Essential oil from leaves of Conobea scoparioides (Cham. & Schltdl.) Benth. (Plantaginaceae) causes cell death in HepG2 cells and inhibits tumor development in a xenograft model

Conobea scoparioides (Cham. & Schltdl.) Benth. (syn. Sphaerotheca scoparioides Cham. & Schldtl.) (Plantaginaceae), popularly known as "pataqueira", "vassourinha-do-brejo" and/or "hierba-de-sapo", is a popular medicinal plant used to treat leishmaniasis, pain and beriberi. In addition, inhibition of cell adhesion, antioxidant, cytotoxic and leishmanicidal activities of compounds or fractions of C. scoparioides have been reported. In the present work, chemical constituents and in vitro and in vivo anti-liver cancer potential of essential oil (EO) from leaves of C. scoparioides were investigated using human hepatocellular carcinoma HepG2 cells as a cell model. EO was obtained by hydrodistillation using a Clevenger-type apparatus and characterized by GC-MS and GC-FID. The in vitro cytotoxic effect was evaluated on three human cancer cell lines (MCF-7, HepG2 and HCT116) and one human non-cancerous cell line (MRC-5) using the Alamar blue assay. Phosphatidylserine externalization and cell cycle distribution were quantified in HepG2 cells by flow cytometry after 48 h incubation. The effectiveness of EO in anti-liver cancer model was studied with HepG2 cells grafted on C.B. 17 SCID mice. The main constituents of EO were thymol methyl ether (62 %), thymol (16 %) and α-phellandrene (14 %). EO displayed an in vitro cytotoxic effect against all human cancer cell lines and caused externalization of phosphatidylserine and DNA fragmentation in HepG2 cells, suggesting induction of apoptotic-like cell death. In vivo tumor mass inhibition of 36.7 and 55.8 % was observed for treatment with EO at doses of 40 and 80 mg/kg, respectively. These results indicate in vitro and in vivo anti-liver cancer potential of EO from leaves of C. scoparioides.

Ruthenium(II) complexes with 6-methyl-2-thiouracil selectively reduce cell proliferation, cause DNA double-strand break and trigger caspase-mediated apoptosis through JNK/p38 pathways in human acute promyelocytic leukemia cells

Ruthenium(II) complexes with 6-methyl-2-thiouracil cis-[Ru(6m2tu)₂(PPh₃)₂] (1) and [Ru(6m2tu)₂(dppb)] (2) (where PPh_3 =triphenylphosphine; dppb = 1,4-bis(diphenylphosphino)butane; and 6m2tu = 6-methyl-2-thiouracil) are potent cytotoxic agents and able to bind DNA. The aim of this study was to evaluate in vitro cellular underlying mechanism and in vivo effectiveness of these ruthenium(II) complexes in human acute promyelocytic leukemia HL-60 cells. Both complexes displayed potent and selective cytotoxicity in myeloid leukemia cell lines, and were detected into HL-60 cells. Reduction of the cell proliferation and augmented phosphatidylserine externalization, caspase-3, -8 and -9 activation and loss of mitochondrial transmembrane potential were observed in HL-60 cells treated with both complexes. Cotreatment with Z-VAD(OMe)-FMK, a pan-caspase inhibitor, reduced Ru(II) complexes-induced apoptosis. In addition, both metal complexes induced phosphorylation of histone H2AX (S139), JNK2 (T183/Y185) and p38α (T180/Y182), and cotreatment with JNK/SAPK and p38 MAPK inhibitors reduced complexes-induced apoptosis, indicating DNA double-strand break and activation of caspase-mediated apoptosis through JNK/p38 pathways. Complex 1 also reduced HL-60 cell growth in xenograft model. Overall, the outcome indicated the ruthenium(II) complexes with 6-methyl-2-thiouracil as a novel promising antileukemic drug candidates.

