Expression of sialyl Lewis X (SLeX) is a well-documented event during malignant transformation of cancer cells, and largely associates with their invasive and metastatic properties. Glycoproteins and glycolipids are the main carriers of SLeX, whose biosynthesis is known to be performed by different glycosyltransferases, namely by the family of β-galactoside-α2,3-sialyltransferases (ST3Gals). In this study, we sought to elucidate the role of ST3GalIV in the biosynthesis of SLeX and in malignant properties of gastrointestinal (GI) cancer cells. By immunofluorescent screening, we selected SLeX-positive GI cancer cell lines and silenced ST3GalIV expression via CRISPR/Cas9. Flow cytometry, immunofluorescence and western blot analysis showed that ST3GalIV KO efficiently impaired SLeX expression in most cancer cell lines, with the exception of the colon cancer cell line LS174T. The impact of ST3GalIV KO in the biosynthesis of SLeX isomer SLeA and non sialylated Lewis X and A were also evaluated and overall, ST3GalIV KO led to a decreased expression of SLeA and an increased expression in both LeX and LeA. In addition, the abrogation of SLeX on GI cancer cells led to a reduction in cell motility. Furthermore, ST3GalVI KO was performed in LS174T ST3GalIV KO cells, resulting in the complete abolishment of SLeX expression and consequent reduced motility capacity of those cells. Overall, these findings portray ST3GalIV as the main, but not the only, enzyme driving the biosynthesis of SLeX in GI cancer cells, with a functional impact on cancer cell motility.

唾液酸路易斯 X (SLeX) 的表达是癌细胞恶性转化过程中一个有据可查的事件，并且很大程度上与其侵袭和转移特性相关。糖蛋白和糖脂是SLeX的主要载体，其生物合成已知是由不同的糖基转移酶进行的，即β-半乳糖苷-α2,3-唾液酸转移酶家族(ST3Gals)。在这项研究中，我们试图阐明 ST3GalIV 在 SLeX 生物合成和胃肠道 (GI) 癌细胞恶性特性中的作用。通过免疫荧光筛选，我们选择了 SLeX 阳性的胃肠道癌细胞系，并通过 CRISPR/Cas9 沉默 ST3GalIV 的表达。流式细胞术、免疫荧光和蛋白质印迹分析表明，ST3GalIV KO 可有效削弱大多数癌细胞系中的 SLeX 表达，但结肠癌细胞系 LS174T 除外。还评估了 ST3GalIV KO 对 SLeX 异构体 SLeA 和非唾液酸化 Lewis X 和 A 生物合成的影响，总体而言，ST3GalIV KO 导致 SLeA 表达减少，LeX 和 LeA 表达增加。此外，废除 SLeX 对胃肠道癌细胞会导致细胞运动性降低。此外，在 LS174T ST3GalIV KO 细胞中进行 ST3GalVI KO，导致 SLeX 表达完全消除，从而降低这些细胞的运动能力。总体而言，这些发现将 ST3GalIV 描述为驱动胃肠道癌细胞中 SLeX 生物合成的主要（但不是唯一）酶，对癌细胞运动具有功能性影响。