Hiroyuki Tsuchiya

The tumor microenvironment (TME) provides a niche for immune evasion and immunotherapy resistance, in part, by recruiting pro‐tumor M2‐like macrophages. In the present study, using heterospheroids consisting of cancer cells and macrophages, we identified TAM activators, which are compounds that reprogram M2‐like tumor‐associated macrophages (TAMs) toward the antitumor M1‐like phenotype. THP‐1‐ or human peripheral monocyte‐derived macrophages were co‐cultured with liver cancer (LC) cells in an ultra‐low attachment dish to generate heterospheroids. Cell surface marker expression and macrophage infiltration into the heterospheroids were assessed by flow cytometry and fluorescence microscopy, respectively. Lipopolysaccharide (LPS) and interferon‐γ (IFNγ)‐induced M1 marker expression was observed on the macrophages in the homospheroids; however, this induction was suppressed in heterospheroids. Microscopic imaging revealed that macrophage infiltration into the heterospheroids was decreased in the presence of LPS and IFNγ, which prompted us to develop a high‐content imaging screen. We identified two compounds [alprostadil (prostaglandin E1) and HX531] with TAM‐activating activity. RNA‐seq analysis revealed that HX531 modulated the immune and IFN response in cancer cells and cell division in macrophages. Moreover, alprostadil promoted the M1‐like polarization of TAMs, increased tumor‐infiltrating CD8 ⁺ T cells, and enhanced anti‐PD‐1 antibody therapeutic efficacy in a syngeneic tumor‐bearing mouse. In conclusion, the heterospheroid culture recapitulates the immunosuppressive TME, which prevents the M1 polarization of TAMs. It provides a new platform for screening TAM activators and will enable the development of novel cancer immunotherapeutics when combined with high‐content imaging analysis.

M2-like tumor-associated macrophages (TAMs) are a promising target for cancer immunotherapy, particularly for cancer patients who are refractory to current immune checkpoint inhibitors (ICIs). Previously, we showed that prostaglandin E1 (PGE1) enhances the expression of M1 markers, including HLA-DR, on macrophages and induces the M1 polarization of TAMs in vivo. This study investigated the pharmacological mechanisms by which PGE1 and its derivatives suppress the expression of M2 markers, including TREM2 and CXCR2. Macrophages were cultured in ultralow attachment dishes either alone or in combination with liver cancer cell lines to generate homospheroids or heterospheroids. Cell surface marker expression was assessed by flow cytometry. Compared with homospheroids, M2 marker expression on macrophages in heterospheroids was significantly increased, suggesting that heterospheroid culture promotes M2 polarization. PGE1 decreased M2 marker expression in heterospheroids more effectively compared with PGE2, PGE3, misoprostol, and 13,14-dihydro-15-keto-PGE1, whereas the suppressive effects of 15-keto- and 13,14-dihydro-PGE1s, and lubiprostone were comparable to that of PGE1. Pharmacological inhibition of prostaglandin receptors revealed that EP2 and EP4 receptors are involved in the PGE1-induced reprogramming of M2-like macrophages to M1 macrophages. In summary, PGE1 and its derivatives are promising TAM-targeting immunotherapeutics.

The tumor microenvironment (TME) provides a niche for immune evasion and immunotherapy resistance, in part, by recruiting pro-tumor M2-like macrophages. In the present study, using heterospheroids consisting of cancer cells and macrophages, we identified TAM activators, which are compounds that reprogram M2-like tumor-associated macrophages (TAMs) toward the antitumor M1-like phenotype. THP-1- or human peripheral monocyte-derived macrophages were co-cultured with liver cancer cells in an ultra-low attachment dish to generate heterospheroids. Cell surface marker expression and macrophage infiltration into the heterospheroids were assessed by flow cytometry and fluorescence microscopy, respectively. Lipopolysaccharide (LPS) and interferon-γ (IFNγ)-induced M1 marker expression was observed on the macrophages in the homospheroids; however, this induction was suppressed in heterospheroids. Microscopic imaging revealed that macrophage infiltration into the heterospheroids was decreased in the presence of LPS and IFNγ, which prompted us to develop a high-content imaging screen. We identified two compounds [alprostadil (prostaglandin E1) and HX531] with TAM-activating activity. RNA-seq analysis revealed that HX531 modulated the immune and IFN response in cancer cells and cell division in macrophages. Moreover, alprostadil promoted the M1-like polarization of TAMs, increased tumor-infiltrating CD8+ T cells, and enhanced anti-PD-1 antibody therapeutic efficacy in a syngeneic mouse xenograft model. In conclusion, the heterospheroid culture recapitulates the immunosuppressive TME, which prevents the M1 polarization of TAMs. It provides a new platform for screening TAM activators and will enable the development of novel cancer immunotherapeutics when combined with high-content imaging analysis.

