Cadmium promotes the proliferation of triple-negative breast cancer cells through EGFR-mediated cell cycle regulation

Mechanisms of Heavy Metal Cadmium (Cd)-Induced Malignancy

The environmental pollution of cadmium is worsening, and its significant carcinogenic effects on humans have been confirmed. Cadmium can induce cancer through various signaling pathways, including the ERK/JNK/p38MAPK, PI3K/AKT/mTOR, NF-κB, and Wnt. It can also cause cancer by directly damaging DNA and inhibiting DNA repair systems, or through epigenetic mechanisms such as abnormal DNA methylation, LncRNA, and microRNA. However, the detailed mechanisms of Cd-induced cancer are still not fully understood and require further investigation.

Cadmium promotes colorectal cancer metastasis through EGFR/Akt/mTOR signaling cascade and dynamics

Cadmium (Cd) is a hazardous environmental heavy metal with a prolonged biological half-life. Due to the main route of foodborne exposure, the intestinal tract is particularly vulnerable to Cd-induced toxicity. However, the chronic toxicity and underlying mechanisms of Cd in intestinal diseases, including colorectal cancer (CRC), still remain vague. Herein, we aim to investigate the long-term effects of Cd exposure on CRC development and the key signaling event. Our findings indicate that chronic and low-dose exposure to Cd promoted the invasion and metastasis capability of CRC cells in vitro and in mice, with a marginal increase in cell growth. The expression of cell junction-related genes was down-regulated while those molecules that facilitate cell mobility were significantly increased by Cd exposure. Epidermal growth factor receptor (EGFR) signaling was identified to play the dominant role in Cd-promoted CRC metastasis. Interestingly, Cd activated EGFR in a non-canonical manner that exhibited distinct signaling dynamics from the canonical ligand. In contrast to EGF, which induced transient EGFR signaling and ERK activation, Cd promoted sustained EGFR signaling to trigger Akt/mTOR cascade. The unique signaling dynamics of EGFR induced by Cd provoked responses that preferably enhanced the metastatic capacity rather than the growth. Furthermore, blockade of EGFR abrogated the promoting effects of Cd on the liver metastasis of CRC cells. In conclusion, this study provides a better understanding of the long-term influences of environmental Cd on CRC metastasis and reveals the unique EGFR signaling dynamics induced by Cd exposure.

Bioinformatics analysis of key genes and potential mechanism in cadmium-induced breast cancer progression

Cadmium (Cd) may be associated with breast cancer progression, but the detailed molecular mechanism has not been fully elucidated. In this study, one public dataset (GSE136595) was used to identify differentially expressed genes (DEGs) in Cd-treated MCF-7 breast cancer cells. We determined a total of 2077 DEGs, and Ingenuity Pathway Analysis (IPA) software showed that 246 of them were related to tumor progression. Pathway analysis of these DEGs indicated that the HIF1α signaling and the epithelial-mesenchymal transition (EMT) pathway regulated by growth factors might be activated. Moreover, twist family bHLH transcription factor 1 (TWIST1), lysine demethylase 3A (KDM3A), Kruppel-like factor 4 (KLF4), nuclear protein 1 (NUPR1), neurogenin 3 (NEUROG3), and HNF1 homeobox B (HNF1B) might be the key transcription factors. And the result of protein-protein interaction (PPI) analysis showed that the hub genes in these 246 DEGs were tumor protein p53 (TP53), polo-like kinase 1 (PLK1), sirtuin 1 (SIRT1), protein tyrosine phosphatase non-receptor type 11 (PTPN11), caspase 8 (CASP8), cyclin-dependent kinase 6 (CDK6), calmodulin 3 (CALM3), KRAS proto-oncogene (KRAS), extra spindle pole bodies like 1 (ESPL1), and marker of proliferation Ki-67 (MKI67). Further analysis indicated that TWIST1, NUPR1, KRAS, and PTPN11 were related to the prognostic of breast cancer based on the Cancer Genome Atlas (TCGA) and they were validated to be upregulated in the Cd-treated MCF-7 cells. Our results suggested that the HIF1α signaling and the EMT pathway regulated by growth factors might be participant in the Cd-induced breast cancer progression and TWIST1, NUPR1, KRAS, and PTPN11 might be potential key genes.

