Inhibition of cell proliferation, induction of apoptosis, reactivation of DLC1, and modulation of other gene expression by dietary flavone in breast cancer cell lines

Molecular Responses of the Eukaryotic Cell Line INT407 on the Internalized Campylobacter jejuni-The Other Side of the Coin

Campylobacter jejuni is a zoonotic bacterium with the capacity to invade the epithelial cells during the pathogenic process. Several bacterial factors have been identified to contribute to this process, but our knowledge is still very limited about the response of the host. To reveal the major routes of this response, a whole-transcriptome analysis (WTA) was performed where gene expressions were compared between the 1st and the 3rd hours of internalization in INT407 epithelial cells. From the 41,769 human genes tested, altogether, 19,060 genes were shown through WTA to be influenced to different extents. The genes and regulation factors of transcription (296/1052; 28%), signal transduction (215/1052; 21%), apoptosis (153/1052; 15%), immune responses (97/1052; 9%), transmembrane transport (64/1052; 6%), cell-cell signaling (32/1052; 3%), cell-cell adhesions (29/1052; 3%), and carbohydrate metabolism (28/1052; 3%) were the most affected biological functions. A striking feature of the gene expression of this stage of the internalization process is the activation of both immune functions and apoptosis, which convincingly outlines that the invaded cell faces a choice between death and survival. The seemingly balanced status quo between the invader and the host is the result of a complex process that also affects genes known to be associated with postinfectious pathological conditions. The upregulation of TLR3 (3.79×) and CD36 (2.73×), two general tumor markers, and SERPINEB9 (11.37×), FNDC1 (7.58×), and TACR2 (8.84×), three factors of tumorigenesis, confirms the wider pathological significance of this bacterium.

Ras superfamily GTPase activating proteins in cancer: Potential therapeutic targets?

To search more therapeutic strategies for Ras-mutant tumors, regulators of the Ras superfamily involved in the GTP/GDP (guanosine triphosphate/guanosine diphosphate) cycle have been well concerned for their anti-tumor potentials. GTPase activating proteins (GAPs) provide the catalytic group necessary for the hydrolysis of GTPs, which accelerate the switch by cycling between GTP-bound active and GDP-bound inactive forms. Inactivated GAPs lose their function in activating GTPase, leading to the continuous activation of downstream signaling pathways, uncontrolled cell proliferation, and eventually carcinogenesis. A growing number of evidence has shown the close link between GAPs and human tumors, and as a result, GAPs are believed as potential anti-tumor targets. The present review mainly summarizes the critically important role of GAPs in human tumors by introducing the classification, function and regulatory mechanism. Moreover, we comprehensively describe the relationship between dysregulated GAPs and the certain type of tumor. Finally, the current status, research progress, and clinical value of GAPs as therapeutic targets are also discussed, as well as the challenges and future direction in the cancer therapy.

Immune Effect of Active Components of Traditional Chinese Medicine on Triple-Negative Breast Cancer

Triple-negative breast cancers are heterogeneous, poorly prognostic, and metastatic malignancies that result in a high risk of death for patients. Targeted therapy for triple-negative breast cancer has been extremely challenging due to the lack of expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Clinical treatment regimens for triple-negative breast cancer are often based on paclitaxel and platinum drugs, but drug resistance and side effects from the drugs frequently lead to treatment failure, thus requiring the development of new therapeutic platforms. In recent years, research on traditional Chinese medicine in modulating the immune function of the body has shown that it has the potential to be an effective treatment option against triple-negative breast cancer. Active components of herbal medicines such as alkaloids, flavonoids, polyphenols, saponins, and polysaccharides have been shown to inhibit cancer cell proliferation and metastasis by activating inflammatory immune responses and can modulate tumor-related signaling pathways to further inhibit the invasion of triple-negative breast cancer. This paper reviews the immunomodulatory mechanisms of different herbal active ingredients against triple-negative breast cancer and provides an outlook on the challenges and directions of development for the treatment of triple-negative breast cancer with herbal active ingredients.

A Critical Review on Anticancer Mechanisms of Natural Flavonoid Puerarin

Cancer is one of the prominent global causes of death and the foremost worldwide health concern. Despite unprecedented progress in cancer chemoprevention, a vast number of cancers, however, remain an undefeatable challenge for treatment modalities. Immense therapeutic activities of puerarin contribute to its use in various health disorders. In this review, we explored the potential molecular mechanisms and targets of puerarin, proving its potential as a novel anticancer agent, for future cancer therapy and chemoprevention. Several mechanisms account for anticancer activity of puerarin which includes downregulation of NF-kB signalling pathway, mTOR signalling pathway, PI3K and BCl-2 proteins and upregulation of miR-16, caspase proteins, c- Jun N terminal kinase and extracellular signal-regulated kinase 1/2. These alterations result in inhibition of cancer cell proliferation and/or induction of apoptosis. Understanding the molecular mechanisms involved in chemotherapy and chemoprevention could aid in the more pronounced exploration of puerarin in effective cancer treatment.

DLC1 SAM domain-binding peptides inhibit cancer cell growth and migration by inactivating RhoA

Deleted-in-liver cancer 1 (DLC1) exerts its tumor suppressive function mainly through the Rho-GTPase-activating protein (RhoGAP) domain. When activated, the domain promotes the hydrolysis of RhoA-GTP, leading to reduced cell migration. DLC1 is kept in an inactive state by an intramolecular interaction between its RhoGAP domain and the DLC1 sterile α motif (SAM) domain. We have shown previously that this autoinhibited state of DLC1 may be alleviated by tensin-3 (TNS3) or PTEN. We show here that the TNS3/PTEN-DLC1 interactions are mediated by the C2 domains of the former and the SAM domain of the latter. Intriguingly, the DLC1 SAM domain was capable of binding to specific peptide motifs within the C2 domains. Indeed, peptides containing the binding motifs were highly effective in blocking the C2-SAM domain-domain interaction. Importantly, when fused to the tat protein-transduction sequence and subsequently introduced into cells, the C2 peptides potently promoted the RhoGAP function in DLC1, leading to decreased RhoA activation and reduced tumor cell growth in soft agar and migration in response to growth factor stimulation. To facilitate the development of the C2 peptides as potential therapeutic agents, we created a cyclic version of the TNS3 C2 domain-derived peptide and showed that this peptide readily entered the MDA-MB-231 breast cancer cells and effectively inhibited their migration. Our work shows, for the first time, that the SAM domain is a peptide-binding module and establishes the framework on which to explore DLC1 SAM domain-binding peptides as potential therapeutic agents for cancer treatment.

