In vivo optical imaging of tumor stromal cells with hypoxia-inducible factor activity.

Tumors contain various stromal cells, such as immune cells, endothelial cells, and fibroblasts, which contribute to the development of a tumor-specific microenvironment characterized by hypoxia and inflammation, and are associated with malignant progression. In this study, we investigated the activity of intratumoral hypoxia-inducible factor (HIF), which functions as a master regulator of the cellular response to hypoxia and inflammation. We constructed the HIF activity-monitoring reporter gene hypoxia-response element-Venus-Akaluc (HVA) that expresses the green fluorescent protein Venus and modified firefly luciferase Akaluc in a HIF activity-dependent manner, and created transgenic mice harboring HVA transgene (HVA-Tg). In HVA-Tg, HIF-active cells can be visualized using AkaBLI, an ultra-sensitive in vivo bioluminescence imaging technology that produces an intense near-infrared light upon reaction of Akaluc with the D-luciferin analog AkaLumine-HCl. By orthotopic transplantation of E0771, a mouse triple negative breast cancer cell line without a reporter gene, into HVA-Tg, we succeeded in noninvasively monitoring bioluminescence signals from HIF-active stromal cells as early as 8 days after transplantation. The HIF-active stromal cells initially clustered locally and then spread throughout the tumors with growth. Immunohistochemistry and flow cytometry analyses revealed that CD11b+ F4/80+ macrophages were the predominant HIF-active stromal cells in E0771 tumors. These results indicate that HVA-Tg is a useful tool for spatiotemporal analysis of HIF-active tumor stromal cells, facilitating investigation of the roles of HIF-active tumor stromal cells in tumor growth and malignant progression.

Tissue-resident macrophages are major tumor-associated macrophage resources, contributing to early TNBC development, recurrence, and metastases.

Triple-negative breast cancer (TNBC) is an aggressive and highly heterogenous disease with no well-defined therapeutic targets. Treatment options are thus limited and mortality is significantly higher compared with other breast cancer subtypes. Mammary gland tissue-resident macrophages (MGTRMs) are found to be the most abundant stromal cells in early TNBC before angiogenesis. We therefore aimed to explore novel therapeutic approaches for TNBC by focusing on MGTRMs. Local depletion of MGTRMs in mammary gland fat pads the day before TNBC cell transplantation significantly reduced tumor growth and tumor-associated macrophage (TAM) infiltration in mice. Furthermore, local depletion of MGTRMs at the site of TNBC resection markedly reduced recurrence and distant metastases, and improved chemotherapy outcomes. This study demonstrates that MGTRMs are a major TAM resource and play pivotal roles in the growth and malignant progression of TNBC. The results highlight a possible novel anti-cancer approach targeting tissue-resident macrophages.

Double filtration plasmapheresis: Review of current clinical applications.

Double filtration plasmapheresis (DFPP) is a semi-selective blood purification modality derived from the plasma exchange (PE) modality. In the DFPP treatment, two types of filters with different pore sizes are used: a plasma separator and a plasma component separator. Blood is separated into plasma and blood cells using a plasma separator. The separated plasma is fractionated into large and small molecular weight components by a plasma component separator. Large molecular weight components, including pathogenic substances, are discarded. Small molecular weight components, including valuable substances such as albumin, are returned to the patient. The advantage of DFPP is that the volume of replacement fluid can be significantly reduced compared to PE. By selecting the optimal pore size model for the plasma component separator, DFPP can be applied to various disorders. The clinical applications of DFPP are reviewed based on recent articles on metabolic disorders, organ transplants, rheumatic disorders, neurological disorders, and dermatologic disorders.

Plasma separation using a membrane.

Plasma separation using a membrane is clinically used as plasmapheresis therapy, such as plasma exchange (PE), double-filtration plasmapheresis (DFPP), or plasma adsorption (PA) modalities. Plasma separation is performed either by centrifugation or by filtration, which involves a permeable hollow fiber membrane. A plasma separator with a hollow fiber membrane was first developed in Japan in the 1980s. It has been used for more than 30 years with continuous technical modifications. Treatment with a membrane-type plasma separator is a safe and well-established modality for many drug-resistant and/or refractory diseases. Currently, national health insurance covers plasmapheresis for ∼30 diseases in Japan. Membrane-type plasma separators are used not only in Japan but also in many other countries. Plasmapheresis treatments with a membrane-type plasma separator are an important alternative for patients with drug-resistant and/or refractory diseases at present and in the near future.

Immunoadsorption using Immusorba TR and PH.

Immusorba TR (IM-TR) and PH (IM-PH) were developed as immunoadsorbents from nonbiological materials as affinity ligands for removal of pathogenic substances. The immunoadsorbents in IM-TR and IM-PH are immobilized on a polyvinyl alcohol gel with tryptophan and phenylalanine, respectively, as a ligand. IM-TR is mainly clinically applied to autoimmune neurological diseases such as myasthenia gravis, Guillain-Barré syndrome, and multiple sclerosis. IM-PH is also applied to neurological diseases but mainly to rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus. Many autoantibodies with different specificities have been found to have similar affinity for the ligand of Immusorba, and it is expected that Immusorba will be used against more diseases and help to elucidate the pathogenesis of diseases via identification of unknown pathogenic substances adsorbed to Immusorba.