Int J Med Sci 2020; 17(5):577-590. doi:10.7150/ijms.43506

Research Paper

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

Jie Li1#, Rui Wang2#, Jie Qin2✉, Haishan Zeng3, Kaige Wang1, Qingli He4, Difan Wang5, Shuang Wang1✉

1. Institute of Photonics and Photon-Technology, Northwest University, Xi'an, Shaanxi 710069, China
2. Department of Orthopedics, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
3. Imaging Unit - Integrative Oncology Department, BC Cancer Research Center, Vancouver, BC, V5Z1L3, Canada
4. Department of Physics, Northwest University, Xi'an, Shaanxi 710069, China
5. School of Life, Xidian University, Xi'an, Shaanxi 710071, China
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Li J, Wang R, Qin J, Zeng H, Wang K, He Q, Wang D, Wang S. Confocal Raman Spectral Imaging Study of DAPT, a γ-secretase Inhibitor, Induced Physiological and Biochemical Reponses in Osteosarcoma Cells. Int J Med Sci 2020; 17(5):577-590. doi:10.7150/ijms.43506. Available from

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Confocal Raman microspectral imaging was adopted to elucidate the cellular drug responses of osteosarcoma cells (OC) to N-[N-(3, 5-difluorophenyl acetyl)-L-alanyl]-sphenylglycine butyl ester (DAPT), a γ-secretase inhibitor, by identifying the drug induced subcellular compositional and structural changes.

Methods: Spectral information were acquired from cultured osteosarcoma cells treated with 0 (Untreated Group, UT), 10 (10 μM DAPT treated, 10T), 20 μM (20 μM DAPT treated, 20T) DAPT for 24 hours. A one-way ANOVA and Tukey's honest significant difference (HSD) post hoc multiple test were sequentially applied to address spectral features among three groups. Multivariate algorithms such as K-means clustering analysis (KCA) and Principal component analysis (PCA) were used to highlight the structural and compositional differences, while, univariate imaging was applied to illustrate the distribution pattern of certain cellular components after drug treatment.

Results: Major biochemical changes in DAPT-induced apoptosis came from changes in the content and structure of proteins, lipids, and nucleic acids. By adopted multivariate algorithms, the drug induced cellular changes was identified by the morphology and spectral characteristics between untreated cells and treated cells, testified that DAPT mainly acted in the nuclear region. With the increase of the drug concentration, the content of main subcellular compositions, such nucleic acid, protein, and lipid decreased. In an addition, DAPT-induced nuclear fragmentation and apoptosis was depicted by the univariate Raman image of major cellular components (nucleic acids, proteins and lipids).

Conclusions: The achieved Raman spectral and imaging results illustrated detailed DAPT-induced subcellular compositional and structural variations as a function of drug dose. Such observations can not only explain drug therapeutic mechanisms of OC DAPT treatment, and also provide new insights for accessing the medicine curative efficacy and predicting prognosis.

Keywords: Confocal Raman microspectral imaging, Osteosarcoma cells, DAPT, Drug Responses, Cellular Heterogeneity