Direct interaction with and activation of p53 by SMAR1 retards cell-cycle progression at G2/M phase and delays tumor growth in mice

SMAR1 inhibits proliferation, EMT and Warburg effect of bladder cancer cells by suppressing the activity of the Wnt/β-catenin signaling pathway

This study aimed to investigate the effects of scaffold matrix attachment region binding protein 1 (SMAR1) on the development of bladder cancer (BCa). SMAR1 expression in paired tumor and corresponding adjacent normal tissues from 55 BCa patients was detected by quantitative reverse transcription-polymerase chain reaction. BCa cells were transfected to regulate SMAR1 expression. BCa cells were treated with XAV-939, LiCl and 2-deoxyglucose. The effect of SMAR1 on the viability, proliferation, migration, invasion and Warburg effect of BCa cells was researched by counting kit-8, colony formation assay, Transwell and aerobic glycolysis assays. Western blot was performed to detect protein expression. BCa cell growth in vivo was recorded in nude mice. Immunohistochemical staining was performed for clinical and xenografted tumor tissue specimens. SMAR1 expression was down-regulated in BCa patients, associating with worse prognoses. SMAR1 knockdown enhanced the viability, proliferation, migration, invasion, EMT and Warburg effect of BCa cells. The opposite effect was found in the SMAR1 overexpression BCa cells. XAV-939 treatment reversed the elevation of β-catenin, c-Myc and Cyclin D1 proteins expression and Warburg effect in Bca cells post-SMAR1 knockdown. LiCl treatment abrogated the inhibition of β-catenin, c-Myc and Cyclin D1 proteins expression and Warburg effect proteins due to SMAR1 overexpression in BCa cells. SMAR1 overexpression inhibited the growth of BCa cells in vivo. SMAR1 might suppress the Wnt/β-catenin signaling pathway activity to inhibit the progression of BCa. It might be an effective treatment target for BCa.

The transcriptomic landscape of elderly acute myeloid leukemia identifies B7H3 and BANP as a favorable signature in high-risk patients

Acute myeloid leukemia (AML) in the elderly remains a clinical challenge, with a five-year overall survival rate below 10%. The current ELN 2017 genetic risk classification considers cytogenetic and mutational characteristics to stratify fit AML patients into different prognostic groups. However, this classification is not validated for elderly patients treated with a non-intensive approach, and its performance may be suboptimal in this context. Indeed, the transcriptomic landscape of AML in the elderly has been less explored and it might help stratify this group of patients. In the current study, we analyzed the transcriptome of 224 AML patients > 65 years-old at diagnosis treated in the Spanish PETHEMA-FLUGAZA clinical trial in order to identify new prognostic biomarkers in this population. We identified a specific transcriptomic signature for high-risk patients with mutated TP53 or complex karyotype, revealing that low expression of B7H3 gene with high expression of BANP gene identifies a subset of high-risk AML patients surviving more than 12 months. This result was further validated in the BEAT AML cohort. This unique signature highlights the potential of transcriptomics to identify prognostic biomarkers in in elderly AML.

Effect of nanovesicular surface-functionalization via chitosan and/or PEGylation on cytotoxicity of tamoxifen in induced-breast cancer model

AIMS

The effect of surface-modification of Tamoxifen (Tam)-loaded-niosomes on drug cytotoxicity and bio-distribution, via functionalization with chitosan and/or PEGylation, was investigated.

MATERIALS AND METHODS

Tam-loaded hybrid-nanocarriers (Tam-loaded niosomes, chitosomes, PEGylated niosomes, and PEGylated chitosomes) were formulated and characterized.

KEY FINDINGS

Chitosanization with/without PEGylation proved to selectively enhance Tam-release at the cancerous-acidic micromilieu. Cytotoxic activity study showed that Tam-loaded PEGylated niosomes had a lower IC₅₀ value on MCF-7 cell line (0.39, 0.35, and 0.27 times) than Tam-loaded PEGylated chitosomes, Tam-loaded niosomes, and Tam-loaded chitosomes, respectively. Cell cycle analysis showed that PEGylation and/or Chitosanization significantly impact Tam efficiency in inducing apoptosis, with a preferential influence of PEGylation over chitosanization. The assay of Annexin-V/PI double staining revealed that chitosanized-nanocarriers had a significant role in increasing the incidence of apoptosis over necrosis. Besides, PEGylated-nanocarriers increased apoptosis, as well as total death and necrosis percentages more than what was shown from free Tam. Moreover, the average changes in both Bax/Bcl-2 ratio and Caspase 9 were best improved in cells treated by Tam-loaded PEGylated niosomes over all other formulations. The in-vivo study involving DMBA-induced-breast cancer rats revealed that PEGylation made the highest tumor-growth inhibition (84.9 %) and breast tumor selectivity, while chitosanization had a lower accumulation tendency in the blood (62.3 ng/ml) and liver tissues (103.67 ng/ml). The histopathological specimens from the group treated with Tam-loaded PEGylated niosomes showed the best improvement over other formulations.

SIGNIFICANCE

All these results concluded the crucial effect of both PEGylation and chitosan-functionalization of Tam-loaded niosomes in enhancing effectiveness, targetability, and safety.

Banp regulates DNA damage response and chromosome segregation during the cell cycle in zebrafish retina

Btg3-associated nuclear protein (Banp) was originally identified as a nuclear matrix-associated region (MAR)-binding protein and it functions as a tumor suppressor. At the molecular level, Banp regulates transcription of metabolic genes via a CGCG-containing motif called the Banp motif. However, its physiological roles in embryonic development are unknown. Here, we report that Banp is indispensable for the DNA damage response and chromosome segregation during mitosis. Zebrafish banp mutants show mitotic cell accumulation and apoptosis in developing retina. We found that DNA replication stress and tp53-dependent DNA damage responses were activated to induce apoptosis in banp mutants, suggesting that Banp is required for regulation of DNA replication and DNA damage repair. Furthermore, consistent with mitotic cell accumulation, chromosome segregation was not smoothly processed from prometaphase to anaphase in banp morphants, leading to a prolonged M-phase. Our RNA- and ATAC-sequencing identified 31 candidates for direct Banp target genes that carry the Banp motif. Interestingly, a DNA replication fork regulator, wrnip1, and two chromosome segregation regulators, cenpt and ncapg, are included in this list. Thus, Banp directly regulates transcription of wrnip1 for recovery from DNA replication stress, and cenpt and ncapg for chromosome segregation during mitosis. Our findings provide the first in vivo evidence that Banp is required for cell-cycle progression and cell survival by regulating DNA damage responses and chromosome segregation during mitosis.

In order for a cell to divide, it must progress through a series of carefully controlled steps known as the cell cycle. First, the cell replicates its DNA and both copies get segregated to opposite ends. The cell then splits into two and each new cell receives a copy of the duplicated genetic material. If any of the stages in the cell cycle become disrupted or mis-regulated this can lead to uncontrolled divisions that may result in cancer.

Researchers have often used a structure within the eye known as the retina to study the cell cycle in zebrafish and other animals as cells in the retina rapidly divide in a highly controlled manner. A protein called Banp is known to help stop tumors from growing in humans and mice, but its normal role in the body, particularly the cell cycle, has remained unclear. To investigate, Babu et al. studied the retina of mutant zebrafish that were unable to make the Banp protein.

The experiments revealed that two stress responses indicating DNA damage or defects in copying DNA were active in the retinal cells of the mutant zebrafish. This suggested that Banp allows cell to progress through the cell cycle by repairing any DNA damage that may arise during replication. Banp does this by activating the gene for another protein called Wrnip1. Babu et al. also found that Banp helps segregate the two copies of DNA during cell division by promoting the activation of two other proteins called Cenpt and Ncapg. Further experiments identified 31 genes that were directly regulated by Banp.

These findings demonstrate that Banp is required for zebrafish cells to be able to accurately copy their DNA and divide in to two new cells. In the future, the work of Babu et al. will provide a useful resource to investigate how tumors grow and spread around the body, and may contribute to the development of new treatments for cancer.

