The role of p38 MAP kinase in the synergistic cytotoxic action of calcitriol and TNF-alpha in human breast cancer cells

Programmed cell death of stressed keratinocytes and its inhibition by vitamin D: The role of death and survival signaling pathways

The epidermis is confronted with multiple environmental and pathophysiological stresses. This study shows that TNFalpha, oxidative stress, hyperosmotic and heat shock induced both caspase-dependent and independent cell death in human HaCaT keratinocytes. The hormonal form of vitamin D, 1,25(OH)2D3, which is an autocrine hormone in the epidermis, protected the cells from all the examined stresses and pathways leading to cell death. We aimed to define the signaling pathways that determine the life-death balance of stressed keratinocytes and participate in their protection by 1,25(OH)2D3. As assessed by employing specific inhibitors, the survival pathways mediated by the EGF receptor, ERK, PI-3K or Src kinase, or basal transcriptional activity are important for unstressed cell survival. However, only the EGF receptor, PI-3K and the Src kinase pathways mediate the survival of stressed cells in a stimulus-specific manner. Inhibition of the p38 and/or the JNK death pathways reduced caspase activation induced by oxidative stress, hyperosmotic shock and TNFalpha. The protective effect of 1,25(OH)2D3 was not mediated by the examined survival pathways. 1,25(OH)2D3 inhibited the stress-induced activation of p38 and JNK. Since mimicking this effect by pharmacological inhibition resulted in the attenuation of caspase activation, we infer that these pathways are involved in keratinocyte protection by 1,25(OH)2D3.

TNF-alpha levels in cancer patients relate to social variables

Tumor necrosis factor-alpha (TNF-alpha) is an important cytokine associated with tumor regression and increased survival time for cancer patients. Research evidence relates immune factors (e.g., natural killer (NK) cell counts, NK cell lysis, lymphocyte profile, and lymphocyte proliferation) to the frequency and quality of social relations among cancer patients. We hypothesized that disruptions in social relations would be associated with lower TNF-alpha responses, and conversely, that reports of positive changes in social relations correlate with stronger responses. A prospective design measured changes in social activity and relationship satisfaction with a partner in 44 breast cancer patients at the time of cancer diagnosis, and initial surgery and 12 months later. Results indicated that patients reporting increased social activities or satisfaction exhibited stronger stimulated TNF-alpha responses. This is the first study to link changes in patient social relations with a cancer-relevant immune variable.

Altered thioredoxin subcellular localization and redox status in MCF-7 cells following 1,25-dihydroxyvitamin D3 treatment

1,25-Dihydroxyvitamin D(3) (1,25D) induces apoptosis in MCF-7 cells via the intrinsic pathway involving bax translocation to mitochondria, cytochrome c release and reactive oxygen species (ROS) generation. Vitamin D up-regulated protein 1 (VDUP1), an apoptotic regulatory gene induced by 1,25D in HL-60 cells, is a negative regulator of thioredoxin (Trx1), a redox protein which neutralizes ROS and protects against oxidative stress induced apoptosis. Due to the involvement of oxidative stress in 1,25D mediated apoptosis, we analyzed whether VDUP1 or Trx1 are altered by 1,25D in MCF-7 cells. In contrast to HL-60 cells, VDUP1 mRNA was not up-regulated by 1,25D in MCF-7 cells, indicating that transcriptional up-regulation of this gene is not required for 1,25D mediated apoptosis. 1,25D did not affect the expression or activity of Trx1 in MCF-7 cells, however, Trx1 activity was higher in MCF-7 cells selected for resistance to 1,25D mediated apoptosis. In untreated MCF-7 cells, Trx1 was present only in the cytosol, and the majority was in the oxidized state. In 1,25D treated MCF-7 cells, Trx1 was present in both cytosol and nucleus, and the nuclear Trx1 pool was in the reduced state. Nuclear localization of Trx1 in 1,25D treated MCF-7 cells was confirmed by immunofluorescent microscopy. Although redox status is known to alter the ability of Trx1 to bind apoptosis signal regulating kinase 1 (ASK1), no changes in ASK1 transcript or protein levels were observed in 1,25D treated MCF-7 cells. Collectively, these studies indicate that although VDUP1 and ASK1 are not altered by 1,25D, changes in redox status and sub-cellular distribution of Trx1 occurs during 1,25D mediated apoptosis of MCF-7 cells.