Silencing RBBP6 (Retinoblastoma Binding Protein 6) sensitises breast cancer cells MCF7 to staurosporine and camptothecin-induced cell death

Classical apoptotic stimulus, staurosporine, induces lytic inflammatory cell death, PANoptosis

Innate immunity is the body's first line of defense against disease, and regulated cell death is a central component of this response that balances pathogen clearance and inflammation. Cell death pathways are generally categorized as non-lytic and lytic. While non-lytic apoptosis has been extensively studied in health and disease, lytic cell death pathways are increasingly implicated in infectious and inflammatory diseases and cancers. Staurosporine (STS) is a well-known inducer of non-lytic apoptosis. However, in this study, we observed that STS also induces lytic cell death at later timepoints. Using biochemical assessments with genetic knockouts, pharmacological inhibitors, and gene silencing, we identified that STS triggered PANoptosis via the caspase-8/RIPK3 axis, which was mediated by RIPK1. PANoptosis is a unique, lytic, innate immune cell death pathway initiated by innate immune sensors and driven by caspases and RIPKs through PANoptosome complexes. Deletion of caspase-8 and RIPK3, core components of the PANoptosome complex, protected against STS-induced lytic cell death. Overall, our study identifies STS as a time-dependent inducer of lytic inflammatory cell death, PANoptosis. These findings emphasize the importance of understanding trigger- and time-specific activation of distinct cell death pathways to advance our understanding of the molecular mechanisms of innate immunity and cell death for clinical translation.

Anti-Cancer and Anti-Proliferative Potential of Cannabidiol: A Cellular and Molecular Perspective

Cannabinoids, the bioactive compounds found in Cannabis sativa, have been used for medicinal purposes for centuries, with early discoveries dating back to the BC era (BCE). However, the increased recreational use of cannabis has led to a negative perception of its medicinal and food applications, resulting in legal restrictions in many regions worldwide. Recently, cannabinoids, notably Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), have gained renewed interest in the medical field due to their anti-cancer properties. These properties include the inhibition of tumour growth and cell invasion, anti-inflammatory effects, and the induction of autophagy and apoptosis. As a result, the use of cannabinoids to treat chemotherapy-associated side effects, like nausea, vomiting, and pain, has increased, and there have been suggestions to implement the large-scale use of cannabinoids in cancer therapy. However, these compounds' cellular and molecular mechanisms of action still need to be fully understood. This review explores the recent evidence of CBD's efficacy as an anti-cancer agent, which is of interest due to its non-psychoactive properties. The current review will also provide an understanding of CBD's common cellular and molecular mechanisms in different cancers. Studies have shown that CBD's anti-cancer activity can be receptor-dependent (CB1, CB2, TRPV, and PPARs) or receptor-independent and can be induced through molecular mechanisms, such as ceramide biosynthesis, the induction of ER stress, and subsequent autophagy and apoptosis. It is projected that these molecular mechanisms will form the basis for the therapeutic applications of CBD. Therefore, it is essential to understand these mechanisms for developing and optimizing pre-clinical CBD-based therapies.

Probing the Effects of Retinoblastoma Binding Protein 6 (RBBP6) Knockdown on the Sensitivity of Cisplatin in Cervical Cancer Cells

