ABSTRACT
The metastatic spread of tumors to distant organs is responsible for more than 90% of cancer-related deaths. Malignant cells that detach from a primary tumor and spread through the bloodstream are called circulating tumor cells (CTCs). Analysis of CTCs collected from blood holds promise as a repeatable and minimally invasive alternative for tissue biopsies. However, widespread application of CTCs to clinical practice has been hindered by the fact that CTCs are extremely rare and obscured by a background of billions of normal blood cells. Most existing technologies developed for CTC separation suffer from limited capture due to reliance on antibody selection of specific antigens (ie. EpCAM), or apply excessive shear stresses in microfluidics that disrupt and break apart biologically important CTC clusters. We have developed a flexible micro spring array (FMSA) device for label-free isolation of CTCs based on differences in cell size and deformability. Flexible spring structures were applied as filtration elements that minimize cell disturbance at the micro scale, while maximizing throughput to allow rapid isolation directly from whole blood. Device performance with respect to capture efficiency, purification against contaminating blood cells, and cell viability was characterized through reconstructed model systems using cancer cell lines. CTCs and clusters were then successfully enriched from clinical samples obtained from breast, lung and colorectal cancer patients and characterized using multiplexed immunocytochemical assays. Whole-transcriptome amplification and molecular single-cell analysis using the Smart-Seq protocol revealed an increased expression of stem cell phenotypes within CTC clusters. This observation was confirmed functionally as clusters were observed to be more tumorigenic and metastatic than matched numbers of single CTCs upon re-implantation in mouse models. Technologies that enable widespread adoption of CTC single-cell analysis in the clinic may provide crucial insight into the mechanisms of metastatic disease and allow the development of dynamic patient-specific therapy plans.
BIOGRAPHY
Ramdane Harouaka obtained a B.S. in Mechanical Engineering from the Pennsylvania State University, then embarked on a brief but adventurous career as a field engineer performing reservoir evaluations on remote desert oilfields. The experience of implementing a diverse array of cutting-edge technologies sparked a passion for exploration and highly interdisciplinary research. Upon returning to Penn State he pursued a PhD in Bioengineering to train in microfabrication techniques that facilitated studying and interacting with the human body at the cellular level. During his thesis work he developed a microfluidic system for label-free mechanical capture of circulating tumor cells from cancer patient blood samples. This inspired a postdoctoral fellowship at the University of Michigan, which involved collaborating closely with clinicians to translate microdevices for improved cancer diagnoses in the clinic. At Michigan he isolated rare cancer stem cells for breast cancer trials, developed techniques for single-cell genomic analysis, and was the recipient of the Outstanding Postdoctoral Fellow award. In 2018 he joined the Biotechnology and Bioengineering division at Sandia National Laboratories in Livermore California, where he is currently pursuing research in the national interest at the interface of engineering and bioscience.
