Suppression of the grainyhead transcription factor 2 gene (GRHL2) inhibits the proliferation, migration, invasion and mediates cell cycle arrest of ovarian cancer cells

Previously, we have identified the Grainyhead transcription factor 2 gene (GRHL2) as notably hypomethylated in high-grade (HG) serous epithelial ovarian tumors, compared with normal ovarian tissues. GRHL2 is known for its functions in normal tissue development and wound healing. In the context of cancer, the role of GRHL2 is still ambiguous as both tumorigenic and tumor suppressive functions have been reported for this gene, although a role of GRHL2 in maintaining the epithelial status of cancer cells has been suggested. In this study, we report that GRHL2 is strongly overexpressed in both low malignant potential (LMP) and HG serous epithelial ovarian tumors, which probably correlates with its hypomethylated status. Suppression of the GRHL2 expression led to a sharp decrease in cell proliferation, migration and invasion and induced G1 cell cycle arrest in epithelial ovarian cancer (EOC) cells displaying either epithelial (A2780s) or mesenchymal (SKOV3) phenotypes. However, no phenotypic alterations were observed in these EOC cell lines following GRHL2 silencing. Gene expression profiling and consecutive canonical pathway and network analyses confirmed these data, as in both these EOC cell lines, GRHL2 ablation was associated with the downregulation of various genes and pathways implicated in cell growth and proliferation, cell cycle control and cellular metabolism. Taken together, our data are indicative for a strong oncogenic potential of the GRHL2 gene in EOC progression and support recent findings on the role of GRHL2 as one of the major phenotypic stability factors (PSFs) that stabilize the highly aggressive/metastatic hybrid epithelial/mesenchymal (E/M) phenotype of cancer cells.

既往研究中，我们发现相较于正常卵巢组织，高级别（HG）浆液性上皮性卵巢肿瘤中Grainyhead转录因子2基因（GRHL2）呈现显著低甲基化状态。GRHL2的已知功能涉及正常组织发育与伤口愈合。在癌症研究语境下，GRHL2的作用仍存在争议：尽管有研究提示其可维持癌细胞的上皮表型，但该基因既被报道具有致瘤性功能，也被发现存在抑瘤性功能，二者并存使其角色暧昧不明。本研究中，我们发现GRHL2在低恶性潜能（LMP）与高级别（HG）浆液性上皮性卵巢肿瘤中均呈显著过表达，这一现象或与其低甲基化状态相关。抑制GRHL2的表达后，无论携带上皮型（A2780s）还是间质型（SKOV3）表型的上皮性卵巢癌（EOC）细胞，其增殖、迁移与侵袭能力均大幅下降，并可诱导G1期细胞周期阻滞。然而，对上述上皮性卵巢癌细胞系进行GRHL2基因沉默后，未观察到任何表型改变。基因表达谱分析及后续的经典通路与网络分析验证了上述结果：在这两株上皮性卵巢癌细胞系中，GRHL2敲除均与一系列参与细胞生长增殖、细胞周期调控及细胞代谢的基因与通路的下调相关。综上，我们的研究结果提示GRHL2基因在上皮性卵巢癌进展中具有较强的致癌潜能，并支持近期的相关发现——即GRHL2作为主要表型稳定性因子（PSFs）之一，可稳定癌细胞极具侵袭性/转移性的混合型上皮/间质（E/M）表型。