Estelle Annick Cuttaz, Laurène Nathalie Dupont, Martinus Gijs, Huu Tuan Nguyen, Raphaël Etienne Jean Trouillon
Fluorescence in situ hybridization (FISH) is a powerful technique for evaluating the HER2 gene status in breast cancer specimen (1). However, most of FISH assays currently used in clinical laboratories are expensive and require long experimental time, up to two days with an overnight incubation (2). Indeed, despite the development of faster FISH probes (HER2 IQFISH pharmDxTM from DAKO, Denmark) cutting the assay time to one day (3), the cost of these new probes is still high (more than 200$/test) and impedes the dissemination of this technique. In this study, we present the extra short incubation microfluidic assisted- fluorescence in situ hybridization (ESIMA-FISH) technique that uses microfluidics to improve FISH for HER2 assessment in breast cancer samples. ESIMA-FISH requires a very short incubation time (35 minutes) and uses 4-fold less probe solution per test. The system is based on a microfluidic chip, developed in our laboratory (4), that is clamped against a microscope slide containing a breast cancer tissue specimen (figure 1). A fluorescent DNA probe solution, specific to the target DNA, is then applied to the tissue section within a thin chamber using the microfluidic system. The probe solution used is obtained by diluting 4 times the standard HER2 IQFISH pharmDxTM probe solution (DAKO, Denmark). Oscillating flows can then be implemented using syringe pumps to improve the delivery of the probe to the tissue. Thanks to this hydrodynamic enhancement of mass transport, the probe-target hybridization efficiency is increased, resulting in overall reductions in the cost and duration of the assay. To validate the ESIMA-FISH technique, several tissue specimens were blindly tested with ESIMA-FISH and standard IQFISH. The results from these two techniques were comparable (figure 2, 3), supporting the possibility of a future clinical use of ESIMA-FISH.