2,5-Di-tert-butyl-1,4-hydroquinone enhances cell transformation accompanied by an increase in intracellular free calcium ion concentration

The distinguishing electrical properties of cancer cells

In recent decades, medical research has been primarily focused on the inherited aspect of cancers, despite the reality that only 5-10% of tumours discovered are derived from genetic causes. Cancer is a broad term, and therefore it is inaccurate to address it as a purely genetic disease. Understanding cancer cells' behaviour is the first step in countering them. Behind the scenes, there is a complicated network of environmental factors, DNA errors, metabolic shifts, and electrostatic alterations that build over time and lead to the illness's development. This latter aspect has been analyzed in previous studies, but how the different electrical changes integrate and affect each other is rarely examined. Every cell in the human body possesses electrical properties that are essential for proper behaviour both within and outside of the cell itself. It is not yet clear whether these changes correlate with cell mutation in cancer cells, or only with their subsequent development. Either way, these aspects merit further investigation, especially with regards to their causes and consequences. Trying to block changes at various levels of occurrence or assisting in their prevention could be the key to stopping cells from becoming cancerous. Therefore, a comprehensive understanding of the current knowledge regarding the electrical landscape of cells is much needed. We review four essential electrical characteristics of cells, providing a deep understanding of the electrostatic changes in cancer cells compared to their normal counterparts. In particular, we provide an overview of intracellular and extracellular pH modifications, differences in ionic concentrations in the cytoplasm, transmembrane potential variations, and changes within mitochondria. New therapies targeting or exploiting the electrical properties of cells are developed and tested every year, such as pH-dependent carriers and tumour-treating fields. A brief section regarding the state-of-the-art of these therapies can be found at the end of this review. Finally, we highlight how these alterations integrate and potentially yield indications of cells' malignancy or metastatic index.

Screening for Small Molecule Inhibitors of Statin-Induced APP C-terminal Toxic Fragment Production

Alzheimer's disease (AD) is characterized by neuronal and synaptic loss. One process that could contribute to this loss is the intracellular caspase cleavage of the amyloid precursor protein (APP) resulting in release of the toxic C-terminal 31-amino acid peptide APP-C31 along with the production of APPΔC31, full-length APP minus the C-terminal 31 amino acids. We previously found that a mutation in APP that prevents this caspase cleavage ameliorated synaptic loss and cognitive impairment in a murine AD model. Thus, inhibition of this cleavage is a reasonable target for new therapeutic development. In order to identify small molecules that inhibit the generation of APP-C31, we first used an APPΔC31 cleavage site-specific antibody to develop an AlphaLISA to screen several chemical compound libraries for the level of N-terminal fragment production. This antibody was also used to develop an ELISA for validation studies. In both high throughput screening (HTS) and validation testing, the ability of compounds to inhibit simvastatin- (HTS) or cerivastatin- (validation studies) induced caspase cleavage at the APP-D720 cleavage site was determined in Chinese hamster ovary (CHO) cells stably transfected with wildtype (wt) human APP (CHO-7W). Several compounds, as well as control pan-caspase inhibitor Q-VD-OPh, inhibited APPΔC31 production (measured fragment) and rescued cell death in a dose-dependent manner. The effective compounds fell into several classes including SERCA inhibitors, inhibitors of Wnt signaling, and calcium channel antagonists. Further studies are underway to evaluate the efficacy of lead compounds - identified here using cells and tissues expressing wt human APP - in mouse models of AD expressing mutated human APP, as well as to identify additional compounds and determine the mechanisms by which they exert their effects.

Modulation of endoplasmic reticulum calcium pump expression during lung cancer cell differentiation

Cellular calcium signaling plays important roles in several signal transduction pathways that control proliferation, differentiation and apoptosis. In epithelial cells calcium signaling is initiated mainly by calcium release from endoplasmic-reticulum-associated intracellular calcium pools. Because calcium is accumulated in the endoplasmic reticulum by sarco/endoplasmic reticulum calcium ATPases (SERCA), these enzymes play a critical role in the control of calcium-dependent cell activation, growth and survival. We investigated the modulation of SERCA expression and function in human lung adenocarcinoma cells. In addition to the ubiquitous SERCA2 enzyme, the SERCA3 isoform was also expressed at variable levels. SERCA3 expression was selectively enhanced during cell differentiation in lung cancer cells, and marked SERCA3 expression was found in fully differentiated normal bronchial epithelium. As studied by using a recombinant fluorescent calcium probe, induction of the expression of SERCA3, a lower calcium affinity pump, was associated with decreased intracellular calcium storage, whereas the amplitude of capacitative calcium influx remained unchanged. Our observations indicate that the calcium homeostasis of the endoplasmic reticulum in lung adenocarcinoma cells presents a functional defect due to decreased SERCA3 expression that is corrected during pharmacologically induced differentiation. The data presented in this work show, for the first time, that endoplasmic reticulum calcium storage is anomalous in lung cancer cells, and suggest that SERCA3 may serve as a useful new phenotypic marker for the study of lung epithelial differentiation.