Distinct structural bases for sequence-specific DNA binding by mammalian BEN domain proteins

The BEN domain is a recently recognized DNA binding module that is present in diverse metazoans and certain viruses. Several BEN domain factors are known as transcriptional repressors, but, overall, relatively little is known of how BEN factors identify their targets in humans. In particular, X-ray structures of BEN domain:DNA complexes are only known for Drosophila factors bearing a single BEN domain, which lack direct vertebrate orthologs. Here, we characterize several mammalian BEN domain (BD) factors, including from two NACC family BTB-BEN proteins and from BEND3, which has four BDs. In vitro selection data revealed sequence-specific binding activities of isolated BEN domains from all of these factors. We conducted detailed functional, genomic, and structural studies of BEND3. We show that BD4 is a major determinant for in vivo association and repression of endogenous BEND3 targets. We obtained a high-resolution structure of BEND3-BD4 bound to its preferred binding site, which reveals how BEND3 identifies cognate DNA targets and shows differences with one of its non-DNA-binding BEN domains (BD1). Finally, comparison with our previous invertebrate BEN structures, along with additional structural predictions using AlphaFold2 and RoseTTAFold, reveal distinct strategies for target DNA recognition by different types of BEN domain proteins. Together, these studies expand the DNA recognition activities of BEN factors and provide structural insights into sequence-specific DNA binding by mammalian BEN proteins.

Genetic determinants of telomere length from 109,122 ancestrally diverse whole-genome sequences in TOPMed

Genetic studies on telomere length are important for understanding age-related diseases. Prior GWAS for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally-diverse individuals (European, African, Asian and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n=109,122 individuals. We identified 59 sentinel variants (p-value <5×10-9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated the independent signals colocalized with cell-type specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated our TL polygenic trait scores (PTS) were associated with increased risk of cancer-related phenotypes.

Tumor suppressor SMAR1 regulates PKM alternative splicing by HDAC6-mediated deacetylation of PTBP1

BACKGROUND

Highly proliferating cancer cells exhibit the Warburg effect by regulation of PKM alternative splicing and promoting the expression of PKM2. Majority of the alternative splicing events are known to occur in the nuclear matrix where various MARBPs actively participate in the alternative splicing events. SMAR1, being a MARBP and an important tumor suppressor, is known to regulate the splicing of various cancer-associated genes. This study focuses on the regulation of PKM alternative splicing and inhibition of the Warburg effect by SMAR1.

METHODS

Immunohistochemistry was performed in breast cancer patient samples to establish the correlation between SMAR1 and PKM isoform expression. Further, expression of PKM isoforms upon modulation in SMAR1 expression in breast cancer cell lines was quantified by qRT-PCR and western blot. The acetylation status of PTBP1 was estimated by immunoprecipitation along with its enrichment on PKM pre-mRNA by CLIP in SMAR1 knockdown conditions. The role of SMAR1 in tumor metabolism and tumorigenesis was explored by in vitro enzymatic assays and functional assays upon SMAR1 knockdown. Besides, in vivo tumor formation by injecting adeno-SMAR1-transduced MDA-MB-231 cells in NOD/SCID mice was performed.

RESULTS

The expression profile of SMAR1 and PKM isoforms in breast cancer patients revealed that SMAR1 has an inverse correlation with PKM2 and a positive correlation with PKM1. Further quantitative PKM isoform expression upon modulation in SMAR1 expression also reflects that SMAR1 promotes the expression of PKM1 over tumorigenic isoform PKM2. SMAR1 deacetylates PTBP1 via recruitment of HDAC6 resulting in reduced enrichment of PTBP1 on PKM pre-mRNA. SMAR1 inhibits the Warburg effect, tumorigenic potential of cancer cells, and in vivo tumor generation in a PKM2-dependent manner.

CONCLUSIONS

SMAR1 regulates PKM alternative splicing by causing HDAC6-dependent deacetylation of PTBP1, resulting in reduced enrichment of PTBP1 on PKM pre-mRNA. Additionally, SMAR1 suppresses glucose utilization and lactate production via repression of PKM2 expression. This suggests that tumor suppressor SMAR1 inhibits tumor cell metabolism and tumorigenic properties of cancer cells via regulation of PKM alternative splicing.

Chemical Decorations of "MARs" Residents in Orchestrating Eukaryotic Gene Regulation

Genome organization plays a crucial role in gene regulation, orchestrating multiple cellular functions. A meshwork of proteins constituting a three-dimensional (3D) matrix helps in maintaining the genomic architecture. Sequences of DNA that are involved in tethering the chromatin to the matrix are called scaffold/matrix attachment regions (S/MARs), and the proteins that bind to these sequences and mediate tethering are termed S/MAR-binding proteins (S/MARBPs). The regulation of S/MARBPs is important for cellular functions and is altered under different conditions. Limited information is available presently to understand the structure–function relationship conclusively. Although all S/MARBPs bind to DNA, their context- and tissue-specific regulatory roles cannot be justified solely based on the available information on their structures. Conformational changes in a protein lead to changes in protein–protein interactions (PPIs) that essentially would regulate functional outcomes. A well-studied form of protein regulation is post-translational modification (PTM). It involves disulfide bond formation, cleavage of precursor proteins, and addition or removal of low-molecular-weight groups, leading to modifications like phosphorylation, methylation, SUMOylation, acetylation, PARylation, and ubiquitination. These chemical modifications lead to varied functional outcomes by mechanisms like modifying DNA–protein interactions and PPIs, altering protein function, stability, and crosstalk with other PTMs regulating subcellular localizations. S/MARBPs are reported to be regulated by PTMs, thereby contributing to gene regulation. In this review, we discuss the current understanding, scope, disease implications, and future perspectives of the diverse PTMs regulating functions of S/MARBPs.

Anticancer potential of AgNPs synthesized using Acinetobacter sp. and Curcuma aromatica against HeLa cell lines: A comparative study

BACKGROUND

Biogenic nanoparticles are gaining attention due to their low toxicity and numerous biomedical applications. Present study aimed to compare the potential anticancer activity of two biogenic silver nanoparticles (bAgNPs and pAgNPs) against human cervical cancer cell lines (HeLa).

METHODS

bAgNPs were synthesized using Acinetobacter sp. whereas pAgNPs were synthesized using aqueous root extract of Curcuma aromatica. Effect of these nanoparticles on HeLa cells viability was studied using MTT assay and colony formation assay. Anticancer potential was determined using fluorescence microscopy and flow cytometry studies. Bio-compatibility studies were performed against peripheral blood mononuclear cells (PBMCs).

RESULTS

Both the nanoparticles showed 50 % viability of peripheral blood mononuclear cells (PBMCs) when used at high concentration (200 μg/mL). IC₅₀ for bAgNPs and pAgNPs against HeLa cells were 17.4 and 14 μg/mL respectively. Colony formation ability of Hela cells was reduced on treatment with both nanoparticles. Acridine orange and ethidium bromide staining demonstrated that bAgNPs were cytostatic whereas pAgNPs were apoptotic. JC-1 dye staining revealed that the mitochondrial membrane potential was affected on treatment with pAgNPs while it remained unchanged on bAgNPs treatment. Flow cytometry confirmed cell cycle arrest in HeLa cells on treatment with nanoparticles further leading to apoptosis in case of pAgNPs. About 77 and 58 % HeLa cells were found in subG1 phase on treatment with bAgNPs and pAgNPs respectively. bAgNPs showed cytostatic effect on HeLa cells arresting the cell growth in subG1 phase, whereas, pAgNPs triggered death of HeLa cells through mitochondrial membrane potential impairment and apoptosis.

CONCLUSION

Overall, bAgNPs and pAgNPs could be safe and showed potential to be used as anticancer nano-antibiotics against human cervical cancer cells.

