Clusterin and IGFBPs as antisense targets in prostate cancer

The primary hurdle to improved survival of advanced prostate cancer is our failure to prevent or treat the tumor's progression to its lethal and untreatable stage of androgen independence. Novel treatment modalities designed to prevent androgen-independent progression including prostate cancer metastasis are required. Accelerated identification and characterization of cancer-relevant molecular targets has sparked considerable interest in the development of new generations of anticancer agents that specifically inhibit a progression-relevant target. Antisense oligonucleotides, short synthetic stretches of chemically modified DNA capable of specifically hybridizing to the mRNA of a chosen cancer-relevant target gene, promise to show enhanced specificity for malignant cells with a favorable side-effect profile due to well-defined and tailored modes of action. Although not all of the challenges have been met to date, emerging clinical evidence supports the premise that antisense oligonucleotides stand a realistic chance of emerging as major partners of rationally designed anticancer regimens. The rationale and status of antisense targeting of the treatment resistance factor clusterin and of insulin-like growth factor binding protein (IGFBP) 2 and 5 are discussed.

An endogenous retrovirus derived from human melanoma cells

We show that human melanoma cells produce retrovirus-like particles that exhibit reverse transcriptase activity, package sequences homologous to human endogenous retrovirus K (HERV-K), and contain mature forms of the Gag and Env proteins. We also demonstrate expression of the pol gene and of Gag, Env, and Rec proteins in human melanomas and metastases but not in melanocytes or normal lymph nodes. The data suggest that expression of retroviral genes and production of retroviral particles is activated during development of melanoma.

Bcl-x(L) antisense oligonucleotides radiosensitise colon cancer cells

Advanced colon cancer is a malignancy with poor response to various treatment modalities including ionising radiation (IR) and chemotherapy. Both IR and chemotherapeutic agents have been shown to act by inducing apoptosis, a type of cell death antagonised by the Bcl-x_L gene product. Since approximately 60% of human colon cancers express Bcl-x_L, it was the aim of this study to explore the potential of Bcl-x_L antisense oligonucleotides as a novel radiosensitisation strategy. Caco-2 colon cancer cells were treated with Bcl-x_L antisense oligonucleotides in combination with IR or cisplatin, and Bcl-x_L protein expression, apoptosis, cell viability and clonogenic survival were examined. Bcl-x_L antisense oligonucleotide specifically reduced the Bcl-x_L protein level by almost 50% in Caco-2 cells. The decreased threshold for the induction of apoptosis resulted in a 300% increase of apoptosis after IR or cisplatin treatment and led to a 60% reduction of cell proliferation beyond response rates achieved with IR. These data suggest that Bcl-x_L is an important factor contributing to the treatment resistance of human colon cancer. Specific reduction of Bcl-x_L protein levels by antisense oligonucleotides qualifies as a promising therapeutic strategy for colon cancer that may help overcome resistance and improve clinical outcome in this malignancy.

Small Interfering RNA Targeting Bcl-2 Sensitizes Malignant Melanoma

Malignant melanoma is a prime example of a treatment-resistant tumor with poor prognosis. Even with innovative treatment regimens, response rates remain low, and the duration of responses is short. More than 90% of all melanomas express the antiapoptotic protein Bcl-2, shown to contribute to a chemoresistant phenotype in melanoma. We previously demonstrated that antisense-mediated inhibition of Bcl-2 sensitizes malignant melanoma to apoptosis-inducing treatment modalities. In the present study, we evaluated synthetic small interfering RNA (siRNA) compounds targeting Bcl-2 as a novel approach to downregulate Bcl-2 expression in melanoma cells. siRNA treatment led up to a 19-fold reduction of bcl-2 mRNA levels and only barely detectable Bcl-2 protein expression at low nanomolar concentrations. Silencing of Bcl-2 in melanoma cells by specific siRNA led to a moderate increase in apoptotic cell death and inhibition of cell growth. However, if siRNA compounds targeting Bcl-2 were combined with the apoptosis-inducing chemotherapeutic agent cisplatin, a massive increase in apoptotic cell death compared with controls was observed. Notably, the combination of Bcl2 siRNA and low-dose cisplatin resulted in a supra-additive effect, with nearly complete suppression of cell growth, whereas cell growth in cisplatin-only-treated cells was only moderately affected (96% vs. 25%, p < 0.001). These findings underline a key role for Bcl-2 in conferring chemoresistance to melanoma and highlight Bcl-2 siRNA strategies as novel and highly effective tools, with the potential for future targeted therapy of malignant melanoma.

