Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) Imaging Service

Breast cancer is a leading cause of cancer-related death among women globally. Trace elements like iron (Fe), copper (Cu), and zinc (Zn) are essential for various cellular processes and are involved in cancer progression and metastasis. Changes in the distribution of these elements in breast cancer tissues have been documented, but their exact roles remain unclear. The study explores the distribution of both essential and non-essential metals, such as strontium (Sr) and barium (Ba), in breast cancer tissues using Laser Ablation-Inductively Coupled Plasma-Time-of-Flight-Mass Spectrometry (LA-ICP-ToF-MS). This method allows for high spatial resolution elemental imaging, offering potential for diagnostic applications in differentiating cancerous tissues from healthy ones.

LA-ICP-ToF-MS bioimaging

LA-ICP-ToF–MS analysis was performed using an Analyte G2 excimer Laser Ablation System (Teledyne Photon Machines, USA) with a wavelength of 193 nm, equipped with an aerosol rapid introduction system (ARIS) and coupled directly to the torch of a Vitesse ICP-ToF–MS platform (Nu Instruments, UK). Instrumental parameters such as laser He flow, nebulizer Ar flow, and torch position were optimized daily to obtain the best sensitivity while ablating a NIST 612 "Trace Elements in Glass" and monitoring the signals for 115In and 238U. The parameters used for the analysis are summarized in Table S2. The monitored mass range was 20–240 amu while blanking the ranges 24.5–30.5 and 38–47 amu to avoid signal saturation at the detector. Two spectra where binned before baseline correction and 20 after baseline correction and the spectra were stored every 1.03 ms. Elemental mapping was performed using a laser beam spot size of 35 µm (square shape) with a laser dosage of 4. Data acquisition was performed by Nu Codaq software (Nu Instruments).

External calibration was carried out by manufacturing gelatine standards following a protocol previously described by Westerhausen et al. [42]. Briefly, 20% pork gelatine (MM ingredients, UK) was heated and mixed with an Amberlyst® 15 ion-exchange resin (Sigma-Aldrich, USA) to reduce the metal background concentrations. Then, the resin was separated by centrifugation, and the clean gelatine was spiked with the desired concentrations of Single Element ICP Standard Solution Roti®Star (Carl Roth, Germany) and filled into molds (Grace Bio-Labs, USA). Calibrations ranged between 0 and 33 µg g−1 for Fe and 0 and 19 µg g−1 for Cu, Zn, and Sr. To calculate the exact concentrations of the analytes in the standards, an aliquot of each standard was dried overnight, weighed, and digested with 20% nitric acid (CL Chem-Lab Nitric, Belgium). The resulting solution was then diluted with ultrapure water and analyzed using an Agilent 8900 ICP-MS/MS system. The parameters for the cross-quantification are summarized in Table S2, and Fe, Cu, Zn, and Sr calibration curves are displayed in Figure S3. To build the LA-ICP-ToF–MS calibration curves, 5 lines of 200 pixels of each standard were ablated. The average intensities were calculated and plotted against their respective concentration values.

Figure 4 compares the elemental distribution of Fe, Cu, Zn, and Sr in the tumor niche and stroma areas of breast cancer tissues. The analysis reveals that Cu, Zn, and Sr are significantly more concentrated in the tumor niche compared to the surrounding stroma, suggesting that these metals are preferentially accumulated in cancerous tissue. It also shows that Fe concentrations were more variable, with significant differences observed between non-metastatic and metastatic groups, especially in the tumor areas. The figure underscores the importance of distinguishing between tumor and stroma regions to better understand elemental distribution in cancer tissues.

Figure 4. Comparison of the tumor niche and stroma distributions in the different sample groups.

The study demonstrates that essential metals like Fe, Cu, Zn, and Sr accumulate at higher levels in breast cancer tissues compared to healthy controls. The findings suggest that these metals, particularly Sr and Ba, may serve as biomarkers for detecting cancer areas. No significant differences were observed between non-metastatic and metastatic samples, indicating that metal accumulation likely occurs during early cancer stages. Additionally, the analysis of tumor niche versus stroma revealed higher metal concentrations in the tumor, likely due to the accelerated metabolism of cancer cells. The study proposes that LA-ICP-ToF-MS could be a valuable tool for understanding the role of metals in cancer progression and offers insights into the use of elemental distribution as a potential diagnostic tool.

Reference

1. Escudero-Cernuda, Sara et al. "Quantitative distribution of essential elements and non-essential metals in breast cancer tissues by LA-ICP-TOF-MS." Analytical and bioanalytical chemistry vol. 417,2 (2025): 361-371. doi:10.1007/s00216-024-05652-8