SMAR1 repression by pluripotency factors and consequent chemoresistance in breast cancer stem-like cells is reversed by aspirin

The high abundance of drug efflux pumps in cancer stem cells (CSCs) contributes to chemotherapy resistance. The transcriptional regulator SMAR1 suppresses CSC expansion in colorectal cancer, and increased abundance of SMAR1 is associated with better prognosis. Here, we found in breast tumors that the expression of SMAR1 was decreased in CSCs through the cooperative interaction of the pluripotency factors Oct4 and Sox2 with the histone deacetylase HDAC1. Overexpressing SMAR1 sensitized CSCs to chemotherapy through SMAR1-dependent recruitment of HDAC2 to the promoter of the gene encoding the drug efflux pump ABCG2. Treating cultured CSCs or 4T1 tumor-bearing mice with the nonsteroidal anti-inflammatory drug aspirin restored SMAR1 expression and ABCG2 repression and enhanced tumor sensitivity to doxorubicin. Our findings reveal transcriptional mechanisms regulating SMAR1 that also regulate cancer stemness and chemoresistance and suggest that, by restoring SMAR1 expression, aspirin might enhance chemotherapeutic efficacy in patients with stem-like tumors.

An investigative study of antitumor properties of a novel thiazolo[4,5-d]pyrimidine small molecule revealing superior antitumor activity with CDK1 selectivity and potent pro-apoptotic properties

New thiazolo[4,5-d]pyrimidine analogues were synthesized and biologically assessed in-vitro for their antineoplastic activity. The growth inhibitory effects of these compounds were assessed through the National Cancer Institute-United States of America (NCI-USA) anticancer screening program. Compound5(7-Chloro-3-(2,4-dimethoxyphenyl)-5-methylthiazolo[4,5-d]pyrimidine-2(3H)-thione) was found to have a potent and broad-spectrum cytotoxic action against NCI panel with GI₅₀ (50% growth inhibition concentration) mean graph midpoint (MG-MID) = 2.88 µM. MTT assay was used to determine IC₅₀ values of the most potent agent against HCT-116 colorectal carcinoma and WI-38 human lung fibroblast cell lines; 5.33 µM ± 0.69 and 21.69 µM ± 1.04, respectively. Flow cytometric analysis revealed that compound5triggered apoptosis and G2/M cell cycle arrest. The ability of compound5to inhibit CDK1 (Cyclin-Dependent Kinase 1)/Cyclin B complex was evaluated, and its IC₅₀ value was 97 nM ± 2.33. Moreover, according to the gene expression analysis, compound5up-regulated p53, BAX, cytochrome c, caspases-3,-8 and-9 besides down-regulated Bcl-2. In conclusion, compound5exerted a potent pro-apoptotic activity through the activation of the intrinsic apoptotic pathway and arrested the cell cycle at the G2/M phase.

SMAR1 inhibits Wnt/β-catenin signaling and prevents colorectal cancer progression

Reduced expression of Scaffold/Matrix Attachment Region Binding Protein 1 (SMAR1) is associated with various cancers resulting in poor prognosis of the diseases. However, the precise underlying mechanism elucidating the loss of SMAR1 requires ongoing study. Here, we show that SMAR1 is highly downregulated during aberrant Wnt3a signaling due to proteasomal degradation and predicted poor prognosis of colorectal cancer. However, substitution mutation (Arginine and Lysine to Alanine) in the D-box elements of SMAR1 viz. "RCHL" and "RQRL" completely abrogated its proteasomal degradation despite Wnt3a activity. SMAR1 inhibited Wnt/β-catenin signaling by recruiting Histone deacetylase-5 to β-catenin promoter resulting in reduced cell migration and invasion. Consequently, reduced tumor sizes in in-vivo NOD-SCID mice were observed that strongly associated with suppression of β-catenin. However, loss of SMAR1 led to enriched H3K9 Acetylation in the β-catenin promoter that further increased Wnt/β-catenin signaling activities and enhanced colorectal cancer progression drastically. Using docking and isothermal titration calorimetric studies we show that small microbial peptides viz. AT-01C and AT-01D derived from Mycobacterium tuberculosis mask the D-box elements of SMAR1. These peptides stabilized SMAR1 expression that further inhibited metastatic SW480 colorectal cancer cell migration and invasion. Drastically reduced subcutaneous tumors were observed in in-vivo NOD-SCID mice upon administration of these peptides (25 mg/kg body weight) intraperitoneally. Taken together our structural studies, in-vitro and in-vivo results strongly suggest that the D-box elements of SMAR1 represent novel druggable targets, where the microbial peptides hold promise as novel colorectal cancer therapeutics.

MicroRNA-652 induces NED in LNCaP and EMT in PC3 prostate cancer cells

MicroRNAs (miRNAs) are small noncoding RNA molecules that post-transcriptionally regulate gene expression. Dysregulation of miRNAs is frequently associated with disease and, in particular, is involved in prostate cancer progression. Next generation miRNA sequencing identified a panel of five miRNAs associated with prostate cancer recurrence and metastasis. High expression of one of these five miRNAs, miR-652, correlated significantly with an increased rate of prostate cancer biochemical recurrence. Overexpression of miR-652 in prostate cancer cells, PC3 and LNCaP, resulted in increased growth, migration and invasion. Prostate cancer cell xenografts overexpressing miR-652 showed increased tumorigenicity and metastases. We found that miR-652 directly targets the B" regulatory subunit, PPP2R3A, of the tumor suppressor PP2A, inducing epithelial-mesenchymal transition (EMT) in PC3 cells and neuroendocrine-like differentiation (NED) in LNCaP cells. The mesenchymal marker N-cadherin increased and epithelial marker E-cadherin decreased in PC3 cells overexpressing miR-652. In LNCaP cells and xenografted tumors, overexpression of miR-652 increased markers of NED, including chromogranin A, neuron specific enolase, and synaptophysin. MiR-652 may contribute to prostate tumor progression by promoting NED through decreased PP2A function. MiR-652 expression could serve as a biomarker for aggressive prostate cancer, as well as provide an opportunity for novel therapy in prostate cancer.

Carbon nanospheres mediated nuclear delivery of SMAR1 protein (DNA binding domain) controls breast tumor in mice model

Aim: To investigate anticancer activity of the DNA binding domain of SMAR1 (His 5) in vitro and in vivo. Materials & methods: His 5 was conjugated to hydrothermally synthesized carbon nanospheres (CNs). Anticancer activity of CNs-His 5 was evaluated in vitro and in vivo. Results: CNs- His 5 significantly reduced cyclin D1 levels in MDA-MB-231 cells. Tumor bearing Balb/c mice injected with CNs-His 5 showed approximately 62% tumor regression and significantly reduced 18FDG uptake. Caspases assay and IHC staining confirmed tumor growth inhibition, which could be attributed to apoptotic, antiproliferative and antiangiogenic activities of His 5. Conclusion: DNA binding domain of the SMAR1 protein (His 5) has potent anticancer activity and its CNs mediated delivery could control breast tumor in mice model.

Control of apoptosis by SMAR1

The nuclear matrix associated protein SMAR1 is sensitive to p53 and acts as a stress inducer as well as a regulator in the p53 regulatory network. Depending on the amount of stress SMAR1 stimulates, it can drive the p53 dynamics in the system to various dynamical states which correspond to various cellular states. The behavior of p53 in these dynamical states is found to be multifractal, due to the mostly long range correlations and large scale fluctuations imparted by stress. This fractal behavior is exhibited in the topological properties of the networks constructed from these dynamical states, and is a signature of self-organization to optimize information flow in the dynamics. The assortativity found in these networks is due to perturbation induced by stress, and indicates that the hubs in the time series play a significant role in stress management. SMAR1 can also regulate apoptosis in the presence of HDAC1, depending on the stress induced by it.

Cdc20 directs proteasome-mediated degradation of the tumor suppressor SMAR1 in higher grades of cancer through the anaphase promoting complex

The Tumor suppressor SMAR1 (scaffold matrix attachment region binding protein 1) has a crucial role in maintaining genomic stability, cell cycle progression and apoptosis.Our previous finding showed that it is highly suppressed in higher grade of cancer. However, the underlying mechanism of this suppression was not well understood. In this study, we show that SMAR1 expression levels are controlled at the proteasomal level by five RING finger E3 ubiquitin ligases including, Cdc20, a substrate receptor of ubiquitin ligase APC/C complex. We found that Cdc20 binds and promotes proteasomal degradation of SMAR1 in a D-box motif dependent manner. Further, our results demonstrated that Cdc20 promotes proteasomal degradation of SMAR1 through K48-linked specific polyubiquitylation, and that short hairpin RNA mediated inactivation of Cdc20 leads to significant stabilization of SMAR1. These findings suggest that Cdc20 is responsible for maintaining the cellular levels of SMAR1. However, since Cdc20 fails to target SMAR1 upon exposure to genotoxic stresses, SMAR1 helps to maintain genomic stability under these conditions through its DNA damage repair activity. Interestingly, Cdc20-mediated degradation of SMAR1 promotes cell migration and invasion.The reciprocal relationship of the duo is evident in breast cancer cell lines as well as in patient samples, suggesting that Cdc20 functions as an important negative regulator of SMAR1 in higher grades of cancer. Our study reveals for the first time, the molecular mechanism associated with lower levels of expression of the important tumor suppressor SMAR1 in higher grades of breast cancer.

