Metastasis is a complex, multistep process that begins with the epithelial-mesenchymal transition (EMT). Circulating tumor cells (CTCs) are believed to have undergone EMT and thus lack or express low levels of epithelial markers commonly used for enrichment and/or detection of such cells. However, most current CTC detection methods only target EpCAM and/or cytokeratin to enrich epithelial CTCs, resulting in failure to recognize other, perhaps more important, CTC phenotypes that lack expression of these markers. Here, we describe a population of complex aneuploid CTCs that do not express cytokeratin or CD45 antigen in patients with breast, ovarian, or colorectal cancers. These cells were not observed in healthy subjects. We show that the primary epithelial tumors were characterized by similar complex aneuploidy, indicating conversion to an EMT phenotype in the captured cells. Collectively, our study provides a new method for highly efficient capture of previously unrecognized populations of CTCs. Significance Current assays for CTC capture likely miss populations of cells that have undergone EMT. Capture and study of CTCs that have undergone EMT would allow a better understanding of the mechanisms driving metastasis.

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Human epidermal growth factor receptor 2 (HER2) gene amplification in circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) might be useful for modifying Herceptin therapy in breast cancer. In the process of investigating the utility of a microfluidic platform for detecting HER2 gene amplification in these cells, we observed novel results on discordance of HER2 status. Peripheral blood (8.5 mL) and bone marrow (BM) (7.5–10 mL) were collected prospectively from patients with clinical stages I–IV breast cancer. Mononuclear cells were recovered, stained with cytokeratin (CK), CD45, and DAPI, and processed through microfluidic channels for fluorescence in situ hybridization (FISH). A ratio of HER2:CEP17 >2 in any CK+/CD45 or CK−/CD45 cell was regarded as positive for HER2 gene amplification. Peripheral blood from 95 patients and BM from 78 patients were studied. We found CK+/CD45−/DAPI+ CTCs in 27.3% of patients. We evaluated HER2 gene amplification by FISH in 88 blood and 78 BM specimens and found HER2+ CTCs in 1 of 9 (11.1%) and HER2+ DTCs (27.2%) in 3 of 11 patients with HER2+ primary tumor. Among patients with a HER2− primary tumor, 5 of 79 had HER2+ CTCs (6.3%) and 14 of 67 had HER2+ DTCs (20.8%). The overall rate of discordance in HER2 status was 15% between primary tumor and CTCs and 28.2% between primary tumor and DTCs. HER2 was amplified in CTCs and DTCs in a portion of both HER2+ and HER2− primary tumors. HER2 discordance was more frequent for DTCs. The clinical implications of evaluating HER2 status in CTCs and DTCs in breast cancer needs to be established in prospective clinical trials. The cell enrichment and extraction microfluidic technology provides a sensitive platform for evaluation of HER2 gene amplification in CTCs and DTCs.

PURPOSE Estrogen receptor (ER) and progesterone receptor (PR) status is prognostic and predictive in breast cancer. Because metastatic breast tumor biopsies are not routinely feasible, circulating tumor cells (CTCs) offer an alternative source of determining ER/PR tumor status. METHODS/PATIENTS Peripheral blood was collected prospectively from 36 patients with metastatic breast cancer. CTCs were isolated using the microfluidic OncoCEE™ platform. Detection was accomplished with an expanded anti-cytokeratin (CK) cocktail mixture and anti-CD45. ER/PR protein expression was assessed by immunocytochemistry (ICC) on the CK+ cells and compared to the primary and/or metastatic tumor (immunohistochemistry: IHC). RESULTS Among the 24 CK+ CTC cases, a concordance of 68% (15/22) in ER/PR status between primary breast tumor and CTCs and 83% (10/12) between metastatic tumor and CTCs was observed. An overall concordance of 79% (19/24) was achieved when assessing CTC and metastatic tumor (primary tumor substituted if metastatic breast biopsy not available). A test sensitivity of 72% and specificity of 100% was identified when comparing CTCs to tumor tissue. Of the 7 discordant cases between CTCs and primary tumor tissue, 2 were concordant with the metastatic biopsy. CONCLUSIONS CTC ER/PR status using the OncoCEE™ platform is feasible, with high concordance in ER/PR status between tumor tissue (IHC) and CTCs (ICC). The prognostic and predictive significance of CTC ER/PR protein expression needs further evaluation in larger trials.

