Tumour suppressive effects of WEE1 gene silencing in breast cancer cells

BACKGROUND

WEE1 is a G2/M checkpoint regulator protein. Various studies have indicated that WEE1 could be a good target for cancer therapy. The main aim of this study was to asssess the tumor suppressive potential of WEE1 silencing in two different breast cancer cell lines, MCF7 which carries the wild-type p53 and MDA-MB468 which contains a mutant type.

MATERIALS AND METHODS

After WEE1 knockdown with specific shRNAs downstream effects on cell viability and cell cycle progression were determined using MTT and flow cytometry analyses, respectively. Real-time PCR and Western blotting were conducted to assess the effect of WEE1 inhibition on the expression of apoptotic (p53) and anti-apoptotic (Bcl2) factors and also a growth marker (VEGF).

RESULTS

The results showed that WEE1 inhibition could cause a significant decrease in the viability of both MCF7 and MDA-MB-468 breast cancer cell lines by more than 50%. Interestingly, DNA content assays showed a significant increase in apoptotic cells following WEE1 silencing. WEE1 inhibition also induced up- regulation of the apoptotic marker, p53, in breast cancer cells. A significant decrease in the expression of VEGF and Bcl-2 was observed following WEE1 inhibition in both cell lines.

CONCLUSIONS

In concordance with previous studies, our data showed that WEE1 inhibition could induce G2 arrest abrogation and consequent cell death in breast cancer cells. Moreover, in this study, the observed interactions between the pro- and anti-apoptotic proteins and decrease in the angiogenesis marker expression confirm the susceptibility to apoptosis and validate the tumor suppressive effect of WEE1 inhibition in breast cancer cells. Interestingly, the levels of the sensitivity to WEE1 silencing in breast cancer cells, MCF7 and MDA-MB468, seem to be in concordance with the level of p53 expression.

Probiotics or antibiotics: future challenges in medicine

Genetic and environmental factors can affect the intestinal microbiome and microbial metabolome. Among these environmental factors, the consumption of antibiotics can significantly change the intestinal microbiome of individuals and consequently affect the corresponding metagenome. The term 'probiotics' is related to preventive medicine rather than therapeutic procedures and is, thus, considered the opposite of antibiotics. This review discusses the challenges between these opposing treatments in terms of the following points: (i) antibiotic resistance, the relationship between antibiotic consumption and microbiome diversity reduction, antibiotic effect on the metagenome, and disease associated with antibiotics; and (ii) probiotics as living drugs, probiotic effect on epigenetic alterations, and gut microbiome relevance to hygiene indulgence. The intestinal microbiome is more specific for individuals and may be affected by environmental alterations and the occurrence of diseases.

Abstract 1551: p53 mutant regulates a network of cellular anoikis through activation of AKT and suppression of BMF

p53 is the most frequently mutated tumor suppressor gene in human cancers. Unlike other tumor-suppressor genes, p53 mutations mainly occur as missense mutations within the DNA-binding domain, leading to the expression of full-length mutant p53 protein. Mutant p53 proteins not only lose their tumor suppressor function, but may also gain new oncogenic function and promote tumorigenesis through transactivation of new target genes. By using an RNA interference (RNAi) approach, we show that silencing of endogenous p53 R273H contact mutant in MDA-MB-468 cells induced massive apoptosis while no apoptosis was observed in the silencing of the p53 R175H structural mutant in SKBR3 cells. Further analysis shows that the apoptotic effects of mutant p53 knock-down involved activation of caspase-9 and mitochondria depolarisation, suggesting a role for mutant p53 in suppressing the intrinsic apoptotic pathway. Indeed, a BCL-2 family member, BCL-2 modifying factor (BMF), was reproducibly up-regulated following knock-down of mutant p53 in MDA-MB-468 cells while no significant changes was observed in other BCL2 family members. Furthermore, we show that p53 R273H contact mutant, but not p53 R175H conformation mutant, suppressed anoikis by down-regulation of BMF expression. Anoikis is a form of apoptosis induced by cell detachment and is a major mechanism to prevent metastasis. Further analyses using microarray gene profiling and connectivity map analysis show that silencing of mutant p53 in MDA-MB-468 cells generates gene expression signatures characteristic of PI3K inhibitors, suggesting that apoptotic effects of mutant p53 knock-down involved dephosphorylation of AKT, a direct substrate of PI3K. Ectopic expression of the activated form of AKT in MDA-MB-468 completely abrogated the apoptotic effects of mutant p53 knock-down. In summary, our results demonstrate that R273H mutant p53 promotes anoikis resistance in breast cancer cells that express it through suppression of BMF expression by the constitutively activated AKT pathway.

