The propensity of invasive circulating tumor cells (iCTCs) in metastatic progression and therapeutic responsiveness.

Circulating tumor cells (CTCs) are important clinical indicators of metastatic progression and treatment efficacy. However, because of their low number and heterogeneity, reliable patient-derived CTC models are not readily available. We report here the isolation and characterization of the invasive population of CTCs, iCTCs, from blood of 10 patients with epithelial ovarian cancer (EOC) and one pancreatic cancer patient based on the avidity of tumor cells toward an artificial collagen-based adhesion matrix (CAM), in comparison with tumor progenitor (TP) cells isolated from tumor cell lines, tumors and ascites from EOC patients. CAM-avid cells identified to be iCTCs were indistinguishable with TP cells using either functional CAM uptake or surface markers (seprase and CD44). In addition, iCTCs were characterized using peritoneal and spontaneous metastasis models in vivo to evaluate their metastatic propensity and therapeutic response. TP cells and iCTCs had a doubling time of about 34-42 hours. TP cells were rare (<3.5%) in most patient-derived specimens, however, iCTCs emigrated into blood, at a high frequency, 64.2% (n = 49). Approximately 500 patient-derived iCTCs recapitulated formation of iCTCs in mouse blood and formed micrometastases in the liver and/or lung, a degree of metastatic spread equivalent to the inoculation of 5 × 105 bulk tumor cells isolated from ascites and tumors. iCTCs were shown to be novel therapeutic targets for blocking metastasis using the reduced formation of iCTCs and micrometastases by RNAi, peptides, and monoclonal antibodies against seprase.

iCTC drug resistance (CDR) Testing ex vivo for evaluation of available therapies to treat patients with epithelial ovarian cancer.

GOALS: Management of epithelial ovarian cancer (EOC) could use serial measurements of invasive circulating tumor cells (iCTCs) for monitoring therapeutic response and early detection of disease progression/recurrence. Goals of this study are to develop an iCTC drug resistance (CDR) assay and to evaluate clinical significance of patient-derived, cultured iCTCs in selecting available therapies. METHODS: The CDR assay using Taxol-Carboplatin and eight other EOC drugs at the concentration used for patients was performed. Blood was donated by six patients before primary Taxol-Carboplatin chemotherapy, one recurrent patient, six patients during and after their course of chemotherapy, and two patients with benign disease for procedure control. CDR score above and below 100 indicates sensitivity and resistance, respectively, to that drug. RESULTS: Five of six pre-therapy samples had >20 iCTCs/>111 CDR for Taxol-Carboplatin sensitivity, and one had 40 iCTCs/23 CDR for resistance. The recurrent sample had 58 iCTCs/5 CDR for resistance. Four of six post-therapy patients had iCTCs decreased to 0/>153 CDR indicating sensitivity, while two patients had >45 iCTCs/<85 CDR indicating resistance. The patients' treatment history and follow-up confirmed that patients were in response or remission when iCTCs were sensitive to Taxol-Carboplatin, and patients were in relapse or recurrence when iCTCs were resistant to Taxol-Carboplatin. CONCLUSION: Further investigation on the CDR assay is warranted to examine its use in selecting drugs before treating a patient.

Vita-Assay™ Method of Enrichment and Identification of Circulating Cancer Cells/Circulating Tumor Cells (CTCs).

The ability to capture, enrich, and propagate circulating cancer cells/circulating tumor cells (CTCs) for downstream analyses such as ex vivo drug-sensitivity testing of short-term cultures of CTCs, single cell sorting of CTCs by fluorescence activated cell sorting (FACS), animal injection tumor and/or metastasis formation studies, next generation sequencing (NGS), gene expression profiling, gene copy number determination, and epigenomic analyses is of high priority and of immense importance to both the basic research and translational/clinical research communities. Vitatex Inc.'s functional cell separation technology, constructed as Vita-Assay™ (AG6W, AN6W, AR6W) culture plates, is based on the preferential adhesion of invasive rare blood cells of tissue origin to a tissue or tumor microenvironment mimic-the so-called cell adhesion matrix (CAM), which has a demonstrated ability to enrich viable CTCs from blood up to one-million fold.The CAM-scaffold allows for the functional capture and identification of invasive CTCs (iCTCs) including invasive tumor progenitor (TP) cells from cancer-patients' blood. CAM-captured CTCs are capable of ingesting the CAM (CAM+) itself. Green and red fluorescent versions of Vita-Assay™ (AG6W and AR6W) allow for direct visualization of CAM-uptake by cancer cells. Vita-Assay™ CAM-enrichment has allowed for sensitive multiplex flow cytometric and microscopic detection of iCTCs from patients with cancers of the breast, ovary, prostate, pancreas, colorectum, and lung; it has also been successfully utilized for ex vivo drug-sensitivity testing of ovarian-cancer patient CTCs. The CAM enrichment method is equally suitable for the separation of iCTCs and TP cells in ascites and pleural fluid.

Treatment monitoring of patients with epithelial ovarian cancer using invasive circulating tumor cells (iCTCs).