Effect of glutathione depletion and hydrophilic bile acids on hepatic acute phase reaction in rats with extrahepatic cholestasis

BACKGROUND

Extrahepatic cholestasis by biliary obstruction induces an acute phase reaction in the liver. It is a complex process involving cytokines, hormones and growth factors. To determine whether the regulation of acute phase proteins (APP) in cholestasis depends on glutathione (GSH), the effect of buthionine sulfoximine-induced (BSO-induced) GSH depletion on the expression of various APP was studied. In addition, we determined the influence of hepatoprotective bile acids on hepatic APP and underlying cytokine events.

METHODS

Liver samples of bile-duct-ligated or sham-operated rats were examined. mRNA expression was quantified by densitometric analysis of Northern blots.

RESULTS

Expression of APP increased 2-5-fold in bile-duct-ligated rats as compared to sham-operated controls. This acute phase reaction remained similar independently of whether cholestasis occurred for 5 days or 3 weeks. In contrast to alpha2-macroglobulin and tissue inhibitor of metalloproteinases-1 (TIMP-1), mRNA levels of both beta-fibrinogen and haptoglobin were significantly up-regulated after GSH depletion by BSO in cholestasis. Feeding of ursodeoxycholic and iso-ursodeoxycholic acid markedly down-regulated alpha2-macroglobulin and TIMP-1 expression in cholestasis but did not affect overexpression of beta-fibrinogen and haptoglobin. Cholestasis leads to an increased APP expression accompanied by an increased expression of inflammatory cytokines (IL-6, TNF-alpha). After feeding of hydrophilic bile acids, increases in inflammatory cytokines were abrogated.

CONCLUSIONS

We show that GSH is involved in the acute phase reaction during obstructive cholestasis. In addition, bile acids might selectively ameliorate the acute phase response by reducing expression of the APP not affected by GSH depletion (alpha2-macroglobulin and TIMP-1).

Efficacy of NaOCl/H2O2 irrigation and GaAlAs laser in decontamination of root canals in vitro

BACKGROUND AND OBJECTIVES

To investigate the bactericidal effect of an 809 nm semiconductor laser alone, and in combination with NaOCl/H(2)O(2) irrigation in root canals in vitro.

STUDY DESIGN/MATERIALS AND METHODS

A total of 72 human single-rooted teeth extracted for periodontal reasons were included. The crowns were removed, the roots shortened to a length of 12 mm, and the canals enlarged up to an apical size of #50 file. The specimens were autoclaved and incubated with a suspension of Streptococcus sanguinis (ATCC 10556). Laser irradiation was performed on a PC-controlled XY translation stage. A 200 micron optic fiber was used. Twelve specimens were irradiated at a power output of 1.5, 3.0, and 4.5 W in the cw-mode. The total irradiation time was 60 seconds per canal. Twelve specimens were rinsed with NaOCl and H(2)O(2) only, 12 were rinsed and laser treated, and 12 served as untreated controls. After laser treatment, the specimens were sonicated and the bacterial growth was examined by counting colony forming units on blood agar plates. Temperature changes at the outer root surface during irradiation were registered by means of thermocouples. Treated and control specimens were investigated by means of scanning electron microscopy.

RESULTS

Mean bacterial reductions of 0.35 log steps at a power output of 1.5 W, 1.44 at 3.0 W, and 2.84 at 4.5 W were calculated. Bacterial reduction by the NaOCl/H(2)O(2) solution alone was 1.48 and comparable to that achieved by irradiation at 3.0 W. With a log kill 2.85, the combination of rinsing and laser irradiation at 3.0 W resulted in a further significant bacterial reduction as compared to rinsing alone (P = 0.004). Irradiation did not result in excessive heat generation at the root surface. Carbonization of the root canal wall was observed in single teeth at 3.0 and 4.5 W and no controlled sealing of the dentinal tubules could be achieved in the root canal.

