Clinics of Oncology Review Article ISSN: 2640-1037 Volume 5 Circulating Tumor Cells and Cell-Free Nucleic Acids as Predictor Factors for Early Pancreatic Cancer Dissemination, A Literature Review Sapovalovs S1*, Truskovs A2, Gailiss J2, Gardovskis A1 and Gardovskis J1 1Department of general surgery, Pauls Stradins CUH, Riga, Latvia 2Rigas Stradins university, medical faculty, Riga, Latvia *Corresponding author: Received: 02 May 2021 Copyright: Accepted: 18 May 2021 Sergejs Sapovalovs, ©2021 Sapovalovs S et al. This is an open access article Published: 24 May 2021 Department of general surgery, Pauls distributed under the terms of the Creative Commons Attri- Stradins CUH, Riga, Latvia, bution License, which permits unrestricted use, distribution, E-mail: [email protected] and build upon your work non-commercially. Citation: Sapovalovs S, Circulating Tumor Cells and Cell-Free Nu- cleic Acids as Predictor Factors for Early Pancreatic Cancer Dissemination, A Literature Review. Clin Onco. 2021; 5(1): 1-31 Abbreviations CD – Cluster of Differentiation; CK – Cytokeratin; CTC(s) – Circulating Tumor Cells; DEP – Dielectrophoresis; EMT – Epithelial to Mesenchymal Transition; EpCAM – Epithelial Cell Adhesion Molecule; FISH – Fluorescence in Situ Hybridization; GEDI – Geometrically Enhanced Differential Immunocapture; MACS – Magnetic Cell Sorter; MET – Mesenchymal–Epithelial Transition; PC – Pancreatic Cancer; PCR – Polymerase Chain Re- action; PDAC – Pancreatic Ductal Adenocarcinoma; PSMA – Prostate-Specific Membrane Antigen; QMS – Quadrupole Magnetic cell Sorter; cfDNA – Cell-Free DNA; cfNA(s) – Cell-Free Nuclei Acid(s); cfmRNA – Cell-Free mRNA; cfmiRNA – Cell-Free miRNA; ctDNA – Circulating Tumor DNA; ddPCR – Droplet Digital Polymerase Chain Reaction 1. Abstract sis, real‐time monitoring and determining recurrence, improved 1.1. Background: Pancreatic cancer remains as one of the most management, and development of targeted therapy in the field of aggressive and deadliest of cancers largely due to formidable chal- cancer studies. Furthermore, the development of radiological and lenges in diagnosis and therapy. Consensus standard treatment for endoscopic techniques, such as sampling of portal venous blood patients with nonmetastatic Pancreatic Cancer (PC) incorporates via endoscopic ultrasound, has enabled obtaining and examining possible neoadjuvant chemotherapy with timely surgical resection material from localizations typically inaccessible by traditional bi- and adjuvant chemotherapy. However, despite all the sophistica- opsies. At the moment, a limited number of “liquid biopsy” plat- tion of modern radiological and endoscopic techniques, the de- forms have been successfully approved, while many are still in cision regarding operability is often only made intra-operatively, preclinical and clinical trial stages and required further research therefore subjecting a patient to unnecessary surgical intervention, and validation. and postponing the possibility of starting early chemotherapy. 1.3. Conclusion: The purpose of this review was to list, system- 1.2. Main Body: Tumors shed various elements of cancerous tis- atize and highlight advantages and limitations of different strat- sue, such as Circulating Tumor Cells (CTCs) and cell-free nucle- egies and individual platforms currently used in CTC and cfNA ic acids (cfNAs) (i.e., cell-free circulating tumor DNA (ctDNA), identification, isolation and analysis. This review emphasizes the cell-free mRNA (cfmRNA) and cell-free miRNA (cfmiRNA)), need for further standardization of different methodologies and into the circulatory system. Detection and analysis of these bio- accumulation of results under equal conditions in large-scale stud- markers through “liquid biopsy” has emerged as a novel, mini- ies, as well as combining different strategies in single devices to mally invasive approach for early detection, determining progno- achieve optimal results. clinicsofoncology.com 1 Volume 5 Issue 1 -2021 Review Article 2. Introduction 3. Tumor-Derived Components for Liquid Biopsy Pancreatic Cancer (PС) is the 12th most common cancer and the Blood and bodily fluids are used as a means of biomarker detec- 7th leading cause of cancer-related death worldwide with 495’773 tion. Through either exocrine and endocrine glands, pancreatic tu- new cases and 466’003 deaths in 2020 [1]. Given the asymptomat- mors secrete CTCs and cFNAS into the circulatory system. While ic course of the disease, the disease is often diagnosed in the later blood is extensively in liquid biopsies due to easy acquisition and stages. In cases of radical resection, the five-year survival rate is minimal invasiveness, it contains circulating materials other than 20 to 25%. Given the poor response to radiation