GOALS: Contemporary management of epithelial ovarian cancer (EOC) uses biomarkers to monitor response to therapy. This study evaluates the role of invasive circulating tumor cells (iCTCs) in monitoring EOC treatment in comparison with serum cancer antigen 125 (CA125). METHODS: Molecular and microscopic analyses were used to identify seprase and CD44 as tumor progenitor (TP) markers. The iCTC flow cytometry assay was optimized using blood donated by 64 healthy donors, 49 patients with benign abdominal diseases and 123 EOC patients. Serial changes in iCTCs and CA125 were measured in 129 blood and 169 serum samples, respectively, from 31 EOC patients to assess their concordance during therapy and their relationship with risk of progressive disease (PD). RESULTS: The assay had 97% specificity and 83% sensitivity for detecting iCTCs in blood of EOC patients. iCTCs were detected in each monitoring patient (31/31, 100%) and in 110 of the 129 blood samples (85.3%). The concordance between changes in iCTCs/CA125 levels and changes in the intervals associated with no evidence of disease (NED) were markedly stronger (specificity: CA125 93.8%; iCTCs 90.6%), whereas increases in iCTCs (79.5%) were more sensitive than increases in CA125 (67.6%) to predict PD or relapse. Among the six patients who had greater than 6 measurements, iCTCs but not CA125 antedated changes in clinical status from PD to NED during and after chemotherapy and predated relapse. CONCLUSION: Serial measurements of iCTCs could predict therapeutic responsiveness in 31 EOC patients who underwent standard taxol/carboplatin therapy.

Prognostic analysis of invasive circulating tumor cells (iCTCs) in epithelial ovarian cancer.

GOALS: Circulating tumor cells (CTCs) have been introduced as a biomarker in detecting advanced epithelial ovarian cancer (EOC). The goals are to examine the prevalence of the invasive subpopulation of CTCs (iCTCs) in patients at high risk of EOC and to compare this biomarker to serum CA125. METHODS: We used a unique cell adhesion matrix (CAM)-based, functional cell enrichment and identification platform to isolate iCTCs from 129 preoperative patients. We confirmed the identity of iCTCs using positive epithelial (Epi+) markers and negative hematopoietic lineage (HL-) markers. Sensitivity and specificity of the assays were examined and iCTCs/CA125 were correlated with overall survival (OS), progression-free survival (PFS) and clinical parameters. RESULTS: We found a 41.2% sensitivity, 95.1% specificity and 77.8% positive predictive value (PPV) of the iCTC assay in detecting patients with stage I and II EOC malignancy, and a 83% sensitivity and 97.3% PPV in detecting all stages of EOC malignancy. However, a positive CA125 test provided weak evidence to detect stage I and II malignancy (61.6% PPV) and all EOC (92.1% PPV), because of its 76.2% specificity. A significantly stronger concordance in OS and PFS of clinical factors (tumor stage, debulking and platinum sensitivity) was noted for elevated iCTCs than for serum CA125. CONCLUSION: The CAM-initiated CTC enrichment/identification method enabled the detection of early stage EOC. iCTCs were better correlated with worse OS and PFS, more specific and better PPV than CA125 in detecting EOC malignancy in patients at high risk of EOC.

Transcriptional regulation of seprase in invasive melanoma cells by transforming growth factor-ß signaling.

The tumor invasive phenotype driven by seprase expression/activity has been widely examined in an array of malignant tumor cell types; however, very little is known about the transcriptional regulation of this critical protease. Seprase (also named fibroblast activation protein-α, antiplasmin-cleaving enzyme, and dipeptidyl prolyl peptidase 5) is expressed at high levels by stromal fibroblast, endothelial, and tumor cells in a variety of invasive tumors but is undetectable in the majority of normal adult tissues. To examine the transcriptional regulation of the gene, we cloned the human seprase promoter and demonstrated that endogenous seprase expression and exogenous seprase promoter activity are high in invasive melanoma cells but not in non-invasive melanoma cells/primary melanocytes. In addition, we identified a crucial TGF-ß-responsive cis-regulatory element in the proximal seprase promoter region that enabled robust transcriptional activation of the gene. Treatment of metastatic but not normal/non-invasive cells with TGF-ß1 caused a rapid and profound up-regulation of endogenous seprase mRNA, which coincided with an abolishment of the negative regulator c-Ski, and an increase in binding of Smad3/4 to the seprase promoter in vivo. Blocking TGF-ß signaling in invasive melanoma cells through overexpression of c-Ski, chemically using SB-431542, or with a neutralizing antibody against TGF-ß significantly reduced seprase mRNA levels. Strikingly, RNAi of seprase in invasive cells greatly diminished their invasive potential in vitro as did blocking TGF-ß signaling using SB-431542. Altogether, we found that seprase is transcriptionally up-regulated in invasive melanoma cells via the canonical TGF-ß signaling pathway, supporting the roles of both TGF-ß and seprase in tumor invasion and metastasis.

Breast cancer bone metastasis mediated by the Smad tumor suppressor pathway.

TGF-beta can signal by means of Smad transcription factors, which are quintessential tumor suppressors that inhibit cell proliferation, and by means of Smad-independent mechanisms, which have been implicated in tumor progression. Although Smad mutations disable this tumor-suppressive pathway in certain cancers, breast cancer cells frequently evade the cytostatic action of TGF-beta while retaining Smad function. Through immunohistochemical analysis of human breast cancer bone metastases and functional imaging of the Smad pathway in a mouse xenograft model, we provide evidence for active Smad signaling in human and mouse bone-metastatic lesions. Genetic depletion experiments further demonstrate that Smad4 contributes to the formation of osteolytic bone metastases and is essential for the induction of IL-11, a gene implicated in bone metastasis in this mouse model system. Activator protein-1 is a key participant in Smad-dependent transcriptional activation of IL-11 and its overexpression in bone-metastatic cells. Our findings provide functional evidence for a switch of the Smad pathway, from tumor-suppressor to prometastatic, in the development of breast cancer bone metastasis.