CONCLUSIONS

The application of the diode laser might be an adjunct to conventional endodontic treatment when used in combination with a NaOCl/H(2)O(2) solution.

Mcl-1 antisense therapy chemosensitizes human melanoma in a SCID mouse xenotransplantation model

It is well established that high expression of the antiapoptotic Bcl-2 family proteins Bcl-2 and Bcl-xL can significantly contribute to chemoresistance in a number of human malignancies. Much less is known about the role the more recently described Bcl-2 family member Mcl-1 might play in tumor biology and resistance to chemotherapy. Using an antisense strategy, we here address this issue in melanoma, a paradigm of a treatment-resistant malignancy. After in vitro proof of principle supporting an antisense mechanism of action with specific reduction of Mcl-1 protein as a consequence of nuclear uptake of the Mcl-1 antisense oligonucleotides employed, antisense and universal control oligonucleotides were administered systemically in combination with dacarbazine in a human melanoma SCID mouse xenotransplantation model. Dacarbazine, available now for more than three decades, still remains the most active single agent for treatment of advanced melanoma. Mcl-1 antisense oligonucleotides specifically reduced target protein expression as well as the apoptotic threshold of melanoma xenotransplants. Combined Mcl-1 antisense oligonucleotide plus dacarbazine treatment resulted in enhanced tumor cell apoptosis and led to a significantly reduced mean tumor weight (mean 0.16 g, 95% confidence interval 0.08-0.26) compared to the tumor weight in universal control oligonucleotide plus dacarbazine treated animals (mean 0.35 g, 95% confidence interval 0.2-0.44) or saline plus dacarbazine treated animals (mean 0.39 g, 95% confidence interval 0.25-0.53). We thus show that Mcl-1 is an important factor contributing to the chemoresistance of human melanoma in vivo. Antisense therapy against the Mcl-1 gene product, possibly in combination with antisense strategies targeting other antiapoptotic Bcl-2 family members, appears to be a rational and promising approach to help overcome treatment resistance of malignant melanoma.

Antisense therapy: current status in prostate cancer and other malignancies

Recent technological advances now allowing both large scale data generation and its in-depth analysis have opened new avenues to identify and target genes involved in neoplastic transformation and tumor progression. This accelerated identification and characterization of cancer-relevant molecular targets has sparked considerable interest in the development of new generations of anti-cancer agents. It is anticipated, that these agents will show enhanced specificity for malignant cells and a more favorable side-effect profile due to well-defined and tailored modes of action. Antisense oligonucleotides (ASOs) are short synthetic stretches of chemically modified DNA capable of specifically hybridizing to the mRNA of a chosen cancer-relevant target gene are close, after decades of challenges, close to fulfilling their promise in the clinical setting. Emerging clinical evidence supports the notion that ASOs stand a realistic chance of developing into one of the main players of rationally designed anti-cancer agents, although certainly not all of the challenges have been met to date. The status of antisense targeting of genes relevant to prostate cancer, including bcl-2, bcl-xL, clusterin, androgen receptor (AR) and IGFBPs, are reviewed.

Equine melanoma in a population of 296 grey Lipizzaner horses

REASONS FOR PERFORMING STUDY

Equine melanomas occur most commonly in grey horses at age 5 years or more. Generally, benign and malignant melanomas are distinguished by microscopy, but a more distinct classification would be helpful.

OBJECTIVES

The objectives of this study were to gain further evidence concerning the occurrence of melanotic tumours, and to evaluate the impact of heredity on melanoma development.

METHODS

A clinical study was conducted on a defined population of 296 grey horses of Lipizzaner breed. Individuals were classified according to their stage of disease using a 0-5 scale. Heritability was estimated on a sample of 296 grey horses with pedigrees traced back as far as 32 generations.

RESULTS

Of the 296 horses, dermal melanomas were present in 148 horses (50%), 68 of which were more than age 15 years; 51 of these were melanoma-bearing. In 75.6% of cases, melanotic tumours were detected underneath the tail. Although melanoma-bearing grey horses were encountered up to stage 4, none of the affected individuals suffered any severe clinical effect or was handicapped in performance. Statistical analysis revealed highly significant effects of stud and age (P < 0.0001), explaining 28% of the total variability.

