Overexpression of regucalcin suppresses cell proliferation in cloned rat hepatoma H4-II-E cells: Involvement of intracellular signaling factors and cell cycle-related genes

The inflammatory macrophages repress the growth of bone metastatic human prostate cancer cells via TNF-α and IL-6 signaling: Involvement of cell signaling regulator regucalcin

Macrophages in the cancer microenvironments may play a regulatory role in the progression and metastasis of prostate cancer cells. However, the crosstalk between macrophages and prostate cancer cells is poorly understood. This study elucidates whether inflammatory macrophages regulate the proliferation and death of human prostate cancer cells in vitro. The RAW264.7 mouse macrophages were cocultured with PC-3 or DU-145 wild-type cells by using a Transwell chamber in vitro. RAW264.7 cells were cocultured with PC-3 or DU-145 cells in the presence of lipopolysaccharide (LPS). This coculturing blocked the proliferation and accelerated the death of cancer cells. Interestingly, cancer cell proliferation was repressed and death was promoted by the addition of the conditioned medium obtained from RAW264.7 cells treated with LPS. Culturing with LPS mostly augmented the production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the culture medium of RAW264.7 cells. The effects of the conditioned medium on the proliferation and death of PC-3 or DU-145 cells were blocked by NF-κB or STAT3 signaling inhibitors. Moreover, the effects of the conditioned medium on the proliferation and death of prostate cancer cells were not expressed in regucalcin-overexpressing cancer cells that diminish the levels of NF-κB p65 and STAT3. Culturing with extracellular TNF-α, IL-6, or regucalcin triggered inhibition of the proliferation of PC-3 wild-type cells. The levels of regucalcin in PC-3 cells were elevated by TNF-α or IL-6 stimulation. This study demonstrates that inflammatory macrophages triggered the loss of prostate cancer cells via the signaling process of NF-κB, STAT3, or regucalcin.

The overexpressed transcription factor RGPR-p117 suppresses the proliferation of normal rat kidney proximal tubular epithelial NRK-52E cells: Involvement of diverse signaling pathways

AIMS

RGPR-p117 was originally discovered as a novel transcription factor, which specifically binds to a nuclear factor I (NFI) consensus motif TTGGC(N)₆CC in the promoter region of the regucalcin gene. RGPR-p117 is also called as Lztr2 and SEC16B. The role of RGPR-p117 in cell regulation is poorly understood. This study was undertaken to determine whether the overexpression of RGPR-p117 impacts the proliferation of normal rat kidney proximal tubular epithelial NRK-52E cells in vitro.

MAIN METHODS

The NRK-52E wild-type cells and RGPR-p117-overexpressing NRK-52E cells were cultured in DMEM containing fetal bovine serum.

KEY FINDINGS

The overexpression of RGPR-p117 repressed colony formation and proliferation of NRK-52E cells. Interestingly, RGPR-p117 overexpression blocked cell proliferation promoted by culturing with Bay K 8644, a calcium-entry agonist, and phorbol 12-myristate 13-acetate, an activator of protein kinase C. The depressive effects of RGPR-p117 overexpression on cell proliferation were not occurred by culturing with various inhibitors of cell cycle and intracellular signaling processes. RGPR-p117 overexpression increased the translocation of RGPR-p117 into the nucleus of NRK-52E cells. Mechanistically, RGPR-p117 overexpression diminished the levels of Ras, PI3 kinase, Akt, mitogen-activated protein kinase, and mTOR, while it raised the levels of p53, Rb, p21, and regucalcin. Furthermore, RGPR-p117 overexpression protected cell death caused by apoptosis-inducing factors, suggesting that the suppressive effects of RGPR-p117 on cell growth are independent of cell death.

SIGNIFICANCE

The present study demonstrates that the overexpressed transcription factor RGPR-p117 suppresses cell proliferation via targeting diverse signaling processes, suggesting a role of RGPR-p117 in cell regulation.

Overexpression of regucalcin blocks the migration, invasion, and bone metastatic activity of human prostate cancer cells: Crosstalk between cancer cells and bone cells

BACKGROUND

Prostate cancer is a bone metastatic cancer and is the second leading cause of cancer-related death in men. Prolonged progression-free survival of prostate cancer patients is associated with high regucalcin expression in the tumor tissues. This study investigates the underlying mechanism by which regucalcin prevents bone metastatic activity of prostate cancer cells.

METHODS

Human prostate cancer PC-3 or DU-145 wild-type cells or regucalcin-overexpressing PC-3 or DU-145 cells (transfectants) were cultured in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum.

RESULTS

Overexpressed regucalcin suppressed the migration and invasion of bone metastatic human prostate cancer cells in vitro, and it reduced the levels of key proteins in metastasis including Ras, Akt, MAPK, RSK-2, mTOR, caveolin-1, and integrin β1. Invasion of prostate cancer cells was promoted by coculturing with preosteoblastic MC3T3-E1 or preosteoclastic RAW264.7 cells. Coculturing with cancer cells and bone cells repressed the growth of preosteoblastic cells and enhanced osteoclastogenesis of preosteoclastic cells, and these alterations were caused by a conditioned medium from cancer cell culture. Disordered differentiation of bone cells was prevented by regucalcin overexpression. Production of tumor necrosis factor-α (TNF-α) in cancer cells was blocked by overexpressed regucalcin. Of note, the effects of conditioned medium on bone cells were prevented by NF-κB inhibitor. TNF-α may be important as a mediator in the crosstalk between cancer cells and bone cells.

CONCLUSION

Overexpression of regucalcin suppressed the migration, invasion, and bone metastatic activity of human prostate cancer cells. This study may provide a new strategy for therapy with the regucalcin gene transfer.

The marine factor 3,5-dihydroxy-4-methoxybenzyl alcohol suppresses growth, migration and invasion and stimulates death of metastatic human prostate cancer cells: targeting diverse signaling processes

Prostate cancer is metastatic cancer and is the second leading cause of cancer-related death in men. It is needed to develop more effective treatment for metastatic prostate cancer. The present study investigates whether the novel factor 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA), which was isolated from marine oyster, suppresses the activity of metastatic human prostate cancer PC-3 or DU-145 cells. Culture of DHMBA (1 or 10 µM) suppressed colony formation and growth of PC-3 or DU-145 cells in vitro. Suppressive effects of DHMBA on cell proliferation were not occurred by culturing with intracellular signaling inhibitors. Mechanistically, DHMBA (10 µM) reduced the levels of key proteins linked to promotion of cell growth, including Ras, PI3K, Akt, MAPK, and mTOR in PC-3 cells. Interestingly, DHMBA increased the levels of cancer suppressor p53, p21, Rb, and regucalcin. Moreover, culture of DHMBA simulated the death of PC-3 and DU-145 cells. This effect was implicated to caspase-3 activation in cells. Interestingly, the effects of DHMBA on cell proliferation and death were blocked by culturing with an inhibitor of aryl hydrocarbon receptor linked to transcriptional regulation. Furthermore, culture of DHMBA inhibited production of reactive oxygen species in PC-3 or DU-145 cells. Of note, DHMBA blocked migration and invasion by diminishing their related protein levels, including NF-κB 65, caveolin-1 and integrin β1. The novel marine factor DHMBA was demonstrated to suppress metastatic prostate cancer cells via targeting diverse signaling pathways. This study may provide a new strategy for prostate cancer therapy with DHMBA.

