Abstract
BackgroundmRNA levels of members of the Vascular Endothelial Growth Factor family (VEGF-A, -B, -C, -D, Placental Growth Factor/PlGF) have been investigated as tissue-based markers of colon cancer. These studies, which used specimens obtained by surgical resection or colonoscopic biopsy, yielded contradictory results. We studied the effect of the sampling method on the marker accuracy of VEGF family members.MethodsComparative RT-qPCR analysis was performed on healthy colon and colon carcinoma samples obtained by biopsy (n = 38) or resection (n = 39) to measure mRNA expression levels of individual VEGF family members. mRNA levels of genes encoding the eicosanoid enzymes cyclooxygenase 2 (COX2) and 5-lipoxygenase (5-LOX) and of genes encoding the hypoxia markers glucose transporter 1 (GLUT-1) and carbonic anhydrase IX (CAIX) were included as markers for cellular stress and hypoxia.ResultsExpression levels of COX2, 5-LOX, GLUT-1 and CAIX revealed the occurrence in healthy colon resection samples of hypoxic cellular stress and a concurrent increment of basal expression levels of VEGF family members. This increment abolished differential expression of VEGF-B and VEGF-C in matched carcinoma resection samples and created a surgery-induced underexpression of VEGF-D. VEGF-A and PlGF showed strong overexpression in carcinoma samples regardless of the sampling method.ConclusionsSampling-induced hypoxia in resection samples but not in biopsy samples affects the marker-reliability of VEGF family members. Therefore, biopsy samples provide a more accurate report on VEGF family mRNA levels. Furthermore, this limited expression analysis proposes VEGF-A and PlGF as reliable, sampling procedure insensitive mRNA-markers for molecular diagnosis of colon cancer.
Highlights
MRNA levels of members of the Vascular Endothelial Growth Factor family (VEGF-A, -B, -C, -D, Placental Growth Factor/PlGF) have been investigated as tissue-based markers of colon cancer
Surgical resection induces hypoxic cellular stress in healthy colon tissue To examine to what extent the sampling procedure may affect the overall condition of the sampled tissue, we analyzed the mRNA expression of cyclooxygenase 2 (COX2) and 5-LOX in samples of healthy colon tissue
The expression levels of glucose transporter 1 (GLUT-1) and carbonic anhydrase IX (CAIX), two hypoxia markers, were significantly increased in resected samples compared to biopsy samples (Figure 1C-D)
Summary
MRNA levels of members of the Vascular Endothelial Growth Factor family (VEGF-A, -B, -C, -D, Placental Growth Factor/PlGF) have been investigated as tissue-based markers of colon cancer. These studies, which used specimens obtained by surgical resection or colonoscopic biopsy, yielded contradictory results. Colorectal cancer is the second most commonly diagnosed cancer in females and the third in males It is the second leading cause of cancer-related death [1]. During colonoscopy, which is the gold standard for detection of colon carcinoma and adenoma, biopsies of polyp-like extrusions are obtained for pathological examination, and these extrusions are removed whenever possible. Little is known about the impact of the sampling method on the overall condition of the sampled tissue or the expression levels of potential cancer biomarker genes
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