Screening for the Biomarkers Associated with Myocardial Infarction by Bioinformatics Analysis

We aimed to find novel biomarkers associated with myocardial infarction (MI). The array data of GSE62646 were downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were analyzed with limma package. Functional enrichment analyses were performed by DAVID v6.7 online tool. The micro-RNA-messenger RNA (miRNA-mRNA) pairs were predicted by miRWalk database, and the protein-mRNA interactions were predicted by StarBase. Then, miRNA-mRNA-protein regulatory network was constructed. Antigen processing and presentation were only the pathway enriched by DEG1 set such as KLRC4 (killer cell lectin-like receptor subfamily C, member 4) and KLRC2 (killer cell lectin-like receptor subfamily C, member 2). KLRC4 and KLRC2 were differentially expressed in MI patients. DLC1 (DLC1 Rho GTPase activating protein, degree = 179) was the most significant node in miRNA-mRNA-protein network. EIF4AIII (eukaryotic translation initiation factor 4A3) and FUS (FUS RNA binding protein) were the key proteins that regulated the most DEGs. KLRC4, KLRC2, and DLC1 were the biomarkers and may play important roles in the progression of MI. Furthermore, EIF4AIII and FUS may also be involved in MI progression.

Puerarin suppresses LPS-induced breast cancer cell migration, invasion and adhesion by blockage NF-κB and Erk pathway

BACKGROUND

Chronic inflammation is a major risk factor for the development and metastatic progression of breast cancer. Puerarin has long been used as traditional Chinese medicine, which possesses manifold physiological activities, including anti-inflammation and anti-cancer activities. However, its anti-cancer metastasis activity in breast cancer cell inflammation-mediated have not been studied.

METHODS

Cell viability was detected with Cell Counting Kit (CCK)-8. Transwell migration and invasion assay were performed to evaluate cell migration and invasion, respectively. Enzyme-linked immunosorbent assay (ELISA) was conducted to analysis the expression of inflammatory factor. In addition, mRNA and protein levels of related cytokines were determined by qRT- PCR assay and western blot analysis, respectively.

RESULTS

In this study, puerarin significantly inhibited lipopolysaccharide (LPS)-induced MCF-7 and MDA-MB-231 cell migration, invasion and adhesion. The mRNA and protein levels revealed that puerarin treatment effectively negated the expression of CCR7, CXCR4, MMP-2, MMP-9, ICAM and VCAM in LPS- activated MCF-7 and MDA-MB-231 cells. Further, the expression of inflammatory factor TNF-α and IL-6 in cell culture supernatant remarkably reduced. Finally, the result indicated that puerarin abrogated the NF-κB activation in breast cancer cells stimulated by LPS, which is mediated through inhibition of phosphorylation of p65 and IκBα. Also, puerarin inhibited phosphorylation of Erk in breast cancer cells LPS-induced.

CONCLUSIONS

This present study revealed that puerarin might be a novel therapeutic drug for breast cancer treatment.

Flavonoid C-glucosides Derived from Flax Straw Extracts Reduce Human Breast Cancer Cell Growth In vitro and Induce Apoptosis

Flax straw of flax varieties that are grown for oil production is a by product which represents a considerable biomass source. Therefore, its potential application for human use is of high interest. Our research has revealed that flax straw is rich in flavonoid C-glucosides, including vitexin, orientin, and isoorientin. The objective of this study was to evaluate the cytotoxicity and possible proapoptotic effect of flax straw derived C-glucosides of flavonoids in the human breast adenocarcinoma cell line (MCF-7). The effects of flax straw derived flavonoid C-glucosides on cell proliferation of MCF-7 cells were evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) and sulforhodamine B assays. The expression of apoptosis-related genes was assessed by real-time PCR. Our data revealed that flax C-glucosides as well as pure compounds are cytotoxic toward MCF-7 cells and inhibit their proliferation. Moreover, the induction of apoptosis was correlated with the changes in the mRNA level of pro-apoptotic genes. Increased expression of bax and caspase-7, -8, and -9 and decreased mRNA expression of bcl-2 was observed, whereas the mRNA levels of p53 and mdm2 were not altered. These results clearly demonstrated that flax straw metabolites effectively induced growth inhibition and apoptosis in human breast adenocarcinoma cells.

Zapotin (5,6,2',6'-tetramethoxyflavone) Modulates the Crosstalk Between Autophagy and Apoptosis Pathways in Cancer Cells with Overexpressed Constitutively Active PKCϵ

Autophagy is important in the regulation of survival and death signaling pathways in cancer. PKCϵ revealed high transforming potential and the ability to increase cell migration, invasion, and metastasis. Zapotin (5,6,2',6'-tetramethoxyflavone), a natural flavonoid, showed chemopreventive and anticancer properties. Previously, we reported that downmodulation of induced PKCϵ level by zapotin was associated with decreased migration and increased apoptosis in HeLa cell line containing doxycycline-inducible constitutively active PKCϵ (PKCϵA/E, Ala(159) → Glu). Depending on the genetic and environmental content of cells, autophagy may either precede apoptosis or occur simultaneously. The purpose of this study was to assess the effect of zapotin on autophagy. Increasing concentration of zapotin (from 7.5 µM to 30 µM) caused an inhibition of the formation of autophagosomes and a decline in microtubule-associated protein 1 light chain 3 (LC3) protein levels. The gene expression level of major negative regulator of autophagy was noticeably increased. Moreover, the expression of the pivotal autophagy genes was decreased. These changes were accompanied by alternation in autophagy-related protein levels. In conclusion, our results implied that both the antiautophagic and the proapoptosis effect of zapotin in HeLaPKCϵA/E cells are associated with the protein kinase C epsilon signaling pathway and lead to programmed cell death.

DLC-1 is an independent prognostic marker and potential therapeutic target in hepatocellular cancer

BACKGROUND

The 5-year survival rate of patients with hepatocellular cancer (HCC) was very low because of invasion and metastasis in the early stage. Biomarkers might help predict early occurrence of invasion and metastasis. Accumulating evidence has shown that deleted in liver cancer-1 (DLC1) may be considered as a metastasis suppressor gene in numerous solid and hematological cancers. However, its prognostic role and mechanisms that regulate and coordinate these activities remain poorly understood.

METHODS

With the method of immunohistochemistry, the expression of DLC-1 as well as Rho A, ROCK2, moesin had been characterized in 80 HCC tissues and adjacent noncancerous tissues. The correlation between their expression and their relationships with clinicopathological characteristics of HCC were also investigated. In addition, the prognostic value of DLC1 expression within the tumor tissues was assessed by Cox regression and Kaplan-Meier analysis.

