Circulating Tumor Cells Provide Current Disease Status

Circulating tumor cells (CTCs) may be a promising alternative to biopsies and a noninvasive source of tumor materials for biomarker assessment.

The capture efficiency of two biochip platforms for CTCs was tested using whole blood spiked with tumor cell lines to detect biomarkers such as epidermal growth factor receptor (EGFR) protein expression from patients with lung cancer and human epidermal growth factor receptor 2 (HER2) expression or amplification in patients with metastatic breast cancer.

The blood tests were performed on the Veridex CellSearch platform, (Raritan, NJ, USA), which has built in ready-to-use ferrofluid-based capture reagent and immunofluorescent reagents. Under the tested conditions, this platform and the newer biochip platforms were equally efficient, but capture efficiency was dependent on epithelial cell adhesion molecule (EpCAM) expression.

It was reported that captured CTCs were amenable to biomarker analyses such as HER2 status, quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) for breast cancer-subtype markers. The captured CTCs were useful in Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation detection and EGFR staining by immunofluorescence. In patients with HER2-positive breast cancer, HER2 status in CTCs and tumor tissue generally correlated well. However, in one patient subset, HER2 status changed from the primary tumor at diagnosis. This finding indicates that in some cases, CTCs may offer a real-time view of a patient's biomarker status that is different from diagnostic tissue. The findings were presented at the Fourth American Association for Cancer Research's International Conference on Molecular Diagnostics in Cancer Therapeutic Development that was held during September 23–27, 2010, in Denver (CO, USA).

Siminder Kaur Atwal, Ph.D., a scientist at Genentech, (South San Francisco, CA, USA), said, "The basic idea is that CTCs can provide real-time information about a patient's current disease state, acting as a 'liquid biopsy.' They are much less invasive than tumor biopsies because they can be detected from a blood draw and do not require surgical intervention." Future studies will focus on evaluating different detection and capture methods with a particular emphasis on tumor types with a low EpCAM expression.

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