The immune system plays a major role in the protection against cancer. Identifying and characterizing the pathways mediating this immune surveillance are thus critical for understanding how cancer cells are recognized and eliminated. Aneuploidy is a hallmark of cancer, and we previously found that untransformed cells that had undergone senescence due to highly abnormal karyotypes are eliminated by natural killer (NK) cells in vitro. However, the mechanisms underlying this process remained elusive. Here, using an in vitro NK cell killing system, we show that non‐cell‐autonomous mechanisms in aneuploid cells predominantly mediate their clearance by NK cells. Our data indicate that in untransformed aneuploid cells, NF‐κB signaling upregulation is central to elicit this immune response. Inactivating NF‐κB abolishes NK cell‐mediated clearance of untransformed aneuploid cells. In cancer cell lines, NF‐κB upregulation also correlates with the degree of aneuploidy. However, such upregulation in cancer cells is not sufficient to trigger NK cell‐mediated clearance, suggesting that additional mechanisms might be at play during cancer evolution to counteract NF‐κB‐mediated immunogenicity.

SummaryThe immune system plays a major role in the protection against cancer. Identifying and characterizing the pathways mediating this immune surveillance is thus critical for understanding how cancer cells are recognized and eliminated. We previously found that untransformed cells that had undergone senescence due to highly abnormal karyotypes are eliminated by Natural Killer (NK) cells in vitro. Here we show that this is also true for aneuploid untransformed cells that had not lost their ability to proliferate. Their elimination by NK cells, like that of aneuploid senescent cells, is predominantly mediated by non-cell autonomous mechanisms. Our data further indicate that NF-κB signaling in aneuploid cells is central to eliciting this immune response. Inactivating NF-κB abolishes NK-cell mediated clearance in aneuploid cells in vitro. In cancer cell lines, NF-κB signaling correlates with degree of aneuploidy, raising the possibility that aneuploidy-induced immune recognition is partially retained in cancer.

Chromosome mis-segregation leads to aneuploidy, a condition in which cells harbor an imbalanced chromosome number. Several lines of evidence strongly indicate that aneuploidy triggers genome instability, ultimately generating cells with complex karyotypes that arrest their proliferation. Isolation and characterization of cells harboring complex karyotypes are crucial to study the impact of an imbalanced chromosome number on cell physiology. To date, no methods have been established to reliably isolate such aneuploid cells. This paper provides a protocol for the enrichment and analysis of aneuploid cells with complex karyotypes utilizing standard, inexpensive tissue culture techniques. This protocol can be used to analyze several features of aneuploid cells with complex karyotypes including their induced senescence-associated secretory phenotype, pro-inflammatory properties, and ability to interact with immune cells. Because cancer cells often harbor imbalances in chromosome number, it is crucial to decipher how aneuploidy impacts cell physiology in normal cells, with the ultimate goal of uncovering both its pro- and anti-tumorigenic effects.

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