Ursolic acid nanoparticles inhibit cervical cancer growth in vitro and in vivo via apoptosis induction

Cervical cancer is a cause of cancer death, making it one of the most common causes of death among women globally. Previously, a variety of studies have revealed the molecular mechanisms by which cervical cancer develops. However, there are still limitations in treatment for cervical cancer. Ursolic acid is a naturally derived pentacyclic triterpene acid, exhibiting broad anticancer effects. Nanoparticulate drug delivery systems have been known to better the bioavailability of drugs on intranasal administration compared with only drug solutions. Administration of ursolic acid nanoparticles is thought to be sufficient to lead to considerable suppression of cervical cancer progression. We loaded gold-ursolic acid into poly(DL-lactide-co-glycolide) nanoparticles to cervical cancer cell lines due to the properties of ursolic acid in altering cellular processes and the easier absorbance of nanoparticles. In addition, in this study, ursolic acid nanoparticles were administered to cervical cancer cells to find effective treatments for cervical cancer inhibition. In the present study, ELISA, western blotting, flow cytometry and immunohistochemistry assays were carried out to calculate the molecular mechanism by which ursolic acid nanoparticles modulated cervical cancer progression. Data indicated that ursolic acid nanoparticles, indeed, significantly suppress cervial cancer cell proliferation, invasion and migration compared to the control group, and apoptosis was induced by ursolic acid nanoparticles in cervical cancer cells through activating caspases, p53 and suppressing anti-apoptosis-related signals. Furthermore, tumor size was reduced by treatment of ursolic acid nanoparticles in in vivo experiments. In conclusion, this study suggests that ursolic acid nanoparticles inhibited cervical cancer cell proliferation via apoptosis induction, which could be a potential target for future therapeutic strategy clinically.

Overexpression of SMAR1 Enhances Radiosensitivity in Human Breast Cancer Cell Line MCF7 via Activation of p53 Signaling Pathway

This study sought to investigate the effect of overexpression of SMAR1 (scaffold/matrix-associated region-binding protein 1) on cell radiosensitivity in breast cancer, as well as elucidate its regulatory mechanism. We constructed a lentiviral expression system to successfully overexpress SMAR1 in human breast cancer cell line MCF7. In addition, overexpression of SMAR1 in MCF7 cells enhanced the radiosensitivity to (89)SrCl2. Moreover, overexpression of SMAR1 significantly induced cell apoptosis rate and G2/M phase arrest under the irradiation of (89)SrCl2. In addition, Western blot analysis showed that overexpression of SMAR1 in MCF cells significantly increased the expression levels of pP53 (ser15), pP53 (ser20), acP53, and p21 and obviously decreased the expression of MDM2 under the irradiation of (89)SrCl2. Notably, these expression changes could be neutralized by PFTα, an inhibitor of p53 signaling pathway that could inhibit p53-dependent transactivation of p53-responsive genes. Therefore, overexpression of SMAR1 may increase radiosensitivity to (89)SrCl2 in breast cancer cell line MCF7 by p53-dependent G2/M checkpoint arrest and apoptosis. Enhanced expression of SMAR1 in tumors will help to improve the clinical efficiency of radiation therapy.

Differential Ratios of Omega Fatty Acids (AA/EPA+DHA) Modulate Growth, Lipid Peroxidation and Expression of Tumor Regulatory MARBPs in Breast Cancer Cell Lines MCF7 and MDA-MB-231

Omega 3 (n3) and Omega 6 (n6) polyunsaturated fatty acids (PUFAs) have been reported to exhibit opposing roles in cancer progression. Our objective was to determine whether different ratios of n6/n3 (AA/EPA+DHA) FAs could modulate the cell viability, lipid peroxidation, total cellular fatty acid composition and expression of tumor regulatory Matrix Attachment Region binding proteins (MARBPs) in breast cancer cell lines and in non-cancerous, MCF10A cells. Low ratios of n6/n3 (1:2.5, 1:4, 1:5, 1:10) FA decreased the viability and growth of MDA-MB-231 and MCF7 significantly compared to the non-cancerous cells (MCF10A). Contrarily, higher n6/n3 FA (2.5:1, 4:1, 5:1, 10:1) decreased the survival of both the cancerous and non-cancerous cell types. Lower ratios of n6/n3 selectively induced LPO in the breast cancer cells whereas the higher ratios induced in both cancerous and non-cancerous cell types. Interestingly, compared to higher n6/n3 FA ratios, lower ratios increased the expression of tumor suppressor MARBP, SMAR1 and decreased the expression of tumor activator Cux/CDP in both breast cancer and non-cancerous, MCF10A cells. Low n6/n3 FAs significantly increased SMAR1 expression which resulted into activation of p21^WAF1/CIP1 in MDA-MB-231 and MCF7, the increase being ratio dependent in MDA-MB-231. These results suggest that increased intake of n3 fatty acids in our diet could help both in the prevention as well as management of breast cancer.

Association of p53 and p21 polymorphisms with prostate cancer

Cell cycle deregulation is common in human cancer. Alterations of the tumor-suppressor gene p53 and its downstream effector p21 have been indicated in the development of numerous human malignancies. Therefore, we hypothesize that the p53 codon 72 polymorphism, either on its own or in combination with p21 (C98A and C70T) polymorphisms, modifies the risk of prostate cancer within the Slovak population, and no previous studies have investigated these gene-gene interactions in the pathogenesis of prostate cancer in the Slovak population. Polymerase chain reaction-restriction fragment length polymorphism was used to determine the p53 and p21 genotypes in subjects comprising 300 prostate cancer patients and 446 healthy individuals. These 3 polymorphisms individually did not correlate with the prostate cancer risk. Conversely, the interaction between the p53 and p21 polymorphisms significantly decreased the risk of prostate cancer, with the odds ratio (OR) being 0.49 [95% confidence interval (CI), 0.27-0.86; P<0.05] for subjects carrying the p53 codon 72 arginine (Arg)/proline (Pro)+Pro/Pro and p21 C98A CA genotypes compared to the combined reference genotypes p53 codon 72 Arg/Arg and p21 C98A CC. Neither the p53 genotypes nor the p21 genotypes showed statistically significant differences in Gleason score or serum prostate-specific antigen levels (P>0.05). A decreased risk of prostate cancer association with the p21 C98A CA genotype (OR=0.58; 95% CI, 0.36-0.93; P<0.05) in non-smokers compared to the non-smokers with the p21 C98A CC genotype was observed. Smokers carrying the p53 codon 72 Pro/Pro genotype were not at any significant risk of prostate cancer (OR=2.97; 95% CI, 0.51-17.15) compared to the non-smokers with the Arg/Arg genotype. Taken together, to the best of our knowledge this is the first study to show that a combination of the variant genotypes of p53 codon 72 and p21 C98A may modify the prostate cancer risk within the Slovak population.

