Valentina Vysotskaia

Enumeration and targeted analysis of KRAS , BRAF and PIK3CA mutations in CTCs captured by a label-free platform: Comparison to ctDNA and tissue in metastatic colorectal cancer

Treatment of advanced colorectal cancer (CRC) requires multimodal therapeutic approaches and need for monitoring tumor plasticity. Liquid biopsy biomarkers, including CTCs and ctDNA, hold promise for evaluating treatment response in real-time and guiding therapeutic modifications. From 15 patients with advanced CRC undergoing liver metastasectomy with curative intent, we collected 41 blood samples at different time points before and after surgery for CTC isolation and quantification using label-free Vortex technology. For mutational profiling, KRAS, BRAF, and PIK3CA hotspot mutations were analyzed in CTCs and ctDNA from 23 samples, nine matched liver metastases and three primary tumor samples. Mutational patterns were compared. 80% of patient blood samples were positive for CTCs, using a healthy baseline value as threshold (0.4 CTCs/mL), and 81.4% of captured cells were EpCAM+ CTCs. At least one mutation was detected in 78% of our blood samples. Among 23 matched CTC and ctDNA samples, we found a concordance of 78.2% for KRAS, 73.9% for BRAF and 91.3% for PIK3CA mutations. In several cases, CTCs exhibited a mutation that was not detected in ctDNA, and vice versa. Complementary assessment of both CTCs and ctDNA appears advantageous to assess dynamic tumor profiles.

Development and validation of an expanded carrier screen that optimizes sensitivity via full-exon sequencing and panel-wide copy-number-variant identification

Purpose By identifying pathogenic variants across hundreds of genes, expanded carrier screening (ECS) enables prospective parents to assess risk of transmitting an autosomal recessive or X-linked condition. Detection of at-risk couples depends on the number of conditions tested, the diseases’ respective prevalences, and the screen’s sensitivity for identifying disease-causing variants. Here we present an analytical validation of a 235-gene sequencing-based ECS with full coverage across coding regions, targeted assessment of pathogenic noncoding variants, panel-wide copy-number-variant (CNV) calling, and customized assays for technically challenging genes. Methods Next-generation sequencing, a customized bioinformatics pipeline, and expert manual call review were used to identify single-nucleotide variants, short insertions and deletions, and CNVs for all genes except FMR1 and those whose low disease incidence or high technical complexity precludes novel variant identification or interpretation. Variant calls were compared to reference and orthogonal data. Results Validation of our ECS data demonstrated >99% analytical sensitivity and >99% specificity. A preliminary assessment of 15,177 patient samples reveals the substantial impact on fetal disease-risk detection attributable to novel CNV calling (13.9% of risk) and technically challenging conditions (15.5% of risk), such as congenital adrenal hyperplasia. Conclusion Validated, high-fidelity identification of different variant types—especially in diseases with complicated molecular genetics—maximizes at-risk couple detection.

Abstract 5690: Optimized molecular barcoding enables accurate targeted mutation detection in circulating cell-free DNA (cfDNA)

The evaluation of cfDNA allows novel approaches to noninvasive detection of actionable alterations, resistance mechanisms, and tumor monitoring in patients with cancer. Importantly, tumor-specific DNA fragments represent a small minority of the cfDNA and can be obscured by false positive (FP) variants introduced by chemical damage and sequencer error. To address this, we improved key processes in the design of NGS libraries, including a new molecular barcoding approach, that maximize molecular recovery while eliminating spurious variants. We engineered a set of Illumina sequencing chemistry compatible adaptors incorporating unique molecular identifiers (barcodes) enabling reconstruction of the sequence of both strands of the original DNA molecule. These barcodes incorporate a number of key design improvements as compared to published methodologies, which enhance sequencer cluster density, thereby increasing library diversity and molecular recovery. Our new design identified both chemical and sequencer errors, reducing incorrect base calls to rates below 5e-7. We validated our methodology for use in cfDNA using both dilution experiments and patient blood samples with known oncogenic alterations via a custom capture panel targeting actionable genomic alterations in a 55kb region. By identifying the molecular origin of each read, we found that the sensitivity of detection obtained from barcoded libraries followed ideal binomial sampling expectations. We obtained an average molecular depth of 1,000 molecules per site from the plasma extracted from a single blood collection tube, which corresponded to an 80% sensitivity of detection of known oncogenic single-nucleotide and indel mutations at 0.15% mutant allele frequency (MAF) in cfDNA with no FP calls. Furthermore, we successfully detected known gene-fusions at 0.5%, and amplifications (>10 copies) down to 1% MAF. We designed and validated a custom-engineered error-correcting sequencing adapters, ideal for broad range of applications requiring high accuracy detection of ultra-low frequency alterations. Note: This abstract was not presented at the meeting. Citation Format: Carlo G. Artieri, Kyle A. Beauchamp, Valentina S. Vysotskaia, Noah C. Welker, Eric A. Evans, Clement Chu, Haluk Tezcan, Imran S. Haque. Optimized molecular barcoding enables accurate targeted mutation detection in circulating cell-free DNA (cfDNA) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5690. doi:10.1158/1538-7445.AM2017-5690

