Outcomes with durvalumab after chemoradiotherapy in stage IIIA-N2 non-small-cell lung cancer: an exploratory analysis from the PACIFIC trial

Background

The phase III PACIFIC trial (NCT02125461) established consolidation durvalumab as standard of care for patients with unresectable, stage III non-small-cell lung cancer (NSCLC) and no disease progression following chemoradiotherapy (CRT). In some cases, patients with stage IIIA-N2 NSCLC are considered operable, but the relative benefit of surgery is unclear. We report a post hoc, exploratory analysis of clinical outcomes in the PACIFIC trial, in patients with or without stage IIIA-N2 NSCLC.

Materials and methods

Patients with unresectable, stage III NSCLC and no disease progression after ≥2 cycles of platinum-based, concurrent CRT were randomized 2 : 1 to receive durvalumab (10 mg/kg intravenously; once every 2 weeks for up to 12 months) or placebo, 1-42 days after CRT. The primary endpoints were progression-free survival (PFS; assessed by blinded independent central review according to RECIST version 1.1) and overall survival (OS). Treatment effects within subgroups were estimated by hazard ratios (HRs) from unstratified Cox proportional hazards models.

Results

Of 713 randomized patients, 287 (40%) had stage IIIA-N2 disease. Baseline characteristics were similar between patients with and without stage IIIA-N2 NSCLC. With a median follow-up of 14.5 months (range: 0.2-29.9 months), PFS was improved with durvalumab versus placebo in both patients with [HR = 0.46; 95% confidence interval (CI), 0.33-0.65] and without (HR = 0.62; 95% CI 0.48-0.80) stage IIIA-N2 disease. Similarly, with a median follow-up of 25.2 months (range: 0.2-43.1 months), OS was improved with durvalumab versus placebo in patients with (HR = 0.56; 95% CI 0.39-0.79) or without (HR = 0.78; 95% CI 0.57-1.06) stage IIIA-N2 disease. Durvalumab had a manageable safety profile irrespective of stage IIIA-N2 status.

Conclusions

Consistent with the intent-to-treat population, treatment benefits with durvalumab were confirmed in patients with stage IIIA-N2, unresectable NSCLC. Prospective studies are needed to determine the optimal treatment approach for patients who are deemed operable.

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The PACIFIC trial established durvalumab after CRT as standard of care for unresectable, stage III NSCLC.

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The optimum multimodal treatment strategy for patients with potentially resectable, stage IIIA-N2 NSCLC is unknown.

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Survival benefit with durvalumab was observed in patients with stage IIIA-N2, unresectable NSCLC in this post hoc analysis.

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Durvalumab after CRT also exhibited a manageable safety profile in this subpopulation from PACIFIC.

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Studies of surgical vs. non-surgical strategies are needed to establish the best approach for potentially operable patients.

Outcomes with durvalumab by tumour PD-L1 expression in unresectable, stage III non-small-cell lung cancer in the PACIFIC trial

BACKGROUND

In the PACIFIC trial, durvalumab significantly improved progression-free and overall survival (PFS/OS) versus placebo, with manageable safety, in unresectable, stage III non-small-cell lung cancer (NSCLC) patients without progression after chemoradiotherapy (CRT). We report exploratory analyses of outcomes by tumour cell (TC) programmed death-ligand 1 (PD-L1) expression.

PATIENTS AND METHODS

Patients were randomly assigned (2:1) to intravenous durvalumab 10 mg/kg every 2 weeks or placebo ≤12 months, stratified by age, sex, and smoking history, but not PD-L1 status. Where available, pre-CRT samples were tested for PD-L1 expression (immunohistochemistry) and scored at pre-specified (25%) and post hoc (1%) TC cut-offs. Treatment-effect hazard ratios (HRs) were estimated from unstratified Cox proportional hazards models (Kaplan-Meier-estimated medians).

RESULTS

In total, 713 patients were randomly assigned, 709 of whom received at least 1 dose of study treatment durvalumab (n = 473) or placebo (n = 236). Some 451 (63%) were PD-L1-assessable: 35%, 65%, 67%, 33%, and 32% had TC ≥25%, <25%, ≥1%, <1%, and 1%-24%, respectively. As of 31 January 2019, median follow-up was 33.3 months. Durvalumab improved PFS versus placebo (primary-analysis data cut-off, 13 February 2017) across all subgroups [HR, 95% confidence interval (CI); medians]: TC ≥25% (0.41, 0.26-0.65; 17.8 versus 3.7 months), <25% (0.59, 0.43-0.82; 16.9 versus 6.9 months), ≥1% (0.46, 0.33-0.64; 17.8 versus 5.6 months), <1% (0.73, 0.48-1.11; 10.7 versus 5.6 months), 1%-24% [0.49, 0.30-0.80; not reached (NR) versus 9.0 months], and unknown (0.59, 0.42-0.83; 14.0 versus 6.4 months). Durvalumab improved OS across most subgroups (31 January 2019 data cut-off; HR, 95% CI; medians): TC ≥ 25% (0.50, 0.30-0.83; NR versus 21.1 months), <25% (0.89, 0.63-1.25; 39.7 versus 37.4 months), ≥1% (0.59, 0.41-0.83; NR versus 29.6 months), 1%-24% (0.67, 0.41-1.10; 43.3 versus 30.5 months), and unknown (0.60, 0.43-0.84; 44.2 versus 23.5 months), but not <1% (1.14, 0.71-1.84; 33.1 versus 45.6 months). Safety was similar across subgroups.

