Abstract

Whole Genome Sequencing using High-Fidelity long-read technology (WGS-HiFi) offers a clinically powerful approach to identify complex genetic alterations in cancer genomes. The 4 Power Biomarker WGS-HiFi by DrSeq lab integrates four complementary biomarker categories—single nucleotide variants (SNVs), insertions/deletions (indels), structural variations (SVs), and epigenetic modifications—to improve diagnostic yield in unresolved oncology cases. This method enables high-resolution, clinically actionable genomic profiling by revealing novel oncogenic drivers, refining prognostic assessment, and guiding targeted therapy. By overcoming the limitations of short-read sequencing, this approach supports precision oncology and provides critical insights into cases with atypical or cryptic mutational profiles.

Introduction

Cancer progression is driven by a diverse spectrum of genomic alterations, ranging from single base changes to complex multi-megabase rearrangements. While conventional short-read sequencing remains a workhorse in clinical genomics, it often fails to detect or accurately resolve variants in repetitive, GC-rich, and structurally complex regions of the genome. Such gaps can leave certain cancer cases genetically “unsolved,” leading to diagnostic uncertainty and limited therapeutic guidance.

High-Fidelity Whole Genome Sequencing (WGS-HiFi), based on long-read sequencing, offers superior read accuracy (>99.9%) and long contiguous sequences, enabling precise detection of difficult-to-characterize mutations. The 4 Power Biomarker WGS-HiFi strategy reinforces comprehensive case resolution by simultaneously profiling:

1. Point mutations (SNVs)
2. Insertions/deletions (indels)
3. Large-scale structural variations (SVs)
4. Epigenetic modifications associated with regulatory gene dysregulation

This integrated multi-biomarker framework increases clinical sensitivity, enhances variant interpretation, and directly impacts oncologic decision-making.

The 4 Power Biomarkers

• Single Nucleotide Variants (SNVs): HiFi sequencing delivers precise detection of point mutations across the genome, including cancer-relevant driver and resistance mutations within repetitive or GC-rich regions often missed by short-read platforms.
• Insertions and Deletions (Indels): Long-read accuracy enables exact characterization of indels, revealing frameshifts and exon disruptions in key tumor suppressor and oncogenes.
• Structural Variations (SVs): Base-pair level resolution of translocations, inversions, duplications, and copy number changes improves identification of fusion genes, oncogene amplification, and tumor genome instability patterns.
• Epigenetic Modifications: Direct detection of DNA methylation patterns permits correlation of genetic alterations with transcriptional regulation, aiding in differentiating driver from passenger events and supporting biomarkers for prognosis.

Methodology

Sample Preparation: High molecular weight DNA is extracted from both tumor tissue and matched normal reference samples, ensuring integrity for long-read sequencing.

Sequencing and Data Generation: HiFi sequencing using circular consensus sequencing (CCS) generates long (>15 kb) reads with high base accuracy. Target coverage depth (≥30×) is maintained for reliable variant detection.

Bioinformatics Analysis:

• SNVs and indels detected with long-read-optimized variant callers (e.g., DeepVariant for CCS data).
• SVs identified with dedicated tools such as pbsv and Sniffles for multi-class SV detection.
• Methylation calling integrated directly from raw signal to establish epigenetic profiles.
• Variants annotated against cancer-specific databases (COSMIC, ClinVar, OncoKB) for clinical relevance.
• Pathogenicity assessment guided by ACMG/AMP criteria, with reporting tailored for clinical tumor boards.

Case Studies: Results in Clinical Context

Clinical application of 4 Power Biomarker WGS-HiFi in unresolved cancer cases has demonstrated:

• Detection of novel and clinically actionable SVs missed in prior short-read sequencing
• Resolution of driver mutations in challenging genomic regions linked to targeted therapy responsiveness
• Discovery of rare structural fusions enabling enrollment into specific clinical trials
• Identification of epigenetic silencing of tumor suppressor genes with potential therapeutic reactivation strategies

These findings have changed clinical management in multiple instances by refining diagnosis, prognosis, and treatment pathways in many real life cases.

1. Detection of Cryptic Structural Variants in Breast Cancer: A study on breast cancer patients revealed that HiFi long-read sequencing detected hundreds of variants in known cancer genes that short-read sequencing missed, including an intronic structural variant in the BRCA1 gene. This structural variant, undetectable by short reads, has implications for hereditary breast cancer risk assessment and patient management. Moreover, long reads clarified the true nature of an ambiguous inversion on chromosome 16p13, reclassifying it from pathogenic to likely benign—a critical distinction for clinical decision-making.
2. Resolving a Pathogenic Duplication in PALB2 in Triple-Negative Breast Cancer: Using a combined approach of long-read sequencing and transcript analysis, clinicians identified a novel intragenic duplication within the PALB2 gene, which was reclassified as pathogenic. This finding provided a potential genetic explanation for aggressive tumor behavior and influenced treatment strategy.
3. Improved Identification of Pathogenic Variants in Rare Disease and Cancer: At Radboud University Medical Center, HiFi sequencing identified 93% of pathogenic variants in clinical samples, including complex structural variants and indels that traditional short-read methods missed. The improved sensitivity and accuracy enabled more comprehensive diagnostic evaluations, supporting clinical workflows for oncology patients with unsolved genetic profiles.
4. Uncovering Cancer-Specific RNA Isoforms Associated with Prognosis: The Anczukow lab at the Jackson Laboratory used HiFi sequencing with Iso-Seq to capture full-length cancer-specific RNA isoforms. This provided new insights into alternative splicing events linked to breast cancer survival, identifying isoforms previously absent from reference transcriptomes. Such detailed transcript-level information aids oncologists in understanding tumor biology and discovering potential drug targets.
5. Long-Read Sequencing Reclassifies Structural Variants for Accurate Diagnosis: Long-read sequencing corrected false positive structural variant calls initially made by short-read data in a large cohort of cancer patients. This led to accurate classification of variants, reducing ambiguity in genetic diagnosis and preventing misdiagnosis in clinical oncology.

Discussion

For oncologists, 4 Power Biomarker WGS-HiFi offers a single-platform, comprehensive genomic view capable of resolving previously cryptic alterations. Beyond mutation discovery, the integration of genomic structure and epigenetics provides deeper biological context, which:

• Improves interpretation in multidisciplinary tumor boards
• Supports personalized treatment selection, including off-label use based on unique biomarker profiles
• Expands eligibility for molecularly guided clinical trials

This methodology addresses common diagnostic limitations by delivering both accuracy and context—critical for complex cancer cases.

Conclusion

The 4 Power Biomarker WGS-HiFi framework establishes a new diagnostic standard for oncologists managing genomically complex or prior unsolved cancer cases. By integrating SNV, indel, SV, and epigenetic profiling from high-fidelity long reads, this approach improves mutation detection, enhances therapeutic decision-making, and supports precision oncology initiatives aimed at improving patient survival and quality of life.

Keywords: Cancer genomics, WGS-HiFi, structural variations, biomarkers, long-read sequencing, mutation detection, precision oncology, clinical genomics, tumor board integration