Lipogenesis and lipolysis: The pathways exploited by the cancer cells to acquire fatty acids

One of the most important metabolic hallmarks of cancer cells is enhanced lipogenesis. Depending on the tumor type, tumor cells synthesize up to 95% of saturated and mono-unsaturated fatty acids (FA) de novo in spite of sufficient dietary lipid supply. This lipogenic conversion starts early when cells become cancerous and further expands as the tumor cells become more malignant. It is suggested that activation of FA synthesis is required for carcinogenesis and for tumor cell survival. These observations suggest that the enzymes involved in FA synthesis would be rational therapeutic targets for cancer treatment. However, several recent reports have shown that the anti-tumor effects, following inhibition of endogenous FA synthesis in cancer cell lines may be obviated by adding exogenous FAs. Additionally, high intake of dietary fat is reported to be a potential risk factor for development and poor prognosis for certain cancers. Recently it was reported that breast and liposarcoma tumors are equipped for both de novo fatty acid synthesis pathway as well as LPL-mediated extracellular lipolysis. These observations indicate that lipolytically acquired FAs may provide an additional source of FAs for cancer. This review focuses on our current understanding of lipogenic and lipolytic pathways in cancer cell progression.     

Bilirubin Inhibits Tumor Cell Growth via Activation of ERK

Bilirubin for decades was considered a potentially toxic waste product of heme degradation until the discovery that it is a potent antioxidant. Accumulating data from observations in humans and experimental studies indicate that the bile pigment may be protective against certain diseases. Based on our own observations that bilirubin induces cell cycle arrest in abnormally proliferating vascular smooth muscle cells and clinical observations describing a lesser incidence of cancer in healthy individuals with high normal or slightly elevated serum bilirubin levels, we hypothesized that bilirubin might suppress tumor cell proliferation in vitro and in vivo. As possible effectors we analyzed key proteins that are involved in cell cycle progression and apoptosis. In vivo tumor growth was assessed in BALB/c nude mice bearing HRT-18 colon cancer xenografts that were treated with bilirubin. In vitro, we investigated the effect of bilirubin on various cell lines and the signaling pathways involved in bilirubin action on tumor cell proliferation in HRT-18 cells using western blots. Bilirubin potently inhibited tumor cell proliferation in vivo and acted cytostatic and pro-apoptotic in vitro. The signaling cascades responsible for this action involved induction of p53, p27, hypophosphorylation of the retinoblastoma tumor suppressor protein as well as caspase activation. These effects were dependent on ERK 1/2. Our study demonstrates that bilirubin may play a role in the defense against cancer by interfering with pro-cancerogenic signaling pathways.     

Kinase profiling of liposarcomas using RNAi and drug screening assays identified druggable targets

Background

Liposarcoma, the most common soft tissue tumor, is understudied cancer, and limited progress has been made in the treatment of metastatic disease. The Achilles heel of cancer often is their kinases that are excellent therapeutic targets. However, very limited knowledge exists of therapeutic critical kinase targets in liposarcoma that could be potentially used in disease management.

Methods

Large RNAi and small-molecule tyrosine kinase inhibitor screens were performed against the proliferative capacity of liposarcoma cell lines of different subtypes. Each small molecule inhibitor was either FDA approved or in a clinical trial.

Results

Screening assays identified several previously unrecognized targets including PTK2 and KIT in liposarcoma. We also observed that ponatinib, multi-targeted tyrosine kinase inhibitor, was the most effective drug with anti-growth effects against all cell lines. In vitro assays showed that ponatinib inhibited the clonogenic proliferation of liposarcoma, and this anti-growth effect was associated with apoptosis and cell cycle arrest at the G0/G1 phase as well as a decrease in the KIT signaling pathway. In addition, ponatinib inhibited in vivo growth of liposarcoma in a xenograft model.

Conclusions

Two large-scale kinase screenings identified novel liposarcoma targets and a FDA-approved inhibitor, ponatinib with clear anti-liposarcoma activity highlighting its potential therapy for treatment of this deadly tumor.