Ru(II)-thymine complex causes DNA damage and apoptotic cell death in human colon carcinoma HCT116 cells mediated by JNK/p38/ERK1/2 via a p53-independent signaling

Ru(II)-thymine complex [Ru(PPh₃)₂(Thy)(bipy)]PF₆ (where PPh₃ = triphenylphosphine, Thy = thyminate and bipy = 2,2′-bipyridine) is a potent cytotoxic agent with ability to bind to DNA, inducing caspase-mediated apoptosis in leukemia cells. In this study, we investigated the mechanism underlying the cell death induction by Ru(II)-thymine complex in human colon carcinoma HCT116 cells, as well as its effect in xenograft tumor model. The Ru(II)-thymine complex increased significantly the percentage of apoptotic HCT116 cells. Co-treatment with a JNK/SAPK inhibitor, p38 MAPK inhibitor and MEK inhibitor, which inhibit the activation of ERK1/2, caused a marked reduction of the percentage of complex-induced apoptotic cells. Moreover, the Ru(II)-thymine complex induced an increase in phospho-JNK2 (T183/Y185), phospho-p38α (T180/Y182) and phospho-ERK1 (T202/Y204) levels in HCT116 cells. Treatment with the Ru(II)-thymine complex increased significantly the phospho-histone H2AX (S139) expression, a DNA damage marker. The expression of phospho-p53 (S15) and MDM2 were not changed, and the co-treatment with a p53 inhibitor (cyclic pifithrin-α) did not reduce the complex-induced apoptosis in HCT116 cells, indicating that the Ru(II)-thymine complex induces DNA damage-mediated apoptosis by JNK/p38/ERK1/2 via a p53-independent signaling. The Ru(II)-thymine complex (1 and 2 mg/kg/day) also inhibited HCT116 cell growth in a xenograft model, reducing the tumor mass at 32.6–40.1%. Altogether, indicate that the Ru(II)-thymine complex is a promising anti-colon cancer drug candidate.

Ruthenium Complexes Containing Heterocyclic Thioamidates Trigger Caspase-Mediated Apoptosis Through MAPK Signaling in Human Hepatocellular Carcinoma Cells

Herein, ruthenium complexes containing heterocyclic thioamidates [Ru(mmi)(bipy)(dppb)]PF₆ (1), [Ru(tzdt)(bipy)(dppb)]PF₆ (2), [Ru(dmp)(bipy)(dppb)]PF₆ (3) and [Ru(mpca)(bipy)(dppb)]PF₆ (4) were investigated for their cellular and molecular effects in cancer cell lines. Complexes 1 and 2 were the most potent of the four compounds against a panel of different cancer cell lines in monolayer cultures and showed potent cytotoxicity in a 3D model of multicellular spheroids that formed from human hepatocellular carcinoma HepG2 cells. In addition, both complexes were able to bind to DNA in a calf thymus DNA model. Compared to the controls, a reduction in cell proliferation, phosphatidylserine externalization, internucleosomal DNA fragmentation, and the loss of the mitochondrial transmembrane potential were observed in HepG2 cells that were treated with these complexes. Additionally, coincubation with a pan-caspase inhibitor (Z-VAD(OMe)-FMK) reduced the levels of apoptosis that were induced by these compounds compared to those in the negative controls, indicating that cell death through apoptosis occurred via a caspase-dependent pathway. Moreover, these complexes also induced the phosphorylation of ERK1/2, and coincubation with an MEK inhibitor (U0126), which is known to inhibit the activation of ERK1/2, but not JNK/SAPK and p38 MAPK inhibitors, reduced the complexes-induced apoptosis compared to that in the negative controls, indicating that the induction of apoptotic cell death occurred through ERK1/2 signaling in HepG2 cells. On the other hand, no increase in oxidative stress was observed in HepG2 cells treated with the complexes, and the complexes-induced apoptosis was not reduced with coincubation with the antioxidant N-acetylcysteine or a p53 inhibitor compared to that in the negative controls, indicating that apoptosis occurred via oxidative stress- and p53-independent pathways. Finally, these complexes also reduced the growth of HepG2 cells that were engrafted in C.B-17 SCID mice compared to that in the negative controls. These results indicated that these complexes are novel anticancer drug candidates for liver cancer treatment.