RESULTS

DLC1 expression was significantly lower in HCC tissues than in adjacent noncancerous tissues, and DLC-1 expression was found to be negatively correlated with tumor differentiation, TNM stage and lymph node metastasis. Furthermore, DLC-1 expression was found to inversely correlate with Rho A, ROCK2 and moesin which were all highly expressed in HCC tissues. Kaplan-Meier analysis showed that significantly longer 5-year survival rate was seen in HCC patients with higher DLC1 expression, compared to those with lower expression of DLC1. Multivariate Cox proportional hazard analyses revealed that DLC1 was an independent factor affecting the overall survival probability.

CONCLUSION

DLC1 could be served as a tumor suppressor gene in the progression especially in the invasion and metastasis of HCC. DLC1 perhaps played its role by regulating the expression of Rho A, ROCK2 and moesin. Evaluation of the expression of DLC-1 might be a good prognostic marker for patients with HCC.

GAP-independent functions of DLC1 in metastasis

Metastases are responsible for most cancer-related deaths. One of the hallmarks of metastatic cells is increased motility and migration through extracellular matrixes. These processes rely on specific small GTPases, in particular those of the Rho family. Deleted in liver cancer-1 (DLC1) is a tumor suppressor that bears a RhoGAP activity. This protein is lost in most cancers, allowing malignant cells to proliferate and disseminate in a Rho-dependent manner. However, DLC1 is also a scaffold protein involved in alternative pathways leading to tumor and metastasis suppressor activities. Recently, substantial information has been gathered on these mechanisms and this review is aiming at describing the potential and known alternative GAP-independent mechanisms allowing DLC1 to impair migration, invasion, and metastasis formation.

Anti-carcinogenic effects of the phenolic-rich extract from abnormal Savda Munziq in association with its cytotoxicity, apoptosis-inducing properties and telomerase activity in human cervical cancer cells (SiHa)

BACKGROUND

Abnormal Savda Munziq (ASMq) is a herbal preparation used in Traditional Uighur Medicine for the treatment cancer. The polyphenol is main compounds contained in ASMq preparation responsible for anticancer effect of ASMq.

METHODS

In this study,Real-time quantitative Polymerase Chain Reaction (RT-PCR) assay, MTT assay and flow cytometry were used to investigate the effect of polyphenol of ASMq on cell viability and the potential of the phenolic rich extracts of ASMq to induce apoptosis in human cervical cancer cells SiHa and its effects on telomerase activity were investigated. Cellular morphological change was observed by phase contrast microscopy. The MTT cell viability data revealed that treatment with phenolic rich extracts at 75 ~ 175 μg/ml significantly inhibited the viability and proliferation of cells, and these effects occurred in a concentration-dependent manner and time dependent manner (P < 0.01).

RESULTS

The phenolic rich extracts can induce apoptosis of SiHa cells, can increase the apoptosis rate in a concentration-dependent manner and time dependent manner (P < 0.01). Growth inhibition and apoptosis induction by phenolic rich extracts treatment on SiHa cells was associated with down-regulation of anti-apoptotic Bcl-2 expression and telomerase (P < 0.05) and Survivin expression. In addition, phenolic rich extracts exerted a dose-dependent induction of FHIT expression.

CONCLUSION

These results suggest that phenolic rich extracts may have anti-tumor effects in human cervical cancer through cytotoxicity, apoptosis-inducing properties and telomerase activity.

Flavone inhibits nitric oxide synthase (NOS) activity, nitric oxide production and protein S-nitrosylation in breast cancer cells

As the core structure of flavonoids, flavone has been proved to possess anticancer effects. Flavone's growth inhibitory functions are related to NO. NO is synthesized by nitric oxide synthase (NOS), and generally increased in a variety of cancer cells. NO regulates multiple cellular responses by S-nitrosylation. In this study, we explored flavone-induced regulations on nitric oxide (NO)-related cellular processes in breast cancer cells. Our results showed that, flavone suppresses breast cancer cell proliferation and induces apoptosis. Flavone restrains NO synthesis by does-dependent inhibiting NOS enzymatic activity. The decrease of NO generation was detected by fluorescence microscopy and flow cytometry. Flavone-induced inhibitory effect on NOS activity is dependent on intact cell structure. For the NO-induced protein modification, flavone treatment significantly down-regulated protein S-nitrosylation, which was detected by "Biotin-switch" method. The present study provides a novel, NO-related mechanism for the anticancer function of flavone.

Isoquercitrin inhibits the progression of pancreatic cancer in vivo and in vitro by regulating opioid receptors and the mitogen-activated protein kinase signalling pathway

Pancreatic cancer is a common malignant tumour that affects individuals worldwide. In recent years, the incidence and mortality rates of pancreatic cancer have continuously increased. Currently, the primary clinical treatment methods for pancreatic cancer include surgical resection, chemotherapy and radiotherapy. However, these treatment methods rarely produce satisfactory therapeutic outcomes. Extensive research has also proven that the effective components of several traditional Chinese medicines, particularly flavonoids extracted from plants, have significant antitumour effects. Isoquercitrin, which is one of the flavonoids found in Bidens pilosa extracts, has a significant antitumour effect. However, the antitumour effect of isoquercitrin and its mechanism of action remain unclear. The objective of the present study was to investigate the effect of isoquercitrin on the progression of pancreatic cancer and to further understand the biological characteristics of the participation of isoquercitrin in the progression of pancreatic cancer. In vitro, we found that a therapeutic dose of isoquercitrin significantly inhibited proliferation, promoted apoptosis and induced cell cycle arrest within the G1 phase in pancreatic cancer cells. Isoquercitrin activated caspase-3, -8 and -9 and reduced the mitochondrial membrane potential. In addition, isoquercitrin inhibited the expression level of the δ opioid receptor; however, isoquercitrin had no effect on the κ and µ opioid receptors. Furthermore, isoquercitrin inhibited extracellular signal-regulated kinase (ERK) phosphorylation and promoted c-Jun N-terminal kinase (JNK) phosphorylation. In vivo, we found that a therapeutic dose of isoquercitrin significantly inhibited xenograft growth in nude mice. In summary, the present study demonstrated that isoquercitrin inhibits human pancreatic cancer progression in vivo and in vitro and that its molecular mechanism may be closely related to opioid receptors and to the activation of the mitogen-activated protein kinase (MAPK) signalling pathway.