The phytochemical p-hydroxycinnamic acid suppresses the growth and stimulates the death in human liver cancer HepG2 cells

Hepatocellular carcinoma (HCC) is one of the most prevalent malignant diseases and causes a third of cancer-related death. The prognosis and effective treatment of advanced HCC remains poor in spite of the development of novel therapeutic strategies. In the present study, we investigate anticancer effects of the botanical molecule p-hydroxycinnamic  acid (HCA) in the HepG2 liver cancer model in vitro. Culturing with HCA (10-1000 nM) suppressed colony formation and growth of HepG2 cells. Mechanistically, culturing with HCA decreased levels of Ras, PI3K, Akt, MAPK, NF-κB p65 and β-catenin, which are linked to processes of cell signaling and transcription, and increased levels of retinoblastoma and regucalcin, which are suppressors for carcinogenesis. These alterations may lead to the suppression of cell growth. Furthermore, culturing with HCA (10-1000 nM) stimulated cell death due to increased caspase-3 levels. Interestingly, the effects of HCA on the growth and death of HepG2 cells were inhibited by culturing with CH223191, an antagonist of aryl hydrocarbon receptor (AHR), suggesting that the flavonoid effects are, at least partly, mediated by activation of AHR signaling. Notably, HCA blocked stimulatory effects of Bay K 8644, an agonist of L-type calcium channel, on the growth of HepG2 cells. Thus, our study demonstrates that HCA suppresses the growth and stimulates the death of human liver cancer HepG2 cells in vitro. The botanical molecule HCA may therefore be a useful tool in the treatment of HCC, providing a novel strategy for the therapy of human liver cancers.

Progression-free survival of prostate cancer patients is prolonged with a higher regucalcin expression in the tumor tissues: Overexpressed regucalcin suppresses the growth and bone activity in human prostate cancer cells

Prostate cancer, which is a bone metastatic cancer, is the second leading cause of cancer-related death in men. There is no effective treatment for metastatic prostate cancer. Regucalcin has been shown to contribute as a suppressor in various types of human cancers. In the present study, furthermore, we investigate an involvement of regucalcin in suppression of prostate cancer. Regucalcin expression was compared in 131 primary tumor tissues and 19 metastatic tumor tissues in prostate cancer patients. Regucalcin expression in the metastatic tumor was found to be reduced as compared with that in primary tumor. The progression-free survival rate was prolonged in patients with a higher regucalcin expression. Translationally, overexpression of regucalcin in bone metastatic human prostate cancer PC-3 and DU-145 cells suppressed colony formation and cell growth in vitro. Mechanistically, overexpressed regucalcin enhanced the levels of p53, Rb, and p21, and decreased the levels of Ras, PI3 kinase, Akt, and mitogen-activated protein kinase, leading to suppression of cell growth. Furthermore, higher regucalcin expression suppressed the levels of nuclear factor-κB p65, β-catenin, and signal transducer and activator of transcription 3, which regulate a transcription activity. Cell growth was promoted by culturing with the calcium agonist Bay K 8644. This effect was blocked by overexpression of regucalcin. Notably, overexpressed regucalcin suppressed bone metastatic activity of PC-3 and DU-145 cells when cocultured with preosteoblastic or preosteoclastic cells. Regucalcin may suppress the development of human prostate cancer, suggesting that gene delivery systems in which its expression is forced may be a novel therapeutic strategy.

An aryl hydrocarbon receptor agonist suppresses the growth of human umbilical vein endothelial cells in vitro: Potent effect with polyunsaturated fatty acids

Human umbilical vein endothelial cells (HUVECs) are a pivotal component of the hematopoietic microenvironment linked to the modulation of the immune response, inflammation and carcinogenesis. HUVEC expresses the aryl hydrocarbon receptor (AHR), which regulates gene expression by binding to the xenobiotic-responsive element. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent agonist for AHR signalling. Treatment with TCDD (0.1-100 nmol/L) was found to suppress the proliferation and to stimulate the death of HUVEC. TCDD's effects were abolished by culturing with CH223191, an inhibitor of AHR signalling. Mechanistically, TCDD treatment increased the protein levels of cell growth suppressors, including p53, Rb, p21 and regucalcin, and caspase-3 implicated in apoptotic cell death, and decreased the levels of Stat3, mitogen-activated protein kinase (MAPK/Erk1/2) and phospho-MAPK/Erk1/2. Treatment with polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid, eicosapentaenoic acid and arachidonic acid, suppressed the proliferation and stimulated the death of HUVEC in vitro, and decreased the levels of Stat3, MAPK/Erk1/2 and phospho-MAPK/Erk1/2 and increased caspase-3. Notably, the effects of TCDD in suppressing proliferation and stimulating death of HUVEC were modulated by coculturing with PUFAs. These effects were reversed by treatment with CH223191, an inhibitor of AHR. Treatment with both TCDD and PUFAs collaboratively enhanced the levels of AHR, CYP1A1, p53, p21, Rb and regucalcin. Moreover, TCDD suppressed migration with wound healing of HUVEC. Notably, the combination of TCDD and PUFAs revealed potent suppressive effects on angiogenesis of HUVEC, potentially related to disorders of the stromal microenvironment.

The calcium channel agonist Bay K 8644 promotes the growth of human liver cancer HepG2 cells in vitro: suppression with overexpressed regucalcin

Hepatocellular carcinoma is one of the most prevalent malignant diseases and causes a third of cancer-related death. The consequences of altered calcium homeostasis in cancer cells may contribute to tumor progression. Regucalcin plays an inhibitory role in calcium signaling linked to transcription regulation. Regucalcin gene expression is downregulated in the tumor tissues of liver cancer patients, suggesting an involvement as a suppressor in hepatocarcinogenesis. We investigated whether Bay K 8644, an agonist of the L-type Ca2+ channel, promotes the growth of human liver cancer and if the effect of Bay K 8644 is suppressed by overexpressed regucalcin using the HepG2 cell model. The colony formation and growth of HepG2 cells were promoted by culturing with Bay K 8644 (0.1-10 nM). This effect was suppressed by inhibitors of signaling processes linked to cell proliferation, including PD98059 and wortmannin. Death of HepG2 cells was stimulated by Bay K 8644 with higher concentrations (25 and 100 nM). The effects of Bay K 8644 on cell growth and death were abolished by verapamil, an antagonist of calcium channel. Mechanistically, culturing with Bay K 8644 increased levels of mitogen-activated protein kinase (MAPK) and phospho-MAPK. Notably, overexpressed regucalcin suppressed Bay K 8644-promoted growth and death of HepG2 cells. Furthermore, overexpressed regucalcin prevented growth and increased death induced by thapsigargin, which induces the release of intracellular stored calcium. Thus, higher regucalcin expression suppresses calcium signaling linked to the growth of liver cancer cells, providing a novel strategy in treatment of hepatocellular carcinoma with delivery of the regucalcin gene.

Exogenous regucalcin negatively regulates the progression of cervical adenocarcinoma

Cervical adenocarcinoma (CA) is a type of cervical cancer, and in previous decades its incidence has steadily increased. The upregulation of regucalcin (RGN) in various tumor cell types inhibits the progression of cancer. To understand the role of RGN in CA, RGN expression in human cervical cancer compared with normal tissues was analyzed using The Cancer Genome Atlas database (TCGA). Subsequently, transfection of lentivirus-mediated RGN into HeLa cells was conducted to study its function in tumor proliferation and metastasis. The expression of RGN and proteins associated with the Wnt/β-catenin signaling pathway and epithelial-mesenchymal transition (EMT) were determined using reverse transcription-quantitative polymerase chain reaction and western blotting. Cell migration and invasion were evaluated using Transwell assays. Furthermore, cell proliferation, colony formation and cell cycle were assessed using the Cell Counting Kit-8, colony formation assay and flow cytometry, respectively. Lentivirus-mediated RGN effectively upregulated RGN expression, inhibited cell proliferation, retarded cellular invasion and promoted cell cycle arrest at the G₂/M phase in HeLa cells. In addition, the expression levels of β-catenin, p-glycogen synthase kinase (GSK)-3β, matrix metalloproteinase (MMP)-3, MMP-7 and MMP-9 were effectively decreased, whilst those of E-cadherin and GSK-3β were increased. The results suggest that RGN may be an inhibitory factor in tumorigenesis, and its mechanism of inhibiting tumor proliferation and metastasis may be associated with Wnt/β-catenin signaling and EMT.

