CAPG (Capping Actin Protein, Gelsolin-Like) is a protein found in human cells, managing their internal structure. Encoded by the CAPG gene, it belongs to a family of proteins interacting with actin, a fundamental component of cellular scaffolding. Its purpose is to maintain the organization and dynamics of the cellular framework, present in various tissues.
The Cellular Role of CAPG
Cells maintain their shape, move, and divide through an intricate internal framework known as the actin cytoskeleton. This dynamic network consists of actin filaments that constantly assemble and disassemble. CAPG plays a specific role in controlling the growth of these actin filaments by “capping” their ends, preventing further addition of actin units.
This capping action is reversible, influenced by calcium ions and specific lipids called phosphoinositides. By regulating the length and stability of actin filaments, CAPG directly impacts cellular processes that rely on actin rearrangement. These processes include cell migration, adhesion, and proper division. CAPG is widespread across various tissues, with higher expression in areas like the prostate, lung, and kidney.
Connection to Cancer Progression
In various forms of cancer, CAPG protein regulation is disrupted, often leading to increased levels or altered activity. Research indicates that CAPG is overexpressed in numerous solid tumors when compared to healthy tissues, including breast invasive carcinoma, ovarian serous cystadenocarcinoma, and glioblastoma multiforme. This elevated expression of CAPG is associated with more aggressive tumor behavior and progression.
When CAPG levels are high, cells can become excessively mobile and invasive. This heightened cell movement is a significant factor in metastasis, where cancer cells spread from the original tumor to other parts of the body. For example, increased CAPG expression in breast cancer is linked to a more invasive cellular phenotype, and its knockdown can reduce invasiveness. In ovarian carcinoma, CAPG overexpression correlates with increased cell migration and invasiveness. In human glioma, higher CAPG levels promote cell growth, migration, and invasiveness.
Diagnostic and Therapeutic Potential
The link between CAPG levels and cancer aggressiveness suggests its utility in clinical settings. CAPG could serve as a biomarker, an indicator that helps predict a patient’s prognosis or the likelihood of cancer spreading. For instance, elevated CAPG expression is associated with a less favorable prognosis in various cancers, including shorter overall survival, increased likelihood of lymph node metastasis, and advanced tumor stages. Measuring CAPG levels might offer insights into tumor aggressiveness, potentially guiding treatment decisions.
Beyond diagnosis, CAPG is also being explored as a potential target for new cancer therapies. Researchers are investigating strategies to block or reduce CAPG activity in cancer cells to slow or prevent metastasis. Early studies indicate that targeting CAPG, for example with a nanobody, can help restrict breast cancer metastasis. Disrupting CAPG’s function could interfere with cellular mechanisms that enable cancer cells to move and invade, potentially limiting disease spread.