Deleted in liver cancer-1 (DLC1): an emerging metastasis suppressor gene

While significant progress continues to be made in the early detection and therapeutic management of primary tumors, the incidence of metastatic disease remains the major cause of mortality. Accordingly, the development of novel effective therapies that can ameliorate dissemination and secondary tumor growth are a clinical priority. The identification of genetic and functional alterations in cancer cells that affect factors implicated in the metastatic process is critical for designing preventive and therapeutic strategies. Evidence implicating the protein deleted in liver cancer-1 (DLC1), a Rho GTPase activator, in metastasis has accumulated to a point where DLC1 may be considered as a metastasis suppressor gene. This review presents evidence supporting an anti-metastatic role for DLC1 in several human cancers and discusses the mechanisms contributing to its inhibitory effects. In addition, promising opportunities for therapeutic interventions based on DLC1 function and downstream pathways involved in the metastatic process are considered.

Flavone Induces Cell Death in Human Hepatoma HepG2 Cells

Flavones have received considerable attention because of their antiproliferative properties and selective effects on cancer cells, making them good candidates for use in cancer therapy. In contrast to other flavones, little is known about the effects of the flavone core structure (2-phenyl-4H-1-benzopyran-4one) on cancer cells. Here, we report that flavone induces cell death in human hepatoma HepG2 cells. Furthermore, annexin-V+/PI- and SubG1 populations of HepG2 cells increased after flavone treatment. Exposure of HepG2 to flavone did not result in either cytochrome c release into the cytosol or changes in the mitochondrial membrane potential. Treatment of HepG2 cells with flavone for 24 h reduced the accumulation of intracellular ROS, which correlated with upregulation of Gred, CuZnSOD and MnSOD mRNA levels. Taken together, our results provided useful insights into the mechanism of cell death caused by flavones, in order to evaluate their future application in hepatocarcinoma therapy.

Isoquercitrin inhibits the progression of liver cancer in vivo and in vitro via the MAPK signalling pathway

Liver cancer is a malignant tumour with high morbidity and fatality rates that is common worldwide. At present, the clinical approaches to treating primary liver cancer include partial hepatectomy, systemic or local chemotherapy, radiotherapy, radiofrequency ablative surgery and liver transplantation. However, all of these approaches have shortcomings, including poor prognosis and numerous side-effects. A large number of studies have proven that many effective ingredients in traditional Chinese medicine, particularly the flavonoid compounds extracted from plants, have achieved breakthroughs in terms of enhancing the effects and reducing the toxicity of chemotherapy and radiotherapy, preventing tumour metastasis and relapse after surgery, alleviating the clinical symptoms of advanced tumours, improving the quality of life of the patient with tumours and extending patient long‑term survival. The purpose of the present study was to investigate the impact of isoquercitrin, the flavonoid from Bidens bipinnata L. extract, on the progression of liver cancer and to achieve a deeper understanding of the biological characteristics of isoquercitrin's involvement in the progression of liver cancer. In the in vitro experiments, isoquercitrin was found to strongly inhibit the proliferation of human liver cancer cells, promote the apoptosis of human liver cancer cells, and block the cell cycle in the G1 phase. Isoquercitrin activated caspase-3, -8 and -9, inhibited the expression level of ERK and p38MAPK protein phosphorylation, and promoted the phosphorylation of JNK. Additionally, isoquercitrin reduced the expression level of PKC in human liver cancer cells. In the in vivo experiments, isoquercitrin was also found to significantly inhibit the growth of transplanted tumours in nude mice. The present study confirmed that isoquercitrin could inhibit the progression of human liver cancer in vivo and in vitro, and the molecular mechanism of isoquercitrin may be closely associated with the MAPK and PKC signalling pathways.

Expression of deleted in liver cancer 1 and plasminogen activator inhibitor 1 protein in ovarian carcinoma and their clinical significance

Background

The deleted in liver cancer 1 (DLC1) and plasminogen activator inhibitor 1 (PAI-1) are known to be closely associated with tumor growth and metastasis in several kinds of human tumors. The aim of this study was to investigate the expression of DLC1 and PAI-1 in ovarian carcinoma, and evaluate their relations with the prognosis of ovarian carcinoma.

Methods

Immunohistochemical staining and Western blot were used to examine the expressions of DLC1 and PAI-1 protein in 25 specimens normal ovarian tissues, 52 specimens of serous cystadenocarcinoma tissues and 23 specimens of mucinous cystadenocarcinoma tissues. Chi-square test, Logistic regression and Partial Correlate analysis were performed to evaluate the association between DLC1 and PAI-1 with clinicopathological characteristics. Overall survival was estimated by Kaplan-Meier curves and multivariate Cox analysis. The relationships between DLC1 and PAI-1 protein expression were analyzed by Pearson’s correlation coefficient.

Results

The expression of DLC1 protein in ovarian carcinoma tissues was significantly lower than that in normal ovarian tissues, but it was converse for PAI-1. In ovarian carcinoma, the expression of DLC1 was significantly associated with advanced FIGO stage, ascites and positive lymph node metastasis, whereas PAI-1 protein was closely related with advanced FIGO stage, poor histological differentiation and lymph node metastasis. The expression of DLC1 was negatively correlated with PAI-1 in ovarian carcinoma. Ovarian cancer patients with negative expression of DLC1 and positive expression of PAI-1 had the worst overall survival time compared to other patients.

Conclusions

The expression of DLC1 and PAI-1 were closely related with the metastasis and invasion of ovarian carcinoma, only the combination of DLC1 and PAI-1 could serve as an independent prognostic factor of ovarian carcinoma.

Diet, nutrients, phytochemicals, and cancer metastasis suppressor genes

The major factor in the morbidity and mortality of cancer patients is metastasis. There exists a relative lack of specific therapeutic approaches to control metastasis, and this is a fruitful area for investigation. A healthy diet and lifestyle not only can inhibit tumorigenesis but also can have a major impact on cancer progression and survival. Many chemicals found in edible plants are known to inhibit metastatic progression of cancer. While the mechanisms underlying antimetastatic activity of some phytochemicals are being delineated, the impact of diet, dietary components, and various phytochemicals on metastasis suppressor genes is underexplored. Epigenetic regulation of metastasis suppressor genes promises to be a potentially important mechanism by which dietary components can impact cancer metastasis since many dietary constituents are known to modulate gene expression. The review addresses this area of research as well as the current state of knowledge regarding the impact of diet, dietary components, and phytochemicals on metastasis suppressor genes.

