
Liquid Biopsy. Molecular análisis of CTCs and circulating tumor DNA. The triumph of multi-omics from a blood sample
The increase in prevalence and incidence rates of cancer worldwide requires effective diagnostic and treatment selection strategies and one of the challenges to overcome is the dynamic panorama of the disease, known as tumor heterogeneity, where intra and intro heterogeneity mark a difference and require continuous and precise monitoring methods. This heterogeneity is the fundamental pillar of cases of resistance and treatment failures.
Advances in genetic sequencing have made possible to identify at the molecular level the deregulations that trigger cancer, mutations and continuous processes of clonal evolution, but the standard for identifying and evaluating patient-specific biomarkers, mutations and genetic signatures that will lead to the appropriate selection of treatments is to perform a tissue biopsy, which are invasive, expensive and do not capture the heterogeneity of the tumor.
Liquid biopsy, on the other hand, is more suitable for longitudinal monitoring of the disease and captures the heterogeneity and clonal evolution that can lead to drug and treatment resistance solutions.
ctDNA as the gold-standard in cancer identification and the triumph of multi-omics
cfDNAs (circulating free DNAs) are DNA fragments found in body fluids of healthy and unhealthy patients, where ctDNA constitutes between 0.01-1% of the total cfDNA. The ctDNA profile has received attention in early diagnosis, treatment selection, identification of resistances mechanisms and detection of post-surgical MRD in numerous types of cancer. Therefore, ctDNA provides a simple methodology to obtain information, but is limited to point mutations, structural rearrangements, copy number variants (CNVs) and changes in DNA methylation, constituting itself as the best-established genomic analysis study molecule in the oncology research.
However, the genomic information provided by ctDN analysis must be complemented with transcriptomic and proteomic data for a more details assessment of a tumor´s phenotype and thus obtain more precise and real-time information for personalize treatment. A genomic analysis provides information on mutations acquired in the evolutionary history of the tumor, while transcriptomic analysis opens a window to the epigenetic influence on gene expression and therefore access to the current state of the tumor, so the interaction between genome and transcriptome is quite relevant to identify updated and precise treatment options. Therefore, the ability of CTCs to provide genomic and transcriptomic information in addition to the genomic information from ctDNAs from the same patient sample is a new perspective that is increasingly welcomed.
Impact of CTC enrichment on prognosis in metastatic breast cancer (MBC)
A technology that has played an important role in the assessment of breast cancer following the above criteria has been the Parsortix system (ANGLE plc., Guilford UK). The technology allows the isolation and analysis of CTCs present in the bloodstream and that have been shed from the primary tumor.
The presence and quantity of CTCs, especially in metastatic breast cancer, is closely related to patient survival. Counts of 5>CTC per 7.5 ml of blood tend to have a lower overall survival compared to those with lower counts. This prognostic value is due to the fact that CTCs contribute to the metastatic spread of the tumour, although there are studies that suggest that CTC counts alone do not always constitute a definitive prognostic indicator and factors such as the stage of the disease, inflammatory environment or cases such as patients with advanced metastatic disease and highly inflammatory blood environment should be considered, the CTC count would not have significant prognostic value.
Microfluidic platforms such as Parsortix, not only capture individual CTCs but also clusters or aggregates of CTCs that add another dimension in the assessment of prognosis, since these aggregates are associated with an even greater metastatic potential than individual CTCs, further highlighting the aggressive nature of the disease.
The detection of megakaryocytes, large bone marrow cells involved in platelet production in blood samples from patients with MBC and isolated by Parsortix are related to an indication of the advanced state of the disease due to a highly inflammatory environment, which is related to a shorter overall survival.
CTC enrichment using systems such as Parsortix facilitates downstream molecular analysis, providing valuable real-time information about the tumour. By analysing the gene expression profile of captured CTCs, a deeper understanding of tumour characteristics and their potential for resistance to treatments can be obtained. This information can be crucial for tailoring therapy and predicting patient outcomes.
Several studies have highlighted the benefits of cell enrichment on Parsortix systems compared to other systems available on the market, in particular its ability to capture a broader range of CTCs, including those that have undergone EMT (Epithelial to Mesenchymal Transition), which allows cancer cells to become more invasive and metastatic, so that traditional epithelial marking methods could miss these cells and underestimate the aggressiveness of the disease.
In conclusion, CTC enrichment using platforms such as Parsortix, significantly improves the understanding of prognosis in breast cancer.
The technology enables the detection and quantification of CTCs and CTC associates, which are strong indicators of disease progression and survival
Analysis of CTCs during EMT often missed by more traditional methods.
The presence of megakaryocytes in post-enrichment blood samples offers additional prognostic information.
Subsequent molecular analysis provides a complete picture of tumour characteristic, ultimately helping to guide treatment decisions and improve patient care.
Referencias
Wishart G, Templeman A, Hendry F, Miller K, Pailhes-Jimenez AS. Molecular Profiling of Circulating Tumour Cells and Circulating Tumour DNA: Complementary Insights from a Single Blood Sample Utilising the Parsortix® System. Curr Issues Mol Biol. 2024 Jan 17;46(1):773-787. doi: 10.3390/cimb46010050. PMID: 38248352; PMCID: PMC10814787.
Templeman A, Miller MC, Cooke MJ, O’Shannessy DJ, Gurung Y, Pereira T, Peters SG, Piano M, Teo M, Khazan N, Kim K, Cohen E, Lopez HB, Alvarez F, Ciccioli M, Pailhes-Jimenez AS. Analytical performance of the FDA-cleared Parsortix® PC1 system. J Circ Biomark. 2023 Aug 7;12:26-33. doi: 10.33393/jcb.2023.2629. PMID: 37601320; PMCID: PMC10434983.
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