Expression profiling of glycosyltransferases and related enzymes using in situ hybridization

Modification of sialylation is associated with multidrug resistance in human acute myeloid leukemia

Aberrant cell surface sialylation patterns have been shown to correlate with tumor progression and metastasis. However, the role of sialylation regulation of cancer multidrug resistance (MDR) remains poorly understood. This study investigated sialylation in modification on MDR in acute myeloid leukemia (AML). Using mass spectrometry (MS) analysis, the composition profiling of sialylated N-glycans differed in three pairs of AML cell lines. Real-time PCR showed the differential expressional profiles of 20 sialyltransferase (ST) genes in the both AML cell lines and bone marrow mononuclear cells (BMMCs) of AML patients. The expression levels of ST3GAL5 and ST8SIA4 were detected, which were overexpressed in HL60 and HL60/adriamycin-resistant (ADR) cells. The altered levels of ST3GAL5 and ST8SIA4 were found in close association with the MDR phenotype changing of HL60 and HL60/ADR cells both in vitro and in vivo. Further data demonstrated that manipulation of these two genes' expression modulated the activity of phosphoinositide-3 kinase (PI3K)/Akt signaling pathway and its downstream target thus regulated the proportionally mutative expression of P-glycoprotein (P-gp) and MDR-related protein 1 (MRP1), both of which are known to be involved in MDR. Blocking the PI3K/Akt pathway by its specific inhibitor LY294002 or by Akt small interfering RNA resulted in the reduced chemosensitivity of HL60/ADR cells. Therefore, this study indicated that sialylation involved in the development of MDR of AML cells probably through ST3GAL5 or ST8SIA4 regulating the activity of PI3K/Akt signaling and the expression of P-gp and MRP1.

Glycomic alterations are associated with multidrug resistance in human leukemia

Correlations of disease phenotypes with glycosylation changes have been analyzed intensively in tumor biology field. In this study we describe glycomic alterations of multidrug resistance in human leukemia cell lines. Using multiple glycan profiling tools: real-time PCR for quantification of glycogenes, FITC-lectin binding for glycan profiling, and mass spectrometry for glycan composition, we compared the glycomics of drug-resistant K562/ADR cells with parental K562 line. The results showed that the expression of glycogenes, glycan profiling and N-glycan composition were different in K562/ADR cells, as compared with those in K562 cells, whereas O-glycans of the two cell lines showed no different mass spectra. Further analysis of the N-glycan regulation by way of tunicamycin application or PNGase F treatment in K562/ADR cells showed partial inhibition of biosynthesis and increased sensitivity to chemotherapeutic drugs in vitro. We targeted glycogene B3GNT8 and ST8SIA4, which were over-expressed in K562/ADR cells, and silenced the expression levels of two glycogenes after using RNA interference approach. The results showed that the silencing of B3GNT8 or ST8SIA4 in K562/ADR cells resulted in increased chemosensitivity to anti-tumor drugs. In conclusion, glycomic alterations are responsible for the overcoming multidrug resistance in human leukemia therapy and the N-linked oligosaccharides are associated with the drug resistance of cancer cells.

Critical role of bone marrow apoptosis-associated speck-like protein, an inflammasome adaptor molecule, in neointimal formation after vascular injury in mice

BACKGROUND

Inflammatory cytokines such as interleukin (IL)-1 beta and IL-18 play an important role in the development of atherosclerosis and restenosis. Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is an adaptor protein that regulates caspase-1-dependent IL-1 beta and IL-18 generation; however, the role of ASC in vascular injury remains undefined. Here, we investigated the contribution of ASC to neointimal formation after vascular injury in ASC-deficient (ASC(-/-)) mice.

METHODS AND RESULTS

Wire-mediated vascular injury was produced in the femoral artery of ASC(-/-) and wild-type mice. Immunohistochemical analysis revealed that ASC was markedly expressed at the site of vascular injury. Neointimal formation was significantly attenuated in ASC(-/-) mice after injury. IL-1 beta and IL-18 were expressed in the neointimal lesion in wild-type mice but showed decreased expression in the lesion of ASC(-/-) mice. To investigate the contribution of bone marrow-derived cells, we developed bone marrow-transplanted mice and found that neointimal formation was significantly decreased in wild-type mice in which bone marrow was replaced with ASC(-/-) bone marrow cells. Furthermore, in vitro experiments showed that the proliferation activity of ASC(-/-) vascular smooth muscle cells was not impaired.

CONCLUSIONS

These findings suggest that bone marrow-derived ASC is critical for neointimal formation after vascular injury and identify ASC as a novel therapeutic target for atherosclerosis and restenosis.

The utility of formalin-fixed and paraffin-embedded tissue blocks for quantitative analysis of N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase mRNA expressed by colorectal cancer cells

N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST) is a sulfotransferase responsible for biosynthesis of chondroitin sulfate E (CS-E). CS-E plays important roles in numerous biological events, such as neurite outgrowth. However, the role of GalNAc4S-6ST in tumor progression remains unknown. In the present study, we analyzed expression of GalNAc4S-6ST mRNA in colorectal cancer by combining real-time RT-PCR with in situ hybridization (ISH) using archived formalin-fixed and paraffin-embedded tissue sections. In 57.5% of 40 patients, expression of GalNAc4S-6ST mRNA was increased in cancer tissues compared with paired normal mucosa. ISH using an RNA probe specific for GalNAc4S-6ST revealed that it was expressed in colorectal cancer cells. Analysis of the relationship between expression of GalNAc4S-6ST as determined by real-time RT-PCR assay and various clinicopathological variables revealed that GalNAc4S-6ST was associated with vessel invasion, although a statistically significant difference was not seen (P=0.125 for lymphatic vessel invasion and P=0.242 for venous invasion). Taken together, we show that real-time RT-PCR combined with ISH is useful to investigate quantitatively GalNAc4S-6ST mRNA expression in formalin-fixed and paraffin-embedded tissue sections, and that GalNAc4S-6ST expressed by colorectal cancer cells plays a minor role in tumor progression.