Cervical cancer is a major cause of death in women despite the advancement of current treatment modalities. The conventional therapeutic agent, cisplatin (CCDP), is the standard treatment for CC; however, resistance often develops due to the cancer's heterogeneity. Therefore, a detailed elucidation of the specific molecular mechanisms driving CC is crucial for the development of targeted therapeutic strategies. Retinoblastoma binding protein 6 (RBBP6) is a potential biomarker associated with cell proliferation and is upregulated in cervical cancer sites, exhibiting apoptosis and dysregulated p53 expression. Furthermore, RBBP6 has been demonstrated to sensitize cancer cells to radiation and certain chemotherapeutic agents by regulating the Bcl-2 gene, thus suggesting a crosstalk among RBBP6/p53/BCL-2 oncogenic signatures. The present study, therefore, investigated the relationship between cisplatin and RBBP6 expression in CC cells. Herein, we first explored bioinformatics simulations and identified that the RBBP6/p53/BCL-2 signaling pathway is overexpressed and correlated with CC. For further analysis, we explored the Genomics of Drug Sensitivity in Cancer (GDSC) and found that most of the CC cell lines are sensitive to CCDP. To validate these findings, RBBP6 was silenced in HeLa and Vero cells using RNAi technology, followed by measurement of wild-type p53 and Bcl-2 at the mRNA level using qPCR. Cells co-treated with cisplatin and siRBBP6 were subsequently analyzed for apoptosis induction and real-time growth monitoring using flow cytometry and the xCELLigence system, respectively. Cancer cells in the co-treatment group showed a reduction in apoptosis compared to the cisplatin-treated group. Moreover, the real-time growth monitoring revealed a reduced growth rate in RBBP6 knockdown cells treated with cisplatin. Although wild-type p53 remained unchanged in the co-treatment group of cancer cells, Bcl-2 was completely repressed, suggesting that RBBP6 is necessary for sensitizing cervical cancer cells to cisplatin treatment by downregulating Bcl-2. The Vero cell population, which served as a non-cancerous control cell line in this study, remained viable following treatment with both siRBBP6 and cisplatin. Findings from this study suggest that RBBP6 expression promotes cisplatin sensitivity in HeLa cells through Bcl-2 downregulation. Knockdown of RBBP6 limits apoptosis induction and delays cell growth inhibition in response to cisplatin. The knowledge obtained here has the potential to help improve cisplatin efficacy through personalized administration based on the expression profile of RBBP6 among individual patients.

Cannabidiol and Cannabis Sativa as a potential treatment in vitro prostate cancer cells silenced with RBBp6 and PC3 xenograft

BACKGROUND

Prostate cancer is the second most frequently occurring carcinoma in males worldwide and one of the leading causes of death in men around the world. Recent studies estimate that over 1.4 million males are diagnosed with prostate cancer on an annual basis, with approximately 375,000 succumbing to the disease annually. With current treatments continuing to show severe side effects, there is a need for new treatments. In this study we looked at the effect of cannabis sativa extract, cannabidiol and cisplatin on prostate cancer cells, PC3.

METHODS

In addressing the above questions, we employed the MTT assay to measure the antiproliferative effect on PC3 cells following treatment with varying concentrations of Cannabis sativa extract, cisplatin and cannabidiol. xCELLigence was also used to confirm the IC50 activity in which cells were grown in a 16 well plate coated with gold and monitor cell attachment. Caspase 3/7 activity was also measured using 96 well-plate following treatment. Western-blot and qRT-PCR was also used to measure the gene expression of tumour suppressor genes, p53, Bax and Bcl2. Animal studies were employed to measure the growth of PC3-mouse derived cancer to evaluate the effect of compounds in vivo.

RESULTS

From the treatment with varying concentrations of Cannabis sativa extract, cannabidiol and cisplatin, we have observed that the three compounds induced antiproliferation of PC3 cancer cell lines through the activation of caspase 3/7 activity. We also observed induction of apoptosis in these cells following silencing of retinoblastoma binding protein 6 (RBBP6), with upregulation of p53 and bax mRNA expression, and a reduction in Bcl2 gene expression. The growth of tumours in the mouse models were reduced following treatment with cisplatin and cannabidiol.

CONCLUSION

We demonstrated that cannabidiol is a viable therapy to treat prostate cancer cells, in combination with silencing of RBBP6. This suggests that cannabidiol rather Cannabis sativa extract may play an important role in reducing cancer progression.

Integrated In Silico Analyses Identify PUF60 and SF3A3 as New Spliceosome-Related Breast Cancer RNA-Binding Proteins

More women are diagnosed with breast cancer (BC) than any other type of cancer. Although large-scale efforts have completely redefined cancer, a cure remains unattainable. In that respect, new molecular functions of the cell should be investigated, such as post-transcriptional regulation. RNA-binding proteins (RBPs) are emerging as critical post-transcriptional modulators of tumorigenesis, but only a few have clear roles in BC. To recognize new putative breast cancer RNA-binding proteins, we performed integrated in silico analyses of all human RBPs (n = 1392) in three major cancer databases and identified five putative BC RBPs (PUF60, TFRC, KPNB1, NSF, and SF3A3), which showed robust oncogenic features related to their genomic alterations, immunohistochemical changes, high interconnectivity with cancer driver genes (CDGs), and tumor vulnerabilities. Interestingly, some of these RBPs have never been studied in BC, but their oncogenic functions have been described in other cancer types. Subsequent analyses revealed PUF60 and SF3A3 as central elements of a spliceosome-related cluster involving RBPs and CDGs. Further research should focus on the mechanisms by which these proteins could promote breast tumorigenesis, with the potential to reveal new therapeutic pathways along with novel drug-development strategies.

