Circulating tumor cells (CTCs) are tumor cells circulating freely in the peripheral blood of patients. The characterization of CTCs is considered as a real-time “liquid biopsy” that provides an ongoing picture of a patient’s cancer status, offering valuable insight into personalized anticancer therapy.

CTCs are very rare and highly heterogeneous, possessing tumor-specific antigenic and genetic characteristics. One of the most commonly used techniques to isolate CTCs is based on the enrichment of tumor cells that express epithelial cell adhesion molecules (EpCAM). This approach, however, can overlook CTC subpopulations that have undergone an epithelial-mesenchymal transition (EMT). It is believed that this EMT process allows the dissemination of CTCs from primary tumors into the circulation. During the EMT process, CTCs lose their epithelial characteristics and acquire more mesenchymal-like phenotypes.

QIAGEN has developed an advanced system that allows enrichment of these cancer cell subtypes from patient blood samples. To accomplish this, we use an antibody-conjugated magnetic bead isolation followed by molecular profiling of captured CTCs. This innovative approach is based on a unique mix of antibodies directed against various tumor cell-associated antigens. By using this technique, you will be able to identify cellular changes in antigen profiles once they develop an EMT or tumor stem cell phenotype, thereby ensuring that your enrichment includes these potentially crucial cells for analysis. This system has been widely used in characterizing cancer progression for targeted therapies.

In a recent investigation from the lab of Dr. Sabine Kasimir-Bauer, Maren Bredemeier and colleagues used the panel AdnaTest EMT-2/Stem Cell Select (QIAGEN Hannover GmbH, Germany) to enrich and profile the expression of 46 genes in CTCs of metastatic breast cancer (MBC) patients. The study was based on 2×5 ml blood from 45 MBC patients and 20 healthy controls, collected at the time of disease progression (T0) and at 2 consecutive clinical stagings (T1 and T2).

One interesting finding is that the multidrug resistant protein gene MRP1 showed a significant difference in expression in overall responders to treatment vs overall nonresponders. In order of significance, VEGFR1, keratin (KRT) 19, EGFR, MET1, ALDH, progesterone receptor (PR), UPA, cathepsin D, KIT1 and Ki67 were differentially expressed in CTCs of patients who had developed liver metastasis as compared to patients without liver metastasis. The patients with liver metastasis showed a significantly lower level of estrogen receptor (ER), PR, HER2, mammaglobin and KRT19 compared to other patients. These preliminary results indicated that CTCs can not only be used as a monitoring tool to guide anticancer therapy, but also allow prediction of the site of metastasis, which may enable a more precise therapeutic decision.

To get more information about this application in MBC research, visit Poster 19, Section 23, at 1 p.m. – 5 p.m., on Sunday, Apr 17, 2016 at AACR in New Orleans.

Find more details about our activities at AACR.

Liquid biopsies show promise for cancer research, but technical challenges remain

Preparing for this year’s annual meeting of the American Association for Cancer Research (AACR), we’ve been thinking about some of the most promising recent technology trends in oncology. One of our favorites is the advances in liquid biopsies as a way to earlier monitor cancer progression, and get a better sense of the genetic variation or expression profile present in a primary tumor or metastatic sites.

Most liquid biopsy studies look for one of three materials: cell-free DNA (cfDNA), circulating tumor cells (CTCs), or exosomes. As its name suggests, cfDNA is the genetic material released into the bloodstream from tumor cells that get lysed during apoptosis or some other process. CTCs are intact cells; in addition to the genetic information they can reveal about a tumor, they’re appealing because they may be cultured for a more sophisticated, longer-term analysis of how these cells function. Exosomes are vesicles released by cells as part of a cell-to-cell signaling network, among other important functions. They may contain RNAs or proteins produced by tumors or other cancerous cells. As scientists make inroads in liquid biopsy studies, it is becoming clear that a comprehensive picture of cancer requires information from as many of these sources as possible.

The biggest challenges with liquid biopsies right now involve finding signal in the noise. This occurs in two different phases: first, when blood or plasma is originally drawn from a patient. The cfDNA, CTCs, and exosomes from cancer cells are wildly outnumbered by material from healthy cells. Typically, liquid biopsies yield vanishingly small samples of interest for cancer research; significant efforts are underway to help solve this problem. A related challenge takes place in data analysis, where again the signal, identifying the driver variant or elucidating mechanisms driving the expression profile, from DNA or cells originating from a tumor can be very difficult to find in the wild-type noise. Analysis and interpretation solutions are being used to overcome this challenge as well.

We believe that liquid biopsies have the potential to transform the diagnosis and treatment of cancer patients. We’re delivering solutions that can help scientists conduct, analyse, and interpret liquid biopsy studies with greater precision and reliability.

We look forward to hearing more about this topic at AACR.
For additional updates, please visit the Biomarker Insights blog or see the schedule for our activities at AACR.