CONCLUSIONS

In contrast to melanomas in solid-coloured horses characterised by early metastases, melanomas in grey horses showed less malignancy. Affected individuals often had encapsulated nodules or structures similar to human blue nevi. Grey horse-specific genetic factors inhibiting metastatic processes may be responsible for this phenomenon.

POTENTIAL CLINICAL RELEVANCE

Although the obtained heritability estimate of 0.36 with a standard error of 0.11 indicates a strong genetic impact on the development of melanoma in ageing grey horses, a possible influence of the genes with large effects was also suggested. Therefore, further analysis is required of melanoma development in the ageing grey horse.

Rifampin-impregnated silicone catheters: a potential tool for prevention and treatment of CSF shunt infections

BACKGROUND

Infection continues to be one of the major complications of cerebro-spinal fluid shunting procedures. Recent insights in the pathophysiological mechanism of these foreign body infections have elucidated the difficulty of achieving successful treatment without device removal. The development of a rifampin-impregnated silicone catheter yielded excellent results in infection prevention and treatment in vitro as well as in an animal model.

PATIENTS AND METHODS

Here, we describe the application of this device in two patients with a complicated course of shunt infection.

RESULTS

In one patient the rifampin-impregnated shunt system was implanted after external drainage to prevent further infection. The shunt infection of the second patient was treated by replacement of the infected shunt system with a rifampin-impregnated device. Both patients recovered immediately without any signs of adverse effects and the two shunt systems have now been working properly for more than 36 and 21 months, respectively.

CONCLUSION

These results suggest that rifampin-impregnated silicone catheters could become a valuable tool in the treatment and prevention of shunt infections.

Farnesyl thiosalicylic acid chemosensitizes human melanoma in vivo

Malignant melanoma is well known for its poor response to a variety of chemotherapeutic agents. Testing of numerous treatment strategies has identified dacarbazine as the most active single drug; however, its response rates in various clinical settings are quite limited. Defective apoptosis in combination with oncogenic proteins (such as activated Ras) in cell proliferation pathways plays a key part in both the development and disease progression of human melanoma. Farnesyl thiosalicylic acid, a novel Ras inhibitor, dislodges Ras proteins from the cell membrane, leading to inhibition of cell transformation and tumor growth. In this study we evaluated the effect of farnesyl thiosalicylic acid treatment on established human melanoma xenografts grown in mice with severe combined immunodeficiency as well as the chemosensitizing effect of farnesyl thiosalicylic acid in combination with dacarbazine. Daily administration of 10, 20, or 40 mg per kg of farnesyl thiosalicylic acid resulted in a concentration-dependent reduction in tumor growth, with growth inhibition reaching a mean value of 45+/-7%, at the highest concentration. The combination of farnesyl thiosalicylic acid (10 mg per kg per day) and dacarbazine (80 mg per kg per day) resulted in a significant reduction of 56%+/-9%, in mean tumor growth. Analysis of toxicologic parameters (mouse weight, blood cell counts, and blood chemistry) showed an acceptable and similar toxicity profile for both the single-agent farnesyl thiosalicylic acid treatment and the combination of farnesyl thiosalicylic acid plus dacarbazine treatment. Given the observed preclinical treatment responses and the low toxicity, our results support the notion that farnesyl thiosalicylic acid in combination with dacarbazine may qualify as a rational treatment approach for human melanoma.

Antitumor effect of G3139 Bcl-2 antisense oligonucleotide is independent of its immune stimulation by CpG motifs in SCID mice

The Bcl-2 antisense oligonucleotide (AS-ODN) G3139 chemosensitizes human malignancies by downregulating the antiapoptotic protein Bcl-2. Because G3139 contains two potential immunostimulatory CpG motifs, we asked if immune stimulation contributes to the antitumor activity observed previously. 5'-Methylation of cytosines in CpG motifs abrogates immune stimulation by oligonucleotides. We, therefore, studied the antitumor and immunostimulatory potential of G3139 vs. an identical oligonucleotide, except for methylation of cytosines in the two CpG motifs (G4232). In a human melanoma SCID mouse xenotransplantation model, G3139 or G4232 was administered by continuous subcutaneous (s.c.) or bolus intraperitoneal (i.p.) infusion. Both G3139 and G4232 significantly reduced tumor growth by about one third relative to the saline-treated group. Furthermore, we noted a similar downregulation of Bcl-2 expression and increase in tumor cell apoptosis caused by G3139 and G4232 compared with saline controls. However, mice treated with G3139 had a pronounced increase in spleen weight and interleukin-12 (IL-12) plasma levels relative to mice treated with either G4232 or saline. Splenomegaly and elevated IL-12 plasma levels suggest that G3139 can be immunostimulatory. However, there is clear evidence that the antitumor effect of G3139 in this model appears to be a Bcl-2 antisense effect that is independent of immune stimulation, as G3139 and its immune-silent counterpart G4232 caused similar tumor suppression and apoptosis induction.

