Specific unsaturated fatty acids enforce the transdifferentiation of human cancer cells toward adipocyte-like cells

Statins Lower Lipid Synthesis But Promote Secretion of Cholesterol-Enriched Extracellular Vesicles and Particles

Lipid droplets are lipid-rich cytosolic organelles that play roles in cell signaling, membrane trafficking, and many other cellular activities. Recent studies revealed that lipid droplets in cancer cells have various biological functions, such as energy production, membrane synthesis, and chemoresistance, thereby fostering cancer progression. Accordingly, the administration of antilipemic agents could improve anti-cancer treatment efficacy given hydrophobic chemotherapeutic drugs could be encapsulated into lipid droplets and then expelled to extracellular space. In this study, we investigated whether statins could promote treatment efficacy of lipid droplet-rich ovarian SKOV-3 cells and the potential influences on generation and composition of cell-derived extracellular vesicles and particles (EVP). Our studies indicate that statins can significantly lower lipid biosynthesis. Moreover, statins can inhibit proliferation, migration, and invasion of SKOV-3 cells and enhance chemosensitivity in vitro and in vivo. Furthermore, statins can lower EVP secretion but enforce the release of cholesterol-enriched EVPs, which can further lower lipid contents in parental cells. It is the first time that the influence of statins on EVP generation and EVP-lipid composition is observed. Overall, we demonstrated that statins could inhibit lipid production, expel cholesterol to extracellular space via EVPs, and improve chemosensitivity.

Influence of olive oil and its components on mesenchymal stem cell biology

Extra virgin olive oil is characterized by its high content of unsaturated fatty acid residues in triglycerides, mainly oleic acid, and the presence of bioactive and antioxidant compounds. Its consumption is associated with lower risk of suffering chronic diseases and unwanted processes linked to aging, due to the antioxidant capacity and capability of its components to modulate cellular signaling pathways. Consumption of olive oil can alter the physiology of mesenchymal stem cells (MSCs). This may explain part of the healthy effects of olive oil consumption, such as prevention of unwanted aging processes. To date, there are no specific studies on the action of olive oil on MSCs, but effects of many components of such food on cell viability and differentiation have been evaluated. The objective of this article is to review existing literature on how different compounds of extra virgin olive oil, including residues of fatty acids, vitamins, squalene, triterpenes, pigments and phenols, affect MSC maintenance and differentiation, in order to provide a better understanding of the healthy effects of this food. Interestingly, most studies have shown a positive effect of these compounds on MSCs. The collective findings support the hypothesis that at least part of the beneficial effects of extra virgin olive oil consumption on health may be mediated by its effects on MSCs.

Melanoma plasticity and phenotypic diversity: therapeutic barriers and opportunities

An incomplete view of the mechanisms that drive metastasis, the primary cause of cancer-related death, has been a major barrier to development of effective therapeutics and prognostic diagnostics. Increasing evidence indicates that the interplay between microenvironment, genetic lesions, and cellular plasticity drives the metastatic cascade and resistance to therapies. Here, using melanoma as a model, we outline the diversity and trajectories of cell states during metastatic dissemination and therapy exposure, and highlight how understanding the magnitude and dynamics of nongenetic reprogramming in space and time at single-cell resolution can be exploited to develop therapeutic strategies that capitalize on nongenetic tumor evolution.

TNBG-5602, a novel derivative of quinoxaline, inhibits liver cancer growth via upregulating peroxisome proliferator-activated receptor γ in vitro and in vivo

Objectives

TNBG-5602 is a newly synthesized compound with an isoquinoline structure. In the present study, we demonstrated the anticancer effect of TNBG-5602 in in-vitro and in-vivo models and investigated its possible anticancer mechanism.

Methods

The antiproliferation effect of TNBG-5602 in vitro was evaluated in human liver cancer cell line QGY-7701. The acute toxicity of TNBG-5602 was evaluated in mice. The anticancer activity of TNBG-5602 in vivo was assessed in a xenograft model of human liver cancer cell line QGY-7701.

