Background

Cancer cell genomes exhibit inherent instability. During cell division, incomplete replication or failure of chromosome segregation occurs, frequently leading to the loss of entire chromosomes or portions of chromosome arms. In the scientific community, a state in which the number of chromosomes within a cell deviates from the normal range is defined as aneuploidy. In the field of tumor genetics, aneuploidy has been identified as a representative characteristic explaining the malignant transformation of various solid tumors, including breast cancer.

However, the specific driving forces behind the occurrence of aneuploidy and its impact on tumor formation remain largely unknown. Previous genomic analysis methods have made it difficult to trace the precise effects of chromosome number changes on gene function. Most studies have assumed that the numerous copy number alterations (CNAs) associated with chromosome number changes act in concert to promote the evolution of tumor cells.

The fundamental question of why cancer cells undergo such extensive genomic disruption to survive and grow remains unanswered. In particular, it has long been unclear whether there are specific key genes that drive actual tumor formation during the accumulation of aneuploidy, and whether these genes can independently induce malignant transformation.

Key Findings

A recent study published in the international journal Nature reveals that even within seemingly disordered aneuploid variations, there exist distinct key oncogenes that actually dominate tumor formation. The experiment was designed based on a mouse model of breast cancer, tracking genomic instability. The analysis revealed that during the process of highly unstable cells evolving into tumors, only 1-2 key genes are specifically activated.

When these key genes are sufficiently activated, cancer cells form tumors without accumulating additional aneuploidy. In other words, an alternative pathway has been discovered that allows cancer cells to bypass the need for the complex accumulation of chromosomal structural changes required to acquire a malignant phenotype. This suggests that aneuploidy is not a direct cause of cancer, but rather a type of genomic screening mechanism for selecting a small number of oncogenes with optimal survival functions.

It is also noteworthy that the function of these genes is manifested only when an 'intact microenvironment' around the tumor exists. When the researchers conducted experiments by disrupting or artificially modifying the structure of the tumor microenvironment (TME), these key genes were unable to independently induce the proliferation of cancer cells. The interaction with the surrounding environment of the tumor is necessary for cancer progression.

Significance and Prospects

This research may serve as a turning point that completely changes the perspective on aneuploidy in cancer biology. By moving away from the conventional view of genomic instability as an uncontrollable chaotic state, it redefines it as a highly precise evolutionary process in which cancer cells select specific target genes to form tumors. This paradigm shift is expected to pave the way for a new design for the development of anticancer drugs.

The most immediate change expected is the improvement in the efficiency of selecting new drug targets. Instead of trying to block hundreds of complex chromosomal variations, it becomes possible to develop a therapeutic strategy that focuses on targeting only 1-2 key genes hidden behind genomic variations. This can clarify the mechanism of action of the drug and significantly reduce side effects.

However, this study was conducted based on a mouse model, so further research is needed to confirm whether the same phenomenon is reproduced in the actual breast cancer development process in human patients. The actual tumor microenvironment in humans is much more complex than in mouse models, and the diversity of the immune system is also greater. In the future, it will be a major research task to elucidate the specific signaling pathways that these genes activate in the interaction with the surrounding tissues.