36 / 155
Single-Cell Biophysics: Measurement, Modulation, and Modeling
Monday Speaker Abstracts
31
Single-Cell Proteotypic Analysis of Invasive Motility in Glioblastoma
Jung-Ming G. Lin
1,2
, Chi-Chih Kang
2
, Amy E. Herr
1,2
, Sanjay Kumar
1,2
.
2
UC-Berkeley, Berkeley, CA, USA.
1
The UC-Berkeley-UCSF Graduate Program in
Bioengineering, Berkeley, CA, USA,
Cellular invasion into the surrounding tissue is a critical step in many solid tumors. However,
virtually nothing is known about how the protein profile of an individual tumor cell relates to its
propensity to invade and metastasize. One type of cancer characterized by cellular invasion is
glioblastoma (GBM). The extensive tissue infiltration of GBM cells makes complete surgical
resection impossible and contributes to resistance to subsequent radiation and chemotherapy. To
investigate the invasive capability of GBM cells, we present a microfluidic device that correlates
differences in protein expression with cellular speed, persistence and aspect ratio. Our
PDMS/polyacrylamide-based device supports chemotactic migration through channels of tissue-
like stiffness, enabling separation of heterogeneous tumor cell populations based on migration
speed. The isolated cells are then subjected to multi-target single-cell western blotting using the
polyacrylamide device walls as the electrophoretic and immunoblotting matrix. Using this
device, we analyzed patient-derived glioblastoma tumor-initiating cells (TICs), a subpopulation
of GBM with stem-like properties. We show that TICs exhibit surprising heterogeneity with
respect to marker expression, with an apparent enrichment of Nestin and depletion of STAT3 in
the most motile cells. This Nestin enrichment is not observed when immunofluorescence is used
to quantify Nestin expression. Furthermore, we identified correlations between specific
biomarkers within single TICs, which would not have been possible with population-based
assays. Specifically, we discovered a positive correlation between Nestin and β-tubulin,
suggesting the possibility that β-tubulin can also be used as a TIC enrichment marker. Our
system lays the groundwork for the development of single-cell protein profiles of tumor invasion
and metastasis. These profiles would allow for the identification of proteins that can predict
invasive capability, an insight with great fundamental and translational value.