Figure 1.

Tumor microenvironmental stresses induce autophagy and affect cancer cell growth and metastasis. Autophagy is activated in response to multiple stresses during cancer progression, including hypoxia, nutrient deprivation, extracellular matrix detachment, endoplasmic reticulum stress and other stresses. Under these stressful conditions, autophagy constitutes a major protective mechanism that allows cells to survive in the primary tumor and migrate into adjacent connective tissue, leading to metastasis in carcinomas. However, if microenvironmental stresses persist, excessive autophagy may ultimately lead to autophagic cell death.