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Updated: Jan 29, 2026

Fluorescence Microscopy for ATP Internalization Mediated by Macropinocytosis in Human Tumor Cells and Tumor-xenografted Mice
Published on: June 30, 2021
Quantitation of Macropinocytosis in Cancer Cells
Koen M O Galenkamp1, Basheer Alas1, Cosimo Commisso2
1Tumor Initiation and Maintenance Program, NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
Abstract:
Macropinocytosis has emerged as an important nutrient supply pathway that sustains cell growth of cancer cells within the nutrient-poor tumor microenvironment. By internalizing extracellular fluid through this bulk endocytic pathway, albumin is supplied to the cancer cells, which, after degradation, serves as an amino acid source to meet the high nutrient demands of these highly proliferating cells. Here, we describe a streamlined protocol for visualization and quantitation of macropinosomes in adherent cancer cells grown in vitro. The determination of the "macropinocytic index" provides a tool for measuring the extent to which this internalization pathway is utilized within the cancer cells and allows for comparison between different cell lines and treatments. The protocol provided herein has been optimized for reproducibility and is readily adaptable to multiple conditions and settings.
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