Liu Ta-Chiang, Wakimoto Hiroaki, Martuza Robert L, Rabkin Samuel D
Molecular Neurosurgery Laboratory, Brain Tumor Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Clin Cancer Res. 2007 Oct 1;13(19):5897-902. doi: 10.1158/1078-0432.CCR-07-1013.
Oncolytic herpes simplex virus (HSV) vectors have shown safety in clinical trials, but efficacy remains unsatisfactory. Novel HSV vectors that possess tumor selectivity with enhanced potency are therefore needed. The gene product of HSV Us3 protects virus-infected cells from apoptosis, a cellular pathway frequently dysfunctional in tumors. We hypothesized that Us3 mutants, whose replication would be inhibited by apoptosis in normal cells, would be selective for tumor cells.
HSV mutants G207 (ribonucleotide reductase-/gamma34.5-), R7041 (Us3-), and R7306 (Us3 revertant) were tested in normal and tumor cells for viral replication, antitumoral potency, apoptosis induction, and Akt activation. Safety and biodistribution after systemic administration and antitumoral efficacy after intratumoral (i.t.) or i.v. administration were examined.
Us3 deletion results in up to 3-log replication inhibition in normal cells, which correlates with enhanced apoptosis induction. In contrast, R7041 replicates very well in tumor cells, showing 1 to 2 log greater yield than G207. In vivo, R7041 shows no signs of toxicity after systemic delivery in both immunocompetent and immunodeficient mice and shows preferential and prolonged replication in tumors compared with normal tissues. R7041 displays significant antitumoral efficacy after i.t. or i.v. administration. An additional feature of Us3 mutants is enhanced Akt activation compared with wild-type infection, which sensitizes cells to phosphatidylinositol 3-kinase-Akt inhibitors (LY294002, Akt inhibitor IV), shown by synergistic antitumoral activity in vitro and enhanced efficacy in vivo.
Us3 deletion confers enhanced tumor selectivity and antitumoral potency on herpes simplex virus-1 and provides for a novel mechanism of combination therapy with phosphatidylinositol 3-kinase-Akt-targeting molecular therapeutics.
溶瘤单纯疱疹病毒（HSV）载体在临床试验中已显示出安全性，但疗效仍不尽人意。因此，需要具有更高效力且具有肿瘤选择性的新型HSV载体。HSV Us3的基因产物可保护病毒感染的细胞免于凋亡，而凋亡是肿瘤中经常功能失调的细胞途径。我们假设，其复制会在正常细胞中被凋亡抑制的Us3突变体对肿瘤细胞具有选择性。
对HSV突变体G207（核糖核苷酸还原酶 - /γ34.5 - ）、R7041（Us3 - ）和R7306（Us3回复体）在正常细胞和肿瘤细胞中进行病毒复制、抗肿瘤效力、凋亡诱导和Akt激活的测试。检查全身给药后的安全性和生物分布以及瘤内（i.t.）或静脉内（i.v.）给药后的抗肿瘤疗效。
Us3缺失导致正常细胞中病毒复制抑制高达3个对数级，这与增强的凋亡诱导相关。相比之下，R7041在肿瘤细胞中复制良好，产量比G207高1至2个对数级。在体内，R7041在免疫健全和免疫缺陷小鼠全身给药后均未显示毒性迹象，并且与正常组织相比，在肿瘤中显示出优先且持久的复制。R7041在瘤内或静脉内给药后显示出显著的抗肿瘤疗效。与野生型感染相比，Us3突变体的另一个特征是增强的Akt激活，这使细胞对磷脂酰肌醇3 - 激酶 - Akt抑制剂（LY294002，Akt抑制剂IV）敏感，体外协同抗肿瘤活性和体内增强疗效表明了这一点。
Us3缺失赋予单纯疱疹病毒1型增强的肿瘤选择性和抗肿瘤效力，并提供了一种与靶向磷脂酰肌醇3 - 激酶 - Akt的分子疗法联合治疗的新机制。
