Corrigendum: Targeting thymidylate synthase enhances the chemosensitivity of triple-negative breast cancer towards 5-FU-based combinatorial therapy.

[This corrects the article DOI: 10.3389/fonc.2021.656804.].

Pharmacological attenuation of melanoma by tryptanthrin pertains to the suppression of MITF-M through MEK/ERK signaling axis.

Melanoma is the most aggressive among all types of skin cancers. The current strategies against melanoma utilize BRAFV600E, as a focal point for targeted therapy. However, therapy resistance developed in melanoma patients against the conventional anti-melanoma drugs hinders the ultimate benefits of targeted therapies. A major mechanism by which melanoma cells attain therapy resistance is via the activation of microphthalmia-associated transcription factor-M (MITF-M), the key transcription factor and oncogene aiding the survival of melanoma cells. We demonstrate that tryptanthrin (Tpn), an indole quinazoline alkaloid, which we isolated and characterized from Wrightia tinctoria, exhibits remarkable anti-tumor activity towards human melanoma through the down-regulation of MITF-M. Microarray analysis of Tpn-treated melanoma cells followed by a STRING protein association network analysis revealed that differential expression of genes in melanoma converges at MITF-M. Furthermore, in vitro and in vivo studies conducted using melanoma cells with differential MITF-M expression status, endogenously or ectopically, demonstrated that the anti-melanoma activity of Tpn is decisively contingent on its efficacy in down-regulating MITF-M expression. Tpn potentiates the degradation of MITF-M via the modulation of MEK1/2-ERK1/2-MITF-M signaling cascades. Murine models demonstrate the efficacy of Tpn in attenuating the migration and metastasis of melanoma cells, while remaining pharmacologically safe. In addition, Tpn suppresses the expression of mutated BRAFV600E and inhibits Casein Kinase 2α, a pro-survival enzyme that regulates ERK1/2 homeostasis in many tumor types, including melanoma. Together, we point to a promising anti-melanoma drug in Tpn, by virtue of its attributes to impede melanoma invasion and metastasis by attenuating MITF-M.

Targeting Thymidylate Synthase Enhances the Chemosensitivity of Triple-Negative Breast Cancer Towards 5-FU-Based Combinatorial Therapy.

BACKGROUND: The ongoing treatment modalities for breast cancer (BC) primarily rely on the expression status of ER, PR and HER-2 receptors in BC tissues. Our strategy of chemosensitization provides new insights to counter chemoresistance, a major obstacle that limits the benefits of chemotherapy of mammary cancers. METHODS: By utilizing a murine breast cancer model employing NSG mice bearing orthotopic triple-negative breast cancer (TNBC) xenografts, we have evaluated the ability of phytochemical curcumin in chemosensitizing BC to 5-Fluorouracil (5-FU) chemotherapy and the differential modulations of cellular events in response to this strategy, independent of their receptor status. RESULTS: A significant synergistic antitumor potential was observed in the murine model with a sub-optimal dose treatment of 5-FU plus curcumin, as evaluated by a reduction in the tumor-related parameters. We authenticated the pivotal role of thymidylate synthase (TS) in regulating the 5-FU-curcumin synergism using the TNBC pre-clinical model. Our study also confirmed the pharmacological safety of this chemotherapeutic plus phytoactive combination using acute and chronic toxicity studies in Swiss albino mice. Subsequently, the molecular docking analysis of curcumin binding to TS demonstrated the affinity of curcumin towards the cofactor-binding site of TS, rather than the substrate-binding site, where 5-FU binds. Our concomitant in vivo and in silico evidence substantiates the superior therapeutic index of this combination. CONCLUSION: This is the first-ever pre-clinical study portraying TS as the critical target of combinatorial therapy for mammary carcinomas and therefore we recommend its clinical validation, especially in TNBC patients, who currently have limited therapeutic options.

Amelioration of Radiation-Induced Damages in Mice by Curcuminoids: The Role of Bioavailability.

