Proliferation

Proliferation (from Latin proles, meaning “offspring”, and fero, meaning “to bear”) is a fundamental biological process of cell reproduction through growth and subsequent division (mitosis), which leads to an increase in the number of cell elements and, as a result, to tissue growth.

This process underpins the development, growth, and life support of any multicellular organism. Proliferation ensures both normal physiological functions and the development of many pathological conditions, including tumor growth.

Physiological and Pathological Proliferation

Cell proliferation may occur as a normal, regulated process or as an excessive, pathological one.

Types of proliferation:

• Physiological proliferation:
  • Description: A normal, strictly regulated process necessary for life.
  • Examples: Embryonic development, child’s body growth, tissue regeneration after damage (wound healing), renewal of the permanently dying cells (skin and intestinal epithelium, blood cells), as well as the reproduction of lymphocytes in response to infection (immune response).
• Pathological proliferation:
  • Description: Excessive, uncontrolled, or poorly controlled cell reproduction, which underlies many diseases.
  • Examples: Benign neoplasms (polyps, adenomas, fibroids), where proliferation is excessive but remains partially controlled. Malignant tumors (cancer), characterized by completely uncontrolled proliferation with invasion into surrounding tissues. Psoriasis, which involves excessive proliferation of epidermal cells.

Molecular Mechanisms and Regulation

Proliferation is based on the cell cycle — a sequence of events that ends with cell division. This cycle is strictly controlled by a complex system of regulatory proteins.

Tumor suppressor genes (e.g., p53, Rb) play a key role in regulation by acting as “brakes” that halt the cell cycle when necessary, whereas proto-oncogenes encode proteins that stimulate cell division (growth factors and their receptors). Normally, a balance is maintained between these systems. Disruption of this balance as a result of mutations leads to uncontrolled proliferation and is the main cause of cancer.

Clinical Significance

The concept of proliferation is central to oncology, pathomorphology, and regenerative medicine. In the histological diagnosis of tumors, determining the proliferation index (e.g., using the Ki-67 marker) is a key prognostic factor: the higher the index, the more aggressive the tumor and the worse the prognosis. Most chemotherapeutic drugs act as antiproliferative agents; their mechanism targets the suppression of cell division or the destruction of rapidly dividing cancer cells. At the same time, stimulating controlled proliferation is one of the main goals of regenerative medicine, which aims to restore damaged tissues.