Ruthenium Complexes With Piplartine Cause Apoptosis Through MAPK Signaling by a p53-Dependent Pathway in Human Colon Carcinoma Cells and Inhibit Tumor Development in a Xenograft Model

Ruthenium complexes with piplartine, [Ru(piplartine)(dppf)(bipy)](PF₆)₂ (1) and [Ru(piplartine)(dppb)(bipy)](PF₆)₂ (2) (dppf = 1,1-bis(diphenylphosphino) ferrocene; dppb = 1,4-bis(diphenylphosphino)butane and bipy = 2,2′-bipyridine), were recently synthesized and displayed more potent cytotoxicity than piplartine in different cancer cells, regulated RNA transcripts of several apoptosis-related genes, and induced reactive oxygen species (ROS)-mediated apoptosis in human colon carcinoma HCT116 cells. The present work aimed to explore the underlying mechanisms through which these ruthenium complexes induce cell death in HCT116 cells in vitro, as well as their in vivo action in a xenograft model. Both complexes significantly increased the percentage of apoptotic HCT116 cells, and co-treatment with inhibitors of JNK/SAPK, p38 MAPK, and MEK, which inhibits the activation of ERK1/2, significantly reduced the apoptosis rate induced by these complexes. Moreover, significant increase in phospho-JNK2 (T183/Y185), phospho-p38α (T180/Y182), and phospho-ERK1 (T202/Y204) expressions were observed in cells treated with these complexes, indicating MAPK-mediated apoptosis. In addition, co-treatment with a p53 inhibitor (cyclic pifithrin-α) and the ruthenium complexes significantly reduced the apoptosis rate in HCT116 cells, and increased phospho-p53 (S15) and phospho-histone H2AX (S139) expressions, indicating induction of DNA damage and p53-dependent apoptosis. Both complexes also reduced HCT116 cell growth in a xenograft model. Tumor mass inhibition rates were 35.06, 29.71, and 32.03% for the complex 1 (15 μmol/kg/day), complex 2 (15 μmol/kg/day), and piplartine (60 μmol/kg/day), respectively. These data indicate these ruthenium complexes as new anti-colon cancer drugs candidates.

In vitro and in vivo anti-leukemia activity of the stem bark of Salacia impressifolia (Miers) A. C. Smith (Celastraceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Salacia impressifolia (Miers) A. C. Smith (family Celastraceae) is a traditional medicinal plant found in the Amazon Rainforest known as "miraruíra", "cipó-miraruíra" or "panu" and is traditionally used to treat dengue, flu, inflammation, pain, diabetes, male impotency, renal affections, rheumatism and cancer.

AIM OF THE STUDY

The aim of this study was to investigate in vitro and in vivo anti-leukemia activity of the stem bark of S. impressifolia in experimental models.

MATERIALS AND METHODS

The in vitro cytotoxic activity of extracts, fractions and quinonemethide triterpenes (22-hydroxytingenone, tingenone and pristimerin) from the stem bark of S. impressifolia in cultured cancer cells was determined. The in vivo antitumor activity of the ethyl acetate extract (EAE) and of its fraction (FEAE.3) from the stem bark of S. impressifolia was assessed in C.B-17 severe combined immunodeficient (SCID) mice engrafted with human promyelocytic leukemia HL-60 cells.

RESULTS

The extract EAE, its fraction FEAE.3, and quinonemethide triterpenes exhibited potent cytotoxicity against cancer cell lines, including in vitro anti-leukemia activity against HL-60 and K-562 cells. Moreover, extract EAE and its fraction FEAE.3 inhibited the in vivo development of HL-60 cells engrafted in C.B-17 SCID mice. Tumor mass inhibition rates were measured as 40.4% and 81.5% for the extract EAE (20 mg/kg) and for its fraction FEAE.3 (20 mg/kg), respectively.

