Hypoxia modulates cellular endocytic pathways and organelles with enhanced cell migration and 3D cell invasion.

Abstract

Hypoxia is characteristic of most tumors and has been shown to drive cancer progression by altering multiple subcellular processes. We hypothesized that cancer cells in hypoxic environment might have slower proliferation rates and increased invasion and migration rates with altered endocytosis compared to the cancer cells in periphery of tumor mass that experiences normoxic conditions.We measured effect of chemically induced hypoxia on cell proliferation, migration, and invasion. Uptake of fluorescently labeled transferrin, galectin3, and dextran that undergo endocytosis through major endocytic pathways (Clathrin-mediated pathway (CME), Clathrin-independent pathway (CIE), Fluid phase endocytosis (FPE)) was analyzed during hypoxia. Also, the organelle changes associated with hypoxia were studied with organelle trackers. We found that the proliferation rate decreased, and the migration and invasion rate increased in cancer cells in hypoxic conditions compared to normoxic cancer cells. A short hypoxic exposure increased endocytosis in hypoxic cancer cells, but a prolonged hypoxic exposure decreased clathrin-independent endocytic uptake. Subcellular organelles, such as mitochondria, increased to withstand the hypoxic stress, while other organelles, such as Endoplasmic reticulum (ER), were significantly decreased. These data suggest that hypoxia modulates cellular endocytic pathways with reduced proliferation and enhanced cell migration and invasion.