Takahiro Matsumoto

Salvia miltiorrhiza is a traditional medicinal plant widely used to treat cardiovascular and cerebrovascular diseases. Tanshinones, including cryptotanshinone, a major bioactive constituent, exhibit various pharmacological activities. Therefore, methods for efficiently increasing tanshinone production are urgently needed. Recently, plant endophytes have attracted considerable attention as novel elicitors that promote the production of valuable bioactive compounds. In the present study, we investigated the effects of secondary metabolites produced by endophytes on the biosynthesis and accumulation of tanshinones in S. miltiorrhiza. Pseudomonas chlororaphis KPUPH-SMC was identified as an endophyte capable of promoting tanshinone production, and phenazine-1-carboxylic acid (PCA) was identified as the metabolite responsible for this activity. Our transcriptome analysis further demonstrated that PCA significantly upregulated the gene expression of tanshinone biosynthetic enzymes (GGPS, CPS, and KSL1). These findings suggest that endophyte-derived secondary metabolites can be used to enhance the biosynthesis of valuable compounds in medicinal plants. This approach represents a promising strategy to improve the quality of herbal medicines. Graphical abstract

Heat shock proteins (HSPs) play an important role in several tumors; contribute to anti-cancer drug resistance, cell proliferation, and metastasis; and have been suggested as a major cause of failed anti-cancer drug treatment. In addition, cancer stem cells (CSCs) have been identified in many types of malignancies, including leukemia, breast, colorectal, and brain cancers, and are a leading cause of failed cancer treatment owing to their anti-cancer drug and radiation therapy resistance. Therefore, many researchers, including our group, have investigated and developed natural products that target chemotherapy resistance factors in cancer cells. This review introduces the inhibitors of chemotherapy resistance factors discovered using a unique assay system. Graphical Abstract

The Wnt/β-catenin signaling pathway plays important roles in several cancer cells, including cell proliferation and development. We previously succeeded in synthesizing a small molecule compound inhibiting the Wnt/β-catenin signaling pathway, named LPD-01 (1), and 1 inhibited the growth of human colorectal cancer (HT-29) cells. In this study, we revealed that 1 inhibits the growth of HT-29 cells stronger than that of another human colorectal cancer (SW480) cells. Therefore, we have attempted to identify the target proteins of 1 in HT-29 cells. Firstly, we investigated the effect on the expression levels of the Wnt/β-catenin signaling pathway-related proteins. As a result, 1 inhibited the expression of target proteins of Wnt/β-catenin signaling pathway (c-Myc and Survivin) and their genes, whereas the amount of transcriptional co-activator (β-catenin) was not decreased, suggesting that 1 inhibited the Wnt/β-catenin signaling pathway without affecting β-catenin. Next, we investigated the target proteins of 1 using magnetic FG beads. Chemical pull-down assay combined with mass spectrometry suggested that 1 directly binds to importin7. As expected, 1 inhibited the nuclear translocation of importin7 cargoes such as Smad2 and Smad3 in TGF-β-stimulated HT-29 cells. In addition, the knockdown of importin7 by siRNA reduced the expression of target genes of Wnt/β-catenin signaling pathway. These results suggest that importin7 is one of the target proteins of 1 for inhibition of the Wnt/β-catenin signaling pathway. Graphical abstract

From the methanolic extract of the climbing stems and rhizomes of Sinomenium acutum, two new aporphine analogues, acutumalkaloids I and II, were isolated together with fifteen known compounds including lysicamine. The chemical structures of the isolated new compounds were elucidated based on chemical/physicochemical evidence such as NMR and MS spectra. For acutumalkaloids I and II, the absolute configurations were established by comparison of experimental and predicted electronic circular dichroism (ECD) data. We compared anti-proliferative activities of isolated compounds with reported naturally occurring Wnt/β-catenin pathway inhibitor, nuciferine. Among the isolated compounds, we found lysicamine have anti-proliferative activity against both of HT-29 human colon cancer cell line and its cancer stem cells (CSCs). The IC₅₀ values of lysicamine against non-CSCs and its CSCs were lower than that of nuciferine. In addition, the results of western blotting analysis suggested that lysicamine inhibited the expression of Wnt/β-catenin pathway target protein such as survivin. These results suggested that lysicamine show cytotoxic activity via inhibition of Wnt/β-catenin pathway. Graphical abstract

We isolated the new sesquiterpenes, valerianaterpenes IV and V, and the new lignans valerianalignans I–III from the methanol extracts of the rhizomes and roots of Valeriana fauriei and elucidated their structures based on chemical and spectroscopic findings. The absolute configuration of valerianaterpene IV and valerianalignans I–III were established by comparing experimental and predicted electronic circular dichroism (ECD) data. Among the isolated compounds, valerianalignans I and II exerted anti-proliferative activity against human astrocytoma cells (U-251 MG) and their cancer stem cells (U-251 MG CSCs). Interestingly, valerianalignans I and II notably exerted anti-proliferative activities at lower concentrations against CSCs than non-CSCs, and the absolute configurations of these compounds affected their activities.

Background: Heat shock proteins (Hsps) are overexpressed in several tumors and contribute to cell proliferation, metastasis, and anticancer drug resistance. Therefore, Hsp inhibitors have enhanced cytotoxicity as chemotherapeutic agents and may be effective with a reduced dosage for tumor therapy to avoid side effects. Results: Four new azaphilones, maximazaphilones I–IV (1–4), and three known compounds (5–7) have been isolated from the airborne-derived fungus Penicillium maximae. Inhibitory effects of isolated compounds against induction of Hsp105 were evaluated by the luciferase assay system using Hsp105 promoter. In this assay, 2–4, 6, and 7 significantly inhibited hsp105 promoter activity without cytotoxicity. In addition, all isolated compounds except for 5 significantly induced the death of Adriamycin (ADR)-treated HeLa cells. Interestingly, 1–4, 6, and 7 didn’t show anti-proliferative and cell death-inducing activity without ADR. Conclusion: This study revealed the chemical structures of maximazaphilones I–IV (1–4) and the potency of azaphilones may be useful for cancer treatment and reducing the dose of anticancer agents. In addition, one of the mechanisms of cell death-inducing activity for 2–4, 6, and 7 was suggested to be inhibitory effects of Hsp105 expression.

We isolated seven new iridoid glucosides (valerianairidoids I–VII; 1–3, 6, 7, 9, and 12) and six known compounds from the methanol extract of the dried rhizomes and roots of Valeriana fauriei. Chemical and spectroscopic data were used to elucidate the chemical structures of the seven new iridoid glucosides, and their absolute configurations were determined by comparing their electronic circular dichroism (ECD) spectra with those determined experimentally. Aglycones 1a, 6a, and 9a, which were obtained by enzymatic hydrolysis of the isolated iridoid glucosides, exhibited anti-proliferative activities against cancer stem cells (CSCs) established by a sphere-formation assay using human breast cancer (MDA-MB-231) and human astrocytoma (U-251MG) cells. Interestingly, these iridoids selectively showed anti-proliferative activities against CSCs from MDA-MB-231 cells. These results suggest that the iridoids obtained in this study may have potency as a breast cancer treatment and as preventive agent via exterminating CSCs.