Betulinic acid-induced Mcl-1 expression in human melanoma--mode of action and functional significance

BACKGROUND

Currently there is no information on the regulation of expression and physiological role of the anti-apoptotic protein Mcl-1 in cells of the melanocytic lineage. This study investigates the regulation and expression of Mcl-1 in human melanoma cells, which was recently found to be induced by betulinic acid, a compound with anti-melanoma and apoptosis-inducing potential.

MATERIALS AND METHODS

Mcl-1 phosphorthioate antisense oligonucleotides were used to investigate the effect of downregulating the expression of Mcl-1. Regulation of Mcl-1 expression was analyzed with the specific PI3-kinase inhibitors LY294002 and wortmannin and the inhibitor of MAP-kinase activation, PD98059. Western blot analysis was performed with anti ERK1/2, Mcl-1, Bak, Bcl-x and Bax antibodies. Activation status of PI-3 kinase and MAP-kinase pathways was investigated using phospho-Akt and phosphorylation-state independent Akt as well as phospho-MAP kinase, phospho-MEK and phospho-GSK-3alpha/beta antibodies.

RESULTS

Upregulation of Mcl-1 in human melanoma cells by betulinic acid is mediated via a signal-transduction pathway that is inhibited by LY294002 and wortmannin. Betulinic acid-induced phosphorylation and activation of the Akt protein kinase was inhibited by LY294002. The inhibitor PD98059 reduced expression levels of Mcl-1 in melanoma cells and this effect was counteracted by betulinic acid. Downregulation of Mcl-1 by antisense oligodeoxynucleotides in combination with betulinic treatment led to a synergistic effect regarding growth inhibition.

CONCLUSIONS

These results suggest that in human melanoma cells Mcl-1 is (i) of functional relevance for survival and (ii) subject to dual regulation by the MAP- kinase pathway and a pathway involving protein kinase B/Akt, the latter of which is modulated in response to betulinic acid. This study provides an experimental foundation for future therapeutic strategies using anti-Mcl-1 antisense oligonucleotides in human melanoma.

Specific systemic nonviral gene delivery to human hepatocellular carcinoma xenografts in SCID mice

Systemic tumor-targeted gene delivery is attracting increasing attention as a promising alternative to conventional therapeutical strategies. To be considered as a viable option, however, the respective transgene has to be administered with high tumor specificity. Here, we describe novel polyethylenimine (PEI)-based DNA complexes, shielded by covalent attachment of polyethylene glycol (PEG), that make use of epidermal growth factor (EGF) as a ligand for targeting gene delivery to EGF receptor-expressing human hepatocellular carcinoma (HCC) cells. In vitro transfection of luciferase reporter DNA resulted in high levels of gene expression in the human HCC cell lines Huh-7 and HepG2. An excess of free EGF during transfection clearly reduced expression levels, indicating a specific EGF receptor-mediated uptake of the DNA particles. Following intravenous injection into human HCC xenograft-bearing SCID mice, luciferase expression was predominantly found in the tumor, with levels up to 2 logs higher than in the liver, which was the highest expressing major organ. Histologic investigation showed reporter gene expression (beta-galactosidase) localized to tumor cells. Assessing DNA distribution within the tumor by immunofluorescence microscopy, rhodamine-labelled transgene DNA was found to be mainly associated with HCC cells. In the liver, DNA was taken up almost exclusively by Kupffer cells and, as indicated by the low expression, subsequently degraded. In conclusion, we have shown that intravenous injection of PEGylated EGF-containing DNA/PEI complexes allows for highly specific expression of a transgene in human HCC tumors.

