invasionmetastasis

Invasion and metastasis are two related processes that drive cancer spread, sometimes referred to as invasionmetastasis.

During invasion, cancer cells detach from the primary mass, degrade extracellular matrix, and migrate through tissue barriers. Metastasis requires several additional steps: intravasation into blood or lymphatic vessels, survival in circulation, arrest and extravasation at distant organ sites, and colonization to establish secondary tumors. Each step presents multiple barriers, making metastatic spread a multistep and inefficient process.

Molecular mechanisms include changes in cell adhesion, loss of epithelial characteristics through epithelial-to-mesenchymal transition, and motility. Proteolytic enzymes such as matrix metalloproteinases facilitate matrix breakdown, while growth factors, cytokines, and angiogenic signals create pathways for dissemination. Tumor cells also adapt to new microenvironments, evading immune surveillance during transit.

Organ-specific patterns of metastasis, or organotropism, reflect interactions between tumor cells and tissues. The 'seed and soil' concept describes how certain cancer cells (seeds) thrive in compatible microenvironments (soil). The pre-metastatic niche and circulation dynamics influence which organs are more likely to harbor metastases.

Clinically, invasion and metastasis determine cancer stage, prognosis, and treatment strategy. Detection relies on imaging, biopsies, and biomarkers. Therapeutic approaches focus on limiting dissemination and growth at distant sites, including surgery and radiotherapy for local disease, systemic therapies targeting molecular drivers, anti-angiogenic or immune-based treatments, and strategies to counteract EMT or invasion-related pathways.

Research continues to characterize the biology of invasion and metastasis, develop models that mimic metastatic spread, and identify biomarkers that predict metastatic risk. Challenges include the heterogeneity of tumors, early micrometastases, and the need for therapies that can eradicate disseminated cells without excessive toxicity.