CONCLUSIONS

PFS benefit with durvalumab was observed across all subgroups, and OS benefit across all but TC <1%, for which limitations and wide HR CI preclude robust conclusions.

Synergistic effects of nelfinavir and bortezomib on proteotoxic death of NSCLC and multiple myeloma cells

Exploiting protein homeostasis is a new therapeutic approach in cancer. Nelfinavir (NFV) is an HIV protease inhibitor that induces endoplasmic reticulum (ER) stress in cancer cells. Under conditions of ER stress, misfolded proteins are transported from the ER back to the cytosol for subsequent degradation by the ubiquitin–proteasome system. Bortezomib (BZ) is a proteasome inhibitor and interferes with degradation of misfolded proteins. Here, we show that NFV and BZ enhance proteotoxicity in non-small cell lung cancer (NSCLC) and multiple myeloma (MM) cells. The combination synergistically inhibited cell proliferation and induced cell death. Activating transcription factor (ATF)3 and CCAAT-enhancer binding protein homologous protein (CHOP), markers of ER stress, were rapidly increased, and their siRNA-mediated knockdown inhibited cell death. Knockdown of double-stranded RNA activated protein kinase-like ER kinase, a signal transducer in ER stress, significantly decreased apoptosis. Pretreatment with the protein synthesis inhibitor, cycloheximide, decreased levels of ubiquitinated proteins, ATF3, CHOP, and the overall total cell death, suggesting that inhibition of protein synthesis increases cell survival by relieving proteotoxic stress. The NFV/BZ combination inhibited the growth of NSCLC xenografts, which correlated with the induction of markers of ER stress and apoptosis. Collectively, these data show that NFV and BZ enhance proteotoxicity in NSCLC and MM cells, and suggest that this combination could tip the precarious balance of protein homeostasis in cancer cells for therapeutic gain.

Ceramide mediates nanovesicle shedding and cell death in response to phosphatidylinositol ether lipid analogs and perifosine

Anticancer phospholipids that inhibit Akt such as the alkylphospholipid perifosine (Per) and phosphatidylinositol ether lipid analogs (PIAs) promote cellular detachment and apoptosis and have a similar cytotoxicity profile against cancer cell lines in the NCI60 panel. While investigating the mechanism of Akt inhibition, we found that short-term incubation with these compounds induced rapid shedding of cellular nanovesicles containing EGFR, IGFR and p-Akt that occurred in vitro and in vivo, while prolonged incubation led to cell detachment and death that depended on sphingomyelinase-mediated generation of ceramide. Pretreatment with sphingomyelinase inhibitors blocked ceramide generation, decreases in phospho-Akt, nanovesicle release and cell detachment in response to alkylphospholipids and PIAs in non-small cell lung cancer cell lines. Similarly, exogenous ceramide also decreased active Akt and induced nanovesicle release. Knockdown of neutral sphingomyelinase decreased, whereas overexpression of neutral or acid sphingomyelinase increased cell detachment and death in response to the compounds. When transferred in vitro, PIA or Per-induced nanovesicles increased ceramide levels and death in recipient cells. These results indicate ceramide generation underlies the Akt inhibition and cytotoxicity of this group of agents, and suggests nanovesicle shedding and uptake might potentially propagate their cytotoxicity in vivo.

A phase I study of nelfinavir, an FDA approved HIV protease inhibitor, in adults with refractory solid tumors