Low-dose cadmium exposure facilitates cell proliferation by promoter hypermethylation of RASSF1A and DAPK1 genes

Cadmium (Cd) at low concentrations has a potential to promote cell proliferation. However, the molecular mechanisms of Cd-induced proliferation are not well understood. Here, we reported that Cd (0-500 nM) significantly promoted the proliferation of HepG2 cells as demonstrated by elevated cell viability, more EdU-positive cells and increased gene expression of KI-67 and COX-2. Meanwhile, the gene expression of DNA methyltransferases was found to be elevated while that of tumor suppressor genes DAPK1 and RASSF1A were decreased under Cd exposure. Correspondingly, the methylation level of promoters in DAPK1 and RASSF1A were increased. Specifically, the CpG sites at -461 (Chr3:50, 374, 481) of RASSF1A promoter, and that at -260 (Chr9:90, 113, 207), -239 (Chr9:90, 113, 228), and -68 (Chr9:90, 113, 399) of DAPK1 promoter, were significantly hypermethylated. Moreover, 5-azacytidine (an inhibitor of DNA methyltransferase) partly impaired Cd-induced promoter hypermethylation of RASSF1A and DAPK1 genes, increased their expressions and slowed down Cd-induced cell proliferation, suggesting that DNA methylation play an essential part in Cd-boosted proliferation. The study showed that Cd caused promoter hypermethylation of RASSF1A and DAPK1, decreasing their expression and leading to higher level of cell proliferation. Furthermore, Cd at low concentrations could influence DNA methylation, which may serve as the proliferative mechanism of Cd.

Cadmium promotes apoptosis and inflammation via the circ08409/miR-133a/TGFB2 axis in bovine mammary epithelial cells and mouse mammary gland

Cadmium is a common environmental heavy metal pollutant that can accumulate over long periods of time and cause disease. Thus, analysis of the molecular mechanisms affected by cadmium in the body could be of great significance for the prevention and treatment of cadmium-related diseases. In this study, flow cytometry, immunofluorescence, transmission electron microscopy, H&E (Hematoxylin Eosin) staining and TUNEL (TdT-mediated dUTP Nick-End Labeling) assays were used to verify that cadmium induced apoptosis and immune responses in bovine mammary epithelial cells (BMECs) and in mouse mammary gland. Isolated BMECs cultured with or without cadmium were collected to screen miRNA (microRNA) using high-throughput sequencing. There were 42 differentially-expressed miRNAs among which 27 were upregulated and 15 downregulated including bta-miR-133a, bta-miR-23b-5p, bta-miR-29e, bta-miR-365-5p, bta-miR-615, bta-miR-7, bta-miR-11975, bta-miR-127, and bta-miR-411a. Among those, miR-133a (which can specifically target TGFB2 (Recombinant Transforming Growth Factor Beta 2) was the most significantly downregulated with a fold-change of 5.27 in BMECs cultured with cadmium. Application of the double luciferase reporter system, western blotting, and qRT-PCR (Quantitative Real-time PCR) revealed that circ08409 can directly bind to miR-133a. Experiments demonstrated that circRNA-08409 could adsorb bta-miR-133a. Both circ08409 and TGFB2 significantly increased apoptosis and altered expression level of a series of inflammatory factors in BMECs. In contrast, miR-133a decreased significantly apoptosis and inflammation in the cells. Compared with cultures receiving only cadmium, the miR-133a+cadmium cultures exhibited significant reductions in the occurrence of late apoptosis. Overall, results indicated that circ08409 could relieve the inhibitory effect of miR-133a on TGFB2 expression by combining with miR-133a and subsequently modulating cell proliferation, apoptosis and inflammation. Overall, the data suggested that the circ08409/miR-133a/TGFB2 axis might play a role in mediating the effect of cadmium on BMECs. As such, data provide novel insights into controlling hazards that cadmium could induce in the mammary gland.

TPD7 inhibits the non-small cell lung cancer HCC827 cell growth by regulating EGFR signalling pathway

Non-small cell lung cancer (NSCLC) accounts for 85% of lung cancer cases, and is characterized by more insensitivity to chemotherapy and poor prognosis. Epidermal growth factor receptor (EGFR) has been confirmed as a tumorigenic driving factor of NSCLC. Taspine has been proved effective in the inhibition of malignant tumours. Here, we found TPD7, a novel taspine derivative, exerted most inhibitory effect on EGFR-dependent HCC827 cells and investigated the underling mechanism. In addition, TPD7 could block cell cycle at G0/G1 phase of HCC827 cells by regulating the expression of cyclin D1 and cyclin E. Furthermore, TPD7 induced HCC827 cell apoptosis by regulating the expression of BCL-2 family proteins. Further study revealed that TPD7 could down-regulate the phosphorylation of EGFR and downstream members. TPD7 might present a potential EGFR inhibitor in the treatment of NSCLC.