The limited efficacy of immune checkpoint inhibitors in hepatocellular carcinoma (HCC) can arise from the involvement of immunosuppressive cells, such as macrophages. In the present study, we found that the long noncoding RNA NEAT1, particularly its short isoform (NEAT1v1) induced the expression of CD24, which is known as an immune checkpoint molecule for macrophages. Mechanistically, NEAT1v1 sponged miR-320a-3p to upregulate the transcription factor SP1, which in turn, activated CD24 transcription. A spheroid co-culture of primary or THP-1-derived macrophages with HCC cells revealed that NEAT1v1 suppressed M1 marker expression and phagocytic activity in macrophages. In a syngeneic subcutaneous model of HCC, Neat1v1 increased the tumor infiltration of M2-like macrophages and induced resistance to anti-Pd-1 antibody, while combination of the anti-Pd-1 and anti-Cd24 antibodies significantly suppressed the tumor growth. Finally, NEAT1, SP1, and CD24 expression increased in tumor tissues from patients with HCC, compared to adjacent normal tissues, whereas miR-320a-3p was significantly downregulated. Moreover, plasma NEAT1 cell-free RNA was significantly decreased after therapeutic intervention. Taken together, NEAT1v1 protects HCC cells from macrophages by sending a "Don't Eat Me" signal via CD24, and is therefore, a potential target molecule for the treatment and diagnosis of HCC.

This study investigated the effects of a long noncoding RNA, nuclear paraspeckle assembly transcript 1 (NEAT1) variant 1 (NEAT1v1) on drug resistance in liver cancer cell lines. NEAT1 knockdown activated mitogen-activated protein kinase (MAPK) signaling pathways, including MAPK kinase (MEK)/extracellular signal-regulated kinase (ERK), but suppressed AKT. Moreover, NEAT1 knockdown sensitized liver cancer cells to sorafenib and lenvatinib, both clinically used for treating hepatocellular carcinoma, whereas it conferred resistance to an AKT-targeted drug, capivasertib. NEAT1v1 overexpression suppressed MEK/ERK and activated AKT, resulting in resistance to sorafenib and lenvatinib and sensitization to capivasertib. Superoxide dismutase 2 (SOD2) knockdown reverted the effects of NEAT1v1 overexpression on the sensitivity to the molecular-targeted drugs. Although NEAT1 or SOD2 knockdown enhanced endoplasmic reticulum (ER) stress, concomitant with the suppression of AKT, taurodeoxycholate, an ER stress suppressor, did not restore AKT activity. Although further in vivo and clinical studies are needed, these results suggested that NEAT1v1 switches the growth modality of liver cancer cell lines from MEK/ERK-dependent to AKT-dependent mode via SOD2 and regulates sensitivity to the molecular-targeted drugs independent of ER stress.

A long noncoding RNA, nuclear paraspeckle assembly transcript 1 (NEAT1) variant 1 (NEAT1v1), confers radioresistance to hepatocellular carcinoma (HCC) cells by inducing autophagy via γ-aminobutyric acid A receptor-associated protein (GABARAP). Radiation induces oxidative stress to damage cellular components and organelles, but it remains unclear how NEAT1v1 protects HCC cells from radiation-induced oxidative stress via autophagy. To address this, we precisely investigated NEAT1v1-induced autophagy in irradiated HCC cell lines. X-ray irradiation significantly increased cellular and mitochondrial oxidative stress and mitochondrial DNA content in HCC cells while NEAT1v1 suppressed them. NEAT1v1 concomitantly induced the phosphatase and tensin homolog-induced kinase 1 (PINK1)/parkin-mediated mitophagy. Interestingly, parkin expression was constitutively upregulated in NEAT1v1-overexpressing HCC cells, leading to increased mitochondrial parkin levels. Superoxide dismutase 2 (SOD2) was also upregulated by NEAT1v1, and GABARAP or SOD2 knockdown in NEAT1v1-overexpressing cells increased mitochondrial oxidative stress and mitochondrial DNA content after irradiation. Moreover, it was suggested that SOD2 was involved in NEAT1v1-induced parkin expression, and that GABARAP promoted parkin degradation via mitophagy. This study highlights the unprecedented roles of NEAT1v1 in connecting radioresistance and mitophagy in HCC.

