GADD45gamma: a new vitamin D-regulated gene that is antiproliferative in prostate cancer cells

The TRPV6 Calcium Channel and Its Relationship with Cancer

Transient receptor potential vanilloid-6 (TRPV6) is a cation channel belonging to the TRP superfamily, specifically the vanilloid subfamily, and is the sixth member of this subfamily. Its presence in the body is primarily limited to the skin, ovaries, kidney, testes, and digestive tract epithelium. The body maintains calcium homeostasis using the TRPV6 channel, which has a greater calcium selectivity than the other TRP channels. Several pieces of evidence suggest that it is upregulated in the advanced stages of thyroid, ovarian, breast, colon, and prostate cancers. The function of TRPV6 in regulating calcium signaling in cancer will be covered in this review, along with its potential applications as a cancer treatment target.

Vitamin D treatment induces in vitro and ex vivo transcriptomic changes indicating anti-tumor effects

Vitamin D deficiency is associated with risk of several common cancers, including colorectal cancer (CRC). Here we have utilized patient derived epithelial organoids (ex vivo) and CRC cell lines (in vitro) to show that calcitriol (1,25OHD) increased the expression of the CRC tumor suppressor gene, CDH1, at both the transcript and protein level. Whole genome expression analysis demonstrated significant differential expression of a further six genes after 1,25OHD treatment, including genes with established links to carcinogenesis GADD45, EFTUD1 and KIAA1199. Furthermore, gene ontologies relevant to carcinogenesis were enriched by 1,25OHD treatment (e.g., 'regulation of Wnt signaling pathway', 'regulation of cell death'), with common enriched processes across in vitro and ex vivo cultures including 'negative regulation of cell proliferation', 'regulation of cell migration' and 'regulation of cell differentiation'. Our results identify genes and pathways that are modifiable by calcitriol that have links to CRC tumorigenesis. Hence the findings provide potential mechanism to the epidemiological and clinical trial data indicating a causal association between vitamin D and CRC. We suggest there is strong rationale for further well-designed trials of vitamin D supplementation as a novel CRC chemopreventive and chemotherapeutic agent.

A Mouse Brain-based Multi-omics Integrative Approach Reveals Potential Blood Biomarkers for Ischemic Stroke

Stroke remains a leading cause of death and disability worldwide. Despite continuous advances, the identification of key molecular signatures in the hyper-acute phase of ischemic stroke is still a primary interest for translational research on stroke diagnosis, prognosis, and treatment. Data integration from high-throughput -omics techniques has become crucial to unraveling key interactions among different molecular elements in complex biological contexts, such as ischemic stroke. Thus, we used advanced data integration methods for a multi-level joint analysis of transcriptomics and proteomics data sets obtained from mouse brains at 2 h after cerebral ischemia. By modeling net-like correlation structures, we identified an integrated network of genes and proteins that are differentially expressed at a very early stage after stroke. We validated 10 of these deregulated elements in acute stroke, and changes in their expression pattern over time after cerebral ischemia were described. Of these, CLDN20, GADD45G, RGS2, BAG5, and CTNND2 were next evaluated as blood biomarkers of cerebral ischemia in mice and human blood samples, which were obtained from stroke patients and patients presenting stroke-mimicking conditions. Our findings indicate that CTNND2 levels in blood might potentially be useful for distinguishing ischemic strokes from stroke-mimicking conditions in the hyper-acute phase of the disease. Furthermore, circulating GADD45G content within the first 6 h after stroke could also play a key role in predicting poor outcomes in stroke patients. For the first time, we have used an integrative biostatistical approach to elucidate key molecules in the initial stages of stroke pathophysiology and highlight new notable molecules that might be further considered as blood biomarkers of ischemic stroke.

