Obesity, independent of p53 gene dosage, promotes mammary tumor progression and upregulates the p53 regulator microRNA-504

Downregulation of the long noncoding RNA DSCR9 (Down syndrome critical region 9) delays breast cancer progression by modulating microRNA-504-5p-dependent G protein-coupled receptor 65

Possible roles of long noncoding RNAs (lncRNAs) in cancer stem cells (CSCs) have often been reported. Here, we focused on the regulatory function of the lncRNA Down syndrome critical region 9 (DSCR9) in breast cancer stem cells (BCSCs). Through bioinformatics analysis, DSCR9, microRNA-504-5p (miR-504-5p), and G protein-coupled receptor 65 (GPR65) were identified as targets implicated in breast cancer development. Then, clinical tissue samples, breast cancer cells, and isolated BCSCs were used to determine the expression of DSCR9, miR-504-5p, and GPR65. The results confirmed the overexpression of DSCR9 and GPR65 but low expression of miR-504-5p in breast cancer tissues and cells as well as in BCSCs. Following mechanistic investigation, it was found that DSCR9 targeted miR-504-5p, and that silencing DSCR9 inhibited the proliferation of BCSCs by elevating the expression of miR-504-5p. Additionally, miR-504-5p targeted GPR65 and inhibited its expression. Moreover, GPR65 activated the MEK/ERK signaling pathway to regulate BCSC proliferation. Finally, animal study verified that depletion of DSCR9 inhibited the proliferation of BCSCs in vivo and that BCSC proliferation was restored by overexpression of GPR65. Altogether, our findings revealed that DSCR9 elevated GPR65 expression by targeting miR-504-5p to exacerbate breast cancer, highlighting a new treatment modality for breast cancer.

Regulation of DNA Damage Response and Homologous Recombination Repair by microRNA in Human Cells Exposed to Ionizing Radiation

Ionizing radiation may be of both artificial and natural origin and causes cellular damage in living organisms. Radioactive isotopes have been used significantly in cancer therapy for many years. The formation of DNA double-strand breaks (DSBs) is the most dangerous effect of ionizing radiation on the cellular level. After irradiation, cells activate a DNA damage response, the molecular path that determines the fate of the cell. As an important element of this, homologous recombination repair is a crucial pathway for the error-free repair of DNA lesions. All components of DNA damage response are regulated by specific microRNAs. MicroRNAs are single-stranded short noncoding RNAs of 20–25 nt in length. They are directly involved in the regulation of gene expression by repressing translation or by cleaving target mRNA. In the present review, we analyze the biological mechanisms by which miRNAs regulate cell response to ionizing radiation-induced double-stranded breaks with an emphasis on DNA repair by homologous recombination, and its main component, the RAD51 recombinase. On the other hand, we discuss the ability of DNA damage response proteins to launch particular miRNA expression and modulate the course of this process. A full understanding of cell response processes to radiation-induced DNA damage will allow us to develop new and more effective methods of ionizing radiation therapy for cancers, and may help to develop methods for preventing the harmful effects of ionizing radiation on healthy organisms.

MicroRNA-504 modulates osteosarcoma cell chemoresistance to cisplatin by targeting p53

Chemoresistance implicates the therapeutic value of cisplatin and remains a primary obstacle to its clinical use. MicroRNAs (miRs) negatively modulate the expression of their target genes and are associated with the occurrence and progression of various types of tumor. The abnormal expression of miR-504 has been reported in certain types of human tumor and has been associated with tumor prognosis. However, the association between miR-504 and cisplatin in human osteosarcoma remains unclear. The present study therefore aimed to assess the in vitro effects and possible mechanism of miR-504 in cell proliferation, apoptosis and cisplatin resistance in MG63 osteosarcoma cells. The results demonstrated that miR-504 was overexpressed in osteosarcoma tissues and cells. This overexpression also induced cell proliferation, as determined by MTT and EdU staining assays. Furthermore, miR-504 suppressed cisplatin-induced apoptosis, which was demonstrated via MTT, cell morphology analysis and flow cytometry. Cisplatin-induced G₁ arrest was also suppressed, which was determined by flow cytometry. The potential target genes of miR-504 were predicted using bioinformatics. p53 was confirmed to be a direct target of miR-504 using a luciferase reporter assay and western blot analysis revealed that miR-504 negatively regulated p53 expression at a molecular level. These results indicate that miR-504 contributes to cisplatin resistance in MG63 osteosarcoma cells by suppressing p53. miR-504 may therefore be a potential biomarker for cisplatin resistance in patients with osteosarcoma.