Antisense therapy for cancer--the time of truth

The recent acceleration in the identification and characterisation of new molecular targets for cancer and the limited effectiveness of conventional treatment strategies has focused considerable interest on the development of new types of anticancer agents. These new drugs are hoped to be highly specific for malignant cells with a favorable side-effect profile due to well-defined mechanisms of action. Antisense oligonucleotides are one such class of new agent--they are short, synthetic stretches of DNA which hybridise with specific mRNA strands that correspond to target genes. By binding to the mRNA, the antisense oligonucleotides prevent the sequence of the target gene being converted into a protein, thereby blocking the action of the gene. Several genes known to be important in the regulation of apoptosis, cell growth, metastasis, and angiogenesis, have been validated as molecular targets for antisense therapy. Furthermore, new targets are rapidly being uncovered through coordinated functional genomics and proteomics initiatives. Phosphorothioate oligonucleotides are the current gold standard for antisense therapy; they have acceptable physical and chemical properties and show reasonable resistance to nucleases. Recently, new generations of these phosphorothioate oligonucleotides that contain 2'-modified nucleoside building blocks to enhance RNA binding affinity and decrease indirect toxic effects have been developed. Antisense therapeutics are, after decades of difficulties, finally close to fulfilling their promise in the clinic.

Effect of blackcurrant-, cranberry- and plum juice consumption on risk factors associated with kidney stone formation

OBJECTIVE

To evaluate the influence of plum-, cranberry- and blackcurrant juice on urinary stone risk factors.

DESIGN

Investigations were carried out in 12 healthy male subjects aged 18-38 y. All subjects received a standardized diet formulated according to the dietary recommendations of the German Society of Nutrition. The subjects provided 24 h urine collections in a control, three loading phases. In each loading phase a neutral mineral water was substituted for 330 ml of the particular juice.

RESULTS

Cranberry juice decreased the urinary pH, whereas the excretion of oxalic acid and the relative supersaturation for uric acid were increased. Blackcurrant juice increased the urinary pH and the excretion of citric acid. The excretion of oxalic acid was increased too. All changes were statistically significant. The plum juice had no significant effect on the urinary composition.

CONCLUSION

It is concluded that blackcurrant juice could support the treatment and metaphylaxis of uric acid stone disease because of its alkalizing effect. Since cranberry juice acidifies urine it could be useful in the treatment of brushite and struvite stones as well as urinary tract infection.

SPONSORSHIP

Funded by our own Division respectively the University.

Bcl-xL antisense oligonucleotides chemosensitize human glioblastoma cells

BACKGROUND

Resistance to chemotherapy in glioblastoma has been linked to the expression of antiapoptotic Bcl-2 family members including Bcl-xL.

METHODS

Bcl-xL expression was specifically reduced in M059K glioblastoma cells with antisense oligonucleotides (ISIS 16009, ISIS 16967) as assessed by Western blotting. Induction of apoptosis by treatment with antisense oligonucleotides in combination with paclitaxel in cell culture was monitored by WST-1 assays and flow cytometric analysis.

RESULTS

Antisense oligonucleotide-mediated reduction of Bcl-xL levels led to enhanced cytotoxicity in M059K cells when compared to the use of a mismatch control oligonucleotide (p < 0.001). A decreased threshold for the induction of apoptosis led to significantly enhanced cytotoxic responses to paclitaxel treatment in WST-1 assays (p < 0.001) and flow cytometric analyses.

CONCLUSION

Combination treatment using Bcl-xL antisense oligonucleotides and paclitaxel may qualify as a promising strategy to ultimately improve the clinical outcome of glioblastoma.

Protein kinase C isoforms in normal and transformed cells of the melanocytic lineage