Vitamin D in Triple-Negative and BRCA1-Deficient Breast Cancer-Implications for Pathogenesis and Therapy

Several studies show that triple-negative breast cancer (TNBC) patients have the lowest vitamin D concentration among all breast cancer types, suggesting that this vitamin may induce a protective effect against TNBC. This effect of the active metabolite of vitamin D, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D), can be attributed to its potential to modulate proliferation, differentiation, apoptosis, inflammation, angiogenesis, invasion and metastasis and is supported by many in vitro and animal studies, but its exact mechanism is poorly known. In a fraction of TNBCs that harbor mutations that cause the loss of function of the DNA repair-associated breast cancer type 1 susceptibility (BRCA1) gene, 1,25(OH)2D may induce protective effects by activating its receptor and inactivating cathepsin L-mediated degradation of tumor protein P53 binding protein 1 (TP53BP1), preventing deficiency in DNA double-strand break repair and contributing to genome stability. Similar effects can be induced by the interaction of 1,25(OH)2D with proteins of the growth arrest and DNA damage-inducible 45 (GADD45) family. Further studies on TNBC cell lines with exact molecular characteristics and clinical trials with well-defined cases are needed to determine the mechanism of action of vitamin D in TNBC to assess its preventive and therapeutic potential.

GSK-J4-Mediated Transcriptomic Alterations in Differentiating Embryoid Bodies

Histone-modifying enzymes are key players in the field of cellular differentiation. Here, we used GSK-J4 to profile important target genes that are responsible for neural differentiation. Embryoid bodies were treated with retinoic acid (10 μM) to induce neural differentiation in the presence or absence of GSK-J4. To profile GSKJ4-target genes, we performed RNA sequencing for both normal and demethylase-inhibited cells. A total of 47 and 58 genes were up- and down-regulated, respectively, after GSK-J4 exposure at a log2-fold-change cut-off value of 1.2 (p-value < 0.05). Functional annotations of all of the differentially expressed genes revealed that a significant number of genes were associated with the suppression of cellular proliferation, cell cycle progression and induction of cell death. We also identified an enrichment of potent motifs in selected genes that were differentially expressed. Additionally, we listed upstream transcriptional regulators of all of the differentially expressed genes. Our data indicate that GSK-J4 affects cellular biology by inhibiting cellular proliferation through cell cycle suppression and induction of cell death. These findings will expand the current understanding of the biology of histone-modifying enzymes, thereby promoting further investigations to elucidate the underlying mechanisms.

1α,25-Dihydroxyvitamin D3 enhances TRPV6 transcription through p38 MAPK activation and GADD45 expression

The active form of vitamin D, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], acts as a ligand for the vitamin D receptor (VDR), and regulates various physiological processes, including calcium and bone metabolism, cellular growth and differentiation, immunity and cardiovascular function. A number of vitamin D derivatives have been synthesized for the treatment of cancer and inflammatory disease, but the adverse effect of hypercalcemic activity due to intestinal calcium absorption has limited wide clinical application. The VDR target gene product TRPV6 is essential for intestinal calcium absorption. Our prior study has demonstrated that 1,25(OH)₂D₃ induces TRPV6 mRNA expression at lower concentrations than for induction of CYP24A1, a VDR target gene involved in vitamin D inactivation, in intestinal SW480 cells, suggesting an additional mechanism for vitamin D signaling on TRPV6 induction. By searching for a signal transduction pathway involved in 1,25(OH)₂D₃-induced expression of TRPV6, we found that a p38 mitogen-activated protein kinase (MAPK) inhibitor reduces the expression of TRPV6 but not CYP24A1 in 1,25(OH)₂D₃-treated SW480 cells. Knockdown experiments showed that p38α is involved in 1,25(OH)₂D₃-induced expression of TRPV6 but not CYP24A1. Treatment with a de novo protein synthesis inhibitor suppressed 1,25(OH)₂D₃-induced TRPV6 expression. Finally, we found that 1,25(OH)₂D₃ treatment induced expression of GADD45A, which encodes the GADD45α MAPK kinase kinase activator, earlier than TRPV6 expression and that GADD45A knockdown reduced TRPV6 induction by 1,25(OH)₂D₃. These findings indicate that p38α and GADD45α are involved in an enhanced vitamin D signaling on TRPV6 expression.