Endoplasmic reticulum calcium pumps and cancer cell differentiation

The endoplasmic reticulum (ER) is a major intracellular calcium storage pool and a multifunctional organelle that accomplishes several calcium-dependent functions involved in many homeostatic and signaling mechanisms. Calcium is accumulated in the ER by Sarco/Endoplasmic Reticulum Calcium ATPase (SERCA)-type calcium pumps. SERCA activity can determine ER calcium content available for intra-ER functions and for calcium release into the cytosol, and can shape the spatiotemporal characteristics of calcium signals. SERCA function therefore constitutes an important nodal point in the regulation of cellular calcium homeostasis and signaling, and can exert important effects on cell growth, differentiation and survival. In several cell types such as cells of hematopoietic origin, mammary, gastric and colonic epithelium, SERCA2 and SERCA3-type calcium pumps are simultaneously expressed, and SERCA3 expression levels undergo significant changes during cell differentiation, activation or immortalization. In addition, SERCA3 expression is decreased or lost in several tumor types when compared to the corresponding normal tissue. These observations indicate that ER calcium homeostasis is remodeled during cell differentiation, and may present defects due to decreased SERCA3 expression in tumors. Modulation of the state of differentiation of the ER reflected by SERCA3 expression constitutes an interesting new aspect of cell differentiation and tumor biology.

A porous Cu/LDPE composite for copper-containing intrauterine contraceptive devices

To improve the rates of both cupric ion release and the utilization of copper in non-porous copper/low-density polyethylene (Cu/LDPE) composite, a porous Cu/LDPE composite is proposed and developed in the present work. Here 2,5-di-tert-butylhydroquinone was chosen as the porogen, ethyl acetate was chosen as the solvent for extraction, and the porous Cu/LDPE composite was obtained by using injection molding and the particulate leaching method. After any residual ethyl acetate remaining inside the porous Cu/LDPE composite had been removed by vacuum drying, the composite was characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry and absorption measurement. For comparison, a non-porous Cu/LDPE composite was also characterized in the same way. The results show that the porous structure was successfully introduced into the polymeric base of the non-porous Cu/LDPE composite, and the porous Cu/LDPE composite is a simple hybrid of copper particles and porous LDPE. The results also show that the introduction of a porous structure can improve the cupric ion release rate of the non-porous Cu/LDPE composite with a certain content of copper particles, indicating that the utilization rate of copper can be improved either the introduction of a porous structure, and that the porous Cu/LDPE composite is another promising material for copper-containing intrauterine devices.

Endoplasmic reticulum calcium pumps and cancer

Endoplasmic reticulum calcium homeostasis is involved in a multitude of signaling, as well as "house-keeping" functions that control cell growth, differentiation or apoptosis in every human/eukaryotic cell. Calcium is actively accumulated in the endoplasmic reticulum by Sarco/Endoplasmic Reticulum Calcium transport ATPases (SERCA enzymes). SERCA-dependent calcium transport is the only calcium uptake mechanism in this organelle, and therefore the regulation of SERCA function by the cell constitutes a key mechanism to adjust calcium homeostasis in the endoplasmic reticulum depending on the cell type and its state of differentiation. The direct pharmacological modulation of SERCA activity affects cell differentiation and survival. SERCA expression levels can undergo significant changes during cell differentiation or tumorigenesis, leading to modified endoplasmic reticulum calcium storage. In several cell types such as cells of hematopoietic origin or various epithelial cells, two SERCA genes (SERCA2 and SERCA3) are simultaneously expressed. Expression levels of SERCA3, a lower calcium affinity calcium pump are highly variable. In several cell systems SERCA3 expression is selectively induced during differentiation, whereas during tumorigenesis and blastic transformation SERCA3 expression is decreased. These observations point at the existence of a cross-talk, via the regulation of SERCA3 levels, between endoplasmic reticulum calcium homeostasis and the control of cell differentiation, and show that endoplasmic reticulum calcium homeostasis itself can undergo remodeling during differentiation. The investigation of the anomalies of endoplasmic reticulum differentiation in tumor and leukemia cells may be useful for a better understanding of the contribution of calcium signaling to the establishment of malignant phenotypes.