BST2 promotes growth and induces gefitinib resistance in oral squamous cell carcinoma via regulating the EGFR pathway

INTRODUCTION

Gefitinib, well known as a new antitumor agent, has been applied in various cancers such as oral squamous cell carcinoma (OSCC). However, most patients eventually acquire resistance to gefitinib, and the molecular mechanism of gefitinib resistance is not well described. Bone marrow stromal cell antigen 2 (BST2) has been reported to promote tumor cell growth and confer chemotherapy resistance in various cancers. However, the roles of BST2 in OSCC still need to be fully understood.

MATERIAL AND METHODS

We determined the expression of BST2 in OSCC tissues using qRT-PCR, immunohistochemistry and western blot. Next, we used MTT assay, flow cytometry and western blot to determine the roles of BST2 in OSCC cell proliferation, cycle progression and apoptosis, respectively. Furthermore, we evaluated the effect of BST2 on gefitinib resistance in OSCC cells and explored the related molecular mechanism.

RESULTS

BST2 expression was up-regulated in OSCC tissues compared with the adjacent normal tissues. BST2 overexpression significantly enhanced OSCC cell proliferation, mediated the cell cycle progression and inhibited cell apoptosis. Additionally, the results showed that BST2 overexpression effectively induced gefitinib resistance in OSCC cells. Subsequent analysis revealed that the underlying mechanism was associated with activation of the EGFR pathway.

CONCLUSIONS

Our study indicated that BST2 promoted growth and induced gefitinib resistance in OSCC cells, at least partially, through regulating the EGFR pathway. Thus, BST2 could be used as a therapeutic target for gefitinib resistance in OSCC.

Human placental cell line HTR-8/SVneo accumulates cadmium by divalent metal transporters DMT1 and ZIP14

Cadmium (Cd) is a global pollutant that accumulates in the placenta and can cause placental dysfunction. Although iron transporters have been suggested to participate in placental Cd uptake, it is still unknown which transporters are actually involved in this process. We specifically aimed to study the role of three iron transporters in the uptake of Cd into the placental cell line HTR-8/SVneo. For this purpose, Divalent Metal Transporter (DMT)1 and ZRT/IRT like protein (ZIP)8 and ZIP14 were downregulated and changes in cellular Cd levels analysed in relation to controls. As clearly shown by the reduction of the Cd content by ∼60% in DMT1- and ZIP14-downregulated cells, the two proteins are essential for Cd accumulation in HTR-8/SVneo cells. Using a validated antibody, we show DMT1 to be localised in situ in trophoblast and stromal cells. We further wanted to investigate how placental cells cope with Cd loading and which metallothionein (MT) isoforms they express. Cd-exposed cells accumulate Cd in a dose-dependent manner and upregulate MT2A accordingly (up to 15-fold induction upon 5 μM CdCl₂ treatment for 72 h). 5 μM Cd exposure for 72 h decreased cell number to 60%, an effect that was aggravated by MT2A depletion (cell number reduced to 30%) indicating additive effects. In conclusion, our data suggest that DMT1 and ZIP14 are required for Cd uptake into human placental cells that upregulate MT2A to store and detoxify the metal. Cd storage in the placenta reduces Cd transport to the fetus, which, however, could impair placental functions and fetal development.

Dietary cadmium chloride impairs shell biomineralization by disrupting the metabolism of the eggshell gland in laying hens

