Mapping pH at Cancer Cell Surfaces
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To develop a tool to measure the pH at the surfaces of individual cells.
The SNARF pH-sensitive dye was conjugated to a pHLIP® peptide (pH-Low Insertion Peptide) that binds cellular membranes in tumor spheroids. A beam splitter allows simultaneous recording of two images (580 and 640 nm) by a CCD camera. The ratio of the two images is converted into a pH map resolving single spheroid cells. An average pH for each cell is calculated and a pH histogram is derived.
Surface pH depends on cellular glycolytic activity, which was varied by adding glucose or deoxy-glucose. Glucose was found to decrease the surface pH relative to the pH of the bulk solution. The surface pH of metastatic cancer cells was lower than that of non-metastatic cells indicating a higher glycolytic activity.
Our method allows cell surface pH measurement and its correlation with cellular glycolytic activity.
Key WordspHLIP Warburg effect Tumor acidity pH measurements SNARF fluorescence
We would like to thank our colleagues Anna Moshnikova and Michael Anderson for useful discussions and suggestions.
Financial support was received from NIH RO1 GM073857 grant to DME, OAA, and YKR.
Compliance with Ethical Standards
Conflict of Interest
D.M.E., O.A.A., and Y.K.R. are founders of pHLIP, Inc. They have shares in the company, but the company did not fund any part of the work reported in the paper, which was done in their academic laboratories.
- 16.Hashim AI, Zhang X, Wojtkowiak JW, Martinez GV, Gillies RJ (2011) Imaging pH and metastasis. NMR Biomed 24:582–591Google Scholar
- 17.Moon RB, Richards JH (1973) Determination of intracellular pH by 31P magnetic resonance. J Biol Chem 248:7276–7278Google Scholar
- 20.Garcia-Martin ML, Herigault G, Remy C et al (2001) Mapping extracellular pH in rat brain gliomas in vivo by 1H magnetic resonance spectroscopic imaging: comparison with maps of metabolites. Cancer Res 61:6524–6531Google Scholar
- 22.Wykoff CC, Beasley NJ, Watson PH et al (2000) Hypoxia-inducible expression of tumor-associated carbonic anhydrases. Cancer Res 60:7075–7083Google Scholar
- 23.Griffiths JR, McIntyre DJ, Howe FA, Stubbs M (2001) Why are cancers acidic? A carrier-mediated diffusion model for H+ transport in the interstitial fluid. Novartis Found Symp 240:46–62 discussion 62–47, 152–153Google Scholar
- 24.Ivanov S, Liao SY, Ivanova A, Danilkovitch-Miagkova A, Tarasova N, Weirich G, Merrill MJ, Proescholdt MA, Oldfield EH, Lee J, Zavada J, Waheed A, Sly W, Lerman MI, Stanbridge EJ (2001) Expression of hypoxia-inducible cell-surface transmembrane carbonic anhydrases in human cancer. Am J Pathol 158:905–919CrossRefGoogle Scholar