Loss or inactivation of both copies of which type of gene can lead to cancer?

Tumor-suppressor genes play a critical role in regulating cell division and maintaining genomic stability. These genes produce proteins that prevent uncontrolled cell growth by inhibiting the cell cycle or promoting apoptosis (programmed cell death). When both copies of a tumor-suppressor gene are lost or inactivated, the regulatory mechanisms that normally keep cell division in check are compromised. This loss of function can lead to unregulated cell proliferation, increasing the likelihood of cancer development.

For instance, mutations in the TP53 gene, a well-known tumor-suppressor gene, can lead to various types of cancer, as the protein it encodes is essential for controlling the cell cycle and responding to DNA damage. In contrast, proto-oncogenes, when mutated or overexpressed, can contribute to cancer development, but it is the loss of tumor-suppressor genes that is specifically linked to the necessity of both copies being affected to promote tumorigenesis. Other options like growth factor genes are involved in cellular signaling and may influence cancer indirectly, but the direct link to cancer development is much more pronounced with tumor-suppressor genes when both alleles are inactive.