Molecular analysis of circulating tumor DNA (ctDNA) has a large potential for clinical application by capturing tumor-specific aberrations through noninvasive sampling. In gastrointestinal stromal tumor (GIST), analysis of and mutations is important for therapeutic decisions, but the invasiveness of traditional biopsies limits the possibilities for repeated sampling. Using targeted next-generation sequencing, we have analyzed circulating cell-free DNA from 50 GIST patients. Tumor-specific mutations were detected in 16 of 44 plasma samples (36%) from treatment-naïve patients and in three of six (50%) patients treated with tyrosine kinase inhibitors. A significant association between detection of ctDNA and the modified National Institutes of Health risk classification was found. All patients with metastatic disease had detectable ctDNA, and tumor burden was the most important detection determinant. Median tumor size was 13.4 cm for patients with detectable mutation in plasma compared with 4.4 cm in patients without detectable mutation ( = 0.006). ctDNA analysis of a patient with disease progression on imatinib revealed that multiple resistance mutations were synchronously present, and detailed analysis of tumor tissue showed that these were spatially distributed in the primary tumor. Plasma samples taken throughout the course of treatment demonstrated that clonal evolution can be monitored over time. In conclusion, we have shown that detection of GIST-specific mutations in plasma is particularly feasible for patients with high tumor burden. In such cases, we have demonstrated that mutational analysis by use of liquid biopsies can capture the molecular heterogeneity of the whole tumor, and may guide treatment decisions during progression. .
Inflammatory myofibroblastic tumor (IMT) is a myofibroblastic/fibroblastic neoplasm of intermediate malignant potential. It is frequently characterized by genetic fusion of ALK with a variety of partner genes, which results in the activated ALK signaling pathway that can be targeted with kinase inhibitors. IMTs can occur in the gynecologic tract, with the uterus (corpus and cervix) being the most frequent site. Recent studies suggest that IMTs in the gynecologic tract are underrecognized, and a low-threshold for performing ALK immunohistochemistry has been proposed. The aim of this study was to evaluate the specificity of ALK immunohistochemistry for IMTs among uterine mesenchymal and mixed epithelial/mesenchymal tumors. We performed ALK immunohistochemistry on 14 molecularly confirmed uterine IMTs and 260 other uterine pure mesenchymal and mixed epithelial/mesenchymal tumors. Cases showing any positive cytoplasmic and/or membranous staining of the tumor cells were considered to be ALK positive. All 14 IMTs were confirmed to harbor ALK genetic fusion by RNA sequencing, and ALK immunostaining in the form of granular cytoplasmic positivity with paranuclear accentuation was observed in all 14 cases. ALK was negative (complete absence of staining) in all the other pure mesenchymal tumors and in all mixed epithelial/mesenchymal tumors examined. Our findings show that ALK is a highly specific diagnostic immunohistochemical marker for ALK fusion in uterine mesenchymal tumors. In the work-up of uterine mesenchymal tumors, particularly smooth muscle tumors showing myxoid stromal changes, a diagnosis of IMT should be strongly considered if ALK positivity is observed.
Defects in DNA damage repair caused by mutations in BRCA1/2, ATM or other genes have been shown to play an important role in the development and progression of prostate cancer. The influence of such mutations on anti-tumor immunity in prostate cancer, however, is largely unknown. To better understand the correlation between BRCA1/2 mutations and the immune phenotype in prostate cancer, we characterized the immune infiltrate of eight BRCA2-mutated tumors in comparison with eight BRCA1/2 wild-type patients by T-cell receptor sequencing and immunohistochemistry for CD45, CD4, CD8, FOXP3, and CD163. In addition, we analyzed seven prostate cancer biopsies that were either BRCA2 or ATM-mutated in comparison with wild-type tumors. Whereas in BRCA1/2 wild-type tumors, immune cells were found predominantly extratumorally, most BRCA2-mutated tumors including one biopsy showed a significantly increased intratumoral immune cell infiltration. The ratio of intratumoral to extratumoral immune cells was considerably higher in BRCA2-mutated tumors for all markers and reached statistical significance for CD4 (p = 0.007), CD8 (p = 0.006), and FOXP3 (p = 0.001). However, the intratumoral CD8 to FOXP3 ratio showed a trend to be lower in BRCA2-mutated tumors suggesting a more suppressed tumor immune microenvironment. Our findings provide a rationale for the future use of immune oncological approaches in BRCA2-mutated prostate cancer and may encourage efforts to target immunosuppressive T-cell populations to prime tumors for immunotherapy.Electronic supplementary materialThe online version of this article (10.1007/s00262-019-02393-x) contains supplementary material, which is available to authorized users.
Biocept’s Target Selector technology is a targeted hotspot mutation panel designed to enrich for mutant targets in a large excess of WT DNA. The test is specific to small regions of interest, is highly sensitive, validated down to 7 mutant copies in a background of 14,000 WT at >98% sensitivity. The ArcherDX Reveal ctDNA test is a 28 gene NGS panel that targets key oncogene activating mutations, drug resistance mutations, in addition to full coverage of TP53. The Reveal ctDNA assay utilizes Anchored Multiplex PCR to enrich, tag, and efficiently capture short ctDNA fragments. Both technologies are designed specifically for use with plasma associated ctDNA. We undertook to evaluate the feasibility of using the ArcherDX Reveal ctDNA 28 NGS panel with the DNA extracted from plasma collected with Biocept’s patented blood collection tube which has been validated at room temperature for 4 days for circulating tumor cells and 8 days for ctDNA. The ability to build complex, targeted libraries, free of chemically induced mutations is of major importance for the detection of the vanishingly rare mutations that can be present in the plasma of cancer patients. We found that high quality NGS libraries were produced from plasma collected and stored in the Biocept blood tube, indicating that little damage occurred to the DNA during preservation. In addition, the two methods were found to be highly concordant and complementary when using both mutation positive and negative patient samples. The Target-Selector assay was the more sensitive, however, the ArcherDX panel revealed several additional mutations not targeted by the Biocept Target Selector assay. Citation Format: Jason C. Poole, Brian Kudlow, Jill Stefanelli, Skyler Mishkin, Anh Pham, Jeff Chen, Veena M. Singh, Josh Stahl, Lyle J. Arnold. A concordance study of the ArcherDX RevealTM ctDNA 28 NGS panel and Biocept’s Target SelectorTM mutation assay using ctDNA collected in Biocept CEE-sureTM blood collection tubes [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 762. doi:10.1158/1538-7445.AM2017-762
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