Fatty acid synthase is required for profibrotic TGF-ß signaling.

Evidence is provided that the fibroproliferative actions of TGF-ß are dependent on a metabolic adaptation that sustains pathologic growth. Specifically, profibrotic TGF-ß signaling is shown to require fatty acid synthase (FASN), an essential anabolic enzyme responsible for the de novo synthesis of fatty acids. With the use of pharmacologic and genetic approaches, we show that TGF-ß-stimulated FASN expression is independent of Smad2/3 and is mediated via mammalian target of rapamycin complex 1. In the absence of FASN activity or protein, TGF-ß-driven fibrogenic processes are reduced with no apparent toxicity. Furthermore, as increased FASN expression was also observed to correlate with the degree of lung fibrosis in bleomycin-treated mice, inhibition of FASN was examined in a murine-treatment model of pulmonary fibrosis. Remarkably, inhibition of FASN not only decreased expression of profibrotic targets, but lung function was also stabilized/improved, as assessed by peripheral blood oxygenation.-Jung, M.-Y., Kang, J.-H., Hernandez, D. M., Yin, X., Andrianifahanana, M., Wang, Y., Gonzalez-Guerrico, A., Limper, A. H., Lupu, R., Leof, E. B. Fatty acid synthase is required for profibrotic TGF-ß signaling.

Urinary CD80 Discriminates Among Glomerular Disease Types and Reflects Disease Activity.

INTRODUCTION: Heterogeneity of nephrotic diseases and a lack of validated biomarkers limits interventions and reduces the ability to examine outcomes. Urinary CD80 is a potential biomarker for minimal change disease (MCD) steroid-sensitive nephrotic syndrome (NS). We investigated and validated a CD80 enzyme-linked immunosorbent assay (ELISA) in urine in a large cohort with a variety of nephrotic diseases. METHODS: A commercial CD80 ELISA was enhanced and analytically validated for urine. Patients were from Mayo Clinic (307) and Nephrotic Syndrome Study Network Consortium (NEPTUNE; 104) as follows: minimal change disease (MCD, 56), focal segmental glomerulosclerosis (FSGS, 92), lupus nephritis (LN, 25), IgA nephropathy (IgAN, 20), membranous nephropathy (MN, 49), autosomal dominant polycystic kidney disease (ADPKD, 10), diabetic nephropathy (DN; 106), pyuria (19), and controls (34). Analysis was by Kruskal-Wallis test, generalized estimating equation (GEE) models, and receiver operating characteristic (AUC) curve. RESULTS: Urinary CD80/creatinine values were highest in MCD compared to other glomerular diseases and were increased in DN with proteinuria >2 compared to controls (control = 36 ng/g; MCD = 139 ng/g, P < 0.01; LN = 90 ng/g, P < 0.12; FSGS = 66 ng/g, P = 0.18; DN = 63, P = 0.03; MN = 69 ng/g, P = 0.33; ng/g, P = 0.07; IgA = 19 ng/g, P = 0.09; ADPKD = 42, P = 0.36; and pyuria 31, P = 0.20; GEE, median, P vs. control). In proteinuric patients, CD80 concentration appears to be independent of proteinuria levels, suggesting that it is unrelated to nonspecific passage across the glomeruli. CD80/creatinine values were higher in paired relapse versus remission cases of MCD and FSGS (P < 0.0001, GEE). CONCLUSION: Using a validated ELISA, urinary CD80 levels discriminate MCD from other forms of NS (FSGS, DN, IgA, MN) and primary from secondary FSGS.

PKC-mediated secretion of death factors in LNCaP prostate cancer cells is regulated by androgens.