Key findings

The results of CCK-8 assay showed that TNBG-5602 can effectively inhibit the proliferation of liver cancer cells in vitro. The acute toxicity test in mice showed that the LD50 of TNBG-5602 was 172 mg/kg. In a xenograft liver cancer model, TNBG-5602 could remarkably inhibit the growth of tumours. During in-vitro and in-vivo studies, we noted that TNBG-5602 could induce lipid accumulation in cancer cells and tissues. Further study indicated that the anticancer effect of TNBG-5602 may be exerted through activating peroxisome proliferator-activated receptor γ (PPARγ) and downregulating proliferating cell nuclear antigen (PCNA).

Conclusions

Our results suggested that TNBG-5602 might exert potent anticancer activity through increasing the expression of PPARγ.

Molecular iodine impairs chemoresistance mechanisms, enhances doxorubicin retention and induces downregulation of the CD44+/CD24+ and E-cadherin+/vimentin+ subpopulations in MCF-7 cells resistant to low doses of doxorubicin

One of the most dreaded clinical events for an oncology patient is resistance to treatment. Chemoresistance is a complex phenomenon based on alterations in apoptosis, the cell cycle and drug metabolism, and it correlates with the cancer stem cell phenotype and/or epithelial-mesenchymal transition. Molecular iodine (I2) exerts an antitumor effect on different types of iodine-capturing neoplasms by its oxidant/antioxidant properties and formation of iodolipids. In the present study, wild-type breast carcinoma cells (MCF-7/W) were treated chronically with 10 nM doxorubicin (DOX) to establish a low-dose DOX-resistant mammary cancer model (MCF-7/D). MCF-7/D cells were established after 30 days of treatment when the culture showed a proliferation rate similar to that of MCF-7/W. These DOX-resistant cells also showed increases in p21, Bcl-2 and MDR-1 expression. Supplementation with 200 µM I2 exerted similar effects in both cell lines: it decreased the proliferation rate by ~40%, and I2 co-administration with DOX significantly increased the inhibitory effect (to ~60%) and also increased apoptosis (BAX/Bcl-2 index), principally by inhibiting Bcl-2 expression. The inhibition by I2 + DOX was also accompanied by impaired MDR-1 induction as well as by a significant increase in PPARγ expression. All of these changes could be attributed to enhanced DOX retention and differential down-selection of CD44+/CD24+ and E-cadherin+/vimentin+ subpopulations. I2 + DOX-selected cells showed a weak induction of xenografts in Foxn1nu/nu mice, indicating that the iodine supplements reversed the tumorogenic capacity of the MCF-7/D cells. In conclusion, I2 is able to reduce the drug resistance and invasive capacity of mammary cancer cells exposed to DOX and represents an anti-chemoresistance agent with clinical potential.

Lipid Droplets: A Key Cellular Organelle Associated with Cancer Cell Survival under Normoxia and Hypoxia

The Warburg effect describes the phenomenon by which cancer cells obtain energy from glycolysis even under normoxic (O₂-sufficient) conditions. Tumor tissues are generally exposed to hypoxia owing to inefficient and aberrant vasculature. Cancer cells have multiple molecular mechanisms to adapt to such stress conditions by reprogramming the cellular metabolism. Hypoxia-inducible factors are major transcription factors induced in cancer cells in response to hypoxia that contribute to the metabolic changes. In addition, cancer cells within hypoxic tumor areas have reduced access to serum components such as nutrients and lipids. However, the effect of such serum factor deprivation on cancer cell biology in the context of tumor hypoxia is not fully understood. Cancer cells are lipid-rich under normoxia and hypoxia, leading to the increased generation of a cellular organelle, the lipid droplet (LD). In recent years, the LD-mediated stress response mechanisms of cancer cells have been revealed. This review focuses on the production and functions of LDs in various types of cancer cells in relation to the associated cellular environment factors including tissue oxygenation status and metabolic mechanisms. This information will contribute to the current understanding of how cancer cells adapt to diverse tumor environments to promote their survival.