E3 ubiquitin ligase RNF180 reduces sensitivity of triple-negative breast cancer cells to Gefitinib by downregulating RAD51

BACKGROUND

Gefitinib (Gef) is an EGFR inhibitor and its resistance in triple negative breast cancer (TNBC) is a critical concern. E3 ubiquitin ligases are pivotal for mediation of TNBC metastasis. However, the role of E3 ubiquitin ligase Ring Finger Protein 180 (RNF180) in EGFR inhibitor resistance of TNBC remains unclear. This study was performed to investigate how the E3 ubiquitin protein ligase RNF180 manipulated the growth, metastasis, and resistance to Gef of TNBC cells.

METHODS

TNBC tissues were harvested for detection of RNF180 and RAD51 expression. Gef-resistant cell lines were constructed. Next, gain- and loss-of-function assays were implemented in TNBC cell lines and Gef-resistant cell lines, followed by assessment of TNBC cell biological processes. IP assay was performed to detect the interaction between RNF180 and RAD51. Drug resistance-related genes (MRP1, BCRP, and MDR1) were evaluated by Western blot and RT-qPCR. The tumorigenesis was performed in nude mice to observe the growth and metastasis of TNBC in vivo.

RESULTS

RAD51 was highly expressed in TNBC tissues and cells, while RNF180 was poorly expressed. Mechanistically, RNF180 degraded RAD51 by ubiquitination. Overexpression of RNF180 or silencing of RAD51 suppressed proliferation, invasion, migration, and Gef resistance of TNBC cells and accelerated their apoptosis. Upregulation of RNF180 or downregulation of RAD51 diminished tumorigenesis and Gef resistance of TNBC in mice.

CONCLUSION

RNF180 degraded RAD51 by ubiquitination, thereby inhibiting TNBC cell growth and metastasis and sensitizing TNBC cells to Gef.

MicroRNA‑193a‑5p exerts a tumor suppressive role in epithelial ovarian cancer by modulating RBBP6

Epithelial ovarian cancer (EOC), a gynecological tumor, is associated with high mortality. MicroRNAs (miRs) serve a crucial role in EOC; however, the mechanisms underlying the effect of miRNA-193a-5p in EOC are not completely understood. Therefore, the present study aimed to investigate the expression levels of miR-193a-5p in serum samples of patients with EOC and to determine the role of miR-193a-5p in EOC. Reverse transcription-quantitative PCR was used to analyze the expression levels of miR-193a-5p in serum samples of patients with EOC and EOC cell lines. The effects of miR-193a-5p and RB binding protein 6, ubiquitin ligase (RBBP6) on the biological functions of EOC were determined by conducting a series of in vitro cell function experiments. The results indicated that the expression levels of miR-193a-5p were significantly decreased in serum samples obtained from patients with EOC and EOC cell lines compared with healthy individuals and normal cells, respectively. Further investigations indicated that RBBP6 was a target gene of miR-193a-5p. The expression levels of RBBP6 were significantly increased in patients with EOC compared with healthy individuals. In addition, in vitro analysis suggested that miR-193a-5p mimic significantly decreased SKOV3 cell proliferation, migration and invasion, and promoted SKOV3 cell apoptosis compared with the control and mimic-negative control groups. In addition, RBBP6 overexpression reversed miR-193a-5p mimic-mediated effects. In conclusion, the results of the present study suggested that downregulated expression levels of miR-193a-5p may serve an inhibitory role in EOC by inhibiting cell proliferation and metastasis, and promoting apoptosis.

Investigating the Effects of RBBP6 Gene Expression on Telomerase Activity in Cervical Cancer Cells

Background

RBBP6 is one of the genes identified as a proliferative gene that plays a role in cancer development, On the other hand both RBBP6 and telomerase activity have been shown to be increase in various cancers. E6 protein of HPV and RBBP6 is known to enhance the progression of cancer cells by interacting with p53 and presenting it to be ubiquitinated by the proteasome thereby promoting cell proliferation and preventing apoptosis. Studies also show that HPV E6 protein can increase telomerase activity by activating the expression of human telomerase reverse transcriptase (hTERT), thus enabling the immortalization of the cells. With RBBP6 and hTERT showing a similar profile in cancer cells, we seek to investigate any possible effect of RBBP6 on telomerase activity.

