aneuploidAneuploidy and chromosomal instability demonstrate contrasting effects depending on cellular context: while increased aneuploidy can drive spontaneous tumor formation in aged animals, it simultaneously prevents tumorigenesis in chemically or genetically induced tumor models. This reveals that the same genomic instability phenotype can function both as an oncogenic driver and as a tumor suppressor depending on the tumor initiation mechanism. [@weaver_aneuploidy_2007]

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Research establishes that aneuploidy plays paradoxical roles in cancer development, acting both as a tumor promoter and suppressor depending on context. Studies demonstrate that increased aneuploidy drives spontaneous tumor formation in aged animals, supporting the oncogenic potential of chromosomal instability, yet this same instability acts as a more effective inhibitor than initiator of tumorigenesis when tumors are induced by chemical carcinogens or genetic alterations. Mechanistically, aneuploid cells that successfully transform into tumors do so by inactivating Stat1 signaling while activating Myc, a combination that suppresses the immune cell infiltration normally triggered by chromosomal instability and allows aneuploid cells to evade immune surveillance. The dual nature of aneuploidy appears to depend on whether cells can overcome the fitness costs imposed by chromosomal imbalance, with the tumor-suppressive effects dominating in contexts where cells lack the adaptive mechanisms to tolerate ongoing chromosome missegregation.

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