Reactivation of proliferin gene expression is associated with increased angiogenesis in a cell culture model of fibrosarcoma tumor progression

Nature's Elixir for Cancer Treatment: Targeting Tumor-induced Neovascularization

Angiogenesis, a multistep process, involves sprouting of new vessels from the pre-existing vessels in response to a stimulus in its microenvironment. Normally, angiogenesis is important for tissue maintenance and homeostasis, however it is also known to be associated with various pathologies, including cancer. Importantly, neovascularization is very crucial for tumors to grow and metastasize since it allows delivery of oxygen and nutrients as well as promotes tumor cell dissemination to distant sites. Activation of angiogenic switch is a consequence of imbalance in pro- as well as anti-angiogenic factors, that are immensely impacted by reactive oxygen species and epigenetic regulation. Several reports have suggested that angiogenic inhibitors significantly inhibit tumor growth. Therefore, anti-angiogenic therapy has gained substantial attention and has been considered a rational approach in cancer therapeutics. In this line, several anti- angiogenic drugs have been approved, however, their long term usage caused several side effects. In view of this, researchers switched to plant-based natural compounds for identifying safe and cost-effective anti-angiogenic drugs. Of note, various phytochemicals have been evaluated to reduce tumor growth by inhibiting tumor-induced angiogenesis. Moreover, the implication of nano-carriers to enhance the bioavailability of phytochemicals has proven to be more efficient anti-cancer agents. The present review highlights the existing knowledge on tumor-induced neovascularization and its regulation at the epigenetic level. Further, we emphasize the inhibitory effect of phytochemicals on tumor- induced angiogenesis that will open up new avenues in cancer therapeutics.

Proliferin-1 Ameliorates Cardiotoxin-Related Skeletal Muscle Repair in Mice

Background

We recently demonstrated that proliferin-1 (PLF-1) functions as an apoptotic cell-derived growth factor and plays an important role in vascular pathobiology. We therefore investigated its role in muscle regeneration in response to cardiotoxin injury.

Methods and Results

To determine the effects of PLF-1 on muscle regeneration, we used a CTX-induced skeletal muscle injury model in 9-week-old male mice that were administered with the recombinant PLF-1 (rPLF-1) or neutralizing PLF-1 antibody. The injured muscles exhibited increased levels of PLF-1 gene expression in a time-dependent manner. On day 14 after injury, rPLF-1 supplementation ameliorated CTX-induced alterations in muscle fiber size, interstitial fibrosis, muscle regeneration capacity, and muscle performance. On day 3 postinjury, rPLF-1 increased the levels of proteins or genes for p-Akt, p-mTOR, p-GSK3α/β, p-Erk1/2, p-p38MAPK, interleukin-10, Pax7, MyoD, and Cyclin B1, and it increased the numbers of CD34⁺/integrin-α7⁺ muscle stem cells and proliferating cells in the muscles and/or bone marrow of CTX mice. An enzyme-linked immunosorbent assay revealed that rPLF-1 suppressed the levels of plasma tumor necrosis factor-α and interleukin-1β in CTX mice. PLF-1 blocking accelerated CTX-related muscle damage and dysfunction. In C2C12 myoblasts, rPLF-1 increased the levels of proteins for p-Akt, p-mTOR, p-GSK3α/β, p-Erk1/2, and p-p38MAPK as well as cellular functions; and these effects were diminished by the depletion of PLF-1 or silencing of its mannose-6-phosphate receptor.

Conclusions

These findings demonstrated that PLF-1 can improve skeletal muscle repair in response to injury, possibly via the modulation of inflammation and proliferation and regeneration, suggesting a novel therapeutic strategy for the management of skeletal muscle diseases.

Direct Reprogramming Induces Vascular Regeneration Post Muscle Ischemic Injury

Reprogramming non-cardiomyocytes (non-CMs) into cardiomyocyte (CM)-like cells is a promising strategy for cardiac regeneration in conditions such as ischemic heart disease. Here, we used a modified mRNA (modRNA) gene delivery platform to deliver a cocktail, termed 7G-modRNA, of four cardiac-reprogramming genes—Gata4 (G), Mef2c (M), Tbx5 (T), and Hand2 (H)—together with three reprogramming-helper genes—dominant-negative (DN)-TGFβ, DN-Wnt8a, and acid ceramidase (AC)—to induce CM-like cells. We showed that 7G-modRNA reprogrammed 57% of CM-like cells in vitro. Through a lineage-tracing model, we determined that delivering the 7G-modRNA cocktail at the time of myocardial infarction reprogrammed ∼25% of CM-like cells in the scar area and significantly improved cardiac function, scar size, long-term survival, and capillary density. Mechanistically, we determined that while 7G-modRNA cannot create de novo beating CMs in vitro or in vivo, it can significantly upregulate pro-angiogenic mesenchymal stromal cells markers and transcription factors. We also demonstrated that our 7G-modRNA cocktail leads to neovascularization in ischemic-limb injury, indicating CM-like cells importance in other organs besides the heart. modRNA is currently being used around the globe for vaccination against COVID-19, and this study proves this is a safe, highly efficient gene delivery approach with therapeutic potential to treat ischemic diseases.

Upregulation of Nogo-B by hypoxia inducible factor-1 and activator protein-1 in hepatocellular carcinoma

Nogo-B is an important regulator of tumor angiogenesis. Expression of Nogo-B is remarkably upregulated in multiple tumor types, especially hepatocellular carcinoma (HCC). Here, we show the transcriptional regulation mechanisms of Nogo-B in liver cancer. In response to hypoxia, expression of Nogo-B significantly increased in HCC tissues and cells. The distal hypoxia-responsive element in the promoter was essential for transcriptional activation of Nogo-B under hypoxic conditions, which is the specific site for hypoxia inducible factor-1α (HIF-1α) binding. In addition, Nogo-B expression was associated with c-Fos expression in HCC tissues. Nogo-B expression was induced by c-Fos, yet inhibited by a dominant negative mutant A-Fos. Deletion and mutation analysis of the predicted activator protein-1 binding sites revealed that functional element mediated the induction of Nogo-B promoter activity, which was confirmed by ChIP. These results indicate that HIF-1α and c-Fos induce the expression of Nogo-B depending on tumor microenvironments, such as hypoxia and low levels of nutrients, and play a role in upregulation of Nogo-B in tumor angiogenesis.

Tumor-secreted proliferin-1 regulates adipogenesis and lipolysis in cachexia

Cancer-associated cachexia (CAC) is a common syndrome in cancer patients and is characterized by loss of body weight accompanied by the atrophy of fat and skeletal muscle. Metabolic changes are a critical factor in CAC; however, the mechanisms through which tumors inhibit adipogenesis and promote lipolysis are poorly understood. To clarify these mechanisms, we investigated adipogenesis-limiting factors released by tumors in a cell culture system. We identified proliferin-1 (PLF-1), a member of the growth hormone/prolactin gene family, as a key factor secreted from certain tumors that inhibited preadipocyte maturation and promoted the lipolysis of mature adipocytes. Importantly, mice transplanted with PLF-1-depleted tumor cells were protected from fat loss due to CAC. These data show that tumor-secreted PLF-1 plays an essential role in impaired adipogenesis and accelerated lipolysis and is a potential therapeutic target against CAC.