Results

Using real-time qPCR and TRAPeze RT Telomerase detection kit (Merc) respectively. We used cervical cancer cell lines in which CaSki cell showed the reduction of hTERT expression and reduction in telomerase activity significantly in RBBP6-knockdown cells. While no significant changes were observed in HeLa cells. Real-time growth assay revealed a significant drop in cell growth in co-silenced RBBP6 and hTERT cells substantiating our observation that RBBP6 might be playing a role in cell proliferation.

Conclusion

Taken all together, the observed effect of RBBP6 gene silencing on telomerase activity in cervical cancer is cell line dependent.

Regulation of Epithelial-Mesenchymal Plasticity by the E3 Ubiquitin-Ligases in Cancer

The epithelial-mesenchymal plasticity (EMP) is a process by which epithelial cells acquire the ability to dynamically switch between epithelial and mesenchymal phenotypic cellular states. Epithelial cell plasticity in the context of an epithelial-to-mesenchymal transition (EMT) confers increased cell motility, invasiveness and the ability to disseminate to distant sites and form metastasis. The modulation of molecularly defined targets involved in this process has become an attractive therapeutic strategy against cancer. Protein degradation carried out by ubiquitination has gained attention as it can selectively degrade proteins of interest. In the ubiquitination reaction, the E3 ubiquitin-ligases are responsible for the specific binding of ubiquitin to a small subset of target proteins, and are considered promising anticancer drug targets. In this review, we summarize the role of the E3 ubiquitin-ligases that control targeted protein degradation in cancer-EMT, and we highlight the potential use of the E3 ubiquitin-ligases as drug targets for the development of small-molecule drugs against cancer.

Analysis of the expression and association of retinoblastoma binding protein 6 with the JNK signaling pathway in prostate cancers

This study aims to investigate the expression of retinoblastoma binding protein 6 (RBBP6) in prostate cancer (PCa) and its association with the c-Jun N-terminal kinase (JNK) pathway. Immunohistochemistry was used to detect RBBP6 and JNK1/2 expression in PCa and benign prostatic hyperplasia tissues. RBBP6 expression in PCa cells (LNCap, PC3, and DU145) and noncancerous prostate epithelial cells (RWPE-1) was determined by quantitative real-time polymerase chain reaction and western blot analysis. PC3 and DU145 cells were transfected with RBBP6 small interfering RNAs (siRNAs) to examine the biological characteristics. Anisomycin (a JNK activator) with/without RBBP6 siRNA was used to treat PC3 cells for further investigating the ramification of the RBBP6-mediated JNK pathway in PCa. PCa tissues and cells showed higher RBBP6 and JNK1/2 expression. RBBP6 was positively correlated with JNK1/2 in PCa tissues. Besides, RBBP6 expression was correlated to clinical tumor stage, lymph node metastasis, Gleason grade, preoperative prostate-specific antigen level, as well as prognosis of PCa. RBBP6 siRNA reduced cell proliferation, arrested cells at G2/M, and promoted cell apoptosis, and suppressed JNK pathway. In addition, migration and invasion decreased after the RBBP6 siRNA transfection with downregulated matrix metallopeptidase-2 (MMP-2) and MMP-9. Anisomycin promoted the proliferation, invasion, and migration of PC3 cells and inhibited PC3 cell apoptosis, which could be reversed by RBBP6 siRNA. RBBP6 expression was upregulated in PCa tissues and positively correlated with expression level of JNK1/2. With inhibition of RBBP6 expression, the proliferation, invasion, and migration of PCa cells decreased dramatically, while PC3 cell apoptosis increased appreciably, accompanied by the suppression of the JNK pathway.

RBBP6 induces non-small cell lung cancer cell proliferation and high expression is associated with poor prognosis

Lung cancer is the most common cause of cancer-associated mortality in China with 85% of patients having non-small cell lung cancer (NSCLC). Identifying NSCLC driver genes and prognostic markers is critical to reducing these numbers. The studies of retinoblastoma binding protein 6 (RBBP6) performed on NSCLC is limited. The present study aimed to investigate the molecular function and the prognostic potential of RBBP6 in NSCLC using the A549 cell line and patient samples, respectively. The functional effect on cancer cell proliferation and prognostic value of RBBP6 were examined in vitro and in vivo using reverse transcription-quantitative PCR, immunofluorescence, immunohistochemistry (IHC) and xenograft implantation. The results demonstrated that RBBP6 mRNA expression was significantly higher in NSCLC tissues compared with in adjacent normal samples. When RBBP6 mRNA expression was interfered with using short hairpin RNA, A549 cell proliferation and xenograft tumor growth were reduced. Additionally, IHC and survival analysis demonstrated that patients with NSCLC with high expression levels of RBBP6 had a shorter median overall survival time compared with patients with low RBBP6 expression (31 vs. 51.5 months), and this was more prominent in stage I–II patients (43 vs. >67 months). High expression levels of RBBP6 indicated poor prognosis in patients with NSCLC. This may be due to the ability of RBBP6 to promote cancer cell proliferation. RBBP6 may be a potential prognostic biomarker and a therapeutic target for NSCLC.

