ID #693 Medulloblastoma circulating tumor cell clusters are molecularly and functionally distinct from their corresponding primary brain tumor cells
Martha Stewart, Jingbo Liu, Isabella Gershon, Hongying Zhang, Franklin Chien, Yuhong Du, Haian Fu, Tevhide Ozkaya, A Fatih Sarioglu, Tobey MacDonaldAbstract
Background
We present a label-free approach for collecting medulloblastoma (MB) circulating tumor cell clusters (CTCCs) from patient blood and CSF. We hypothesize that captured CTCCs represent a sub-clonal population of cells within the primary tumor with stem-like properties that drive treatment resistance and relapse.
Objective
To compare the genetic, metabolic, and drug-responsiveness of MB-CTCCs and their corresponding primary MB tumor cells.
Methods
Primary Group 3 MYC-amplified MB patient cells (BT52) were dissociated from the tumor and their corresponding CTCCs (BT52-CTCCs) were collected from the patient’s blood and established in culture. These were then molecularly validated and compared by sequencing whole genome DNA (WGS) and single cell RNA (scRNA-seq). Baseline metabolic characteristics including oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were assessed using the Seahorse Mitochondrial Stress Test. Drug sensitivity using high throughput screening (HTS) with over 2000 drugs was performed through the Emory Chemical Biology Discovery Center (ECBDC).
Results
WGS confirmed matching DNA copy number variations for BT52 and BT52-CTCCs, while scRNA-seq revealed distinct differences in gene expression. BT52-CTCCs had a higher maximum respiratory capacity than BT52s as measured by OCR (36.68 vs 28.22 pmol/min, p = 0.0072) and basal respiration (34.33 vs 31.88 pmol/min, p = 0.0148). BT52 cells had a higher ECAR than BT52-CTCCs through all phases of the mitochondrial stress test (16.93 vs 8.52 mpH/min, p < 0.0001). BT52-CTCCs showed significant resistance to some key drugs used for the treatment of MB. Molecular and functional analysis of BT52 vs. BT52-CTCCs in response to treatment to select investigational drugs is ongoing and will be presented.
Conclusions
Preliminary data suggests MB primary and CTCCs, while similar in genomic and transcriptomic profiles, significantly differ metabolically, functionally and in response to drugs in vitro. MB-CTCCs may represent a critical sub-clonal population that can mediate drug resistance.