The combination of catechin, baicalin and β-caryophyllene potentially suppresses the production of inflammatory cytokines in mouse macrophages in vitro

It has been demonstrated that the combination of three botanical factors of (+)-catechin, baicalin and β-caryophyllene, which exhibit anti-inflammatory effects, with comparatively lower concentrations of each factor, demonstrating a potent synergistic-suppressive effect on the growth of mouse macrophage RAW264.7 cells in vitro, and suggesting it may function as a pharmacologic tool for managing inflammatory diseases. The present study was undertaken to determine the suppressive effects of (+)-catechin, baicalin or β-caryophyllene on the production of inflammatory cytokines, including TNF-α, IL-6 and IL-1β, which was enhanced by lipopolysaccharide (LPS) in RAW264.7 cells in vitro. The cells were cultured for 3 days without botanical factors, followed by incubation for 5 h in the presence of either vehicle, (+)-catechin [1 µg/ml (3.45 µM)], baicalin [1 µg/ml (2.24 µM)], or β-caryophyllene [1 µg/ml (5 µM)] with or without LPS (100 ng/ml); this did not have significant effects on the number of RAW264.7 cells. The production of TNF-α, IL-6 and IL-1β was not altered by the addition of (+)-catechin, baicalin, β-caryophyllene, or the three combined factors in RAW264.7 cells without LPS. LPS treatment caused a marked production of TNF-α, IL-6, and IL-1β. This enhancement was suppressed by the addition of (+)-catechin, baicalin or β-caryophyllene. Of note, the production of these cytokines was additively suppressed by the combination of the three factors in macrophages. Thus, the combination of (+)-catechin, baicalin and β-caryophyllene was found to reveal a potent suppressive effect on cytokine production in macrophages in vitro. This composition may be a useful tool as a potent anti-inflammatory agent.

2,3,7,8‑tetrachlorodibenzo‑p‑dioxin suppresses the growth of human colorectal cancer cells in vitro: Implication of the aryl hydrocarbon receptor signaling

Human colorectal cancer is the third most common cancer disease with a 5‑year survival rate of 55% in USA in 2016. The investigation to identify novel biomarker factors with molecular classification may provide notable clinical information to prolong the survival of patients with colorectal cancer. The aryl hydrocarbon receptor (AHR) binds the AHR nuclear translocator in the cytoplasm of various types of cells, including liver cells, and then binds to the xenobiotic responsive element on various genes. AHR was initially discovered via its ligand, the polychlorinated hydrocarbon, 2,3,7,8‑tetrachlorodibenzo‑p‑dioxin (TCDD). The present study was undertaken to determine whether TCDD, an agonist of AHR signaling, impacts the growth of RKO human colorectal cancer cells in vitro. Treatment with TCDD (0.1‑100 nM) revealed suppressive effects on colony formation and proliferation of RKO cells, and stimulated death of these cells with subconfluence. These effects of TCDD were abolished by pretreatment with CH223191, an inhibitor of AHR signaling. Western blot analysis demonstrated that TCDD treatment decreased AHR levels and elevated cytochrome P450 family 1 subfamily A member 1 (CYP1A1) levels, indicating a stimulation of AHR signaling. TCDD treatment caused an increase in nuclear factor‑κB p65 and β‑catenin levels, although it did not have an effect on Ras levels. Notably, TCDD treatment increased the levels of p53, retinoblastoma, p21 and regucalcin, which are depressors of carcinogenesis. Additionally, action of TCDD on cell proliferation and death were not revealed in regucalcin‑overexpressing RKO cells, and regucalcin overexpression depressed AHR signaling associated with CYP1A1 expression. Thus, AHR signaling suppresses the growth of colorectal cancer cells, indicating a role as a significant targeting molecule for colorectal cancer.

Prolonged survival of renal cancer patients is concomitant with a higher regucalcin gene expression in tumor tissues: Overexpression of regucalcin suppresses the growth of human renal cell carcinoma cells in vitro

Renal cell carcinoma (RCC), which is a type of cancer found in the kidney tubule, is among the 10 most frequently occurring human cancers. Regucalcin plays a potential role as a regulator of transcriptional activity, and its downregulated expression or activity may contribute to the promotion of human cancers. In this study, we investigated the involvement of regucalcin in human RCC. Regucalcin expression was compared in 23 normal and 29 tumor samples of kidney cortex tissues of patients with clear cell RCC obtained through the Gene Expression Omnibus (GEO) database (GSE36895). Regucalcin expression was downregulated in the tumor tissues. The prolonged survival of patients with clear cell RCC was demonstrated to be associated with a higher regucalcin gene expression in the TCGA dataset. The overexpression of regucalcin suppressed the colony formation, proliferation and the death of human clear cell RCC A498 cells in vitro. Mechanistically, the overexpression of regucalcin induced the G1 and G2/M phase cell cycle arrest of A498 cells through the suppression of multiple signaling components, including Ras, PI3 kinase, Akt and mitogen‑activated protein (MAP) kinase. Importantly, the overexpression of regucalcin led to an elevation in the levels of the tumor suppressors, p53, Rb and the cell cycle inhibitor, p21. The levels of the transcription factors, c‑fos, c‑jun, nuclear factor‑κB p65, β‑catenin and signal transducer and activator of transcription 3, were suppressed by regucalcin overexpression. On the whole, the findings of this study suggest that regucalcin plays a suppressive role in the promotion of human RCC. The overexpression of regucalcin by gene delivery systems may thus prove to be a novel therapeutic strategy for RCC.

2,3,7,8‑Tetrachlorodibenzo‑p‑dioxin suppresses the growth of human liver cancer HepG2 cells in vitro: Involvement of cell signaling factors

The aryl hydrocarbon receptor (AHR) is transcriptionally active in the form of a heterodimer with the AHR nuclear translocator, which then binds to the xenobiotic responsive element. AHR was originally discovered via its ligand, the polychlorinated hydrocarbon, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In this study, we investigated whether TCDD regulates the growth of human liver cancer HepG2 cells in vitro. TCDD (0.1–100 nM) was found to exert suppressive effects on the colony formation and proliferation of HepG2 cells, and stimulatory effects on the death of HepG2 cells when the cells reached subconfluence. The effects of TCDD on the HepG2 cells were abolished by culture with CH223191, an inhibitor of AHR signaling. The effects of TCDD were dependent on the concentration of serum, which contains various signaling factors. The effects of TCDD were not potentiated by culture with tumor necrosis factor-α, which activates the signaling of nuclear factor-κB (NF-κB). The results of western blot analysis revealed that TCDD increased the protein levels of p53, Rb, p21, and regucalcin, which are suppressors of the growth of tumor cells. Moreover, TCDD enhanced the NF-κB p65, β-catenin, signal transducer and activator of transcription 3 (STAT3), Ras and Akt levels. Thus, the findings of this study indicate that TCDD may suppress liver cancer cell growth through various signaling pathways, mediated by AHR and its-related co-factors. Of note, the effects of TCDD were found to be potentiated by gemcitabine, which induces nuclear DNA damage in cancer cells, suggesting that their combined use may have potential as a suppressor of tumor cell growth.