Identification of flavone glucuronide isomers by metal complexation and tandem mass spectrometry: regioselectivity of uridine 5'-diphosphate-glucuronosyltransferase isozymes in the biotransformation of flavones

Flavone glucuronide isomers of five flavones (chrysin, apigenin, luteolin, baicalein, and scutellarein) were differentiated by collision-induced dissociation of [Co(II) (flavone-H) (4,7-diphenyl-1,10-phenanthroline)(2)](+) complexes. The complexes were generated via postcolumn addition of a metal-ligand solution after separation of the glucuronide products generated upon incubation of each flavone with an array of uridine 5'-diphosphate (UDP)-glucuronosyltransferase (UGT) isozymes. Elucidation of the glucuronide isomers allowed a systematic investigation of the regioselectivity of 12 human UGT isozymes, including 8 UGT1A and 4 UGT2B isozymes. Glucuronidation of the 7-OH position was the preferred site for all the flavones except for luteolin, which possessed adjacent hydroxyl groups on the B ring. For all flavones and UGT isozymes, glucuronidation of the 5-OH position was never observed. As confirmed by the metal complexation/MS/MS strategy, glucuronidation of the 6-OH position only occurred for baicalein and scutellarein when incubated with three of the UGT isozymes.

Correlation of DLC1 gene methylation with oncogenic PIK3CA mutations in extramammary Paget's disease

Extramammary Paget's disease is a rare cutaneous malignant neoplasm. The genetic and epigenetic mechanisms underlying its pathology remain unknown. In this study, we investigated the expression levels, and mutation and methylation status of a common tumor suppressor gene, deleted in liver cancer 1 (DLC1), and an oncogene, PIK3CA, in tumor (n=132) and normal tissues (n=20) from unrelated patients. The presence of epigenetic and genetic lesions was then correlated to the patient pathology data to determine the potential role of these genes in extramammary Paget's disease etiology and progression. The DLC1 gene was found to be downregulated in 43 (33%) tumors, as compared with immunohistochemistry results from normal tissues. Methylation-sensitive, high-resolution melting analysis indicated that the DLC1 promoter was hypermethylated in 51 (39%) extramammary Paget's disease tumors. This hypermethylation was associated with significantly decreased DLC1 levels (P=0.011), and had a strong positive correlation with advanced age (P=0.002). PIK3CA mutations were detected by direct sequencing in 32 (24%) tumors, the majority of which were invasive. Furthermore, PIK3CA mutations significantly correlated with DLC1 hypermethylation. Thus, aberrant DLC1 methylation and PIK3CA mutations may have important roles in extramammary Paget's disease pathogenesis, and may represent potential molecular targets for therapy.

Role of DLC1 tumor suppressor gene and MYC oncogene in pathogenesis of human hepatocellular carcinoma: potential prospects for combined targeted therapeutics (review)

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death, and its incidence is increasing worldwide in an alarming manner. The development of curative therapy for advanced and metastatic HCC is a high clinical priority. The HCC genome is complex and heterogeneous; therefore, the identification of recurrent genomic and related gene alterations is critical for developing clinical applications for diagnosis, prognosis and targeted therapy of the disease. This article focuses on recent research progress and our contribution in identifying and deciphering the role of defined genetic alterations in the pathogenesis of HCC. A significant number of genes that promote or suppress HCC cell growth have been identified at the sites of genomic reorganization. Notwithstanding the accumulation of multiple genetic alterations, highly recurrent changes on a single chromosome can alter the expression of oncogenes and tumor suppressor genes (TSGs) whose deregulation may be sufficient to drive the progression of normal hepatocytes to malignancy. A distinct and highly recurrent pattern of genomic imbalances in HCC includes the loss of DNA copy number (associated with loss of heterozygosity) of TSG-containing chromosome 8p and gain of DNA copy number or regional amplification of protooncogenes on chromosome 8q. Even though 8p is relatively small, it carries an unusually large number of TSGs, while, on the other side, several oncogenes are dispersed along 8q. Compelling evidence demonstrates that DLC1, a potent TSG on 8p, and MYC oncogene on 8q play a critical role in the pathogenesis of human HCC. Direct evidence for their role in the genesis of HCC has been obtained in a mosaic mouse model. Knockdown of DLC1 helps MYC in the induction of hepatoblast transformation in vitro, and in the development of HCC in vivo. Therapeutic interventions, which would simultaneously target signaling pathways governing both DLC1 and MYC functions in hepatocarcinogenesis, could result in progress in the treatment of liver cancer.

The tetramethoxyflavone zapotin selectively activates protein kinase C epsilon, leading to its down-modulation accompanied by Bcl-2, c-Jun and c-Fos decrease

Zapotin, a tetramethoxyflavone, is a natural compound with a wide spectrum of activities in neoplastic cells. Protein kinase C epsilon (PKCε) has been shown to be oncogenic, with the ability to increase cell migration, invasion and survival of tumor cells. Here we report that zapotin inhibits cell proliferation. In wild-type HeLa cells with basal endogenous expression of PKCε, the IC(50) was found to be 17.9 ± 1.6 μM. In HeLa cells overexpressing doxycycline-inducible constitutively active PKCε (HeLaPKCεA/E), the IC(50) was 7.6 ± 1.3 μM, suggesting that PKCε enhances the anti-proliferative effect of zapotin. Moreover, we found that zapotin selectively activated PKCε in comparison with other PKC family members, but attenuated doxycycline-induced PKCε expression. As a result of zapotin treatment for 6, 12 and 24h, the doxycycline-induced levels of the two differently phosphorylated PKCε forms (87 kDa and 95 kDa) were decreased. Migration assays revealed that increasing concentrations of zapotin (from 3.5 to 15 μM) decreased migration of HeLaPKCεA/E cells. Furthermore, zapotin significantly increased the fraction of apoptotic cells in doxycycline-induced (HeLaPKCεA/E) cells after 24h and decreased the levels of Bcl-2, c-Jun, c-Fos. This was accompanied by a degradation of PARP-1. In summary, activation of PKCε and down-modulation of the induced PKCε level by zapotin were associated with decreased migration and increased apoptosis. These observations are consistent with the previously reported chemopreventive and chemotherapeutic action of zapotin.