Citation Format: Boon Shing Tan, Kai Hung Tiong, Ivan Kok Seng Yap, Rozita Rosli, Soon-Keng Cheong, Chee-Onn Leong. p53 mutant regulates a network of cellular anoikis through activation of AKT and suppression of BMF. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1551. doi:10.1158/1538-7445.AM2014-1551

Probiotic assessment of Enterococcus durans 6HL and Lactococcus lactis 2HL isolated from vaginal microflora

Forty-five lactic acid bacteria (LAB) were isolated from the vaginal specimens of healthy fertile women, and the identities of the bacteria were confirmed by sequencing of their 16S rDNA genes. Among these bacteria, only four isolates were able to resist and survive in low pH, bile salts and simulated in vitro digestion conditions. Lactococcus lactis 2HL, Enterococcus durans 6HL, Lactobacillus acidophilus 36YL and Lactobacillus plantarum 5BL showed the best resistance to these conditions. These strains were evaluated further to assess their ability to adhere to human intestinal Caco-2 cells. Lactococcus lactis 2HL and E. durans 6HL were the most adherent strains. In vitro tests under neutralized pH proved the antimicrobial activity of both strains. Results revealed that the growth of Escherichia coli O26, Staphylococcus aureus and Shigella flexneri was suppressed by both LAB strains. The antibiotic susceptibility tests showed that these strains were sensitive to all nine antibiotics: vancomycin, tetracycline, ampicillin, penicillin, gentamicin, erythromycin, clindamycin, sulfamethoxazole and chloramphenicol. These data suggest that E. durans 6HL and Lactococcus lactis 2HL could be examined further for their useful properties and could be developed as new probiotics.

Safety profile of dextran-spermine gene delivery vector in mouse lungs

A nano-sized polymer, dextran-spermine (D-SPM), was shown to have the capacity to deliver gene to the lung of mouse via intranasal route. In this study, assessments on the safety profile of D-SPM were performed to complement the gene expression results. African green monkey kidney fibroblast (COS-7) and human adenocarcinoma breast (MCF-7) cells transfected with D-SPM/pDNA showed massive reduction in the number of viable cells. As for in vivo study, elevated level of neutrophils was observed, despite the minimal level of pro-inflammatory cytokines (TNF-alpha, IL-12, IFN-gamma) detected in the bronchoalveolar lavage fluid (BALF) of mice treated with the D-SPM/pDNA complexes. Histology profile examinations of the lungs showed mild inflammatory responses, with inflamed areas overlap with healthy areas. Although reduction of mice weight was seen at day 1 post administration, the mice did not show any sign of abnormal behavior or physical appearance. Biodistribution study was performed to determine the ability of the D-SPM/pDNA complexes to infiltrate to other non-intended organs. The result showed that the D-SPM/pDNA complexes were only localized at the lung and no gene expression was detected in other organs or blood. In short, these results indicate that the D-SPM/pDNA exhibited mild toxicity in the mouse lungs.

Identification of immunogenic proteins of Candida parapsilosis by serological proteome analysis

AIMS

Systemic candidiasis is the leading fungal bloodstream infection, and its incidence has been on the rise. Recently, Candida parapsilosis has emerged as an increasingly prevalent fungal pathogen, but little is known about its antigenic profile. Hence, the current work was performed to discover immunogenic proteins of C. parapsilosis using serological proteome analysis.