Emerging Role of AP-1 Transcription Factor JunB in Angiogenesis and Vascular Development

Blood vessels are essential for the formation and maintenance of almost all functional tissues. They play fundamental roles in the supply of oxygen and nutrition, as well as development and morphogenesis. Vascular endothelial cells are the main factor in blood vessel formation. Recently, research findings showed heterogeneity in vascular endothelial cells in different tissue/organs. Endothelial cells alter their gene expressions depending on their cell fate or angiogenic states of vascular development in normal and pathological processes. Studies on gene regulation in endothelial cells demonstrated that the activator protein 1 (AP-1) transcription factors are implicated in angiogenesis and vascular development. In particular, it has been revealed that JunB (a member of the AP-1 transcription factor family) is transiently induced in endothelial cells at the angiogenic frontier and controls them on tip cells specification during vascular development. Moreover, JunB plays a role in tissue-specific vascular maturation processes during neurovascular interaction in mouse embryonic skin and retina vasculatures. Thus, JunB appears to be a new angiogenic factor that induces endothelial cell migration and sprouting particularly in neurovascular interaction during vascular development. In this review, we discuss the recently identified role of JunB in endothelial cells and blood vessel formation.

Selective antagonism of cJun for cancer therapy

The activator protein-1 (AP-1) family of transcription factors modulate a diverse range of cellular signalling pathways into outputs which can be oncogenic or anti-oncogenic. The transcription of relevant genes is controlled by the cellular context, and in particular by the dimeric composition of AP-1. Here, we describe the evidence linking cJun in particular to a range of cancers. This includes correlative studies of protein levels in patient tumour samples and mechanistic understanding of the role of cJun in cancer cell models. This develops an understanding of cJun as a focal point of cancer-altered signalling which has the potential for therapeutic antagonism. Significant work has produced a range of small molecules and peptides which have been summarised here and categorised according to the binding surface they target within the cJun-DNA complex. We highlight the importance of selectively targeting a single AP-1 family member to antagonise known oncogenic function and avoid antagonism of anti-oncogenic function.

PLF-1 (Proliferin-1) Modulates Smooth Muscle Cell Proliferation and Development of Experimental Intimal Hyperplasia

Background Although apoptosis and cell proliferation have been extensively investigated in atherosclerosis and restenosis postinjury, the communication between these 2 cellular events has not been evaluated. Here, we report an inextricable communicative link between apoptosis and smooth muscle cell proliferation in the promotion of vascular remodeling postinjury. Methods and Results Cathepsin K-mediated caspase-8 maturation is a key initial step for oxidative stress-induced smooth muscle cell apoptosis. Apoptotic cells generate a potential growth-stimulating signal to facilitate cellular mass changes in response to injury. One downstream mediator that cathepsin K regulates is PLF-1 (proliferin-1), which can potently stimulate growth of surviving neighboring smooth muscle cells through activation of PI3K/Akt/p38MAPK (phosphatidylinositol 3-kinase/protein kinase B/p38 mitogen-activated protein kinase)-dependent and -independent mTOR (mammalian target of rapamycin) signaling cascades. We observed that cathepsin K deficiency substantially mitigated neointimal hyperplasia by reduction of Toll-like receptor-2/caspase-8-mediated PLF-1 expression. Interestingly, PLF-1 blocking, with its neutralizing antibody, suppressed neointima formation and remodeling in response to injury in wild-type mice. Contrarily, administration of recombinant mouse PLF-1 accelerated injury-induced vascular actions. Conclusions This is the first study detailing PLF-1 as a communicator between apoptosis and proliferation during injury-related vascular remodeling and neointimal hyperplasia. These data suggested that apoptosis-driven expression of PLF-1 is thus a novel target for treatment of apoptosis-based hyperproliferative disorders.

Tobacco chemical-induced mouse lung adenocarcinoma cell lines pin the prolactin orthologue proliferin as a lung tumour promoter

Lung adenocarcinoma (LADC) is the leading cause of cancer death worldwide. Nevertheless, syngeneic mouse models of the disease are sparse, and cell lines suitable for transplantable and immunocompetent mouse models of LADC remain unmet needs. We established multiple mouse LADC cell lines by repeatedly exposing two mouse strains (FVB, Balb/c) to the tobacco carcinogens urethane or diethylnitrosamine and by culturing out the resulting lung tumours for prolonged periods of time. Characterization of the resulting cell lines (n = 7) showed that they were immortal and phenotypically stable in vitro, and oncogenic, metastatic and lethal in vivo. The primary tumours that gave rise to the cell lines, as well as secondary tumours generated by transplantation of the cell lines, displayed typical LADC features, such as glandular architecture and mucin and thyroid transcription factor 1 expression. Moreover, these cells exhibited marked molecular similarity with human smokers' LADC, including carcinogen-specific Kras point mutations (KrasQ61R in urethane- and KrasQ61H in diethylnitrosamine-triggered cell lines) and Trp53 deletions and displayed stemness features. Interestingly, all cell lines overexpressed proliferin, a murine prolactin orthologue, which functioned as a lung tumour promoter. Furthermore, prolactin was overexpressed and portended poor prognosis in human LADC. In conclusion, we report the first LADC cell lines derived from mice exposed to tobacco carcinogens. These cells closely resemble human LADC and provide a valuable tool for the functional investigation of the pathobiology of the disease.

Fibronectin Regulation of Integrin B1 and SLUG in Circulating Tumor Cells

Metastasis is the leading cause of cancer death worldwide. Circulating tumor cells (CTCs) are a critical step in the metastatic cascade and a good tool to study this process. We isolated CTCs from a syngeneic mouse model of hepatocellular carcinoma (HCC) and a human xenograft mouse model of castration-resistant prostate cancer (CRPC). From these models, novel primary tumor and CTC cell lines were established. CTCs exhibited greater migration than primary tumor-derived cells, as well as epithelial-to-mesenchymal transition (EMT), as observed from decreased E-cadherin and increased SLUG and fibronectin expression. Additionally, when fibronectin was knocked down in CTCs, integrin B1 and SLUG were decreased, indicating regulation of these molecules by fibronectin. Investigation of cell surface molecules and secreted cytokines conferring immunomodulatory advantage to CTCs revealed decreased major histocompatibility complex class I (MHCI) expression and decreased endostatin, C-X-C motif chemokine 5 (CXCL5), and proliferin secretion by CTCs. Taken together, these findings indicate that CTCs exhibit distinct characteristics from primary tumor-derived cells. Furthermore, CTCs demonstrate enhanced migration in part through fibronectin regulation of integrin B1 and SLUG. Further study of CTC biology will likely uncover additional important mechanisms of cancer metastasis.

Integrin Regulation of CAF Differentiation and Function

Extensive remodeling of the extracellular matrix, together with paracrine communication between tumor cells and stromal cells, contribute to an “activated” tumor microenvironment that supports malignant growth and progression. These stromal cells include inflammatory cells, endothelial cells, and cancer-associated fibroblasts (CAFs). Integrins are expressed on all tumor and stromal cell types where they regulate both cell adhesion and bidirectional signal transduction across the cell membrane. In this capacity, integrins control pro-tumorigenic cell autonomous functions such as growth and survival, as well as paracrine crosstalk between tumor cells and stromal cells. The myofibroblast-like properties of cancer-associated fibroblasts (CAFs), such as robust contractility and extracellular matrix (ECM) deposition, allow them to generate both chemical and mechanical signals that support invasive tumor growth. In this review, we discuss the roles of integrins in regulating the ability of CAFs to generate and respond to extracellular cues in the tumor microenvironment. Since functions of specific integrins in CAFs are only beginning to emerge, we take advantage of a more extensive literature on how integrins regulate wound myofibroblast differentiation and function, as some of these integrin functions are likely to extrapolate to CAFs within the tumor microenvironment. In addition, we discuss the roles that integrins play in controlling paracrine signals that emanate from epithelial/tumor cells to stimulate fibroblasts/CAFs.