RBBP6, a RING finger-domain E3 ubiquitin ligase, induces epithelial-mesenchymal transition and promotes metastasis of colorectal cancer

RBBP6 has been implicated in tumorigenesis but its role in tumor metastasis and progression has not been evaluated. Interestingly, here we show that RBBP6 is upregulated in colorectal cancer (CRC) where its expression level is positively correlated with distant metastasis. In this study, we identified RBBP6, a RING Finger-domain E3 ubiquitin ligase, served as an independent prognostic factor and predicted poor outcome for CRC patients. RBBP6 promoted cell proliferation, migration, and invasion in CRC cells and promoted tumor growth, lung metastasis, and liver metastasis in mouse models. Mechanistically, we revealed that RBBP6 bound and ubiquitylated IκBα, an inhibitor of the NF-κB-signaling pathway. RBBP6-mediated ubiquitination and degradation of IκBα significantly enhanced p65 nuclear translocation, which triggered the activation of NF-κB pathway and then induced the epithelial–mesenchymal transition (EMT) process and cell metastasis. Furthermore, by DNA methylation results and ChIP analysis, we demonstrated that the promoter of RBBP6 was hypomethylated, and was activated by multi-oncogenic transcription factors. In conclusion, our findings suggest that RBBP6 may be a potential prognostic biomarker and therapeutic target for CRC invasion and metastasis.

RBBP6 Is Abundantly Expressed in Human Cervical Carcinoma and May Be Implicated in Its Malignant Progression

RBBP6 is a novel gene encoding splicing-associated proteins. There are 3 protein isoforms (isoforms 1-3). RBBP6 isoforms 1 has been shown to interact with both p53 and Rb. It also plays a role in the induction of apoptosis and the regulation of the cell cycle. The expression of RBBP6 has been documented in several cancers but RBBP6 expression in cervical cancer has not been well studied. The aim of this study was to establish expression levels and tissue distribution of the RBBP6 gene products at both protein and messenger RNA (mRNA) levels in cervical cancer by immunocytochemistry and in situ hybridization (ISH). A link between RBBP6 expression, apoptosis, and cervical cancer progression was also investigated. RBBP6 mRNA was expressed in the nuclei and cytoplasm of normal and tumour cervical epithelium. In general, expression was high in the cytoplasm and nuclei of moderately differentiated and invasive carcinoma. Immunolabelling results were confirmed by image analysis and ISH experiments. Apoptosis assays using TUNEL correlated with the expression of the RBBP6 gene in all examined cases. This is the first report on the abundant expression of RBBP6 in cervical cancer and its involvement in the malignant progression of cervical cancer. Because of the high expression and corresponding pro-apoptotic activity observed in cervical cancer cells in this study, we suggest that RBBP6 is involved in the malignant progression of cervical cancer. RBBP6 proteins can therefore be targeted for therapeutic interventions against cervical cancer.

PACT cessation overcomes ovarian cancer cell chemoresistance to cisplatin by enhancing p53-mediated apoptotic pathway

