Accurate evaluation of drug effect on the LDH activity of live cells: dual measurement of live cell number by fluorescent staining of nucleus and LDH activity by formazan.

Effect of drugs on the intracellular activity of lactate dehydrogenase (LDH) has been measured by using water-soluble tetrazolium (WST). Because the assay is usually conducted in the presence of dead cells, net activity of live cells is not evaluated. Here, we reported the assay of the net intracellular LDH activity of live cells by counting the live cells using fluorescent staining of nucleus. By using a deep red fluorescent dye, dual measurements of fluorescence signal of nucleus and absorbance of WST could be conducted with transparent 96-well-plates. We found that conventional assay in the presence of dead cells overestimate the effect of drugs on the LDH activity.

In vitro evaluation of novel SN-38 prodrug activated by α-rhamnosidase of exogenous enzyme.

This study introduces the α-rhamnose (Rham)-conjugated prodrug of SN-38 (Rham-SN-38) as a promising alternative to irinotecan. α-rhamnosidase, responsible for SN-38 release from Rham-SN-38, does not express in human cells, minimizing individual variability and side effects. The injection of the α-rhamnosidase into the tumor tissues makes it possible, for the first time, to activate the Rham-SN-38. Furthermore, α-rhamnosidase demonstrates significantly higher activity than carboxylesterase, the specific enzyme activating irinotecan. SN-38 release mediated by α-rhamnosidase completes within 2 h, with a kcat/Km value approximately 5.0 × 104-fold higher than that of irinotecan. The 50% inhibition concentration (IC50) of Rham-SN-38 against three types of cancer cells and one normal cell exceeds 4.5 × 103 nM. The addition of α-rhamnosidase significantly increases cytotoxicity, with IC50 comparable to free SN-38. The QIC50, an index reflecting the difference in cytotoxicity with and without α-rhamnosidase, exceeds approximately 1.0 × 102-fold. Rham-SN-38, synthesized in this study, demonstrates significant potential as a prodrug for cancer therapy.

Engineered macrophages acting as a trigger to induce inflammation only in tumor tissues based on arginase 1-responsive TNF-α accelerated release.

Herein, we report engineered macrophages, termed "MacTrigger," acting as a trigger to induce an inflammatory environment only in tumor tissues. This led to intensive anti-tumor effects based on the removal potential of foreign substances. The strength of this study is the utilization of two unique functions of macrophages: (1) their ability to migrate to tumor tissues and (2) polarization into the anti-inflammatory M2 phenotype in the presence of tumor tissues. The MacTrigger accelerated the release of inflammatory cytokines, tumor necrosis factor-alpha (TNF-α), when it was polarized to the M2 phenotype. When the MacTrigger was administered to tumor-bearing mice, tumor growth was significantly inhibited compared with the non-treatment group, the un-transfected macrophages group, and the group with engineered macrophages capable of randomly releasing TNF-α. Additionally, the ratio of the M1 phenotype to the M2 phenotype in tumor tissues was >1 only in the MacTrigger group. Moreover, the ratios of natural killer cells and CD8+T cells in tumor tissues were increased compared with other groups. These results indicate that MacTrigger can induce inflammation in tumor tissues, leading to effective anti-tumor effects. In normal tissues, especially the liver, notable side effects were not observed. This is because, in the liver, the MacTrigger was not polarized to the M2 phenotype and could not induce inflammation. These results suggest that the MacTrigger is a "trigger" that can induce inflammation only in tumor tissues, then allowing the body to attack tumor tissues through the innate immunity system.

Engineered macrophages acting as a trigger to induce inflammation only in tumor tissues.

Herein, we report engineered macrophages, termed "MacTrigger," acting as a trigger to induce an inflammatory environment only in tumor tissues. This led to intensive anti-tumor effects based on the removal potential of foreign substances. The strength of this study is the utilization of two unique functions of macrophages: (1) their ability to migrate to tumor tissues and (2) polarization into the anti-inflammatory M2 phenotype in the presence of tumor tissues. The MacTrigger accelerated the release of inflammatory cytokines, tumor necrosis factor-alpha (TNF-α), when it was polarized to the M2 phenotype. When the MacTrigger was administered to tumor-bearing mice, tumor growth was significantly inhibited compared with the non-treatment group, the un-transfected macrophages group, and the group with engineered macrophages capable of randomly releasing TNF-α. Additionally, the ratio of the M1 phenotype to the M2 phenotype in tumor tissues was >1 only in the MacTrigger group. Moreover, the ratios of natural killer cells and CD8+T cells in tumor tissues were increased compared with other groups. These results indicate that MacTrigger can induce inflammation in tumor tissues, leading to effective anti-tumor effects. In normal tissues, especially the liver, notable side effects were not observed. This is because, in the liver, the MacTrigger was not polarized to the M2 phenotype and could not induce inflammation. These results suggest that the MacTrigger is a "trigger" that can induce inflammation only in tumor tissues, then allowing the body to attack tumor tissues through the innate immunity system.