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Sci—Fri AM: Mountain — 04: Label‐free Raman spectroscopy of single tumour cells detects early radiation‐induced glycogen synthesis associated with increased radiation resistance
Author(s) -
Matthews Q,
Isabelle M,
Harder S,
Brolo AG,
Lum JJ,
Jirasek A
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4894943
Subject(s) - radioresistance , radiosensitivity , glycogen , lncap , clonogenic assay , cancer research , viability assay , cell , biology , cell cycle , cell culture , radiation therapy , chemistry , medicine , biochemistry , cancer cell , cancer , genetics
Purpose: To use label‐free Raman spectroscopy (RS) for early treatment monitoring of tumour cell radioresistance. Methods: Three human tumour cell lines, two radioresistant (H460, SF 2 = 0.57 and MCF7, SF 2 = 0.70) and one radiosensitive (LNCaP, SF 2 = 0.36), were irradiated with single fractions of 2, 4, 6, 8 or 10 Gy. In additional experiments, H460 and MCF7 cells were irradiated under co‐treatment with the anti‐diabetic drug metformin, a known radiosensitizing agent. Treated and control cultures were analyzed with RS daily for 3 days post‐treatment. Single‐cell Raman spectra were acquired from 20 live cells per sample, and experiments were repeated in triplicate. The combined data sets were analyzed with principal component analysis using standard algorithms. Cells from each culture were also subjected to standard assays for viability, proliferation, cell cycle, and radiation clonogenic survival. Results: The radioresistant cells (H460, MCF7) exhibited a RS molecular radiation response signature, detectable as early as 1 day post‐treatment, of which radiation‐induced glycogen synthesis is a significant contributor. The radiosensitive cells (LNCaP) exhibited negligible glycogen synthesis. Co‐treatment with metformin in MCF7 cells blocked glycogen synthesis, reduced viability and proliferation, and increased radiosensitivity. Conversely, metformin co‐treatment in H460 cells did not produce these same effects; importantly, both radiation‐induced synthesis of glycogen and radiosensitivity were unaffected. Conclusions: Label‐free RS can detect early glycogen synthesis post‐irradiation, a previously undocumented metabolic mechanism associated with tumour cell radioresistance that can be targeted to increase radiosensitivity. RS monitoring of intratumoral glycogen may provide new opportunities for personalized combined modality radiotherapy treatments.