     

Cytomorphology of lipomatous tumors of soft tissue

OBJECTIVE: To evaluate the cytomorphologic features of benign and malignant lipomatous tumors of soft tissue on fine needle aspirates (FNA) and determine if the variants of liposarcoma could be identified. STUDY DESIGN: FNA of histologically documented benign (51 cases) and malignant (39 cases) lipomatous tumors were reviewed. Twenty-six of the 51 FNA from lipomas and 34 of the 39 FNA from malignant lipomatous tumors were satisfactory for evaluation. RESULTS: FNA from 26 cases of lipomas were cellular, with lobulated, fibroadipose tissue. Thin and thick capillaries were seen in 92% and 65% of cases, though a chicken wire vascular pattern was seen in only 4 cases (15%). A cytodiagnosis of liposarcoma could be made in 23 cases (88%), and these could be further subtyped into well-differentiated (4 cases), myxoid (8), pleomorphic (4), round cell (3) and liposarcoma, ?type (4). Only 50% of the well-differentiated liposarcomas, 3 of the 10 pleomorphic liposarcomas and 8 of the 17 myxoid liposarcomas were diagnosed as such on FNA. Cytologic diagnosis of the remaining 9 cases of myxoid liposarcoma were pleomorphic liposarcoma (1); liposarcoma, ?type (3); malignant mesenchymal tumor (1); suspicious for malignancy (2); and benign (2). There were no false positives, but there were 3 false negative cases (1 well-differentiated and 2 myxoid liposarcoma). CONCLUSION: Lipomas can be diagnosed readily. Arborizing vessels can be seen in lipomas and should be interpreted with caution. Subclassification of liposarcomas on FNA is possible but not very reliable. Myxoid liposarcomas pose a problem, and aspirates from them can mimic a wide range of morphologic subtypes. The role of FNA in identification of variants of liposarcoma is limited.     

Arbiter of differentiation and death: Notch signaling meets apoptosis.

Notch-ligand interactions are a highly conserved mechanism that regulates cell fate decisions. Over the past few years, numerous observations have shown that this mechanism operates to regulate cell differentiation in an enormous variety of developmental and cell maturation processes. Recent studies indicate that in addition to cell differentiation, Notch signaling has direct effects on proliferation and programmed cell death. The picture emerging from these findings suggests that, depending on cellular and developmental context, Notch signaling may function as a general "arbiter" of cell fate, regulating differentiation potential, rate of proliferation, and apoptotic cell death. In this review, we briefly summarize the current knowledge of the structure and function of Notch receptors and discuss the recent evidence that Notch signaling regulates apoptotic cell death. The possible mechanisms of this effect and its potential implications for developmental biology, immunobiology, neuropathology, and tumor biology are discussed.     

Synergistic Effects of Targeted PI3K Signaling Inhibition and Chemotherapy in Liposarcoma

While liposarcoma is the second most common soft tissue malignant tumor, the molecular pathogenesis in this malignancy is poorly understood. Our goal was therefore to expand the understanding of molecular mechanisms that drive liposarcoma and identify therapeutically-susceptible genetic alterations. We studied a cohort of high-grade liposarcomas and benign lipomas across multiple disease sites, as well as two liposarcoma cell lines, using multiplexed mutational analysis. Nucleic acids extracted from diagnostic patient tissue were simultaneously interrogated for 150 common mutations across 15 essential cancer genes using a clinically-validated platform for cancer genotyping. Western blot analysis was implemented to detect activation of downstream pathways. Liposarcoma cell lines were used to determine the effects of PI3K targeted drug treatment with or without chemotherapy. We identified mutations in the PIK3CA gene in 4 of 18 human liposarcoma patients (22%). No PIK3CA mutations were identified in benign lipomas. Western blot analysis confirmed downstream activation of AKT in both PIK3CA mutant and non-mutant liposarcoma samples. PI-103, a dual PI3K/mTOR inhibitor, effectively inhibited the activation of the PI3K/AKT in liposarcoma cell lines and induced apoptosis. Importantly, combination with PI-103 treatment strongly synergized the growth-inhibitory effects of the chemotherapy drugs doxorubicin and cisplatin in liposarcoma cells. Taken together, these findings suggest that activation of the PI3K/AKT pathway is an important cancer mechanism in liposarcoma. Targeting the PI3K/AKT/pathway with small molecule inhibitors in combination with chemotherapy could be exploited as a novel strategy in the treatment of liposarcoma.     