Prolonged survival of patients with colorectal cancer is associated with a higher regucalcin gene expression: Overexpression of regucalcin suppresses the growth of human colorectal carcinoma cells in vitro

Regucalcin plays a crucial role as a regulator of transcriptional signaling activity, and its decreased expression or activity may contribute to the promotion of human carcinogenesis. A higher regucalcin expression in the tumor tissues has been demonstrated to prolong the survival of patients with various types of cancer, including pancreatic cancer, breast cancer, liver cancer and lung adenocarcinoma. The involvement of regucalcin in human colorectal cancer was investigated in the current study. Regucalcin gene expression and the survival data of 62 patients with colorectal cancer were obtained though the Gene Expression Omnibus (GEO) database (GSE12945) for outcome analysis. The data of gene expression revealed that the prolonged survival of patients with colorectal cancer was associated with a higher regucalcin gene expression in tumor tissues. The overexpression of regucalcin suppressed colony formation and proliferation, and induced the death of human colorectal carcinoma RKO cells cultured in a medium containing fetal bovine serum in vitro. Mechanistically, the overexpression of regucalcin induced the G1 and G2/M phase cell cycle arrest of the RKO cells through the suppression of multiple signaling pathways, including Ras, Akt, mitogen-activated protein (MAP) kinase and SAPK/JNK. Of note, the overexpression of regucalcin induced an increase in the levels of the tumor suppressors, p53 and Rb, and the cell cycle inhibitor, p21. Moreover, the levels of the transcription factors, c‑fos, c‑jun, nuclear factor (NF)‑κB p65, β-catenin and signal transducer and activator of transcription 3 (Stat3), were suppressed by the overexpression of regucalcin. On the whole, the findings of this study suggest that regucalcin plays a crucial role as a suppressor in human colorectal cancer, and that the suppressed expression of the regucalcin gene may predispose patients to the promotion of colorectal cancer. The overexpression of regucalcin by gene delivery may thus prove to be a novel therapeutic strategy for colorectal cancer.

Downregulation of SMP30 in senescent human lens epithelial cells

Senescence marker protein 30 (SMP30) has been reported to serve antiapoptotic and antioxidant roles, as well as roles in Ca²⁺ regulation, and may be involved in the occurrence and development of cataract. The present study aimed to investigate the expression of SMP30 in senescent human lens epithelial cells (HLECs) and explored the relationship between SMP30 and aging. SRA01/04 cells, a HLEC line, were treated with H₂O₂ to mimic aging, and cell morphological changes were observed by microscopy and cell activity was examined by MTT assay, senescence-associated-β-galactosidase (SA-β-Gal) staining and cell cycle analysis. The expression of SMP30 mRNA and protein was measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Following prolonged low-dose H₂O₂ exposure, cells exhibited senescence-related morphological changes, reduced growth activity, increased SA-β-Gal positive staining and cell cycle arrest in the S and G2/M phases. SMP30 mRNA expression levels were significantly downregulated following exposure to 75 and 100 µM H₂O₂, and the protein expression levels in the same groups were decreased by >6-fold compared with the control untreated cells. However, no significant change was observed in SMP30 expression in the 25 and 50 µM H₂O₂ exposure groups. These results suggest that, in the early stage of senescence induced by H₂O₂-mediated chronic oxidative stress, there may be no significant change in SMP30 expression, but when the oxidative stress increases and senescence is aggravated, SMP30 may be significantly downregulated in the senescent HLECs. The present study indicates that SMP30 may be an important factor involved in the aging process of HLECs and the development of cataract.

Combination of alendronate and genistein synergistically suppresses osteoclastic differentiation of RAW267.4 cells in vitro

Bone is a dynamic tissue that undergoes constant remodeling, with removal by osteoclastic bone resorption and replacement via osteoblastic bone formation and mineralization. Deterioration of bone mass with aging leads to osteoporosis. Bisphosphonates are potent inhibitors of osteoclastic bone resorption. Genistein, an isoflavone, exerts a bone anabolic effect by suppressing osteoclastic bone resorption and stimulating osteoblastic bone formation. The present study was undertaken to investigate the anabolic effects of a combination of alendronate and genistein on osteoclastic differentiation. Preosteoclastic RAW267.4 cells were cultured with alendronate (0.1-100 µM) and/or genistein (0.1-100 µM) in vitro. Alendronate or genistein alone had no significant effect on the proliferation and death of RAW267.4 cells. Notably, the combination of the two agents was found to potently and synergistically repress the proliferation and death of RAW267.4 cells. Moreover, alendronate or genistein used separately at higher concentrations suppressed the osteoclastic differentiation of RAW267.4 cells induced by receptor activator of nuclear factor-κB ligand (RANKL) in vitro. However, combinations of the two agents (0.1-100 µM) synergistically suppressed the RANKL-induced osteoclastic differentiation. In conclusion, bisphosphonate and genistein combination therapy may provide a novel strategy for the prevention and treatment of osteoclastic bone resorption.

Survival of lung cancer patients is prolonged with higher regucalcin gene expression: suppressed proliferation of lung adenocarcinoma A549 cells in vitro

Regucalcin plays a crucial role as a suppressor of transcription signaling, and its diminished expression or activity may play a key role in human carcinogenesis. Higher regucalcin expression has been demonstrated to prolong survival of the patients of pancreatic cancer, breast cancer, and hepatocellular carcinoma. Moreover, we investigated an involvement of regucalcin in human lung cancer. Human non-small cell lung cancer (NSCLC) accounts for over 80% in human lung cancer and is one of the leading causes of malignancy-related mortality with fewer than 16% patients surviving beyond 5 years. In this study, gene expression and survival data of 204 lung adenocarcinoma patients were obtained through the gene expression omnibus database (GSE31210) for outcome analysis. Gene expression data demonstrated that prolonged survival in lung cancer patients is associated with higher regucalcin gene expression. Overexpression of regucalcin suppressed the proliferation, cell death, and migration of human lung adenocarcinoma NSCLC A549 cells in vitro. Mechanistically, regucalcin induced G1 and G2/M phase cell cycle arrest of A549 cells through suppression of multiple signaling pathways including Ras, Akt, MAP kinase, and SAPK/JNK. Moreover, overexpression of regucalcin caused decreases in the oncogenes c-fos and c-myc and elevation of the tumor suppressers p53 and Rb. These findings suggest that regucalcin may play a potential role as a suppressor of human lung cancer, and that downregulation of regucalcin expression may predispose patients to development of lung cancer. Overexpression of regucalcin using gene delivery may constitute a novel therapeutic approach to treating lung cancer.

Senescence marker protein 30 (SMP30) serves as a potential prognostic indicator in hepatocellular carcinoma

Senescence marker protein 30 (SMP30) has been identified as a tumor-related molecule of hepatocellular carcinoma (HCC). Its clinical significance and underlying mechanisms in HCC tissues, however, remain largely unexplored. We have demonstrated a preferentially expressed SMP30 in normal liver using a tissue microarray. By employing real-time quantitative PCR, two tissue microarrays and Oncomine database analysis, we have also shown that the SMP30 in HCC tissues has significantly reduced when compared with that in paired adjacent non-tumor tissues (P = 0.0037). The reduced expression of SMP30 is very noticeably related to larger tumor size (P = 0.012), enhanced TNM (P = 0.009) and worse survival (P < 0.0001) in HCC patients. The analyses using Cox regression have indicated that the decreased SMP30 expression is an independent risk to the reduced overall survival rate of HCC patients (P = 0.001), and the down-regulation of SMP30 in HCC might be mediated by DNA methylation. Moreover, genes co-expressed with SMP30 may affect the prognosis through apoptotic process, biological adhesion and blood coagulation by PANTHER analyses. Our studies have indicated that the SMP30 may serve as a candidate of HCC clinical prognostic marker and a potential therapeutic target.

