Abstract 3066: Direct detection and enumeration of circulating tumor cells (CTCs) in blood by CastRT-qPCR

Abstract

Abstract Statistical data suggest that only approximately 25% of cancer patients will respond to the same treatment. Enumeration and molecular characterization of circulating tumor cells (CTCs) promise to be valuable for cancer cell diagnosis, survival prognosis, and treatment guidance. However, CTCs are very rare. There is no sensitive and specific assay available for analyzing CTCs from whole blood without extensive enrichment processes. Sample enrichment causes target cells loss, expensive and time-consuming. Here we report a highly specific competitive allele-specific TaqMan-based RT-qPCR (castRT-qPCR) for rare copies of DNA mutation detection. CastPCR can detect rare copies of mutant alleles for up to one in 10 million with a wide dynamic range of more than 6-log orders and <5 copy sensitivity. We have successfully designed and validated cast-PCR assays for more than 80 cancer-related SNPs of KRAS, EGFR, BRAF, KIT, pTEN, p53 and other oncogenes or tumor suppressor genes. CastRT-PCR was used to specifically detect and enumerate CTCs in blood samples with lung cancer cell lines spiking-in and lung cancer patient blood without prior biochemical enrichment processes. EGFR mutation (p.L858R) was detected in all 5 blood samples from late stage lung cancers. Approximately 50% of circulating lung tumor cells with positive EGFR p.L858R mutation had positive EGFR p.T790M mutation. In normal blood samples spiked in cell lines of known Kras and EGFR mutation at the level of 10 cells/mL of whole blood (close to actual patient samples), CastRT-PCR accurately detected the known mutations. Our data suggest that digital castRT-qPCR can be used to enumerate CTCs and detect cancer-related mutations in the blood, which paves the way for future individualized cancer treatment by monitoring CTC level and molecular characterization. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3066. doi:10.1158/1538-7445.AM2011-3066