Nuclear matrix-associated protein SMAR1 regulates alternative splicing via HDAC6-mediated deacetylation of Sam68

Pre-mRNA splicing is a complex regulatory nexus modulated by various trans-factors and their posttranslational modifications to create a dynamic transcriptome through alternative splicing. Signal-induced phosphorylation and dephosphorylation of trans-factors are known to regulate alternative splicing. However, the role of other posttranslational modifications, such as deacetylation/acetylation, methylation, and ubiquitination, that could modulate alternative splicing in either a signal-dependent or -independent manner remain enigmatic. Here, we demonstrate that Scaffold/matrix-associated region-binding protein 1 (SMAR1) negatively regulates alternative splicing through histone deacetylase 6 (HDAC6)-mediated deacetylation of RNA-binding protein Sam68 (Src-associated substrate during mitosis of 68 kDa). SMAR1 is enriched in nuclear splicing speckles and associates with the snRNAs that are involved in splice site recognition. ERK-MAPK pathway that regulates alternative splicing facilitates ERK-1/2-mediated phosphorylation of SMAR1 at threonines 345 and 360 and localizes SMAR1 to the cytoplasm, preventing its interaction with Sam68. We showed that endogenously, SMAR1 through HDAC6 maintains Sam68 in a deacetylated state. However, knockdown or ERK-mediated phosphorylation of SMAR1 releases the inhibitory SMAR1-HDAC6-Sam68 complex, facilitating Sam68 acetylation and alternative splicing. Furthermore, loss of heterozygosity at the Chr.16q24.3 locus in breast cancer cells, wherein the human homolog of SMAR1 (BANP) has been mapped, enhances Sam68 acetylation and CD44 variant exon inclusion. In addition, tail-vein injections in mice with human breast cancer MCF-7 cells depleted for SMAR1 showed increased CD44 variant exon inclusion and concomitant metastatic propensity, confirming the functional role of SMAR1 in regulation of alternative splicing. Thus, our results reveal the complex molecular mechanism underlying SMAR1-mediated signal-dependent and -independent regulation of alternative splicing via Sam68 deacetylation.

p21, p53, TP53BP1 and p73 polymorphisms and the risk of gastric cardia adenocarcinoma in a Chinese population

Gastric cardia adenocarcinoma (GCA) is one of the most common malignant tumors and among the leading causes of cancer-related death. Genetic factors might play an important role in GCA carcinogenesis. Here, we performed a hospital-based case-control study to evaluate the effect of functional p21, p53, TP53BP1 and p73 single nucleotide polymorphisms (SNPs) on the risk of GCA. The study included 330 GCA cases and 608 controls. Genotypes were determined using the ligation detection reaction (LDR) method. The p21 rs1059234 TT, p21 rs3176352 GC/CC, p21 rs762623 GA and TP53BP1 rs560191 CC genotypes were associated with the risk of GCA, and a genotype combination effect was observed. After Bonferroni correction, the association remained significant for TP53BP1 rs560191 G > C, whereas the remaining four SNPs showed no association between the polymorphisms and GCA risk in all comparison models. Further large replication studies are needed to confirm the present findings.

Nuclear matrix protein SMAR1 represses c-Fos-mediated HPV18 E6 transcription through alteration of chromatin histone deacetylation

Matrix attachment region (MAR)-binding proteins have been implicated in the transcriptional regulation of host as well as viral genes, but their precise role in HPV-infected cervical cancer remains unclear. Here we show that HPV18 promoter contains consensus MAR element in the LCR and E6 sequences where SMAR1 binds and reinforces HPV18 E6 transcriptional silencing. In fact, curcumin-induced up-regulation of SMAR1 ensures recruitment of SMAR1-HDAC1 repressor complex at the LCR and E6 MAR sequences, thereby decreasing histone acetylation at H3K9 and H3K18, leading to reorientation of the chromatin. As a consequence, c-Fos binding at the putative AP-1 sites on E6 promoter is inhibited. E6 depletion interrupts degradation of E6-mediated p53 and lysine acetyl transferase, Tip60. Tip60, in turn, acetylates p53, thereby restoring p53-mediated transactivation of proapoptotic genes to ensure apoptosis. This hitherto unexplained function of SMAR1 signifies the potential of this unique scaffold matrix-associated region-binding protein as a critical regulator of E6-mediated anti-apoptotic network in HPV18-infected cervical adenocarcinoma. These results also justify the candidature of curcumin for the treatment of HPV18-infected cervical carcinoma.

p21 rs3176352 G>C and p73 rs1801173 C>T polymorphisms are associated with an increased risk of esophageal cancer in a Chinese population

Objective

Esophageal cancer was the fifth most commonly diagnosed cancer and the fourth leading cause of cancer-related death in China in 2009. Genetic factors might play an important role in esophageal squamous cell carcinoma (ESCC) carcinogenesis.

Designs and Methods

To evaluate the effect p21, p53, TP53BP1 and p73 single nucleotide polymorphisms (SNPs) on the risk of ESCC, we conducted a hospital based case–control study. A total of 629 ESCC cases and 686 controls were recruited. Their genotypes were determined using ligation detection reaction (LDR) method.

Results

When the p21 rs3176352 GG homozygote genotype was used as the reference group, the CC genotype was associated with a significantly increased risk of ESCC. When the p73 rs1801173 CC homozygote genotype was used as the reference group, the CT genotype was associated with a significantly increased risk of ESCC. After Bonferroni correction, for p21 rs3176352 G>C, the p_correct was still significant. For the other six SNPs, in all comparison models, no association between the polymorphisms and ESCC risk was observed.

Conclusions

p21 rs3176352 G>C and p73 rs1801173 C>T SNPs are associated with increased risk of ESCC. To confirm the current findings, additional, larger studies and tissue-specific biological characterization are required.

A non-surgical approach for male germ cell mediated gene transmission through transgenesis

Microinjection of foreign DNA in male pronucleus by in-vitro embryo manipulation is difficult but remains the method of choice for generating transgenic animals. Other procedures, including retroviral and embryonic stem cell mediated transgenesis are equally complicated and have limitations. Although our previously reported technique of testicular transgenesis circumvented several limitations, it involved many steps, including surgery and hemicastration, which carried risk of infection and impotency. We improved this technique further, into a two step non-surgical electroporation procedure, for making transgenic mice. In this approach, transgene was delivered inside both testes by injection and modified parameters of electroporation were used for in-vivo gene integration in germ cells. Using variety of constructs, germ cell integration of the gene and its transmission in progeny was confirmed by PCR, slot blot and immunohistochemical analysis. This improved technique is efficient, requires substantially less time and can be easily adopted by various biomedical researchers.

The aqueous extract of Ficus religiosa induces cell cycle arrest in human cervical cancer cell lines SiHa (HPV-16 Positive) and apoptosis in HeLa (HPV-18 positive)

Natural products are being extensively explored for their potential to prevent as well as treat cancer due to their ability to target multiple molecular pathways. Ficus religiosa has been shown to exert diverse biological activities including apoptosis in breast cancer cell lines. In the present study, we report the anti-neoplastic potential of aqueous extract of F. religiosa (FRaq) bark in human cervical cancer cell lines, SiHa and HeLa. FRaq altered the growth kinetics of SiHa (HPV-16 positive) and HeLa (HPV-18 positive) cells in a dose-dependent manner. It blocked the cell cycle progression at G1/S phase in SiHa that was characterized by an increase in the expression of p53, p21 and pRb proteins with a simultaneous decrease in the expression of phospho Rb (ppRb) protein. On the other hand, in HeLa, FRaq induced apoptosis through an increase in intracellular Ca(2+) leading to loss of mitochondrial membrane potential, release of cytochrome-c and increase in the expression of caspase-3. Moreover, FRaq reduced the migration as well as invasion capability of both the cervical cancer cell lines accompanied with downregulation of MMP-2 and Her-2 expression. Interestingly, FRaq reduced the expression of viral oncoproteins E6 and E7 in both the cervical cancer cell lines. All these data suggest that F. religiosa could be explored for its chemopreventive potential in cervical cancer.

Synthesis of pyrazolo[1,5-a]pyrimidine linked aminobenzothiazole conjugates as potential anticancer agents

A series of pyrazolo[1,5-a]pyrimidine linked 2-aminobenzothizole conjugates (6a-t) were synthesized and evaluated for their anticancer activity against five human cancer cell lines. Among them two compounds 6p and 6m showed significant anticancer activity with IC50 values ranging from 2.01 to 7.07 and 1.94-3.46 μM, respectively. Moreover, cell cycle arrest in G2/M and reduction in Cdk1 expression level were observed upon treatment of these compounds and they also induced caspase-3 dependent apoptosis. This was further confirmed by staining as well as DNA fragmentation analysis.