Abstract 3149: Enumeration and mutational profiling of CTCs and comparison to ctDNA and colorectal cancer liver metastases

Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LA Background Colorectal cancer (CRC) is the 3rd most common cancer diagnosed worldwide in both men and women. Only 39% of cancers are diagnosed at a localized stage, and 5-year survival rates decrease rapidly for patients with advanced and metastasized disease (stage III 61%, stage IV 8%). Better markers for detection of disease progression, therapeutic resistance and minimal residual disease are still needed. Liquid biopsies, such as CTCs and ctDNA, are emerging biomarkers shed by the tumor into the blood stream. Both markers currently are attracting growing interest for their use in disease prognosis, early detection of recurrence and are promising candidates for guiding cancer therapy in real-time. Method For rapid label-free isolation of CTCs from peripheral blood we used the Vortex technology, a microfluidic device using inertia and laminar microvortices. From 15 patients with metastatic CRC to the liver that underwent liver metastatectomy with curative intent, we collected CTCs preoperatively, at the 5th postoperative day and during follow-up visits. Cells collected were immunostained for EpCAM, CD45 and DAPI, enumerated using standardized classification criteria, and subjected to Sanger sequencing. CTC enumeration and mutational patterns were compared to the primary tumor, liver metastases and ctDNA (detected by a multiplexed PCR and enrichment technology; Kidess E et al., 2015) as well as CEA levels when available. Results 41 blood samples from 15 patients were collected at different time points prior to and after surgical resection of liver metastases. More CTCs were found in preoperatively collected CRC patient samples (2.4 CTCs/mL, 0.1 - 5.5/mL) than in age-matched healthy controls (0.1 CTCs/mL, 0 - 0.4/mL). 80% of all CRC samples were identified as positive for CTCs (based on a calculated threshold from healthy controls), with varying levels of EpCAM expression (81.4% of CTCs being EpCAM+). The number of CTCs for each patient, showed a close correlation to clinical parameters and ctDNA levels: detection of CTCs, CTC mutational profiles as well as ctDNA revealed minimal residual disease and anticipated tumor recurrence earlier than carcinoembryonic antigen (CEA) value or imaging. For example, for P006, postoperative imaging surveillance revealed progressive disease, which was accompanied by rising levels of CTCs (up to 29 CTCs/mL at the last time point) and PIK3CA mutant DNA in both plasma ctDNA and CTC DNA, while CEA remained in the normal range. Conclusion Our data illustrate that CTCs as well as ctDNA can efficiently reveal disease recurrence as well as disease progression earlier than imaging and far more reliable compared to CEA, the currently standard biomarker for CRC. Beyond enumeration, CTC molecular analysis gives additional information and will potentially help to promote the development of tailored therapies for every individual patient. Citation Format: Evelyn Kidess-Sigal, Haiyan E. Liu, Melanie Triboulet, James Che, Georges A. Poultsides, Brendan C. Visser, Andre Marziali, Marc Lee, Valentina Vysotskaia, Matthew Wiggin, Vishnu C. Ramani, Ulrich Keilholz, Ingeborg Tinhofer, Amin Zia, John Coller, Jeffrey A. Norton, Elodie Sollier, Stefanie S. Jeffrey. Enumeration and mutational profiling of CTCs and comparison to ctDNA and colorectal cancer liver metastases. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3149.