Serum Unsaturated Free Fatty Acids: A Potential Biomarker Panel for Early-Stage Detection of Colorectal Cancer

Background: To screen biomarkers to differentiate early-stage colorectal cancer (CRC) from benign colorectal disease (BCD) and healthy controls.

Materials & Methods: Quantitative and qualitative analysis of C_16:1, C_18:3, C_18:2, C_18:1, C_20:4, and C_22:6 in 185 healthy controls, 55 patients with BCD, and 139 patients with CRC was performed. Comparisons of their levels in between CRC patients, BCD patients, and healthy controls were performed using Mann-Whitney U test.

Results: Serum levels of C_16:1, C_18:3, C_18:2, C_18:1, C_20:4, and C_22:6 in CRC patients were significantly decreased compared with healthy controls and BCD patients. A combination of C_16:1, C_18:2, C_20:4, and C_22:6 has excellent diagnostic performance to differentiate early-stage CRC patients from healthy controls plus BCD patients, with an AUC of 0.926, a sensitivity of 84.6%, and a specificity of 89.8%.

Conclusions: Serum levels of C_16:1, C_18:2, C_20:4, and C_22:6 could be diagnostic indicators of early-stage CRC patients.

JNK implication in adipocyte-like cell death induced by chemotherapeutic drug cisplatin

Recent evidence shows that tumor microenvironment containing heterogeneous cells may be involved in cancer initiation, growth and tumor cell response to anticancer therapy. Chemotherapy was designed to make toxic impact on malicious cells in organisms, however, the means to protect healthy cells against chemical toxicity are still unsuccessful. As known, the majority of tumor surrounding cells are cancer-associated adipocytes which influence cancer development, progression and treatment. Targeting the components of tumor microenvironment in combination with conventional cancer treatment may become an effective cancer therapy strategy. However, little is known about adipocyte death mechanisms during combined chemo- and targeted therapy. The importance of c-Jun-NH<inf>2</inf>-terminal kinase (JNK) signaling in tumor development and treatment has been demonstrated using various in vitro and in vivo cancer models. The aim of this study was to ascertain adipocyte viability during simultaneous stress kinase JNK inhibition and exposure to one of the most commonly used anticancer drugs cis-diamminedichloroplatinum II (cisplatin). Our model involved adipocyte-like cells (ADC) which were obtained during in vitro differentiation of adult rabbit muscle-derived stem cells. Cisplatin induced apoptotic cell death. During 24-hr cisplatin treatment gradual, strong and prolonged increase of both JNK and its target protein c-Jun phosphorylation was found in ADC. Pre-treatment of cells with SP600125 decreased cisplatin-induced activation of c-Jun and promoted apoptosis. Upregulation of proapoptotic Bax and downregulation of antiapoptotic Bcl-2 proteins were found to be regulated in JNK-dependent manner. Thus, the results prove the antiapoptotic role of activated JNK in adipocyte-like cells treated with cisplatin.

c-Flip KO fibroblasts display lipid accumulation associated with endoplasmic reticulum stress

c-Flip proteins are well-known apoptosis modulators. They generally contribute to tissue homeostasis maintenance by inhibiting death-receptor-mediated cell death. In the present manuscript, we show that c-Flip knock-out (KO) mouse embryonic fibroblasts (MEFs) kept in culture under starvation conditions gradually modify their phenotype and accumulate vacuoles, becoming progressively larger according to the duration of starvation. Large vacuoles are present in KO MEFs though not in WT MEFs, and are Oil Red-O positive, which indicates that they represent lipid droplets. Western blot experiments reveal that, unlike WT MEFs, KO MEFs express high levels of the lipogenic transcription factor PPAR-γ. Lipid droplet accumulation was found to be associated with endoplasmic reticulum (ER) stress activation and autophagic modulation valuated by means of BIP increase, LC3 lipidation and AMP-activated protein kinase (AMPK) phosphorylation, and p62 accumulation. Interestingly, XBP-1, an ER stress-induced lipogenic transcription factor, was found to preferentially localize in the nucleus rather than in the cytoplasm of KO MEFs. These data demonstrate that, upon starvation, c-Flip affects lipid accumulation, ER stress and autophagy, thereby pointing to an important role of c-Flip in the adaptive response and ER stress response programs under both normal and pathological conditions.