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Background: Preclinical studies show that HIV protease inhibitors such as nelfinavir (N) have dose- dependent, pleiotropic anti-cancer activities. However, the maximum tolerated dose (MTD) of N has not been established in humans. Methods: Pts were treated on a modified Fibonacci dose-escalation scheme with a twice daily oral dose of N starting at the FDA approved dose of 1250 mg bid on a 21-day cycle. Patients with refractory solid tumors, ECOG PS < 2, and adequate organ function were eligible. Therapy continued until MTD or disease progression. PBMCs as well as optional tumor biopsies were collected for Akt inhibition and expression of markers of ER stress (ERS). Results: 14 patients have been enrolled. Of the 11 evaluable for toxicity, there were 10 men, 10 Caucasians, and 1 African American (median age 63 years (range 24 - 77)). Tumor types included NSCLC (3), SCLC (2), thyroid (3), pancreatic (1), colorectal (1), and renal cell (1). Median number of prior systemic therapies was 2 (range, 1 - 6). There have been no grade 4 or 5 toxicities. We observed 12 grade 3 toxicities that were asymptomatic laboratory abnormalities. The most prevalent toxicities were ALT transaminitis (5 events in 8 subjects in dose level ((DL) 2, 3, 4), AST transaminitis (4 events in 8 subjects in DL 2, 4), diarrhea (8 events in 5 subjects in DL 2, 3, 4), and hyperglycemia (5 events in 5 subjects in DL 1, 2, 3). Enrollment continues at DL 4 (3125 mg twice daily). There have been no responses. Two subjects with lung cancer had stable disease for 9 weeks. Pharmacokinetic data revealed median Cmax of 2,461.5 ng/ml (DL1), 11,809 ng/ml (DL2), 11,576 ng/ml (DL3), and 11,986 ng/ml (DL4), occurring 4 hours after an oral dose. There was no relationship between the drug levels and albumin levels. Akt inhibition and increased expression of markers of ERS and apoptosis have been observed in PBMCs from week 1 in the majority of patients at every dose level, but there was no correlation with clinical response. Conclusions: N appears to be well tolerated in subjects with advanced solid tumors at 2.5 times the FDA approved dose. AUC data suggest that there may be only minimal increases in plasma drug concentrations with doses above 1875 mg twice daily.

No significant financial relationships to disclose.

Prognostic significance of clinical features and Akt activation in the survival of patients with bronchioloalveolar carcinoma (BAC)

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Background: Lung cancer is the leading cause of cancer related mortality in the world. BAC is a subset of NSCLC that has recently gained attention because of enhanced efficacy of epidermal growth factor receptor (EGFR) inhibitors in this population. Prognostic features for BAC have not been well defined. Because activation of Akt is a poor prognostic factor for other types of NSCLC, and because changes in Akt may predict outcome for EGFR inhibitors, we assessed the prognostic significance of clinical features and Akt activation in patients with BAC. Methods: 46 cases of BAC were classified according to WHO 2001 criteria. Akt activation was assessed using immunohistochemistry. Associations between ordered Akt levels and other dichotomous parameters were evaluated using an exact Cochran-Armitage test for trend. Survival was analyzed by the Kaplan-Meier method, and hazard ratios (HR) were determined based on Cox proportional hazard models. Results: Tissues from 45 patients were analyzed. Age and histology (mucinous vs. non-mucinous) were not associated with survival. Akt activation was observed in 63% of cases, but was not associated with differences in survival. Complete clinical data (except smoking) were available for 43 patients, and smoking history was available for 31 patients (8 never-smokers, 23 smokers). Cox model analysis revealed that male gender (HR 2.24, 95% CI 1.07–4.71, p = 0.032) and advanced stage (III or IV) (HR 2.17, 95% CI 1.004–4.71, p = 0.049) were associated with a worse prognosis. A model limited only to the 31 patients with smoking data demonstrated that smoking alone (HR 6.89, 95% CI 1.49–31.88, p = 0.013) was associated with a worse prognosis. Conclusions: These studies identify gender, stage, and especially smoking status as potentially important prognostic features for BAC. Akt was not prognostic. Given that the recent NSCLC clinical trials with erlotinib and gefitinib that showed varying survival benefit did not stratify by smoking status and BAC, it is possible that these characteristics could have affected the clinical outcomes. Investigators studying EGFR inhibitors should consider stratifying by smoking status and BAC to determine if there are subsets of patients who could benefit most from these therapies.

No significant financial relationships to disclose.

Variable apoptotic response of NSCLC cells to inhibition of the MEK/ERK pathway by small molecules or dominant negative mutants

To evaluate the role of the MEK/ERK pathway in NSCLC survival, we analyzed NSCLC cell lines that differed in tumor histology and status of p53, Rb, and K-ras. Constitutive ERK1/2 activity was demonstrated in 17 of 19 cell lines by maintenance of ERK1/2 phosphorylation with serum deprivation. Phosphorylation of ERK1/2 correlated with phosphorylation of MEK1/2 and p90RSK, but was inversely correlated with phosphorylation of c-Raf at S259. With serum deprivation, the MEK inhibitors, PD98059 and U0126, inhibited ERK1/2 activity but did not increase apoptosis. PD98059 and U0126 induced cell cycle arrest in G(0)/G(i) in cells with the highest levels of ERK1/2 activity, which correlated with induction of p27 but not p21. To confirm the cytostatic response to MEK inhibitors, we performed transient transfections with dominant negative forms of MEK or ERK. Surprisingly, dominant negative MEK and ERK mutants increased apoptosis without affecting cell cycle or p27 levels. When combined with paclitaxel, MEK inhibitors had no effect on apoptosis. In contrast, dominant negative ERK2 potentiated paclitaxel-induced apoptosis. Our studies show that constitutive ERK1/2 activity in NSCLC cells promotes cellular survival and chemotherapeutic resistance. Moreover, our data are the first to demonstrate divergent cellular responses to inhibition of the MEK/ERK pathway by small molecule inhibitors or dominant negative mutants.

