Development of novel therapeutic strategies based on the molecular analyses of tumor cells in animal lymphomas

在过去的30年里，大量的治疗犬淋巴肿瘤的临床试验被报道；然而，患者的预后并没有明显的改善。本研究旨在基于肿瘤细胞的分子分析开发新的治疗策略。在肿瘤细胞耐药方面，检测了药物外排泵、药物代谢分子、细胞周期调节分子和细胞凋亡相关分子。结果表明，犬耐药淋巴样肿瘤中药物外排泵之一p -糖蛋白（P-gp）表达升高，编码细胞周期/凋亡相关分子的p53基因突变。接下来，我们建立了一套定量测定淋巴样细胞中重排免疫球蛋白和t细胞受体基因拷贝数的系统。该检测系统能够量化化疗后少量残留肿瘤细胞，即最小残留病（MRD）。即使在诱导完全缓解后，狗也可以检测到MRD，并在复发前1~2个月逐渐增加。化疗结束时MRD的量与缓解至复发的持续时间呈负相关。这些结果表明，MRD可以作为比较不同化疗方案疗效的客观指标，也可以作为犬淋巴瘤复发的负面预后因素。此外，本研究引入了一种基于每个阶段/患者MRD水平的量身定制的治疗方法。由于犬淋巴样肿瘤可以被认为是人类疾病的动物模型，本研究为开发新的人类淋巴样肿瘤治疗策略提供了有用的信息。

For the past 30 years, a large number of therapeutic clinical trials for canine lymphoid tumors were reported; however, apparent improvement on the outcome of the patients has not been obtained. The present study was carried out to aim at the development of novel therapeutic strategies based upon the molecular analyses of the tumor cells.With respect to the drug resistance of the tumor cells, drug efflux pumps, drug metabolizing molecules, cell cycle-regulating molecules, and apoptosis-associated molecules were examined. The results indicated that increased expression of P-glycoprotein (P-gp), one of the drug efflux pump, and mutation of p53 gene encoding cell cycle/apoptosis-associated molecule were found in drug-resistant lymphoid tumors in dogs.Next, we established an assay system to quantify the copy number of rearranged immunoglobulin and T-cell receptor genes in lymphoid cells. The assay system enabled the quantification of a small number of residual tumor cells after chemotherapy, namely minimal residual disease (MRD). MRD could be detected in dogs even after induction of complete remission and gradually increased 1～2 months before relapse. The amount of MRD at the end of chemotherapy was negatively correlated with the remission duration until relapse. These findings indicated that the MRD could be an objective marker to compare the efficacy of different chemotherapeutic protocols and a negative prognostic factor for the relapse in canine lymphoma. Furthermore, the present study introduced a tailor-made therapy based on the MRD level in each phase/patient.Because the lymphoid tumors in dogs can be recognized as an animal model of the human disease, the present study provided useful information to develop novel therapeutic strategies in lymphoid tumors in humans.