B4GALT1 調節基質-整合素相互作用以控制肝細胞癌轉移

Abstract

Beta1,4-半乳糖轉移酶（B4GALTs）在各種疾病中扮演關鍵角色，包括癌症。其中，B4GALT1在肝臟中高度表達，而患有B4GALT1基因突變的人通常會罹患肝病。然而，B4GALT1對肝癌的影響長期以來一直未明確。在這項研究中，我們發現相對於相鄰的正常肝組織，肝細胞癌組織中B4GALT1明顯下降。此外，我們還發現低B4GALT1表現與肝細胞癌患者的血管侵犯性增加以及整體存活率下降有關。進一步的研究顯示，B4GALT1的沉默或缺失增加了體外肝細胞癌細胞的遷移和侵犯性，並在小鼠中促使肺轉移。值得注意的是，我們的研究揭示了B4GALT1影響肝細胞癌細胞與laminin層黏蛋白的黏附之間的聯繫。B4GALT1的沉默或缺失增加了細胞的黏附，而B4GALT1的過度表達則產生了相反的效應。通過質譜和Griffonia simplicifolia凝集素II（GSL-II）拉下實驗，我們確定了integrin整合素α6和β1是B4GALT1的主要蛋白質受質，B4GALT1通過修改它們的N-glycan進行調控。由於B4GALT1下調，導致細胞遷移和侵犯性增強，這種效應可以通過使用抗α6或抗β1整合素的阻斷抗體明顯逆轉。這些發現表明B4GALT1的下調導致N-glycan修飾的改變，提高了整合素α6和β1對層黏蛋白的結合能力，從而促進了肝細胞癌細胞的侵犯性。整體而言，我們的研究增加了對B4GALT1在肝細胞癌轉移的作用的理解，並指出針對B4GALT1表達下降的肝細胞癌患者，以層黏蛋白-整合素作為潛在治療策略的重要性。

Beta-1,4-galactosyltransferases, particularly B4GALT1, are crucial enzymes implicated in various diseases, including cancer. B4GALT1''s high expression in the liver and its association with liver diseases is established, but its role in liver cancer has been uncertain. This investigation reveals that B4GALT1 is significantly underexpressed in hepatocellular carcinoma (HCC) compared to non-cancerous liver tissue. This downregulation correlates with more pronounced vascular invasion and a poorer overall survival rate for those affected by HCC. Experimentally, B4GALT1 inhibition or elimination heightened HCC cell migratory and invasive behavior in vitro, and also increased the occurrence of lung metastases in animal models. Furthermore, B4GALT1 was found to be intricately linked to cell adhesion to laminin; reductions in B4GALT1 facilitated cellular adhesion, while its overexpression reduced it. Integrins α6 and β1 were pinpointed as primary substrates altered by B4GALT1 via N-glycosylation, a process discernible through mass spectrometry and lectin pull-down assays. Counteracting the effects of reduced B4GALT1 on cell movement and invasiveness was possible by employing antibodies against integrins α6 or β1. Overall, the study posits that diminished B4GALT1 expression contributes to the invasive potential of HCC cells by affecting the N-glycosylation and hence the binding dynamics of integrin-laminin. Consequently, this research not only advances our understanding of B4GALT1''s role in HCC metastasis but also highlights targeting integrin-laminin interactions as a promising therapeutic avenue for HCC patients with low B4GALT1 expression.