Downregulation of p21/WAF1 expression by thymidylate synthase

We developed a cell system where expression of thymidylate synthase (TS), an enzyme essential for DNA synthesis, can be modulated by a Zn(2+)-inducible promoter in MCF-7 cells. We found that overexpression of TS resulted in downregulation of p21 protein and mRNA levels. Statistical analysis demonstrated a significant downregulation of p21, but not a statistically significant decrease in p53 protein levels following TS induction. Since p21 is known to be transcriptionally activated by p53, these results suggest that TS downregulation of p21 may be occurring through a p53-independent mechanism in this in vitro cell system. In addition, cell cycle analysis demonstrated that downregulation of p21 by TS resulted in a decreased G(1)/S ratio in MCF-7 cells.

Down-regulation of the erbB-2 receptor by trastuzumab (herceptin) enhances tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis in breast and ovarian cancer cell lines that overexpress erbB-2

We investigated whether combined treatment with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and trastuzumab could enhance the specific killing of cells that overexpress the erbB-2 receptor. The combination resulted in an enhancement of TRAIL-mediated apoptosis in all cell lines overexpressing erbB-2 receptor compared with either reagent alone. In contrast, there was no effect in cell lines with low levels of the erb-B2 receptor. Trastuzumab treatment resulted in down-regulation of the erbB-2 receptor in all erbB-2-overexpressing cell lines. Similar enhancement of TRAIL toxicity was observed when the erbB-2 receptor was down-regulated using antisense oligodeoxynucleotides. Down-regulation of the erbB-2 receptor protein by trastuzumab or antisense oligodeoxynucleotides decreased Akt kinase activation but not mitogen-activated protein kinase activation. Down-regulation of Akt kinase activity by a phosphatidylinositol 3'-kinase inhibitor (LY294002) also resulted in enhancement of TRAIL-mediated apoptosis. Expression of a constitutively active form of Akt kinase in an erbB-2-overexpressing cell line completely abrogated the increase in TRAIL-mediated apoptosis by trastuzumab and significantly reduced the biological effect of either reagent alone. Therefore, down-regulation of the erbB-2 receptor by trastuzumab enhances TRAIL-mediated apoptosis by inhibiting Akt kinase activity. These data suggest that the combination of trastuzumab and TRAIL may allow enhanced therapeutic efficacy and specificity in the treatment of erbB-2-overexpressing tumors.

Akt/protein kinase B is constitutively active in non-small cell lung cancer cells and promotes cellular survival and resistance to chemotherapy and radiation

To evaluate the role of Akt/PKB in non-small cell lung cancer (NSCLC) survival, we analyzed NSCLC cell lines that differed in tumor histology as well as p53, Rb, and K-ras status. Constitutive Akt/protein kinase B (PKB) activity was demonstrated in 16 of 17 cell lines by maintenance of S473 phosphorylation with serum deprivation. Additional analysis of five of 2these NSCLC lines revealed that phosphorylation of S473 and T308 correlated with in vitro kinase activity. Akt/PKB activation was phosphatidylinositol 3-kinase-dependent and promoted survival because the phosphatidylinositol 3 inhibitors LY294002 and wortmannin inhibited Akt/PKB phosphorylation, Akt/PKB activity, and increased apoptosis only in cells with active Akt/PKB. To test whether Akt/PKB activity promoted therapeutic resistance, LY294002 was added with individual chemotherapeutic agents or irradiation. LY294002 greatly potentiated chemotherapy-induced apoptosis in cells with high Akt/PKB levels, but did not significantly increase chemotherapy-induced apoptosis in cells with low Akt/PKB levels. Combined with radiation in cells with active Akt/PKB, LY294002 additively increased apoptosis and inhibited clonogenic growth. These results were extended with transiently transfected Akt/PKB mutants. Transfecting dominant negative Akt/PKB decreased Akt/PKB activity and increased basal apoptosis as well as chemotherapy- and irradiation-induced apoptosis only in cells with high Akt/PKB activity. Conversely, transfecting constitutively active Akt/PKB into cells with low Akt/PKB activity increased Akt/PKB activity and attenuated chemotherapy- and radiation-induced apoptosis. We therefore identify Akt/PKB as a constitutively active kinase that promotes survival of NSCLC cells and demonstrate that modulation of Akt/PKB activity by pharmacological or genetic approaches alters the cellular responsiveness to therapeutic modalities typically used to treat patients with NSCLC.

Human smooth muscle alpha-actin gene is a transcriptional target of the p53 tumor suppressor protein

Smooth muscle (sm) alpha-actin is expressed in vascular smooth muscle cells and fibroblast cells. Its expression is regulated by cell proliferation and repressed during oncogenic transformation. In this study, we demonstrate that p53 activation is associated with a dramatic increase in organized microfilament bundles and an increase in sm alpha-actin mRNA level. Wild-type p53, but not mutant p53, strongly stimulated human sm alpha-actin promoter activity in p53 null cell lines. The sequences homologous to the p53 consensus sequence and to the p53 binding sequence from the muscle creatine kinase, were found within a specific region of the sm alpha-actin promoter. This sequence was sufficient to confer p53-dependent activation to a heterologous promoter and p53 was capable of binding to this sequence as assessed by gel shift analysis. Ionizing irradiation of colorectal tumor cells caused an increase in alpha-actin mRNA level in a p53-dependent manner. Taken together, these results demonstrate that human sm alpha-actin gene is a transcriptional target for p53 tumor suppressor protein and represents the first example of a cytoskeletal gene with a functionally defined p53 response element.

