Genetic Mutation Detected in Circulating Tumor Cells

Tissue biopsies from metastatic cancer patients are invasive procedures that are frequently impossible due to the lack of accessible lesions, but a sample is required for genetic analysis.

Circulating tumor cells (CTCs) are neoplastic cells shed from either primary tumors or its metastases that circulate in the peripheral blood of patients with metastatic cancers, and these cells circulating in the blood of metastatic patients could give as accurate a genomic read-out as tumor biopsies.

Oncologists at Thomas Jefferson University (Philadelphia, PA, USA) compared tissue biopsies surgically removed from two patients with triple negative inflammatory breast cancer with CTCs in blood samples. Formalin-fixed paraffin embedded (FFPE) tumor tissues were prepared and DNA was isolated from the fixed cells and genomic analysis was performed using next-generation sequencing (NGS). Immunohistochemical staining was performed on FFPE sections using a monoclonal mouse anti-human tumor protein p53.

The CellSearch System (Janssen Diagnostics; Raritan, NJ, USA) was used to determine if CTCs were present in the patients’ blood and the resulting sample served as a primary enrichment of CTC that was used for single-cell selection using the DEPArray System (Silicon Biosystems, San Diego, CA, USA). The DEParray system is an automated platform that uses dielectrophoresis and a high-quality image-based cell selection system that allows for the identification and recovery of individual cells from heterogeneous samples.

Breast tissue samples from both patients showed a specific mutation in a region of a cancer-driving gene, p53. The scientists studied this mutation in several CTCs isolated from both patients. They found that in several of the CTCs collected, the mutations matched with the tumor biopsy, however in one patient, some of circulating tumor cells had an additional mutation.

The authors concluded that by using a combination of enrichment and CTC selection methods, they were able to isolate uncontaminated CTCs to achieve single-cell molecular analysis. Their results indicate that CTCs are in fact representative of the biology of macro metastatic disease and could represent a noninvasive source of cancer cells to determine genetic markers of the disease progression and reveal the presence of potential drug targets.

Sandra V. Fernandez, PhD, an assistant professor and lead author of the study said, “Our work suggests that these cancer cells in the blood also accurately reflect the genetic status of the parent tumor or its metastases, potentially giving us a new and easy to source of genomic information to guide treatment.” The study was published on October 9, 2014, in the journal Breast Cancer Research.

Related Links:
Thomas Jefferson University 
Janssen Diagnostics 
Silicon Biosystems