Applying Probe Electrospray Ionization Mass Spectrometry to Cytological Diagnosis: A Preliminary Study by Using Cultured Lung Cancer Cells

Our plain-English summary of Applying Probe Electrospray Ionization Mass Spectrometry to Cytological Diagnosis: A Preliminary Study by Using Cultured Lung Cancer Cells, by Y. Morimoto, T. Oya, M. Ichimura-Shimizu, et al (Acta Cytologica, 2021).

The study

• Authors: Y. Morimoto, T. Oya, M. Ichimura-Shimizu, M. Matsumoto, H. Ogawa, T. Kobayashi, S. Sumida, T. Kakimoto, M. Yamashita, C. Cheng, K. Tsuneyama
• Journal: Acta Cytologica
• Published: 2021;65(5):430-439
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Cytology and histology are 2 indispensable diagnostic tools for cancer diagnosis, which are rapidly increasing in importance with aging populations. We applied mass spectrometry (MS) as a rapid approach for swiftly acquiring nonmorphological information of interested cells. Conventional MS, which primarily rely on promoting ionization by pre-applying a matrix to cells, has the drawback of time-consuming both on data acquisition and analysis. As an emerging method, probe electrospray ionization-MS (PESI-MS) with a dedicated probe is capable to pierce sample and measure specimen in small amounts, either liquid or solid, without the requirement for sample pretreatment. Furthermore, PESI-MS is timesaving compared to the conventional MS. Herein, we investigated the capability of PESI-MS to characterize the cell types derived from the respiratory tract of human tissues.

Study Design: PESI-MS analyses with DPiMS-2020 were performed on various type of cultured cells including 5 lung squamous cell carcinomas, 5 lung adenocarcinomas, 5 small-cell carcinomas, 4 malignant mesotheliomas, and 2 normal controls.

Results: Several characteristic peaks were detected at around m/z 200 and 800 that were common in all samples. As expected, partial least squares-discriminant analysis of PESI-MS data distinguished the cancer cell types from normal control cells. Moreover, distinct clusters divided squamous cell carcinoma from adenocarcinoma.

Conclusion: PESI-MS presented a promising potential as a novel diagnostic modality for swiftly acquiring specific cytological information.

© 2021 S. Karger AG, Basel.

In plain English

This was a preliminary laboratory study of cultured human cell lines, not of people. It did not study asbestos exposure. The authors tested whether a quick method called PESI-MS could tell cell types apart. They analysed 21 cell lines: 5 lung squamous cell carcinoma, 5 lung adenocarcinoma, 5 small-cell carcinoma and 4 malignant mesothelioma lines, plus normal airway cells (BEAS2B) and normal mesothelial cells (MeT5A). Each sample was measured 3 times. Characteristic peaks around m/z 200 and 800 appeared in all samples. Samples frozen longer had fewer peaks (128 to 356) than samples frozen for a shorter time (597 to 1,105). In statistical clustering, normal cells separated from cancer cells, including mesothelioma for the normal mesothelial line, though some cancer measurements were hard to separate from normal ones. One peak, m/z 1,569.28, was a candidate for telling squamous cell carcinoma from adenocarcinoma. The authors saw potential for this method in cytological diagnosis. They noted a possible link between longer storage and fewer peaks, that signals from few abnormal cells might be masked by normal cells, and that the candidate peak was unidentified.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Preliminary laboratory study analysing cultured human cell lines by probe electrospray ionization mass spectrometry (PESI-MS), with multivariate statistical analysis (PLS-DA)
• Who was studied: 21 commercially available human cell lines: 5 lung squamous cell carcinomas, 5 lung adenocarcinomas, 5 small-cell carcinomas, 4 malignant mesotheliomas (Y-MESO-14, H28, H2373, H2052), and normal controls BEAS2B (airway epithelial cells) and MeT5A (mesothelial cells). No patient samples were newly collected.
• Exposure: No asbestos or other exposure was studied. The study measured cell lines with a mass spectrometer (DPiMS-2020); fiber types are not mentioned.
• Main results:
  • In all samples, characteristic peaks were detected around m/z 200 and 800.
  • Among the 11 samples with long freezer storage, the total number of peaks per sample ranged from 128 to 356. Table 1 gives 30 to 35 weeks for these samples.
  • Among samples with shorter freezer storage, the total number of peaks per sample ranged from 597 to 1,105. Table 1 gives 15 weeks for these samples.
  • In PLS-DA plots, the normal airway line BEAS2B plotted apart from the squamous cell carcinoma, adenocarcinoma and small-cell carcinoma groups.
  • The normal mesothelial line MeT5A was distinguished from each cancer type, including malignant mesothelioma. However, several measurements of malignant cells were difficult to separate from normal cells.
  • A heat map of the top 25 differing metabolites showed distinct patterns between squamous cell carcinoma and adenocarcinoma.
  • The peak m/z 1,569.28 was a candidate for distinguishing squamous cell carcinoma from adenocarcinoma. It ranked first in Table 2, with a raw p value of 0.000435.
• The authors' conclusion: The authors concluded that the study showed potential for applying rapid mass spectrometry by PESI-MS to pathological and cytological diagnosis. They plan further testing on specimens preserved for liquid-based cytology.
• Limitations the authors state:
  • Freezer storage time differed among samples. The authors suggested a possible negative correlation between storage duration and the number of detected peaks.
  • In real clinical specimens, signals from a small number of abnormal cells might be buried among signals from many normal cells.
  • The candidate peak m/z 1,569.28 could not be matched to a known substance.
  • Further analysis such as MS/MS is needed to identify the detected substances.
  • PESI-MS may not detect some substances that conventional mass spectrometry can detect.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Cytology, Histology, Squamous Cell Carcinoma, Lung Adenocarcinoma, Carcinoma, Malignant Mesothelioma, Adenocarcinoma.

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