Sfondrini Lucia, Besusso Dario, Bronte Vincenzo, Macino Beatrice, Rossini Anna, Colombo Mario Paolo, Ménard Sylvie, Balsari Andrea
Molecular Targeting Unit, Department of Experimental Oncology, Istituto Nazionale Tumori, Via Venezian 1, 20133, Milan, Italy.
Cancer Immunol Immunother. 2004 Aug;53(8):697-704. doi: 10.1007/s00262-004-0516-x. Epub 2004 Mar 18.
Peritumoral CpG-oligodeoxynucleotide (ODN) treatment has been successful in tumor mouse models expressing strong antigens to induce activation of tumor-specific CD8+ T lymphocytes which contribute to the control of tumor growth. To get near to clinical reality, the tumor-specific CD8+ response was investigated in mice bearing the weakly immunogenic B16 melanoma tumor and using the melanocyte differentiation tyrosinase-related protein 2 (TRP-2) as a tracking antigen.
The expansion and activation of TRP-2-specific T lymphocytes by CpG-ODNs was analyzed by tetramer staining and IFN-gamma production assays, while the activity of these cells in both memory and primary response was evaluated in vivo.
After CpG-ODN treatment, the number of TRP-2 tetramer-stained CD8+ T lymphocytes was not significantly modified, but these cells produced higher levels of interferon gamma (IFN-gamma) in response to the antigen than those from untreated mice. Mice possessing these activated T lymphocytes, when evaluated for their antitumor memory response, showed marginal protection against intravenous (i.v.) and subcutaneous (s.c.) tumor rechallenge. These cells were not crucial for the control of primary tumor growth since strong reduction of subcutaneous tumor was observed after CpG-ODN treatment in both CD8+ T cell depleted or nondepleted mice. On the contrary, NK cell depletion markedly reduced CpG-ODN-induced tumor growth inhibition.
Altogether, these data indicate the CpG treatment activates tumor-reactive effector CD8+ T lymphocytes, but, paralleling recent clinical observations, our model indicates that the mere activation of antitumor T cells is insufficient to result in a clinical response.
肿瘤周围CpG-寡脱氧核苷酸（ODN）治疗在表达强抗原的肿瘤小鼠模型中已成功诱导肿瘤特异性CD8+ T淋巴细胞活化，有助于控制肿瘤生长。为了接近临床实际情况，在携带弱免疫原性B16黑色素瘤肿瘤的小鼠中，以黑素细胞分化酪氨酸酶相关蛋白2（TRP-2）作为追踪抗原，研究了肿瘤特异性CD8+反应。
通过四聚体染色和干扰素-γ产生试验分析CpG-ODN对TRP-2特异性T淋巴细胞的扩增和活化，同时在体内评估这些细胞在记忆和初次反应中的活性。
CpG-ODN治疗后，TRP-2四聚体染色的CD8+ T淋巴细胞数量无明显改变，但这些细胞对抗原产生的干扰素γ（IFN-γ）水平高于未治疗小鼠的细胞。对具有这些活化T淋巴细胞的小鼠进行抗肿瘤记忆反应评估时，发现其对静脉内（i.v.）和皮下（s.c.）肿瘤再攻击的保护作用较弱。这些细胞对原发性肿瘤生长的控制并非至关重要，因为在CD8+ T细胞耗竭或未耗竭的小鼠中，CpG-ODN治疗后均观察到皮下肿瘤明显缩小。相反，NK细胞耗竭显著降低了CpG-ODN诱导的肿瘤生长抑制。
总之，这些数据表明CpG治疗可激活肿瘤反应性效应CD8+ T淋巴细胞，但与最近的临床观察结果相似，我们的模型表明单纯激活抗肿瘤T细胞不足以产生临床反应。
