Use of Fluorescence In Situ Hybridization (FISH) in Diagnosis and Tailored Therapies in Solid Tumors

Abstract

Fluorescence in situ hybridization (FISH) is a standard technique used in routine diagnostics of genetic aberrations. Thanks to simple FISH procedure is possible to recognize tumor-specific abnormality. Its applications are limited to designed probe type. Gene rearrangements e.g., ALK, ROS1 reflecting numerous translocational partners, deletions of critical regions e.g., 1p and 19q, gene fusions e.g., COL1A1-PDGFB, genomic imbalances e.g., 6p, 6q, 11q and amplifications e.g., HER2 are targets in personalized oncology. Confirmation of genetic marker is frequently a direct indication to start specific, targeted treatment. In other cases, detected aberration helps pathologists to better distinguish soft tissue sarcomas, or to state a final diagnosis. Our main goal is to show that applying FISH to formalin-fixed paraffin-embedded tissue sample (FFPE) enables assessing genomic status in the population of cells deriving from a primary tumor or metastasis. Although many more sophisticated techniques are available, like Real-Time PCR or new generation sequencing, FISH remains a commonly used method in many genetic laboratories.

Keywords: ALK; COL1A1-PDGFB; FISH; HER2; ROS1; personalized medicine; personalized oncology; t(X,18); targeted treatment.

Figure 1

Applications of fluorescence in situ hybridization (FISH) in genetic diagnostics in solid tumors on FFPE material: A—1p/19q probe: a-1 deletion of 1p32 locus, a-2 normal signal pattern (cell on the left) and deletion of 19q13 locus (cell on the right), a-3 normal signal pattern (Abbott Molecular), B—dual fusion probe: fusions and normal signals pattern of COL1A1 and PDGFB loci (ZytoVision), C—break apart probe: c-1 rearrangement of ALK gene, c-2 normal signal pattern (Abbott Molecular), D—break apart probe: rearrangement of EWSR1 locus (Abbott Molecular), F—break apart probe: f-1 rearrangement of ROS1 gene, f-2 normal signal pattern (Empire Genomics), G—locus specific probe: g-1 amplification of HER2 locus, g-2 normal signal pattern (Abbott Molecular), E—break apart probe: normal signal pattern of SS18 locus (Abbott Molecular). Majority probes indicate region of interest in red color and control region—in green, excluding picture B, where red color indicates COL1A1 gene locus, green color—PDGFB gene locus, yellow color—fusion of COL1A1-PDGFB and PDGFB-COL1A1. Full names of available commercial probes are presented in Table 2.