CONCLUSIONS

Ethyl acetate extract and its fraction from the stem bark of S. impressifolia exhibit in vitro and in vivo anti-leukemia activity that can be attributed to their quinonemethide triterpenes. These data confirm the ethnopharmacological use of this species and may contribute to the development of a novel anticancer herbal medicine.

A novel ruthenium complex with xanthoxylin induces S-phase arrest and causes ERK1/2-mediated apoptosis in HepG2 cells through a p53-independent pathway

Ruthenium-based compounds have gained great interest due to their potent cytotoxicity in cancer cells; however, much of their potential applications remain unexplored. In this paper, we report the synthesis of a novel ruthenium complex with xanthoxylin (RCX) and the investigation of its cellular and molecular action in human hepatocellular carcinoma HepG2 cells. We found that RCX exhibited a potent cytotoxic effect in a panel of cancer cell lines in monolayer cultures and in a 3D model of multicellular cancer spheroids formed from HepG2 cells. This compound is detected at a high concentration in the cell nuclei, induces DNA intercalation and inhibits DNA synthesis, arresting the cell cycle in the S-phase, which is followed by the activation of the caspase-mediated apoptosis pathway in HepG2 cells. Gene expression analysis revealed changes in the expression of genes related to cell cycle control, apoptosis and the MAPK pathway. In addition, RCX induced the phosphorylation of ERK1/2, and pretreatment with U-0126, an MEK inhibitor known to inhibit the activation of ERK1/2, prevented RCX-induced apoptosis. In contrast, pretreatment with a p53 inhibitor (cyclic pifithrin-α) did not prevent RCX-induced apoptosis, indicating the activation of a p53-independent apoptosis pathway. RCX also presented a potent in vivo antitumor effect in C.B-17 SCID mice engrafted with HepG2 cells. Altogether, these results indicate that RCX is a novel anticancer drug candidate.

Novel piplartine-containing ruthenium complexes: synthesis, cell growth inhibition, apoptosis induction and ROS production on HCT116 cells

Piplartine (piperlongumine) is a plant-derived molecule that has been receiving intense interest due to its anticancer characteristics that target the oxidative stress. In the present paper, two novel piplartine-containing ruthenium complexes [Ru(piplartine)(dppf)(bipy)](PF₆)₂ (1) and [Ru(piplartine)(dppb)(bipy)](PF₆)₂ (2) were synthesized and investigated for their cellular and molecular responses on cancer cell lines. We found that both complexes are more potent than metal-free piplartine in a panel of cancer cell lines on monolayer cultures, as well in 3D model of cancer multicellular spheroids formed from human colon carcinoma HCT116 cells. Mechanistic studies uncovered that the complexes reduced the cell growth and caused phosphatidylserine externalization, internucleosomal DNA fragmentation, caspase-3 activation and loss of the mitochondrial transmembrane potential on HCT116 cells. Moreover, the pre-treatment with Z-VAD(OMe)-FMK, a pan-caspase inhibitor, reduced the complexes-induced apoptosis, indicating cell death by apoptosis through caspase-dependent and mitochondrial intrinsic pathways. Treatment with the complexes also caused a marked increase in the production of reactive oxygen species (ROS), including hydrogen peroxide, superoxide anion and nitric oxide, and decreased reduced glutathione levels. Application of N-acetyl-cysteine, an antioxidant, reduced the ROS levels and apoptosis induced by the complexes, indicating activation of ROS-mediated apoptosis pathway. RNA transcripts of several genes, including gene related to the cell cycle, apoptosis and oxidative stress, were regulated under treatment. However, the complexes failed to induce DNA intercalation. In conclusion, the complexes are more potent than piplartine against different cancer cell lines and are able to induce caspase-dependent and mitochondrial intrinsic apoptosis on HCT116 cells by ROS-mediated pathway.