Roles of GSK-3 and microRNAs on epithelial mesenchymal transition and cancer stem cells

Various signaling pathways exert critical roles in the epithelial to mesenchymal transition (EMT) and cancer stem cells (CSCs). The Wnt/beta-catenin, PI3K/PTEN/Akt/mTORC, Ras/Raf/MEK/ERK, hedgehog (Hh), Notch and TP53 pathways elicit essential regulatory influences on cancer initiation, EMT and progression. A common kinase involved in all these pathways is moon-lighting kinase glycogen synthase kinase-3 (GSK-3). These pathways are also regulated by micro-RNAs (miRs). TP53 and components of these pathways can regulate the expression of miRs. Targeting members of these pathways may improve cancer therapy in those malignancies that display their abnormal regulation. This review will discuss the interactions of the multi-functional GSK-3 enzyme in the Wnt/beta-catenin, PI3K/PTEN/Akt/mTORC, Ras/Raf/MEK/ERK, Hh, Notch and TP53 pathways. The regulation of these pathways by miRs and their effects on CSC generation, EMT, invasion and metastasis will be discussed.

Emerging Concepts Linking Obesity with the Hallmarks of Cancer

There is compelling epidemiological evidence linking obesity to many tumours; however, the molecular mechanisms fuelling this association are not clearly understood. Emerging evidence links changes in the tumour microenvironment with the obese state, and murine and human studies highlight the relevance of adipose stromal cells (ASCs), including immune cells, both at remote fat depots, such as the omentum, as well as in peritumoural tissue. These obesity-associated changes have been implicated in several hallmarks of cancer, including the chronic inflammatory state and associated cell signalling, epithelial-to-mesenchymal transition (EMT), tumour-related fibrosis, angiogenesis, and genomic instability. Here, we present a summary of developments over the past 5 years, with particular focus on the tumour microenvironment in the obese state.

Regulatory module involving FGF13, miR-504, and p53 regulates ribosomal biogenesis and supports cancer cell survival

The microRNA miR-504 targets TP53 mRNA encoding the p53 tumor suppressor. miR-504 resides within the fibroblast growth factor 13 (FGF13) gene, which is overexpressed in various cancers. We report that the FGF13 locus, comprising FGF13 and miR-504, is transcriptionally repressed by p53, defining an additional negative feedback loop in the p53 network. Furthermore, we show that FGF13 1A is a nucleolar protein that represses ribosomal RNA transcription and attenuates protein synthesis. Importantly, in cancer cells expressing high levels of FGF13, the depletion of FGF13 elicits increased proteostasis stress, associated with the accumulation of reactive oxygen species and apoptosis. Notably, stepwise neoplastic transformation is accompanied by a gradual increase in FGF13 expression and increased dependence on FGF13 for survival ("nononcogene addiction"). Moreover, FGF13 overexpression enables cells to cope more effectively with the stress elicited by oncogenic Ras protein. We propose that, in cells in which activated oncogenes drive excessive protein synthesis, FGF13 may favor survival by maintaining translation rates at a level compatible with the protein quality-control capacity of the cell. Thus, FGF13 may serve as an enabler, allowing cancer cells to evade proteostasis stress triggered by oncogene activation.