A new cytotoxic quinolone alkaloid and a pentacyclic steroidal glycoside from the stem bark of Crataeva nurvala: study of anti-proliferative and apoptosis inducing property

Chemical investigation of stem bark of Crataeva nurvala afforded 5,7-dimethoxy-3-phenyl-1-ethyl-1,4-dihydro-4-quinolone and a steroidal glycoside with unprecedented pentacyclic ring system named crataemine (1a) and crataenoside (2) respectively. The structures of the compounds were determined by spectroscopic analysis. A series of compounds with modification at position 1 of 1a (1a-1c) were prepared. All compounds were screened for cytotoxic activity against HeLa, PC-3 and MCF-7 cells. Only 1a and 2 showed potency against all three cells. Mechanism based study for activity of the compounds demonstrated that it could block the migration of more aggressive HeLa and PC-3 cells and prevent their colony formation ability as well. The compounds potentiated apoptosis in HeLa and PC-3 cells in a significant manner.

Regulation of GAD65 expression by SMAR1 and p53 upon Streptozotocin treatment

Background

GAD65 (Glutamic acid decarboxylase 65 KDa isoform) is one of the most important auto-antigens involved in Type 1 diabetes induction. Although it serves as one of the first injury markers of β-islets, the mechanisms governing GAD65 expression remain poorly understood. Since the regulation of GAD65 is crucial for the proper functioning of insulin secreting cells, we investigated the stress induced regulation of GAD65 transcription.

Results

The present study shows that SMAR1 regulates GAD65 expression at the transcription level. Using a novel protein-DNA pull-down assay, we show that SMAR1 binding is very specific to GAD65 promoter but not to the other isoform, GAD67. We show that Streptozotocin (STZ) mediated DNA damage leads to upregulation of SMAR1 and p53 expression, resulting in elevated levels of GAD65, in both cell lines as well as mouse β-islets. SMAR1 and p53 act synergistically to up-regulate GAD65 expression upon STZ treatment.

Conclusion

We propose a novel mechanism of GAD65 regulation by synergistic activities of SMAR1 and p53.

Anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates as p53 activators in cervical cancer cells

A library of new anthranilamide-pyrazolo[1,5-a]pyrimidine conjugates were designed, synthesized, and evaluated for their anticancer activity in cervical cancer cells such as HeLa and SiHa that possess low levels of p53. All 24 conjugates showed antiproliferative activity, while some of them exhibit significant cytotoxicity. In assays related to cell-cycle distribution, these conjugates induced G(2) /M arrest in HeLa cells and G(1) cell-cycle arrest in SiHa cells. Immunocytochemistry assays revealed that these compounds cause nuclear translocation of p53, thereby indicating the activation of p53. In cervical cancer cells, the p53 protein is degraded by E6 oncoprotein. Immunoblot and RT-PCR analyses proved the presence of mitochondria-mediated apoptosis with involvement p53 target genes such as BAX, Bcl2, and p21 (CDKI). Moreover, these compounds increased the phosphorylated forms of p53 and provide signals for apoptosis induction. Interestingly, one of the conjugates, (2-phenyl-7-(3,4,5-trimethoxyphenyl)pyrazolo[1,5-a]pyrimidin-5-yl)(4-(2-(thiophen-2-ylmethylamino)benzoyl)piperazin-1-yl)methanone, is the most promising candidate in this series and has the potential to be taken up for further detailed studies.

Chromatin remodelling protein SMAR1 inhibits p53 dependent transactivation by regulating acetyl transferase p300

Acetylation of p53 is indispensable for its transcriptional activities and induction of apoptosis upon DNA damage. Here, we show that chromatin remodelling protein SMAR1 inhibits p53 acetylation and p53 dependent apoptosis by repressing p300 expression in response to DNA damage. The repression of p300 expression by SMAR1 is relieved upon treatment with proteosomal inhibitors MG132 and Lactacystin. We demonstrate that SMAR1 interacts with p53-p300 transcriptional complex and SMAR1 overexpression antagonizes p300 interaction with p53 and suppresses activation of p53 apoptotic targets and p53 regulated miRNA miR-34a. Conversely, knockdown of SMAR1 promotes p300 accumulation and p53 acetylation while ectopic expression of p300 rescues SMAR1 inhibition on p53. Collectively, these results indicate that SMAR1 is an important player in p300-p53 regulated DNA damage signalling pathway and can exert its effect on apoptosis in a transcription independent manner.

Curcumin enhances the efficacy of chemotherapy by tailoring p65NFκB-p300 cross-talk in favor of p53-p300 in breast cancer

Breast cancer cells often develop multiple mechanisms of drug resistance during tumor progression, which is the major reason for the failure of breast cancer therapy. High constitutive activation of NFκB has been found in different cancers, creating an environment conducive for chemotherapeutic resistance. Here we report that doxorubicin-induced SMAR1-dependent transcriptional repression and SMAR1-independent degradation of IkBα resulted in nuclear translocation of p65NFκB and its association with p300 histone acetylase and subsequent transcription of Bcl-2 to impart protective response in drug-resistant cells. Consistently SMAR1-silenced drug-resistant cells exhibited IkBα-mediated inhibition of p65NFκB and induction of p53-dependent apoptosis. Interestingly, curcumin pretreatment of drug-resistant cells alleviated SMAR1-mediated p65NFκB activation and hence restored doxorubicin sensitivity. Under such anti-survival condition, induction of p53-p300 cross-talk enhanced the transcriptional activity of p53 and intrinsic death cascade. Importantly, promyelocyte leukemia-mediated SMAR1 sequestration that relieved the repression of apoptosis-inducing genes was indispensable for such chemo-sensitizing ability of curcumin. A simultaneous decrease in drug-induced systemic toxicity by curcumin might also have enhanced the efficacy of doxorubicin by improving the intrinsic defense machineries of the tumor-bearer. Overall, the findings of this preclinical study clearly demonstrate the effectiveness of curcumin to combat doxorubicin-resistance. We, therefore, suggest curcumin as a potent chemo-sensitizer to improve the therapeutic index of this widely used anti-cancer drug. Taken together, these results suggest that curcumin can be developed into an adjuvant chemotherapeutic drug.

Synthesis and anticancer activity of oxindole derived imidazo[1,5-a]pyrazines

A series of oxindole derivatives of imidazo[1,5-a]pyrazines were prepared and confirmed by 1H NMR, mass and HRMS data. These compounds were evaluated for their anticancer activity against a panel of 52 human tumor cell lines derived from nine different cancer types: leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate and breast. Among them compound 7l showed significant anticancer activity with GI50 values ranging from 1.54 to 13.0 μM. Cell cycle arrest was observed in G0/G1 phase upon treatment of A549 cells with 6.5 μM (IC50) concentration of compound 7l and induced apoptosis. This was confirmed by Annexin V-FITC as well as DNA fragmentation analysis and interestingly this compound (7l) did not affect the normal cells.

Gene regulation by SMAR1: Role in cellular homeostasis and cancer

Changes in the composition of nuclear matrix associated proteins contribute to alterations in nuclear structure, one of the major phenotypes of malignant cancer cells. The malignancy-induced changes in this structure lead to alterations in chromatin folding, the fidelity of genome replication and gene expression programs. The nuclear matrix forms a scaffold upon which the chromatin is organized into periodic loop domains called matrix attachment regions (MAR) by binding to various MAR binding proteins (MARBPs). Aberrant expression of MARBPs modulates the chromatin organization and disrupt transcriptional network that leads to oncogenesis. Dysregulation of nuclear matrix associated MARBPs has been reported in different types of cancers. Some of these proteins have tumor specific expression and are therefore considered as promising diagnostic or prognostic markers in few cancers. SMAR1 (scaffold/matrix attachment region binding protein 1), is one such nuclear matrix associated protein whose expression is drastically reduced in higher grades of breast cancer. SMAR1 gene is located on human chromosome 16q24.3 locus, the loss of heterozygosity (LOH) of which has been reported in several types of cancers. This review elaborates on the multiple roles of nuclear matrix associated protein SMAR1 in regulating various cellular target genes involved in cell growth, apoptosis and tumorigenesis.

