Cancer testis antigen burden (CTAB): a novel biomarker of tumor-associated antigens in lung cancer.

BACKGROUND: Cancer-testis antigens (CTAs) are tumor antigens that are normally expressed in the testes but are aberrantly expressed in several cancers. CTA overexpression drives the metastasis and progression of lung cancer, and is associated with poor prognosis. To improve lung cancer diagnosis, prognostic prediction, and drug discovery, robust CTA identification and quantitation is needed. In this study, we examined and quantified the co-expression of CTAs in lung cancer to derive cancer testis antigen burden (CTAB), a novel biomarker of immunotherapy response. METHODS: Formalin fixed paraffin embedded (FFPE) tumor samples in discovery cohort (n = 5250) and immunotherapy and combination therapy treated non-small cell lung cancer (NSCLC) retrospective (n = 250) cohorts were tested by comprehensive genomic and immune profiling (CGIP), including tumor mutational burden (TMB) and the mRNA expression of 17 CTAs. PD-L1 expression was evaluated by IHC. CTA expression was summed to derive the CTAB score. The median CTAB score for the discovery cohort of 170 was applied to the retrospective cohort as cutoff for CTAB "high" and "low". Biomarker and gene expression correlation was measured by Spearman correlation. Kaplan-Meier survival analyses were used to detect overall survival (OS) differences, and objective response rate (ORR) based on RECIST criteria was compared using Fisher's exact test. RESULTS: The CTAs were highly co-expressed (p < 0.05) in the discovery cohort. There was no correlation between CTAB and PD-L1 expression (R = 0.011, p = 0.45) but some correlation with TMB (R = 0.11, p = 9.2 × 10-14). Kaplan-Meier survival analysis of the immunotherapy-treated NSCLC cohort revealed better OS for the pembrolizumab monotherapy treated patients with high CTAB (p = 0.027). The combination group demonstrated improved OS compared to pembrolizumab monotherapy group (p = 0.04). The pembrolizumab monotherapy patients with high CTAB had a greater ORR than the combination therapy group (p = 0.02). CONCLUSIONS: CTA co-expression can be reliably measured using CGIP in solid tumors. As a biomarker, CTAB appears to be independent from PD-L1 expression, suggesting that CTAB represents aspects of tumor immunogenicity not measured by current standard of care testing. Improved OS and ORR for high CTAB NSCLC patients treated with pembrolizumab monotherapy suggests a unique underlying aspect of immune response to these tumor antigens that needs further investigation.

Incidental Detection of Maternal Neoplasia in Noninvasive Prenatal Testing.

BACKGROUND: Noninvasive prenatal testing (NIPT) uses cell-free DNA (cfDNA) as an analyte to detect copy-number alterations in the fetal genome. Because maternal and fetal cfDNA contributions are comingled, changes in the maternal genome can manifest as abnormal NIPT results. Circulating tumor DNA (ctDNA) present in cases of maternal neoplasia has the potential to distort the NIPT readout to a degree that prevents interpretation, resulting in a nonreportable test result for fetal aneuploidy. METHODS: NIPT cases that showed a distortion from normal euploid genomic representation were communicated to the caregiving physician as nonreportable for fetal aneuploidy. Follow-up information was subsequently collected for these cases. More than 450000 pregnant patients who submitted samples for clinical laboratory testing >3 years are summarized. Additionally, in-depth analysis was performed for >79000 research-consented samples. RESULTS: In total, 55 nonreportable NIPT cases with altered genomic profiles were cataloged. Of these, 43 had additional information available to enable follow-up. A maternal neoplasm was confirmed in 40 of these cases: 18 malignant, 20 benign uterine fibroids, and 2 with radiological confirmation but without pathological classification. CONCLUSIONS: In a population of pregnant women who submitted a blood sample for cfDNA testing, an abnormal genomic profile not consistent with fetal abnormalities was detected in about 10 out of 100000 cases. A subset of these observations (18 of 43; 41.9%) was attributed to maternal malignant neoplasms. These observational results suggest the need for a controlled trial to evaluate the potential of using cfDNA as an early biomarker of cancer.

Using Targeted Sequencing of Paralogous Sequences for Noninvasive Detection of Selected Fetal Aneuploidies.