Divergent roles of lysyl oxidase family members in ornithine decarboxylase- and RAS-transformed mouse fibroblasts and human melanoma cells

We have previously shown that proto-oncoprotein c-Jun is activated in ornithine decarboxylase (ODC)- and RAS-transformed mouse fibroblasts, and that the transformed morphology of these cells can be reversed by expressing the transactivation domain deletion mutant of c-Jun (TAM67). Here, we found that lysyl oxidase (Lox), encoding an extracellular matrix-modifying enzyme, is downregulated in a c-Jun-dependent manner in ODC-transformed fibroblasts (Odc cells). In addition to Lox, the Lox family members Lox-like 1 and 3 (Loxl1 and Loxl3) were found to be downregulated in Odc as well as in RAS-transformed fibroblasts (E4), whereas Lox-like 4 (Loxl4) was upregulated in Odc and downregulated in E4 cells compared to normal N1 fibroblasts. Tetracycline-regulatable LOX re-expression in Odc cells led to inhibition of cell growth and invasion in three-dimensional Matrigel in an activity-independent manner. On the contrary, LOX and especially LOXL2, LOXL3, and LOXL4 were found to be upregulated in several human melanoma cell lines, and LOX inhibitor B-aminopropionitrile inhibited the invasive growth of these cells particularly when co-cultured with fibroblasts in Matrigel. Knocking down the expression of LOX and especially LOXL2 in melanoma cells almost completely abrogated the invasive growth capability. Further, LOXL2 was significantly upregulated in clinical human primary melanomas compared to benign nevi, and high expression of LOXL2 in primary melanomas was associated with formation of metastases and shorter survival of patients. Thus, our studies reveal that inactive pro-LOX (together with Lox propeptide) functions as a tumor suppressor in ODC- and RAS-transformed murine fibroblasts by inhibiting cell growth and invasion, and active LOX and LOXL2 as tumor promoters in human melanoma cells by promoting their invasive growth.

Palbociclib inhibits epithelial-mesenchymal transition and metastasis in breast cancer via c-Jun/COX-2 signaling pathway

Palbociclib, a highly selective CDK4/6 inhibitor, has been shown to be a novel anti-tumor agent that suppresses breast cancer cell proliferation. However, its anti-metastasis activity remains controversial. In the present study, we evaluated whether palbociclib prevented breast cancer cell metastasis and revealed its regulatory mechanism. We found that palbociclib inhibited migration and invasion in the breast cancer cells MDA-MB-231 and T47D. The epithelial-mesenchymal transition (EMT) markers, vimentin and Snail, were down-regulated with palbociclib treatment. Moreover, we revealed that this inhibition was mediated by the c-Jun/COX-2 pathway. COX-2 was decreased after palbociclib treatment. The production of PGE2 was also reduced along with COX-2. Additionally, our data showed that c-Jun, a crucial transcriptional regulator of COX-2, was down-regulated by palbociclib. We found that palbociclib weakened the COX-2 promoter binding activity of c-Jun and prevented its translocation from the cytoplasm to cell nuclei. Bioluminescence imaging and tail intravenous injection were used to evaluate the anti-metastasis effect of palbociclib in vivo. The data demonstrated that palbociclib reduced breast cancer metastasis to the lung. These results therefore demonstrated that the anti-metastasis activity of palbociclib is mediated via the c-Jun/COX-2 signaling pathway by inhibiting EMT in breast cancer cells.

C-Jun recruits the NSL complex to regulate its target gene expression by modulating H4K16 acetylation and promoting the release of the repressive NuRD complex

The proto-oncogene c-Jun plays essential roles in various cellular processes, including cell proliferation, cell differentiation, and cellular apoptosis. Enormous efforts have been made to understand the mechanisms regulating c-Jun activation. The males absent on the first (MOF)-containing non-specific lethal (NSL) complex has been shown to positively regulate gene expression. However, the biological function of the NSL complex is largely unknown. Here we present evidence showing that c-Jun recruits the NSL complex to c-Jun target genes upon activation. The NSL complex catalyzes H4K16 acetylation at c-Jun target genes, thereby promoting c-Jun target gene transcription. More interestingly, we also found that the NSL complex promotes the release of the repressive NuRD complex from c-Jun target genes, thus activating c-Jun. Our findings not only reveal a new mechanism regulating c-Jun activation, but also identify the NSL complex as a c-Jun co-activator in c-Jun-regulated gene expression, expanding our knowledge of the function of the NSL complex in gene expression regulation.

MiR-1284 modulates multidrug resistance of gastric cancer cells by targeting EIF4A1

Routine chemotherapy as an important treatment mode often can not be effective because of multidrug resistance (MDR). MicroRNA (miRNA) modulates the expression of a great number of genes, including MDR. In this study, the expression of miR-1284 was reduced in gastric cancer (GC) tissue specimens with metastasis and in vincristine-resistant (VCR) GC SGC7901 cells (SGC-7901/VCR) compared to that in the controls. Recombinant lentiviral vectors with miR-1284 led to the overexpression of miR-1284 mRNA and reversed the chemoresistance of SGC7901/VCR cells, promoted cell cycle arrested at the G0/G1 phase, accelerated drug-induced apoptosis, and decreased migration and invasiveness of SGC-7901/VCR. In addition, the overexpression of miR-1284 sensitized tumors to chemotherapy in vivo. Our data provide combined evidence that miR-1284 can heighten the expression of MYC and reduce the expression of JUN, MMP12, and EIF4A1 that was the direct target. In conclusion, miR-1284 can function as a new regulator to reduce GC MDR cells by targeting EIF4A1.

The Bromodomain BET Inhibitor JQ1 Suppresses Tumor Angiogenesis in Models of Childhood Sarcoma

The bromodomain and extra-terminal domain inhibitor JQ1 has marked antitumor activity against several hematologic malignancies as well as solid tumor models. Here, we investigated its activity in vitro and in vivo against models of childhood rhabdomyosarcoma and Ewing sarcoma. In vitro, JQ1 (but not the inactive enantiomer JQ1R) inhibited cell proliferation and increased G1 fraction of cells, although there was no correlation between cell line sensitivity and suppression of c-MYC or MYCN. In vivo, xenografts showed significant inhibition of growth during the period of treatment, and rapid regrowth after treatment was stopped, activity typical of antiangiogenic agents. Furthermore, xenografts derived from cell lines intrinsically resistant or sensitive to JQ1 in vitro had similar sensitivity in vivo as xenografts. Further investigation showed that JQ1 reduced tumor vascularization. This was secondary to both drug-induced downregulation of tumor-derived growth factors and direct effects of JQ1 on vascular elements. JQ1 suppressed VEGF-stimulated vascularization of Matrigel plugs in mice, and in vitro suppressed differentiation, proliferation, and invasion of human umbilical cord vascular endothelial cells (HUVEC). In HUVECs, JQ1 partially suppressed c-MYC levels, but dramatically reduced AP-1 levels and activity through suppression of the AP-1-associated protein FOSL1. Our data suggest that the antitumor activity of JQ1 in these sarcoma models is largely a consequence of its antiangiogenic activity. Mol Cancer Ther; 15(5); 1018-28. ©2016 AACR.

