Prognostic value of preoperative circulating tumor cells counts in patients with UICC stage I-IV colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer death worldwide. There is an urgent need to identify prognostic markers for patients undergoing curative resection of CRC. The detection of circulating tumor cells in peripheral blood is a promising approach to identify high-risk patients with disseminated disease in colorectal cancer. This study aims to evaluate the prognostic relevance of preoperative CTCs using the Cellsearch® system (CS) in patients, who underwent resection with curative intent of different stages (UICC I-IV) of colorectal cancer. Out of 91 Patients who underwent colorectal resection, 68 patients were included in this study. CTC analysis was performed in patients with CRC UICC stages I-IV immediately before surgery. Data were correlated with clinicopathological parameters and patient outcomes. One or more CTCs/7.5 mL were detected in 45.6% (31/68) of patients. CTCs were detected in all stages of the Union of International Cancer Control (UICC), in stage I (1/4, 25%), in stage II (4/12, 33.3%), in stage III (5/19, 26.3%) and in stage IV (21/33, 63.6%). The detection of ≥ 1 CTCs/ 7.5ml correlated to the presence of distant overt metastases (p = 0.014) as well as with shorter progression-free (p = 0.008) and overall survival (p = 0.008). Multivariate analyses showed that the detection of ≥ 1 CTCs/ 7.5ml is an independent prognostic indicator for overall survival (HR, 3.14; 95% CI, 1.18-8.32; p = 0.021). The detection of CTCs is an independent and strong prognostic factor in CRC, which might improve the identification of high-risk patients in future clinical trials.

RHAMM splice variants confer radiosensitivity in human breast cancer cell lines

Biomarkers for prognosis in radiotherapy-treated breast cancer patients are urgently needed and important to stratify patients for adjuvant therapies. Recently, a role of the receptor of hyaluronan-mediated motility (RHAMM) has been suggested for tumor progression. Our aim was (i) to investigate the prognostic value of RHAMM in breast cancer and (ii) to unravel its potential function in the radiosusceptibility of breast cancer cells. We demonstrate that RHAMM mRNA expression in breast cancer biopsies is inversely correlated with tumor grade and overall survival. Radiosusceptibility in vitro was evaluated by sub-G1 analysis (apoptosis) and determination of the proliferation rate. The potential role of RHAMM was addressed by short interfering RNAs against RHAMM and its splice variants. High expression of RHAMMv1/v2 in p53 wild type cells (MCF-7) induced cellular apoptosis in response to ionizing radiation. In comparison, in p53 mutated cells (MDA-MB-231) RHAMMv1/v2 was expressed sparsely resulting in resistance towards irradiation induced apoptosis. Proliferation capacity was not altered by ionizing radiation in both cell lines. Importantly, pharmacological inhibition of the major ligand of RHAMM, hyaluronan, sensitized both cell lines towards radiation induced cell death. Based on the present data, we conclude that the detection of RHAMM splice variants in correlation with the p53 mutation status could help to predict the susceptibility of breast cancer cells to radiotherapy. Additionally, our studies raise the possibility that the response to radiotherapy in selected cohorts may be improved by pharmaceutical strategies against RHAMM and its ligand hyaluronan.

Abstract 5693: Low coverage genome-wide sequencing of cell-free DNA enables detection, therapeutic monitoring, and characterization of copy number alterations in patients with solid tumors

Circulating tumor DNA (ctDNA) has been detected in the blood of patients with many cancer types and is thought to reflect the combined genetic profile of the primary tumor and metastases. The majority of studies into “liquid biopsies” have focused on detecting focal events including single nucleotide variants, fusions, and specific copy number alterations (CNAs); however, these assays are limited to mutations occurring in targeted regions and require deep sequencing. The objective of this study was to use low coverage, genome-wide sequencing of cell-free DNA (cfDNA) to evaluate the frequency, distribution, and persistence of genome-wide CNAs in the plasma of patients with solid tumors. cfDNA was isolated from a total of 203 plasma aliquots from 72 patients diagnosed with a variety of solid tumors. For almost half of the patients, multiple collections were available (range: 2-13) to enable longitudinal monitoring of treatment response. Greater than 25% of baseline cfDNA samples showed evidence of one or more CNAs and greater than 40% of patients had a CNA detected in at least one sample. Among patients with longitudinal monitoring, greater than 35% of individuals showed evidence of CNAs at baseline and approximately 25% of samples showed similar evidence in subsequent sampling. Collectively, CNAs were detected on all autosomes, suggesting that genome-wide profiling is necessary to fully assess CNA distributions. Additionally, we devised a metric which quantified the level of genomic instability. This metric, termed the genomic instability number (GIN), was associated with disease classification. In patients capable of longitudinal monitoring, GIN values were observed concomitant with therapeutic response (including, interestingly, response to immunotherapy) or disease progression and may provide information earlier than standard imaging-based methods. In addition, total cfDNA amount was evaluated as a predictor. When analysis was performed across all patients, there was a poor correlation between total cfDNA amount and the GIN; however, total cfDNA amount was strongly correlated with the cumulative abundance of CNA events within individual patients, suggesting that the CNAs detected in the cfDNA were derived from the additional genetic material contributed by the tumor. These data demonstrate the feasibility of detecting ctDNA in a significant portion of cancer patients solely on the basis of low coverage CNA profiling. Further, the nature of CNA events observed varied both between patients and across longitudinal samples from individual patients, suggesting potential for monitoring therapy response or disease progression. This study suggests that genome-wide CNA profiling may be useful alone or as a complement to standard variant detection strategies in the development of liquid biopsy technologies.