and chemother- tumor-specific components, which in result decreases the con- apy, the predicted five-year survival without surgery is 3 to 5%. centration of cancer-specific components within the sample. Oth- Cancer diagnosis is mainly based on data from radiological ex- er body fluids, such as pancreatic juice, bile, stool, saliva, urine, aminations such as CT, MR, PET in combination with endo US and pleural effusion may be used as a primary or complementary data, oncological markers, as well as the results of examinations source of biomarkers for the detection of pancreatic cancer. of tissue samples obtained during surgical biopsies or Fine Nee- Enrichment is a crucial step in liquid biopsies, as bodily fluids dle Aspiration Cytology (FNAC). Although conventional tissue contain circulating materials besides CTCs and cfNA’s. The pres- biopsies are a gold standard in cancer diagnostics and can provide ence of these materials is particularly prevalent in blood samples. invaluable information, these methods are painful, invasive, and In context of liquid biopsies, “enrichment” implies a purification anatomically difficult to perform, often carry risks of additional process of isolating tumor cells from other components (e.g. leu- complications such as bleeding, infection, and dispersal of cancer kocytes) by running the sample through a platform. Generally, cells into healthy tissue and therefore, they are not always feasible enrichment methods rely on different properties of the target com- to perform and/ or repeat. Additionally, the use of all these meth- ponent: (a) biological properties (e.g., specific surface protein ex- ods cannot completely exclude the presence of micrometastases, pression) and (b) physical properties (e.g., size, density, electric thus, unresectable patients often undergo surgery that delay the charges, and deformability). Following enrichment, tumor-specific initiation of systemic therapy. components require subsequent detected. Considering the above-mentioned shortcoming of the classic PC 3.1. CTCs diagnostic methods, there is an urgent need to find highly sensitive CTCs, first described by Thomas Ashworth in 1869, represent a and high-precision minimally invasive methods for early diagno- heterogeneous group of cells with varying phenotypic and geno- sis of PС and PC dissemination. Circulating tumors cells in these typic properties that shed from primary and/or secondary tumor patients could be used in lieu of tumor tissue samples. Consider- sites, entering into the bloodstream, and circulating throughout the ing that tumors shed various complex elements of cancerous tissue body. Although CTCs are excellent candidates for liquid biopsies, such as Circulating Tumor Cells (CTCs) and cell-free nucleic ac- as their presence indicates malignancy, they were not used in clin- ids (cfNAs) (i.e., cell-free circulating tumor DNA (ctDNA), cell- ical applications until the late 1990s. free mRNA (cfmRNA) and cell-free miRNA (cfmiRNA)), into the According to literature, mechanical forces (exerted by internal tu- circulatory system, liquid biopsy has emerged as a novel, minimal- mor growth or external surgery) and/or Epithelial to Mesenchymal ly invasive tool for early stage diagnosis, determining prognosis, Transition (EMT), may be causalities of CTC secretion.EMT is monitoring therapeutic responses and tumor recurrence, as well as a biological process, where cells gain mesenchymal properties, designing innovative therapies in cancer treatment. which in return leads to an enhanced migratory capacity, invasive- In the past decade, liquid biopsy proved to be highly diagnosti- ness, and elevated resistance to apoptosis. This process allows po- cally valuable in lung, brain, and breast cancers. Importance of larized cells to transgress through the basement membrane, stroma biopsies is evident – application of such method in diagnosis of and vessel walls, and enter into the circulatory system. At a distant PC has been highlighted in several studies, where early detection site, a reverse process called the Mesenchymal–Epithelial Transi- of pancreatic cancer is associated with decreased mortality and tion (MET), as well as interaction with the Extracellular Matrix increased survival rates (increase from 3% up to 32%) amongst (ECM) of the site may induce the formation of a new metasta- patients. While numerous methods of tumor-derived components sis. This mechanism exists even in the premalignant pancreatic enrichment, detection, and analysis are available, there’s scarcity lesions, which are still not recognizable with conventional diag- of reports evaluating their diagnostic value and provide compara- nostics methods, which suggests that the metastatic spread may be tive analysis of different methods