Role of Msi1 and MAML1 in Regulation of Notch Signaling Pathway in Patients with Esophageal Squamous Cell Carcinoma

PURPOSE

Developmental pathways such as Wnt and Notch are involved in different cellular functions from the cell cycle regulation to self-renewal. Therefore, aberrations in these pathways may cause tumorigenesis. Msi1 has a critical regulatory role for the Wnt and Notch pathways. In the present study, we have assessed the probable correlation between the Msi1 and MAML1 in esophageal squamous cell carcinoma (ESCC) progression and metastasis.

METHODS

Levels of Msi1 and MAML1 mRNA expression in 51 ESCC patients were compared to the normal tissues using real-time polymerase chain reaction (PCR).

RESULTS

Nine out of 51 (17.6 %) cases had Msi1/MAML1 overexpression, and there was a significant correlation between such overexpressed cases and tumor location (p = 0.013).

CONCLUSIONS

We showed that there is not any direct correlation and feedback between the Msi1 and MAML1 in ESCC patients.

FBXW7 overexpression suppresses renal cancer cell proliferation and induces apoptosis

FBXW7 gene (F-box and WD-40 domain protein 7) is also named HCDC4 and is a significant tumor suppressor gene, which can regulate human cell cycle, proliferation and differentiation. In this study, we tend to investigate protein expression and related biological functions of FBXW7 gene. FBXW7 expression level in renal cell carcinoma (RCC) tissues is highly related to its clinical pathologic grade (P = 0.0094) and TNM phase (P = 0.0080) and is highly lower than in paracancerous normal tissues through immunohistochemistry study. FBXW7 high-expression patients have overall better prognosis than low-expression patients (P < 0.001). After transfected with FBXW7 plasmid, the RCC cell lines ACHN and A704 showed a depressed proliferation activity and high proportion of apoptosis through CCK8, colony formation and flow cytometry assay studies. By Western blot analysis, expression of cell proliferation-activating protein c-Myc and c-Jun is downregulated in FBXW7 high-expression RCC compared with negative control. These data suggested that FBXW7 is a significant tumor suppressor gene in RCC.

A positive feedback loop between prolactin and STAT5 promotes angiogenesis

The signal transduction events that orchestrate cellular activities required for angiogenesis remain incompletely understood. We and others recently described that proangiogenic mediators such as fibroblast growth factors can activate members of the signal transducers and activators of transcription (STAT) family. STAT5 activation is necessary and sufficient to induce migration, invasion and tube formation of endothelial cells. STAT5 effects on endothelial cells require the secretion of the prolactin (PRL) family member proliferin-1 (PLF1) in mice and PRL in humans. In human endothelial cells, PRL activates the PRL receptor (PRLR) resulting in MAPK and STAT5 activation, thus closing a positive feedback loop. In vivo, endothelial cell-derived PRL is expected to combine with PRL of tumor cell and pituitary origin to raise the concentration of this polypeptide hormone in the tumor microenvironment. Thus, PRL may stimulate tumor angiogenesis via autocrine, paracrine, and endocrine pathways. The disruption of tumor angiogenesis by interfering with PRL signaling may offer an attractive target for therapeutic intervention.

Angiogenic factors in chronic lymphocytic leukaemia (CLL): Where do we stand?

The role of angiogenesis in haematological malignancies such as chronic lymphocytic leukaemia (CLL) is difficult to envision, because leukaemia cells are not dependent on a network of blood vessels to support basic physiological requirements. Regardless, CLL cells secrete high levels of major angiogenic factors, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and platelet derived growth factor (PDGF). Nonetheless, it remains unclear how most angiogenic factors regulate accumulation and delayed apoptosis of CLL cells. Angiogenic factors such as leptin, granulocyte colony-stimulating factor (G-CSF), follistatin, angiopoietin-1 (Ang1), angiogenin (ANG), midkine (MK), pleiotrophin (PTN), progranulin (PGRN), proliferin (PLF), placental growth factor (PIGF), and endothelial locus-1 (Del-1), represent novel therapeutic targets of future CLL research but have remained widely overlooked. This review aims to outline our current understanding of angiogenic growth factors and their relationship with CLL, a still uncured haematopoietic malignancy.

Suppression of acetylpolyamine oxidase by selected AP-1 members regulates DNp73 abundance: mechanistic insights for overcoming DNp73-mediated resistance to chemotherapeutic drugs

Enhanced resistance to chemotherapy has been correlated with high levels of Delta-Np73 (DNp73), an anti-apoptotic protein of the p53 tumor-suppressor family which inhibits the pro-apoptotic members such as p53 and TAp73. Although genotoxic drugs have been shown to induce DNp73 degradation, lack of mechanistic understanding of this process precludes strategies to enhance the targeting of DNp73 and improve treatment outcomes. Antizyme (Az) is a mediator of ubiquitin-independent protein degradation regulated by the polyamine biosynthesis pathway. We show here that acetylpolyamine oxidase (PAOX), a catabolic enzyme of this pathway, upregulates DNp73 levels by suppressing its degradation via the Az pathway. Conversely, downregulation of PAOX activity by siRNA-mediated knockdown or chemical inhibition leads to DNp73 degradation in an Az-dependent manner. PAOX expression is suppressed by several genotoxic drugs, via selected members of the activator protein-1 (AP-1) transcription factors, namely c-Jun, JunB and FosB, which are required for stress-mediated DNp73 degradation. Finally, chemical- and siRNA-mediated inhibition of PAOX significantly reversed the resistant phenotype of DNp73-overexpressing cancer cells to genotoxic drugs. Together, these data define a critical mechanism for the regulation of DNp73 abundance, and reveal that inhibition of PAOX could widen the therapeutic index of cytotoxic drugs and overcome DNp73-mediated chemoresistance in tumors.

Small molecule inhibitors targeting activator protein 1 (AP-1)

Activator protein 1 (AP-1) is a pivotal transcription factor that regulates a wide range of cellular processes including proliferation, apoptosis, differentiation, survival, cell migration, and transformation. Accumulating evidence supports that AP-1 plays an important role in several severe disorders including cancer, fibrosis, and organ injury, as well as inflammatory disorders such as asthma, psoriasis, and rheumatoid arthritis. AP-1 has emerged as an actively pursued drug discovery target over the past decade. Excitingly, a selective AP-1 inhibitor T-5224 (51) has been investigated in phase II human clinical trials. Nevertheless, no effective AP-1 inhibitors have yet been approved for clinical use. Despite significant advances achieved in understanding AP-1 biology and function, as well as the identification of small molecules modulating AP-1 associated signaling pathways, medicinal chemistry efforts remain an urgent need to yield selective and efficacious AP-1 inhibitors as a viable therapeutic strategy for human diseases.

AP-1/c-Jun transcription factors: regulation and function in malignant melanoma

Malignant melanoma is an aggressive form of skin cancer with an increasing incidence worldwide. One way to address the pathology of the disease is through molecular research. In addition to the analysis of melanoma-relevant signaling pathways, the investigation of important transcription factors is a fundamental objective. The AP-1 transcription factor family is known to play an important role in melanoma progression and development. The AP-1 family member c-Jun is highly expressed and active in melanoma cells, and the mechanisms and signaling pathways regulating c-Jun protein are diverse. In addition to the common regulation and activation of c-Jun by mitogen-activated protein kinases (MAPKs), there are several other signaling pathways and interactions leading to c-Jun protein expression and thus AP-1 activation. In malignant melanoma, and many other cancer types, c-Jun has mainly oncogenic functions; however, other AP-1 proteins also have anti-oncogenic roles. Interestingly, several studies have revealed that a strong AP-1 activity in melanoma mainly depends on c-Jun. Recently, it has also been shown that the c-Jun protein is regulated and activated by several other mechanisms, including miRNAs and the cytoskeleton. In summary, there are a variety of mechanisms underlying the induction of c-Jun protein expression and activity leading to tumor progression and development, and this diverse regulatory machinery is due to the heterogeneity of different tumor types, particularly in malignant melanoma.