Loss of DLC1 is an independent prognostic factor in patients with oral squamous cell carcinoma

Deleted in liver cancer (DLC1), a Rho GTPase-activating protein, was observed to be differentially expressed in oral squamous cell carcinoma in comparison with normal tissues using tissue proteomics. In the current study, we investigated the clinical significance of loss of DLC1 expression in different stages of development of oral squamous cell carcinoma to determine its potential as a biomarker for oral dysplasia and prognosis of oral squamous cell carcinoma. Immunohistochemical analysis of DLC1 expression was carried out in oral squamous cell carcinoma patients (n=214), dysplasia (n=51), hyperplastic squamous mucosa (n=45), and histologically normal oral tissues (n=80), and correlated with clinicopathological parameters and disease prognosis over 91 months for oral squamous cell carcinomas. Loss of DLC1 expression was observed in oral squamous cell carcinoma (64%), oral dysplasia (31%), hyperplastic squamous mucosa (22%), and normal mucosa (16%). Significant loss of DLC1 expression was observed in oral squamous cell carcinomas as compared with dysplasia (P<0.001, odds ratio=3.8, 95% CI=2.0-7.3), suggesting it may be an important event involved in cancer progression. Among oral squamous cell carcinomas, the loss of DLC1 expression was significantly associated with poor prognosis (P=0.021, hazards ratio (HR)=1.8, 95% CI=1.1-2.9). Multivariate analysis revealed loss of DLC1 (P=0.023, HR=2.1, 95% CI=1.2-3.9) and histopathological grade (P=0.015, HR=1.7, 95% CI=1.1-2.7) to be independent predictors for disease-free survival in oral squamous cell carcinoma patients in comparison with known prognostic factors, viz. tumor stage, nodal status, and overall stage. Loss of DLC1 expression emerged as an important biomarker for predicting patients diagnosed with oral dysplasia at high risk of transformation upon future validation in longitudinal studies. Loss of DLC1 expression is a poor prognostic marker for oral squamous cell carcinoma patients.

Caffeic acid induces apoptosis in human cervical cancer cells through the mitochondrial pathway

OBJECTIVE

The anti-proliferation effect of caffeic acid (3,4-dihydroxycinnamic acid), isolated from Ocimum gratissimum Linn, on human cervical cancer cells (HeLa cells) was examined to elucidate the associated mechanism and death mode.

MATERIALS AND METHODS

Flow cytometry showed that caffeic acid treatment results in dramatically increased apoptosis of HeLa cells. Western blot analysis revealed that caffeic acid activates various processed caspases.

RESULTS

Caffeic acid significantly reduced proliferation of HeLa cells in a concentration-dependent manner. Morphological evidence of apoptosis, including nuclei fragmentation was clearly observed 24 and 48 hours after exposure to caffeic acid (1 mM and 10 mM) by flow cytometry. Time-dependent inhibition was also observed. Caffeic acid decreased levels of uncleaved caspase-3 and Bcl-2, and induced cleaved caspase-3 and p53.

CONCLUSION

Caffeic acid induces apoptosis by inhibiting Bcl-2 activity, leading to release of cytochrome c and subsequent activation of caspase-3, indicating that caffeic acid induces apoptosis via the mitochondrial apoptotic pathway. This also suggests that caffeic acid has a strong anti-tumor effect and may be a promising chemopreventive or chemotherapeutic agent.

Chemopreventive effects of β-ionone and geraniol during rat hepatocarcinogenesis promotion: distinct actions on cell proliferation, apoptosis, HMGCoA reductase, and RhoA

Chemopreventive activities of the dietary isoprenoids β-ionone (βI) and geraniol (GOH) were evaluated during the promotion phase of hepatocarcinogenesis. Over 5 consecutive weeks, rats received daily 16 mg/100 g body weight (b.w.) of βI (βI group), 25 mg/100 g b.w. of GOH (GOH group), or only corn oil (CO group, controls). Compared to the CO group, the following was observed: only the βI group showed a decrease in the mean number of visible hepatocyte nodules (P<.05); βI and GOH groups had reduced mean number of persistent preneoplastic lesions (pPNLs) (P<.05), but no differences regarding number of remodeling PNL (rPNLs) were observed; only the βI group exhibited smaller rPNL size and percentage of liver sections occupied by pPNLs (P<.05), whereas the GOH group displayed a smaller percentage of liver sections occupied by rPNLs (P<.05); a trend was observed in the βI group, which showed reduced cell proliferation of pPNLs (P<.10), and the GOH group had increased apoptosis in pPNLs and rPNLs (P<.05); only the βI group displayed reduced total plasma cholesterol concentrations (P<.05) and increased hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase mRNA levels (P<.05); only the GOH group had lower hepatic membrane RhoA protein levels (P<.05); both the βI- and GOH-treated groups had higher hepatic concentrations of βI and GOH, respectively (P<.05). Given these data, βI and GOH show promising chemopreventive effects during promotion of hepatocarcinogenesis by acting through distinct mechanism of actions: βI may inhibit cell proliferation and modulate HMGCoA reductase, and GOH can induce apoptosis and inhibit RhoA activation.

N-acetyl-D-glucosamine-coated polyamidoamine dendrimer promotes tumor-specific B cell responses via natural killer cell activation

N-acetyl-D-glucosamine-coated polyamidoamine dendrimer (GN8P), exerting high binding affinity to rodent recombinant NKR-P1A and NKR-P1C activating proteins, was shown previously to delay the development of rat colorectal carcinoma as well as mouse B16F10 melanoma, and to potentiate antigen-specific antibody formation in healthy C57BL/6 mice via NK cell stimulation. In this study, we investigated whether GN8P also modulates tumor-specific B cell responses. Serum anti-B16F10 melanoma IgG levels, IgG2a mRNA expression, antibody dependent cell-mediated cytotoxicity (ADCC), and counts of plasma as well as antigen presenting B cells were evaluated in tumor-bearing C57BL/6 mice treated with GN8P and in respective controls. To reveal the mechanism of GN8P effects, the synthesis of interferon-gamma (IFN-γ) and interleukin-4 (IL-4), cytokines involved in regulation of immunoglobulin class switch, was determined. The GN8P treatment significantly elevated IgG, and particularly IgG2a, response against B16F10 melanoma, which led to augmented ADCC reaction. The significant increase in production of IFN-γ, which is known to support IgG2a secretion, was observed solely in NK1.1 expressing cell populations, predominantly in NK cells. Moreover, GN8P raised the number of plasma cells, and promoted antigen presenting capacity of I-A/I-E-positive B lymphocytes by up-regulation of their CD80 and CD86 co-stimulatory molecule expression. These results indicate that GN8P-induced enhancement of tumor-specific antibody formation is triggered by NK cell activation, and contributes to complexity of anticancer immune response involving lectin-saccharide interaction.

DLC-1 as a modulator of proliferation, apoptosis and migration in Burkitt's lymphoma cells

Deleted in liver cancer-1(DLC-1) gene expression is frequently down-regulated or deleted in many types of human cancer. To evaluate whether DLC-1 could be a therapeutic target for non-Hodgkin lymphoma (NHL), we examined the expressions of DLC-1 in Burkitt's lymphoma (BL) cell lines and tested the effects of DLC-1 on cellular growth and migration in BL cells. DLC-1 expression was not detectable in two human BL cell lines, Raji and Daudi, by reverse transcription-PCR. The transfer of DLC-1 into Raji and Daudi cell lines caused a significant inhibition in cell proliferation. This inhibitory effect on cell proliferation in BL cell lines was accompanied by induction of apoptosis. Furthermore, restoration of DLC-1 expression in BL cells had a significant inhibitory effect on migration. Our findings suggest that DLC-1 may play an important role in lymphoma by acting as a bona fide new tumor suppressor gene.

