MK615 inhibits pancreatic cancer cell growth by dual inhibition of Aurora A and B kinases

A Review with Updated Perspectives on Nutritional and Therapeutic Benefits of Apricot and the Industrial Application of Its Underutilized Parts

Fruits maintain the image as the richest sources of vitamins. Focusing on apricots, utilization of apricot species for many applications is possible due to its various benefits. Many research studies demonstrated different perspectives of apricot, especially in medical used as it can act as antioxidant, anti-inflammatory, and antimicrobial agents. Moreover, in the industrial sectors, apricots can be used in the production of biofuels and batteries. All components of the apricot fruit, including seeds and kernels have been found to possess significant interest. This review is to breach the knowledge gap regarding the key nutrients and chemicals of apricot fruit, contributing to its health-promoting properties to emphasize the noble importance of this fruit in the diet and in the management of several diseases. We also cover the application of apricots in the industry that could be developed as a promising and sustainable source.

Comprehensive Review of Phytochemical Constituents, Pharmacological Properties, and Clinical Applications of Prunus mume

Prunus mume is one of the most ancient medicinal herbs and health foods commonly used in Asian countries. It is widely used as a constituent of many medicinal preparations and as a food ingredient for its beneficial health effects. In this review, we retrieved reports from PubMed, embase, Scopus, and SciFinder databases, to collect extensive scientific evidence on the phytochemical constituents, pharmacological properties, and clinical applications of Prunus mume. The literature review revealed that approximately 192 compounds have been isolated from different parts of the plant, and their molecular structures have been identified. The pharmacological properties of the plant, including anti-diabetic, liver-protective, antitumor, antimicrobial, antioxidant, and anti-inflammatory activities, as well as their underlying mechanisms, have been clarified by in vitro and in vivo studies. Clinical studies, although very limited, have been highlighted in this review to provide a reference for further exploration on therapeutic applications of the plant.

Anticancer properties of Prunus mume extracts (Chinese plum, Japanese apricot)

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts of the fruit of Prunus mume (Rosaceae) have been used for a long time in Eastern Asia, in many culinary and medicinal preparations. The plant originates from the south of mainland China (named méi) and was introduced later in Japan (ume), Korea (maesil) and Vietnam (mai or mo). Extracts of the fruits (Chinese plum or Japanese apricot, 'Nanko' mume cultivar of Prunus mume Sieb. et Zucc.) are used in traditional Chinese and Japanese medicine, and various Korean medical preparations, for more than 2000 years. The medicinal use of the flesh of the fruits is cited in ancient Japanese monographies (such as Shokokukodenhiho published in 1817).

AIM OF THE STUDY

To analyze the anticancer activities of P. mume extracts and their potential use to prevent or treat cancers. The use of P. mume extracts to alleviate the side effects of chemotherapy, notably drug-induced gastro-intestinal toxicities, is also reviewed.

METHODS

Extensive database retrieval, such as SciFinder and PubMed, was performed by using keywords such as "Prunus mume", "Chinese plum", "Japanese apricot", and "cancer". In addition, relevant textbooks, patents, reviews, and digital documents (in English) were consulted to collate all available scientific literature and to provide a complete science-based survey of the topic.

RESULTS

P. mume extracts display hepatoprotective, anti-inflammatory, antioxidative and antibacterial effects, as well as anticancer properties. A survey of the antitumor activities of MK615 and other P. mume extracts is provided here, with information about the natural products found in the extracts (such as ursolic acid and oleanic acid) and the mechanisms of action of these extracts. MK615 inhibits proliferation and induces apoptotic death of different types of cancer cells from both solid and hematological tumors.

CONCLUSION

The pool of in vitro data and signs of anticancer activities in mice models and in Human, although very limited, support the use of this extract to treat cancer, notably gastro-intestinal tumors. However, more robust evidence of anticancer activity in Human are awaited. Beyond cancer treatment, the use of P. mume extracts to prevent or to treat mucositis and other gastro-intestinal damages induced by anticancer drugs is underlined. The woody plant Prunus mume, a member of the Rosaceae family, has a long plantation history in China, and has widely been planted in Asia due to its high ornamental value (colorful corollas, pleasant fragrance, weeping trait) and the culinary, nutritional and medicinal potential of the fruits from the specie Prunus mume Sieb. et Zucc (Mei). Over the past 20 years the therapeutic potential of the extract of Japanese apricot "Ume" has been regularly reported. Anti-bacterial, anti-oxidative, anti-inflammatory and anti-cancer properties have been described. A complete analysis of the published scientific literature on Ume and cancer is presented here.

