Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C062

Oral Communications

Surviving metabolism: acidity as a selection pressure in colorectal cancer cell lines

J. Michl1,2, S. Monterisi1,2, W. F. Bodmer2, P. Swietach1

1. Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, United Kingdom. 2. Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.

Introduction: Extracellular acidity is a chemical signature of tumours. It arises because the raised metabolic rate in cancer cells releases large quantities of lactic acid and CO2 into the tumour microenvironment (1, 2). Dysregulated pH has been shown to perturb or even kill cancer cells. Although targeting acidity is a good candidate for the therapeutic management of tumour growth (3), so far, none of the major approved therapies are based explicitly on disrupting acid handling and/or signalling. Using a large panel of colorectal cancer (CRC) cell lines, our aim was to identify the molecular processes that provide a survival benefit to cancer cells living under acid-stress. Methods: We investigated pH-related physiology in over 40 CRC cell lines. We measured (i) survival by sulphorhodamine B (SRB) assay, (ii) lumen formation by F-actin staining, (iii) extracellular pH (pHe) time courses as a readout of metabolic rate, and (iv) intracellular pH (pHi) on a single-cell level by fluorescence imaging. These measurements we performed over a range of pHe values using an imaging plate reader (Cytation 5, Biotek). Results: CRC cell lines displayed a wide range of sensitivities to changes in pHe. A 50% reduction in survival was associated with pHe values of 7.3 (most sensitive: Iscerol) to below 6.5 (least sensitive: C106). pHe-sensitivity was also observed in 3D cultures grown in Matrigel. CRC cell lines categorised as pH-sensitive formed smaller colonies under acidic pHe (6.76); however, their differentiation status was independent of pHe. Furthermore, the cell lines differed in their ability to regulate pHi in response to changes in ambient pHe, quantified in terms of the slope of their pHi-pHe relationship. This metric of pHi-control ranged from 0.16 (Colo206) to 0.59 (Iscerol), representing strong to weak pHi control, respectively. Conclusions: We established a database that provides a comprehensive appraisal of the pH phenotype for individual CRC cell lines. This information allows us to correlate phenotype with mutations and gene expression profiles of these cell lines, and to identify molecular processes involved in acid handling and signalling.

Where applicable, experiments conform with Society ethical requirements