Ovarian cancer ranks as a lethal gynecological malignancy, and development of resistance to chemotherapy agents constitutes a major clinical challenge in ovarian carcinoma management. P53-associated cellular protein-testes derived (PACT) is recently proven to be expressed aberrantly in several cancers, and exerts a critical roles in cell proliferation, apoptosis and migration. Up to now, its function in chemoresistance of ovarian cancer remains poorly defined. In the present study, elevated expression of PACT was detected in cisplatin-resistant A2780/CP cells relative to cisplatin-sensitive A2780 cells. Moreover, exposure to cisplatin also increased PACT expression in A2780 cells. Functional assay confirmed that knockdown of PACT further aggravated the inhibitory effects of cisplatin on A2780 cell viability and enhanced cell apoptosis and caspase-3 activity in cisplatin-treated A2780 cells, indicating that PACT cessation elevates cell sensitivity to cisplatin in A2780 cells. Whilst, deletion of PACT affords little effects on cisplatin resistance in p53-defective SKOV3 cells. Mechanistic analysis corroborated that depression of PACT notably enhanced cisplatin-induced p53 expression, concomitant with the increases in p53-downstream Bax, p21 expression and decrease in Bcl-2 expression. Intriguingly, blocking the p53 pathway notably reversed PACT inhibition-increased cell sensitivity to cisplatin in A2780 cells by elevating cell viability and depressing cell apoptosis. Additionally, abrogation of p53 signaling also blunts PACT suppression-overcomed chemotherapy resistance to cisplatin in A2780/CP cells. Together, these findings confirm that targeting PACT may antagonize ovarian cancer cell resistance to cisplatin, supporting a promising therapeutic strategy to overcome the chemotherapy resistance in the treatment of ovarian cancer.

RBBP6 expressional effects on cell proliferation and apoptosis in breast cancer cell lines with distinct p53 statuses

Introduction

Breast cancer is the most common malignancy amongst women and has a higher incidence rate than lung cancer. Its tumor progression partially results from inactivation of p53 which is caused by overexpression of ubiquitous regulatory proteins possessing p53-binding domain. RBBP6 is regarded as one of the ubiquitous proteins because of its RING finger-like domain which enables it to possess E3 ligase activity. Thus, it has become a potential target in cancer treatment as it is highly expressed in various malignancies including cancer. However, it is not clearly defined whether the effect of RBBP6 on cell growth and apoptosis is cell line-dependent, more especially in breast cancer cell lines that have distinct p53 expression profiles. This study aims at evaluating the effects of RBBP6 on cell growth and apoptosis in breast cancer cell lines with different p53 expressions.

Methods

Following the analysis at mRNA and protein levels in breast cancer tissue, RBBP6 expression was successfully manipulated using gene silencing and protein overexpression techniques in MCF-7 and MDA-MB-231 cell lines. The cells were co-treated with siRBBP6 and anticancer agents following apoptosis detection, which was confirmed by caspase 3/7 activity and quantification of apoptotic genes.

Results

RBBP6 was overexpressed in breast cancer tissues that were classified as stages 3 and 4, while in stage 1, its expression was much lower. The MCF-7 cell line which expresses wild-type p53 was more sensitive to apoptosis induction than MDA-MB-231 which is a mutant p53-expressing cell line. These data suggest that RBBP6 silencing triggers significant levels of intrinsic apoptosis, and its overexpression appears to promote cell proliferation in wild-type p53-expressing MCF-7 cell line as opposed to MDA-MB-231 cells.

Conclusion

The effect of RBBP6 on cell proliferation and apoptosis induction in breast cancer seems to be cell line-dependent based on p53 status.

RBBP6 increases radioresistance and serves as a therapeutic target for preoperative radiotherapy in colorectal cancer

Radiotherapy (RT) can be used as preoperative treatment to downstage initially unresectable locally rectal carcinoma, but radioresistance and recurrence remain significant problems. Retinoblastoma binding protein 6 (RBBP6) has been implicated in the regulation of cell cycle, apoptosis and chemoresistance both in vitro and in vivo. The present study investigated whether the inhibition of RBBP6 expression would improve radiosensitivity in human colorectal cancer cells. After SW620 and HT29 cells were exposed to radiation, the levels of RBBP6 mRNA and protein increased over time in both cells. Moreover, a significant reduction in clonogenic survival and a decrease in cell viability in parallel with an obvious increase in cell apoptosis were demonstrated in irradiated RBBP6‐knockdown cells. Transfection with RBBP6 shRNA improved the levels of G2‐M phase arrest, which blocked the cells in a more radiosensitive period of the cell cycle. These observations indicated that cell cycle and apoptosis mechanisms may be connected with tumor cell survival following radiotherapy. In vivo, the tumor growth rate of nude mice in the RBBP6‐knockdown group was significantly slower than that in other groups. These results indicated that RBBP6 overexpression could resist colorectal cancer cells against radiation by regulating cell cycle and apoptosis pathways, and inhibition of RBBP6 could enhance radiosensitivity of human colorectal cancer.