Alterations in the ATP2A2 gene in correlation with colon and lung cancer

Sarcoendoplasmic reticulum calcium transport ATPases (SERCA-type calcium pumps), proteins that accumulate calcium in the endoplasmic reticulum, play an important role in numerous signaling pathways controlling tumor growth, differentiation, and cell death. Reports that Atp2a2 (Serca2) haploinsufficient mice often developed cancer prompted us to study the involvement of the ATP2A2 gene in human cancer development. We found 13 different novel alterations of the ATP2A2 gene in 27 of 416 alleles of patients with two different types of cancer. Changes in ATP2A2 were significantly more common in patients with colon cancer (P < 0.0001, odds ratio OR = 25.3) or lung cancer (P = 0.046, OR = 8.05). The 13 alterations were missense mutations (2), intronic deletions (2), intronic insertions (1), and single-nucleotide alterations (8: two in the coding region, three in the intronic region, and three in the promoter region). We detected lost or reduced expression of ATP2A2 in all patients with alterations in the promoter region, as well as in patients with a combination of gene alterations. Our results suggest that germline alterations of ATP2A2 may predispose to lung and colon cancer and that an impaired ATP2A2 gene might be involved, directly or indirectly, as an early event in carcinogenesis.

A calcium-based theory of carcinogenesis

Most human cancers are initiated by chronic injuries that repeatedly kill cells and must, therefore, repeatedly raise cell calcium within nearby survivors. They may also raise calcium in distant cells via calcium waves. Here it is argued that these calcium increases initiate oncogenesis by breaking gap junctions and thus disorganizing tissues and by activating proto-oncogenes. It is also argued that these calcium increases become self-perpetuating in part through the development of an ability of cells to divide in reduced extracellular calcium, i.e., habituation to reduced extracellular calcium. I propose to test these calcium-based theories by using aequorinated mice.

Accelerated chemically induced tumor development mediated by CD4+CD25+ regulatory T cells in wild-type hosts

We examined the role of CD4+CD25+ regulatory T cells in the development of 3-methylcholanthrene (MCA)-induced tumors. Immunization of wild-type BALB/c mice with a series of SEREX (serological identification of antigens by recombinant expression cloning)-defined broadly expressed self-antigens results in the development of highly active CD4+CD25+ regulatory T cells. Accelerated tumor development was observed in mice immunized with self-antigens and was abolished by antibody-mediated depletion of CD4+ T cells or CD25+ T cells. A similar acceleration of tumorigenesis was also observed in mice adoptively transferred 2 or 4 weeks after MCA injection with CD4+CD25+ T cells derived from mice immunized with DnaJ-like 2, one of these self-antigens. Experiments with Jalpha281-/- mice lacking invariant natural killer (iNK) T cells indicated that iNK T cells, known for their protective role in the development of MCA-induced tumors, were suppressed in immunized hosts. NK cells, also known to play a protective role in MCA induced-tumorigenesis, were also suppressed in mice immunized with serologically defined self-antigens in a CD4+CD25+ T cell-dependent manner. We propose that CD4+CD25+ regulatory T cells generated by immunization with these self-antigens enhance susceptibility to MCA induced-tumorigenesis by down-regulating iNK T and NK reactivity, and suggest that these observations provide direct evidence for the existence of cancer immunosurveillance in this system of chemical carcinogenesis.

Expression of endomembrane calcium pumps in colon and gastric cancer cells. Induction of SERCA3 expression during differentiation

Calcium mobilization from the endoplasmic reticulum (ER) into the cytosol is a key component of several signaling networks controlling tumor cell growth, differentiation, or apoptosis. Sarco/endoplasmic reticulum calcium transport ATPases (SERCA-type calcium pumps), enzymes that accumulate calcium in the ER, play an important role in these phenomena. We report that SERCA3 expression is significantly reduced or lost in colon carcinomas when compared with normal colonic epithelial cells, which express this enzyme at a high level. To study the involvement of SERCA enzymes in differentiation, in this work differentiation of colon and gastric cancer cell lines was initiated, and the change in the expression of SERCA isoenzymes as well as intracellular calcium levels were investigated. Treatment of the tumor cells with butyrate or other established differentiation inducing agents resulted in a marked and specific induction of the expression of SERCA3, whereas the expression of the ubiquitous SERCA2 enzymes did not change significantly or was reduced. A similar marked increase in SERCA3 expression was found during spontaneous differentiation of post-confluent Caco-2 cells, and this closely correlated with the induction of other known markers of differentiation. Analysis of the expression of the SERCA3 alternative splice isoforms revealed induction of all three known iso-SERCA3 variants (3a, 3b, and 3c). Butyrate treatment of the KATO-III gastric cancer cells led to higher resting cytosolic calcium concentrations and, in accordance with the lower calcium affinity of SERCA3, to diminished ER calcium content. These data taken together indicate a defect in SERCA3 expression in colon cancers as compared with normal colonic epithelium, show that the calcium homeostasis of the endoplasmic reticulum may be remodeled during cellular differentiation, and indicate that SERCA3 constitutes an interesting new differentiation marker that may prove useful for the analysis of the phenotype of gastrointestinal adenocarcinomas.