O'Malley B W, Li D, Buckner A, Duan L, Woo S L, Pardoll D M
Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, Baltimore, MD 21287, USA.
Laryngoscope. 1999 Mar;109(3):389-95. doi: 10.1097/00005537-199903000-00009.
OBJECTIVE/HYPOTHESIS: Adenoviral interleukin-2 (AdV-IL-2) gene therapy has previously not proven effective in treating established murine oral cancer. We hypothesize that the intratumoral level of IL-2 expression is a major limiting factor in treatment outcome.
A microscopic disease and established oral cancer murine model was used to test this hypothesis. IL-2 gene transfer was performed with a recombinant adenovirus vector.
Tumor cells were transduced in vitro with AdV-IL-2 and subsequently implanted into the floor of the mouth in C3H/HeJ mice. IL-2 expression in vitro ranged from 990 to 1,050 pg/10(6) tumor cells. This microscopic disease treatment resulted in either complete tumor regression or a dramatic decrease in tumor progression. Cytolytic T-cell (CTL) assays demonstrated a predominance of CD8-specific, T-cell-mediated tumor killing. Reducing IL-2 expression by half with a mixture of 1:1 transduced to nontransduced tumor cells eliminated the antitumor effect and decreased the CTL response. These findings support the presence of a critical "threshold" of IL-2 expression. Adenovirus repurification and amplification allowed isolation of a twofold-higher-titer AdV-IL-2 vector. Treatment of established tumors with the higher-titer AdV-IL-2 at a new maximal dose of 1.4 x 10(9) plaque-forming units (pfu) increased in vivo IL-2 expression to 1,127 pg/10(6) cells and generated a significant antitumor response. Complete regression of established tumors, however, could not be achieved, and we noted a decrease in IL-2 expression well below the threshold at 1 week after treatment. Upon repeat maximal AdV-IL-2 injection in vivo, a greater antitumor effect and increased CTL response was seen, but also, 28% of the animals died of IL-2 toxicity.
Although limited by expression and toxicity as a single-treatment strategy for established tumors, AdV-IL-2 gene therapy should be considered a potential component of combination therapy strategies.
目的/假设：腺病毒白细胞介素-2（AdV-IL-2）基因疗法此前尚未被证明对已形成的小鼠口腔癌有效。我们假设肿瘤内白细胞介素-2的表达水平是治疗效果的主要限制因素。
使用微观疾病和已形成口腔癌的小鼠模型来验证这一假设。采用重组腺病毒载体进行白细胞介素-2基因转移。
肿瘤细胞在体外被AdV-IL-2转导，随后植入C3H/HeJ小鼠的口腔底部。体外白细胞介素-2的表达范围为990至1050 pg/10⁶肿瘤细胞。这种微观疾病治疗导致肿瘤完全消退或肿瘤进展显著减缓。细胞毒性T细胞（CTL）检测表明，主要是CD8特异性的、T细胞介导的肿瘤杀伤作用。将转导与未转导的肿瘤细胞按1:1混合，使白细胞介素-2表达减半，消除了抗肿瘤作用并降低了CTL反应。这些发现支持白细胞介素-2表达存在关键“阈值”。腺病毒的再纯化和扩增使得能够分离出滴度高两倍的AdV-IL-2载体。用新的最大剂量1.4×10⁹空斑形成单位（pfu）的高滴度AdV-IL-2治疗已形成肿瘤，可使体内白细胞介素-2表达增加至1127 pg/10⁶细胞，并产生显著的抗肿瘤反应。然而，已形成的肿瘤无法完全消退，并且我们注意到治疗后1周白细胞介素-2表达降至阈值以下。在体内重复注射最大剂量的AdV-IL-2后，观察到更大的抗肿瘤作用和增强的CTL反应，但同时，28%的动物死于白细胞介素-2毒性。
尽管作为已形成肿瘤的单一治疗策略受到表达和毒性的限制，但AdV-IL-2基因疗法应被视为联合治疗策略的潜在组成部分。