Natural Products and Synthetic Analogs as a Source of Antitumor Drugs

Cancer is a heterogeneous disease and one of the major issues of health concern, especially for the public health system globally. Nature is a source of anticancer drugs with abundant pool of diverse chemicals and pharmacologically active compounds. In recent decade, some natural products and synthetic analogs have been investigated for the cancer treatment. This article presents the utilization of natural products as a source of antitumor drugs.

In Vivo Antitumor Effects of MK615 Led by PD-L1 Downregulation

Background/Aim: MK615 extracted from Prunus mume was reported to have anti-inflammatory effects. In this article, we examined the in vivo antitumor effect of MK615 (an extract from Japanese apricot) using mouse tumor xenografts and focusing on the downregulation of PD-L1 (programmed death-ligand 1), a ligand of programmed cell death-1, a surface protein of activated T cells. Materials and Methods: B16/BL6 melanoma cells were injected into C57BL/6 or BALB/c-nu/nu mice to establish lung metastasis. BALB/c-nu/nu mice (nude mice) were used as a T cell–deficient model. The mice were given MK615 or saline orally every other day for approximately 8 weeks, and their survival was observed. NF-κB (nuclear factor-κB) and PD-L1 expressions of metastatic lung tissues were also examined. Results: The survival rate was improved only in the MK615-treated C57BL/6 mice (P < .05), not in the saline-given control mice or BALB/c-nu/nu mice. The downregulations of NF-κB and PD-L1 were observed in both MK615-treated C57BL/6 and BALB/c-nu/nu mice. These results suggest that the antitumor effects of MK615 are associated with T cell–mediated immunity activated by MK-615-induced PD-L1 downregulation in tumor cells. Conclusion: MK615 is beneficial for a prolonged host survival time in the B16/BL6 melanoma xenograft model associated with T cell–mediated antitumor immunity.

A natural therapeutic approach for the treatment of periodontitis by MK615

Periodontitis is a chronic inflammatory disease that affects the tooth-supporting tissues. Gingival fibroblasts are the most abundant cells in periodontal tissues and they participate actively in the host inflammatory response to periodontal pathogens that is known to mediate local tissue destruction in periodontitis. The Japanese apricot, known as Ume in Japanese, has been a traditional Japanese medicine for centuries and is a familiar and commonly consumed food. The health benefits of Ume are widely recognized and have been confirmed in recent studies showing that MK615, an extract of compounds from Ume, has strong anticancer and anti-inflammatory effects. However, the potential role of MK615 in oral health is unknown. We hypothesized that the anti-inflammatory activities of MK615 could be exploited to inhibit the effects of lipopolysaccharide (LPS) produced by periodontal bacterial pathogens, such as Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis. Here, we show that LPS-induced interleukin (IL)-6 and IL-8 production by gingival fibroblasts was dose-dependently inhibited by MK615. As a potent inhibitor of the inflammatory responses induced by periodontal pathogens, MK615 merits further testing as a therapeutic agent in inflammatory diseases such as periodontitis.

Breaking up is hard to do: RalA, mitochondrial fission and cancer

The small GTPases RalA and RalB are activated downstream of oncogenic Ras. While activation of RalA is critically important for tumor initiation and growth of Ras-driven cancers, the highly similar small GTPase RalB is implicated in cell survival and metastasis. This difference in function between these two related proteins maps to the C-terminus, a 30 amino acid region that regulates subcellular localization and contains several potential phosphorylation sites. Here we discuss our recent evidence that phosphorylation by the mitotic kinase Aurora A promotes RalA relocalization to mitochondrial membranes, where it recruits the effector RalBP1 and the large dynamin-related GTPase Drp1 to promote mitochondrial fission. As upregulation of both RalA and Aurora A have been observed in human tumors, and phosphorylation of RalA at the site targeted by Aurora A promotes tumorigenesis, it is possible that regulation of mitochondrial fission is one mechanism by which RalA promotes cancer.