Effects of mutations in Wnt/β-catenin, hedgehog, Notch and PI3K pathways on GSK-3 activity-Diverse effects on cell growth, metabolism and cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that participates in an array of critical cellular processes. GSK-3 was first characterized as an enzyme that phosphorylated and inactivated glycogen synthase. However, subsequent studies have revealed that this moon-lighting protein is involved in numerous signaling pathways that regulate not only metabolism but also have roles in: apoptosis, cell cycle progression, cell renewal, differentiation, embryogenesis, migration, regulation of gene transcription, stem cell biology and survival. In this review, we will discuss the roles that GSK-3 plays in various diseases as well as how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK, Wnt/beta-catenin, hedgehog, Notch and TP53. Mutations that occur in these and other pathways can alter the effects that natural GSK-3 activity has on regulating these signaling circuits that can lead to cancer as well as other diseases. The novel roles that microRNAs play in regulation of the effects of GSK-3 will also be evaluated. Targeting GSK-3 and these other pathways may improve therapy and overcome therapeutic resistance.

Systematic analysis of the p53-related microRNAs in breast cancer revealing their essential roles in the cell cycle

Numerous miRNAs have been found to be involved in the regulation of the p53 signaling pathway. Conversely, p53 regulates the transcription or processing of microRNAs (miRNAs). Given that complexities in the association between p53 and miRNAs exist, and due to the rapidly increasing amount of literature regarding the interactions between p53 and miRNAs, the present study systematically analyzed the associations between miRNAs and p53 in breast cancer using a literature-based discovery approach, natural language processing. A total of 22 miRNAs were found to be associated with p53. Next, three popular online tools (PicTar, miRanda and TargetScan) were used to predict the targets of each miRNA, and certain targets were validated by experiments. Gene Ontology annotation and network analysis demonstrated that the majority of the targets of the p53-related miRNAs were enriched in the cell cycle process. These results suggest that, in addition to regulating the transcription of cell cycle-related genes, p53 also indirectly modulates the cell cycle via miRNAs.

Adiposity is associated with p53 gene mutations in breast cancer

Mutations in the p53 gene are among the most frequent genetic events in human cancer and may be triggered by environmental and occupational exposures. We examined the association of clinical and pathological characteristics of breast tumors and breast cancer risk factors according to the prevalence and type of p53 mutations. Using tumor blocks from incident cases from a case-control study in western New York, we screened for p53 mutations in exons 2-11 using the Affymetrix p53 Gene Chip array and analyzed case-case comparisons using logistic regression. The p53 mutation frequency among cases was 28.1 %; 95 % were point mutations (13 % of which were silent) and the remainder were single base pair deletions. Sixty seven percent of all point mutations were transitions; 24 % of them are G:C>A:T at CpG sites. Positive p53 mutation status was associated with poorer differentiation (OR, 95 % CI 2.29, 1.21-4.32), higher nuclear grade (OR, 95 % CI 1.99, 1.22-3.25), and increased Ki-67 status (OR, 95 % CI 1.81, 1.10-2.98). Cases with P53 mutations were more likely to have a combined ER-positive and PR-negative status (OR, 95 % CI 1.65, 1.01-2.71), and a combined ER-negative and PR-negative status (OR, 95 % CI 2.18, 1.47-3.23). Body mass index >30 kg/m(2), waist circumference >79 cm, and waist-to-hip ratio >0.86 were also associated with p53 status; obese breast cancer cases are more likely to have p53 mutations (OR, 95 % CI 1.78, 1.19-2.68). We confirmed that p53 mutations are associated with less favorable tumor characteristics and identified an association of p53 mutation status and adiposity.