Temperature-dependent localization of TLS-CHOP to splicing factor compartments

The myxoid/round cell liposarcoma oncogene TLS-CHOP belongs to a growing family of tumor type specific fusion genes generated by chromosome translocations. We have recently found that the TLS-CHOP fusion protein is localized to well-defined nuclear structures, a pattern distinct from normal TLS or CHOP cellular distribution. Since location and function are intimately coupled in the organized nucleus, the aberrant localization of the fusion protein most certainly reflects the oncogenic activities of TLS-CHOP. We have investigated the role of the functionally unknown, SYGQ-rich, TLS N-terminal in the localization of TLS-CHOP to nuclear structures. Here, we report the temperature-dependent localization of TLS-CHOP to splicing factor compartments and association with Cajal bodies. Further, mutational analysis of the N-terminal part of green fluorescent protein-tagged TLS-CHOP identifies a region within the N-terminal required for colocalization with the splicing factor SC-35.     

Pathology and genetics of adipocytic tumors

Adipocytic tumors are common mesenchymal neoplasms with considerable morphologic and genetic heterogeneity. The fruitful integration of morphology and cytogenetics in the past 15 years has not only enhanced the diagnostic accuracy, but also refined the various pathological classifications and subtypes in these tumors. The current WHO classification includes eleven benign subtypes, one intermediate and five categories of malignant fatty neoplasms with incorporation of relevant genetic findings. Of the benign tumors, lipomas have been extensively analyzed by chromosome banding which has shown that their cytogenetic patterns are heterogeneous. Still aberrations involving 12q13-->q15, 6p23-->p21 and loss of material from 13q are common and consistent findings. Among the malignant tumors, the t(12;16)(q13;p11) resulting in the fusion of DDIT3 and FUS genes is the hallmark of myxoid and round cell liposarcoma and is used as a highly specific and sensitive marker of this entity. The tumor in the intermediate group, atypical lipomatous neoplasm/well-differentiated liposarcoma which poses morphologic challenges due to close histological similarity to benign lipomas shows characteristic supernumerary rings and giant rod chromosomes due to amplification of the 12q14-->q15 region often involving the MDM2 oncogene. This review will focus on the pathological features of the various adipocytic tumors and relevant genetic findings reported in the literature.     

Vasoactive intestinal peptide: autocrine growth factor in neuroblastoma.

Neuroblastoma is the most common solid tumor of children less than 5 years of age; yet the biology of this tumor is poorly understood. Neuroblastoma tumors are derived from neural crest precursors; they synthesize both adrenergic and peptidergic neurotransmitters. This study determined VIP receptor expression in primary neuroblastoma tumors prior to chemotherapy. The VIP receptor was expressed in 12 of 15 neuroblastoma tumors as determined by direct binding studies (KD = 1.3-12.4 nM) and VIP-mediated stimulation of adenylate cyclase. The VIP stimulation index for adenylate cyclase in the primary tumor was inversely correlated with the VIP content of the tumor, suggesting that VIP regulates its own receptor expression. Similar observations were made in vitro by comparison of two human neuroblastoma cell lines, IMR32 and SKNSH. Both cell lines were demonstrated to express specific, high affinity VIP receptors (KD = 4 nM and 2.5 nM for IMR32 and SKNSH, respectively). IMR32 cells contained very low levels of VIP (0.6 pg VIP/10(6) cells). Exogenous VIP stimulated adenylate cyclase 22-fold over basal activity and VIP inhibited proliferation of IMR32 cells by 49% in 6-day cultures. On the other hand, SKNSH cells synthesized high levels of VIP (6.3 pg/10(6) cells), metabolized VIP rapidly and demonstrated a low level of VIP-mediated stimulation of adenylate cyclase; their proliferation rate was minimally inhibited by exogenous VIP. These observations help validate the hypothesis that VIP serves as an autocrine growth factor in neuroblastoma.     

