Department of Biomedicine, University of Bergen, Bergen, Norway.
Department of Pathology, Haukeland University Hospital, Bergen, Norway.
Neuro Oncol. 2019 Jul 11;21(7):890-900. doi: 10.1093/neuonc/noz060.
Suicide gene therapy for malignant gliomas has shown encouraging results in the latest clinical trials. However, prodrug application was most often restricted to short-term treatment (14 days), especially when replication-defective vectors were used. We previously showed that a substantial fraction of herpes simplex virus thymidine kinase (HSV-TK) transduced tumor cells survive ganciclovir (GCV) treatment in an orthotopic glioblastoma (GBM) xenograft model. Here we analyzed whether these TK+ tumor cells are still sensitive to prodrug treatment and whether prolonged prodrug treatment can enhance treatment efficacy.
Glioma cells positive for TK and green fluorescent protein (GFP) were sorted from xenograft tumors recurring after suicide gene therapy, and their sensitivity to GCV was tested in vitro. GBM xenografts were treated with HSV-TK/GCV, HSV-TK/valganciclovir (valGCV), or HSV-TK/valGCV + erlotinib. Tumor growth was analyzed by MRI, and survival as well as morphological and molecular changes were assessed.
TK-GFP+ tumor cells from recurrent xenograft tumors retained sensitivity to GCV in vitro. Importantly, a prolonged period (3 mo) of prodrug administration with valganciclovir (valGCV) resulted in a significant survival advantage compared with short-term (3 wk) application of GCV. Recurrent tumors from the treatment groups were more invasive and less angiogenic compared with primary tumors and showed significant upregulation of epidermal growth factor receptor (EGFR) expression. However, double treatment with the EGFR inhibitor erlotinib did not increase therapeutic efficacy.
Long-term treatment with valGCV should be considered as a replacement for short-term treatment with GCV in clinical trials of HSV-TK mediated suicide gene therapy.
恶性神经胶质瘤的自杀基因治疗在最近的临床试验中显示出可喜的结果。然而，前药的应用最常局限于短期治疗（14 天），尤其是在使用复制缺陷型载体时。我们之前的研究表明，在荷瘤原位神经胶质瘤（GBM）异种移植模型中，相当一部分转导了单纯疱疹病毒胸苷激酶（HSV-TK）的肿瘤细胞在更昔洛韦（GCV）治疗下存活下来。在这里，我们分析这些 TK+肿瘤细胞是否仍然对前药治疗敏感，以及延长前药治疗是否可以增强治疗效果。
从自杀基因治疗后复发的异种移植肿瘤中分离出 TK 和绿色荧光蛋白（GFP）阳性的神经胶质瘤细胞，并在体外检测其对 GCV 的敏感性。用 HSV-TK/GCV、HSV-TK/缬更昔洛韦（valGCV）或 HSV-TK/valGCV+厄洛替尼处理 GBM 异种移植。通过 MRI 分析肿瘤生长，评估生存以及形态和分子变化。
来自复发异种移植肿瘤的 TK-GFP+肿瘤细胞在体外保留了对 GCV 的敏感性。重要的是，与 GCV 的短期（3 周）应用相比，用 valGCV 延长前药（3 个月）给药时间可显著延长生存时间。与原发性肿瘤相比，治疗组的复发性肿瘤侵袭性更强，血管生成较少，表皮生长因子受体（EGFR）表达显著上调。然而，用 EGFR 抑制剂厄洛替尼进行双重治疗并没有增加治疗效果。
在 HSV-TK 介导的自杀基因治疗的临床试验中，应考虑用 valGCV 进行长期治疗，以替代 GCV 的短期治疗。