Prolonged survival in hepatocarcinoma patients with increased regucalcin gene expression: HepG2 cell proliferation is suppressed by overexpression of regucalcin in vitro

Hepatocellular carcinoma (HCC) is one of the most common malignant cancers worldwide and ranks third in overall global cancer-related mortality rates. Importantly, in this study gene expression data demonstrate that prolonged survival in HCC patients is associated with increased regucalcin gene expression. Regucalcin has been shown to play a pivotal role as a transcription repressor and diminished expression or activity of regucalcin may play a key role in the development of human carcinogenesis. Indeed, overexpression of regucalcin suppressed the proliferation, cell death, and migration of human HCC HepG2 cells in vitro. Mechanistically, regucalcin induced G1 and G2/M phase cell cycle arrest of HepG2 cells through suppression of multiple signaling pathways including Ras, Akt, MAP kinase and SAPK/JNK and by increasing the tumor suppressors p53 and Rb. Furthermore, the oncogenes c-fos and c-myc were suppressed by overexpression of regucalcin, and overexpression of regucalcin caused an increase in p21 and a decrease in NF-κB p65 and β-catenin. These findings suggest that regucalcin may play a potential role as a suppressor of human HCC, and that diminished expression of regucalcin may predispose patients to development of HCC. Overexpression of regucalcin may constitute a novel therapeutic approach to treating HCC.

Potential suppressive effects of gentian violet on human breast cancer MDA-MB-231 cells in vitro: Comparison with gemcitabine

Gentian violet (GV), a cationic triphenylmethane dye, is used as an antifungal and antibacterial agent. Recently, attention has been focused on GV as a potential chemotherapeutic and antiangiogenic agent. The present study was undertaken to determine the suppressive effects of GV on human breast cancer MDA-MB-231 cells in vitro. The proliferation of MDA-MB-231 cells was suppressed by culture with GV (1-200 nM). The suppressive effects of GV on cell proliferation were not potentiated in the presence of various inhibitors that induce cell cycle arrest in vitro. This finding suggested that GV inhibits G1 and G2/M phase cell cycle arrest in MDA-MB-231 cells. The suppressive effects of GV on proliferation are mediated through the inhibition of various signaling pathways or nuclear transcription in vitro. Moreover, the suppressive effects of GV on cell proliferation were compared with that of gemcitabine, a strong antitumor agent that induces nuclear DNA damage. Notably, the culture with gemcitabine >50 nM suppressed cell proliferation, while the effects of GV were observed at >1 nM. The suppressive effects of gemcitabine on cell proliferation were not potentiated by GV. Overall, the present study demonstrated that GV exhibits a potential suppressive effect on the proliferation of human breast cancer MDA-MB-231 cells in vitro.

Increased regucalcin gene expression extends survival in breast cancer patients: Overexpression of regucalcin suppresses the proliferation and metastatic bone activity in MDA-MB-231 human breast cancer cells in vitro

Human breast cancer is highly metastatic to bone and drives bone turnover. Breast cancer metastases cause osteolytic lesions and skeletal damage that leads to bone fractures. Regucalcin, which plays a pivotal role as an inhibitor of signal transduction and transcription activity, has been suggested to act as a suppressor of human cancer. In the present study, we compared the clinical outcome between 44 breast cancer patients with higher regucalcin expression and 43 patients with lower regucalcin expression. Prolonged relapse-free survival was identified in the patients with increased regucalcin gene expression. We further demonstrated that overexpression of full length, but not alternatively spliced variants of regucalcin, induces G1 and G2/M phase cell cycle arrest, suppressing the proliferation of MDA-MB-231 cells, a commonly used in vitro model of human breast cancer that metastasize to bone causing osteolytic lesions. Overexpression of regucalcin was found to suppress multiple signaling pathways including Akt, MAP kinase and SAPK/JNK, and NF-κB p65 and β-catenin along with increased p53, a tumor suppressor, and decreased K-ras, c-fos and c-jun. Moreover, we found that co-culture of regucalcin-overexpressing MDA-MB-231 cells with mouse bone marrow cells prevented enhanced osteoclastogenesis and suppressed mineralization in mouse bone marrow cells in vitro. Taken together, the present study suggests that regucalcin may have important anticancer properties in human breast cancer patients. Mechanistically, these effects are likely mediated through suppression of multiple signaling pathways, upregulation of p53 and downregulation of oncogenes leading to anti-proliferative effects and reduced metastases to bone, a phenotype associated with poor clinical outcome.

Prolonged survival in pancreatic cancer patients with increased regucalcin gene expression: Overexpression of regucalcin suppresses the proliferation in human pancreatic cancer MIA PaCa-2 cells in vitro

Approximately 90% of all pancreatic cancers are pancreatic ductal adenocarcinomas (PDAC). PDAC is a highly aggressive malignancy and is one of the deadliest. This poor clinical outcome is due to the prominent resistance of pancreatic cancer to drug and radiation therapies. Regucalcin plays a pivotal role as a suppressor protein in signal transduction in various types of cells including tumor tissues. We demonstrated that the prolonged survival is induced in PDAC patients with increased regucalcin gene expression using a dataset of PDAC obtained from GEO database (GSE17891) together with the clinical annotation data file. Moreover, overexpression of regucalcin with full length was demonstrated to suppress the proliferation, cell death and migration in human pancreatic cancer MIA PaCa-2 (K-ras mutated) cells that possess resistance to drug and radiation therapies. Suppressive effects of regucalcin on cell proliferation and death were not seen in the cells overexpressed with regucalcin cDNA alternatively spliced variants (deleted exon 4 or deleted exon 4 and 5). Regucalcin was suggested to induce G1 and G2/M phase cell cycle arrest in MIA PaCa-2 cells. Suppressive effects of regucalcin on cell proliferation were independent of cell death. Overexpression of regucalcin was found to suppress signaling pathways including Akt, MAP kinase and SAPK/JNK, to increase the protein levels of p53, a tumor suppresser, and to decrease K-ras, c-fos and c-jun, a oncogene, by suppressing signaling pathways that are related to signaling of K-ras. Regucalcin may play a potential role as a suppressor protein in human pancreatic cancer.

The flavonoid p-hydroxycinnamic acid exhibits anticancer effects in human pancreatic cancer MIA PaCa-2 cells in vitro: Comparison with gemcitabine

Pancreatic cancer is a highly aggressive malignancy with a notoriously dismal prognosis. A major contributor to this poor clinical outcome is pancreatic cancer's prominent chemoresistance. The present study was undertaken to determine whether the flavonoid p‑hydroxycinnamic acid (HCA), which is a botanical factor, possesses anticancer effects on cloned human pancreatic cancer MIA PaCa‑2 cells that possess resistance to radiation therapy in vitro. Proliferation of MIA PaCa‑2 cells was suppressed after culture with HCA (10‑1,000 nM). Such an effect was also noted in human pancreatic cancer Pt45P1 cells. In the MIA PaCa‑2 cells, HCA induced G1 and G2/M phase cell cycle arrest in the cells. The suppressive effects of HCA on proliferation were suggested to be mediated through the inhibition of various signaling pathways related to nuclear factor‑κB (NF‑κB), extracellular signal‑regulated kinase (ERK), protein kinase C, phosphatidylinositol 3‑kinase (PI3K) or nuclear transcription activity. Moreover, HCA was found to stimulate cell death in the MIA PaCa‑2 and Pt45P1 cells in vitro. The anticancer effects of HCA on MIA PaCa‑2 cells were exhibited at a lower concentration than gemcitabine, a potent cancer drug. The flavonoid HCA may be a useful tool in the therapy of human pancreatic cancer in vivo.