In this study, we identified cadmium (Cd) as a potential endocrine disruptor that impairs laying performance, egg quality, and eggshell deposition and induces oxidative stress and inflammation in the eggshell glands of laying hens. A total of 480 38-wk-old laying hens were randomly assigned into 5 groups that were fed a basal diet (control) or a basal diet supplemented with Cd (provided as CdCl2·2.5 H2O) at 7.5, 15, 30, and 60 mg Cd per kg feed for 9 wk. The results showed that, when compared with the control group, a low dose of dietary Cd (7.5 mg/kg) had positive effects on egg quality by improving albumen height, Haugh unit, yolk color, and shell thickness at the third or ninth week. However, with the increase in the dose and duration of Cd exposure, the laying performance, egg quality, and activities of eggshell gland antioxidant enzymes (catalase [CAT], glutathione peroxide [GSH-Px]), and ATPase (Na+/K+-ATPase, Ca2+-ATPase, and Mg2+-ATPase) deteriorated, and the activity of total nitric oxide synthase (T-NOS) and the level of malondialdehyde (MDA) increased significantly (P < 0.05). The histopathology and real-time quantitative PCR results showed that Cd induced endometrial epithelial cell proliferation accompanied by upregulation of the mRNA levels of progesterone receptor (PgR) and epidermal growth factor receptor (EGFR), downregulation of the mRNA levels of estrogen receptor α (ERα) and interleukin 6 (IL6), and inflammation of the eggshell gland accompanied by significantly increased expression of complement C3 and pro-inflammatory cytokine tumor necrosis factor α (TNFα) (P < 0.05). In addition, the ultrastructure of the eggshell showed that dietary supplementation with 7.5 mg/kg Cd increased the palisade layer and total thickness of the shell, but with the increase in dietary Cd supplementation (30 and 60 mg/kg) the thickness of the palisade layer and mammillary layer decreased significantly (P < 0.05), and the outer surface of the eggshell became rougher. Correspondingly, the expression of calbindin 1 (CALB1), ovocalyxin-32 (OCX-32), ovocalyxin-36 (OCX-36), osteopontin (SPP1), and ovocledidin-17 (OC-17) decreased significantly (P < 0.05) with increasing dietary Cd supplementation. Conclusively, the present study demonstrates that dietary supplementation with Cd negatively affects laying performance, egg quality, and eggshell deposition by disturbing the metabolism of eggshell glands in laying hens but has a positive effect on egg quality at low doses.

The effects of cadmium exposure in the induction of inflammation

Inflammation is a physiological process essential for maintaining homeostatic mechanisms in human, but however, exaggerated inflammatory responses are closely related to many chronic diseases. Cadmium (Cd) is a heavy metal with high toxicity when present in food, water and air has the potential of eliciting inflammatory reactions, with a major health risk to human. This review aimed to elucidate on the major routes of Cd exposure, the main organs affected by the exposure, the degree of toxicity as well as the roles of the toxic effects on the immune system which results to inflammatory responses. Immune modulation by Cd may cause serious adverse health effects in humans. Various studies have highlighted the ability of Cd as an environmental pollutant involved in the modulation of the innate, adaptive and mucosal immune responses in relations to the release of chemokine, gene expression, and susceptibility to microbial infections.

Biological and molecular modifications induced by cadmium and arsenic during breast and prostate cancer development

Breast and prostate cancer are two of the most common malignancies worldwide. Both cancers can develop into hormone -dependent or -independent subtypes and are associated to environmental exposure in the context of an inherited predisposition. As and Cd have been linked to the onset of both cancers, with the exception of As, which lacks a definitive association with breast carcinogenesis. The two elements exert an opposite effect dependent on acute versus chronic exposure. High doses of As or Cd were shown to induce cell death in acute experimental exposure, while chronic exposure triggers cell proliferation and viability, which is no longer limited by telomere shortening and apoptosis. The chronically exposed cells also increase their invasion capacity and tumorigenic potential. At molecular level, malignant transformation is evidenced mainly by up-regulation of BCL-2, MMP-2, MMP-9, VIM, Snail, Twist, MT, MLH and down-regulation of Casp-3, PTEN, E-CAD, and BAX. The signaling pathways most commonly activated are KRAS, p53, TGF-β, TNF-α, WNT, NRF2 and AKT. This knowledge could potentially raise public awareness over the health risks faced by the human population living or working in a polluted environment and smokers. Human exposure to As and Cd should be minimize as much as possible. Healthcare policies targeting people belonging to these risk categories should include analysis of: DNA damage, oxidative stress, molecular alterations, and systemic level of heavy metals and of essential minerals. In this review, we present the literature regarding cellular and molecular alterations caused by exposure to As or Cd, focusing on the malignant transformation of normal epithelial cells after long-term intoxication with these two carcinogens.

Endocrine disruption through membrane estrogen receptors and novel pathways leading to rapid toxicological and epigenetic effects

Estrogen binding to estrogen receptors (ESR) triggers signaling cascades within cells. Historically, a major emphasis has been characterizing estrogen-induced genomic actions resulting from binding to nuclear estrogen receptor 1 (nESR1). However, recent evidence indicates the first receptors estrogens encounter as they enter a cell, membrane ESR1 (mESR1), also play crucial roles. Membrane and nuclear ESR are derived from the same transcripts but the former are directed to the membrane via palmitoylation. Binding and activation of mESR1 leads to rapid fluctuations in cAMP and Ca+2 and stimulation of protein kinase pathways. Endocrine disrupting chemicals (EDC) that mimic 17β-estradiol can signal through mESR1 and elicit non-genomic effects. Most current EDC studies have focused on genomic actions via nESR1. However, increasing number of studies have begun to examine potential EDC effects mediated through mESR1, and some EDC might have higher potency for signaling through mESR1 than nESR1. The notion that such chemicals might also affect mESR1 signaling via palmitoylation and depalmitoylation pathways has also begun to gain currency. Recent development of transgenic mice that lack either mESR1 or nESR1, while retaining functional ESR1 in the other compartment, will allow more precise in vivo approaches to determine EDC effects through nESR1 and/or mESR1. It is increasingly becoming apparent in this quickly evolving field that EDC directly affect mESR and estrogen signaling, but such chemicals can also affect proportion of ESR reaching the membrane. Future EDC studies should be designed to consider the full range of effects through mESR alone and in combination with nESR.