Aqueous cinnamon extract (ACE-c) from the bark of Cinnamomum cassia causes apoptosis in human cervical cancer cell line (SiHa) through loss of mitochondrial membrane potential

Background

Chemoprevention, which includes the use of synthetic or natural agents (alone or in combination) to block the development of cancer in human beings, is an extremely promising strategy for cancer prevention. Cinnamon is one of the most widely used herbal medicines with diverse biological activities including anti-tumor activity. In the present study, we have reported the anti-neoplastic activity of cinnamon in cervical cancer cell line, SiHa.

Methods

The aqueous cinnamon extract (ACE-c) was analyzed for its cinnamaldehyde content by HPTLC analysis. The polyphenol content of ACE-c was measured by Folin-Ciocalteau method. Cytotoxicity analysis was performed by MTT assay. We studied the effect of cinnamon on growth kinetics by performing growth curve, colony formation and soft agar assays. The cells treated with ACE-c were analyzed for wound healing assay as well as for matrix metalloproteinase-2 (MMP-2) expression at mRNA and protein level by RT-PCR and zymography, respectively. Her-2 protein expression was analyzed in the control and ACE-c treated samples by immunoblotting as well as confocal microscopy. Apoptosis studies and calcium signaling assays were analyzed by FACS. Loss of mitochondrial membrane potential (Δψ_m) in cinnamon treated cells was studied by JC-1 staining and analyzed by confocal microscopy as well as FACS.

Results

Cinnamon alters the growth kinetics of SiHa cells in a dose-dependent manner. Cells treated with ACE-c exhibited reduced number of colonies compared to the control cells. The treated cells exhibited reduced migration potential that could be explained due to downregulation of MMP-2 expression. Interestingly, the expression of Her-2 oncoprotein was significantly reduced in the presence of ACE-c. Cinnamon extract induced apoptosis in the cervical cancer cells through increase in intracellular calcium signaling as well as loss of mitochondrial membrane potential.

Conclusion

Cinnamon could be used as a potent chemopreventive drug in cervical cancer.

Synthesis and anti breast cancer activity of biphenyl based chalcones

A series of (2E,2'E)-1,1'-(3-hydroxy-5-methylbiphenyl-2,6-diyl)-bis(3-pheylprop-2-ene-1-ones (5-33) were prepared by the reaction of 1,3-diacetyl biphenyls (1-4) with different aldehydes in presence of catalytic amount of solid KOH in ethanol in excellent yields. The compounds were evaluated for anticancer activity against human breast cancer MCF-7 (estrogen responsive proliferative breast cancer model) and MDA-MB-231 (estrogen independent aggressive breast cancer model) cell lines, HeLa (cervical cancer) cell line, and human embryonic kidney (HEK-293) cells. Most of the compounds preferentially inhibited the growth of the aggressive human breast cancer cell lines, MDA-MB-231 in the range of 4.4-30 μM. The two compounds 9 and 29 proved to be better anticancer agents than the standard drug tamoxifen against the MDA-MB-231 cell lines. Mode of action of these compounds was established to be apoptosis, cell cycle arrest and loss of mitochondrial membrane potential.

Transcription factor co-repressors in cancer biology: roles and targeting

Normal transcription displays a high degree of flexibility over the choice, timing and magnitude of mRNA expression levels that tend to oscillate and cycle. These processes allow for combinatorial actions, feedback control and fine-tuning. A central role has emerged for the transcriptional co-repressor proteins such as NCOR1, NCOR2/SMRT, CoREST and CTBPs, to control the actions of many transcriptional factors, in large part, by recruitment and activation of a range of chromatin remodeling enzymes. Thus, co-repressors and chromatin remodeling factors are recruited to transcription factors at specific promoter/enhancer regions and execute changes in the chromatin structure. The specificity of this recruitment is controlled in a spatial-temporal manner. By playing a central role in transcriptional control, as they move and target transcription factors, co-repressors act as a key driver in the epigenetic economy of the nucleus. Co-repressor functions are selectively distorted in malignancy, by both loss and gain of function and contribute to the generation of transcriptional rigidity. Features of transcriptional rigidity apparent in cancer cells include the distorted signaling of nuclear receptors and the WNTs/beta-catenin axis. Understanding and predicting the consequences of altered co-repressor expression patterns in cancer cells has diagnostic and prognostic significance, and also have the capacity to be targeted through selective epigenetic therapies.

The role of TP53 and p21 gene polymorphisms in breast cancer biology in a well specified and characterized German cohort

OBJECTIVE

Abrogation of the function of TP53 gene is supposed to lead to a more aggressive breast cancer phenotype that produces a less favorable clinical outcome. The p21 gene on chromosome 6p21.2 can be stimulated by an activated TP53 gene. A product of transcription, the p21 protein, an inhibitor of cyclin-dependent kinases, has its function in gene repair and angiogenesis during cell division, and can regulate apoptosis. The purpose of this analysis was to examine for an association between the genotypes measured on two single nucleotide polymorphisms (SNPs) located within the TP53 and p21 genes.

METHODS

In a clinical epidemiological case-control study, 814 individuals were recruited. 550 samples (275 cases/275 control) of peripheral blood obtained from women (aged 22-87 years) with breast cancer and from healthy women (aged 23-87 years) were genotyped for frequencies of the following gene variances: R72P/rs1042522 (gene TP53) and S31R/ss4388499 (gene p21).

RESULTS

For the variance in gene TP53 no significant differences between the control group and women with breast cancer could be estimated. For the variance in gene p21 a statistically significant association between the SNP measured within p21 and breast cancer status was observed. The odds ratio for the increased risk for those carrying the CA genotype as opposed to the CC genotype is 1.74 (95% confidence ratio = 1.00-3.05).

CONCLUSION

Despite this finding p21 does not appear to act as an exclusive prognostic marker for breast cancer disease.

Coordinated regulation of p53 apoptotic targets BAX and PUMA by SMAR1 through an identical MAR element

How tumour suppressor p53 bifurcates cell cycle arrest and apoptosis and executes these distinct pathways is not clearly understood. We show that BAX and PUMA promoters harbour an identical MAR element and are transcriptional targets of SMAR1. On mild DNA damage, SMAR1 selectively represses BAX and PUMA through binding to the MAR independently of inducing p53 deacetylation through HDAC1. This generates an anti-apoptotic response leading to cell cycle arrest. Importantly, knockdown of SMAR1 induces apoptosis, which is abrogated in the absence of p53. Conversely, apoptotic DNA damage results in increased size and number of promyelocytic leukaemia (PML) nuclear bodies with consequent sequestration of SMAR1. This facilitates p53 acetylation and restricts SMAR1 binding to BAX and PUMA MAR leading to apoptosis. Thus, our study establishes MAR as a damage responsive cis element and SMAR1-PML crosstalk as a switch that modulates the decision between cell cycle arrest and apoptosis in response to DNA damage.

Tumor Necrosis Factor alpha (TNFalpha) regulates CD40 expression through SMAR1 phosphorylation

CD40 plays an important role in mediating inflammatory response and is mainly induced by JAK/STAT phosphorylation cascade. TNFalpha is the key cytokine that activates CD40 during inflammation and tumorigenesis. We have earlier shown that SMAR1 can repress the transcription of Cyclin D1 promoter by forming a HDAC1 dependent repressor complex. In this study, we show that SMAR1 regulates the transcription of NF-kappaB target gene CD40. SMAR1 recruits HDAC1 and forms a repressor complex on CD40 promoter and keeps its basal transcription in check. Further, we show that TNFalpha stimulation induces SMAR1 phosphorylation at Ser-347 and promotes its cytoplasmic translocation, thus releasing its negative effect. Concomitantly, TNFalpha induced phosphorylation of STAT1 at Tyr-701 by JAK1 facilitates its nuclear translocation and activation of CD40 through p300 recruitment and core Histone-3 acetylation. Thus, TNFalpha mediated regulation of CD40 expression occurs by dual phosphorylation of SMAR1 and STAT1.

Tumor suppressor protein SMAR1 modulates the roughness of cell surface: combined AFM and SEM study

Background

Imaging tools such as scanning electron microscope (SEM) and atomic force microscope (AFM) can be used to produce high-resolution topographic images of biomedical specimens and hence are well suited for imaging alterations in cell morphology. We have studied the correlation of SMAR1 expression with cell surface smoothness in cell lines as well as in different grades of human breast cancer and mouse tumor sections.

