Giant Magnetoresistive Nanosensor Analysis of Circulating Tumor DNA Epidermal Growth Factor Receptor Mutations for Diagnosis and Therapy Response Monitoring.

BACKGROUND: Liquid biopsy circulating tumor DNA (ctDNA) mutational analysis holds great promises for precision medicine targeted therapy and more effective cancer management. However, its wide adoption is hampered by high cost and long turnaround time of sequencing assays, or by inadequate analytical sensitivity of existing portable nucleic acid tests to mutant allelic fraction in ctDNA. METHODS: We developed a ctDNA Epidermal Growth Factor Receptor (EGFR) mutational assay using giant magnetoresistive (GMR) nanosensors. This assay was validated in 36 plasma samples of non-small cell lung cancer patients with known EGFR mutations. We assessed therapy response through follow-up blood draws, determined concordance between the GMR assay and radiographic response, and ascertained progression-free survival of patients. RESULTS: The GMR assay achieved analytical sensitivities of 0.01% mutant allelic fraction. In clinical samples, the assay had 87.5% sensitivity (95% CI = 64.0-97.8%) for Exon19 deletion and 90% sensitivity (95% CI = 69.9-98.2%) for L858R mutation with 100% specificity; our assay detected T790M resistance with 96.3% specificity (95% CI = 81.7-99.8%) with 100% sensitivity. After 2 weeks of therapy, 10 patients showed disappearance of ctDNA by GMR (predicted responders), whereas 3 patients did not (predicted nonresponders). These predictions were 100% concordant with radiographic response. Kaplan-Meier analysis showed responders had significantly (P < 0.0001) longer PFS compared to nonresponders (N/A vs. 12 weeks, respectively). CONCLUSIONS: The GMR assay has high diagnostic sensitivity and specificity and is well suited for detecting EGFR mutations at diagnosis and noninvasively monitoring treatment response at the point-of-care.

Flexible binding of PNP pincer ligands to monomeric iron complexes.

Transition metal complexes supported by pincer ligands have many important applications. Here, the syntheses of five-coordinate PNP pincer-supported Fe complexes of the type (PNP)FeCl2 (PNP = HN{CH2CH2(PR2)}2, R = iPr ((iPr)PNP), tBu ((tBu)PNP), or cyclohexyl ((Cy)PNP)) are reported. In the solid state, ((iPr)PNP)FeCl2 was characterized in two different geometries by X-ray crystallography. In one form, the (iPr)PNP ligand binds to the Fe center in the typical meridional geometry for a pincer ligand, whereas in the other form, the (iPr)PNP ligand binds in a facial geometry. The electronic structures and geometries of all of the (PNP)FeCl2 complexes were further explored using (57)Fe Mössbauer and magnetic circular dichroism spectroscopy. These measurements show that in some cases two isomers of the (PNP)FeCl2 complexes are present in solution and conclusively demonstrate that binding of the PNP ligand is flexible, which may have implications for the reactivity of this important class of compounds.

Multigene profiling of single circulating tumor cells.

Numerous techniques for isolating circulating tumor cells (CTCs) have been developed. Concurrently, single-cell techniques that can reveal molecular components of CTCs have become widely available. We discuss how the combination of isolation and multigene profiling of single CTCs in our platform can facilitate eventual translation to the clinic.