Binary-ternary Cd(II)-(hydroxycarboxylic acid)-(aromatic chelator) systems exhibit in vitro cytotoxic selectivity in a tissue-specific manner

Cadmium is a metallotoxin, amply encountered in the environment and derived through physical and anthropogenic activities. Its entry in various organisms leads through water and the food chain to humans, thereby inducing a plethora of pathophysiologies. Delineation of the interactive role of cadmium with physiological and physiologically relevant substrates, requires well-defined forms of cadmium arising from such interactions along with the ensuing chemical reactivity amounting to toxic manifestations and health aberrations. To implement such efforts, low molecular mass substrate metal ion binders are needed, forming species with enhanced solubility and bioavailability. To that end, α-hydroxy isobutyric acid (HIBAH₂) was used in pH-specific synthetic efforts involving bulky aromatic chelators 2,2'-bipyridine (2,2'-bipy) and 1,10-phenanthroline (phen), thus leading to new crystalline materials [Cd(C₄H₇O₃)₂]_n(1), [Cd(C₄H₇O₃)₂(H₂O)₂](2), [{Cd₂(C₄H₇O₃)₂(C₁₀H₈N₂)₂(H₂O)₂}(NO₃)₂]_n·nH₂O(3), and [{Cd₂(C₄H₇O₃)₂(C₁₂H₈N₂)₂(H₂O)₂}(NO₃)₂]_n·2nH₂O(4), which were physicochemically characterized (elemental analysis, FT-IR, NMR, ESI-MS, and X-ray crystallography) in the solid state and solution. Their physicochemical characteristics led to their employment in tissue-specific biological toxicity studies in three different cell lines. Their toxicity profile (cell viability, morphology, chemotacticity) was correlated through genetic biomarkers to apoptotic-necrotic processes, thereby shedding light on cadmium cellular toxicity processes. Finally, the cytoprotective action of specific chelators was examined, lending credence to the notion that appropriately structured chelators and antioxidants may be used as effective deterrent to cadmium toxicity. Collectively, structure-specificity linked to tissue-specific toxicity profiling in well-defined binary-ternary Cd(II)-HIBAH₂ systems exemplifies that metal ion's aberrant interactions in the cellular milieu, meriting further probing into the development of efficient chelators in cadmium detoxification.

Evidences for involvement of estrogen receptor induced ERK1/2 activation in ovarian cancer cell proliferation by Cadmium Chloride

Cadmium (Cd) as a human carcinogen and one of the most toxic industrial and environmental pollutant mimics the estrogenic effects in cell proliferation. So, it might have a role in the incidence and etiology of hormone-related cancers such as ovarian cancer as the most lethal gynecologic malignancy. This study aimed to evaluate the estrogenic effect and underlying mechanism of Cd in ovarian cancer cell line proliferation. OVCAR3 and SKOV3 cell lines were treated with different concentrations of CdCl₂ (0- 50 μM). Cell proliferation was analyzed using MTT and BrdU assay. To evaluate the estrogenic effect of Cd, the cells were pre-incubated with estrogen receptor (ER) antagonist ICI 182,780. The expression of ER was determined using western blotting method. Real-time RT-PCR method was used to assess c-fos, c-jun and FOXO3a mRNA level. The results showed that Cd has an estrogenic proliferative effect at nM concentration range and ICI 182,780 significantly reversed the CdCl₂-induced cell proliferation. Cd also increased the expression of ERs. Cd exposure induced activation of p-ERK1/2 in these cells. Cd also intensified c-jun, c-fos, and FOXO3a mRNA expression. Taken together, the current work suggests that Cd induces ovarian cancer cell proliferation in an ER-dependent mechanism induced ERK1/2 activation pathway. Understanding of downstream targets by which Cd deregulates cell proliferation can be noteworthy to define its underlying carcinogenesis mechanism.