Enzymes belonging to the protein kinase C (PKC) family represent one of the major mediators of signal transduction in melanocytes. To identify PKC isoforms that may be associated with the process of malignant transformation and metastasis, we investigated the expression pattern of 11 different PKC isoforms (alpha, beta I, beta II, gamma, delta, epsilon, eta, theta, zeta, lambda, and iota) in melanoma lymph node metastases, in cell lines established from these metastases, in primary cell cultures from normal melanocytes, and in permanent cell lines established from spontaneously transformed melanocytes. PKC alpha, beta I, beta II, delta, epsilon, eta, zeta, lambda and iota were found to be expressed in total lysates from melanoma metastases. In permanent cell lines established from these metastases, the expression levels of PKC beta I, beta II, delta, epsilon, and eta were lower or undetectable when compared with initial expression in tumour lysates. In normal primary melanocyte cultures, the PKC isoforms beta II, delta, epsilon, eta and iota were undetectable. PKC gamma and theta isoforms were undetectable in all melanocytic cell types examined. PKC iota was the only isoform exclusively detected in tumour lysates, in spontaneously transformed melanoma cells and melanoma cell lines, but not in normal melanocytes, and may therefore be associated with the transformed phenotype in human melanoma in vitro and in vivo.

Bcl-X(L) is a chemoresistance factor in human melanoma cells that can be inhibited by antisense therapy

Malignant melanoma is a tumor that responds poorly to a variety of apoptosis-inducing treatment modalities, such as chemotherapy. The expression of genes that regulate apoptotic cell death plays an important role in determining the sensitivity of tumor cells to chemotherapeutic intervention. Bcl-x(L) is an antiapoptotic member of the Bcl-2 family and is universally expressed in human melanoma. To evaluate the Bcl-x(L) protein as a potential therapeutic target in melanoma, the influence of Bcl-x(L) expression levels on the chemoresistance of human melanoma cells was investigated. Overexpression of Bcl-x(L) in stably transfected human melanoma Mel Juso cells significantly reduced sensitivity to cisplatin-induced apoptosis (p < or = 0.05). In a parallel approach, reduction of Bcl-x(L) protein by specific AS oligonucleotide (ISIS 16009) treatment enhanced the chemosensitivity of Mel Juso cells by 62% compared to cells treated with MM control oligonucleotide (ISIS 16967) as well as chemotherapy-induced apoptosis. These data suggest that Bcl-x(L) is an important factor contributing to the chemoresistance of human melanoma. Reduction of Bcl-x(L) expression by AS oligonucleotides provides a rational and promising approach that may help to overcome chemoresistance in this malignancy.

The melanocyte-specific isoform of the microphthalmia transcription factor affects the phenotype of human melanoma

The microphthalmia transcription factor MITF plays a pivotal role in the development and differentiation of melanocytes. The purpose of this work was to investigate the expression and function of the melanocyte-specific isoform MITF-M in human melanoma. We found that MITF-M is repressed in 8 of 14 established melanoma cell lines tested. Transfection of MITF-M into a melanoma cell line (518A2) lacking the M-isoform and into a permanent cell line established from normal melanocytes (NMel-II) resulted in slower tumor growth in a severe combined immunodeficient-mouse xenotransplantation model. The growth difference between vector control-transfected tumors derived from the NMel-II cell line (mean tumor weight +/- SD, 3.2 g +/- 1.13) and MITF-M (+) transfectants (mean tumor weight +/- SD, 1.1 g +/- 0.49) was significant (P = 0.018). The mean tumor weight of control-transfected 518A2 tumors was 0.99 g +/- 0.22 and of MITF-M (+) transfectants, 0.69 g +/- 0.32. The difference in growth between 518A2 controls and the MITF-M (+) transfectants was clear, however it did not reach statistical significance (P = 0.08). In addition to the growth-inhibitory effects, MITF-M expression led to a change in the histopathological appearance of tumors from epitheloid toward a spindle-cell type in vivo. These results indicate a role for the MITF-M isoform in the in vivo growth control and the phenotype of human melanoma. In conclusion, MITF-M may qualify as a marker capable of identifying subgroups of melanoma patients with different tumor biology and prognosis.

Hepatocytes convert to a fibroblastoid phenotype through the cooperation of TGF-β1 and Ha-Ras: steps towards invasiveness