The prognostic significance of Jun transcription factors in ovarian cancer

PURPOSE

The Jun proteins (c-Jun, JunD and JunB) play an important role in the regulation of cell proliferation, apoptosis and angiogenesis. It is well established that these proteins participate in the carcinogenesis and progression in several tumour types. However, little is known about the prognostic significance of Jun proteins in patients with invasive epithelial ovarian carcinoma.

METHODS

We analysed fresh-frozen tissues of 161 ovarian cancer patients by using Western blot analysis to investigate protein levels of JunB, JunD, c-Jun and phosphorylated c-Jun (pc-Jun Ser63). The results were correlated with clinicopathologic prognostic parameters and survival data.

RESULTS

A high pc-Jun expression was significantly associated with shorter progression-free survival (14 vs. 16 months, p = 0.017) and overall survival (25 vs. 41 months, p = 0.038). In case of JunD, moderate protein levels were associated with a better prognosis, leading to longer progression-free and overall survival compared to weak or strong JunD expression (PFS in cases with weak/moderate/strong JunD expression: 14 vs. 19.5 vs. 16 months, p = 0.011; OAS: 32 vs. 42 vs. 35.5 months, p = 0.009). Multivariate Cox regression analysis confirmed an independent and significant impact of pc-Jun and JunD on the patient's prognosis.

CONCLUSIONS

Our results show that Jun proteins (pc-Jun and JunD) influence carcinogenesis and tumour progression, suggesting a significant role as prognostic predictors in human ovarian carcinoma.

Angiogenesis induced by signal transducer and activator of transcription 5A (STAT5A) is dependent on autocrine activity of proliferin

Multiple secreted factors induce the formation of new blood vessels (angiogenesis). The signal transduction events that orchestrate the numerous cellular activities required for angiogenesis remain incompletely understood. We have shown previously that STAT5 plays a pivotal role in angiogenesis induced by FGF2 and FGF8b. To delineate the signaling pathway downstream of STAT5, we expressed constitutively active (CA) or dominant-negative (DN) mutant STAT5A in mouse brain endothelial cells (EC). We found that the conditioned medium from CA-STAT5A but not from dominant-negative STAT5A overexpressing EC is sufficient to induce EC invasion and tube formation, indicating that STAT5A regulates the secretion of autocrine proangiogenic factors. Conversely, CA-STAT5A-induced conditioned medium had no effect on EC proliferation. Using a comparative genome-wide transcription array screen, we identified the prolactin family member proliferin (PLF1 and PLF4) as a candidate autocrine factor. The CA-STAT5A-dependent transcription and secretion of PLF by EC was confirmed by quantitative RT-PCR and Western blotting, respectively. CA-STAT5A binds to the PLF1 promoter region, suggesting a direct transcriptional regulation. Knockdown of PLF expression by shRNA or by blocking of PLF activity with neutralizing antibodies removed the CA-STAT5A-dependent proangiogenic activity from the conditioned medium of EC. Similarly, the ability of concentrated conditioned medium from CA-STAT5A transfected EC to induce angiogenesis in Matrigel plugs in vivo was abolished when PLF was depleted from the medium. These observations demonstrate a FGF/STAT5/PLF signaling cascade in EC and implicate PLF as autocrine regulator of EC invasion and tube formation.

Bridging sequence diversity and tissue-specific expression by DNA methylation in genes of the mouse prolactin superfamily

Much of the DNA in genomes is organized within gene families and hierarchies of gene superfamilies. DNA methylation is the main epigenetic event involved in gene silencing and genome stability. In the present study, we analyzed the DNA methylation status of the prolactin (PRL) superfamily to obtain insight into its tissue-specific expression and the evolution of its sequence diversity. The PRL superfamily in mice consists of two dozen members, which are expressed in a tissue-specific manner. The genes in this family have CpG-less sequences, and they are located within a 1-Mb region as a gene cluster on chromosome 13. We tentatively grouped the family into several gene clusters, depending on location and gene orientation. We found that all the members had tissue-dependent differentially methylated regions (T-DMRs) around the transcription start site. The T-DMRs are hypermethylated in nonexpressing tissues and hypomethylated in expressing cells, supporting the idea that the expression of the PRL superfamily genes is subject to epigenetic regulation. Interestingly, the DNA methylation patterns of T-DMRs are shared within a cluster, while the patterns are different among the clusters. Finally, we reconstituted the nucleotide sequences of T-DMRs by converting TpG to CpG based on the consideration of a possible conversion of 5-methylcytosine to thymine by spontaneous deamination during the evolutionary process. On the phylogenic tree, the reconstituted sequences were well matched with the DNA methylation pattern of T-DMR and orientation. Our study suggests that DNA methylation is involved in tissue-specific expression and sequence diversity during evolution.

c-Jun binding site identification in K562 cells

Determining the binding sites of the transcription factor is important for understanding of transcriptional regulation. Transcription factor c-Jun plays an important role in cell growth, differentiation and development, but the binding sites and the target genes are not clearly defined in the whole human genome. In this study, we performed a ChIP-Seq experiment to identify c-Jun binding site in the human genome. Forty-eight binding sites were selected to process further evaluation by dsDNA microarray assay. We identified 283 c-Jun binding sites in K562 cells. Data analysis showed that 48.8% binding sites located within 100 kb of the upstream of the annotated genes, 28.6% binding sites comprised consensus TRE/CRE motif (5'-TGAC/GTCA-3', 5'-TGACGTCA-3') and variant sequences. Forty-two out of the selected 48 binding sites were found to bind the c-Jun homodimer in dsDNA microarray analysis. Data analysis also showed that 1569 genes are located in the neighborhood of the 283 binding sites and 191 genes in the neighborhood of the 42 binding sites validated by dsDNA microarray. We consulted 38 c-Jun target genes in previous studies and 16 among these 38 genes were also detected in this study. The identification of c-Jun binding sites and potential target genes in the genome scale may improve our fundamental understanding in the molecular mechanisms underlying the transcription regulation related to c-Jun.

JNK signaling promotes intestinal tumorigenesis through activation of mTOR complex 1 in Apc(Δ716) mice

BACKGROUND & AIMS

Signaling by the mammalian target of rapamycin complex 1 (mTORC1) has been implicated in various human cancers. mTORC1 signaling is activated in intestinal tumors of adenomatous polyposis coli (Apc(Δ716)) mice, a model of familial adenomatous polyposis; in these mice, the mTORC1 inhibitor RAD001 can block tumor formation. However, the precise mechanism of mTORC1 signaling in intestinal tumors is not clear. We investigated whether c-Jun-NH(2) terminal kinase (JNK) is involved in the mTORC1 activation.

METHODS

We investigated the effects of an inhibitor and an activator of JNK, as well as small interfering RNA against JNK, on mTORC1 in Apc(Δ716) mice and colon cancer cell lines. We also determined the role of JNK in mTORC1 signaling using in vitro kinase assays.