Advanced hepatocellular carcinoma responds to MK615, a compound extract from the Japanese apricot “Prunus mume”

MK615, a compound extracted from the Japanese apricot “Prunus mume” has been reported to have in vitro anti-tumor activities against several cancer cell lines, including hepatocellular carcinoma (HCC). However, the clinical effects and feasibility of administering MK615 for patients with HCC were unknown. We experienced a case with advanced HCC for which MK615 was effective against both lymph node and pulmonary metastases. A 60-year-old female underwent surgical resection of a 9 cm HCC in the right lobe. The pathological diagnosis was moderately differentiated HCC with vascular invasion. The HCC recurred in the liver 8 mo after the surgery. Radiofrequency ablation and transarterial infusion chemotherapy were performed, but the recurrence was not controlled. One year after the intrahepatic recurrence, pulmonary and lymph metastasis appeared. Sorafenib was administered, but was not effective. Then, MK615 was administered as a final alternative therapy after informed consent was obtained from the patient. Three months later, her alpha-fetoprotein level decrease and both the lymph node and pulmonary metastases decreased in size. The patient has survived for more than 17 mo after the MK615 administration, and was in good condition. Although further investigations are necessary to clarify its safety and efficacy in humans, MK615 may be useful for the treatment of HCC, without serious adverse effects.

Efficacy of MK615 for the treatment of patients with liver disorders

AIM: To investigate the hepatoprotective effect of MK615, a Japanese apricot extract, in an animal model, and its clinical therapeutic effect.

METHODS: Wistar rats were administered physiological saline (4 mL/kg) or MK615 solution (4 mL/kg) for 7 d. On the sixth d, acute hepatic injury was induced by administering a single intraperitoneal injection (ip) of D-galactosamine hydrochloride (D-GalN) (600 mg/kg). Plasma levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined, and liver tissues were used for histopathological analysis. Fifty-eight patients with liver disorders [hepatitis C (n = 40), non-alcoholic fatty liver disease (n = 15), and autoimmune liver disease (n = 3)] were orally administered commercially available Misatol ME-containing MK615 (13 g/d) daily for 12 wk. Blood and urine were sampled immediately before and 6 wk, 12 wk, and 16 wk after the start of intake to measure various biochemical parameters. The percentage change in ALT and AST levels after 12 wk from the pre-intake baseline served as a primary endpoint.

RESULTS: D-GalN effectively induced acute hepatic injury in the rats. At 48 h after the ip injection of D-GalN, the plasma levels of ALT (475.6 ± 191.5 IU/L vs 225.3 ± 194.2 IU/L, P < 0.05) and AST (1253.9 ± 223.4 IU/L vs 621.9 ± 478.2 IU/L, P < 0.05) in the MK615 group were significantly lower than the control group. Scattered single cell necrosis, loss of hepatocytes, and extensive inflammatory cell infiltration were observed in hepatic tissue samples collected from the control group. However, these findings were less pronounced in the group receiving MK615. At the end of the clinical study, serum ALT and AST levels were significantly decreased compared with pre-intake baseline levels from 103.5 ± 58.8 IU/L to 71.8 ± 39.3 IU/L (P < 0.05) and from 93.5 ± 55.6 IU/L to 65.5 ± 34.8 IU/L (P < 0.05), respectively. A reduction of ≥ 30% from the pre-study baseline ALT level was observed in 26 (45%) of the 58 patients, while 25 (43%) patients exhibited similar AST level reductions. The chronic hepatitis C group exhibited significant ALT and AST level reductions from 93.4 ± 51.1 IU/L to 64.6 ± 35.1 IU/L (P < 0.05) and from 94.2 ± 55.5 IU/L to 67.2 ± 35.6 IU/L (P < 0.05), respectively. A reduction of ≥ 30% from the pre-study baseline ALT level was observed in 20 (50%) of the 40 patients. ALT levels in both the combined ursodeoxycholic acid (UDCA) treatment and the UDCA uncombined groups were significantly lower after Misatol ME administration. MK615 protected hepatocytes from D-GalN-induced cytotoxicity in rats. Misatol ME decreased elevated ALT and AST levels in patients with liver disorders.

