Redox modulation of oxidatively-induced DNA damage by ascorbate enhances both in vitro and ex-vivo DNA damage formation and cell death in melanoma cells.

Elevated genomic instability in cancer cells suggests a possible model-scenario for their selective killing via the therapeutic delivery of well-defined levels of further DNA damage. To examine this scenario, this study investigated the potential for redox modulation of oxidatively-induced DNA damage by ascorbate in malignant melanoma (MM) cancer cells, to selectively enhance both DNA damage and MM cell killing. DNA damage was assessed by Comet and ɣH2AX assays, intracellular oxidising species by dichlorofluorescein fluorescence, a key antioxidant enzymatic defence by assessment of catalase activity and cell survival was determined by clonogenic assay. Comet revealed that MM cells had higher endogenous DNA damage levels than normal keratinocytes (HaCaT cells); this correlated MM cells having higher intracellular oxidising species and lower catalase activity, and ranked with MM cell melanin pigmentation. Comet also showed MM cells more sensitive towards the DNA damaging effects of exogenous H2O2, and that ascorbate further enhanced this H2O2-induced damage in MM cells; again, with MM cell sensitivity to induced damage ranking with degree of cell pigmentation. Furthermore, cell survival data indicated that ascorbate enhanced H2O2-induced clonogenic cell death selectively in MM cells whilst protecting HaCaT cells. Finally, we show that ascorbate serves to enhance the oxidising effects of the MM therapeutic drug Elesclomol in both established MM cells in vitro and primary cell cultures ex vivo. Together, these results suggest that ascorbate selectively enhances DNA damage and cell-killing in MM cells. This raises the option of incorporating ascorbate into clinical oxidative therapies to treat MM.

Vitamin D level and endogenous DNA damage in patients with cancers in Duhok city, KRG-Iraq.

INTRODUCTION: Many clinical and pre-clinical studies suggested the protective effect of vitamin D against cancer development and cancer progression. Vitamin D deficiency is highly prevalent worldwide, and its link to DNA damage is worthy to study. It has been shown that vitamin D supplementation can reduce the risk of cancer with a favorable prognosis. Studies on DNA damage in different types of cancer and its link to plasma vitamin D has not been found in literature. PATIENTS AND METHODS: In this study we included 45 patients with different types of cancers and 35 healthy individuals as controls. The plasma vitamin D levels were measured in all participants. DNA damage levels of peripheral blood (mononuclear) cells in 45 newly diagnosed and untreated cancer patients and in 35 healthy individuals were measured using Alkaline Comet Assay technique. RESULTS: The DNA damage observed in cancer patients was significantly higher than in healthy individuals. Interestingly, we have found a significant inverse correlation between the plasma levels of vitamin D and DNA damage in cancer patients (p < 0.0001) and in healthy individuals (p < 0.001). CONCLUSION: There is an inverse association between endogenous DNA damage and plasma vitamin D levels. Patients with vitamin D deficiency show highest levels of DNA damage suggesting that deficiency of vitamin D is probably one of the factors which increases the risk of cancer.

Parental history of coronary artery disease among adults with hypothyroidism: Case controlled study.

BACKGROUND: Thyroid dysfunction has a negative impact on coronary artery diseases (CAD) through several changes in its risk factors like dyslipidemia, glucose intolerance, and components of metabolic syndrome. Parental history of premature CAD may be an important risk factor for their offspring. OBJECTIVE: To investigate whether overt and subclinical hypothyroidism and the risk of atherosclerosis are present in adults with parental history of CAD. MATERIALS AND METHODS: This case control study included 135 hypothyroid patients and 100 age-sex matched controls. Data were analyzed regarding CAD risk factors, hormonal and biochemical measures including retinol Binding Protein-4, fasting serum insulin, high-sensitivity C-reactive protein, lipid profile, fasting serum glucose, and serum malondialdehyde. RESULTS: Parental history of CAD was significantly higher in overt hypothyroidism than subclinical group (P = 0.001). The level of RBP-4 in hypothyroid patients was significantly higher than euthyroid subjects (P = 0.03), and was higher in hypothyroid patients with positive parental history of CAD (p = 0.01). There were positive relationships between RBP-4 and related cardiovascular risk factors and with hypothyroidism, its sensitivity and specificity were 47.9% and 42.5% respectively. The positive predictive value was 60.8% and the negative predictive value was 30.4%. Hypothyroid patients with parental history of CAD had a risk of 3.7 times more than the euthyroid subjects. CONCLUSIONS: In hypothyroidism patients, parental history of CAD is a predictor of future coronary events and the related risk factors. RBP-4 is positively correlated with waist circumference, BMI, lipid profile, High-sensitivity CRP, MDA, fasting serum glucose, fasting serum insulin, HOMA indices and TSH.

BTK Modulates p53 Activity to Enhance Apoptotic and Senescent Responses.

p53 is a tumor suppressor that prevents the emergence of transformed cells by inducing apoptosis or senescence, among other responses. Its functions are regulated tightly by posttranslational modifications. Here we show that Bruton's tyrosine kinase (BTK) is a novel modulator of p53. We found that BTK is induced in response to DNA damage and p53 activation. BTK induction leads to p53 phosphorylation, which constitutes a positive feedback loop that increases p53 protein levels and enhances the transactivation of its target genes in response to stress. Inhibiting BTK reduced both p53-dependent senescence and apoptosis. Further, BTK expression also upregulated DNA damage signals and apoptosis. We conclude that despite being involved in oncogenic signals in blood malignancies, BTK has antineoplastic properties in other contexts, such as the enhancement of p53's tumor suppressor responses. Along with evidence that BTK expression correlates with good prognosis in some epithelial tumors, our findings may encourage a reevaluation of the clinical uses of BTK inhibitors in cancer therapy. Cancer Res; 76(18); 5405-14. ©2016 AACR.

Posttranscriptional Upregulation of p53 by Reactive Oxygen Species in Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) cells multiply and become more resistant to immunochemotherapy in "proliferation centers" within tissues, whereas apoptosis occurs in the periphery. Various models recapitulate these microenvironments in vitro, such as stimulation with CD154 and IL4. Using this system, we observed a 30- to 40-fold induction of wild-type p53 protein in 50 distinct human CLL specimens tested, without the induction of either cell-cycle arrest or apoptosis. In contrast, the mRNA levels for p53 did not increase, indicating that its elevation occurred posttranscriptionally. Mechanistic investigations revealed that under the conditions studied, p53 was phosphorylated on residues associated with p53 activation and increased half-life. However, p53 protein induced in this manner could transcriptionally activate only a subset of target genes. The addition of a DNA-damaging agent further upregulated p53 protein levels, which led to apoptosis. p53 induction relied on the increase in intracellular reactive oxygen species observed after CD154 and IL4 stimulation. We propose that chronic oxidative stress is a characteristic of the microenvironment in B-cell "proliferation centers" in CLL that are capable of elevating the basal expression of p53, but to levels below the threshold needed to induce arrest or apoptosis. Our findings suggest that reactivation of the full transcriptional activities of p53 in proliferating CLL cells may offer a possible therapeutic strategy. Cancer Res; 76(21); 6311-9. ©2016 AACR.