Cellular survival pathways and resistance to cancer therapy

Chemotherapy and irradiation induce programmed cell death (apoptosis) in their target cells. Dysregulated apoptosis is a feature that is selected for during tumor formation and contributes to therapeutic resistance. Cell survival in the face of cytotoxic therapy is dictated by both internal properties of the cell, such as status of components of the apoptotic machinery, and its extracellular milieu, such as extracellular matrix (ECM) and growth factor receptor expression and signaling. The importance of extracellular survival signals as key regulators of apoptosis is now being recognized by the ability of growth factors (GFs), GF receptors (GFRs), and GFR signaling to promote cellular survival. GFs can mitigate or abrogate the effectiveness of cancer therapy and protect against other cellular insults. Because survival signals generated by different extracellular sources converge at key molecules, new molecular targets have been identified which could be exploited to maximize the effectiveness of cytotoxic cancer therapy.

Paralytic peptides from hemolymph of the lepidopteran insect Trichoplusia ni Hubner

1. Two paralytic peptides were isolated and identified from hemolymph of Trichoplusia ni Hubner. 2. These peptides cause rapid, rigid paralysis when injected into the lepidopteran insect, Manduca sexta. 3. The paralytic dose (ED50) of one peptide is 0.05 micrograms/g and the other is 0.9 micrograms/g. 4. Sequences are very similar to paralytic peptides from the hemolymph of other lepidopteran insects.

Identification of insecticidal peptides from venom of the trap-door spider, Aptostichus schlingeri (Ctenizidae)

Nine insecticidal peptides were isolated from the venom of the trap-door spider, Aptostichus schlingeri. Seven of these toxins cause flaccid paralysis of insect larvae within 10 min of injection and all were lethal within 24 hr. The complete amino acid sequences (32-76 residues) of six peptides are presented. The identified peptides contain three or four disulfide bonds and the larger peptides (74-76 residues) are quite similar in sequence with carboxyl termini as free acids, not amidated.

Isolation and identification of paralytic peptides from hemolymph of the lepidopteran insects Manduca sexta, Spodoptera exigua, and Heliothis virescens

Seven paralytic peptides were isolated and identified from lepidopteran hemolymph. All of these peptides cause rapid, rigid paralysis when injected into Manduca sexta and some other lepidopteran larvae. Each peptide contains 23 amino acid residues including 2 cysteines and the carboxyl termini are acidic. Synthetic peptides in the disulfide or reduced forms, and as carboxyl-terminal acids or amides were equally paralytic. The most potent paralytic peptide, Mas PP I, has the following sequence: H-Glu-Asn-Phe-Ala-Gly-Gly-Cys-Ala-Thr-Gly-Tyr-Leu- Arg-Thr-Ala-Asp-Gly-Arg-Cys-Lys-Pro-Thr-Phe-OH. The two peptides from M. sexta hemolymph are remarkable in that they are autoparalytic (i.e. factors in collected hemolymph that are paralytic when injected into the same larvae).

Cellular activation of latent transforming growth factor beta requires binding to the cation-independent mannose 6-phosphate/insulin-like growth factor type II receptor

The activation of latent transforming growth factor beta (LTGF-beta) normally seen in cocultures of bovine aortic endothelial and bovine smooth muscle cells can be inhibited by coculturing the cells with either mannose 6-phosphate (Man-6-P) or antibodies directed against the cation-independent Man-6-P/insulin-like growth factor type II receptor (anti-Man-6-PR). This result was established by measuring the ability of coculture conditioned medium (formed with or without Man-6-P or anti-Man-6-PR) to suppress bovine aortic endothelial cell migration and protease production, activities previously shown to be related to transforming growth factor beta activity. The inhibition by Man-6-P is dose dependent, with maximal inhibition seen at 100 microM and is specific because mannose 1-phosphate and glucose 6-phosphate do not interfere with activation of LTGF-beta. The inhibitory effect of anti-Man-6-PR is also specific and dose dependent; maximal inhibition of activation occurs at 400 micrograms/ml. Control experiments indicate that Man-6-P and anti-Man-6-PR do not interfere with the basal level of migration of bovine aortic endothelial cells, the migration observed when exogenous transforming growth factor beta is added, the activation of transforming growth factor beta by plasmin or transient acidification, and the release of LTGF-beta. Thus, binding to the cation-independent Man-6-P/insulin-like growth factor type II receptor appears to be a requirement for activation of LTGF-beta.