Metformin Reduces Prostate Tumor Growth, in a Diet-Dependent Manner, by Modulating Multiple Signaling Pathways

Prostate-cancer is strongly influenced by obesity, wherein metformin could represent a promising treatment; however, the endocrine metabolic/cellular/molecular mechanisms underlying these associations and effects are still unclear. To determine the beneficial antitumoral effects of metformin on prostate cancer progression/aggressiveness and the relative contribution of high-fat diet (HFD; independently of obesity), we used HFD-fed immunosuppressed mice inoculated with PC3 cells (which exhibited partial resistance to diet-induced obesity) compared with low-fat diet (LFD)-fed control mice. Moreover, gene expression analysis was performed on cancer-associated genes in the xenografted tumors, and the antitumorigenic role of metformin on tumoral (PC3/22Rv1/LNCaP) and normal (RWPE1) prostate cells was evaluated. The results demonstrate that HFD is associated with enhanced prostate cancer growth irrespective of body weight gain and endocrine metabolic dysregulations and that metformin can reduce prostate cancer growth under LFD but more prominently under HFD, acting through the modulation of several tumoral-associated processes (e.g., cell cycle, apoptosis, and/or necrosis). Moreover, the actions observed in vivo could be mediated by the modulation of the local expression of GH/IGF1 axis components. Finally, it was demonstrated that metformin had disparate effects on proliferation, migration, and prostate-specific antigen secretion from different cell lines. Altogether, these data reveal that metformin inhibits prostate cancer growth under LFD and, specially, under HFD conditions through multiple metabolic/tumoral signaling pathways.Implications: The current study linking dietary influence on metformin-regulated signaling pathways and antitumoral response provides new and critical insight on environment-host interactions in cancer and therapy. Mol Cancer Res; 15(7); 862-74. ©2017 AACR.

Transcript Levels of Androgen Receptor Variant 7 and Ubiquitin-Conjugating Enzyme 2C in Hormone Sensitive Prostate Cancer and Castration-Resistant Prostate Cancer

PURPOSE

This study is designed to identify the androgen receptor variant 7 (AR-V7) status, clinical significance of AR-V7 in hormone sensitive prostate cancer (HSPC). Then, we evaluated AR-V7 and changes of its target gene, ubiquitin-conjugating enzyme E2C (UBE2C) which is an anaphase-promoting complex/cyclosome (APC/C)-specific ubiquitin-conjugating enzyme, in castration-resistant prostate cancer (CRPC) in serial tumor biopsies from patients receiving androgen deprivation therapy.

METHODS

We used RT-PCR and Q-PCR assay to evaluate AR-V7, androgen receptor full length (AR-FL), and UBE2C in tumor biopsies from patients with HSPC and CRPC. We examined associations between mRNA expression of AR-V7 and clinicopathologic factors. Furthermore, to identify other potential genes involved in the development of CRPC, RNA sequencing was conducted, using paired prostate cancer (PCa) tissues obtained immediately prior to treatment and at the time of therapeutic resistance.

RESULTS

A total of 13 HSPC patients and three CRPC patients were enrolled. Neither a high Gleason score (score of 8 and 9) nor a high risk of PCa (a high risk of locally advanced PCa according to NCCN guidelines) was correlated with mRNA expression of AR-V7 in HSPC (P = 0.153 and P = 0.215). The mRNA expression of AR-FL, but not AR-V7, was significantly associated with the mRNA expression of UBE2C level in HSPC (P = 0.007). However, increased expression of AR-V7, not AR-FL, paralleled increased expression of UBE2C in the CRPC specimens (P = 0.03). AR-V7 expression status before ADT was likely related to shorter CRPC development in patients treating ADT. The result of the RNA-sequencing analysis using serial samples from the same patient before and after castration demonstrated an increased level of the PI3K regulatory subunit 1 (P = 0.018).

CONCLUSION

Our study revealed the role of UBE2C as a marker of the androgen signaling pathway in PCa. Differential gene expression analysis using serial samples from the same patient before and after castration revealed potential genes and pathways involved in development of CRPC. Further studies are needed to determine whether these genes and pathways are potential therapeutic target for CRPC. Prostate 77:60-71, 2017. © 2016 Wiley Periodicals, Inc.