BACKGROUND: Current methods for noninvasive prenatal testing (NIPT) ascertain fetal aneuploidies using either direct counting measures of DNA fragments from specific genomic regions or relative measures of single nucleotide polymorphism frequencies. Alternatively, the ratios of paralogous sequence pairs were predicted to reflect fetal aneuploidy. We developed a NIPT assay that uses paralog sequences to enable noninvasive detection of fetal trisomy 21 (T21) and trisomy 18 (T18) using cell-free DNA (cfDNA) from maternal plasma. METHODS: A total of 1060 primer pairs were designed to determine fetal aneuploidy status, fetal sex, and fetal fraction. Each library was prepared from cfDNA by coamplifying all 1060 target pairs together in a single reaction well. Products were measured using massively parallel sequencing and deviations from expected paralog ratios were determined based on the read depth from each paralog. RESULTS: We evaluated this assay in a blinded set of 480 cfDNA samples with fetal aneuploidy status determined by the MaterniT21® PLUS assay. Samples were sequenced (mean = 2.3 million reads) with 432 samples returning a result. Using the MaterniT21 PLUS assay for paired plasma aliquots from the same individuals as a reference, all 385 euploid samples, all 31 T21 samples, and 14 of 16 T18 samples were detected with no false positive results observed. CONCLUSIONS: This study introduces a novel NIPT aneuploidy detection approach using targeted sequencing of paralog motifs and establishes proof-of-concept for a potentially low-cost, highly scalable method for the identification of selected fetal aneuploidies with performance and nonreportable rate similar to other published methods.

Determination of fetal DNA fraction from the plasma of pregnant women using sequence read counts.

OBJECTIVE: This study introduces a novel method, referred to as SeqFF, for estimating the fetal DNA fraction in the plasma of pregnant women and to infer the underlying mechanism that allows for such statistical modeling. METHODS: Autosomal regional read counts from whole-genome massively parallel single-end sequencing of circulating cell-free DNA (ccfDNA) from the plasma of 25 312 pregnant women were used to train a multivariate model. The pretrained model was then applied to 505 pregnant samples to assess the performance of SeqFF against known methodologies for fetal DNA fraction calculations. RESULTS: Pearson's correlation between chromosome Y and SeqFF for pregnancies with male fetuses from two independent cohorts ranged from 0.932 to 0.938. Comparison between a single-nucleotide polymorphism-based approach and SeqFF yielded a Pearson's correlation of 0.921. Paired-end sequencing suggests that shorter ccfDNA, that is, less than 150 bp in length, is nonuniformly distributed across the genome. Regions exhibiting an increased proportion of short ccfDNA, which are more likely of fetal origin, tend to provide more information in the SeqFF calculations. CONCLUSION: SeqFF is a robust and direct method to determine fetal DNA fraction. Furthermore, the method is applicable to both male and female pregnancies and can greatly improve the accuracy of noninvasive prenatal testing for fetal copy number variation.

Noninvasive detection of a balanced fetal translocation from maternal plasma.

BACKGROUND: Massively parallel sequencing of circulating cell free (ccf) DNA from maternal plasma has been demonstrated to be a powerful method for the detection of fetal copy number variations (CNVs). Although the detection of CNVs has been described by multiple independent groups, genomic aberrations resulting in copy number-neutral events including balanced translocations have proven to be more challenging to detect noninvasively from ccf DNA. METHODS: Data modeling was initially performed to evaluate multiple methods, ultimately leveraging the short length of ccf DNA and paired-end sequencing to construct read-specific mapping characteristics. After testing in a model system, we evaluated the methods on ccf DNA isolated from the plasma of a donor known to be carrying a fetus with a balanced translocation [t(8;11)]. Sequencing was performed with Illumina sequencing technology. RESULTS: Our methodology identified the known translocation (P = 1.21 × 10(-8)) and discounted the likelihood of others, enabling the base specific identification of the rearrangement positions. In total, 402 unique sequencing reads spanned the putative breakpoints, of which 76 contained the structural rearrangement. In addition, 38 of the chimeric reads were mapped to each of the resulting derivative chromosomes, supporting the presence of a reciprocal translocation. Finally, we identified a 6-bp deletion present within der(8) that was absent from the der(11) reciprocal rearrangement. CONCLUSIONS: We have developed an algorithm to detect balanced rearrangements and applied our methodology to demonstrate the first proof-of-principle study on the noninvasive detection of a fetal-specific balanced translocation by sequencing ccf DNA from maternal plasma.

Real-world comprehensive genomic and immune profiling reveals distinct age- and sex-based genomic and immune landscapes in tumors of patients with non-small cell lung cancer.

