The Cystine/Cysteine Cycle and GSH Are Independent and Crucial Antioxidant Systems in Malignant Melanoma Cells and Represent Druggable Targets

Abstract Aims: Cancer chemoresistance is often due to upregulation of antioxidant systems. Therapeutic targeting of these systems is however hampered by their redundancy. Here, we have performed a functional dissection of the antioxidant systems in different melanoma cases aimed at the identification of the most effective redox active drug. Results: We have identified two crucial antioxidant mechanisms: glutathione (GSH), the major intracellular redox buffer, and the cystine/cysteine cycle, which switches the extracellular redox state from an oxidized to a reduced state. The two mechanisms are independent in melanoma cells and may be substitutes for each other, but targeting both of them is lethal. Exposure to the pro-oxidant compound As(2)O(3) induces an antioxidant response. However, while in these cells the intracellular redox balance remains almost unaffected, a reduced environment is generated extracellularly. GSH depletion by buthioninesulfoximine (BSO), or cystine/cysteine cycle inhibition by (S)-4-carboxyphenylglycine (sCPG), enhanced the sensitivity to As(2)O(3). Remarkably, sCPG also prevented the remodeling of the microenvironment redox state. Innovation: We propose that the definition of the prevalent antioxidant system(s) in tumors is crucial for the design of tailored therapies involving redox-directed drugs in association with pro-oxidant drugs. Conclusion: In melanoma cells, BSO is the best enhancer of As(2)O(3) sensitivity. However, since the strong remodeling of the microenvironmental redox state caused by As(2)O(3) may promote tumor progression, the concomitant use of cystine/cysteine cycle blockers is recommended. Antioxid. Redox Signal. 00, 000-000

KAVA Chalcone, Flavokawain A, Inhibits Urothelial Tumorigenesis in the UPII-SV40T Transgenic Mouse Model

Flavokawain A (FKA) is the predominant chalcone identified from the kava plant. We have previously demonstrated that FKA preferentially inhibits the growth of p53 defective bladder cancer cell lines. Here we examined whether FKA could inhibit bladder cancer development and progression in vivo in the UPII-SV40T transgenic model that resembles human urothelial cell carcinoma (UCC) with defects in the p53 and the retinoblastoma (RB) protein pathways. Genotyped UPII-SV40T mice were fed orally with vehicle control (AIN-93M) or FKA (6 g/kg food; 0.6%) for 318 days starting at 28 days of age. More than 64% of the male mice fed with FKA-containing food survived beyond 318 days of age, whereas only about 38% of the male mice fed with vehicle control food survived to that age (p= 0.0383). The mean bladder weights of surviving male transgenic mice with the control diet versus the FKA diet were 234.6 ± 72.5 versus 96.1±69.4 mg (P=0.0002). FKA was excreted primarily through the urinary tract and concentrated in the urine up to 8.4 μmol/L, averaging about 38 times (males) and 15 times (females) more concentrated than in the plasma (P=0.0001). FKA treatment inhibited the occurrence of high-grade papillary UCC, a precursor to invasive urothelial cancer, by 42.1%. A decreased expression of Ki67, survivin and XIAP and increased expression of p27 and DR5 and number of TUNEL-positive apoptotic cells were observed in the urothelial tissue of FKA-fed mice. These results suggest a potential of FKA in preventing the recurrence and progression of non-muscle invasive UCC

Thrombotic thrombocytopenic purpura and defective apoptosis due to CASP8/10 mutations: the role of mycophenolate mofetil

Key Points Immunological dysregulation may underlie unusual autoimmune diseases, which also deserve to be investigated from a genetic point of view.</jats:p