The potent and selective anti-tumor agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), localizes in lysosomes and forms cytotoxic copper complexes that generate reactive oxygen species (ROS), resulting in lysosomal membrane permeabilization (LMP) and cell death. Herein, the role of lysosomal membrane stability in the anti-tumor activity of Dp44mT was investigated. Studies were performed using molecules that protect lysosomal membranes against Dp44mT-induced LMP, namely heat shock protein 70 (HSP70) and cholesterol. Up-regulation or silencing of HSP70 expression did not affect Dp44mT-induced LMP in MCF7 cells. In contrast, cholesterol accumulation in lysosomes induced by the well characterized cholesterol transport inhibitor, 3-β-[2-(diethyl-amino)ethoxy]androst-5-en-17-one (U18666A), inhibited Dp44mT-induced LMP and markedly and significantly (p<0.001) reduced the ability of Dp44mT to inhibit cancer cell proliferation (i.e., increased the IC(50)) by 140-fold. On the other hand, cholesterol extraction using methyl-β-cyclodextrin enhanced Dp44mT-induced LMP and significantly (p<0.01) increased its anti-proliferative activity. The protective effect of U18666A in increasing lysosomal cholesterol and preventing the cytotoxic activity of Dp44mT was not due to induced autophagy. Instead, U18666A was found to decrease lysosomal turnover, resulting in autophagosome accumulation. Moreover, preincubation with U18666A did not prevent the ability of Dp44mT to induce autophagosome synthesis, indicating that autophagic initiation via Dp44mT occurs independently of LMP. These studies demonstrate the significance of lysosomal membrane stability in relation to the ability of Dp44mT to execute tumor cell death and overcome pro-survival autophagy. Hence, lysosomal-dependent cell death induced by Dp44mT serves as an important anti-tumor strategy. These results are important for comprehensively understanding the mechanism of action of Dp44mT.

Aims To apply combinations of monofunctional platinums with selected phytochemicals in human ovarian tumor models towards overcoming platinum resistance. Recently research has been directed at combinations of platinum drugs with tumor active phytochemicals towards a means of overcoming platinum resistance in ovarian cancer. In this study, two designed monofunctional planaramineplatinum(II) complexes, tris(8-hydroxyquinoline)monochloroplatinum(II) chloride (LH3) and tris(benzimidazole)chloroplatinum(II) chloride (LH4), were investigated for activity against human ovarian A2780, cisplatin-resistant A2780 (A2780cisR) and ZD0473-resistant A2780 (A2780ZD0473R) cancer cell lines, alone and in combination with curcumin, genistein, querceitin, capsaicin and resveratrol. Methods LH3 and LH4 were synthesized starting with potassium tetracloroplatinate and phytochemicals were obtained from commercial sources. Cytotoxicity was determined using MTT reduction assay. Cellular levels of glutathione before and after treatment were also determined. Interaction of the designed compounds with pBR322 plasmid DNA and damage to DNA in A2780 and A2780cisR cell lines due to interaction with designed compounds alone and in combination with phytochemicals were also investigated. Proteomic studies involving 2D-gel electrophoresis and mass spectrometry were carried out to identify key proteins associated with drug resistance in A2780 and A2780cisR cell lines. Results and Discussion LH3 and LH4 were found to be much more active than cisplatin against the resistant tumour models and greatest synergism in activity was observed when combinations of LH3 and LH4 with the phytochemicals were administered as a bolus. For combinations of LH3 and LH4 with the phytochemicals, platinum accumulation and the level of Pt-DNA binding were greater in the resistant A2780cisR cell line than in the parental A2780 cell line. Proteomic studies confirmed significant changes in expression of a number of proteins in A2780cisR cell line compared to the A2780 parent cell line. Greater activity of LH3 and LH4 than cisplatin against the resistant ovarian cell lines indicates that monofunctional platinums can be novel drug candidates with different cytotoxicity profiles from those of Pt drugs currently in use. The steric properties conveyed by the heterocylic ligands play a significant role in modulating their cytotoxicities and binary combination with tumour active phytochemicals can serve to further enhance drug efficacy. Conclusion Monofunctional platinums containing bulky planaramine ligands in combination with tumor active phytochemicals have the potential of overcoming platinum resistance in ovarian cancer cell lines. Acknowledgment This research was partly supported by Biomedical Science Research Initiative Grant and Biomedical Science Cancer Research Donation Fund. Citation Format: Laila Arzuman, Fazlul Huq, Jun Qing Yu, Philip Beale. Synergism from combinations of monofunctional platinums with phytochemicals in human ovarian cancer cell lines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3504. doi:10.1158/1538-7445.AM2015-3504

@s y d ne y .ed u .au @ Funding information 1 | BACKGROUND Ovarian cancer (OC) is the leading cause of death from gynaecological cancers in women [15, 36, 29] and the fifth most common cause of cancer deaths in women overall, with an estimated 239,000 new cases and over 152,000 deaths worldwide annually [10, 27]. It has a five year mortality rate in the United States of approximately 35% [12, 35] [3, 22].Current standard treatment mainly comprises platinum-based chemotherapeutics, with platinum drugs cisplatin and carboplatin given in combination with paclitaxel used to treat nearly all women with OC. However, the most prevalent OC type, high grade serous carcinoma (HGSC), often develops significant chemotherapy resistance alongside greatly altered genomes and transcriptome. Thus, most patients initially respond to the treatment, but over the longer term

Kinetics of alkaline hydrolysis of crystal violet (CV) in micellar solutions of a cationic surfactant, cetyltrymethylammonium bromide (CTAB) both in absence and presence of urea was investigated. The reaction was catalyzed by micelles of CTAB and addition of urea caused a gradual decrease in the rate of the reaction. Kinetic results could be correlated with change in micellization behavior of CTAB by water structure breaking effect of urea. The kinetic profiles have been fitted with the simulated profiles on the basis of pseudo-phase ion-exchange model and best fits with reasonable parameters could be obtained.