Biopolymer system for cell recovery from microfluidic cell capture devices

Microfluidic systems for affinity-based cell isolation have emerged as a promising approach for the isolation of specific cells from complex matrices (i.e., circulating tumor cells in whole blood). However, these technologies remain limited by the lack of reliable methods for the innocuous recovery of surface captured cells. Here, we present a biofunctional sacrificial hydrogel coating for microfluidic chips that enables the highly efficient release of isolated cells (99% ± 1%) following gel dissolution. This covalently cross-linked alginate biopolymer system is stable in a wide variety of physiologic solutions (including EDTA treated whole blood) and may be rapidly degraded via backbone cleavage with alginate lyase. The capture and release of EpCAM expressing cancer cells using this approach was found to have no significant effect on cell viability or proliferative potential, and recovered cells were demonstrated to be compatible with downstream immunostaining and FISH analysis.

Abstract 5304: RNA sequencing of circulating tumor cells implicates WNT signaling in pancreatic cancer metastasis

Circulating tumor cells (CTCs) shed into blood from primary cancers include putative precursors that initiate distal metastases. While isolation and molecular analysis of these cells is technically challenging, they may identify cellular pathways that contribute to the blood-borne dissemination of cancer cells. Here, we adapted a microfluidic device for efficient capture of CTCs from an endogenous mouse pancreatic cancer model and subjected CTCs to digital gene expression (DGE) analysis using single molecule RNA sequencing. We identified Wnt2 as enriched in both CTCs and metastatic ascites cells, compared with primary tumors. Expression of Wnt2 in pancreatic cancer cells suppresses anoikis, enhances anchorage-independent sphere formation, and increases metastatic propensity in vivo. The effect of Wnt2 is correlated with fibronectin upregulation, and it is mediated in part through non-canonical Wnt signaling and suppressed by inhibition of the Map3k7 (Tak1) kinase, an integrator of Wnt, BMP and TGF-β signaling. DGE analysis of human pancreatic CTCs reveals significant enrichment for non-canonical Wnt signaling in 5 of 11 cases, with Wnt2 RNA detectable by in situ hybridization in a subset of CTCs. Identifying CTC-enriched transcripts such as Wnt2 may point to pathways that enhance haematogenous metastasis, thus providing novel therapeutic targets to prevent the distal spread of cancer.

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 5304. doi:1538-7445.AM2012-5304

Isolation and characterization of circulating tumor cells from patients with localized and metastatic prostate cancer

Rare circulating tumor cells (CTCs) are present in the blood of patients with metastatic epithelial cancers but have been difficult to measure routinely. We report a quantitative automated imaging system for analysis of prostate CTCs, taking advantage of prostate-specific antigen (PSA), a unique prostate tumor-associated marker. The specificity of PSA staining enabled optimization of criteria for baseline image intensity, morphometric measurements, and integration of multiple signals in a three-dimensional microfluidic device. In a pilot analysis, we detected CTCs in prostate cancer patients with localized disease, before surgical tumor removal in 8 of 19 (42%) patients (range, 38 to 222 CTCs per milliliter). For 6 of the 8 patients with preoperative CTCs, a precipitous postoperative decline (<24 hours) suggests a short half-life for CTCs in the blood circulation. Other patients had persistent CTCs for up to 3 months after prostate removal, suggesting early but transient disseminated tumor deposits. In patients with metastatic prostate cancer, CTCs were detected in 23 of 36 (64%) cases (range, 14 to 5000 CTCs per milliliter). In previously untreated patients followed longitudinally, the numbers of CTCs declined after the initiation of effective therapy. The prostate cancer-specific TMPRSS2-ERG fusion was detectable in RNA extracted from CTCs from 9 of 20 (45%) patients with metastatic disease, and dual staining of captured CTCs for PSA and the cell division marker Ki67 indicated a broad range for the proportion of proliferating cells among CTCs. This method for analysis of CTCs will facilitate the application of noninvasive tumor sampling to direct targeted therapies in advanced prostate cancer and warrants the initiation of long-term clinical studies to test the importance of CTCs in invasive localized disease.

Abstract 1136: Detection and characterization of circulating tumor cells in localized and metastatic prostate cancer patients using CTC-Chip microfluidic technology

Despite recent molecular advances, the treatment of localized and metastatic prostate cancer has changed little in recent decades and it remains a major cause of cancer deaths in men. Localized prostate cancer may be either indolent or invasive, without reliable distinguishing markers, and the absence of tumor tissue from patients with metastatic bone disease has hampered understanding of acquired resistance to primary hormonal therapy. Given the predominant hematogenous spread of prostate cancer, circulating tumor cells (CTCs) may provide an indicator of vascular invasiveness, as well as a source of tumor specimens for molecular analysis, but available technologies have been limited by relatively low sensitivity. Huge strides in engineering at smaller scales have lead to the tremendous progress in microfabricated devices to facilitate both applied and basic research. Applying a multi-disciplinary approach, we have developed a microfluidic technology “CTC-Chip” for diagnosis and monitoring of non-hematological cancers. Using the CTC-Chip, we were able to isolate CTCs in patients with both localized and metastatic prostate cancer. In patients with advanced cancer, CTCs were present at a frequency of 34 CTCs/mL (range 14-653), with a profound decline in numbers during response to hormone withdrawal therapy. Molecular markers, including the characteristic TMPRSS2-ERG translocation, are readily identified in CTCs. In patients with early stage, resectable prostate cancer, we have monitored CTC load in circulation following surgical resection of the primary tumor. CTCs were examined the day following surgical resection, at postoperative day 9, and at greater than 3 months, coincident with scheduled postoperative clinical visits. Longitudinal monitoring of CTCs revealed all CTC-positive cases showed disappearance of CTCs following prostate resection, with some having an immediate decline and others having a delayed (&gt;24 hours) response. No evident differences in tumor pathology or operative procedure distinguished patients with a rapid versus delayed postoperative CTC decline. Dual staining of captured CTCs for PSA and Ki67 indicated a broad range in proliferative index of CTCs among patients with different clinical courses. Thus, the quantitative isolation and analysis of CTCs in both localized and metastatic prostate cancer provides novel insights into early hematogenous dissemination and enables molecular analyses of treatment-responsive and -resistant disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1136.

Parametric analysis of intercellular ice propagation during cryosurgery, simulated using monte carlo techniques

A microscale theoretical model of intracellular ice formation (IIF) in a heterogeneous tissue volume comprising a tumor mass and surrounding normal tissue is presented. Intracellular ice was assumed to form either by intercellular ice propagation or by processes that are not affected by the presence of ice in neighboring cells (e.g., nucleation or mechanical rupture). The effects of cryosurgery on a 2D tissue consisting of 10(4) cells were simulated using a lattice Monte Carlo technique. A parametric analysis was performed to assess the specificity of IIF-related cell damage and to identify criteria for minimization of collateral damage to the healthy tissue peripheral to the tumor. Among the parameters investigated were the rates of interaction-independent IIF and intercellular ice propagation in the tumor and in the normal tissue, as well as the characteristic length scale of thermal gradients in the vicinity of the cryosurgical probe. Model predictions suggest gap junctional intercellular communication as a potential new target for adjuvant therapies complementing the cryosurgical procedure.