MEN1 Deficiency-Driven Activation of the β-Catenin-MGMT Axis Promotes Pancreatic Neuroendocrine Tumor Growth and Confers Temozolomide Resistance
》》Journal：Adv Sci (Weinh) .
》》相关产品：Temozolomide (SJ-MX0064) 和 O6-Benzylguanine (SJ-MX3716)
》》产品引用描述：
》》Abstract
O6-methylguanine DNA methyltransferase (MGMT) removes alkyl adducts from the guanine O6 position (O6-MG) and repairs DNA damage. High MGMT expression results in poor response to temozolomide (TMZ). However, the biological importance of MGMT and the mechanism underlying its high expression in pancreatic neuroendocrine tumors (PanNETs) remain elusive. Here, it is found that MGMT expression is highly elevated in PanNET tissues compared with paired normal tissues and negatively associated with progression-free survival (PFS) time in patients with PanNETs. Knocking out MGMT inhibits cancer cell growth in vitro and in vivo. Ectopic MEN1 expression suppresses MGMT transcription in a manner that depends on β-Catenin nuclear export and degradation. The Leucine 267 residue of MEN1 is crucial for regulating β-Catenin-MGMT axis activation and chemosensitivity to TMZ. Interference with β-Catenin re-sensitizes tumor cells to TMZ and significantly reduces the cytotoxic effects of high-dose TMZ treatment, and MGMT overexpression counteracts the effects of β-Catenin deficiency. This study reveals the biological importance of MGMT and a new mechanism by which MEN1 deficiency regulates its expression, thus providing a potential combinational strategy for treating patients with TMZ-resistant PanNETs.
》》部分文献数据展示：
Fig 8. Alterations in the 𝛽-Catenin-MGMT axis re-sensitize PanNETs to TMZ. A) Silencing of 𝛽-Catenin disrupted the 𝛽-Catenin-MGMT signaling pathway upon the treatment of TMZ. QGP-1 cells were transfected individually with siControl or si𝛽-Catenin for 24 h, then treated with 300 μm TMZ or DMSO for 48 h, and subjected to immunoblotting using antibodies against 𝛽-Catenin and MGMT with actin as a loading control. B,C) Knockdown of 𝛽-Catenin significantly reduced IC50 of TMZ in QGP-1 cells. QGP-1 cells were transfected individually by siControl, si𝛽-Catenin-1# or si𝛽-Catenin-2# and treated with indicated dose of TMZ for 48 h, and then subjected to CCK8 assay (**P < 0.01, n = 3).D,E) The antagonists of 𝛽-Catenin also reduced IC50 of TMZ in QGP-1 cells. QGP-1 cells were treated by two antagonists of 𝛽-Catenin, combined with indicated dose of TMZ for 48 h, and then subjected to CCK8 assay (**P < 0.01, n = 3). F) The antagonists of 𝛽-Catenin increased the tumor chemosensitivity to TMZ. QGP-1 cells were treated by two antagonists of 𝛽-Catenin, combined with 300 μm TMZ and then subjected to CCK8 assay for indicated time points (*P < 0.05, **P < 0.01, n = 3). G,H) Overexpression of MGMT rescued 𝛽-Catenin depletion-leading to inhibition of colony formation upon TMZ treatment in QGP-1 cells. MGMT or negative control- overexpressing stable QGP-1 cells were transfected individually by siCtrl or si𝛽-Catenin for 24 h, and treated with 300 μm TMZ for 10 days, and then subjected to colony formation assay (***P < 0.001, **P < 0.01, n = 3).
Fig 3. F) O6-BG induced the accumulation of Wee1, p27, p21, C-PARP, BAD, and BAX in a dose-dependent manner. Forty-eight hours after QGP-1 cells treated with O6-BG at increasing concentrations (50, 75, and 100 μm) vs DMSO, cells were subjected to immunoblotting using antibodies against the indicated proteins with actin as a loading control. G) O6-BG induced the accumulation of Wee1, p27, p21, C-PARP, BAD, and BAX in a time-dependent manner. QGP-1 cells were treated with 75 μm O6-BG at increasing time points, and then subjected to immunoblotting using antibodies against the indicated proteins with actin as a loading control.
