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BioMed Central, BMC Cancer, 1(14), 2014

DOI: 10.1186/1471-2407-14-760

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GLUT-1 expression is largely unrelated to both hypoxia and the Warburg phenotype in squamous cell carcinomas of the vulva

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Abstract Background Strongly increased uptake of glucose is a hallmark of solid malignant tumors. This phenotype can be triggered by hypoxia-induced gene expression changes or can occur independently of hypoxia as a consequence of malignant transformation itself, and is often referred to as the Warburg effect. The glycolytic phenotype has been associated with malignant progression and resistance to radio- and chemotherapy. Methods We have chosen squamous cell carcinomas of the vulva (SCC-V) as a representative solid tumor entity to study the central players of this pathway, namely glucose transporter (GLUT)-1, carbonic anhydrase (CA) IX, hexokinase (HK)-2 and pyruvate kinase (PK)-M2, and have investigated their relationships to tumor microvessels (CD34, αSMA) and proliferation (Ki67). Expression of these proteins was analyzed in 38 SCC-Vs, 5 vulvar dysplasias and 10 non-neoplastic squamous epithelia of the vulva using multiparametric immunohistochemistry in registered serial sections (MIRSS). Results Expression of GLUT-1 in invasive carcinomas was predominantly located in the outer layers of the tumor cell aggregates close to the vascularized tumor stroma, and only to a lesser extent colocalized with CA IX, which was repeatedly found at larger diffusion distances away from microvessels. CA IX expression was lower in invasive carcinomas compared to dysplasias and non-neoplastic tissue and higher in recurrent vs. primary tumors. Ki67-positive proliferating cells were partially colocalized with GLUT-1. However, HK-2 and PK-2 - proteins centrally involved in the Warburg phenotype - did not show such a correlation. Conclusions Consistent with prior studies, the pattern of GLUT-1 clearly indicated that a large part of its expression is presumably unrelated to hypoxia. However, there was also no association with HK-2 and PK-M2, suggesting that the functional background of this expression is also independent of aerobic glycolysis. CA IX may be worth consideration as a marker of biological hypoxia, as should its pathophysiological consequences in SCC-V.