Pazopanib,a Receptor Tyrosine Kinase Inhibitor,Suppresses Tumor Growth through Angiogenesis in Dedifferentiated Liposarcoma Xenograft Models

INTRODUCTION: The rarity of dedifferentiated liposarcoma (DDLPS) and the lack of experimental DDLPS models limit the development of novel therapeutic strategies. Pazopanib (PAZ) is a tyrosine kinase inhibitor that is approved for the treatment of non-adipocytic advanced soft tissue sarcoma. The activity of this agent has not yet been properly explored in preclinical liposarcoma models nor in a randomized phase Ш clinical trial in this entity. The aim of the present study was to investigate whether PAZ had antitumor activity in DDLPS models in vivo. MATERIAL AND METHODS: We established two patient-derived DDLPS xenograft models (UZLX-STS3 and UZLX-STS5) through implantation of tumor material from sarcoma patients in athymic nude NMRI mice. An animal model of the SW872 liposarcoma cell line was also used. To investigate the efficacy of PAZ in vivo, mice bearing tumors were treated for 2 weeks with sterile water, doxorubicin (1.2 mg/kg, intraperitoneally, twice per week), PAZ [40 mg/kg, orally (p.o.), twice per day], or PAZ plus doxorubicin (same schedules as for single treatments). RESULTS: Patient-derived xenografts retained the histologic and molecular features of DDLPS. PAZ significantly delayed tumor growth by decreasing proliferation and inhibited angiogenesis in all models tested. Combining the angiogenesis inhibitor with an anthracycline did not show superior efficacy. CONCLUSION: These results suggest that PAZ has potential antitumor activity in DDLPS primarily through antiangiogenic effects and therefore should be explored in clinical trials.     

Depletion of intracellular putrescine and spermidine by alpha-difluromethylornithine does not inhibit proliferation of 9L rat brain tumor cells.

Incubation of 9L rat brain tumor cells with 25 mM DL-α-difluoromethylornithine inhibits cell proliferation, while treatment with 10 mM and 1 mM do not. All three concentrations cause equal degrees of depletion of intracellular putrescine and spermidine content, but have no effect on spermine content. These observations show that 9L cells can continue to proliferate in spite of significant polyamine depletion and leads one to question the role of polyamines in 9L cell replication. These observations also suggest that inhibition of 9L cell proliferation by 25 mM DL-α-difluormethylornithine is probably not due to its effect on ornithine decarboxylase or on intracellular polyamine content.     

Down-regulation of endothelial cell growth inhibitors by enhanced MYCN oncogene expression in human neuroblastoma cells.

Recent evidence indicates that the genetic alterations of the multistage process of malignant transformation appear to activate tumor neovascularization by altering the balance between stimulators and inhibitors of angiogenesis. In the present study, we have attempted to define the effect of enhanced MYCN oncogene expression on the profile of endothelial cell growth modulators in neuroblastoma cells. We report here that conditioned medium of human neuroblastoma cells with normal MYCN expression contains three inhibitors of endothelial cell proliferation, which appear to be novel proteins as judged by their physicochemical, immunological and biological properties. All three inhibitors are diminished or become undetectable upon experimental increase of MYCN expression. Our results suggest that enhanced MYCN expression in human neuroblastoma cells alters the angiogenic balance by down-regulating endothelial cell growth inhibitors but leaving the expression of the stimulators unaffected. These data shed light on the molecular mechanisms linking the genetic changes of malignant transformation with initiation of tumor angiogenesis. Moreover, our observations might explain the poor prognosis of human neuroblastomas following MYCN oncogene amplification through initiation of angiogenesis and subsequent tumor growth and spread.     