The effects of diet induced obesity on breast cancer associated pathways in mice deficient in SFRP1

Background

Secreted frizzled-related proteins (SFRPs) are a family of proteins that block the Wnt signaling pathway and loss of Sfrp1 expression is observed in breast cancer. The molecular mechanisms by which obesity contributes to breast tumorigenesis are not well defined, but involve increased inflammation. Mice deficient in Sfrp1 show enhanced mammary gland inflammation in response to diet induced obesity (DIO). Furthermore, mammary glands from Sfrp1^−/− mice exhibit increased Wnt signaling, decreased cell death responses, and excessive hyper branching. The work described here was initiated to investigate whether obesity exacerbates the aforementioned pathways, as they each play a key roles in the development of breast cancer.

Findings

Wnt signaling is significantly affected by DIO and Sfrp1^−/− loss as revealed by analysis of Myc mRNA expression and active β-catenin protein expression. Furthermore, Sfrp1^−/− mice fed a high fat diet (HFD) exhibit an increase in mammary cell proliferation. The death response is also impaired in the mammary gland of Sfrp1^−/− mice fed a normal diet (ND) as well as a HFD. In response to γ-irradiation, mammary glands from Sfrp1^−/− mice express significantly less Bax and Bbc3 mRNA, caspase-3 positive cells, and p53 protein. The expression of Wnt4 and Tnfs11 are critical for normal progesterone mediated mammary gland development and in response to obesity, Sfrp1^−/− mice express significantly more Wnt4 and Tnfs11 mRNA expression. Evaluation of progesterone receptor (PR) expression showed that DIO increases the number of PR positive cells.

Conclusions

Our data indicate that the expression of Sfrp1 is a critical factor required for maintaining appropriate cellular homeostasis in response to the onset of obesity.

Obesity increases tumor aggressiveness in a genetically engineered mouse model of serous ovarian cancer

OBJECTIVES

Obesity is associated with increased risk and worse outcomes for ovarian cancer. Thus, we examined the effects of obesity on ovarian cancer progression in a genetically engineered mouse model of serous ovarian cancer.

METHODS

We utilized a unique serous ovarian cancer mouse model that specifically deletes the tumor suppressor genes, Brca1 and p53, and inactivates the retinoblastoma (Rb) proteins in adult ovarian surface epithelial cells, via injection of an adenoviral vector expressing Cre (AdCre) into the ovarian bursa cavity of adult female mice (KpB mouse model). KpB mice were subjected to a 60% calories-derived from fat in a high fat diet (HFD) versus 10% calories from fat in a low fat diet (LFD) to mimic diet-induced obesity. Tumors were isolated at 6 months after AdCre injection and evaluated histologically. Untargeted metabolomic and gene expression profiling was performed to assess differences in the ovarian tumors from obese versus non-obese KpB mice.

RESULTS

At sacrifice, mice on the HFD (obese) were twice the weight of mice on the LFD (non-obese) (51g versus 31g, p=0.0003). Ovarian tumors were significantly larger in the obese versus non-obese mice (3.7cm(2) versus 1.2cm(2), p=0.0065). Gene expression and metabolomic profiling indicated statistically significant differences between the ovarian tumors from the obese versus non-obese mice, including metabolically relevant pathways.

Deconvoluting the obesity and breast cancer link: secretome, soil and seed interactions

Obesity is associated with increased risk of breast cancer in postmenopausal women and is linked with poor prognosis in pre- and postmenopausal breast cancer patients. The mechanisms underlying the obesity-breast cancer connection are becoming increasingly clear and provide multiple opportunities for primary to tertiary prevention. Several obesity-related host factors can influence breast tumor initiation, progression and/or response to therapy, and these have been implicated as key contributors to the complex effects of obesity on cancer incidence and outcomes. These host factors include components of the secretome, including insulin, insulin-like growth factor-1, leptin, adiponectin, steroid hormones, cytokines, vascular regulators, and inflammation-related molecules, as well as the cellular and structural components of the tumor microenvironment. These secreted and structural host factors are extrinsic to, and interact with, the intrinsic molecular characteristics of breast cancer cells (including breast cancer stem cells), and each will be considered in the context of energy balance and as potential targets for cancer prevention.