PURPOSE: The present study investigated the role of free curcuminoids bioavailability on the relative radioprotective efficacy of natural unformulated curcuminoids. MATERIALS AND METHODS: A food-grade bioavailable formulation of curcuminoids as curcumagalactomannosides (CGM) and unformulated curcuminoids (UC) were employed for the study. Swiss albino mice were randomized into Normal control, Radiation control, Radiation + UC, and Radiation + CGM groups and irradiated with γ-radiation of 6, 8, 10 and 12 Gy. Survival rate, hematological and biochemical parameters, bone marrow cellularity, chromosomal aberrations and histopathology of intestine were followed as a measure of the relative efficacy.Results and Discussion: Oral administration with both UC and CGM at 100 mg/kg. b.wt. produced significant radioprotective effect over the untreated control group of animals. However, CGM treatment was found to provide better clastogenic and genotoxic potential as compared to UC. Further, the histopathology analysis of intestine confirmed the better protective effect of CGM over UC-treated animals. CONCLUSION: The present study demonstrated the positive role of the bioavailability of curcuminoids in the amelioration of radiation-induced damages in mice since CGM treatment exerted better survival rate and radioprotective effect as compared with UC, despite the relatively low concentrations of curcuminoids in CGM (39% w/w).

Protection against Whole Body γ-Irradiation Induced Oxidative Stress and Clastogenic Damage in Mice by Ginger Essential Oil.

Radioprotective effects of ginger essential oil (GEO) on mortality, body weight alteration, hematological parameters, antioxidant status and chromosomal damage were studied in irradiated mice. Regression analysis of survival data in mice exposed to radiation yielded LD50/30 as 7.12 and 10.14 Gy for control (irradiation alone) and experimental (GEO-treated irradiated) mice, respectively, with a dose reduction factor (DRF) of 1.42. In mice exposed to whole-body gamma-irradiation (6 Gy), GEO pre-treatment at 100 and 500 mg/kg b.wt (orally) significantly ameliorated decreased hematological and immunological parameters. Radiation induced reduction in intestinal tissue antioxidant enzyme levels such as superoxide dismutase, catalase, glutathione peroxidase and glutathione was also reversed following administration of GEO. Tissue architecture of small intestine which was damaged following irradiation was improved upon administration of GEO. Anticlastogenic effects of GEO were studied by micronuclei assay, chromosomal aberration and alkaline gel electrophoresis assay. GEO significantly decreased the formation of micronuclei, increased the P/N ratio, inhibited the formation of chromosomal aberrations and protected agaisnt cellular DNA damage in bone marrow cells as revealed by comet assay. These results are supportive of use of GEO as a potential radioprotective compound.

Enhanced bioavailability and safety of curcumagalactomannosides as a dietary ingredient.

In spite of the various bioavailable formulations of curcumin for pharma and dietary supplement applications, food grade formulations suitable as a dietary ingredient, and capable of providing significant levels of plasma curcumin, are limited. The present contribution describes the safety and oral bioavailability of a novel water soluble formulation of curcumin, curcumagalactomannosides (CGM), when used as a dietary ingredient in selected food items. CGM was prepared using a food grade hydrocolloid (galactomannans) derived from the kitchen spice fenugreek (Trigonella foenum graccum), without using any synthetic excipients. The safety of the formulation was assessed through acute and subchronic toxicity studies on Wistar rats and genotoxicity studies. The efficacy of CGM as a bioavailable dietary ingredient was assessed by successfully preparing various food items and by measuring the post-blood plasma curcumin levels at various time intervals after the consumption of food items. High performance liquid chromatography coupled with a photodiode array detector (HPLC-PDA) and electrospray ionization tandem mass spectrometer (ESI-MS/MS) was employed for the quantification of plasma curcuminoids. It was observed that CGM is safe and suitable for further development and clinical studies, with a no observable adverse effect level (NOAEL) up to 2.0 g kg⁻¹ per day b.wt. CGM was found to offer seven to ten times higher bioavailability of curcumin in humans, when incorporated into various food/beverage items at 100 mg CGM per serving size, as compared to the standard unformulated curcumin.

Gastroprotective activity of essential oils from turmeric and ginger.

