Abstract P6-07-05: Single-cell TOF-SIMS reveals that human breast cancer stem cells have significantly lower content of palmitoleic acid compared to their counterpart non-stem cancer cells
Authors: Ide Yoshimi , Waki Michihiko , Ishizaki Itsuko , Nagata Yasuyuki , Taki Yumiko , Hosokawa Yuko , Matsunuma Ryoichi , Ogura Hiroyuki , Shiiya Norihiko , Sanada Noriaki , Setou Mitsutoshi 
Published: May 2015

Abstract
Background
Distinguishing individual cancers according to their biochemical heterogeneity have provided much useful information to clinical site. Recently, the cancer stem cell (CSC) theory has been accepted as a concept that explains the mechanism of cancer recurrence and resistance to treatment. To characterize such particular cell populations in heterogeneous tissues, we conducted combination of fluorescence activated cell sorting (FACS) and time-of-flight secondary-ion mass spectrometry (TOF-SIMS) and applied the method to analyses of breast CSCs. TOF-SIMS, which enables to visualize the composition of molecules with mass over 100 Da that were obtained in specimen, has been employed to analyze surface of industrial materials and biomaterials. This method is thus suitable for performing single cell analysis of membranous lipids.
Methods
Breast cancer specimens surgically resected from two patients were enzymatically dispersed into cells. They were labeled with fluorescence-conjugated antibodies of CD45, CD44, and CD24. The cells of CD45-CD44+ CD24- were sorted as CSCs with FACS as well as CD45-CD44- CD24+ cells as non-stem cancer cells (NSCCs). TOF-SIMS analysis and fatty acid analysis was performed according to our previous study published in Surface and Interface Analysis (1). The surface of the sorted cells was analyzed by a PHI TRIFT V (ULVAC-PHI Inc., Kanagawa, Japan) TOF-SIMS instrument. Primary ion beam is irradiated to the surface of the samples and, secondary ions derived from samples are calculated by time-of-flight with the information of the place where the molecular ions were ejected. Negative secondary ions were obtained with a mass range of m/z 0–1850. Mass spectra were analyzed by WinCadenceN software (ULVAC-PHI Inc.) to obtain ion counts and ion images. Integrated ion intensities of FA were normalized using phosphoric acid intensity. The Welch’s t-test was used to compare the normalized ion counts with P-value &lt; 0.05 taken as statistically significant.
Results
FACS analyses successfully collected CD45-/CD44+/CD24- CSCs and CD45-/CD44-/CD24+ non-stem cancer cells (NSCCs) in both two cases, which were corresponding to o.33% and 0.74% of all cells in case 1, and 0.14% and 1.14% in case 2. TOF-SIMS analyses visualized phosphoric acids and four fatty acid (FA) species in the sorted CSCs and NSCCs. These ions probably came from membranous phosphopolipids and they were uniformly detected from the locus where the cell attached. Integrated ion intensity of palmitoleic acids [FA(16:1)] of CSCs normalized by phosphoric acids signals were significantly decreased than that of CD45-/CD44-/CD24+ NSCCs as a counterpart. Therefore, our novel method successfully provided lipid composition analysis of individual cells classified with complicated combination of marker expressions in clinical specimens composed of heterogeneous cellular populations, and characterized lipid composition of CSCs.
Reference
1. Nagata Y, Ishizaki I, Waki M, Ide Y, Hossen A, Ohnishi K, et al. Glutaraldehyde Fixation Method for Single-Cell Lipid Analysis by Time-of-Flight Secondary Ion-Mass Spectrometry. Surface and interface analysis : SIA. 2014:DOI: 10.1002/sia/5522.
Citation Format: Yoshimi Ide, Michihiko Waki, Itsuko Ishizaki, Yasuyuki Nagata, Yumiko Taki, Yuko Hosokawa, Ryoichi Matsunuma, Hiroyuki Ogura, Norihiko Shiiya, Noriaki Sanada, Mitsutoshi Setou. Single-cell TOF-SIMS reveals that human breast cancer stem cells have significantly lower content of palmitoleic acid compared to their counterpart non-stem cancer cells [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-07-05.