tumorigenézisel

Tumorigenesis is the process by which normal cells are transformed into cancerous cells. This complex multistep process involves the accumulation of genetic and epigenetic alterations within a cell, leading to uncontrolled proliferation, evasion of cell death, and the ability to invade surrounding tissues and metastasize to distant sites.

The initiation of tumorigenesis often begins with mutations in genes that regulate cell growth and division, known as proto-oncogenes and tumor suppressor genes. Activation of proto-oncogenes, which normally promote cell growth, can lead to their overexpression, driving excessive cell division. Conversely, inactivation of tumor suppressor genes, which normally inhibit cell growth or promote DNA repair, removes critical brakes on proliferation.

Beyond initial genetic mutations, epigenetic changes also play a significant role. These are heritable alterations in gene expression that do not involve changes to the underlying DNA sequence. Examples include DNA methylation and histone modifications, which can silence tumor suppressor genes or activate oncogenes.

The tumor microenvironment also contributes to tumorigenesis. This includes surrounding cells like fibroblasts, immune cells, and blood vessels, as well as extracellular matrix components. These elements can provide growth factors, suppress immune surveillance, and facilitate invasion and metastasis.

Over time, as more genetic and epigenetic damage accumulates, cells can acquire the hallmarks of cancer, enabling them to form a tumor. This progression is a gradual process, and many cells with early genetic alterations do not necessarily develop into a full-blown cancer.