METHODS AND RESULTS

Cell wall proteins extracted from C. parapsilosis were resolved by two-dimensional electrophoresis followed by immunoblotting using antisera from experimentally infected mice. Mass spectrometry analysis of the 32 immunoreactive protein spots resulted in the identification of 12 distinct proteins. Among them, 11 proteins were known antigens of Candida albicans, whereas Idh2p was identified for the first time as an immunogenic protein of Candida species. Recombinant Idh2p was expressed in Escherichia coli, and its antigenicity was verified by immunoblot analysis.

CONCLUSIONS

An immunoproteomic approach was successfully applied to identify immunogenic proteins of C. parapsilosis, with Idh2p as a novel candidate antigen. The identified antigens may serve as potential biomarkers for development of diagnostic assay and/or vaccine for C. parapsilosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work represents the first immunoproteomic analysis of C. parapsilosis, which provides new insights into host-pathogen interactions and pathogenesis of C. parapsilosis. The immunogenic proteins could be studied as biomarker candidates for C. parapsilosis.

Tamoxifen-loaded nanostructured lipid carrier as a drug delivery system: characterization, stability assessment and cytotoxicity

Cancer nanotherapeutics is beginning to overwhelm the global research and viewed to be the revolutionary treatment regime in the medical field. This investigation describes the development of a stable nanostructured lipid carrier (NLC) system as carrier for Tamoxifen (TAM). The TAM-loaded NLC (TAM-NLC) developed with 200mg of TAM showed a spherical particle with the size of 46.6nm, polydispersity index of 0.267, entrapment efficiency of 99.74% and with the zeta potential of -23.78mV. Besides, the equivalent cytotoxicity of TAM and TAM-NLC to human (MCF-7) and mice (4T1) mammary breast cancer cell lines were observed. Incubating the formulation at the physiological pH resulted into reduced Ostwald ripening rate but without any significant change in the absorptivity. When coupled with the measurements of zeta potential and Ostwald ripening rate, the absorbance assay may be used to predict the long-term stability of drug-loaded nanoparticle formulations. The results of the study also suggest that TAM-NLC is a promising drug delivery system for breast cancer therapy. This is the first encouraging report on the in vitro effect of TAM-NLC against human and mouse mammary adenocarcinoma cell lines.

Goniothalamin selectively induces apoptosis on human hepatoblastoma cells through caspase-3 activation

Goniothalamin is a biologically active styrylpyrone derivative isolated from various Goniothalamus species. The ability of goniothalamin to induce apoptosis via caspase-3 activation against hepatoblastoma (HepG2) and normal liver cells (Chang cells) was studied using morphological and biochemical evaluations. HepG2 and Chang cells were treated with goniothalamin for 72 h and analysed by TUNEL and Annexin-V/PI staining. Furthermore, the post-mitochondrial caspase-3 was quantified using ELISA. In view of our results, goniothalamin induced apoptosis on treated cells via alteration of cellular membrane integrity and cleavage of DNA. On the other hand, post-mitochondrial caspase-3 activity was significantly elevated in HepG2 cells treated with goniothalamin after 72 h. These findings suggest that goniothalamin induced apoptosis on HepG2 liver cancer cells via induction of caspase-3 with less sensitivity on the cell line of Chang cells.

Mucosal genetic immunization through microsphere-based oral carriers

Polymeric carriers in the form of cellulose acetate phthalate (CAP) and alginate (ALG) microspheres were used for encapsulation of plasmid DNA for oral mucosal immunization. Access into the intestinal mucosa by pVAX1 eukaryotic expression plasmid vectors carrying gene-coding sequences, either for the cholera enterotoxin B subunit (ctxB) immunostimulatory antigen or the green fluorescent protein (GFP), delivered from both types of microsphere carriers were examined in orally immunized BALB/c mice. Demonstration of transgene protein expression and IgA antibody responses at local mucosal sites suggest immunological response to a potential oral DNA vaccine formulated within the microsphere carriers.