1,25 dihydroxyvitamin D3 inhibits the proliferation of thyroid cancer stem-like cells via cell cycle arrest

BACKGROUND

An anti-proliferative effect of vitamin D has been reported in different carcinomas, including thyroid cancer. Cancer stem cells (CSCs), a very small fraction of cancer cells, are widely believed to be responsible for cancer initiation, relapse and metastasis.

OBJECTIVES

We addressed the question as to whether CSCs derived from the anaplastic thyroid carcinoma cell lines SW1736, C643, HTh74 and its doxorubicin- resistant subline HTh74R are also a target of vitamin D action.

METHODS

The effect of calcitriol on growth of HTh74, HTh74R, SW1736 and C643 cell lines was investigated by cell viability assays. In stem-enriched cells derived from thyro-spheres cell cycle analysis and apoptotic assays were performed. Furthermore, the role of calcitriol in the formation of cancer thyro-spheres and its putative differentiation-inducing effect were analysed.

RESULTS

CSCs isolated as thyro-spheres from all the four anaplastic thyroid carcinoma cells expressed vitamin D receptors as did their parental cells. Calcitriol inhibited proliferation of anaplastic thyroid carcinoma cells with a more pronounced effect on doxorubicin-resistant HTh74R cells, and it significantly reduced the capacity to form stem cell-derived spheres and decreased the size of these spheres that consist of CSCs and their progenitor cells. As revealed by cell cycle analysis, calcitriol induced G2/M phase arrest in thyro-sphere cells derived cells from HTh74, HTh74R and C643 but did not affect apoptosis. Finally, calcitriol altered morphology of CSCs.

CONCLUSION

Calcitriol inhibited the growth of CSCs derived from anaplastic thyroid cancer cells. It may also exert a pro-differentiation effect in thyroid CSCs.

Integration of genome-wide of Stat3 binding and epigenetic modification mapping with transcriptome reveals novel Stat3 target genes in glioma cells

BACKGROUND

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in many human tumors, including gliomas, and regulates the expression of genes implicated in proliferation, survival, apoptosis, angiogenesis and immune regulation. Only a small fraction of those genes has been proven to be direct STAT3 targets. In gliomas, STAT3 can play tumor suppressive or oncogenic roles depending on the tumor genetic background with target genes being largely unknown.

RESULTS

We used chromatin immunoprecipitation, promoter microarrays and deep sequencing to assess the genome-wide occupancy of phospho (p)-Stat3 and epigenetic modifications of H3K4me3 and H3ac in C6 glioma cells. This combined assessment identified a list of 1200 genes whose promoters have both Stat3 binding sites and epigenetic marks characteristic for actively transcribed genes. The Stat3 and histone markings data were also intersected with a set of microarray data from C6 glioma cells after inhibition of Jak2/Stat3 signaling. Subsequently, we found 284 genes characterized by p-Stat3 occupancy, activating histone marks and transcriptional changes. Novel genes were screened for their potential involvement in oncogenesis, and the most interesting hits were verified by ChIP-PCR and STAT3 knockdown in human glioma cells.

CONCLUSIONS

Non-random association between silent genes, histone marks and p-Stat3 binding near transcription start sites was observed, consistent with its repressive role in transcriptional regulation of target genes in glioma cells with specific genetic background.

Mechanism of androgen receptor corepression by CKβBP2/CRIF1, a multifunctional transcription factor coregulator expressed in prostate cancer