Effect of extracellular calcium on regucalcin expression and cell viability in neoplastic and non-neoplastic human prostate cells

Extracellular calcium (Ca2+o) and its receptor, the Ca2+-sensing receptor (CaSR), play an important role in prostate physiology, and it has been shown that the deregulation of Ca2+ homeostasis and the overexpression of CaSR are involved in prostate cancer (PCa). Regucalcin (RGN), a Ca2+-binding protein that plays a relevant role in intracellular Ca2+ homeostasis, was identified as an under-expressed protein in human PCa. Moreover, RGN was associated with suppression of cell proliferation, suggesting that the loss of RGN may favor development and progression of PCa. This work aims to unveil the role of Ca2+o on RGN expression and viability of non-neoplastic (PNT1A) and neoplastic (LNCaP) prostate cell lines. It was demonstrated that Ca2+o up-regulates RGN expression in both cell lines, but important differences were found between cells for dose- and time-responses to Ca2+o treatment. It was also shown that high [Ca2+]o triggers different effects on cell proliferation of neoplastic and non-neoplastic PCa cells, which seems to be related with RGN expression levels. This suggests the involvement of RGN in the regulation of cell proliferation in response to Ca2+o treatment. Also, the effect of Ca2+o on CaSR expression seems to be dependent of RGN expression, which is strengthened by the fact that RGN-knockdown in PNT1A cells increases the CaSR expression, whereas transgenic rats overexpressing RGN exhibit low levels of CaSR. Overall, our results highlighted the importance of RGN as a regulatory protein in Ca2+-dependent signaling pathways and its deregulation of RGN expression by Ca2+o may contribute for onset and progression of PCa.

Regucalcin expression in bovine tissues and its regulation by sex steroid hormones in accessory sex glands

Regucalcin (RGN) is a mammalian Ca2+-binding protein that plays an important role in intracellular Ca2+ homeostasis. Recently, RGN has been identified as a target gene for sex steroid hormones in the prostate glands and testis of rats and humans, but no studies have focused on RGN expression in bovine tissues. Thus, in the present study, we examined RGN mRNA and protein expression in the different tissues and organs of veal calves and beef cattle. Moreover, we investigated whether RGN expression is controlled through sex steroid hormones in bovine target tissues, namely the bulbo-urethral and prostate glands and the testis. Sex steroid hormones are still illegally used in bovine husbandry to increase muscle mass. The screening of the regulation and function of anabolic sex steroids via modified gene expression levels in various tissues represents a new approach for the detection of illicit drug treatments. Herein, we used quantitative PCR, western blot and immunohistochemistry analyses to demonstrate RGN mRNA and protein expression in bovine tissues. In addition, estrogen administration down-regulated RGN gene expression in the accessory sex glands of veal calves and beef cattle, while androgen treatment reduced RGN gene expression only in the testis. The confirmation of the regulation of RGN gene expression through sex steroid hormones might facilitate the potential detection of hormone abuse in bovine husbandry. Particularly, the specific response in the testis suggests that this tissue is ideal for the detection of illicit androgen administration in veal calves and beef cattle.

Inhibition of SMP30 gene expression influences the biological characteristics of human Hep G2 cells

Senescence marker protein 30 (SMP30), a hepatocellular carcinoma (HCC) associated antigen had been identified by our research group. To study its mechanisms of regulation and associations with the occurrence and development of HCC, we inhibited expression by RNAi technique, and observed effects on the biological characteristics of Hep G2 cells. In cell viability assays, cell growth in the experimental group (with siRNA transfection) was elevated. In Transwell invasion assays, compared with blank and control groups, numbers of invading cells in the experimental group were significantly increased, whereas in apoptosis assays, the percentage apoptosis demonstrated no differences, but after UV irradiation, that in the experimental group was higher than the other two groups. In a word, SMP30 can inhibit the proliferation and invasion of human hepatoma cells and thus can be regarded as a cancer suppressive factor.

Involvement of regucalcin as a suppressor protein in human carcinogenesis: insight into the gene therapy

Regucalcin, which its gene is located on the X chromosome, plays a multifunctional role as a suppressor protein in cell signal transduction in various types of cells and tissues. The suppression of regucalcin gene expression has been shown to involve in carcinogenesis. Regucalcin gene expression was uniquely downregulated in carcinogenesis of rat liver in vivo, although the expression of other many genes was upregulated, indicating that endogenous regucalcin plays a suppressive role in the development of hepatocarcinogenesis. Overexpression of endogenous regucalcin was found to suppress proliferation of rat cloned hepatoma cells in vitro. Moreover, the regucalcin gene and its protein levels were demonstrated specifically to downregulate in human hepatocellular carcinoma by analysis with multiple gene expression profiles and proteomics. Regucalcin gene expression was also found to suppress in human tumor tissues including kidney, lung, brain, breast and prostate, suggesting that repressed regucalcin gene expression leads to the development of carcinogenesis in various tissues. Regucalcin may play a role as a suppressor protein in carcinogenesis. Overexpression of endogenous regucalcin is suggested to reveal preventive and therapeutic effects on carcinogenesis. Delivery of the regucalcin gene may be a novel useful tool in the gene therapy of carcinogenesis. This review will discuss regarding to an involvement of regucalcin as a suppressor protein in human carcinogenesis in insight into the gene therapy.

Regucalcin is an androgen-target gene in the rat prostate modulating cell-cycle and apoptotic pathways

BACKGROUND

Regucalcin (RGN) is a calcium (Ca(2+) )-binding protein underexpressed in prostate adenocarcinoma comparatively to non-neoplastic prostate or benign prostate hyperplasia cases. Moreover, RGN expression is negatively associated with the cellular differentiation of prostate adenocarcinoma, suggesting that loss of RGN may be associated with tumor onset and progression. However, the RGN actions over the control of prostate cell growth have not been investigated.

METHODS

Androgens are implicated in the promotion of prostate cell proliferation, thus we studied the in vivo effect of androgens on RGN expression in rat prostate. The role of RGN modulating cell proliferation and apoptotic pathways in rat prostate was investigated using transgenic animals (Tg-RGN) overexpressing the protein.

RESULTS

In vivo stimulation with 5α-dihydrotestosterone (DHT) down-regulated RGN expression in rat prostate. Cell proliferation index and prostate weight were reduced in Tg-RGN, which was concomitant with altered expression of cell-cycle regulators. Tg-RGN presented diminished expression of the oncogene H-ras and increased expression of cell-cycle inhibitor p21. Levels of anti-apoptotic Bcl-2, as well as the Bcl-2/Bax protein ratio were increased in prostates overexpressing RGN. Both caspase-3 expression and enzyme activity were decreased in the prostates of Tg-RGN.

CONCLUSIONS

Overexpression of RGN resulted in inhibition of cell proliferation and apoptotic pathways, which demonstrated its role maintaining prostate growth balance. Thus, deregulation of RGN expression may be an important event favoring the development of prostate cancer. Moreover, the DHT effect down-regulating RGN expression in rat prostate highlighted for the importance of this protein in prostatic physiology.