DNA methylation regulated microRNAs in human cervical cancer

Regulation of miRNA gene expression by DNA promoter methylation may represent a key mechanism to drive cervical cancer progression. In order to understand the impact of DNA promoter methylation on miRNAs at various stages of cervical carcinogenesis, we performed DNA methylation microarray on Normal Cervical Epithelium (NCE), Cervical Intraepithelial Neoplasia (CIN I-III) and Squamous Cell Carcinoma (SCC) tissues to identify differentially methylated miRNAs followed by validation by bisulfite sequencing. Further, expression of miRNAs was analyzed by qRT-PCR in clinical tissues and cervical cancer cell lines. Transcriptional activity was determined by luciferase assay. We identified a total of 69 hypermethylated and hypomethylated miRNA promoters encompassing 78 CpG islands in all except Y chromosome, among the three groups. The candidate DNA promoters of miR-424 were significantly hypermethylated and miR-200b and miR-34c were significantly hypomethylated in SCC compared to NCE (P < 0.05). Expression of miR-424, miR-200b, and miR-34c were inversely correlated with promoter DNA methylation in tissue samples. Treatment of cell lines with 5-aza-2'-deoxycytidine showed differential expression in all three miRNAs. We observed a decrease in miRNA promoter activity following in vitro SssI methylase treatment of miR-424, miR-200b, and miR-34c. Luciferase assay demonstrated that miR-200b and miR-424 functionally interacts with 3'-UTR of HIPK3 and RBBP6 respectively and decreased their activity in presence of miR-200b and miR-424 mimics transfected in SiHa cells. Taken together, we have identified deregulation of miRNAs by aberrant DNA promoter methylation, leading to its transcriptional silencing during cervical carcinogenesis, which can be potential targets for diagnosis and therapy.

Real-time and label-free impedimetric analysis of the formation and drug testing of tumor spheroids formed via the liquid overlay technique

Tumor spheroids formed via the liquid overlay technique were quantitatively monitored by impedance measurement across the interdigitated electrodes.

Cannabidiol rather than Cannabis sativa extracts inhibit cell growth and induce apoptosis in cervical cancer cells

BACKGROUND

Cervical cancer remains a global health related issue among females of Sub-Saharan Africa, with over half a million new cases reported each year. Different therapeutic regimens have been suggested in various regions of Africa, however, over a quarter of a million women die of cervical cancer, annually. This makes it the most lethal cancer amongst black women and calls for urgent therapeutic strategies. In this study we compare the anti-proliferative effects of crude extract of Cannabis sativa and its main compound cannabidiol on different cervical cancer cell lines.

METHODS

To achieve our aim, phytochemical screening, MTT assay, cell growth analysis, flow cytometry, morphology analysis, Western blot, caspase 3/7 assay, and ATP measurement assay were conducted.

RESULTS

Results obtained indicate that both cannabidiol and Cannabis sativa extracts were able to halt cell proliferation in all cell lines at varying concentrations. They further revealed that apoptosis was induced by cannabidiol as shown by increased subG0/G1 and apoptosis through annexin V. Apoptosis was confirmed by overexpression of p53, caspase 3 and bax. Apoptosis induction was further confirmed by morphological changes, an increase in Caspase 3/7 and a decrease in the ATP levels.

CONCLUSIONS

In conclusion, these data suggest that cannabidiol rather than Cannabis sativa crude extracts prevent cell growth and induce cell death in cervical cancer cell lines.

RBBP6: a potential biomarker of apoptosis induction in human cervical cancer cell lines

Overexpression of RBBP6 in cancers of the colon, lung, and esophagus makes it a potential target in anticancer therapy. This is especially important because RBBP6 associates with the tumor suppressor gene p53, the inactivation of which has been linked to over 50% of all cancer types. However, the expression of RBBP6 in cancer and its interaction with p53 are yet to be understood in order to determine whether or not RBBP6 is cancer promoting and therefore a potential biomarker. In this study, we manipulated RBBP6 expression levels followed by treatment with either camptothecin or γ-aminobutyric acid in cervical cancer cells to induce apoptosis or cell cycle arrest. We began by staining human cervical cancer tissue sections with anti-RBBP6 monoclonal antibody to evaluate the extent of expression of RBBP6 in patients’ specimens. We followed on with silencing the overexpression of RBBP6 and treatment with anticancer agents to evaluate how the specimens respond to combinational therapy. Apoptosis induction was evaluated through confocal microscope, and flow cytometry using annexin V staining, and also by checking the mitochondrial and caspase-3/7 activity. Cell cycle arrest was evaluated using flow cytometry through staining with propidium iodide. RBBP6 was highly expressed in cervical cancer tissue sections that were in stage II or III of development. Silencing RBBP6 followed by treatment with γ-aminobutyric acid and camptothecin seems to sensitize cells to apoptosis induction rather than cell cycle arrest. Overexpression of RBBP6 seems to promote S-phase in cell cycle and cell proliferation. These results predict a proliferative role of RBBP6 in cancer progression rather than as a cancer-causing gene. Furthermore, sensitization of cells to camptothecin-induced apoptosis by RBBP6 targeting suggests a promising tool for halting cervical cancer progression.