BACKGROUND: Turmeric (Curcuma longa) and ginger (Zingiber officianale) are widely used in Asian countries as traditional medicine and food ingredients. In the present study, we have evaluated the gastroprotective activity of turmeric essential oil (TEO) and ginger essential oil (GEO) in rats. METHODS: Turmeric and ginger were evaluated for their antiulcer activity against ethanol-induced ulcers in male Wistar rats at different doses: 100, 500 and 1000 mg/kg body weight. Ethanol was used to induce gastric ulcer in Wistar rats. Parameters such as ulcer index, histopathology and levels of antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase and glutathione (GSH) levels were measured to assess the degree of protection produced by the essential oils. RESULTS: TEO and GEO inhibited ulcer by 84.7% and 85.1%, respectively, as seen from the ulcer index. Reduced antioxidant enzymes such as GPx, SOD, catalase and GSH produced by alcohol administration were significantly (p<0.001) increased by simultaneous administration of TEO and GEO. Histopathological examination showed that ethanol-induced lesions such as necrosis, erosion and hemorrhage of the stomach wall were significantly reduced after oral administration of essential oils. CONCLUSIONS: RESULTS suggest that TEO and GEO could reduce the gastric ulcer in rat stomach as seen from the ulcer index and histopathology of the stomach. Moreover, oxidative stress produced by ethanol was found to be significantly reduced by TEO and GEO.

Antimutagenic potential and modulation of carcinogen-metabolizing enzymes by ginger essential oil.

Essential oil extracted from ginger (GEO) was evaluated for its mutagenicity to Salmonella typhimurium TA 98, TA 100, TA 102, and TA 1535 strains with and without microsomal activation. GEO was found to be non-mutagenic up to a concentration of 3 mg/plate. It was also assessed for antimutagenic potential against direct acting mutagens such as sodium azide, 4-nitro-o-phenylenediamine, N-methyl-N'-nitro-N-nitrosoguanidine, tobacco extract, and 2-acetamidoflourene, which needs microsomal activation. GEO significantly inhibited (p < 0.001) the mutagenicity induced by these agents in a concentration-dependent manner. The effect of GEO to modulate the action of phase I carcinogen-metabolizing enzymes was investigated by studying its effect on various isoforms of microsomal cytochrome P450 enzymes. Significant inhibition of CYP1A1, CYP1A2, and CYP2B1/2, aniline hydroxylase (an indicator of CYP2E1 activity), and aminopyrine-N-demethylase (indicator of CYP1A, 2A, 2B, 2D, and 3A activity) was shown by GEO both in vitro and in vivo. GEO gave an IC50 value of 30, 57.5, and 40 µg for CYP1A1, CYP1A2, and CYP2B1/2, respectively, 55 µg for aniline hydroxylase, and 37.5 µg for aminopyrene-N-demethylase. GEO also significantly increased the levels of phase II carcinogen-metabolizing enzymes uridine 5'-diphospho-glucuronyl transferase and glutathione-S-transferase in vivo indicating the use of GEO as an antimutagen and as a potential chemopreventive agent.

Acute and subchronic toxicity as well as mutagenic evaluation of essential oil from turmeric (Curcuma longa L).

The present study investigated the acute, subchronic and genotoxicity of turmeric essential oil (TEO) from Curcuma longa L. Acute administration of TEO was done as single dose up to 5 g of TEO per kg body weight and subchronic toxicity study for thirteen weeks was done by daily oral administration of TEO at doses 0.1, 0.25 and 0.5 g/kg b.wt. in Wistar rats. There were no mortality, adverse clinical signs or changes in body weight; water and food consumption during acute as well as subchronic toxicity studies. Indicators of hepatic function such as aspartate aminotransferase (AST), alanine amino transferase (ALT) and alkaline phosphatase (ALP) were unchanged in treated animals compared to untreated animals. Oral administration of TEO for 13 weeks did not alter total cholesterol, triglycerides, markers of renal function, serum electrolyte parameters and histopathology of tissues. TEO did not produce any mutagenicity to Salmonella typhimurium TA-98, TA-100, TA-102 and TA-1535 with or without metabolic activation. Administration of TEO to rats (1 g/kg b.wt.) for 14 days did not produce any chromosome aberration or micronuclei in rat bone marrow cells and did not produce any DNA damage as seen by comet assay confirming the non toxicity of TEO.