Focus: Rare Disease: Desmoplastic Small Round Cell Tumor in a Pregnant Woman: A Case Report and Literature Review

Background: Desmoplastic small round cell tumor (DSRCT) is an aggressive malignant tumor commonly found in young men; most occurs in the abdominal cavity. Here we conducted an in-depth analysis of a pregnant patient in our hospital and explored all the case information in the literature on small round cell carcinoma of women. Case presentation: A 27-year-old pregnant woman underwent tumor resection in our hospital at 29 weeks gestational age for a large progressive shoulder lump. The postoperative pathology showed that the mass was a DSRCT. Genetic testing found no fusion gene. At 36 weeks gestation, a painful mass was found in the breast and proved to be a metastatic focus of the desmoplastic small round cell tumor. Twenty days after a successful cesarean section at 40 weeks gestation, she received the VAC-IE chemotherapy regimen, successfully completed the first course, but when awaiting the next chemotherapy, unfortunately, the patient died during follow-up due to tumor recurrence and metastasis. Conclusion: The treatment of DSRCT in pregnant women requires a multidisciplinary consultation, and the treatment and examination during pregnancy are subject to many constraints, which may have a negative impact on the patient’s prognosis. Also, a review of the literature found that there is still no standard treatment protocol for DSRCT, and its prognosis in female patients is independent of age and tissue origin.     

Intraabdominal desmoplastic small round cell tumor. Report of a case diagnosed by fine needle aspiration cytology.

In this report, fine needle aspiration (FNA) findings in a case of intraabdominal desmoplastic small round cell tumor (IADSRCT) are presented. Computed tomographic scan-guided FNA performed on a right upper abdominal mass on a 20-year-old man produced a cellular specimen consisting of monomorphic small round cells with scant cytoplasm and ovoid nuclei. FNA cytology and immunocytochemistry suggested the diagnosis of IADSRCT. Surgical removal of the tumor and detailed histology and ultrastructural studies confirmed the cytologic findings.     

pRB, a tumor suppressor with a stabilizing presence

The product of the retinoblastoma tumor-susceptibility gene (RB1) is a key regulator of cell proliferation and this function is thought to be central to its tumor suppressive activity. Several studies have demonstrated that inactivation of pRB not only allows inappropriate proliferation but also undermines mitotic fidelity, leading to genome instability and ploidy changes. Such properties promote tumor evolution and correlate with increased resistance to therapeutics and tumor relapse. These observations suggest that inactivation of pRB could contribute to both tumor initiation and progression. Further characterization of the role of pRB in chromosome segregation will provide insight into processes that are misregulated in human tumors and could reveal new therapeutic targets to kill or stall these chromosomally unstable lesions. We review the evidence that pRB promotes genome stability and discuss the mechanisms that probably contribute to this effect.     

The in vivo differentiation of murine neuroblastoma

C1300 neuroblastoma was implanted with regenerating skeletal muscle to study the role of tissue interactions during tumor cell differentiation. Combined tumor-muscle implants, placed subcutaneously or within diffusion chambers were compared with control tumors implanted without muscle. Neuroblastoma implanted with injured muscle undergoes a partial neuronal differentiation. The tumor cells lose their normal round cell configuration and develop numerous cytoplasmic processes. Accompanying these outward changes are an increased content of microtubules in the neuritic processes; the appearance of glial-like processes containing abundant microfilaments; and the occurrence of growth vesicles identical to those of the growth cones of normal neurites. Although the implants usually contain large numbers of regenerated myofibers, tumor cell differentiation is not dependent upon the presence of these newly formed fibers. Tumor differentiation occurs equally well on the surfaces of degenerating muscle fragments, fibrin deposits and on the membrane surfaces of the diffusion chambers. These observations suggest that non-specific cell surface phenomena, rather than neuromuscular interactions were primarily responsible for the tumor cell differentiation in vivo.     

The integration of cell proliferation and growth in leaf morphogenesis

A number of recent publications have assessed the outcome on leaf development of targeted manipulation of cell proliferation. The results of these investigations have awakened interest in the long-standing debate in plant biology on the precise role of cell division in morphogenesis. Does cell proliferation drive morphogenesis (cell theory) or is it subservient to a mechanism which acts at the whole organ level to regulate morphogenesis (organismal theory)? In this review, the central role of growth processes (distinct from cell proliferation) in morphogenesis is highlighted and the limitations in our understanding of the basic mechanisms of plant growth control are highlighted. Finally, an attempt is made to demonstrate how sequential local co-ordination of growth might provide an interpretation of some of the recent observations on cell proliferation and leaf morphogenesis.