Paralytic and insecticidal toxins from the funnel web spider, Hololena curta

One peptide and ten acylpolyamine toxins (curtatoxins) were purified and identified from venom of Hololena curta. The acylpolyamines consist of six different polyamines which are amidated with three different aromatic acids: (3-indolyl)acetic, (4-hydroxy-3-indolyl)acetic and 2.5-dihydroxybenzoic acids. These acylpolyamines instantly paralyze lepidopteran larvae following injection. The most potent insecticidal peptide in H. curta venom contains 38 amino acids and is lethal at 4 micrograms/g when injected into Manduca sexta larvae.

Studies on the role of basic fibroblast growth factor in vivo: inability of neutralizing antibodies to block tumor growth

Affinity-purified polyclonal rabbit antibodies prepared against recombinant basic fibroblast growth factor (bFGF) neutralized the ability of bFGF to stimulate plasminogen activator (PA) production and endothelial cell migration in vitro. After iodination and intraperitoneal injection of the antibodies in mice, approximately 76% of the maximum circulating level of 125I-anti-bFGF antibodies (AF) was found as intact IgG after 24 hr. Furthermore, the circulating 125I-AF retained the ability to bind bFGF. Studies were performed to determine whether the growth of three different murine tumors (CT26, EHS, or B16/BL6) could be inhibited with affinity-purified neutralizing antibodies against bFGF. Tumors were injected subcutaneously in syngeneic mice, and neutralizing antibodies against bFGF were injected daily into the peritoneum. All studies, which varied in tumor burden, antibody dose, and study length, indicated that neutralizing antibodies against bFGF had no effect on tumor size, tumor growth, or tumor histology.

Chemical characterization of acylpolyamine toxins from venom of a trap-door spider and two tarantulas

Two acylpolyamines are identified from venom of the trap-door spider, Hebestatis theveniti. These toxins (paralytic to lepidopteran insect larvae) are amides containing 3-(3-indolyl)lactic acid joined to spermine or 1,13-diamino-4,10-diazatridecane (Het389 and Het403, respectively). Het389 is also abundant in venom from a tarantual from Mozambique (Harpactirella sp.). Two additional acylpolyamines (Apc600 and Apc728) are partially characterized from venom of another tarantula, Aphonopelma chalcodes.

Prevention of hemodialysis fistula thrombosis. Early detection of venous stenoses

Venous dialysis pressures were measured consecutively in 168 chronic hemodialysis patients for 265 patient-years of monitored dialysis. Venous dialysis pressure greater than 150 mm Hg measured by the protocol were considered elevated. Seventy-three patients had elevated venous dialysis pressures and 58 agreed to undergo elective venography (fistulogram). Fifty of 58 patients studied (86%) had significant venous stenoses. A combination of percutaneous transluminal angioplasty (PTA) and surgical revision were used to electively treat these stenoses. Early detection and treatment of these stenoses decreased fistula thrombosis and fistula replacement threefold compared with our earlier experiences. Patients with elevated venous dialysis pressure who were venogramed and treated had an occurrence of fistula thrombosis similar to patients with normal dialysis pressure (0.15 and 0.13 episodes per patient year of dialysis respectively, P = NS). In contrast patients with elevated venous dialysis pressure who refused elective fistulogram and treatment averaged 1.4 episodes of thrombosis per patient year of dialysis (P less than 0.001) compared to both other groups). We conclude that elevated venous dialysis pressure is a reliable method of detecting fistula stenoses and that the elective treatment of these stenoses significantly decreases fistula thrombosis and fistula loss.

Alpha 2-macroglobulin is a binding protein for basic fibroblast growth factor

After incubation with human serum or plasma, 125I-basic fibroblast growth factor (bFGF) (molecular mass 18.5 kDa) exhibits molecular mass forms greater than 200 kDa as determined by nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography. These high molecular mass forms of bFGF are immunoprecipitable with antiserum raised against alpha 2-macroglobulin (alpha 2M). Purified alpha 2M and 125I-bFGF form a covalent complex in a specific, saturable manner. Excess unlabeled bFGF competes with 125I-bFGF for complex formation. Complex formation is complete after 4 h and is inhibited by pretreating alpha 2M with dithiothreitol, iodoacetamide, iodoacetic acid, and N-ethylmaleimide. The complex is resistant to acidic conditions and denaturants such as urea. Heparin, which binds bFGF, has no effect on complex formation. Methylamine, which blocks protease binding to alpha 2M, increases the amount of 125I-bFGF that can be bound 2-fold. Plasmin and trypsin treatment of alpha 2M has no effect on 125I-bFGF binding. The ability of growth factors to compete for binding is specific, as aFGF and TGF-beta compete for binding to alpha 2M, whereas platelet-derived growth factor does not. 125I-bFGF.alpha 2M complexes do not bind to low affinity bFGF binding sites and bind poorly to high affinity bFGF binding sites on BHK-21 cells. In addition, 125I-bFGF bound to alpha 2M has decreased ability to stimulate plasminogen activator production in bovine capillary epithelial cells.

