Abstract
MYC family members, MYC, MYCN, and MYCL, are oncogenic transcription factors that regulate the expression of genes involved in normal development, cell growth, proliferation, metabolism, and survival. While MYC is amplified and/or overexpressed across a variety of tissue types, MYCN is often overexpressed in tumors of the nervous system (neuroblastoma and medulloblastoma) or with neuroendocrine features (neuroendocrine prostate cancer). Given recent reports that MYCN expression is also deregulated in a variety of non-neuronal tissue types, we investigated whether MYCN was also deregulated in triple-negative breast cancer (TNBC). In contrast to previous individual immuno-fluorescence (IF) stains against higher expressing MYC family isoform protein, we developed an IF stain to simultaneously detect both MYCN- and MYC-expressing cells within the same tumor cell population. Our methodology allows for the detection of low level MYCN and MYC expression and can be multiplexed with additional protein probes. Herein, using tyramide signal amplification (TSA), we present two protocols for the IF detection of MYCN and MYC on formalin-fixed paraffin embedded (FFPE) tumor sections and in cell lines fixed in situ after growth as adherent cultures on chambered microscope slides.