Cadmium induces progesterone receptor gene expression via activation of estrogen receptor in human ovarian cancer cells

Cadmium (Cd) as a metalloesterogen may have a role in development of ovarian cancer. One of the critical target genes of estrogens is progesterone receptors (PRs). There are controversial studies on association between Cd, PRs, and cell proliferation. This study investigates the effect of Cd on proliferation of ovarian cancer cell lines, PRA and PRB expression and their relationship. OVCAR3 and SKOV3 cells were treated with CdCl₂ (1-100 nM) and cell proliferation was assayed using bromodeoxyuridine (BrdU) method. The mechanism underlying the proliferative effect of Cd mediated by PRs was examined using cell transfection with PR- small interfering RNA (siRNA) and western blot analysis. Our results showed the involvement of PRs in Cd induced proliferation of ovarian cancer cells. Progesterone receptors are involved in proliferative effect of Cd. Moreover, Cd modified the expression of PRA and PRB and induced ovarian cancer cell proliferation through the change of PRA/PRB ratio. In conclusion, there is a mechanistic association between Cd effects on ovarian cancer cell proliferation, estrogen receptors and PRs expression.

Cadmium induces apoptotic program imbalance and cell cycle inhibitor expression in cultured human astrocytes

Cadmium is a highly neurotoxic heavy metal impairing neurogenesis and induces neurodegenerative disorders. Toxic concentrations of cadmium induce astrocytic apoptosis by depleting intracellular glutathione levels, elevating intracellular calcium levels, altering mitochondria membrane potentials, and activating JNK and PI3K/Akt signaling pathways. Cadmium suppresses cell proliferation in kidney epithelial cells, lung fibroblasts, and primary myelocytes; however, cadmium's effects on proteins regulating oxidative stress, apoptosis, and cell proliferation in astrocytes are less known. The present study hypothesized that cadmium alters levels of antioxidant enzymes, apoptotic regulator proteins, and cell cycle inhibitor proteins, resulting in apoptosis and cell cycle arrest. Concentrations ≥20 μM cadmium induced apoptosis and led to intracellular changes including DNA fragmentation, reduced mRNA expression of antioxidant enzymes (i.e., catalase and glutathione S transferase-A4), downregulation of B-cell lymphoma 2 (Bcl-2), and upregulation of Bcl-2-associated X protein (Bax). Moreover, cadmium suppressed astrocytic proliferation by inducing S and G2/M phase cell cycle arrest and promoting p53, p21, and p27 expression. In conclusion, this study provides mechanistic insight into cadmium-induced cytotoxicity of astrocytes and highlights potential targets for prevention of cadmium-induced apoptosis and cell cycle arrest.

Suppression of ferroportin expression by cadmium stimulates proliferation, EMT, and migration in triple-negative breast cancer cells

Cadmium (Cd) has been linked to a variety of cancers, including breast cancer; however, the molecular mechanism of its carcinogenic activity is not fully understood. To this end, the present study investigated the roles of ferroportin (FPN), a prognostic marker of breast cancer, in Cd-induced stimulation of cell proliferation and cell migration. Triple-negative MDA-MB-231 cells were treated with 1-3 μM Cd. The cells exhibited significant reduction in FPN expression and concomitant increase in iron concentration. Cells treated with Cd for 8 weeks displayed elevated proliferative and migratory activities which were inversely related with FPN expression. Reduced FPN expression also resulted in EMT as indicated by an increase in the expression of E-cadherin, and a decrease in the expression of N-cadherin, Twist and Slug. Further investigation revealed that Cd suppressed FPN expression at least partially by activating TGF-β, a known regulator of FPN expression. Taken together, these results indicate that Cd-induced stimulation of MDA-MB-231 cell proliferation, EMT, and migration is brought about by suppression of FPN expression and associated disruption of iron homeostasis.

Genistein reduces the activation of AKT and EGFR, and the production of IL6 in cholangiocarcinoma cells involving estrogen and estrogen receptors