Citation Format: Christopher K. Ellison, Aaron M. Goodman, Sabine Riethdorf, Amin R. Mazloom, Lisa Tran, Prachi Nakashe, Erin McCarthy, Tobias Gorges, Alexander Stein, Julia Quidde, Daniel S. Grosu, Mathias Ehrich, Taylor J. Jensen, Klaus Pantel, Razelle Kurzrock. Low coverage genome-wide sequencing of cell-free DNA enables detection, therapeutic monitoring, and characterization of copy number alterations in patients with solid tumors [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 5693. doi:10.1158/1538-7445.AM2017-5693

Abstract 503: Molecular characterization of in vivo isolated EpCAM-positive circulating tumor cells in breast cancer

Introduction: In the early stages of cancer, the chance to detect rare CTCs is increasing by increasing the sample volume. The aim of our study was to evaluate the diagnostic sensitivity of a novel clinical device for the in-vivo isolation of EpCAM-positive CTCs (CellCollectorTM, GILUPI, GmBH), by using highly sensitive RT-qPCR molecular assays.

Patients and methods: 29 breast cancer patients without overt metastases before the beginning of adjuvant chemotherapy (M0), 26 breast cancer patients with overt metastases before starting of therapy (M1) and 12/26 of them before the second cycle of therapy (M2), as well as 18 healthy donors participated in the study. After in-vivo isolation, total RNA was extracted from captured cells, lysed in Trizol, followed by cDNA synthesis. RT-qPCR was used for the molecular characterization of captured cells, for: CK-19, HER-2, TWIST1, VEGF, ER, PR, EGFR, CD44, CD24, and ALDH1, while B2M was used as a reference gene. Peripheral blood was also collected for CTC analysis by the FDA cleared CellSearchTM system. In addition, immunofluorescence staining of cytospins was performed and screened for CTCs using the ARIOL system, using ER, HER2, CK (8, 18, 19) and CD45 for CTC identification.

Results: Results are shown in Table 1. At least one gene was expressed in 10(34.5%) of M0, 15(57.7%) of M1 and 4(33.3%) of M2 patient groups, but in none of healthy donors 0/18(0%). CellSearchTM gave positive results in 5(17.2%) of M0, 10(38.5%) of M1 and 0(0%) of M2. Immunofluorescence (Ariol system) was positive for ER, HER2, CK (8, 18, 19) in 5/15(33.3%) M0, in 4/12(33.3%) M1 and in 1/7(14.3%) M2 groups. Table 1.Gene expression in CTCHealthy N = 18M0 N = 29M1 N = 26M2 N = 12CK-190 (0%)6(20.7%)6 (23.1%)2 (16.7%)HER20 (0%)2 (6.9%)0 (0%)0 (0%)ER0 (0%)2 (6.9%)0 (0%)0 (0%)PR0 (0%)0 (0%)0 (0%)0 (0%)EGFR0 (0%)0 (0%)0 (0%)0 (0%)TWIST10 (0%)1 (3.4%)0 (0%)2 (16.7%)VEGF0 (0%)3 (10.3%)5 (19.2%)1 (8.3%)CD44+/CD24−,0 (0%)4 (13.8%)3 (11.5%)1 (8.3%)ALDH1high/CD24−,0 (0%)2 (6.9%)8 (30.8%)1(8.3%)

Conclusions: In-vivo isolation of CTC is minimally invasive, and in combination with high specific and sensitive RT-qPCR assays for CTC detection and molecular characterization seems promising. Comparison studies with the CellSearch and immunofluorescence have shown poor agreement. These results should be validated in large patient cohorts, and in respect to the clinical outcome.

Citation Format: Areti D. Strati, Martha Zavridou, Galateia Kallergi, Eleni Politaki, Tobias Gorges, Andra Kuske, Anna-Lena Bohnen, George Koutsodontis, Amanda Psyrri, Klaus Lucke, Vasilis Georgoulias, Klaus Pantel, Evi Lianidou. Molecular characterization of in vivo isolated EpCAM-positive circulating tumor cells in breast cancer. [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 503.