RESULTS

JNK was activated in intestinal polyps of Apc((Δ716) mice); the JNK inhibitor SP600125 significantly suppressed tumor formation. In colorectal cancer cell lines, the JNK activator anisomycin activated mTORC1, whereas SP600125 or small interfering RNAs against JNK suppressed signaling. Importantly, JNK stimulated the mTORC1 kinase activity in vitro, through direct phosphorylation of Raptor at serine 863.

CONCLUSIONS

JNK is required for activation of mTORC1 in intestinal tumor cells. JNK inhibitors might be developed as therapeutics or to prevent development of intestinal tumors.

PPARgamma in placental angiogenesis

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor involved in diverse biological processes including adipocyte differentiation, glucose homeostasis, and inflammatory responses. Analyses of PPARγ knockout animals have been so far preempted by the early embryonic death of PPARγ-/- embryos as a consequence of the severe alteration of their placental vasculature. Using Sox2Cre/PPARγL2/L2 mice, we obtained fully viable PPARγ-null mice through specific and total epiblastic gene deletion, thereby demonstrating that the placental defect is the unique cause of PPARγ-/- embryonic lethality. The vasculature defects observed in PPARγ-/- placentas at embryonic d 9.5 correlated with an unsettled balance of pro- and antiangiogenic factors as demonstrated by increased levels of proliferin (Prl2c2, PLF) and decreased levels of proliferin-related protein (Prl7d1, PRP), respectively. To analyze the role of PPARγ in the later stage of placental development, when its expression peaks, we treated pregnant wild-type mice with the PPARγ agonist rosiglitazone. This treatment resulted in a disorganization of the placental layers and an altered placental microvasculature, accompanied by the decreased expression of proangiogenic genes such as Prl2c2, vascular endothelial growth factor, and Pecam1. Together our data demonstrate that PPARγ plays a pivotal role in controlling placental vascular proliferation and contributes to its termination in late pregnancy.

Animal models of soft-tissue sarcoma

Soft-tissue sarcomas (STSs) are rare mesenchymal tumors that arise from muscle, fat and connective tissue. Currently, over 75 subtypes of STS are recognized. The rarity and heterogeneity of patient samples complicate clinical investigations into sarcoma biology. Model organisms might provide traction to our understanding and treatment of the disease. Over the past 10 years, many successful animal models of STS have been developed, primarily genetically engineered mice and zebrafish. These models are useful for studying the relevant oncogenes, signaling pathways and other cell changes involved in generating STSs. Recently, these model systems have become preclinical platforms in which to evaluate new drugs and treatment regimens. Thus, animal models are useful surrogates for understanding STS disease susceptibility and pathogenesis as well as for testing potential therapeutic strategies.

Emerging roles of ATF2 and the dynamic AP1 network in cancer

Cooperation among transcription factors is central for their ability to execute specific transcriptional programmes. The AP1 complex exemplifies a network of transcription factors that function in unison under normal circumstances and during the course of tumour development and progression. This Perspective summarizes our current understanding of the changes in members of the AP1 complex and the role of ATF2 as part of this complex in tumorigenesis.

Identification of integrins alpha6 and beta7 as c-Jun- and transformation-relevant genes in highly invasive fibrosarcoma cells

Understanding the mechanisms of tumor cell invasion is essential for our attempts to prevent cancer deaths. We screened by DNAmicroarrays the c-Jun- and transformation-related gene expression changes in S-adenosylmethionine decarboxylase (AdoMetDC)-overexpressing mouse fibroblasts that are highly invasive in vivo, and their derivatives expressing a tetracycline-inducible dominant-negative mutant of c-Jun (TAM67) or c-Jun shRNA. Among the small set of target genes detected were integrins alpha6 and beta7, cathepsin L and thymosin beta4, all upregulated in the AdoMetDC-transformed cells and downregulated upon reversal of transformation by TAM67 or c-Jun shRNA. The upregulation of integrin alpha6 subunit, pairing with integrin beta1, endowed the transformed cells with the capability to attach to basement membrane laminin and to spread. Further, inhibition of integrin alpha6 or beta1 function with neutralizing antibodies blocked the invasiveness of AdoMetDC-transformants and human HT-1080 fibrosarcoma cells in three-dimensional Matrigel. Moreover, immunohistochemical analyses showed strong integrin alpha6 staining in high-grade human fibrosarcomas. Our data show that c-Jun can regulate all three key steps of invasion: cell adhesion (integrin alpha6), basement membrane/extracellular matrix degradation (cathepsin L) and cell migration (thymosin beta4). In addition, this is the first study to associate integrin beta7, known as a leukocyte-specific integrin binding to endothelial/epithelial cell adhesion molecules, with the transformed phenotype in cells of nonleukocyte origin. As tumor cell invasion is a prerequisite for metastasis, the observed critical role of integrin alpha6beta1 in fibrosarcoma cell invasion/spreading allures testing antagonists to integrin alpha6beta1, alone or combined with inhibitors of cathepsin L and thymosin beta4, as chemotherapeutic agents.

Alpha3beta1 integrin in epidermis promotes wound angiogenesis and keratinocyte-to-endothelial-cell crosstalk through the induction of MRP3

During cutaneous wound healing, epidermal keratinocytes play essential roles in the secretion of factors that promote angiogenesis. However, specific cues in the wound microenvironment that trigger the production of pro-angiogenic factors by keratinocytes, and the cellular receptors that mediate this response, remain unclear. In this study, we exploited a model of conditional integrin knockout to demonstrate impaired wound angiogenesis in mice that lack alpha3beta1 integrin in epidermis. In addition, we used genetic and shRNA approaches to determine that alpha3beta1-integrin deficiency in keratinocytes leads to reduced mRNA and protein expression of the pro-angiogenic factor mitogen-regulated protein 3 (MRP3; also known as PRL2C4), and to demonstrate that this regulation provides a mechanism of keratinocyte-to-endothelial-cell crosstalk that promotes endothelial-cell migration. Finally, we showed that the impaired wound angiogenesis in epidermis-specific alpha3-integrin-knockout mice is correlated with reduced expression of MRP3 in wounded epidermis. These findings identify a novel role for alpha3beta1 integrin in promoting wound angiogenesis through a mechanism of crosstalk from epidermal to endothelial cells, and they implicate MRP3 in this integrin-dependent crosstalk. Such a mechanism represents a novel paradigm for integrin-mediated regulation of wound angiogenesis that extends beyond traditional roles for integrins in cell adhesion and migration.

Musashi1: a stem cell marker no longer in search of a function

One of the earliest genes identified with stem and early progenitor cells is the RNA-binding protein, Musashi1 (Msi1). Through gene profiling of mammary epithelial cells transduced with Msi1, a unique autocrine signaling pathway was identified that activates both the Wnt and Notch pathways. This process was associated with increased secretion of the growth factor, PLF1 and inhibition of the secreted Wnt pathway inhibitor, DKK3. Identification of PLF1 as an effector of these pathways in the absence of the DKK3 tumor suppressor provides a new avenue for investigating differences between normal and malignant tissues, and potentially targeting tumor stem cells.