The liver is a primary organ that stores body iron, and plays a central role in the regulation of iron homeostasis. Hepatic iron overload (HIO) is a prevalent feature among patients with chronic liver diseases (CLDs), including alcoholic/nonalcoholic liver diseases and hepatitis C. HIO is suggested to promote the progression toward hepatocellular carcinoma because of the pro-oxidant nature of iron. Iron metabolism is tightly regulated by various factors, such as hepcidin and ferroportin, in healthy individuals to protect the liver from such deteriorative effects. However, their intrinsic expressions or functions are frequently compromised in patients with HIO. Thus, various nutrients have been reported to regulate hepatic iron metabolism and protect the liver from iron-induced damage. These nutrients are beneficial in HIO-associated CLD treatment and eventually prevent iron-mediated hepatocarcinogenesis. This mini-review aimed to discuss the mechanisms and hepatocarcinogenic risk of HIO in patients with CLDs. Moreover, nutrients that hold the potential to prevent iron-induced hepatocarcinogenesis are summarized.

A long noncoding RNA (lncRNA), nuclear enriched abundant transcript 1 (NEAT1) variant 1 (NEAT1v1), is involved in the maintenance of cancer stem cells (CSCs) in hepatocellular carcinoma (HCC). CSCs are suggested to play important roles in therapeutic resistance. Therefore, we investigated whether NEAT1v1 is involved in the sensitivity to radiation therapy in HCC. Gene knockdown was performed using short hairpin RNAs, and NEAT1v1-overexpressing HCC cell lines were generated by stable transfection with a NEAT1v1-expressing plasmid DNA. Cells were irradiated using an X-ray generator. We found that NEAT1 knockdown enhanced the radiosensitivity of HCC cell lines and concomitantly inhibited autophagy. NEAT1v1 overexpression enhanced autophagy in the irradiated cells and conferred radioresistance. Gamma-aminobutyric acid receptor-associated protein (GABARAP) expression was downregulated by NEAT1 knockdown, whereas it was upregulated in NEAT1v1-overexpressing cells. Moreover, GABARAP was required for NEAT1v1-induced autophagy and radioresistance as its knockdown significantly inhibited autophagy and sensitized the cells to radiation. Since GABARAP is a crucial protein for the autophagosome-lysosome fusion, our results suggest that NEAT1v1 confers radioresistance to HCC by promoting autophagy through GABARAP.

This study aimed to present a rare case of fibrous dysplasia (FD) in a healthy young adult man with a concomitant osteoporotic vertebral compression fracture. FD is a benign lesion of the bone characterized by replacement of the medullary component with fibro-osseous tissue that contains abnormally arranged trabeculae of immature woven bone. Recently it has been reported that several bone tumors including FD express the receptor activator of nuclear factor-kappa B (RANK) and its ligand (RANKL). Therefore, we hypothesized that FD contributed to osteoporosis, linked by the RANK-RANKL pathway of osteoclastogenesis. We report the case of a healthy man with monostotic femoral fibrous dysplasia (FD) with concomitant 7^th thoracic vertebra compression fracture due to osteoporosis [young adult mean (YAM) was 79% in bone mineral density (BMD)]. After curettage of the FD, artificial bone grafting in the cavity, and administration of alendronate sodium, BMD improved considerably within 9 months. FD is a benign bone condition in which abnormal fibrous tissue replaces normal bone. The axis of the receptor activator of nuclear factor-kappa B (RANK) and its ligand (RANKL) has been implicated in osteoporosis pathogenesis. RANKL immunohistochemical staining was performed, and strong staining of stromal cells was observed compared to other FD cases that showed weak to moderate staining. The presence of FD might have contributed to the low BMD due to the RANK-RANKL axis acting as osteoclastogenesis stimulator.