Introduction: Younger patients with non-small cell lung cancer (NSCLC) (<50 years) represent a significant patient population with distinct clinicopathological features and enriched targetable genomic alterations compared to older patients. However, previous studies of younger NSCLC suffer from inconsistent findings, few studies have incorporated sex into their analyses, and studies targeting age-related differences in the tumor immune microenvironment are lacking. Methods: We performed a retrospective analysis of 8,230 patients with NSCLC, comparing genomic alterations and immunogenic markers of younger and older patients while also considering differences between male and female patients. We defined older patients as those ≥65 years and used a 5-year sliding threshold from <45 to <65 years to define various groups of younger patients. Additionally, in an independent cohort of patients with NSCLC, we use our observations to inform testing of the combinatorial effect of age and sex on survival of patients given immunotherapy with or without chemotherapy. Results: We observed distinct genomic and immune microenvironment profiles for tumors of younger patients compared to tumors of older patients. Younger patient tumors were enriched in clinically relevant genomic alterations and had gene expression patterns indicative of reduced immune system activation, which was most evident when analyzing male patients. Further, we found younger male patients treated with immunotherapy alone had significantly worse survival compared to male patients ≥65 years, while the addition of chemotherapy reduced this disparity. Contrarily, we found younger female patients had significantly better survival compared to female patients ≥65 years when treated with immunotherapy plus chemotherapy, while treatment with immunotherapy alone resulted in similar outcomes. Discussion: These results show the value of comprehensive genomic and immune profiling (CGIP) for informing clinical treatment of younger patients with NSCLC and provides support for broader coverage of CGIP for younger patients with advanced NSCLC.

Immunologic Factors Associated with Differential Response to Neoadjuvant Chemoimmunotherapy in Triple-Negative Breast Cancer.

Background: KEYNOTE-522 resulted in FDA approval of the immune checkpoint inhibitor pembrolizumab in combination with neoadjuvant chemotherapy for patients with early-stage, high-risk, triple-negative breast cancer (TNBC). Unfortunately, pembrolizumab is associated with several immune-related adverse events (irAEs). We aimed to identify potential tumor microenvironment (TME) biomarkers which could predict patients who may attain pathological complete response (pCR) with chemotherapy alone and be spared the use of anti-PD-1 immunotherapy. Methods: Comprehensive immune profiling, including RNA-seq gene expression assessment of 395 immune genes, was performed on matched FFPE tumor samples from 22 stage I-III TNBC patients (14 patients treated with neoadjuvant chemotherapy alone (NAC) and 8 treated with neoadjuvant chemotherapy combined with pembrolizumab (NAC+I)). Results: Differential gene expression analysis revealed that in the NAC group, IL12B and IL13 were both significantly associated with pCR. In the NAC+I group, LCK and TP63 were significantly associated with pCR. Patients in both treatment groups exhibiting pCR tended to have greater tumor inflammation than non-pCR patients. In the NAC+I group, patients with pCR tended to have greater cell proliferation and higher PD-L1 expression, while in the NAC group, patients with pCR tended to have lower cancer testis antigen expression. Additionally, the NAC+I group trended toward a lower relative dose intensity averaged across all chemotherapy drugs, suggesting that more dose reductions or treatment delays occurred in the NAC+I group than the NAC group. Conclusions: A comprehensive understanding of immunologic factors could potentially predict pCR to chemotherapy alone, enabling the avoidance of the unnecessary treatment of these patients with checkpoint inhibitors.

Mechanisms of immune modulation in the tumor microenvironment and implications for targeted therapy.

The efficacy of cancer therapies is limited to a great extent by immunosuppressive mechanisms within the tumor microenvironment (TME). Numerous immune escape mechanisms have been identified. These include not only processes associated with tumor, immune or stromal cells, but also humoral, metabolic, genetic and epigenetic factors within the TME. The identification of immune escape mechanisms has enabled the development of small molecules, nanomedicines, immune checkpoint inhibitors, adoptive cell and epigenetic therapies that can reprogram the TME and shift the host immune response towards promoting an antitumor effect. These approaches have translated into series of breakthroughs in cancer therapies, some of which have already been implemented in clinical practice. In the present article the authors provide an overview of some of the most important mechanisms of immunosuppression within the TME and the implications for targeted therapies against different cancers.

RNA Sequencing Identifies Novel NRG1 Fusions in Solid Tumors that Lack Co-Occurring Oncogenic Drivers.

