Quantifying EpCAM heterogeneity of circulating-tumor-cells (CTCs) from small cell lung cancer (SCLC) patients.

Abstract

e20091 Background: Tumor heterogeneity and evolution of SCLC is poorly defined. Serial longitudinal interrogation of tumor heterogeneity from CTCs detected in peripheral blood patient (pt) samples is a potential strategy to address this gap in knowledge. However, existing technology is generally limited to the capture and enumeration of CTCs, without a high-throughput method to quantify phenotypic properties. Here, we evaluated a novel nanotechnology platform – nanoparticle-mediated magnetic ranking cytometry (MagRC) to profile SCLC CTCs by EpCAM protein expression. Methods: Blood samples from 20 SCLC pts were processed through the MagRC platform. Magnetic nanoparticles conjugated with anti-EpCAM antibodies were incubated with whole blood samples then introduced into the MagRC device where CTCs are sorted by differently sized nickel micromagnets within microfluidic channels. Captured CTCs are ranked into 8 zones that correlate with EpCAM expression levels (zone 1 = highest to 8 = lowest). For 8 pts, all samples were processed at a 1mL/hr flow rate (fr), and for 12 pts, a 0.5mL/hr fr was also studied; 66% of all chips were processed at a 1ml/hr fr and 34% at a 0.5ml/hr fr. The average zone for each chip was compared to the flow rate, age, and stage (extensive-stage (ES) vs limited-stage (LS)). The differences were tested using the Wald test within the linear mixed effects model. Results: Among 20 pts, 11 were ES; 9 were LS. Median age at diagnosis was 69 years old (yo); 65% were male. We detected CTCs in 12 of 20 pts (60%), similar to other studies. When comparing the MagRC-ranked EpCAM zone, the 0.5mL/hr fr demonstrated a lower median zone (4.3 vs 6.5; p < 0.001) as compared to the 1mL/hr rate. Interestingly, pts > 65 yo had a higher median zone (6.2 vs. 3.5; p = 0.019) compared to those ≤65 yo. The effect remained significant after controlling for flow rate (p = 0.002). No EpCAM zone difference was detected between ES and LS. Conclusions: We demonstrate the ability of MagRC to quantify EpCAM expression levels of CTCs from SCLC pts. We observed a higher MagRC zone (i.e. lower EpCAM expression) from pts > 65 yo. This observation requires validation in larger datasets along with continued investigation into the biology of SCLC CTCs.