CONCLUSION: These results suggest that MK615 and Misatol ME are promising hepatoprotective agents for patients with liver disorders.

Analysis of hepcidin expression: In situ hybridization and quantitative polymerase chain reaction from paraffin sections

AIM: To establish methods for quantitative polymerase chain reaction (PCR) for hepcidin using RNAs isolated from paraffin-embedded sections and in situ hybridization of hepatocellular carcinoma (HCC).

METHODS: Total RNA from paraffin-embedded sections was isolated from 68 paraffin-embedded samples of HCC. Samples came from 54 male and 14 female patients with a mean age of 66.8 ± 7.8 years. Quantitative PCR was performed. Immunohistochemistry and in situ hybridization for hepcidin were also performed.

RESULTS: Quantitative PCR for hepcidin using RNAs isolated from paraffin-embedded sections of HCC was performed successfully. The expression level of hepcidin mRNA in cancer tissues was significantly higher than that in non-cancer tissues. A method of in situ hybridization for hepcidin was established successfully, and this demonstrated that hepcidin mRNA was expressed in non-cancerous tissue but absent in cancerous tissue.

CONCLUSION: We have established novel methods for quantitative PCR for hepcidin using RNAs isolated from paraffin-embedded sections and in situ hybridization of HCC.

MK615, a Prunus mume Steb. Et Zucc ('Ume') extract, attenuates the growth of A375 melanoma cells by inhibiting the ERK1/2-Id-1 pathway

The Japanese apricot, a commonly consumed food called 'Ume' in Japan, has been used for a traditional Japanese medicine for centuries. MK615, an extract of compounds from 'Ume', has strong antitumorigenic and antiinflammatory effects including the induction of apoptosis and autophagy, and inhibition of cytokine production mediated via the inhibition of MAPKs signaling including ERK-1/2, JNK and p38MAPK. The inhibitor of DNA binding 1 (Id-1), a basic helix-loop-helix (bHLH) transcription factor family, is essential for DNA binding and the transcriptional regulation of various proteins that play important roles in the development, progression and invasion of tumors. In melanoma, Id-1 is constitutively expressed in the late and early stages, suggesting it as a therapeutic target in patients with melanoma. This study reports that MK615 profoundly reduced both the mRNA- and protein expression levels of Id-1 and inhibited cell growth in A375 melanoma cells. MK615 markedly inhibited the phosphorylation of ERK1/2, which is associated with Id-1 protein expression in A375 cells. Id-1-specific RNAi induced the death of A375 cells. Moreover, the expression of Bcl-2 was decreased by both MK615 and Id-1-specific RNAi in A375 cells. The results suggest that MK615 is a potential therapeutic agent for treating malignant melanoma.

MK615: a new therapeutic approach for the treatment of oral disease

The oral cavity is inhabited by over 500 different bacterial species. Dental caries and periodontitis are major bacterial infectious diseases in the oral cavity. Prunus mume Sieb. et Zucc., which is a variety of Japanese apricot known as Ume in Japanese, has been a traditional Japanese medicine for centuries, and is a familiar and commonly consumed food. The health benefits of Ume are now being widely recognized. Recent studies showed that MK615, an extract of compounds from Ume, has strong anticancer and anti-inflammatory effects. However, the potential role of MK615 in the antimicrobial field remains unknown. Therefore, we hypothesize that MK615 has antimicrobial activities against a range of oral bacterial pathogens. Here, we show that MK615 may be a potent inhibitor of the growth of some oral bacteria and an inhibitor of biofilm formation by Streptococcus mutans, the principal etiological agent of human dental caries. Our findings suggest that MK615 has potential as a therapeutic agent for treating and preventing oral diseases such as dental caries and periodontitis.

MK615 decreases RAGE expression and inhibits TAGE-induced proliferation in hepatocellular carcinoma cells

AIM: To investigate the proliferative effect of advanced glycation end-products (AGEs) and the role of their cellular receptor (RAGE) on hepatocellular carcinoma (HCC) cells, and the inhibitory effects of MK615, an extract from Japanese apricot, against AGEs were also evaluated.

