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Page 6 of 20 Singh et al. Cancer Drug Resist. 2025;8:56

Table 2. Components of liquid biopsy-based detection of circulating circRNAs for drug resistance monitoring in cancer: a comparative
analysis

Component
S.N. Specific component Description/principle Advantages Limitations/disadvantages Ref.
category
Primary source of Minimally
circulating circRNAs; invasive; widely Low RNA yield; variability
1 Biological sample Plasma/serum [5]
obtained from peripheral used; good RNA depending on handling
blood stability
Alternative fluids for Non-invasive; Lower circRNA concentrations;
2 Biological sample Urine/saliva/CSF site-specific cancers (e.g., can reflect local limited standard protocols [6]
urological, CNS) tumor biology
Enhances tumor
Isolation of tumor-derived
Cellular/molecular specificity; Time-consuming; requires
3 Exosome isolation exosomes containing [47]
assay protects RNA specialized kits or equipment
circRNAs
from degradation
Increases
Cellular/molecular Digests linear RNAs to May result in partial RNA loss if
4 RNase R treatment specificity for [35]
assay enrich circRNAs not optimized
circRNAs
Commercial kits (e.g., High RNA purity;
RNA extraction Column-based/magnetic Qiagen, Norgen) used for optimized for Costly; requires careful sample
5 [48]
method bead kits isolating total RNA from low-input handling
biofluids samples
Amplifies the back-splice Cost-effective; Limited to known targets; less
qRT-PCR with divergent
6 Detection principle junction unique to highly specific for sensitive for low-abundance [49]
primers
circRNAs known circRNAs circRNAs
Absolute
Uses microdroplets to
7 Detection principle ddPCR detect and quantify RNA quantification; Expensive; requires specialized [50]
copies with high sensitivity ideal for rare instruments
circRNAs
Comprehensive;
Unbiased sequencing to detects novel Data-intensive; needs
8 Detection principle RNA-seq detect both known and circRNAs and bioinformatics expertise [51]
novel circRNAs expression
changes
Tools used to identify Enables
Bioinformatics CIRCexplorer2, find_circ, circRNAs from sequencing genome-wide Complex pipelines; prone to false
9 [52]
analysis CIRI2, DCC data by mapping circRNA positives without proper filtering
back-splice junctions discovery
Provides
Databases for annotation,
circBase, functional
Bioinformatics interaction prediction, and Limited clinical annotations for
10 CircInteractome, context and [53]
analysis biological interpretation of novel circRNAs
circAtlas regulatory
circRNAs
network insights
Real-time, longitudinal Guides therapy Not yet standardized for clinical
assessment of treatment decisions;
11 Clinical relevance Resistance monitoring use; requires large-scale [45]
response via circRNA non-invasive validation
dynamics surveillance
Using circRNA expression Supports
Personalized treatment Translational challenges;
12 Clinical relevance changes to tailor treatment precision [54]
adaptation regulatory hurdles
regimens dynamically oncology
circRNAs: Circular RNAs; CSF: cerebrospinal fluid; CNS: central nervous system; qRT-PCR: quantitative reverse transcription polymerase chain
reaction; ddPCR: droplet digital polymerase chain reaction; RNA-seq: RNA sequencing; DCC: deleted in colorectal carcinoma.
CIRCULATING CIRCRNAS AS EMERGING BIOMARKERS IN LIQUID BIOPSY FOR DRUG
RESISTANCE SURVEILLANCE IN CANCER
CircRNAs are becoming increasingly popular as circulating biomarkers. Evidence of their dysregulation in
numerous cancers adds to our knowledge of resistance mechanisms and a bright future for therapeutic
monitoring . The liquid biopsy-based approach for detecting circulating circRNAs is used to monitor drug
[15]
resistance in cancer . The process begins with the identification of resistant cancer cells and the collection
[15]

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