Expulsion of micronuclei containing amplified genes contributes to a decrease in double minute chromosomes from malignant tumor cells

Abstract

Double minute chromosomes (DMs) are a hallmark of gene amplification. The relationship between the formation of DMs and the amplification of DM-carried genes remains to be clarified. The human colorectal cancer cell line NCI-H716 and human malignant primitive neuroectodermal tumor cell line SK-PN-DW are known to contain many DMs. To examine the amplification of DM-carried genes in tumor cells, we performed Affymetrix SNP Array 6.0 analyses and verified the regions of amplification in NCI-H716 and SK-PN-DW tumor cells. We identified the amplification regions and the DM-carried genes that were amplified and overexpressed in tumor cells. Using RNA interference, we downregulated seven DM-carried genes, (NDUFB9, MTSS1, NSMCE2, TRIB1, FAM84B, MYC and FGFR2) individually and then investigated the formation of DMs, the amplification of the DM-carried genes, DNA damage and the physiological function of these genes. We found that suppressing the expression of DM-carried genes led to a decrease in the number of DMs and reduced the amplification of the DM-carried genes through the micronuclei expulsion of DMs from the tumor cells. We further detected an increase in the number of γH2AX foci in the knockdown cells, which provides a strong link between DNA damage and the loss of DMs. In addition, the loss of DMs and the reduced amplification and expression of the DM-carried genes resulted in a decrease in cell proliferation and invasion ability.

Aurora B–mediated localized delays in nuclear envelope formation facilitate inclusion of late-segregating chromosome fragments

“…Historically, micronuclei have been used as biomarkers for genomic instability, and their increased presence of micronuclei in human cells is typically associated with cancer ( Bonassi et al ., 2011 ; Santos et al ., 2010 ; Celik et al ., 2013 ). As such, there has been much interest in understanding the cellular response to micronucleus formation and subsequent micronucleus fate ( Fenech et al ., 2011 ; Huang et al ., 2011 ; Kirsch-Volders et al ., 2011 ; Hatch et al ., 2013 ; Ji et al ., 2013 ). Previous studies showed a direct correlation between Aurora B levels and micronucleus frequency ( Tatsuka et al ., 1998 ).…”

Cytotoxic and genotoxic effects of 131I and 60Co in follicular thyroid cancer cell (WRO) with and without recombinant human thyroid‐stimulating hormone treatment

“…Numerical and structural anomalies were observed by van Staveren et al [] with 68–77 chromosomes. The presence of double minutes in WRO cells is indicative of oncogene amplifications that are also found in other solid tumors, such as colon, pancreatic, breast carcinomas, and also leukemia, but not in normal cells [Shimizu et al, ; Shimizu, ; Movafagh et al, ; Ji et al, ; Storlazzi et al, ].…”

Cell-Free eccDNAs: A New Type of Nucleic Acid Component for Liquid Biopsy?

“…This entire procedure is illustrated in Figure 1. Although this strategy is very effective for small eccDNAs (like microDNA and spcDNA) it remains difficult to extract the entire circular DNA for the large DMs, for which alternative methods like microdissection (13), array-CGH (39) or direct sequencing of the total DNA (40) can be applied, as sequences on DMs are highly amplified. As the quantity of cfDNAs obtained from body fluids is very limited, when using cfDNAs as starting material, eccDNA enrichment method may need further improvement to increase sensitivity.…”