Identification of secreted proteins that mediate cell-cell interactions in an in vitro model of the lung cancer microenvironment

Non-small cell lung cancer (NSCLC) cells with somatic mutations in K-ras recruit to the tumor a variety of cell types (hereafter collectively termed "stromal cells") that can promote or inhibit tumorigenesis by mechanisms that have not been fully elucidated. Here, we postulated that stromal cells in the tumor microenvironment alter the tumor cell secretome, including those proteins required for tumor growth and dissemination, and we developed an in vitro model to test this hypothesis. Coculturing a murine K-ras mutant lung adenocarcinoma cell line (LKR-13) with a murine lung stromal cell (macrophage, endothelial cell, or fibroblast) enhanced stromal cell migration, induced endothelial tube formation, increased LKR-13 cell proliferation, and regulated the secretion of proteins involved in angiogenesis, inflammation, cell proliferation, and epithelial-to-mesenchymal transition. Among these proteins, CXCL1 has been reported to promote NSCLC development, whereas interleukin-18 (IL-18) has an undefined role. Genetic and pharmacologic strategies to inhibit CXCL1 and IL-18 revealed that stromal cell migration, LKR-13 cell proliferation, and LKR-13 cell tumorigenicity required one or both of these proteins. We conclude that stromal cells enhanced LKR-13 cell tumorigenicity partly through their effects on the secretome of LKR-13 cells. Strategies to inhibit tumor/stromal cell interactions may be useful as therapeutic approaches in NSCLC patients.

Musashi1 modulates mammary progenitor cell expansion through proliferin-mediated activation of the Wnt and Notch pathways

The RNA-binding protein Musashi1 (Msi1) is a positive regulator of Notch-mediated transcription in Drosophila melanogaster and neural progenitor cells and has been identified as a putative human breast stem cell marker. Here we describe a novel functional role for Msi1: its ability to drive progenitor cell expansion along the luminal and myoepithelial lineages. Expression of Msi1 in mammary epithelial cells increases the abundance of CD24(hi) Sca-1(+), CD24(hi) CD29(+), CK19, CK6, and double-positive CK14/CK18 progenitor cells. Proliferation is associated with increased proliferin-1 (PLF1) and reduced Dickkopf-3 (DKK3) secretion into the conditioned medium from Msi-expressing cells, which is associated with increased colony formation and extracellular signal-regulated kinase (ERK) phosphorylation. Treatment with the MEK inhibitor U0126 inhibits ERK activation and decreases Notch and beta-catenin/T-cell factor (TCF) reporter activity resulting from Msi1 expression. Reduction of DKK3 in control cells with a short hairpin RNA (shRNA) increases Notch and beta-catenin/TCF activation, whereas reduction of PLF1 with a shRNA in Msi1-expressing cells inhibits these pathways. These results identify Msi1 as a key determinant of the mammary lineage through its ability to coordinate cell cycle entry and activate the Notch and Wnt pathways by a novel autocrine process involving PLF1 and DKK3.

Expression and characterization of novel ovine orthologs of bovine placental prolactin-related proteins

Background

The prolactin-related proteins (PRPs) are non-classical placental-specific members of the prolactin/growth hormone family. Among ruminants, they are expressed in the cotyledonary villi of cattle and goat. We investigated placental PRP in sheep in order to gain a comprehensive understanding of the function and evolution of these molecules. We also examined the sequence properties, expression and lactogenic activation of the cloned genes.

Results

We cloned two novel ovine PRPs, named oPRP1 and oPRP2. oPRP2 had a typical PRP sequence similar to bovine PRP1 (bPRP1). oPRP1 had a short sequence identical with bovine or caprine type PRP but the reading frame was shifted. Both oPRPs were expressed in trophoblast giant binucleate cells (BNC) as in cattle and goat. oPRP1 expression declined from the early to the middle stage of gestation. In contrast, oPRP2 expression remained constant throughout the gestation period. oPRP2 was translated to form a mature protein in a mammalian cell expression system. Western blotting showed a molecular mass of 35 kDa for the FLAG-tag fusion oPRP2 protein. This recombinant protein and bPRP1 were bioassayed using Nb2 lymphoma cells; it was confirmed that neither ruminant PRP had lactogenic activity because the Nb2 lymphoma cells did not proliferate.

Conclusion

We have identified two novel PRPs, oPRP1 and oPRP2, in ovine placenta. Both these ovine PRPs were localized and quantitatively expressed in BNC. Absence of lactogenic activity was confirmed for the oPRP2 molecule. It is anticipated that novel and known ruminant PRPs have common functions, except for lactogenic activity.

Increased rate of hair regrowth in mice with constitutive overexpression of Del1

BACKGROUND

Developmental endothelial locus (Del)1 is a secreted extracellular matrix-associated protein that stimulates angiogenesis through integrin binding and is implicated in vasculogenesis. We hypothesized that increased expression of an angiogenic factor would lead to enhanced wound healing.

MATERIALS AND METHODS

Transgenic mice had Del1 cloned behind a keratin 14 promoter (K14-Del1) to drive constitutive expression in basal keratinocytes. Transgenic animals and wild-type litter mates underwent excisional wounding or depilation, and tissues were harvested at various time points. Wound healing and hair regrowth were assessed by photography, histology, and immunohistochemistry. For injection experiments, purified Del1 protein was injected in the flanks of wild-type mice with carrier on the contralateral flank as a control. Del1 expression during hair development was performed using transgenic mice with a LacZ cassette introduced downstream from the native promoter.

RESULTS

K14-Del1 animals appeared normal and healed excisional wounds normally but demonstrated an increased rate of hair regrowth after wound healing. Using depilation experiments to specifically address hair follicle growth, we found increased hair regrowth was independent of wounding. This was confirmed by injection of purified Del1 protein. During normal hair anagenesis, Del1 is expressed in the root of the hair follicle.

CONCLUSIONS

Constitutive expression of Del1 in skin does not affect skin vascularity or improve wound healing. Surprisingly, we found the primary effect of constitutive Del1 expression in the basal keratinocytes was increased hair growth following induction of anagenesis. During normal hair anagenesis, we see expression of Del1 in the root of the hair follicle suggesting it may function there to stimulate hair growth.

JUN oncogene amplification and overexpression block adipocytic differentiation in highly aggressive sarcomas

The human oncogene JUN encodes a component of the AP-1 complex and is consequently involved in a wide range of pivotal cellular processes, including cell proliferation, transformation, and apoptosis. Nevertheless, despite extensive analyses of its functions, it has never been directly involved in a human cancer. We demonstrate here that it is highly amplified and overexpressed in undifferentiated and aggressive human sarcomas, which are blocked at an early step of adipocyte differentiation. We confirm by cellular and xenograft mouse models recapitulating these sarcoma genetics that the failure to differentiate is dependent upon JUN amplification/overexpression.

The prolactin family: effectors of pregnancy-dependent adaptations

Prolactin (PRL) is a hormone involved in many biological functions. In some species, there is a family of PRL-related genes; such is the case in the mouse and rat. The actions of members of the PRL family can be distinguished based on the involvement of the PRL receptor signaling pathway (classical versus nonclassical). Recent insights into the biology of the PRL family have been derived from mouse mutagenesis studies. There is compelling evidence suggesting that the PRL family contributes to the regulation of pregnancy-dependent adaptations to physiological stressors.

