Reduction of Rapid Proliferating Tumour Cell Lines by Inhibition of the Specific Glycine Transporter GLYT1.

Christine Garcia Bierhals,Barry H Hirst,Alison Howard

doi:10.3390/biomedicines9121770

Abstract

Studies have highlighted the relevance of extracellular glycine and serine in supporting high growth rates of rapidly proliferating tumours. The present study analysed the role of the specific glycine transporter GLYT1 in supplying glycine to cancer cells and maintaining cell proliferation. GLYT1 knockdown in the rapidly proliferating tumour cell lines A549 and HT29 reduced the number of viable cells by approximately 30% and the replication rate presented a decrease of about 50% when compared to cells transfected with control siRNA. In contrast, when compared to control, GLYT1 siRNA had only a minimal effect on cell number of the slowly proliferating tumour cell line A498, reducing the number of viable cells by 7% and no significant difference was observed when analysing the replication rate between GLYT1 knockdown and control group. When utilising a specific GLYT1 inhibitor, ALX-5407, the doubling time of rapidly proliferating cells increased by about 8 h presenting a significant reduction in the number of viable cells after 96 h treatment when compared to untreated cells. Therefore, these results suggest that GLYT1 is required to maintain high proliferation rates in rapidly proliferating cancer cells and encourage further investigation of GLYT1 as a possible target in a novel therapeutic approach.

Highlights

Tumour cells present a different metabolism than normal cells utilising aerobic glycolysis to obtain energy even when oxygen levels are adequate, a metabolic mechanism known as the Warburg effect [1,2,3]
GLYT1 mRNA expression was reduced by 86%, 79%, 93% when A549, HT29 and A498 cells, respectively, were treated with a specific GLYT1 small interfering RNAs (siRNAs), in comparison to control groups treated with Negative siRNA (Figure 1a)
GLYT1kd cells demonstrated a significant reduction in glycine uptake from the extracellular medium when compared to Controls; glycine uptake was reduced by 35%, 31%, and 41% in A549, HT29 and A498 tumour cells, respectively (Figure 1b)

Summary

Introduction

Tumour cells present a different metabolism than normal cells utilising aerobic glycolysis to obtain energy even when oxygen levels are adequate, a metabolic mechanism known as the Warburg effect [1,2,3] They present an altered requirement for certain amino acids, different from normal cells [4]. Clinical studies have linked high glycine concentration in tumour tissues with poor patient prognosis in colorectal and breast cancers [8,9,10]. Taken together, this evidence suggests an important role for extracellular glycine in supporting rapid proliferation rate of some tumours

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Conclusion