NRG1 gene fusions are rare, therapeutically relevant, oncogenic drivers that occur across solid tumor types. To understand the landscape of NRG1 gene fusions, 4397 solid tumor formalin-fixed, paraffin-embedded samples consecutively tested by comprehensive genomic and immune profiling during standard care were analyzed. Nineteen NRG1 fusions were found in 17 unique patients, across multiple tumor types, including non-small-cell lung (n = 7), breast (n = 2), colorectal (n = 3), esophageal (n = 2), ovarian (n = 1), pancreatic (n = 1), and unknown primary (n = 1) carcinomas, with a cumulative incidence of 0.38%. Fusions were identified with breakpoints across four NRG1 introns spanning 1.4 megabases, with a mixture of known (n = 8) and previously unreported (n = 11) fusion partners. Co-occurring driver alterations in tumors with NRG1 fusions were uncommon, except colorectal carcinoma, where concurrent alterations in APC, BRAF, and ERBB2 were present in a subset of cases. The overall lack of co-occurring drivers highlights the importance of identifying NRG1 gene fusions, as these patients are unlikely to harbor other targetable alterations. In addition, RNA sequencing is important to identify NRG1 gene fusions given the variety of fusion partners and large genomic areas where breakpoints can occur.

Validation of the Labcorp Plasma Focus Test to Facilitate Precision Oncology Through Cell-Free DNA Genomic Profiling of Solid Tumors.

Genomic profiling is critical for precision oncology to guide treatment decisions. Liquid biopsy testing is a complementary approach to tissue testing, particularly when tissue is not readily available. The Labcorp Plasma Focus test is a circulating cell-free DNA genomic profiling test that identifies actionable variants in solid cancers, including non-small-cell lung, colorectal, melanoma, breast, esophageal, gastroesophageal junction, and gastric cancers. This study highlights the analytical validation of the test, including accuracy compared with orthogonal methods, as well as sensitivity, specificity, precision, reproducibility, and repeatability. Concordance with orthogonal methods showed percent positive agreement of 98.7%, 89.3%, and 96.2% for single nucleotide variants (SNVs), insertion/deletions (indels), and copy number amplifications (CNAs), respectively, and 100.0% for translocations and microsatellite instability (MSI). Analytical sensitivity revealed a median limit of detection of 0.7% and 0.6% for SNVs and indels, 1.4-fold for CNAs, 0.5% variant allele frequency for translocations, and 0.6% for MSI. Specificity was >99% for SNVs/indels and 100% for CNAs, translocations, and MSI. Average positive agreement from precision, reproducibility, and repeatability experiments was 97.5% and 88.9% for SNVs/indels and CNAs, and 100% for translocations and MSI. Taken together, these data show that the Labcorp Plasma Focus test is a highly accurate, sensitive, and specific approach for cell-free DNA genomic profiling to supplement tissue testing and inform treatment decisions.

Clinical characterization of the mutational landscape of 24,639 real-world samples from patients with myeloid malignancies.

Myeloid neoplasms represent a broad spectrum of hematological disorders for which somatic mutation status in key driver genes is important for diagnosis, prognosis and treatment. Here we summarize the findings of a targeted, next generation sequencing laboratory developed test in 24,639 clinical myeloid samples. Data were analyzed comprehensively and as part of individual cohorts specific to acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and myeloproliferative neoplasms (MPN). Overall, 48,015 variants were detected, and variants were found in all 50 genes in the panel. The mean number of mutations per patient was 1.95. Mutation number increased with age (Spearman's rank correlation coefficient, ρ = 0.29, P < 0.0001) and was higher in patients with AML than MDS or MPN (Student's t-test, P < 0.0001). TET2 was the most common mutation detected (19.1% of samples; 4,695/24,639) including 7.7% (1,908/24,639) with multi-hit TET2 mutations. Mutation frequency was correlated between patients with cytopenias and MDS (Spearman's, ρ = 0.97, P < 2.2×10-16) with the MDS diagnostic gene SF3B1 being the only notable outlier. This large retrospective study shows the utility of NGS testing to inform clinical decisions during routine clinical care and highlights the mutational landscape of a broad population of myeloid patients.

Detection of microdeletion 22q11.2 in a fetus by next-generation sequencing of maternal plasma.