Methods

We validated knockdown and overexpression of SMAR1 using RT-PCR as well as Western blotting in human embryonic kidney (HEK) 293, human breast cancer (MCF-7) and mouse melanoma (B16F1) cell lines. The samples were then processed for cell surface roughness studies using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The same samples were used for microarray analysis as well. Tumors sections from control and SMAR1 treated mice as well as tissues sections from different grades of human breast cancer on poly L-lysine coated slides were used for AFM and SEM studies.

Results

Tumor sections from mice injected with melanoma cells showed pronounced surface roughness. In contrast, tumor sections obtained from nude mice that were first injected with melanoma cells followed by repeated injections of SMAR1-P44 peptide, exhibited relatively smoother surface profile. Interestingly, human breast cancer tissue sections that showed reduced SMAR1 expression exhibited increased surface roughness compared to the adjacent normal breast tissue. Our AFM data establishes that treatment of cells with SMAR1-P44 results into increase in cytoskeletal volume that is supported by comparative gene expression data showing an increase in the expression of specific cytoskeletal proteins compared to the control cells. Altogether, these findings indicate that tumor suppressor function of SMAR1 might be exhibited through smoothening of cell surface by regulating expression of cell surface proteins.

Conclusion

Tumor suppressor protein SMAR1 might be used as a phenotypic differentiation marker between cancerous and non-cancerous cells.

SMAR1 forms a ternary complex with p53-MDM2 and negatively regulates p53-mediated transcription

The intra-cellular level of tumor suppressor protein p53 is tightly controlled by an autoregulatory feedback loop between the protein and its negative regulator MDM2. The role of MDM2 in down-regulating the p53 response in unstressed conditions and in the post-stress recovery phase is well documented. However, interplay between the N-terminal phosphorylations and C-terminal acetylations of p53 in this context remains unclear. Here, we show that an MAR binding protein SMAR1 interacts with MDM2 and the Ser15 phosphorylated form of p53, forming a ternary complex in the post stress-recovery phase. This triple complex formation between p53, MDM2 and SMAR1 results in recruitment of HDAC1 to deacetylate p53. The deacetylated p53 binds poorly to the target promoter (p21), which results in switching off the p53 response, essential for re-entry into the cell cycle. Interestingly, the knock-down of SMAR1 using siRNA leads to a prolonged cell-cycle arrest in the post stress recovery phase due to ablation of p53-MDM2-HDAC1 interaction. Thus, the results presented here for the first time highlight the role of SMAR1 in masking the active phosphorylation site of p53, enabling the deacetylation of p53 by HDAC1-MDM2 complex, thereby regulating the p53 transcriptional response during stress rescue.

Tumor suppressor SMAR1 represses IkappaBalpha expression and inhibits p65 transactivation through matrix attachment regions

Aberrant NF-kappaB activity promotes tumorigenesis. However, NF-kappaB also inhibits tumor growth where tumor suppressor pathways remain unaltered. Thus, its role in tumorigenesis depends upon the function of other cellular factors. Tumor suppressor SMAR1 down-modulated in high grade breast cancers is regulated by p53 and is reported to interact and stabilize p53. Because both SMAR1 and NF-kappaB are involved in tumorigenesis, we investigated the effect of SMAR1 upon NF-kappaB activity. We show that SMAR1 induction by doxorubicin or overexpression produces functional NF-kappaB complexes that are competent for binding to NF-kappaB consensus sequence. However, SMAR1 induced p65-p50 complex is phosphorylation- and transactivation-deficient. Induction of functional NF-kappaB complexes stems from down-regulation of IkappaBalpha transcription through direct binding of SMAR1 to the matrix attachment region site present in IkappaBalpha promoter and recruitment of corepressor complex. Real time PCR array for NF-kappaB target genes revealed that SMAR1 down-regulates a subset of NF-kappaB target genes that are involved in tumorigenesis. We also show that SMAR1 inhibits tumor necrosis factor alpha-induced induction of NF-kappaB suggesting that activation of NF-kappaB by SMAR1 is independent and different from classical pathway. Thus, for the first time we report that a tumor suppressor protein SMAR1 can modulate NF-kappaB transactivation and inhibit tumorigenesis by regulating NF-kappaB target genes.

Tumor suppressor SMAR1 downregulates Cytokeratin 8 expression by displacing p53 from its cognate site

Intermediary filaments play a crucial role in transformation of cells to a malignant phenotype. Here, we report that tumor suppressor SMAR1 downregulates Cytokeratin 8 gene expression by modulating p53-mediated transactivation of this gene. Moreover, the cell surface cytokeratin expression was downregulated leading to a decreased migration and invasiveness of cells. We further validated these results using genotoxic stress agents that lead to an increase in the levels of SMAR1 protein. This subsequently represses the transcription of Cytokeratin 8 gene by local chromatin condensation mediated by histone methylation and deacetylation. Evaluation of SMAR1 and Cytokeratin 8 proteins in different grades of cancer using tissue microarray point out at the inverse expression profiles of these genes (i.e. low levels of SMAR1 correlating with high expression of Cytokeratin 8) in higher grades of breast cancer. Therefore, the results presented here highlight the mechanism of Cytokeratin 8 gene regulation by interplay of tumor suppressor proteins SMAR1 and p53.

Detection of copy number alterations in metastatic melanoma by a DNA fluorescence in situ hybridization probe panel and array comparative genomic hybridization: a southwest oncology group study (S9431)

PURPOSE

Gene copy number alteration (CNA) is common in malignant melanoma and is associated with tumor development and progression. The concordance between molecular cytogenetic techniques used to determine CNA has not been evaluated on a large set of loci in malignant melanoma.

EXPERIMENTAL DESIGN

A panel of 16 locus-specific fluorescence in situ hybridization (FISH) probes located on eight chromosomes was used to identify CNA in touch preparations of frozen tissue samples from 19 patients with metastatic melanoma (SWOG-9431). A subset (n = 11) was analyzed using bacterial artificial chromosome (BAC) array comparative genomic hybridization (aCGH) of DNA isolated directly from touch-preparation slides.

RESULTS

By FISH, most samples showed loss near or at WISP3/6p21, CCND3/6q22, and CDKN2A/9p21 (>75% of samples tested). More than one third of CDKN2A/9p21 losses were biallelic. Gains of NEDD9/6p24, MET/7q31, and MYC/8q24 were common (57%, 47%, and 41%, respectively) and CNA events involving 9p21/7p12.3 and MET were frequently coincident, suggesting gain of the whole chromosome 7. Changes were confirmed by aCGH, which also uncovered many discreet regions of change, larger than a single BAC. Overlapping segments observed in >45% of samples included many of the loci analyzed in the FISH study, in addition to other WNT pathway members, and genes associated with TP53 pathways and DNA damage response, repair, and stability.

CONCLUSIONS

This study outlines a set of CNAs at the gene and regional level, using FISH and aCGH, which may provide a benchmark for future studies and may be important in selection of individual therapy for patients with metastatic malignant melanoma.

Stabilization of SMAR1 mRNA by PGA2 involves a stem loop structure in the 5' UTR

Prostaglandins are anticancer agents known to inhibit tumor cell proliferation both in vitro and in vivo by affecting the mRNA stability. Here we report that a MAR-binding protein SMAR1 is a target of Prostaglandin A2 (PGA2) induced growth arrest. We identify a regulatory mechanism leading to stabilization of SMAR1 transcript. Our results show that a minor stem and loop structure present in the 5' UTR of SMAR1 (1-UTR) is critical for nucleoprotein complex formation that leads to SMAR1 stabilization in response to PGA2. This results in an increased SMAR1 transcript and altered protein levels, that in turn causes downregulation of Cyclin D1 gene, essential for G1/S phase transition. We also provide evidence for the presence of a variant 5' UTR SMAR1 (17-UTR) in breast cancer-derived cell lines. This form lacks the minor stem and loop structure required for mRNA stabilization in response to PGA2. As a consequence of this, there is a low level of endogenous tumor suppressor protein SMAR1 in breast cancer-derived cell lines. Our studies provide a mechanistic insight into the regulation of tumor suppressor protein SMAR1 by a cancer therapeutic PGA2, that leads to repression of Cyclin D1 gene.