Activation of PKCdelta in androgen-dependent LNCaP prostate cancer cells leads to apoptosis via the activation of p38 MAPK and JNK cascades. We have recently shown that treatment of LNCaP cells with phorbol 12-myristate 13-acetate (PMA) leads to a PKCdelta-mediated autocrine release of death factors, including the cytokines TNFalpha and TRAIL, and that conditioned medium (CM) collected from PMA-treated LNCaP cells promotes the activation of the extrinsic apoptotic cascade. Interfering with this autocrine loop either at the level of factor release or death receptor activation/signaling markedly impaired the PMA apoptotic response. In the present study we show that this PKCdelta-dependent autocrine mechanism is greatly influenced by androgens. Indeed, upon androgen depletion, which down-regulates PKCdelta expression, TNFalpha and TRAIL mRNA induction and release by PMA are significantly diminished, resulting in a reduced apoptogenic activity of the CM and an impaired ability of the CM to activate p38 MAPK and JNK. These effects can be rescued by addition of the synthetic androgen R1881. Furthermore, RNAi depletion of the androgen-receptor (AR) from LNCaP cells equally impaired PMA responses, suggesting that PKC-mediated induction of death factor secretion and apoptosis in LNCaP prostate cancer cells are highly sensitive to hormonal control.

Androgens regulate protein kinase Cdelta transcription and modulate its apoptotic function in prostate cancer cells.

Activation of protein kinase Cdelta (PKCdelta), a member of the novel PKC family, leads to apoptosis in several cell types. Although the molecular bases of PKCdelta activation are being unfolded, limited information is available on the mechanisms that control its expression. Here, we report that in prostate cancer cells PKCdelta is tightly regulated by androgens at the transcriptional level. Steroid depletion from the culture medium causes a pronounced down-regulation of PKCdelta protein and mRNA in androgen-sensitive LNCaP prostate cancer cells, an effect that is rescued by the androgen R1881 in an androgen receptor (AR)-dependent manner. Analysis of the PKCdelta promoter revealed a putative androgen responsive element (ARE) located 4.7 kb upstream from the transcription start site. Luciferase reporter assays show that this element is highly responsive to androgens, and mutations in key nucleotides in the AR-binding consensus abolish reporter activity. Furthermore, using chromatin immunoprecipitation assays, we determined that the AR binds in vivo to the PKCdelta ARE in response to androgen stimulation. Functional studies revealed that, notably, androgens modulate phorbol 12-myristate 13-acetate (PMA)-induced apoptosis in LNCaP cells, an effect that is dependent on PKCdelta. Indeed, androgen depletion or AR RNA interference severely impaired the apoptotic function of PKCdelta or the activation of p38, a downstream effector of PKCdelta in LNCaP cells--effects that can be rescued by restoring PKCdelta levels using an adenoviral delivery approach. Our studies identified a novel hormonal mechanism for the control of PKCdelta expression via transcriptional regulation that fine-tunes the magnitude of PKCdelta apoptotic responses.

Visinin-like protein-1 is a potent inhibitor of cell adhesion and migration in squamous carcinoma cells.

Tumor cell invasion is a highly integrated and complex process comprising several biologically distinct functions such as cell adhesion, motility, proteolysis, etc. Visinin-like protein-1 (VILIP-1), a member of the neuronal EF-hand calcium-sensor protein family, plays a role in regulating tumor cell invasiveness of mouse squamous cell carcinoma (SCC). VILIP-1 enhances cyclic adenosine monophosphate levels through PKA induction. However, the mechanism by which VILIP-1 reduces cell invasiveness is not well understood. In this study, we show that VILIP-1 decreased cell adhesion and migration/invasiveness of highly invasive mouse SCC cells. Forced expression of VILIP-1 reduced cell adhesion to fibronectin in parallel to downregulating alphav and alpha5 integrin subunit levels. VILIP-1 overexpression also led to decreased migration ability. Conversely, short hairpin RNA-mediated VILIP-1 knock-down of SCC cells' characterized by little or no invasiveness, correlated with increased adhesion to fibronectin and enhanced expression of alphav and alpha5 integrin subunits together with increased cell migration. Function-blocking assays with inhibitory anti-alpha5 and anti-alphav integrin antibodies showed that both subunits contributed to cell adhesion, migration, and invasiveness of highly invasive SCC cell lines. These results point to a critical role of VILIP-1 in regulating cell adhesion and migration by downregulation of fibronectin receptor expression. Decreased or absent VILIP-1 expression in SCC cell subpopulations may lead to a more advanced malignant phenotype characterized by changes in adhesive ability and increased cell motility, suggestive of a tumor suppressor function.

