| 研究実績の概要 |
One problem with studying the mechanism of the PD-1 blockade therapy is the difficulty in identification of the tumor-reactive cytotoxic T cells (TR CTLs) because PD-1 blockade likely generates CTLs with a large repertoire of TCRs in response to a variety of tumor antigens {Tumeh, 2014, 25428505;McGranahan, 2016, 26940869}. To circumvent this problem, CellTrace-labeled CD45.1+ CD8+ T cells were transferred into CD45.2+ CD8-/- mice and their proliferation in DLN was examined assuming that tumor-activated CD8+ T cells will proliferate vigorously. The frequency and number of rapidly proliferating CD45.1+ CD8+ T cells increased in tumor-bearing mice treated with PD-L1 mAb compared with those injected with control IgG. Remarkably, PD-L1 mAb did not induce proliferation in the absence of tumor, strongly indicating that highly proliferating CD8+ T cells are indeed activated by tumor antigens.
In fact, compared with less dividing cells, highly proliferating CD8+ T cells in response to tumor antigens contained larger mitochondrial mass, higher mitochondrial membrane potential and more mitochondrial superoxide, clearly indicating activation of mitochondria in TR CTLs in vivo by PD-1 blockade. In agreement with this, the oxygen consumption rate (OCR), an indicator of mitochondrial respiration, and the ATP turnover were significantly higher in CD8+ T cells isolated from DLN of PD-L1 mAb-treated mice. Together these data demonstrate that increased mitochondrial activity in proliferating TR CTLs is associated with tumor regression by the PD-1 blockade therapy.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
One problem with studying the mechanism of the PD-1 blockade therapy is the difficulty in identification of the tumor-reactive cytotoxic T cells (TR CTLs) because PD-1 blockade likely generates CTLs with a large repertoire of TCRs in response to a variety of tumor antigens {Tumeh, 2014, 25428505;McGranahan, 2016, 26940869}. To circumvent this problem, CellTrace-labeled CD45.1+ CD8+ T cells were transferred into CD45.2+ CD8-/- mice and their proliferation in DLN was examined assuming that tumor-activated CD8+ T cells will proliferate vigorously. The frequency and number of rapidly proliferating CD45.1+ CD8+ T cells increased in tumor-bearing mice treated with PD-L1 mAb compared with those injected with control IgG. Remarkably, PD-L1 mAb did not induce proliferation in the absence of tumor, strongly indicating that highly proliferating CD8+ T cells are indeed activated by tumor antigens.
In fact, compared with less dividing cells, highly proliferating CD8+ T cells in response to tumor antigens contained larger mitochondrial mass, higher mitochondrial membrane potential and more mitochondrial superoxide, clearly indicating activation of mitochondria in TR CTLs in vivo by PD-1 blockade. In agreement with this, the oxygen consumption rate (OCR), an indicator of mitochondrial respiration, and the ATP turnover were significantly higher in CD8+ T cells isolated from DLN of PD-L1 mAb-treated mice. Together these data demonstrate that increased mitochondrial activity in proliferating TR CTLs is associated with tumor regression by the PD-1 blockade therapy.
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| 今後の研究の推進方策 |
A. Development of a novel and efficient combination therapy based on metabolic pathway modulation by small chemicals
Based on the results in the first year, we will chose the candidates of small chemicals that could modulate the energy metabolism modulating reactive oxygen species (ROS) generation. We will select small molecules based on their structure activity relationship to activate mitochondria. We will combine each of them with PD-1 blockade therapy and screen the best partner in the criteria of the enhancement of tumor regression activity and extension of survival of tumor-bearing mice.
B. Investigating the mechanism for the augmentation of antitumor immunity by combiation of the certain chemicals
Mechanistic Target Of Rapamycin (mTOR) and AMP-activated Protein Kinase (AMPK) are the energy sensors that control the balance of glycolysis and FAO. The balance of phosphorylation of mTOR and AMPK, therefore, is proposed to control the fate of CD8+ T cell activation and memory formation. In order to gain molecular insights of the enhancement of antitumor immunity in the above-mentioned combination approaches, phosphorylation level of mTOR and AMPK will be extensively investigated, which would clarify the function of the chemicals on tumor-reactive CD8+ T cells.
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