Longitudinal Evaluation of Circulating Tumor DNA Using Sensitive Amplicon-Based Next-Generation Sequencing to Identify Resistance Mechanisms to Immune Checkpoint Inhibitors for Advanced Urothelial Carcinoma.

Serial evaluation of circulating tumor DNA may allow noninvasive assessment of drivers of resistance to immune checkpoint inhibitors (ICIs) in advanced urothelial cancer (aUC). We used a novel, amplicon-based next-generation sequencing assay to identify genomic alterations (GAs) pre- and post-therapy in 39 patients with aUC receiving ICI and 6 receiving platinum-based chemotherapy (PBC). One or more GA was seen in 95% and 100% of pre- and post-ICI samples, respectively, commonly in TP53 (54% and 54%), TERT (49% and 59%), and BRCA1/BRCA2 (33% and 33%). Clearance of ≥1 GA was seen in 7 of 9 patients responding to ICI, commonly in TP53 (n = 4), PIK3CA (n = 2), and BRCA1/BRCA2 (n = 2). A new GA was seen in 17 of 20 patients progressing on ICI, frequently in BRCA1/BRCA2 (n = 6), PIK3CA (n = 3), and TP53 (n = 3), which seldom emerged in patients receiving PBC. These findings highlight the potential for longitudinal circulating tumor DNA evaluation in tracking response and resistance to therapy.

Analytical and clinical validation of an amplicon-based next generation sequencing assay for ultrasensitive detection of circulating tumor DNA.

Next-generation sequencing of circulating tumor DNA presents a promising approach to cancer diagnostics, complementing conventional tissue-based diagnostic testing by enabling minimally invasive serial testing and broad genomic coverage through a simple blood draw to maximize therapeutic benefit to patients. LiquidHALLMARK® is an amplicon-based next-generation sequencing assay developed for the genomic profiling of plasma-derived cell-free DNA (cfDNA). The comprehensive 80-gene panel profiles point mutations, insertions/deletions, copy number alterations, and gene fusions, and further detects oncogenic viruses (Epstein-Barr virus (EBV) and hepatitis B virus (HBV)) and microsatellite instability (MSI). Here, the analytical and clinical validation of the assay is reported. Analytical validation using reference genetic materials demonstrated a sensitivity of 99.38% for point mutations and 95.83% for insertions/deletions at 0.1% variant allele frequency (VAF), and a sensitivity of 91.67% for gene fusions at 0.5% VAF. In non-cancer samples, a high specificity (≥99.9999% per-base) was observed. The limit of detection for copy number alterations, EBV, HBV, and MSI were also empirically determined. Orthogonal comparison of epidermal growth factor receptor (EGFR) variant calls made by LiquidHALLMARK and a reference allele-specific polymerase chain reaction (AS-PCR) method for 355 lung cancer specimens revealed an overall concordance of 93.80%, while external validation with cobas® EGFR Mutation Test v2 for 50 lung cancer specimens demonstrated an overall concordance of 84.00%, with a 100% concordance rate for EGFR variants above 0.4% VAF. Clinical application of LiquidHALLMARK in 1,592 consecutive patients demonstrated a high detection rate (74.8% circulating tumor DNA (ctDNA)-positive in cancer samples) and broad actionability (50.0% of cancer samples harboring alterations with biological evidence for actionability). Among ctDNA-positive lung cancers, 72.5% harbored at least one biomarker with a guideline-approved drug indication. These results establish the high sensitivity, specificity, accuracy, and precision of the LiquidHALLMARK assay and supports its clinical application for blood-based genomic testing.

Mechanically and chemically defined hydrogel matrices for patient-derived colorectal tumor organoid culture.

Patient-derived tumor organoids offer potentially useful models of cancer tissue physiology. Yet, conventional organoid cultures utilize generic matrices that are difficult to tailor for various unique tumor microenvironments. Here, we employ synthetic, enzymatically crosslinked hydrogels to define mechanical and biochemical properties hypothesized to be relevant for maintaining these organoids. We show that a single extracellular matrix component, gelatin, suffices to support colorectal cancer patient-derived xenograft (CRC-PDX) organoid survival, and that high matrix stiffness synergizes with hypoxia to increase organoid growth and metabolism in a majority of CRC-PDX lines tested. Moreover, we demonstrate that defined gelatin-based hydrogels support CRC-PDX tumor growth in vivo and organoid sensitivity to various CRC therapeutic drugs in vitro in a largely comparable fashion to a conventional reconstituted basement membrane matrix. Based on our findings, we propose that enzymatically crosslinked hydrogels potentially provide a platform for designing mechanically and biochemically defined matrices for various types of patient-derived tumor organoids.