Emerging role of cancer stem cells in the biology and treatment of ovarian cancer: basic knowledge and therapeutic possibilities for an innovative approach

In 2013 there will be an estimated 22,240 new diagnoses and 14,030 deaths from ovarian cancer in the United States. Despite the improved surgical approach and the novel active drugs that are available today in clinical practice, about 80% of women presenting with late-stage disease have a 5-year survival rate of only 30%. In the last years a growing scientific knowledge about the molecular pathways involved in ovarian carcinogenesis has led to the discovery and evaluation of several novel molecular targeted agents, with the aim to test alternative models of treatment in order to overcome the clinical problem of resistance. Cancer stem cells tend to be more resistant to chemotherapeutic agents and radiation than more differentiated cellular subtypes from the same tissue. In this context the study of ovarian cancer stem cells is taking on an increasingly important strategic role, mostly for the potential therapeutic application in the next future. In our review, we focused our attention on the molecular characteristics of epithelial ovarian cancer stem cells, in particular on possible targets to hit with targeted therapies.

Cancerous ovarian stem cells: obscure targets for therapy but relevant to chemoresistance

Chemotherapy with platinum and taxanes is the first line of treatment for all epithelial ovarian cancer (EOC) patients after debulking surgery. Even though the treatment is initially effective in 80% of patients, recurrent cancer is inevitable in the vast majority of cases. Emerging evidence suggests that some tumor cells can survive chemotherapy by activating the self-renewal pathways resulting in tumor progression and clinical recurrence. These defined population of cells commonly termed as "cancer stem cells" (CSC) may generate the bulk of the tumor by using differentiating pathways. These cells have been shown to be resistant to chemotherapy and, to have enhanced tumor initiating abilities, suggesting CSCs as potential targets for treatment. Recent studies have introduced a new paradigm in ovarian carcinogenesis which proposes in situ carcinoma at the fimbrial end of the fallopian tube to generate high-grade serous ovarian carcinomas, in contrast to ovarian cortical inclusion cysts (CIC) which produce borderline and low grade serous, mucinous, endometrioid, and clear cell carcinomas. This review summarizes recent advances in our understanding of the cellular origin of EOC and the molecular mechanisms defining the basis of CSC in EOC progression and chemoresistance. Using a model ovarian cancer cell line, we highlight the role of CSC in response to chemotherapy, and relate how CSCs may impact on chemoresistance and ultimately recurrence. We also propose the molecular targeting of CSCs and suggest ways that may improve the efficacy of current chemotherapeutic regimens needed for the management of this disease.

Ovarian cancer stem cells: a new target for cancer therapy

Ovarian cancer is a highly lethal disease among all gynecologic malignancies and is the fifth leading cause of cancer-related death in women. Although the standard combination of surgery and chemotherapy was initially effective in patients with ovarian cancer, disease relapse commonly occurred due to the generation of chemoresistance. It has been reported that cancer stem cells (CSCs) are involved in drug resistance and cancer recurrence. Over the past decades, increasing studies have been done to identify CSCs from human ovarian cancer cells. The present paper will summarize different investigations on ovarian CSCs, including isolation, mechanisms of chemoresistance, and therapeutic approaches. Although there are still numerous challenges to translate basic research to clinical applications, understanding the molecular details of CSCs is essential for developing effective strategies to prevent ovarian cancer and its recurrence.