BACKGROUND: Efforts have been undertaken recently to assess the fetal genome through analysis of circulating cell-free (ccf) fetal DNA obtained from maternal plasma. Sequencing analysis of such ccf DNA has been shown to enable accurate prenatal detection of fetal aneuploidies, including trisomies of chromosomes 21, 18, and 13. We sought to extend these analyses to examine subchromosomal copy number variants through the sequencing of ccf DNA. We examined a clinically relevant genomic region, chromosome 22q11.2, the location of a series of well-characterized deletion anomalies that cause 22q11.2 deletion syndrome. METHODS: We sequenced ccf DNA isolated from maternal plasma samples obtained from 2 patients with confirmed 22q11.2 deletion syndrome and from 14 women at low risk for fetal chromosomal abnormalities. The latter samples were used as controls, and the mean genomic coverage was 3.83-fold. Data were aligned to the human genome, repetitive regions were removed, the remaining data were normalized for GC content, and z scores were calculated for the affected region. RESULTS: The median fetal DNA contribution for all samples was 18%, with the affected samples containing 17%-18% fetal DNA. Using a technique similar to that used for sequencing-based fetal aneuploidy detection from maternal plasma, we detected a statistically significant loss of representation of a portion of chromosome 22q11.2 in both of the affected fetal samples. No such loss was detected in any of the control samples. CONCLUSIONS: Noninvasive prenatal diagnosis of subchromosomal fetal genomic anomalies is feasible with next-generation sequencing.

Hypomethylation of the 14-3-3σ promoter leads to increased expression in non-small cell lung cancer.

The 14-3-3 proteins are a set of seven highly conserved proteins that have recently been implicated in having a role in human tumorigenesis. However, the mechanism by which 14-3-3 proteins may act in this capacity is not well understood. In this study, we examined the expression of one of the 14-3-3 family members, 14-3-3σ, since it was shown previously to be aberrantly altered in human tumors. Using quantitative rtPCR and immunohistochemistry, we found that the expression levels of 14-3-3σ were elevated in the majority of human non-small cell lung cancers (NSCLC) we examined. Surprisingly, we found that the 14-3-3σ gene was hypomethylated in lung tumors relative to normal lung tissue suggesting that decreased DNA methylation resulted in increased expression of 14-3-3σ in NSCLC. We also determined the gene copy number for 14-3-3σ in tumor samples and found no significant correlation with elevated mRNA expression. And also no mutations were found in 14-3-3σ gene. Overall, our data suggest that misregulated expression of 14-3-3σ gene may be due to altered methylation status. © 2011 Wiley-Liss, Inc.

Assessing CAR T-Cell Therapy Response Using Genome-Wide Sequencing of Cell-Free DNA in Patients With B-Cell Lymphomas.

Methods that enable monitoring of therapeutic efficacy of autologous chimeric antigen receptor (CAR) T-cell therapy will be clinically useful. The aim of this study is to demonstrate the feasibility of blood-derived cell-free DNA (cfDNA) to predict CAR T-cell therapy response in patients with refractory B-cell lymphomas. Whole blood was collected before and throughout CAR T-cell therapy until day 154. Low-coverage (∼0.4×), genome-wide cfDNA sequencing, similar to that established for noninvasive prenatal testing, was performed. The genomic instability number (GIN) was used to quantify plasma copy number alteration level. Twelve patients were enrolled. Seven (58%) patients achieved a complete response (CR); 2 (25%), a partial response. Median progression-free survival was 99 days; median overall survival was not reached (median follow-up, 247 days). Altogether, 127 blood samples were analyzed (median, 10 samples/patient [range 8-13]). All 5 patients who remained in CR at the time of last measurement had GIN <170 (threshold). Two patients who attained CR, but later relapsed, and all but one patient who had best response other than CR had last GIN measurement of >170. In 5 of 6 patients with relapsed or progressive disease, increasing GIN was observed before the diagnosis by imaging. The abundance of CAR T-cell construct (absolute number of construct copies relative to the number of human genome equivalents) also showed a trend to correlate with outcome (day 10, P = .052). These data describe a proof-of-concept for the use of multiple liquid biopsy technologies to monitor therapeutic response in B-cell lymphoma patients receiving CAR T-cell therapy.

Early, On-Treatment Levels and Dynamic Changes of Genomic Instability in Circulating Tumor DNA Predict Response to Treatment and Outcome in Metastatic Breast Cancer Patients.