Overexpression of the calcium sensor visinin-like protein-1 leads to a cAMP-mediated decrease of in vivo and in vitro growth and invasiveness of squamous cell carcinoma cells.

Visinin-like protein-1 (VILIP-1) is a member of the neuronal EF-hand Ca(2+)-sensor protein family. VILIP-1 is expressed in the central nervous system where it plays a crucial role in regulating cAMP levels, cell signaling, and differentiation. Screening of mouse skin tumor cell lines for differentially expressed genes showed high-level VILIP-1 expression in less aggressive squamous cell carcinoma (SCC) and papilloma cell lines. Conversely, expression was markedly decreased or lost in invasive SCC and spindle cell carcinoma cell lines. In addition, immunohistochemistry of normal skin and primary tumors showed that VILIP-1 is expressed in basal cells of the normal intrafollicular epidermis as well as in basal cells of papillomas. The expression was decreased in low-grade SCCs and disappeared in most high-grade SCCs. When two high-grade carcinoma cell lines were transfected with VILIP1-cDNA, the VILIP-1 transfectants had significantly higher cAMP levels than the respective vector alone-transfected lines. VILIP-1-transfected cells were less invasive (both in vivo and in vitro) than the control transfectants. Reduced invasiveness and elevation of cAMP levels were accompanied by decreased MMP-9, as well as decreased RhoA activity. These results indicate that VILIP-1 plays an important role in regulating tumor cell invasiveness and that its loss could aid in enhancing the advanced malignant phenotype.

Suppression of endogenous lipogenesis induces reversion of the malignant phenotype and normalized differentiation in breast cancer.

The correction of specific signaling defects can reverse the oncogenic phenotype of tumor cells by acting in a dominant manner over the cancer genome. Unfortunately, there have been very few successful attempts at identifying the primary cues that could redirect malignant tissues to a normal phenotype. Here we show that suppression of the lipogenic enzyme fatty acid synthase (FASN) leads to stable reversion of the malignant phenotype and normalizes differentiation in a model of breast cancer (BC) progression. FASN knockdown dramatically reduced tumorigenicity of BC cells and restored tissue architecture, which was reminiscent of normal ductal-like structures in the mammary gland. Loss of FASN signaling was sufficient to direct tumors to a reversed phenotype that was near normal when considering the development of polarized growth-arrested acinar-like structure similar to those formed by nonmalignant breast cells in a 3D reconstituted basement membrane in vitro. This process, in vivo, resulted in a low proliferation index, mesenchymal-epithelial transition, and shut-off of the angiogenic switch in FASN-depleted BC cells orthotopically implanted into mammary fat pads. The role of FASN as a negative regulator of correct breast tissue architecture and terminal epithelial cell differentiation was dominant over the malignant phenotype of tumor cells possessing multiple cancer-driving genetic lesions as it remained stable during the course of serial in vivo passage of orthotopic tumor-derived cells. Transient knockdown of FASN suppressed hallmark structural and cytosolic/secretive proteins (vimentin, N-cadherin, fibronectin) in a model of EMT-induced cancer stem cells (CSC). Indirect pharmacological inhibition of FASN promoted a phenotypic switch from basal- to luminal-like tumorsphere architectures with reduced intrasphere heterogeneity. The fact that sole correction of exacerbated lipogenesis can stably reprogram cancer cells back to normal-like tissue architectures might open a new avenue to chronically restrain BC progression by using FASN-based differentiation therapies.

Molecular mechanisms of protein kinase C-induced apoptosis in prostate cancer cells.