Cholangiocarcinoma (CCA) is a malignant tumor of the biliary epithelium associated with Opisthorchis viverrini, primary sclerosing cholangitis and hepatitis viral infection. In the global population, men have higher incidence rates for CCA than women; thus, a gender disparity in the progression of chronic inflammation of the biliary duct leading to malignancy may involve the effects of estrogen (E2). Genistein (GE), a prominent phytoestrogen found in soy products, is an estrogen receptor β (ERβ) agonist and a tyrosine kinase inhibitor. The present study investigated the effects of GE on the growth of CCA cells by cell viability assay. The effects on signaling proteins were detected by western blot analysis and ELISA. Gene expression was examined by RT-qPCR. Two human intrahepatic CCA cell lines, HuCCA‑1 and RMCCA‑1, were utilized. GE (50‑200 µM) reduced the viability of the two cell lines, and also inhibited the activation of epidermal growth factor receptor (EGFR) and AKT, as evidenced by decreasing protein levels of phosphorylated (p)-EGFR (Tyr1173) and p‑AKT (Ser473), respectively. GE altered the mitogen‑activated protein kinase signaling cascade by mediating decreased protein levels of p‑p38 and increased protein levels of p‑ERK1/2. GE significantly decreased the levels of interleukin 6 (IL6) and induced the expression of inducible nitric oxide synthase (iNOS). GE also downregulated the expression of p‑ERα (Ser118) protein and ERα mRNA levels. Finally, GE induced the downregulation of the protein levels of ERβ. Of note, E2 deprivation potentiated the GE-induced reduction of p‑EGFR (Tyr1173) and total AKT proteins and production of IL6, and mediated the downregulation of GE-induced iNOS protein. In conclusion, GE inhibited the growth of human CCA cell lines by reducing the activation of EGFR and AKT, and by attenuating the production of IL6. E2 and ER were also involved in the growth-inhibitory effect of GE in CCA cells.

The protective role of melatonin in cadmium-induced proliferation of ovarian cancer cells

Cadmium (Cd), a ubiquitous environmental and occupational pollutant, acts as a metalloestrogen to induce cell proliferation. It is suggested that Cd may also contribute to the development of estrogen-related cancers like ovarian cancer which is the most lethal cancer in women. Furthermore, it was shown that melatonin has antiproliferative effect on estradiol (E2)-induced proliferation. The aim of the present study was to evaluate whether melatonin inhibits Cd-induced proliferation in ovarian cancer cell lines and also whether Cd and melatonin can modulate estrogen receptor α (ERα) expression. OVCAR3 and SKOV3 human ovarian cancer cell lines were treated with CdCl₂ (1-100 nM) and melatonin (1 μM) for 48 h. Cell proliferation evaluation was carried out by bromodeoxyuridine (BrdU) incorporation assay. ERα expression was detected by western blotting method 24 h after cell treatment. The results were demonstrated that Cd increased proliferation of ovarian cancer cell lines in a dose dependent manner. Melatonin inhibited Cd-induced proliferation of OVCAR3 and SKOV3 cell lines. Moreover, CdCl₂ significantly increased ERα expression in both OVCAR3 and SKOV3 cell lines compared to control. Melatonin significantly inhibited Cd inducing effect on ERα expression of OVCAR3 and SKOV3 cell. In conclusion, due to the proliferative effect on ovarian cancer cell lines, Cd could play an important role in the etiology of ovarian cancer by inducing cells ERα expression. Furthermore, melatonin has the protective role on Cd-induced cell proliferation by inhibition of ERα expression.

Recent advances on the stimulatory effects of metals in breast cancer

Certain environmental chemicals may accumulate in human serum and tissues eliciting estrogenic and/or carcinogenic effects. Therefore, there is heightened interest in determining whether environmental chemicals may increase the risk for endocrine-related tumors like breast cancer. For instance, metals as cadmium, zinc, copper, iron, nickel and aluminum have been shown to mimic estrogen action. Moreover, the exposure to these chemicals has been reported to stimulate diverse malignancies including breast cancer, which is the most common tumor in women worldwide. In this review, we summarize the epidemiologic and experimental evidence regarding the association between the exposure to some trace elements and breast cancer risk. We also address recent insights on the molecular mechanisms involved by metals in breast tumorigenesis.

Blood cadmium levels associated with short distant metastasis-free survival time in invasive breast cancer

Distant metastasis is strongly associated with poor prognosis of breast cancer. Cadmium (Cd) exposure was previously found associated with breast cancer incidence. We explored the associations of blood cadmium levels (BCLs) and clinicopathologic characteristics with invasive breast cancer distant metastasis. Blood samples were collected and analyzed for BCLs by graphite-furnace atomic absorption spectrometry. Clinicopathologic characteristics, including basic clinical information and tumor characteristics, were obtained from medical records. Breast cancer distant metastasis-free survival (DMFS) time was calculated at follow-up. The associations of BCLs and clinicopathologic characteristics with DMFS time were examined by Kaplan-Meier method and Cox regression analysis, and associations between BCLs and tumor characteristics were also explored. Blood Cd level was positively associated with distant metastasis, clinical stage, BMI, and age. On univariate analysis, older age at diagnosis, family history of breast cancer, high N classification and clinical stage, positivity for human epidermal growth factor receptor 2, and high BCLs were associated with short DMFS time. On multivariate analysis model, older age at diagnosis, family history of breast cancer, high N classification, and BCLs were predictors for breast cancer distant metastasis. BCLs were a risk factor for short DMFS time of invasive breast cancer. BCLs and some clinicopathologic factors affect breast cancer distant metastasis, which needs further epidemiological and experimental studies to confirm.