BACKGROUND: Circulating tumor DNA (ctDNA) offers high sensitivity and specificity in metastatic cancer. However, many ctDNA assays rely on specific mutations in recurrent genes or require the sequencing of tumor tissue, difficult to do in a metastatic disease. The purpose of this study was to define the predictive and prognostic values of the whole-genome sequencing (WGS) of ctDNA in metastatic breast cancer (MBC). METHODS: Plasma from 25 patients with MBC were taken at the baseline, prior to treatment (T0), one week (T1) and two weeks (T2) after treatment initiation and subjected to low-pass WGS. DNA copy number changes were used to calculate a Genomic Instability Number (GIN). A minimum predefined GIN value of 170 indicated detectable ctDNA. GIN values were correlated with the treatment response at three and six months by Response Evaluation Criteria in Solid Tumours assessed by imaging (RECIST) criteria and with overall survival (OS). RESULTS: GIN values were detectable (>170) in 64% of patients at the baseline and were significantly prognostic (41 vs. 18 months OS for nondetectable vs. detectable GIN). Detectable GIN values at T1 and T2 were significantly associated with poor OS. Declines in GIN at T1 and T2 of > 50% compared to the baseline were associated with three-month response and, in the case of T1, with OS. On the other hand, a rise in GIN at T2 was associated with a poor response at three months. CONCLUSIONS: Very early measurements using WGS of cell-free DNA (cfDNA) from the plasma of MBC patients provided a tumor biopsy-free approach to ctDNA measurement that was both predictive of the early tumor response at three months and prognostic.

Genome-wide Sequencing of Cell-free DNA Enables Detection of Copy-number Alterations in Patients with Cancer Where Tissue Biopsy is Not Feasible.

When tissue biopsy is not medically prudent or tissue is insufficient for molecular testing, alternative methods are needed. Because cell-free DNA (cfDNA) has been shown to provide a representative surrogate for tumor tissue, we sought to evaluate its utility in this clinical scenario. cfDNA was isolated from the plasma of patients and assayed with low-coverage (∼0.3×), genome-wide sequencing. Copy-number alterations (CNA) were identified and characterized using analytic methods originally developed for noninvasive prenatal testing (NIPT) and quantified using the genomic instability number (GIN), a metric that reflects the quantity and magnitude of CNAs across the genome. The technical variability of the GIN was first evaluated in an independent cohort comprising genome-wide sequencing results from 27,754 women who consented to have their samples used for research and whose NIPT results yielded no detected CNAs to establish a detection threshold. Subsequently, cfDNA sequencing data from 96 patients with known cancers but for whom a tissue biopsy could not be obtained are presented. An elevated GIN was detected in 35% of patients and detection rates varied by tumor origin. Collectively, CNAs covered 96.6% of all autosomes. Survival was significantly reduced in patients with an elevated GIN relative to those without. Overall, these data provide a proof of concept for the use of low-coverage, genome-wide sequencing of cfDNA from patients with cancer to obtain relevant molecular information in instances where tissue is difficult to access. These data may ultimately serve as an informative complement to other molecular tests.

Horizons in Veterinary Precision Oncology: Fundamentals of Cancer Genomics and Applications of Liquid Biopsy for the Detection, Characterization, and Management of Cancer in Dogs.

Cancer is the leading cause of death in dogs, in part because many cases are identified at an advanced stage when clinical signs have developed, and prognosis is poor. Increased understanding of cancer as a disease of the genome has led to the introduction of liquid biopsy testing, allowing for detection of genomic alterations in cell-free DNA fragments in blood to facilitate earlier detection, characterization, and management of cancer through non-invasive means. Recent discoveries in the areas of genomics and oncology have provided a deeper understanding of the molecular origins and evolution of cancer, and of the "one health" similarities between humans and dogs that underlie the field of comparative oncology. These discoveries, combined with technological advances in DNA profiling, are shifting the paradigm for cancer diagnosis toward earlier detection with the goal of improving outcomes. Liquid biopsy testing has already revolutionized the way cancer is managed in human medicine - and it is poised to make a similar impact in veterinary medicine. Multiple clinical use cases for liquid biopsy are emerging, including screening, aid in diagnosis, targeted treatment selection, treatment response monitoring, minimal residual disease detection, and recurrence monitoring. This review article highlights key scientific advances in genomics and their relevance for veterinary oncology, with the goal of providing a foundational introduction to this important topic for veterinarians. As these technologies migrate from human medicine into veterinary medicine, improved awareness and understanding will facilitate their rapid adoption, for the benefit of veterinary patients.