METHODS: Two HCC cell lines, HuH7 and HepG2, were used. Expression of RAGE was investigated by polymerase chain reaction, Western blotting, and flow cytemetry (FACS). The effect of MK615 on RAGE expression was also evaluated by FACS. The proliferative effects of a control (unglycated bovine serum albumin), glucose-derived AGEs (Glc-AGE), and glyceraldehyde-derived AGEs (Glycer-AGE), and the anti-proliferative effect of MK615 against AGEs, were evaluated using MTT assays.

RESULTS: Expression of RAGE was confirmed at both the mRNA and protein levels in both HuH7 and HepG2. FACS revealed that the level of RAGE expression was higher in HuH7 than in HepG2. Treatment with 0.1 μg/mL MK615 decreased the expression level of RAGE from 24.3% to 3.7% in HuH7 and from 6.2% to 4.8% in HepG2. The growth indices for the control, Glc-AGE, and Glycer-AGE were 1.06 ± 0.08, 0.99 ± 0.04, and 1.38 ± 0.05, respectively, in HuH7 (P = 0.037), and were 1.03 ± 0.04, 1.04 ± 0.03, and 1.07 ± 0.05, respectively, in HepG2 (P > 0.05). When the cells were cultured simultaneously with Glycer-AGE and MK615, MK615 abrogated the proliferative effect of Glycer-AGE in HuH7.

CONCLUSION: Only Glycer-AGE has a proliferative effect on HuH7, which expresses a higher level of RAGE. MK615 suppresses the proliferative effect of Glycer-AGE on HuH7 by decreasing the expression of RAGE.

MK615, a prospective anti-proliferative agent, enhances CD4/CD8 ratio after exposure to irradiation

PURPOSE

Recently, it was found that MK615 possessed an anti-proliferative ability on treated cancer cells as a consequence of triterpenoid compounds. It is well known that radiation affects cellular-mediated immunity in cancer patients who are treated with radiotherapy. Similarly, the ability of triterpenoid compounds to enhance the cellular-mediated immunity has been observed. Therefore, in the present study, we attempted to investigate the effect of MK615 on both cancer cells and cellular-mediated immunity after irradiation.

MATERIALS AND METHODS

After mice were inoculated with mouse mammary carcinoma (FM3A) cells, they were categorised as follows: Non-treated, irradiated with 5 Gy, treated with 660 μg/day MK615 (MK615, an extract from the Japanese apricot) and lastly exposed to both irradiation and MK615. Afterward, mice were sacrificed and spleens were utilised to measure the cluster of differentiation 4 and 8 (CD4 and CD8) using flowcytometry. Simultaneously, in vitro study, human alveolar basal epithelial carcinomic (A549), mouse lymphoma (EL4) and FM3A cell lines were examined. Growth inhibition was assessed via colony, cell viability and apoptotic assays.

RESULTS

The median survival was in favour of the MK615-treated group (26.1 ± 1.9 days) compared with non-treated group (22.3 ± 2.3 days) (p < 0.05). Approximately 50% reduction of the CD4/CD8 ratio was observed following the exposure to irradiation alone. However, this ratio was comparable between the non-treated and both MK615-treated groups. Additionally, only the dual treatment was associated with tumour volume reduction. In contrast, in vitro study showed that MK615 had no significant (p ≥ 0.1) effect on the selected cell lines with or without irradiation.

CONCLUSION

MK615 has a potential to reduce tumour volume and may normalise cellular-mediated immunity level following the exposure to irradiation.

Advanced malignant melanoma responds to Prunus mume Sieb. Et Zucc (Ume) extract: Case report and in vitro study