New synthetic flavone derivatives induce apoptosis of hepatocarcinoma cells

Natural flavonoids have broad biological activity, including anticancer. In this study, a series of novel flavone derivatives were synthesized with the substitutions of chlorine, isopropyl, methoxy, and nitro groups on the benzene ring of flavone skeleton to develop effective anticancer agents. Antiproliferative assays showed that the synthesized chemicals possess notable activity against hepatocarcinoma cells (HepG-2); in particular, the compound 6f with chlorine and dimethoxy modifications at the two benzene rings showed an IC(50) at 1.1 microM to HepG-2. The 6f also displayed marked anticancer activity towards a panel of cancer cells, including nasopharyngeal carcinoma cells (CNE-2 and CNE-1), breast adenocarcinoma cell (MCF-7), and epithelial carcinoma cells (Hela). Exposing HepG-2 cells to compound 6f at 10 microM induced chromatin condensation, nuclear disassembly, and DNA fragmentation. In 6f-treated HepG-2 cells, the sub-G(0) population was remarkably increased; and in these cells, both caspase-8 and caspase-9 activity was significantly increased, which in turn activated caspase-3. In addition, proapoptotic Bax was upregulated by compound 6f while the antiapoptotic Bcl-2 was downregulated. Taken together, our data suggest that the new flavonoid derivative 6f triggers apoptosis through both death-receptor and mitochondria-dependent intrinsic pathways, being a potent therapeutic agent against hepatocarcinoma.

Dietary quercetin combining intratumoral doxorubicin injection synergistically induces rejection of established breast cancer in mice

Dietary ingredients can decrease the risk of a variety of human cancers. Quercetin (3,3',4',5,7-pentahydroxyflavone) has a long history of consumption as part of the normal human diet and is able to induce growth inhibition in multiple cancer cells. In an attempt to generate more potent therapeutic effect for breast cancer, we have designed a combinative regimen of dietary quercetin with intratumoral doxorubicin injection and evaluated their anti-tumor activity in established breast cancer mouse model. Interestingly, dietary quercetin combining intratumoral doxorubicin injection synergistically induced potent rejection of 4T1 breast cancer and led to long-term, tumor-free survival in mice bearing established breast tumor, whereas quercetin or doxorubicin alone failed to cure tumor-bearing mice. Treatment with quercetin promoted lymphocyte proliferation and regulated Th1/Th2 cytokine imbalance. Combination of quercetin and intratumoral doxorubicin injection further induced a persistent T-cell tumor-specific responses. Based on these results, the combination of quercetin as a food supplement adjunctive with intratumoral doxorubicin chemotherapy may represent a novel and highly effective strategy for inducing immune responses against tumors.

Proteomic analysis of differentially expressed proteins in hepatitis B virus-related hepatocellular carcinoma tissues

BACKGROUND

Hepatocellular carcinoma (HCC), a major cause of cancer death in China, is preceded by chronic hepatitis and liver cirrhosis (LC). Although hepatitis B virus (HBV) has been regarded as a clear etiology of human hepatocarcinogenesis, the mechanism is still needs to be further clarified. In this study, we used a proteomic approach to identify the differential expression protein profiles between HCC and the adjacent non-tumorous liver tissues.

METHODS

Eighteen cases of HBV-related HCC including 12 cases of LC-developed HCC and 6 cases of chronic hepatitis B (CHB)-developed HCC were analyzed by two-dimensional electrophoresis (2-DE) combined with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), and the results were compared to those of paired adjacent non-tumorous liver tissues.

RESULTS

A total of 17 differentially expressed proteins with diverse biological functions were identified. Among these, 10 proteins were up-regulated, whereas the other 7 proteins were down-regulated in cancerous tissues. Two proteins, c-Jun N-terminal kinase 2 and ADP/ATP carrier protein were found to be up-regulated only in CHB-developed HCC tissues. Insulin-like growth factor binding protein 2 and Rho-GTPase-activating protein 4 were down-regulated in LC-developed and CHB-developed HCC tissues, respectively. Although 11 out of these 17 proteins have been already described by previous studies, or are already known to be involved in hepatocarcinogenesis, this study revealed 6 new proteins differentially expressed in HBV-related HCC.

CONCLUSION

These findings elucidate that there are common features between CHB-developed HCC and LC-developed HCC. The identified proteins are valuable for studying the hepatocarcinogenesis, and may be potential diagnostic markers or therapeutic targets for HBV-related HCC.

Overexpression of DLC-1 induces cell apoptosis and proliferation inhibition in the renal cell carcinoma

The lack of effective anti-tumor therapy for renal cell carcinoma (RCC) has stimulated the search for novel target whose inhibition could block tumorigenesis. Recently, reduced DLC-1 has been shown to be associated with aggressive and highly metastatic renal cell carcinoma. In this study, the biological role of DLC-1 on cell growth, migration and cell cycle progression in RCC cells was investigated. Over-expression of DLC-1 was associated with a marked inhibition of cell growth (P<0.01). The inhibitory effect was partly due to the induction of apoptosis and cell cycle arrest in G(0)/G(1) accompanied by up-regulation of the intracellular signal proteins of p27 and down-regulation of cyclin D1 and cyclin E. Furthermore, DLC-1 induced FAK dephosphorylation of focal adhesion proteins inhibited cell migration (P<0.05). Decreased DLC-1 expression strongly correlated with proliferative activity, as indicated by the elevated levels of Ki67. Restoration of DLC-1 expression in RCC cells led to Bcl-2 and caspase-3 mediated apoptosis as well as attenuated the ability of the cells to form RCC tumors in athymic nude mice (P<0.05). Taken together, these results suggest that DLC-1 plays a crucial role in signal transduction pathway regulating the cell proliferation, migration, and carcinogenesis of human RCC.

Inhibition of overexpressed CDC-25.1 phosphatase activity by flavone in Caenorhabditis elegans

We previously reported that flavone induces embryonic lethality in Caenorhabditis elegans, which appeared to be the result of cell cycle arrest during early embryogenesis. To test this possibility, here we examined whether flavone inhibits the activity of a key cell cycle regulator, CDC-25.1 in C. elegans. A gain-of-function cdc-25.1 mutant, rr31, which exhibits extra cell divisions in intestinal cells, was used to test the inhibitory effects of flavone on CDC-25 activity. Flavone inhibited the extra cell divisions of intestinal cells in rr31, and modifications of flavone reduced the inhibitory effects. The inhibitory effects of flavone on CDC-25.1 were partly, if not completely, due to transcriptional repression.