584 Background: Hormone receptor (estrogen receptor [ER] and progesterone receptor [PR]) status in all breast cancer patients is recommended for selection of treatment options. However, the analytical sensitivity of immunohistochemistry (IHC) in detecting low levels of ER/PR is often poor and is likely due to methodological variation. Because biopsy is not often feasible in all patients with recurrent and/or metastatic breast disease, circulating tumor cells (CTCs) offer an attractive alternative source of tumor tissue for determining ER/PR status and can be monitored more readily to enable a more effective course of treatment. Methods: Twenty mL of peripheral blood was collected prospectively from 15 patients diagnosed with late stage metastatic/recurrent breast cancer. CTCs were isolated using the microfluidic OncoCEE platform. A cocktail of antibodies was utilized for CTC capture and detection with an expanded anti-cytokeratin (CK) cocktail mixture and anti-CD45. ER/PR protein expression was assessed by immunocytochemistry (ICC) on the cells captured within the microchannels and compared to IHC performed on the primary tumor or metastatic biopsy. Results: CK+/CD45-/DAPI+ cells were located and assessed for ER/PR ICC. Among the 15 cases, a high concordance (13/15; 87%) in ER/PR status between IHC and ICC results was observed. Two cases were found to be discordant where one was positive by IHC and negative on the CTCs, and the other was negative by IHC and positive on the CTCs. However, both cases that were discordant had low numbers of detected CTCs. Conclusions: There is significant heterogeneity between ER/PR protein expression in CTCs and primary tumor/metastatic biopsy, and this status may change over time due to therapy. ER/PR ICC on CTCs from peripheral blood using the OncoCEE platform is shown to be feasible with high concordance (87%) in ER/PR status between primary tumor/metastatic biopsy (by IHC) and CTCs (by ICC). The significance of heterogeneity at the ER/PR protein level in CTCs ascertaining to the prognosis and predictive response to anti-estrogen therapy needs further evaluation in larger prospective clinical trials.

BACKGROUND: The status of HER2 gene amplification in circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) might provide useful information for monitoring response to trastuzumab therapy, and may provide a basis for consideration of trastuzumab in patients with HER2 negative primary tumors who have HER2 positive CTCs and/or DTCs. The majority of techniques utilized for detection of minimal residual disease are limited in their ability to allow detailed phenotypic and genotypic evaluation of the cells. We report the utility of a microfluidic platform (OncoCEE™,Biocept, San Diego) for detecting HER2 gene amplification in CTCs and DTCs in patients with non-metastatic breast cancer. METHODS: Peripheral blood (10ml) and bone marrow (BM) (1-2ml) were collected from patients with clinical stage I-III breast cancer in acid citrate dextrose solution (BD, Franklin Lakes, NJ) and anti-clumping reagent (OncoCEE-Sure™). Mononuclear cells were recovered using a Percoll density gradient method, incubated with a mixture of 10 primary capture antibodies (Abs), introduced into CEE™ microchannels, stained with fluorescent anti cytokeratin (CK) and CD45 abs and finally processed for fluorescence in situ hybridization (FISH) using probes specific to centromere 17 (spectrum green) and HER2 (spectrum arrange). The ratio of HER2:CEP17 >2.2 in any CK+/CD45- and CK-/CD45- cell was regarded as positive for HER2 gene amplification. RESULTS: Peripheral blood and/or BM from 78 patients (65 BM; 70 blood; 57 matched blood and BM) with T1NO (39), T1N1 (8), T2N0 (12), T2N1 (2), T2N2 (1), T2N3 (3), T3N0 (2), T3N1 (2), T3N2 (1), T4N0(5), T4N1 (3), with HER2+ (n=12) and HER2− (n=58) primary invasive breast tumors were studied. The 12 patients with HER2+ primary tumors had HER2+ DTCs in 3/12 (25%) and HER2+ CTCs in 1/9 (11%) cases respectively. HER2+ DTCs and HER2+ CTCs occurred in 12/55 (24%) and in 4/63 (6%) of the patients with HER2− primary breast tumors. HER2+ CTCs and DTCs occurred simultaneously in only 2 patients and in either blood (3) or BM (13) in the remaining patients. CONCLUSION: 1. The cell enrichment and extraction microfluidic technology (OncoCEE™) provides a sensitive platform for evaluation of HER2 gene amplification of CTCs and DTCs. 2. HER2+ primary tumors were associated with either HER2+ CTCs or DTCs in 25% of the patients. 3. HER2+ CTCs or DTCs occurred in 28% of patients with HER2−primary tumor. 4. Discordant HER2 status was contributed mainly by HER2+ DTCs occurring in HER2 - primary tumors. 5. The clinical significance of evaluating the status of HER2 gene amplification in CTCs and DTCs in the management of patients with breast cancer needs to be evaluated prospectively in larger clinical trials. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-06-04.