GTP gamma S loading of endothelial cells stimulates phospholipase C and uncouples ATP receptors

The effects of GTP gamma S, a stable GTP analogue that can activate guanine nucleotide-binding proteins, on phospholipase C activation/calcium mobilization were studied in intact cultured bovine aortic endothelial cells (BAEC). Phosphoinositide metabolism and cytosolic free Ca2+ concentration [( Ca2+]i; fura-2 fluorescence) were studied after the cells were transiently permeabilized, loaded with different guanine nucleotides, and then allowed to reseal and recover. Intracellular GTP gamma S stimulated a dose-dependent [median effective concentration (EC50) 2.5 microM] decrease in basal [3H]phosphoinositide content. Phosphatidylinositol 4,5-bisphosphate, phosphatidylinositol 4-bisphosphate, and phosphatidylinositol levels decreased to 57 +/- 9, 63 +/- 8, and 74 +/- 8% control levels, respectively, in BAEC loaded with approximately 85 microM GTP gamma S. Basal inositol trisphosphate (IP3) and [Ca2+]i were increased in GTP gamma S-loaded BAEC when compared with sham-loaded BAEC. In control BAEC, the purinergic receptor agonist ATP (100 microM) induced rapid increases in [Ca2+]i and IP3. However, BAEC that had been intracellularly loaded with GTP gamma S [median inhibitory constant (IC50) 1 microM] or 5'-guanylyl-imidodiphosphate exhibited decreased calcium mobilization in response to ATP. Ionomycin (calcium ionophore)-releasable pools of calcium were similar in sham- and GTP gamma S-loaded cells, suggesting that total intracellular calcium had not been depleted by the permeabilization protocol. The diminished calcium mobilization in response to ATP was associated with decreases in ATP-stimulated PIP2 hydrolysis and IP3 formation. In addition, GTP gamma S loading did not increase basal levels of cyclic AMP. Intracellular GDP beta S, GDP, or GTP did not inhibit ATP-stimulated increases in [Ca2+]i or IP3.(ABSTRACT TRUNCATED AT 250 WORDS)

Venular endothelium in vitro: isolation and characterization

The structural and functional properties of the endothelium vary in relation to anatomic site and position along the vascular tree. Cultures of endothelial cells have been obtained so far from large arteries, large veins and capillaries, but not from venules. We now report techniques for culturing not only rat arterial and venous endothelium, but also a special method for obtaining and culturing venular endothelium. The technique is based on the principle of "vascular labeling," whereby an insoluble pigment can be permanently deposited in the wall of the venules, making them easily visible by light microscopy. The venules of a rat cremaster muscle are labeled with a local injection of histamine followed by Monastral blue B intravenously (i.v.); 24 hours later selected venules are isolated by microdissection and either enzymatically dispersed or placed directly into tissue culture wells. The wells are coated with fibronectin and laminin and supplemented with DMEM, 20% fetal calf serum, and endothelial cell growth factor. Polygonal and spindly endothelial cells begin as clusters, grow in sheets, and sometimes form tubes. The cells stain variably for Factor VIII-related antigen, Ulex Europeus I lectin, and non-muscle specific actin. They synthesize angiotensin-converting enzyme, but do not metabolize acetylated LDL. Ultrastructurally, they display pinocytic vesicles, microtendons, and tight junctions, but not Weibel-Palade bodies. We believe that this method will be important for studying the pathophysiology of venules, which are the preferential target of inflammatory mediators and the typical site of inflammatory cell diapedesis.

Hemodialysis without anticoagulation. One-year prospective trial in hospitalized patients at risk for bleeding

This prospective study evaluated a protocol for hemodialysis without anticoagulation in a diverse group of hospitalized patients in unstable condition with relative contraindications to anticoagulation. Of 262 attempts at hemodialysis without anticoagulation in 49 patients, 239 hemodialysis treatments (91 percent) were successfully completed. Approximately 7 percent of the attempts required conversion to a low-dose heparin regimen because of clotting in the extracorporeal dialysis circuit. Fewer than 2 percent of the dialysis treatments resulted in clotting in the extracorporeal circuit sufficient to interrupt hemodialysis. Partial thromboplastin times and activated clotting times did not change during these hemodialysis treatments. Solute clearance, ultrafiltration rate, and decrements in arterial oxygen concentration and platelet count were not different from those in patients who underwent hemodialysis with anticoagulation. There were no episodes of accelerated bleeding associated with this dialysis method. This study indicates that hemodialysis without anticoagulation can be reliable and effective in closely monitored situations.

The reimplanted ureter as a catheterizing stoma

Some current trends in the management of neurogenic bladder have been toward utilization of the urinary bladder as a storage device with a continent catheterizing stoma. This study presents a procedure using the now standard Cohen ureteral reimplantation, followed some 6 weeks later by transureteroureterostomy and distal ureteral stomal formation, after the method of Mitrofanoff. This staged procedure appears to have allowed the recently reimplanted ureter to be divided and brought to the skin as a viable catheterizing stoma. We believe that this experimental study has demonstrated that the Cohen technique of ureteral reimplantation is a reasonable antecedent to the use of transureteroureterostomy and distal ureteral stoma creation for continent catheterization. Monfort has demonstrated this clinically in one patient, and we feel that this technique deserves more extensive clinical trials.