Protein kinase C (PKC) isozymes, a family of serine-threonine kinases, are important regulators of cell proliferation and malignant transformation. Phorbol esters, the prototype PKC activators, cause PKC translocation to the plasma membrane in prostate cancer cells, and trigger an apoptotic response. Studies in recent years have determined that each member of the PKC family exerts different effects on apoptotic or survival pathways. PKCdelta, one of the novel PKCs, is a key player of the apoptotic response via the activation of the p38 MAPK pathway. Studies using RNAi revealed that depletion of PKCdelta totally abolishes the apoptotic effect of the phorbol ester PMA. Activation of the classical PKCalpha promotes the dephosphorylation and inactivation of the survival kinase Akt. Studies have assigned a pro-survival role to PKCepsilon, but the function of this PKC isozyme remains controversial. Recently, it has been determined that the PKC apoptotic effect in androgen-dependent prostate cancer cells is mediated by the autocrine secretion of death factors. PKCdelta stimulates the release of TNFalpha from the plasma membrane, and blockade of TNFalpha secretion or TNFalpha receptors abrogates the apoptotic response of PMA. Molecular analysis indicates the requirement of the extrinsic apoptotic cascade via the activation of death receptors and caspase-8. Dissecting the pathways downstream of PKC isozymes represents a major challenge to understanding the molecular basis of phorbol ester-induced apoptosis.

Heregulin in breast cancer: old story, new paradigm.

Heregulin (HRG), a combinatorial ligand for the epidermal growth factor receptor family, is expressed in about 30% of breast cancer tumors. HRG induces tumorigenicity and metastasis of breast cancer cells and promotes hormone-independent growth. Although HRG has been studied mostly in the context of the HRG receptor family, accumulating evidence suggests that HRG plays distinctive and causative roles in breast cancer tumorigenesis independent from the HRG receptors, demanding a comprehensive and independent study of HRG as a unique growth factor. This review provides a consolidated view of HRG and its biological role in the development, progression, and maintenance of breast cancer. Further, it provides further evidence that HRG is implicated in breast cancer resistance and targeting HRG may possibly be a beneficial tool to target a subgroup of breast carcinomas.

Phorbol ester-induced apoptosis in prostate cancer cells via autocrine activation of the extrinsic apoptotic cascade: a key role for protein kinase C delta.

It is well established that activation of protein kinase C (PKC) by phorbol esters promotes apoptosis in androgen-dependent prostate cancer cells. However, there is limited information regarding the cellular mechanisms involved in this effect. In this report we identified a novel autocrine pro-apoptotic loop triggered by PKCdelta activation in prostate cancer cells that is mediated by death receptor ligands. The apoptotic effect of phorbol 12-myristate 13-acetate in LNCaP cells was impaired by inhibition or depletion of tumor necrosis factor alpha-converting enzyme, the enzyme responsible for tumor necrosis factor alpha (TNFalpha) shedding. Moreover, the apoptogenic effect of conditioned medium collected after phorbol 12-myristate 13-acetate treatment could be inhibited by blocking antibodies against TNFalpha and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), but not FasL, as well as by RNA interference depletion of TNFalpha and TRAIL receptors. Moreover, depletion or inhibition of death receptor downstream effectors, including caspase-8, FADD, p38 MAPK, and JNK, significantly reduced the apoptogenic effect of the conditioned medium. PKCdelta played a major role in this autocrine loop, both in the secretion of autocrine factors as well as a downstream effector. Taken together, our results demonstrate that activation of PKCdelta in prostate cancer cells causes apoptosis via the release of death receptor ligands and the activation of the extrinsic apoptotic cascade.

Tyrosine kinase c-Src constitutes a bridge between cystic fibrosis transmembrane regulator channel failure and MUC1 overexpression in cystic fibrosis.

Cystic fibrosis (CF), a disease caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) chloride channel, is associated in the respiratory system with the accumulation of mucus and impaired lung function. The role of the CFTR channel in the regulation of the intracellular pathways that determine the overexpression of mucin genes is unknown. Using differential display, we have observed the differential expression of several mRNAs that may correspond to putative CFTR-dependent genes. One of these mRNAs was further characterized, and it corresponds to the tyrosine kinase c-Src. Additional results suggest that c-Src is a central element in the pathway connecting the CFTR channel with MUC1 overexpression and that the overexpression of mucins is a primary response to CFTR malfunction in cystic fibrosis, which occurs even in the absence of bacterial infection.