Alternatively spliced variants of the regucalcin gene in various human normal and tumor tissues

Regucalcin plays a pivotal role as a suppressor protein in signal transduction in various cell types. The regucalcin gene, which is localized on the X chromosome, consists of 7 exons and 6 introns. Decreased liver regucalcin gene expression has been suggested to play a suppressive role in the development of hepatocellular carcinogenesis in animal models. This study was undertaken to determine the changes in regucalcin gene expression in various human normal and tumor tissues, including liver, kidney, brain and lung tissues. The full-length and alternatively spliced variants of regucalcin mRNA were found to be expressed in various human tissues. This expression was suppressed in tumor tissues of hepatocellular carcinoma, kidney transitional cell carcinoma, brain malignant meningioma and lung non-small cell carcinoma. The full-length regucalcin protein was found to be highly expressed in normal human liver and kidney tissues; its expression was suppressed, however, in the liver and kidney tumor tissues. The spliced variant proteins were found to be expressed in the normal liver and kidney tissues, and decreased in the tumor tissues. Such alternative variants were not observed in the liver and kidneys of rats and mice. The alternatively spliced variants of the regucalcin gene were found to be expressed in various human normal and tumor tissues.

The diverse roles of calcium-binding protein regucalcin in cell biology: from tissue expression and signalling to disease

Regucalcin (RGN) is a calcium (Ca(2+))-binding protein widely expressed in vertebrate and invertebrate species, which is also known as senescence marker protein 30, due to its molecular weight (33 kDa) and a characteristically diminished expression with the aging process. RGN regulates intracellular Ca(2+) homeostasis and the activity of several proteins involved in intracellular signalling pathways, namely, kinases, phosphatases, phosphodiesterase, nitric oxide synthase and proteases, which highlights its importance in cell biology. In addition, RGN has cytoprotective effects reducing intracellular levels of oxidative stress, also playing a role in the control of cell survival and apoptosis. Multiple factors have been identified regulating the cell levels of RGN transcripts and protein, and an altered expression pattern of this interesting protein has been found in cases of reproductive disorders, neurodegenerative diseases and cancer. Moreover, RGN is a serum-secreted protein, and its levels have been correlated with the stage of disease, which strongly suggests the usefulness of this protein as a potential biomarker for monitoring disease onset and progression. The present review aims to discuss the available information concerning RGN expression and function in distinct cell types and tissues, integrating cellular and molecular mechanisms in the context of normal and pathological conditions. Insight into the cellular actions of RGN will be a key step towards deepening the knowledge of the biology of several human diseases.

Suppressive role of regucalcin in liver cell proliferation: involvement in carcinogenesis

Regucalcin (RGN/SMP30) was discovered in 1978 and is a unique calcium-binding protein contains no EF-hand motif calcium-binding domain. Its name, regucalcin, was proposed as it suppresses activation of enzymes related to calcium signalling. The regucalcin gene (rgn) is localized on the X chromosome. Regucalcin plays its role of suppressor protein in intracellular signalling pathways, including of protein kinases and protein phosphatase activities, protein synthesis, and DNA and RNA synthesis in liver cells. Overexpression of endogenous regucalcin has a suppressive effect on cell proliferation in modelled rat hepatoma H4-II-E cells, which are induced by various signalling stimulations in vitro. This suppressive effect is independent of apoptosis. Endogenous regucalcin plays a suppressive role on overproduction of proliferating cells in regenerating rat liver in vivo. Regucalcin mRNA expression is uniquely down-regulated in development of carcinogenesis in liver of rats in vivo. Regucalcin mRNA and protein expressions are also depressed in human hepatoma HepG2 cells, MCF-7 breast cancer cells, and prostate cancer LNCaP cells. Depression of regucalcin expression may be associated with activity progression of carcinogens. Regucalcin may be a key molecule suppressor protein in cell proliferation and carcinogenesis.

Role of regucalcin in cell nuclear regulation: involvement as a transcription factor

Regucalcin (RGN/SMP30) was discovered in 1978 as a calcium (Ca(2+))-binding protein that contains no EF-hand motif of the Ca(2+)-binding domain. The name of regucalcin was proposed for this Ca(2+)-binding protein, which can regulate various Ca(2+)-dependent enzyme activations in liver cells. The regucalcin gene is localized on the X chromosome. Regucalcin plays a multifunctional role in cell regulation through maintaining intracellular Ca(2+) homeostasis and suppressing signal transduction in various cell types. The cytoplasmic regucalcin is translocated into the nucleus and inhibits nuclear Ca(2+)-dependent and -independent protein kinases and protein phosphatases, Ca(2+)-activated deoxyribonucleic acid (DNA) fragmentation and DNA and ribonucleic acid (RNA) synthesis. Moreover, overexpression of endogenous regucalcin regulates the gene expression of various proteins that are related to cell proliferation and apoptosis. This review will discuss the role of regucalcin in the regulation of cell nuclear function and an involvement in gene expression as a novel transcription factor.

DNA methylation as an adjunct to histopathology to detect prevalent, inconspicuous dysplasia and early-stage neoplasia in Barrett's esophagus

PURPOSE

Endoscopic surveillance of Barrett's esophagus is problematic because dysplasia/early-stage neoplasia is frequently invisible and likely to be missed because of sampling bias. Molecular abnormalities may be more diffuse than dysplasia. The aim was therefore to test whether DNA methylation, especially on imprinted and X-chromosome genes, is able to detect dysplasia/early-stage neoplasia.

EXPERIMENTAL DESIGN

27K methylation arrays were used to find genes best able to differentiate between 22 Barrett's esophagus and 24 esophageal adenocarcinoma (EAC) samples. These were validated using pyrosequencing on a retrospective cohort (60 Barrett's esophagus, 36 dysplastic, and 90 EAC) and then in a prospective multicenter study (98 Barrett's esophagus patients, including 28 dysplastic and 9 early EAC) designed to utilize biomarkers to stratify patients according to their prevalent dysplasia/EAC status.

RESULTS

Genes (23%) on the array, including 7% of X-linked and 69% of imprinted genes, have shown statistically significant changes in methylation in EAC versus Barrett's esophagus (Wilcoxon P < 0.05). 6/7 selected candidate genes were successfully internally (Pearson's P < 0.01) and externally validated (ANOVA P < 0.001). Four genes (SLC22A18, PIGR, GJA12, and RIN2) showed the greatest area under curve (0.988) to distinguish between Barrett's esophagus and dysplasia/EAC in the retrospective cohort. This methylation panel was able to stratify patients from the prospective cohort into three risk groups based on the number of genes methylated (low risk: <2 genes, intermediate: 2, and high: >2).

CONCLUSION

Widespread DNA methylation changes were observed in Barrett's carcinogenesis including ≈70% of known imprinted genes. A four-gene methylation panel stratified patients with Barrett's esophagus into three risk groups with potential clinical utility.

Natural isothiocyanates: genotoxic potential versus chemoprevention

Isothiocyanates, occurring in many dietary cruciferous vegetables, show interesting chemopreventive activities against several chronic-degenerative diseases, including cancer, cardiovascular diseases, neurodegeneration, diabetes. The electrophilic carbon residue in the isothiocyanate moiety reacts with biological nucleophiles and modification of proteins is recognized as a key mechanism underlying the biological activity of isothiocyanates. The nuclear factor-erythroid-2-related factor 2 system, which orchestrates the expression of a wide array of antioxidant genes, plays a role in the protective effect of isothiocyanates against almost all the pathological conditions reported above. Recent emerging findings suggest a further common mechanism. Chronic inflammation plays a central role in many human diseases and isothiocyanates inhibit the activity of many inflammation components, suppress cyclooxygenase 2, and irreversibly inactivate the macrophage migration inhibitory factor. Due to their electrophilic reactivity, some isothiocyanates are able to form adducts with DNA and induce gene mutations and chromosomal aberrations. DNA damage has been demonstrated to be involved in the pathogenesis of various chronic-degenerative diseases of epidemiological relevance. Thus, the genotoxicity of the isothiocyanates should be carefully considered. In addition, the dose-response relationship for genotoxic compounds does not suggest evidence of a threshold. Thus, chemicals that are genotoxic pose a greater potential risk to humans than non-genotoxic compounds. Dietary consumption levels of isothiocyanates appear to be several orders of magnitude lower than the doses used in the genotoxicity studies and thus it is highly unlikely that such toxicities would occur in humans. However, the beneficial properties of isothiocyanates stimulated an increase of dietary supplements and functional foods with highly enriched isothiocyanate concentrations on the market. Whether such concentrations may exert a potential health risk cannot be excluded with certainty and an accurate evaluation of the toxicological profile of isothiocyanates should be prompted before any major increase in their consumption be recommended or their clinical use suggested.

