肺癌是全世界死亡率最高的癌症，因為患者在確診時已處於晚期。高轉移率使其成為最致命的人類癌。因此，了解癌症進展和轉移的分子機制對於改善治療和預後至關重要。膽固醇是細胞膜的重要組成部分，對於多種細胞功能都是必需的。一些研究顯示，高水平的膽固醇與不同類型的癌症的不良預後有關。研究表明GRAMD1B是一種脂質結合蛋白，在癌細胞中已被證實是膽固醇轉運和代謝的調節因子。然而，GRAMD1B在非小細胞肺癌中的角色尚不清楚。在我們的實驗中，我們確定GRAMD1B與肺腫瘤和不良的臨床預後呈正相關。此外，與低轉移的CL1-0細胞相比，GRAMD1B在高轉移的CL1-5肺癌細胞中高度表達。此外，通過功能性實驗，我們發現GRAMD1B在非小細胞肺癌細胞中促進了細胞遷移、細胞的非貼附性生長和癌幹性特性。最後，我們試圖探索由GRAMD1B調節的分子機制，並通過RNAseq的通路富集分析和GRAMD1B過度表達的CL1-0細胞中膽固醇酯的增加，我們發現GRAMD1B可能調節膽固醇平衡。通過ACAT1抑制劑avasimibe抑制膽固醇酯化，可以抑制CL1-5和GRAMD1B過度表達的CL1-0細胞的細胞遷移。結論是這項研究確立了在非小細胞肺癌中，GRAMD1B透過ACAT1和NPC1L1調控膽固醇平衡，促進了肺癌細胞的遷移、非貼附性生長和癌幹性特性。

Globally, lung cancer is the leading cause of cancer death because of the high rate of metastasis. Thus, understanding the molecular mechanisms underlying cancer progression and metastasis is important to improve the treatment and prognosis. Cholesterol is an essential component of cell membranes and is required for various cellular functions. Several studies have shown that high levels of cholesterol are associated with poor prognosis in various types of cancer. GRAMD1B, a lipid-binding protein, has been identified as a regulator of cholesterol trafficking and metabolism in cancer cells. However, the role of GRAMD1B in non-small cell lung cancer is unknown. In this study, we identified that GRAMD1B was positively correlated with lung tumors and poor clinical outcomes. Moreover, GRAMD1B was highly expressed in high metastatic CL1-5 lung cancer cells, compared to low metastatic CL1-0 cells. Furthermore, by functional assays, we found that GRAMD1B promoted cell migration, anchorage-independent cell growth, and cancer stemness property in NSCLC cells. Finally, we tried to explore the molecular mechanisms regulated by GRAMD1B and found that GRAMD1B may regulate cholesterol homeostasis according to the pathway enrichment analysis of RNAseq results and the increase of cholesterol ester in GRAMD1B-overexpressed CL1-0 cells. Inhibition of the esterification of cholesterol by an ACAT1 inhibitor, avasimibe, suppressed cell migration of CL1-5 and GRAMD1B-overexpressed CL1-0 cells. In conclusion, this study established that GRAMD1B promoted lung cancer cell migration, anchorage-independent growth, and stemness property by regulating cholesterol homeostasis through ACAT1 and NPC1L1 in NSCLC.

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