ) [27], associated with nucleic acid, protein, lipid, and carbohydrate content. In both 10T and 20T groups, a decrease in peak intensity, as compared to the UT group, was observed at 787 cm -1 , which is associated with uracil, thymine, and cytosine ring breathing modes in DNA and RNA bases.…”