Update on a tumor-associated NADH oxidase in gastric cancer cell growth

Gastric cancer is one of the most common human malignancies, and its prevalence has been shown to be well-correlated with cancer-related deaths worldwide. Regrettably, the poor prognosis of this disease is mainly due to its late diagnosis at advanced stages after the cancer has already metastasized. Recent research has emphasized the identification of cancer biomarkers in the hope of diagnosing cancer early and designing targeted therapies to reverse cancer progression. One member of a family of growth-related nicotinamide adenine dinucleotide (NADH or hydroquinone) oxidases is tumor-associated NADH oxidase (tNOX; ENOX2). Unlike its counterpart CNOX (ENOX1), identified in normal rat liver plasma membranes and shown to be stimulated by growth factors and hormones, tNOX activity purified from rat hepatoma cells is constitutively active. Its activity is detectable in the sera of cancer patients but not in those of healthy volunteers, suggesting its clinical relevance. Interestingly, tNOX expression was shown to be present in an array of cancer cell lines. More importantly, inhibition of tNOX was well correlated with reduced cancer cell growth and induction of apoptosis. RNA interference targeting tNOX expression in cancer cells effectively restored non-cancerous phenotypes, further supporting the vital role of tNOX in cancer cells. Here, we review the regulatory role of tNOX in gastric cancer cell growth.

Dengue-induced autophagy, virus replication and protection from cell death require ER stress (PERK) pathway activation

A virus that reproduces in a host without killing cells can easily establish a successful infection. Previously, we showed that dengue-2, a virus that threatens 40% of the world, induces autophagy, enabling dengue to reproduce in cells without triggering cell death. Autophagy further protects the virus-laden cells from further insults. In this study, we evaluate how it does so; we show that dengue upregulates host pathways that increase autophagy, namely endoplasmic reticulum (ER) stress and ataxia telangiectasia mutated (ATM) signaling followed by production of reactive oxygen species (ROS). Inhibition of ER stress or ATM signaling abrogates the dengue-conferred protection against other cell stressors. Direct inhibition of ER stress response in infected cells decreases autophagosome turnover, reduces ROS production and limits reproduction of dengue virus. Blocking ATM activation, which is an early response to infection, decreases transcription of ER stress response proteins, but ATM has limited impact on production of ROS and virus titers. Production of ROS determines only late-onset autophagy in infected cells and is not necessary for dengue-induced protection from stressors. Collectively, these results demonstrate that among the multiple autophagy-inducing pathways during infection, ER stress signaling is more important to viral replication and protection of cells than either ATM or ROS-mediated signaling. To limit virus production and survival of dengue-infected cells, one must address the earliest phase of autophagy, induced by ER stress.

Application of xCELLigence RTCA Biosensor Technology for Revealing the Profile and Window of Drug Responsiveness in Real Time

The xCELLigence technology is a real-time cellular biosensor, which measures the net adhesion of cells to high-density gold electrode arrays printed on custom-designed E-plates. The strength of cellular adhesion is influenced by a myriad of factors that include cell type, cell viability, growth, migration, spreading and proliferation. We therefore hypothesised that xCELLigence biosensor technology would provide a valuable platform for the measurement of drug responses in a multitude of different experimental, clinical or pharmacological contexts. In this manuscript, we demonstrate how xCELLigence technology has been invaluable in the identification of (1) not only if cells respond to a particular drug, but (2) the window of drug responsiveness. The latter aspect is often left to educated guess work in classical end-point assays, whereas biosensor technology reveals the temporal profile of the response in real time, which enables both acute responses and longer term responses to be profiled within the same assay. In our experience, the xCELLigence biosensor technology is suitable for highly targeted drug assessment and also low to medium throughput drug screening, which produces high content temporal data in real time.