Cadmium stimulates metastasis-associated phenotype in triple-negative breast cancer cells through integrin and β-catenin signaling

Cadmium (Cd) is a carcinogenic heavy metal which is implicated in breast cancer development. While the mechanisms of Cd-induced breast cancer initiation and promotion have been studied, the molecular processes involved in breast cancer progression remain to be investigated. The purpose of the present study was to evaluate the influence of Cd on metastasis-associated phenotypes, such as cell adhesion, migration, and invasion in triple-negative breast cancer cells. Treatment of MDA-MB-231 cells with 1μM Cd increased cell spreading and cell migration. This was associated with the activation of integrin β1, FAK, Src, and Rac1. Treatment with Cd also inhibited GSK3β activity and induced T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription, indicating the involvement of β-catenin signaling. Furthermore, treatment with 3μM Cd for 4weeks increased the expression of β-catenin and enhanced TCF/LEF-mediated transcription. Furthermore, enhanced expressions of integrins α5 and β1, paxillin, and vimentin indicated that prolonged Cd treatment reorganized the cytoskeleton, which aided malignancy, as evidenced by enhanced matrix metalloprotease 2/9 (MMP2/9) secretion and cell invasion. Prolonged Cd treatment also caused an increase in cell growth. Together, these results indicate that Cd alters key signaling processes involved in the regulation of cytoskeleton to enhance cancer cell migration, invasion, adhesion, and proliferation.

ROS-dependent HMGA2 upregulation mediates Cd-induced proliferation in MRC-5 cells

Cadmium (Cd) is a heavy metal widely found in a number of environmental matrices, and the exposure to Cd is increasing nowadays. In this study, the role of high mobility group A2 (HMGA2) in Cd-induced proliferation was investigated in MRC-5 cells. Exposure to Cd (2μM) for 48h significantly enhanced the growth of MRC-5 cells, increased reactive oxygen species (ROS) production, and induced both mRNA and protein expression of HMGA2. Evidence for Cd-induced reduction of the number of G0/G1 phase cells and an increase in the number of cells in S phase and G2/M phase was sought by flow cytometric analysis. Western blot analysis showed that cyclin D1, cyclin B1, and cyclin E were upregulated in Cd-treated cells. Further study revealed that N-acetyl cysteine (NAC) markedly prevented Cd-induced proliferation of MRC-5 cells, ROS generation, and the increasing protein level of HMGA2. Silencing of HMGA2 gene by siRNA blocked Cd-induced cyclin D1, cyclin B1, and cyclin E expression and reduction of the number of G0/G1 phase cells. Combining, our data showed that Cd-induced ROS formation provoked HMGA2 upregulation, caused cell cycle changes, and led to cell proliferation. This suggests that HMGA2 might be an important biomarker in Cd-induced cell proliferation.

Regulation of therapeutic resistance in cancers by receptor tyrosine kinases

In response to DNA damage lesions due to cellular stress, DNA damage response (DDR) pathways are activated to promote cell survival and genetic stability or unrepaired lesion-induced cell death. Current cancer treatments predominantly utilize DNA damaging agents, such as irradiation and chemotherapy drugs, to inhibit cancer cell proliferation and induce cell death through the activation of DDR. However, a portion of cancer patients is reported to develop therapeutic resistance to these DDR-inducing agents. One significant resistance mechanism in cancer cells is oncogenic kinase overexpression, which promotes cell survival by enhancing DNA damage repair pathways and evading cell cycle arrest. Among the oncogenic kinases, overexpression of receptor tyrosine kinases (RTKs) is reported in many of solid tumors, and numerous clinical trials targeting RTKs are currently in progress. As the emerging trend in cancer treatment combines DNA damaging agents and RTK inhibitors, it is important to understand the substrates of RTKs relative to the DDR pathways. In addition, alteration of RTK expression and their phosphorylated substrates can serve as biomarkers to stratify patients for combination therapies. In this review, we summarize the deleterious effects of RTKs on the DDR pathways and the emerging biomarkers for personalized therapy.