Altered Sialylation and Sialyltransferase Expression in Gynecologic Cancers

Functions of Sialyltransferases in gynecological malignancies: A systematic review

INTRODUCTION

The biosynthesis of tumor-associated sialoglycans involves Sialyltransferases expressed in cancer cells differentially. The current review aspires to bridge the existing knowledge gaps by consolidating evidence regarding the role of Sialyltransferases in gynecological malignant tumors (ovarian, cervix, endometrial, and breast).

METHODS

In this systematic review, we searched databases, including PubMed, Embase, Web of Science, Scopus and Cochrane Library. Twenty-two high-quality articles were selected out of 559 researched studies using radiomics quality score (RQS) tools.

RESULTS

Our findings indicated that 7 articles were related to Sialyltransferases in ovarian cancer, in which 6 studies was examined only ST6Gal-I and one study examined the ST3Gal-I, ST3Gal-II, ST3Gal-III, ST3Gal-IV, ST3Gal-VI, and ST3Gal-6. In addition, 5 articles were related to Sialyltransferases in cervix cancer (ST6Gal-I), 3 articles to endometrial cancer (ST6Gal-I, ST3Gal-III, ST3Gal-IV, and ST3Gal-6), and 7 articles to breast cancer (ST6Gal-I gene in 5 studies, ST6GAL-II gene in one study, and ST8SIA1 and ST3GAL-V genes in one study).

CONCLUSION

ST6Gal-I gene expression occurs at a high speed in ovarian, cervix, endometrial, and breast cancers, leading to metastasis to distant cells, cell destruction, cell invasion, and reduced patient survival.

Alpha 2,6-sialyltransferase I expression in the placenta of patients with preeclampsia

BACKGROUND

The expression of sialyl-glycoconjugates changes during development, differentiation and oncogenic transformation, tumor invasion and metastasis. Similarly, in the early stage of pregnancy, trophoblast cells have to undergo adhesion, invasion, and proliferation to develop a healthy placenta; the cytobiologic behavior is similar to tumor growth and invasion. Inadequate trophoblast invasion to the spiral artery in the 2nd trimester of pregnancy was believed to be correlated with pregnancy complications, including preeclampsia.

METHODS

Alterations in alpha2,6-sialyltransferase I (ST6Gal I) mRNA in the placental tissues of women with preeclampsia (n=20) and without preeclampsia (n=20 used as a control) were examined by semiquantitative reverse transcription-polymerase chain reaction and real-time quantitative reverse transcription-polymerase chain reaction. The transcription regulators of ST6Gal I including a "constitutive" promoter (Y + Z form), "hepatic" promoter (H form), and lymphoblastic promoter (X form) were investigated. The enzyme activity of ST6Gal I was also examined.

RESULTS

Both mRNA expression and enzyme activity of ST6Gal I did not show a significant difference in the placental tissues of the women of both groups. The transcription regulators of ST6Gal I, including the Y+Z form and the H form, also failed to show any difference. The X form, seldom detected in the study, was excluded from analysis.

CONCLUSION

Our results suggested that ST6Gal I was not involved in the pathogenesis of the preeclampsia.

Soyasaponin I decreases the expression of alpha2,3-linked sialic acid on the cell surface and suppresses the metastatic potential of B16F10 melanoma cells

The transfer of sialic acids to the non-reducing terminal positions on sugar chains of glycoconjugates is catalyzed by sialyltransferases (STs). Increased sialylation is correlated with oncogenic transformation and metastatic potential. ST inhibitors may be potentially valuable as anti-cancer and anti-metastatic agents. In this study, we evaluated the effects of soyasaponin I (Ssa I), a known inhibitor of STs, on tumor metastasis through studying a highly metastatic cancer cell line B16F10. Ssa I specifically inhibited the expression of alpha2,3-linked sialic acids without affecting other glycans on the B16F10 cell surface. We also found that Ssa I decreased the migratory ability of cells, enhanced cell adhesion to extracellular matrix proteins. Finally, a pulmonary metastasis assay demonstrated that alteration of glycosylation in this way significantly reduced the ability of tumor cells to distribute to the lungs of mice. Collectively, these findings suggested that alpha2,3-linked sialic acids may play an important role in metastasis potential of B16F10 cells.

Soyasaponin-I-modified invasive behavior of cancer by changing cell surface sialic acids

OBJECTIVE

Sialylation involving tumor formation and invasive behavior goes along with altered sialyltransferase (ST) activity. A potent ST inhibitor, soyasaponin I (SsaI), was discovered to selectively inhibit the cellular alpha2,3-sialyltranserase activity. In this study, we further test the effects of SsaI on modifying the metastatic and invasive behaviors of cancer cell lines.

METHODS

Nonmetastatic breast cancer cell line, MCF-7, and highly metastastic breast cancer cell line, MDA-MB-231, were used to investigate the effects of SsaI on tumor cells.

RESULTS

SsaI did not affect cell growth cycle and also failed to inhibit cell growth in this study (the concentration of SsaI < or=100 muM). SsaI was as predicted to successfully inhibit cellular alpha2,3-ST activity and depressed the dose-dependent tumor cell surface alpha2,3-sialic acid expression. In addition, different concentrations of SsaI did stimulate MCF-7 cell adhesion to collagen type I linearly and significantly enhanced cell adhesion to the Matrigel-matrix. Furthermore, SsaI significantly decreased MDA-MB-231 cell migration. Reverse transcriptase polymerase chain reaction for evaluating mRNA expression of ST3Gal I, III and IV showed that SsaI also down-regulated the expression of ST3Gal IV but did not affect the other two.

CONCLUSIONS

The results showed that SsaI was implicated in the invasive behavior of tumor cells, suggesting that altered alpha2,3-sialylation pathway played a crucial role in the adhesion and tumor metastases. SsaI is a good candidate for studying the biological roles of ST, and might provide a new preventive strategy in tumor metastasis.