In hepatocarcinogenesis, it is an open question whether transforming growth factor (TGF)-β1 provides a tumor-suppressive or a tumor-promoting role. To address this question, we employed immortalized murine hepatocytes, which display a high degree of differentiation and, expectedly, arrest in the G1 phase under exposure to TGF-β1. These hepatocytes maintain epithelial polarization upon expression of oncogenic Ha-Ras. However, Ras-transformed hepatocytes rapidly convert to a spindle-shaped, fibroblastoid morphology upon treatment with TGF-β1, which no longer inhibits proliferation. This epithelial to fibroblastoid conversion (EFC) is accompanied by disruption of intercellular contacts and remodeling of the cytoskeletal framework. Fibroblastoid derivatives form elongated branching cords in collagen gels and grow to severely vascularized tumors in vivo, indicating their increased malignancy and even invasive phenotype. Additionally, fibroblastoid cells secrete strongly enhanced levels of TGF-β1, suggesting an autocrine regulation of TGF-β signaling. Expression profiling further revealed that the loss of the adhesion component E-cadherin correlates with the upregulation of its transcriptional repressor Snail in fibroblastoid cells. Moreover, the phosphoinositide 3-OH (PI3) kinase pathway was required for the maintenance of EFC, as inhibition of PI3 kinase reverted fibroblastoid cells to an epithelial-like phenotype. Taken together, these data indicate a dual role of TGF-β1 in hepatocytes: it induces proliferation arrest but provides a crucial function in promoting late malignant events in collaboration with activated Ha-Ras.

The Ras inhibitor S-trans,trans-farnesylthiosalicylic acid chemosensitizes human tumor cells without causing resistance

Ras transformation requires Ras membrane anchorage, which is promoted by a farnesylcysteine carboxymethyl ester and by additional sequences specific to each Ras isoform. We showed previously that S-trans,trans-farnesylthiosalicylic acid (FTS) disrupts Ras membrane anchorage and that this disturbance contributes to inhibition of cell transformation and tumor growth. Most tumor cells develop resistance to anticancer agents. Here we examined whether tumor cells develop resistance to FTS and evaluated the therapeutic potential of FTS combined with cytotoxic drugs, because oncogenic Ras promotes antiapoptotic signals in tumors of epithelial origin. We showed that Panc-1 pancreatic cancer cells, SW480 colon cancer cells, and H-ras (EJ)-transformed Rat-1 fibroblasts exposed to FTS for prolonged periods (>6 months) do not escape FTS-induced growth inhibition and do not develop drug resistance. These cells continued to express reduced amounts of Ras, exhibit a reversed phenotype, and show an altered response to the cytotoxic drugs doxorubicin and gemcitabine. FTS-treated Panc-1 or SW480 cells acquired sensitivity to the cytotoxic drugs, whereas FTS-treated EJ cells lost sensitivity to doxorubicin, reflecting the opposite effects of oncogenic Ras on the survival of epithelial cells and fibroblasts. Treatment with FTS led to a marked increase in sensitivity to gemcitabine of the formerly resistant SW480 cells and a 100-fold increase in sensitivity to gemcitabine of Panc-1 cells. Such treatment in mice with preexisting Panc-1 tumors provided a synergistic effect of FTS and gemcitabine, leading to enhanced inhibition of tumor growth and a 65% increase in survival rate.

Adrenoceptor hyporeactivity is responsible for Escherichia coli endotoxin-induced acute vascular dysfunction in humans

Impaired response to catecholamines contributes to the altered hemodynamics in sepsis, which has been attributed to excessive NO formation. We have studied the systemic hemodynamic and local forearm responses and inducible NO synthase (iNOS) expression during experimental endotoxemia in humans. Escherichia coli endotoxin (lipopolysaccharide [LPS]) was administered at doses of 1 or 2 ng/kg to healthy volunteers. In 10 subjects, the systemic pressor effect of phenylephrine was assessed before and after the administration of LPS. In 9 further subjects, forearm blood flow responses to intra-arterial noradrenaline, acetylcholine, glyceryl trinitrate, and N(G)-monomethyl-L-arginine (L-NMMA) were studied at baseline and after LPS administration. Peripheral blood was collected and analyzed for iNOS mRNA and protein. Four hours after LPS, the response of systolic blood pressure (P<0.0005) and heart rate (P<0.05) to phenylephrine was significantly reduced. In the forearm, noradrenaline-induced vasoconstriction was also reduced by approximately 50% (P<0.01), but L-NMMA responsiveness was unchanged. iNOS mRNA or protein was not increased. Marked vascular adrenoceptor hyporeactivity is detectable in the absence of increased NO activity or iNOS expression in endotoxemia, arguing against major involvement of vascular iNOS activity in the acute systemic vasodilation to LPS.