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 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.

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.

Antitumor Properties of the leaf essential oil of Zornia brasiliensis

Zornia brasiliensis, popularly known as "urinária", "urinana", and "carrapicho", is a medicinal plant used in Brazilian northeast folk medicine as a diuretic and against venereal diseases. The aim of this study was to investigate the chemical composition and antitumor potential of the leaf essential oil of Z. brasiliensis. The essential oil was obtained by hydrodistillation using a Clevenger-type apparatus and analyzed by GC-MS and GC-FID. Its composition was characterized by the presence of trans-nerolidol, germacrene D, trans-caryophyllene, α-humulene, and farnesene as major constituents. In vitro cytotoxicity of the essential oil and some of its major constituents (trans-nerolidol, trans-caryophyllene, and α-humulene) was evaluated for tumor cell lines from different histotypes using the Alamar blue assay. The essential oil, but not the constituents tested, presented promising cytotoxicity. Furthermore, mice inoculated with B16-F10 mouse melanoma were used to confirm its in vivo effectiveness. An in vivo antitumor study showed tumor growth inhibition rates of 1.68-38.61 % (50 and 100 mg/kg, respectively). In conclusion, the leaf essential oil of Z. brasiliensis presents trans-nerolidol, germacrene D, trans-caryophyllene, α-humulene, and farnesene as major constituents and is able to inhibit cell proliferation in cultures as well as in tumor growth in mice.