Senescence Marker Protein 30: Functional and Structural Insights to its Unknown Physiological Function

Senescence marker protein 30 (SMP30) is a multifunctional protein involved in cellular Ca(2+) homeostasis and the biosynthesis of ascorbate in non-primate mammals. The primary structure of the protein is highly conserved among vertebrates, suggesting the existence of a significant physiological function common to all mammals, including primates. Enzymatic activities of SMP30 include aldonolactone and organophosphate hydrolysis. Protective effects against apoptosis and oxidative stress have been reported. X-ray crystallography revealed that SMP30 is a six-bladed β-propeller with structural similarity to paraoxonase 1, another protein with lactonase and organophosphate hydrolase activities. SMP30 has recently been tied to several physiological conditions including osteoporosis, liver fibrosis, diabetes, and cancer. This review aims to describe the recent advances made toward understanding the connection between molecular structure, enzymatic activity and physiological function of this highly conserved, multifaceted protein.

Senescence marker protein 30 (SMP30)/regucalcin (RGN) expression decreases with aging, acute liver injuries and tumors in zebrafish

Senescence marker protein 30 (SMP30)/regucalcin (RGN) is known to be related to aging, hepatocyte proliferation and tumorigenesis. However, expression and function of non-mammalian SMP30/RGN is poorly understood. We found that zebrafish SMP30/RGN mRNA expression decreases with aging, partial hepatectomy and thioacetamide-induced acute liver injury. SMP30/RGN expression was also greatly decreased in a zebrafish liver cell line. In addition, we induced liver tumors in adult zebrafish by administering diethylnitrosamine. Decreased expression was observed in foci, hepatocellular carcinomas, cholangiocellular carcinomas and mixed tumors as compared to the surrounding area. We thus showed the importance of SMP30/RGN in liver proliferation and tumorigenesis.

SP1 suppresses phorbol 12-myristate 13-acetate induced up-regulation of human regucalcin expression in liver cancer cells

There is a growing evidence that regucalcin (RGN) plays a multifunctional role in liver cancer cells. Previous reports showed that the presence of phorbol 12-myristate 13-acetate (PMA) caused a significant increase in RGN mRNA expression and promoter activity in rat hepatoma cells. In this study, we confirmed that human RGN is also up-regulated by PMA treatment independent of translation, and we identified the mechanism by which PMA up-regulates the expression of human RGN via driving SP1 away from a SP1 motif located within -188/-180 of the promoter in HepG2 cells. Overexpression of SP1 dramatically reduces PMA-induced up-regulation of both internal expression of mRNA and promoter activity, whereas knockdown of SP1 has the opposite effect. Therefore, the present study delineates the fundamental elements in the promoter which will be helpful in the future studies on the regulation of RGN expression in liver cancer.

Serum immunoreactivity of SMP30 and its tissues expression in hepatocellular carcinoma

OBJECTIVES

To detect serum antibody against SMP30 in HCC patients and to evaluate its potential associations with HCC patient's clinical parameter and expression levels in HCC tissues.

DESIGN AND METHODS

Serum antibody to SMP30 was tested by ELISA method; SMP30 mRNA and protein expression in HCC patients were analyzed using the methods of in situ nucleic acid hybridization and immunohistochemistry, respectively.

RESULTS

The highest relevance of SMP30 antibody was associated with HCC (32.4%). The positive rate of SMP30 antibody was not related to the age of patients, tumor size, metastasis and infections of HBV, but the positive rate for SMP30 antibody in the HCC sera with alpha-fetoprotein (AFP) negative was higher (43.6%) compared with that AFP positive (26.2%). Both SMP30 mRNA and protein expression levels were downregulated in HCC and upregulated in adjacent tissues.

CONCLUSIONS

SMP30 may be useful for HCC serologic screening, especially for the patients with AFP negative.

Shotgun proteomics analysis of hibernating arctic ground squirrels

Mammalian hibernation involves complex mechanisms of metabolic reprogramming and tissue protection. Previous gene expression studies of hibernation have mainly focused on changes at the mRNA level. Large scale proteomics studies on hibernation have lagged behind largely because of the lack of an adequate protein database specific for hibernating species. We constructed a ground squirrel protein database for protein identification and used a label-free shotgun proteomics approach to analyze protein expression throughout the torpor-arousal cycle during hibernation in arctic ground squirrels (Urocitellus parryii). We identified more than 3,000 unique proteins from livers of arctic ground squirrels. Among them, 517 proteins showed significant differential expression comparing animals sampled after at least 8 days of continuous torpor (late torpid), within 5 h of a spontaneous arousal episode (early aroused), and 1-2 months after hibernation had ended (non-hibernating). Consistent with changes at the mRNA level shown in a previous study on the same tissue samples, proteins involved in glycolysis and fatty acid synthesis were significantly underexpressed at the protein level in both late torpid and early aroused animals compared with non-hibernating animals, whereas proteins involved in fatty acid catabolism were significantly overexpressed. On the other hand, when we compared late torpid and early aroused animals, there were discrepancies between mRNA and protein levels for a large number of genes. Proteins involved in protein translation and degradation, mRNA processing, and oxidative phosphorylation were significantly overexpressed in early aroused animals compared with late torpid animals, whereas no significant changes at the mRNA levels between these stages had been observed. Our results suggest that there is substantial post-transcriptional regulation of proteins during torpor-arousal cycles of hibernation.

Regucalcin is under-expressed in human breast and prostate cancers: Effect of sex steroid hormones

Regucalcin plays an important role in maintenance of intracellular Ca(2+) homeostasis, suppresses cell proliferation, inhibits expression of oncogenes, and increases the expression of tumour suppressor genes. This suggests that regucalcin functions may be altered in cancer tissues. In this study the regucalcin expression in breast and prostate cancer cases was analysed by RT-PCR and immunohistochemistry showing that the mRNA and/or protein are under-expressed in these tumors. The effect of sex steroid hormones on regucalcin expression in breast and prostate cancer cells was determined by real-time PCR. MCF-7 and LNCaP cells were stimulated with 0, 1, and 10 nM of 17beta-estradiol (E(2)) or 5alpha-dihydrotestosterone (DHT), respectively, for 0, 6, 12, 24, and 48 h. MCF-7 cells were also stimulated with E(2) conjugated to BSA (E(2)-BSA). To explore the mechanisms underlying the sex steroid regulation of regucalcin expression, control treatments with ICI 182,780, flutamide and cyclohexamide were carried out. E(2) effects regulating regucalcin expression were not abrogated in the presence of ICI 182,780, and were similar to those observed with E(2)-BSA, which suggests the involvement of a membrane-bound estrogen receptor. In LNCaP cells, DHT down-regulated regucalcin expression, an effect inhibited by the presence of both flutamide and cyclohexamide, suggesting the involvement of androgen receptor and de novo protein synthesis. The loss of regucalcin expression in breast and prostate cancer cases and the regulation of its expression by sex steroid hormones suggest that it may be associated with development and progression of these human tumors.