Measurable morphological features of single circulating tumor cells in selected solid tumors-A pilot study

Area of Science:

• Oncology
• Cell Biology
• Biotechnology

Background:

• Liquid biopsies, particularly circulating tumor cells (CTCs), are crucial for understanding metastasis.
• Current CTC analysis often focuses on enumeration and limited marker-based phenotyping, lacking detailed biological insights.
• Morphological analysis of CTCs may enhance understanding of cancer dissemination and improve isolation techniques.

Purpose of the Study:

• To quantitatively describe the morphological features of CTCs, including size, shape, protrusions, and micronuclei.
• To investigate variations in CTC morphology across different cancer types (lung, ovarian, breast, prostate) and phenotypes.
• To correlate CTC morphology with epithelial-mesenchymal transition (EMT) status.

Main Methods:

• Imaging flow cytometry was used to identify and phenotype CTCs using epithelial, mesenchymal, and exclusion markers.
• Standardized methods were applied to analyze CTC morphology, including size, shape (circularity, diagonal values), protrusions, and micronuclei.
• Open-source software QuPath was utilized for detailed morphological measurements of CTCs and leukocytes/endothelial cells.

Main Results:

• A total of 1156 CTCs were analyzed, showing larger and more irregular shapes compared to leukocytes/endothelial cells.
• Epithelial CTCs were largest (median 18.2 μm), while mesenchymal CTCs were smallest (median 10.4 μm).
• Lung cancer CTCs were largest; prostate and breast cancer CTCs were smallest. Epithelial CTCs showed high elongation, mesenchymal CTCs were irregular. Protrusions and micronuclei were rare, observed mainly in epithelial and EMT CTCs.

Conclusions:

• Significant variability exists in CTC morphology based on phenotypic classification and organ of origin.
• Morphological characteristics, such as size and shape, can influence CTC isolation methods.
• This study provides the first detailed morphological measurements of CTCs during EMT and describes protrusions and micronuclei in CTCs.