Overcoming challenges of ovarian cancer stem cells: novel therapeutic approaches

Understanding the genetic and molecular mechanisms of ovarian cancer has been the focus of research efforts working toward the greater goal of improving cancer therapy for patients with residual disease after initial treatment with conventional surgery and neoadjuvant chemotherapy. The focus of this review will be centered on new therapeutic strategies based on Cancer Stem Cells studies of chemoresistant subpopulations, the prevention of metastasis, and individualized therapy in order to find the most successful combination of treatments to effectively treat human ovarian cancer. We reviewed recent literature (1993-2011) of novel treatment approaches to ovarian cancer stem cells. As the focus of ovarian cancer investigation has centered on the cancer stem cell model and the complexities that it presents in the development of effective treatments, the future of treating ovarian cancer lies in utilizing individualized treatment systems that include enhancing existing treatments, aiming for novel therapy targets, managing the plasticity of stem cells to induce cellular differentiation, and regulating oncogenic signaling pathways.

Attributes of Oct4 in stem cell biology: perspectives on cancer stem cells of the ovary

Epithelial ovarian cancer (EOC) remains the most lethal of all the gynaecological malignancies with drug resistance and recurrence remaining the major therapeutic barrier in the management of the disease. Although several studies have been undertaken to understand the mechanisms responsible for chemoresistance and subsequent recurrence in EOC, the exact mechanisms associated with chemoresistance/recurrence continue to remain elusive. Recent studies have shown that the parallel characteristics commonly seen between embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSC) are also shared by a relatively rare population of cells within tumors that display stem cell-like features. These cells, termed 'cancer initiating cells' or 'cancer stem cells (CSCs)' have been shown not only to display increased self renewal and pluripotent abilities as seen in ESCs and iPSCs, but are also highly tumorigenic in in vivo mouse models. Additionally, these CSCs have been implicated in tumor recurrence and chemoresistance, and when isolated have consistently shown to express the master pluripotency and embryonic stem cell regulating gene Oct4. This article reviews the involvement of Oct4 in cancer progression and chemoresistance, with emphasis on ovarian cancer. Overall, we highlight why ovarian cancer patients, who initially respond to conventional chemotherapy subsequently relapse with recurrent chemoresistant disease that is essentially incurable.

Transdifferentiation of MALME-3M and MCF-7 Cells toward Adipocyte-like Cells is Dependent on Clathrin-mediated Endocytosis

Abstract

Enforced cell transdifferentiation of human cancer cells is a promising alternative to conventional chemotherapy. We previously identified albumin-associated lipid- and, more specifically, saturated fatty acid-induced transdifferentiation programs in human cancer cells (HCCLs). In this study, we further characterized the adipocyte-like cells, resulting from the transdifferentiation of human cancer cell lines MCF-7 and MALME-3M, and proposed a common mechanistic approach for these transdifferentiating programs. We showed the loss of pigmentation in MALME-3M cells treated with albumin-associated lipids, based on electron microscopic analysis, and the overexpression of perilipin 2 (PLIN2) by western blotting in MALME-3M and MCF-7 cells treated with unsaturated fatty acids. Comparing the gene expression profiles of naive melanoma MALME-3M cells and albumin-associated lipid-treated cells, based on RNA sequencing, we confirmed the transcriptional upregulation of some key adipogenic gene markers and also an alternative splicing of the adipogenic master regulator PPARG, that is probably related to the reported up regulated expression of the protein. Most importantly, these results also showed the upregulation of genes responsible for Clathrin (CLTC) and other adaptor-related proteins. An increase in CLTC expression in the transdifferentiated cells was confirmed by western blotting. Inactivation of CLTC by chlorpromazine (CHP), an inhibitor of CTLC mediated endocytosis (CME), and gene silencing by siRNAs, partially reversed the accumulation of neutral lipids observed in the transdifferentiated cells. These findings give a deeper insight into the phenotypic changes observed in HCCL to adipocyte-like transdifferentiation and point towards CME as a key pathway in distinct transdifferentiation programs.

Disclosures

Simon C and Aguilar-Gallardo C are co-inventors of the International Patent Application No. PCT/EP2011/004941 entitled “Methods for tumor treatment and adipogenesis differentiation”.

Electronic supplementary material

The online version of this article (doi:10.1186/2193-1801-1-44) contains supplementary material, which is available to authorized users.