Malignant melanoma (MM) is an aggressive chemoresistant skin cancer characterized by rapid metastasis and a poor prognosis. Therefore, the development of innovative effective therapies is critical. MK615 is an extract from the Japanese apricot Prunus mume Sieb. Et Zucc (Ume). At a neutral pH, it contains natural chemical substances such as triterpenoids that exert anti-neoplastic effects in several types of cancers. We found that in patients with advanced MM, MK615 dramatically suppressed the cutaneous in-transit metastasis of the disease. Pre- and post-treatment comparison of tumors showed that the apoptotic index was significantly increased by MK615. In vitro studies, MTT assay, flow cytometric cell cycle analysis and immunofluorescence microscopy revealed that MK615 inhibited the growth of SK-MEL28 cells in a dose-dependent manner, increased the proportion of cells in sub-G1 phase and induced apoptosis. We further examined the expression of the receptor for advanced glycation end products (RAGE). RAGE is a multi-ligand receptor that binds to a novel cytokine, high mobility group box protein 1 (HMGB1), as well as advanced glycation end products. There is evidence that RAGE/HMGB1 interactions enhance cell invasion in MM. Here, we present Western blotting and immunofluorescence microscopy data indicating that MK615 inhibited the expression of RAGE in SK-MEL28 cells, and suppressed the release of HMGB1 by SK-MEL28 cells. Our findings suggest that MK615 may be a valuable tool for treating MM and other malignant tumors.

Aurora-A phosphorylates, activates, and relocalizes the small GTPase RalA

The small GTPase Ras, which transmits extracellular signals to the cell, and the kinase Aurora-A, which promotes proper mitosis, can both be inappropriately activated in human tumors. Here, we show that Aurora-A in conjunction with oncogenic Ras enhances transformed cell growth. Furthermore, such transformation and in some cases also tumorigenesis depend upon S194 of RalA, a known Aurora-A phosphorylation site. Aurora-A promotes not only RalA activation but also translocation from the plasma membrane and activation of the effector protein RalBP1. Taken together, these data suggest that Aurora-A may converge upon oncogenic Ras signaling through RalA.

MK615 attenuates Porphyromonas gingivalis lipopolysaccharide-induced pro-inflammatory cytokine release via MAPK inactivation in murine macrophage-like RAW264.7 cells

The Japanese apricot, known as Ume in Japanese, has been a traditional Japanese medicine for centuries, and is a familiar and commonly consumed food. The health benefits of Ume are now being widely recognized and have been strengthened by recent studies showing that MK615, an extract of compounds from Ume, has strong anticancer and anti-inflammatory effects. However, the potential role of MK615 in the periodontal field remains unknown. Here, we found that MK615 significantly reduced the production of pro-inflammatory mediators (tumor necrosis factor-alpha and interleukin-6) induced by Porphyromonas gingivalis lipopolysaccharide (LPS), a major etiological agent in localized chronic periodontitis, in murine macrophage-like RAW264.7 cells. MK615 markedly inhibited the phosphorylation of ERK1/2, p38MAPK, and JNK, which is associated with pro-inflammatory mediator release pathways. Moreover, MK615 completely blocked LPS-triggered NF-kappaB activation. The present results suggest that MK615 has potential as a therapeutic agent for treating inflammatory diseases such as periodontitis.

Triterpenes augment the inhibitory effects of anticancer drugs on growth of human esophageal carcinoma cells in vitro and suppress experimental metastasis in vivo

The antineoplastic effects of combinations of anticancer drugs (5-fluorouracil, irinotecan and cisplatin) and triterpenes (ursolic acid, betulinic acid, oleanolic acid and a Japanese apricot extract (JAE) containing triterpenes) on esophageal squamous carcinoma cells were examined by the WST-8 (2-(2-methoxy- 4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt) assay in vitro and by an animal model in vivo. Triterpenes and JAE showed additive and synergistic cytotoxic effects, respectively, on esophageal squamous carcinoma cells (YES-2 cells) by combinational use of 5-fluorouracil. JAE and 5-fluorouracil induced cell cycle arrest at G2/M phase and at S phase, respectively, and caused apoptosis in YES-2 cells. A new animal model of esophageal cancer causing tumor colonization of the peritoneal cavity and producing bloody ascites was made by injecting YES-2 cells into the peritoneal cavity of a severe combined immunodeficiency mouse. In this model, 5-fluorouracil inhibited colonization of tumor cells in the peritoneum. The addition of JAE to 5-fluorouracil augmented the suppression of experimental metastasis of the peritoneum. The numbers of peritoneal nodules of more than 2 mm in diameter in mice treated with 5-fluorouracil and JAE were less than those in mice treated with 5-fluorouracil alone or JAE alone. These results suggest that triterpenes, especially JAE, are effective supplements for enhancing the chemotherapeutic effect of 5-fluorouracil on esophageal cancer.