Mass spectrometric proteomics profiles ofin vivo tumor secretomes: Capillary ultrafiltration sampling of regressive tumor masses

Identification of in vivo secreted peptides/proteins (secretomes) in tumor masses has the potential to provide important biomarkers and therapeutic targets for cancer therapy. However, limitations of existing technologies have made obtaining these secretomes for analysis extremely difficult. Here we employed an in vivo sampling technique using capillary ultrafiltration (CUF) probes to collect secretomes directly from tumor masses. Mass spectrometric proteomics approaches were then used to identify the tumor secretomes. A UV-induced skin fibrosarcoma cell line (UV-2240) was subcutaneously injected into C3H/NeH mice, resulting in tumor masses that initially progressed, then regressed and eventually eradicated. We then implanted CUF probes into tumor masses at the progressive and regressive stage. Five secreted proteins (cyclophilin-A, S100A4, profilin-1, thymosin beta 4 and 10), previously associated with tumor progression, were identified from tumor masses at the progressive stage. Five secreted proteins including three protease inhibitors (fetuin-A, alpha-1 antitrypsin 1-6, and contrapsin) were identified from tumor masses at the regressive stage. The technique involving CUF probes linked to mass spectrometric proteomics reinforces systems biology studies of cell-cell interactions and is potentially applicable to the discovery of in vivo biomarkers in human disease.

Proliferin enhances microvilli formation and cell growth of neuroblastoma cells

Proliferins (also termed mitogen-regulated proteins; MRP/PLFs) belong to the prolactin gene family. Mrp/Plfs are involved in angiogenesis of the uterus and placenta and maximally expressed during midgestation and decline through the remainder of the gestation period in mouse placenta. The tissue expressions of Mrp/Plfs are mainly documented in placenta, hair follicles of skin and in wound healing. In this report, we demonstrate that Plf1, Plf1 minus exon3, Plf2 and Mrp3 but not Mrp4 are expressed in mouse whole brain by diagnostic RT-PCR and Western blotting. The expression levels of Mrp/Plf mRNAs in mouse brains were low during the neonatal period, but higher in embryonic and adult stages, indicating Mrp/Plfs expression profiles are different in mouse brain and placenta. Interestingly, endogenous Mrp/Plfs were detected using immunostaining both in mouse brain sections and the neuroblastoma cell line, Neuro-2a cells. The function of PLF1 was explored by expressing exogenous PLF1 in Neuro-2a cells. This resulted in increased microvilli. Neuro-2a cells with stable expression of PLF1 had increased proliferation compared with normal and stable expressing EGFP cells when cell reached saturation density. Together these data, strongly suggest that MRP/PLFs mediate microvilli formation and contribute to cell proliferation of neuroblastoma cells.

The rat prolactin gene family locus: species-specific gene family expansion

In the rat there is a large family of paralogous genes related to prolactin (PRL). Members of the PRL family are expressed in cell- and temporal-specific patterns in the anterior pituitary, uterus, and placenta. An overriding feature of the PRL family is its association with pregnancy. In this investigation, we used information derived from the public rat genome database as a tool for identifying new members of the rat PRL family. The entire rat PRL gene family locus spans approximately 1.7 megabases (Mb) on Chromosome 17. Genes possessed either 5- or 6-exon organization patterns. We provide information on three newly identified genes orthologous to previously identified members of the mouse PRL gene family [placental lactogen-Ialpha (PL-Ialpha), PL-Ibeta, and proliferin (PLF)] and a new member of the PRL family, termed PRL-like protein-P (PLP-P). Information is also presented on the existence of multiple PLP-M transcripts, which are generated by alternative splicing. Expansion of the PRL family has occurred independently in rodents versus the cow and does not exist in the human and dog. Elucidation of the rat PRL gene family locus provides tools for studying the genetics and biology of the rat PRL family and new insights into species-specific gene family expansion.

Transcriptional regulators of angiogenesis

Angiogenesis, the process by which new blood vessels develop from a pre-existing vascular network, is essential for normal development and in certain physiological states. Inadequate or excessive angiogenesis has been incriminated in a number of pathologic states. For example, vaso-occlusive disease arising from atherosclerosis can lead to ischemia, a situation in which enhanced angiogenesis would be beneficial. Conversely, overzealous angiogenesis can contribute to tumor development and in this case inhibition of angiogenesis is desirable. Thus, strategies to induce or inhibit angiogenesis are of considerable therapeutic interest.

Characterization of medroxyprogesterone and DMBA-induced multilineage mammary tumors by gene expression profiling

Mouse mammary tumors arising during medroxyprogesterone-DMBA-mediated mammary carcinogenesis comprised three distinct phenotypes: adenocarcinoma, squamous cell carcinoma, and myoepithelial carcinoma. The molecular signature for each of the three tumor subsets was characterized by gene microarray analysis, and three distinct sets of gene expression profiles were obtained that were corroborated in part by quantitative RT-PCR and immunohistochemistry. These results suggest that this carcinogenesis and gene expression model will be useful for rapidly assessing the histopathological differences arising in mammary carcinogenesis and the effects of tumor promoting or chemoprevention agents.

Mitogen-regulated protein/proliferin mRNA induction following single applications of tumor promoters to murine skin

Mitogen-regulated protein/proliferin (mrp/plf) gene family transcripts rise in abundance as a response to diverse chemical and physical agents that promote morphological transformation in the murine C3H/10T1/2 cultured cell model of multi-step carcinogenesis. To determine if proliferin genes respond to tumor promoters in vivo, RNA was extracted from the whole skin of SENCAR mice after single applications of 2 or 20 microg 12-O-tetradecanoylphorbol-13-acetate (TPA); 3.2 or 32 nmole), 20 or 40 mg benzoyl peroxide (BPO; 83, 165 micromole), or acetone vehicle alone (2.72 mmole). RNA samples were prepared from treated skin areas, 2-48 h after painting. Mrp/plf-mRNA was not detected in Northern blot hybridizations, but large increases in mRNAs for ornithine decarboxylase gene and mRNA (odc), v-jun oncogene-related transcription factor gene and mRNA (junB), egr1 (early growth response protein gene and mRNA) were measured relative to beta 2 microglobulin gene and mRNA (b2m) mRNA in response to TPA. BPO induced small relative changes in these mRNAs. Reverse transcriptase (RT)-polymerase chain reactions (PCR) detected fully-processed MRP/plf-mRNA 16-48 h after TPA treatments in five of six animals, and in three of six BPO-treated animals. The MRP/plf-mRNA species expressed in the skin were predominantly plf1 and mrp3 as determined by gene-specific restriction enzyme sites within the RT-PCR products. Expression was either undetectable or found at low levels in acetone-painted controls and was not detected during the anagen phase of the normal hair growth cycle in unpainted animals. These results demonstrate that mrp/plf-mRNA is differentially expressed in murine skin in response to mechanistically distinct tumor promoters and has potential utility as a short-term biomarker for tumor promoting effects in chemical carcinogenesis.

Role of epidermal growth factor receptor signaling in RAS-driven melanoma

The identification of essential genetic elements in pathways governing the maintenance of fully established tumors is critical to the development of effective antioncologic agents. Previous studies revealed an essential role for H-RAS(V12G) in melanoma maintenance in an inducible transgenic model. Here, we sought to define the molecular basis for RAS-dependent tumor maintenance through determination of the H-RAS(V12G)-directed transcriptional program and subsequent functional validation of potential signaling surrogates. The extinction of H-RAS(V12G) expression in established tumors was associated with alterations in the expression of proliferative, antiapoptotic, and angiogenic genes, a profile consistent with the observed phenotype of tumor cell proliferative arrest and death and endothelial cell apoptosis during tumor regression. In particular, these melanomas displayed a prominent RAS-dependent regulation of the epidermal growth factor (EGF) family, leading to establishment of an EGF receptor signaling loop. Genetic complementation and interference studies demonstrated that this signaling loop is essential to H-RAS(V12G)-directed tumorigenesis. Thus, this inducible tumor model system permits the identification and validation of alternative points of therapeutic intervention without neutralization of the primary genetic lesion.