Supplementary Material for: Two populations of double minute chromosomes harbor distinct amplicons, the <i>MYC</i> locus at 8q24.2 and a 0.43-Mb region at 14q24.1, in the SW613-S human carcinoma cell line

High-level amplifications observed in tumor cells are usually indicative of genes involved in oncogenesis. We report here a high resolution characterization of a new amplified region in the SW613-S carcinoma cell line. This cell line contains tumorigenic cells displaying high-level <i>MYC</i> amplification in the form of double minutes (DM<sup>+</sup> cells) and non tumorigenic cells exhibiting low-level <i>MYC</i> amplification in the form of homogeneously staining regions (DM<sup>–</sup> cells). Both cell types were studied at genomic and functional levels. The DM<sup>+</sup> cells display a second amplification, corresponding to the 14q24.1 region, in a distinct population of DMs. The 0.43-Mb amplified and overexpressed region contains the <i>PLEK2, PIGH, ARG2, VTI1B, RDH11</i><i>,</i> and <i>ZFYVE26</i> genes. Both amplicons were stably maintained upon in vitro and in vivo propagation. However, the 14q24.1 amplicon was not found in cells with high-level <i>MYC</i> amplification in the form of HSRs, either obtained after spontaneous integration of endogenous DM <i>MYC</i> copies or after transfection of DM<sup>–</sup> cells with a <i>MYC</i> gene expression vector. These HSR-bearing cells are highly tumorigenic. The 14q24.1 amplification may not play a role in malignancy per se but might contribute to maintaining the amplification in the form of DMs.

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