Quantification of fetal DNA by use of methylation-based DNA discrimination.

BACKGROUND: Detection of circulating cell-free fetal nucleic acids in maternal plasma has been used in noninvasive prenatal diagnostics. Most applications rely on the qualitative detection of fetal nucleic acids to determine the genetic makeup of the fetus. This method leads to an analytic dilemma, because test results from samples that do not contain fetal DNA or are contaminated with maternal cellular DNA can be misleading. We developed a multiplex approach to analyze regions that are hypermethylated in placenta relative to maternal blood to evaluate the fetal portion of circulating cell-free DNA isolated from maternal plasma. METHODS: The assay used methylation-sensitive restriction enzymes to eliminate the maternal (unmethylated) fraction of the DNA sample. The undigested fetal DNA fraction was then coamplified in the presence of a synthetic oligonucleotide to permit competitive PCR. The amplification products were quantified by single-base extension and MALDI-TOF MS analysis. RESULTS: Using 2 independent markers, (sex determining region Y)-box 14 (SOX14) and T-box 3 (TBX3), we measured a mean of 151 copies of fetal DNA/mL plasma and a mean fetal fraction of 0.13 in samples obtained from pregnant women. We investigated 242 DNA samples isolated from plasma from pregnant and nonpregnant women and observed an analytical sensitivity and specificity for the assay of 99% and 100%, respectively. CONCLUSIONS: By investigating several regions in parallel, we reduced the measurement variance and enabled quantification of circulating cell-free DNA. Our results indicate that this multiplex methylation-based reaction detects and quantifies the amount of fetal DNA in a sample isolated from maternal plasma.

Arsenicals produce stable progressive changes in DNA methylation patterns that are linked to malignant transformation of immortalized urothelial cells.

Aberrant DNA methylation participates in carcinogenesis and is a molecular hallmark of a tumor cell. Tumor cells generally exhibit a redistribution of DNA methylation resulting in global hypomethylation with regional hypermethylation; however, the speed in which these changes emerge has not been fully elucidated and may depend on the temporal location of the cell in the path from normal, finite lifespan to malignant transformation. We used a model of arsenical-induced malignant transformation of immortalized human urothelial cells and DNA methylation microarrays to examine the extent and temporal nature of changes in DNA methylation that occur during the transition from immortal to malignantly transformed. Our data presented herein suggest that during arsenical-induced malignant transformation, aberrant DNA methylation occurs non-randomly, progresses gradually at hundreds of gene promoters, and alters expression of the associated gene, and these changes are coincident with the acquisition of malignant properties, such as anchorage independent growth and tumor formation in immunocompromised mice. The DNA methylation changes appear stable, since malignantly transformed cells removed from the transforming arsenical exhibited no reversion in DNA methylation levels, associated gene expression, or malignant phenotype. These data suggest that arsenicals act as epimutagens and directly link their ability to induce malignant transformation to their actions on the epigenome.

Epigenetic mediated transcriptional activation of WNT5A participates in arsenical-associated malignant transformation.

Arsenic is a human carcinogen with exposure associated with cancer of the lung, skin, and bladder. Many potential mechanisms have been implicated as playing a role in the process of arsenical-induced malignancy including the perturbation of signaling pathways and aberrant epigenetic regulation. We initiated studies to examine the role of a member of the non-canonical WNT signaling pathway, WNT5A, in UROtsa cells and arsenite [URO-ASSC] and monomethylarsonous acid [URO-MSC] malignantly transformed variants. We present data herein that suggest that WNT5A is transcriptionally activated during arsenical-induced malignant transformation. This WNT5A transcriptional activation is correlated with the enrichment of permissive histone modifications and the reduction of repressive modifications in the WNT5A promoter region. The epigenetic activation of WNT5A expression and acetylation of its promoter remain after the removal of the arsenical, consistent with the maintenance of an anchorage independent growth phenotype in these cells. Additionally, treatment with epigenetic modifying drugs supports a functional role for these epigenetic marks in controlling gene expression. Reduction of WNT5A using lentiviral shRNA greatly attenuated the ability of these cells to grow in an anchorage independent fashion. Extension of our model into human bladder cancer cell lines indicates that each of the cell lines examined also express WNT5A. Taken together, these data suggest that the epigenetic remodeling of the WNT5A promoter is correlated with its transcriptional activation and this upregulation likely participates in arsenical-induced malignant transformation.