High expression of alpha 2, 3-linked sialic acid residues is associated with the metastatic potential of human gastric cancer

BACKGROUND

Sialic acid, as a terminal saccharide residue on cell surface glycoconjugates, plays an important role in a variety of biological processes. However, the precise nature of the molecules in gastric cancers has not been unveiled nor documented to be of clinical relevance. Herein, we measured the expression of alpha 2, 3-linked sialic acid residues by using a specific lectin as well as the potential of invasion and metastasis of gastric cancer was analyzed.

METHODS

The expression of alpha 2, 3-linked sialic acid residues in 100 cases of gastric cancer samples was evaluated using Maackia amurensis leukoagglutinin (MAL) histochemical staining analysis. The assays of cytochemical staining and flow cytometry were employed to determine the MAL positive cells in the gastric cancer cell lines. The activities of invasion and migration were evaluated using the assays of cell adhesion and transwell chamber.

RESULTS

The staining of MAL in gastric cancer tissues showed that high levels of alpha 2, 3-linked sialic acid residues were closely associated with the invasive depth (P=0.0003) and lymph node metastasis (P=0.0441). In gastric adenocarcinoma cell lines, SGC-7901, the highly metastatic cell line, displayed the most positive reaction with MAL among the selected cell lines. The potential of invasion and migration was confirmed using the assays of adhesion and transwell chamber that SGC-7901 exhibited the high activity of adhesion to extracellular matrix (ECM) and penetration to Matrigel.

CONCLUSION

These results suggested that high level of alpha 2, 3-linked sialic acid residues was associated with metastatic potential of gastric cancer cells.

Adenovirus-mediated restoration of expression of the tumor suppressor gene DLC1 inhibits the proliferation and tumorigenicity of aggressive, androgen-independent human prostate cancer cell lines: prospects for gene therapy

Our recent study showing highly recurrent loss of function of DLC1 (deleted in liver cancer 1), a tumor suppressor gene in primary prostate carcinoma (PCA), implicates this gene in the pathogenesis of this disease. To evaluate the response of PCA to oncosuppressive activity of DLC1, we examined now the effects of adenoviral vector for human DLC1 transduction into the DLC1-deficient, androgen-independent (AI) and aggressive human PCA cell lines PC-3 and C4-2-B2. Adenovirus-mediated restoration of DLC1 expression inhibited the proliferation, invasiveness and anchorage-independent growth of PC-3 and C4-2-B2 cells in vitro as well as the tumorigenicity of PC-3 cells in nude mice. It also induced cell-cycle arrest, inhibited the activation of RhoA and the formation of actin stress fibers. DLC1 induced apoptosis in C4-2-B2 cells, whereas it did not elicit such an effect in PC-3 cells. The abundance of the antiapoptotic protein Bcl-2 was greater in PC-3 cells than in C4-2-B2 cells, and PC-3 cells were rendered sensitive to DLC1-induced apoptosis by treatment with the Bcl-2 inhibitor HA14-1. These results suggest that adenovirus-mediated DLC1 transfer, alone or together with other agents, such as inhibitors of Bcl-2 or histone deacetylase, might prove effective in the treatment of aggressive, AI-PCA.

DLC-1:a Rho GTPase-activating protein and tumour suppressor

The deleted in liver cancer 1 (DLC-1) gene encodes a GTPase activating protein that acts as a negative regulator of the Rho family of small GTPases. Rho proteins transduce signals that influence cell morphology and physiology, and their aberrant up-regulation is a key factor in the neoplastic process, including metastasis. Since its discovery, compelling evidence has accumulated that demonstrates a role for DLC-1 as a bona fide tumour suppressor gene in different types of human cancer. Loss of DLC-1 expression mediated by genetic and epigenetic mechanisms has been associated with the development of many human cancers, and restoration of DLC-1 expression inhibited the growth of tumour cells in vivo and in vitro. Two closely related genes, DLC-2 and DLC-3, may also be tumour suppressors. This review presents the current status of progress in understanding the biological functions of DLC-1 and its relatives and their roles in neoplasia.

Characterization of a novel tumor-suppressor gene PLC delta 1 at 3p22 in esophageal squamous cell carcinoma

Deletion of 3p is one of the most frequent chromosomal alterations in many solid tumors, including esophageal squamous cell carcinoma (ESCC), suggesting the existence of one or more tumor-suppressor genes at 3p. Recently, our loss of heterozygosity study revealed that 3p22 was frequently deleted in ESCC and a candidate tumor-suppressor gene (TSG), phospholipase C-delta 1 (PLC delta 1), was identified within the 3p22 region. In this study, absent expression of PLC delta 1 was detected in 26 of 50 (52%) primary ESCCs and 4 of 9 (44.4%) ESCC cell lines, which was significantly associated with DNA copy number loss and promoter hypermethylation (P < 0.05). Functional studies showed that PLC delta 1 was able to suppress both in vitro and in vivo tumorigenic ability of ESCC cells, including foci formation, colony formation in soft agar, and tumor formation in nude mice. The tumor-suppressive mechanism of PLC delta 1 was associated with its role in the cell cycle arrest at the G(1)-S checkpoint by up-regulation of p21 and down-regulation of phosphorylated Akt (Ser(473)). In addition, down-regulation of PLC delta 1 protein was significantly correlated with ESCC metastasis (P = 0.014), which was associated with its function in increasing cell adhesion and inhibiting cell mobility. Taken together, our results suggest that PLC delta 1 plays an important suppressive role in the development and progression of ESCC.

Deleted in liver cancer-1 (DLC-1): a tumor suppressor not just for liver

Deleted in liver cancer 1 (DLC-1), as its name implied, was originally isolated as a potential tumor suppressor gene often deleted in hepatocellular carcinoma. Further studies have indicated that down-expression of DLC-1 either by genomic deletion or DNA methylation is associated with a variety of cancer types including lung, breast, prostate, kidney, colon, uterus, ovary, and stomach. Re-expression of DLC-1 in cancer cells regulates the structure of actin cytoskeleton and focal adhesions and significantly inhibits cell growth, supporting its role as a tumor suppressor. This tumor suppressive function relies on DLC-1's RhoGTPase activating protein (RhoGAP) activity and steroidogenic acute regulatory (StAR)-related lipid transfer (START) domain, as well as its focal adhesion localization, which is recruited by the Src Homology 2 (SH2) domains of tensins in a phosphotyrosine-independent fashion. Therefore, the expression and subcellular localization of DLC-1 could be a useful molecular marker for cancer prognosis, whereas DLC-1 and its downstream signaling molecules might be therapeutic targets for the treatment of cancer.