Abstract 1134: RNAi screening of human kinome identified fibroblast growth factor receptor 4 (FGFR4) as potential molecular target in basal-like breast cancers (BLBC)

Global gene expression profiling has uncovered previously unrecognized subsets of human breast cancer, including the so-called "triple-negative" or "basal-like" tumours (BLBC) characterized by estrogen/progesterone receptor negativity, lack of Her-2/Neu amplification and high frequency of p53 mutation. These refractory tumours therefore are insensitive to hormonal therapy or trastuzumab-based therapy, and thus confer a markedly poor prognosis relative to other subtypes. To date, little progress has been made to identify specific molecular pathways associated with these refractory cancers that may be effectively targeted for therapeutic purposes. Using a human kinome RNAi library screen, we show that knock-down of endogenous human FGFR4 (but not FGFR1-3) induces significant tumor-specific cell death in basal-like breast cancer cells. Further analysis reveals that FGFR4 mediates the BLBC cells survival through activation of AKT as knock-down of endogenous FGFR4 in MDA-MB-468 and HCC1937 cells significantly reduced AKT phosphorylation. Consistently, ectopic expression of a constitutively active myristoylated AKT completely abrogates the apoptosis induced by FGFR4 knock-down. Interestingly, both MDA-MB-468 and HCC1937 also secrete fibroblast growth factor 19 (FGF19), a canonical ligand specific for FGFR4. RNAi-mediated silencing of FGF19 evidently suppresses the growth of these BLBC cells via AKT signalling as marked by diminished AKT phosphorylation following depletion of FGF19. Knockdown of FGF19 in addition triggers ERK1/2 activation to compensate for AKT signalling down-regulation in MDA-MB-468. Together, our results demonstrated the existence of a FGFR4-FGF19 autocrine loop which could potentially be developed as therapeutic target for future treatment of BLBC.

Citation Format: Kai Hung Tiong, Boon Shing Tan, Heng Lungh Choo, Ammu Kutty Radhakrishnan, Rozita Rosli, Soon-Keng Cheong, Chee-Onn Leong. RNAi screening of human kinome identified fibroblast growth factor receptor 4 (FGFR4) as potential molecular target in basal-like breast cancers (BLBC). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1134. doi:10.1158/1538-7445.AM2013-1134

Downregulation of RhoGDIα increased migration and invasion of ER (+) MCF7 and ER (-) MDA-MB-231 breast cancer cells

Rho GDP dissociation inhibitors (RhoGDIs) can inhibit cell motility, invasion, and metastasis in cancer by inactivating the RhoGTPases. A member of RhoGDI family has been consistently shown to interact with estrogen receptor (ER), and change its transcriptional activity. ER is a receptor known to be inversely correlated with cell motility and invasion in breast cancer. The consequence of RhoGDIα activity on migration and invasion of ER (+) and ER (-) breast cancers is not clear. The aim of our study was to investigate the possible opposing effect of RhoGDIα on the migration and invasion of ER (+) MCF7 and ER (-) MDA-MB-231 breast cancer cells. RhoGDIα was downregulated using short interfering RNA (siRNA) and upregulated using GFP-tagged ORF clone of RhoGDIα, and their ability for migration and invasion was assayed using transwell chambers. It was found that the silencing of RhoGDIα in MCF7 and MDA-MB-231 cells significantly increased migration and invasion of these cells into the lower surface of porous membrane of the chambers. Overexpression of RhoGDIα in MCF7 cells suppressed their migration and invasion, but no significant effect was found on MDA-MB-231 cells. Our results indicate that the downregulation of RhoGDIα similarly affects the in vitro migration and invasion of ER (+) MCF7 and ER (-) MDA-MB-231 cells. However, our assays are differently affected by the upregulation of RhoGDIα in these two cell lines and this may be due to the differences in ER expression, primary invasive ability and/or other molecules between these two cell line models which warrant further investigation.

Calreticulin and cancer

Calreticulin (CRT) as a multi-functional endoplasmic reticulum protein is involved in a spectrum of cellular processes which ranges from calcium homeostasis and chaperoning to cell adhesion and finally malignant formation and progression. Previous studies have shown a contributing role for CRT in a range of different cancers. This present review will focus on the possible roles of CRT in the progression of malignant proliferation and the mechanisms involved in its contribution to cancer invasion.