The transcription factor coregulator Casein kinase IIβ-binding protein 2 or CR6-interacting factor 1 (CKβBP2/CRIF1) binds the androgen receptor (AR) in prostate cancer cells and in response to dihydrotestosterone localizes with AR on the prostate-specific antigen gene enhancer, but does not bind DNA suggesting CKβBP2/CRIF1 localization in chromatin is determined by AR. In this study we show also that CKβBP2/CRIF1 inhibits wild-type AR and AR N-terminal transcriptional activity, binds to the AR C-terminal region, inhibits interaction of the AR N- and C-terminal domains (N/C interaction) and competes with p160 coactivator binding to the AR C-terminal domain, suggesting CKβBP2/CRIF1 interferes with AR activation functions 1 and 2. CKβBP2/CRIF1 is expressed mainly in stromal cells of benign prostatic hyperplasia and in stroma and epithelium of prostate cancer. CKβBP2/CRIF1 protein is increased in epithelium of androgen-dependent prostate cancer compared to benign prostatic hyperplasia and decreased slightly in castration recurrent epithelium compared to androgen-dependent prostate cancer. The multifunctional CKβBP2/CRIF1 is a STAT3 interacting protein and reported to be a coactivator of STAT3. CKβBP2/CRIF1 is expressed with STAT3 in prostate cancer where STAT3 may help to offset the AR repressor effect of CKβBP2/CRIF1 and allow AR regulation of prostate cancer growth.

Does vitamin D protect against DNA damage?

Vitamin D is a secosteroid best known for its role in maintaining bone and muscle health. Adequate levels of vitamin D may also be beneficial in maintaining DNA integrity. This role of vitamin D can be divided into a primary function that prevents damage from DNA and a secondary function that regulates the growth rate of cells. The potential for vitamin D to reduce oxidative damage to DNA in a human has been suggested by clinical trial where vitamin D supplementation reduced 8-hydroxy-2'-deoxyguanosine, a marker of oxidative damage, in colorectal epithelial crypt cells. Studies in animal models and in different cell types have also shown marked reduction in oxidative stress damage and chromosomal aberrations, prevention of telomere shortening and inhibition of telomerase activity following treatment with vitamin D. The secondary function of vitamin D in preventing DNA damage includes regulation of the poly-ADP-ribose polymerase activity in the DNA damage response pathway involved in the detection of DNA lesions. It is also able to regulate the cell cycle to prevent the propagation of damaged DNA, and to regulate apoptosis to promote cell death. Vitamin D may contribute to prevention of human colorectal cancer, though there is little evidence to suggest that prevention of DNA damage mediates this effect, if real. Very limited human data mean that the intake of vitamin D required to minimise DNA damage remains uncertain.

Correlation of somatic mutation and expression identifies genes important in human glioblastoma progression and survival

Cooperative dysregulation of gene sequence and expression may contribute to cancer formation and progression. The Cancer Genome Atlas (TCGA) Network recently catalogued gene sequence and expression data for a collection of glioblastoma multiforme (GBM) tumors. We developed an automated, model-free method to rapidly and exhaustively examine the correlation among somatic mutation and gene expression and interrogated 149 GBM tumor samples from the TCGA. The method identified 41 genes whose mutation status is highly correlated with drastic changes in the expression (z-score ± 2.0), across tumor samples, of other genes. Some of the 41 genes have been previously implicated in GBM pathogenesis (e.g., NF1, TP53, RB1, and IDH1) and others, while implicated in cancer, had not previously been highlighted in studies using TCGA data (e.g., SYNE1, KLF6, FGFR4, and EPHB4). The method also predicted that known oncogenes and tumor suppressors participate in GBM via drastic over- and underexpression, respectively. In addition, the method identified a known synthetic lethal interaction between TP53 and PLK1, other potential synthetic lethal interactions with TP53, and correlations between IDH1 mutation status and the overexpression of known GBM survival genes.

Vitamin d, sunlight and prostate cancer risk

Prostate cancer is the second common cancer in men worldwide. The prevention of prostate cancer remains a challenge to researchers and clinicians. Here, we review the relationship of vitamin D and sunlight to prostate cancer risk. Ultraviolet radiation of the sunlight is the main stimulator for vitamin D production in humans. Vitamin D's antiprostate cancer activities may be involved in the actions through the pathways mediated by vitamin D metabolites, vitamin D metabolizing enzymes, vitamin D receptor (VDR), and VDR-regulated genes. Although laboratory studies including the use of animal models have shown that vitamin D has antiprostate cancer properties, whether it can effectively prevent the development and/or progression of prostate cancer in humans remains to be inconclusive and an intensively studied subject. This review will provide up-to-date information regarding the recent outcomes of laboratory and epidemiology studies on the effects of vitamin D on prostate cancer prevention.