Specific genes involved in synthesis and editing of heparan sulfate proteoglycans show altered expression patterns in breast cancer

Abstract

BackgroundThe expression of a specific set of genes controls the different structures of heparan sulfate proteoglycans (HSPGs), which are involved in the growth, invasion and metastatic properties of cancerous cells. The purpose of this study is to increase knowledge of HSPG alterations in breast cancer.MethodsTwenty-three infiltrating ductal adenocarcinomas (IDCs), both metastatic and non-metastatic were studied. A transcriptomic approach to the structure of heparan sulfate (HS) chains was used, employing qPCR to analyze both the expression of the enzymes involved in their biosynthesis and editing, as well as the proteoglycan core proteins. Since some of these proteoglycans can also carry chondroitin sulfate chains, we extended the study to include the genes involved in the biosynthesis of these glycosaminoglycans. Histochemical techniques were also used to analyze tissular expression of particular genes showing significant expression differences, of potential interest.ResultsNo significant change in transcription was detected in approximately 70% of analyzed genes. However, 13 demonstrated changes in both tumor types (40% showing more intense deregulation in the metastatic), while 5 genes showed changes only in non-metastatic tumors. Changes were related to 3 core proteins: overexpression of syndecan-1 and underexpression of glypican-3 and perlecan. HS synthesis was affected by lower levels of some 3-O-sulfotransferase transcripts, the expression of NDST4 and, only in non metastatic tumors, higher levels of extracellular sulfatases. Furthermore, the expression of chondroitin sulfate also was considerably affected, involving both the synthesis of the saccharidic chains and sulfations at all locations. However, the pro-metastatic enzyme heparanase did not exhibit significant changes in mRNA expression, although in metastatic tumors it appeared related to increased levels of the most stable form of mRNA. Finally, the expression of heparanase 2, which displays anti-metastatic features, experienced a strong deregulation in all patients analyzed.ConclusionsIDCs show alterations in the expression of HSPG genes; principally the expression and localization of proteoglycans and the sulfation patterns of glycosaminoglycan chains, depending on the metastatic nature of the tumor. In addition, the anti-proliferative molecule heparanase 2 experiences strong deregulation, thus highlighting it as a potentially interesting diagnostic factor.

Tissue-specificity of heparan sulfate biosynthetic machinery in cancer

“…According Affimetrix microarray analysis, only 9 of 100 GAG biosynthesis-involved genes (EXT2, CHSY3, CSGALNACT1, HS3ST2, HS2ST1, CHST11, CSGALNACT2, HPSE, SULF2) are significantly different between normal and malignant human plasma cells, while the rest genes remain unchanged; 30 6 of 15 GAG biosynthesis-involved genes are changed in neuroendocrine tumors; 31 7 of 21 key HS-synthesising genes are significantly deregulated in breast cancer. 32 Although the obtained results were not analyzed in terms of overall configuration of GAG-biosynthetic machinery in tumors, they support a common disbalance of the system in cancer. Complex analysis of transcriptional activity of HS biosynthetic system in normal prostate tissue and tumors showed significant downregulation of total transcriptional activity of HS biosynthetic system and changes in overall expression patterns in prostate cancer, 33 whereas in colon cancer only qualitative changes in expression patterns are detected.…”

“…[35][36][37] Earlier, a similar idea was applied in few studies, where expression of a number of GAG biosynthesis-involved genes in different normal and cancer tissues were investigated simultaneously, [30][31][32] however the obtained results were not analyzed in terms of a common expression pattern of the system.…”

“…31 Most of the studied genes for HS biosynthetic machinery show no changes or similar expression changes in non-metastatic or metastatic infiltrating ductal adenocarcinomas (IDCs) but sulfotransferase HS3ST5 is decreased in non-metastatic tumors and not changed in metastatic tumors, and SULF1 and SULF2 show overexpression in non-metastatic and no change in metastatic tumors. 32 All the data advocate for close association of HS biosynthetic system with tumor development and metastatic process although molecular mechanisms of the association remain unknown. Possibly, malignant cells with deteriorated HS composition at the cell surface may survive inside the tumor node only, where they do not contact with other cell types and could not be recognized and eliminated by immune system.…”

Insights into the key roles of proteoglycans in breast cancer biology and translational medicine

“…Cell surface-associated HSPGs have been described as tumor biomarkers being differentially regulated during tumorigenesis [3, 24, 25]. Recently, a direct relationship between growth factor-mediated signaling, ERs and ECM components has been shown.…”

“…Notably, this study also showed that glypican-1 stimulates the mitogenic response of two breast cancer cell lines to -heparin binding epidermal growth factor (HB-EGF) and to FGF2, suggesting that the up-regulation of glypican-1 could play a role in breast cancer progression. It should be noted, however, that a more recent study of 23 breast tumor samples by qRT-PCR could not detect significant over-expression of glypican-1 [24]. …”