Time course of release into the medium of newly synthesized proteins by cultured aortic endothelial cells. Role of serum in preventing proteolytic degradation

Endothelial cells from pig aortas were labeled with 35S-methionine, and the soluble proteins that were released into the culture medium were examined by SDS-PAGE. Proteins were collected during labeling, and during the intervals 0 to 3, 3 to 6, 6 to 12, and 12 to 24 hours of chase after a 1-hour labeling period, and during the intervals 0 to 12, 12 to 24, and 24 to 48 hours of chase after a 24-hour labeling period. Release of radiolabeled soluble protein from cells into the medium continued over the longest time periods examined. If the cells were labeled for 1 hour, characteristic patterns of proteins appeared in the medium during the labeling period, early (0- to 3-hour postlabeling) and late (6- to 24-hour postlabeling). The time course of release of fibronectin (Fn) and of angiotensin-converting enzyme (ACE) was determined by using immunoprecipitation. ACE appeared only after 6 hours of chase. Fn appeared throughout the chase period. The effects of serum and of the protease inhibitors alpha-2 macroglobulin, pepstatin, and leupeptin on protein release were examined. In the absence of serum, endothelial cell culture medium contained substantial protease activity capable of completely degrading most of the released proteins; a major effect of serum was to protect newly released protein from degradation.

Growth and analysis of vascular smooth muscle on microspheres

Protocols for culturing vascular smooth muscle cells (VSMCs) on polystyrene microspheres, assessing VSMC contractility while adhered to the microspheres, and analyzing VSMCs cultured on microspheres by flow cytometry are described. These procedures preserve optimal VSMC viability and function, while providing a method for assessing these cells within the parameters required for analysis by flow cytometry.

Metabolism of [3H]leupeptin by rat liver

Tritium-labeled leupeptin was used to study how this tripeptide proteinase inhibitor interacts with the liver, including the mechanism of its transport into the cell, its subcellular distribution after uptake, and its metabolism once in the tissue. Experiments were done in situ and in a perfused liver. At low concentrations (1 to 10 microM) the uptake of radioactive inhibitor was competed by chemically reduced leupeptin. At high concentrations at least up to 400 microM the uptake was directly proportional to the external concentration of tripeptide. Entry into the tissue essentially stopped at low temperature (less than 21 degrees C). [3H]Leupeptin initially was located in the soluble fraction of the liver homogenate and by 15 to 30 min became concentrated in the lysosome-rich fraction. During 2 h of perfusion almost 50% of [3H]leupeptin that had entered the liver was secreted intact into the bile. In addition, a portion of the leupeptin that remained in the liver was degraded during this time period.

Uptake and degradation of 125I-labeled rat asialoorosomucoid by the perfused rat liver

The uptake and degradation of a homologous rat serum asialoglycoprotein, 125I-asialoorosomucoid, and the effects on this metabolism by leupeptin, a proteinase inhibitor, were studied in the perfused rat liver. 125I-Asialoorosomucoid was rapidly taken up by the liver (t1/2 = 5.7 min) and acid-soluble degradation products began to appear in the circulating perfusate medium after 20-30 min. These products accounted for 60-65% of the initially added radioactivity after 90 min of perfusion. The early events in the galactose-mediated uptake of 125I-asialoorosomucoid were unchanged by the presence of leupeptin. However, the appearance of acid-soluble degradation products was greatly reduced when livers had been pretreated with the inhibitor (1.0 mg for 60 min). This effect corresponded with an increase in acid-precipitable material being located within the lysosomal-rich fraction from homogenates of leupeptin-treated livers. Leupeptin inhibited degradation of 125I-asialoorosomucoid by approx. 85% relative to control values over 90 min of perfusion. Inhibition of asialoorosomucoid degradation was also demonstrated in vitro. Leupeptin (1.0 mM) reduced hydrolysis of this glycoprotein substrate by greater than 50% during a 24 h incubation with isolated lysosomal enzymes. The thiol proteinases, cathepsin B, H and L, which are known to be inhibited by leupeptin, are apparently involved in initiating digestion of rat 125I-asialoorosomucoid within liver lysosomes. As a result of inhibition by leupeptin both in the perfused liver and in vitro very limited changes occurred in the native molecular weight of the starting glycoprotein.

A fatal episode of accidental methomyl poisoning

Three fatalities from the accidental ingestion of methomyl, a carbamate pesticide, are reported. The methomyl had been stored in an unlabeled tin can and was accidentally used in preparing "roti," an Indian dish. The identification of the source of the poison through animal tests and further chemical identification is described. The lethal dose of methomyl was estimated to have been between 12 and 15 mg/kg body weight.