Introduction: Hormone receptor (estrogen receptor (ER) and progesterone receptor (PR)) status in all breast cancer patients is recommended by immunohistochemistry (IHC) and is considered standard practice for selection of treatment options. However, the analytical sensitivity of IHC in detecting low levels of ER/PR is often poor and likely due to methodological variation. Because biopsy is not often feasible in all patients presenting with recurrent and/or metastatic breast disease, circulating tumor cells (CTCs) offer an attractive alternative source of tumor tissue for determining ER/PR status and can be monitored more readily to enable a more effective course of treatment. Experimental Design: Twenty ml of peripheral blood was collected prospectively from 14 patients diagnosed with late stage metastatic/recurrent breast cancer. CTCs were isolated using the microfluidic OncoCEETM platform. A cocktail of antibodies was utilized for CTC capture and detection with an expanded anti-cytokeratin (CK) cocktail mixture and anti-CD45. ER/PR protein expression was assessed by immunocytochemistry (ICC) on the cells captured within the microchannels and compared to IHC performed on the primary tumor or metastatic biopsy. Results: CK+/CD45-/DAPI+ cells were located and assessed for ER/PR immunocytochemistry. Among the 14 cases a high concordance (12/14; 86%) in ER/PR status between primary tumor/metastatic biopsy and CTCs was observed. Two cases were found to be discordant where one was positive by IHC and negative on the CTCs and the other was negative on by IHC on the primary tumor/metastatic biopsy and positive on the CTCs. However, both cases that were discordant had low numbers of CTCs detected. Conclusions: There is significant heterogeneity between ER/PR protein expression in CTCs and primary tumor/metastatic biopsy and this status may change over time due to therapy. ER/PR ICC on CTCs from peripheral blood using the OncoCEETM platform is shown to be feasible with high concordance (86%) in ER/PR status between primary tumor/metastatic biopsy (by IHC) and CTCs (by ICC). The significance of heterogeneity at the ER/PR protein level in CTCs ascertaining to the prognosis and predictive response to anti-estrogen therapy needs further evaluation in larger prospective clinical trials. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4568. doi:1538-7445.AM2012-4568

Introduction: The measurement of circulating tumor cells (CTCs) in blood generally requires either anti-EpCAM for capture, anti-cytokeratin (CK) for detection, or both. However, EpCAM and CK are absent in some tumor cells, and both may be down-regulated during neoplastic progression or during epithelial-to-mesenchymal transition (EMT). Here we show capture on a micro-fluidic system using single or multiple antibodies, and CTC detection with CEE-Enhanced (CE), a novel in situ staining method that fluorescently labels the capture antibodies bound to the CTCs. Methods: Buffy coat cells isolated from 8 mL of blood were pre-incubated with either anti-EpCAM alone or with a mixture of antibodies to epithelial and mesenchymal cell surface antigens. CTCs were captured on a micro-fluidic channel. Identification of CTCs was determined with anti-CK and with CE to detect cells with the capture antibodies bound to the cell surface antigens. All cells scored as positive for CK or CE were, by definition, CD45-negative and DAPI-positive. Results: Using anti-EpCAM alone for capture, significantly more CTCs were detected by CE staining than with anti-CK in breast and prostate cancers. This indicated that CK-negative CTCs were captured but not detected and that some EpCAM-positive CTCs were CK-negative. Results using capture antibody mixtures varied from sample to sample but gave up to 2-fold higher CK-positive cells than anti-EpCAM only, and as much as 4-fold higher CE-positive cells. Control blood from healthy donors was CK and CE-negative. All CK-positive cells co-stained with CE, as determined with different fluorescent labels. In a clinical study of stage IV breast cancer, CTCs were isolated with an antibody mixture and sequentially stained with CK and CE. Fifteen of 24 samples (63%) contained CK-positive cells (range 1-60 CTCs) while 24 of 24 samples (100%) contained additional CE-positive cells (range 1-41; median=11; Wilcoxon test, p=0.02). The modest correlation coefficient (r = 0.57, p=0.004) for the number of CE-positive and CK-positive cells in each sample suggests that one or more different phenotypes of CTCs were being detected. Amplified Her2 was detected by FISH in isolated CK-positive CTCs, and also in CK-negative, CE-positive CTCs from Her2-positive patients, indicating these were tumor cells. Conclusions: The CEE-Enhanced staining technology enables the detection of CK-negative CTCs. This novel detection method, based on the in situ labeling of antibodies used for capture, greatly expands single and multi-antibody approaches to the study of rare circulating cells. Specifically, this allows the exploration and study of circulating cells not expressing CK such as highly de-differentiated tumor cells, stem cells or those tumor cells undergoing EMT. The clinical significance of these CK-negative CTCs is under investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5172. doi:10.1158/1538-7445.AM2011-5172