Tumor response and adaptation to CYP17 inhibition in prostate cancer: Induction of steroidogenesis and androgen receptor splice variants

18

Background: Abiraterone is a novel inhibitor of the steroidogenic enzyme CYP17 and suppresses tumor growth in patients with castration-resistant prostate cancer (CRPC). The efficacy of abiraterone in suppressing tumor androgens or mechanisms of resistance to abiraterone are not known.

Methods: Human CRPC xenografts LuCaP 23 and LuCaP 35 grown in castrated male mice were treated with abiraterone to determine effects on tumor growth and tumor androgen levels. Tumor gene expression measurements were obtained to delineate mechanisms of abiraterone resistance.

Results: Abiraterone i.p. for 21 days improved survival (time to tumor size 750 mm3) vs vehicle control (VC) in LuCaP 35 (HR 3.8 [95% CI 3.1-53.7] median survival 39 vs 18 days) and LuCap 23 (HR 2.4 [1.43-10.24] median survival 24 vs. 14 days). Greater anti-tumor activity correlated with superior tumor androgen suppression. Tumor testosterone was strongly suppressed in both LuCaP35 (0.20 + 0.24 vs VC 0.69 + 0.36 pg/mg) and LuCaP 23 (0.07 + 0.11 vs VC 0.49 + 0.22 pg/mg). DHT levels were also markedly suppressed in LuCaP35 (1.17 + 1.46 vs VC 3.49 + 1.81pg/mg). In contrast, DHT levels in LuCap23 were unchanged early (day 7-21) and only partially suppressed at longer time points (VC 5.73 + 1.88; early 5.31 + 2.69; late 2.82 + 2.27 pg/mg). Expression of the abiraterone target CYP17 was upregulated in both xenografts (LuCaP23 2.5 fold, p<0.0001; LuCap35 2.9 fold, p=0.028). Overall, LuCap23 appeared resistant to suppression of tumor androgens due to induction of steroidogenic transcripts (including STAR, CYP11, HSD3B1 and AKR1C3) without statistically significant increases in androgen receptor (AR). In contrast, LuCap35 demonstrated strong induction of transcripts for AR and AR splice variants (AR 3.8 fold, p<0.0001, V7 AR splice variant 3.7 fold, p<0.0001), with induction of steroidogenic transcripts only at late time points.

Conclusions: Abiraterone treatment suppressed intratumoral androgen levels and reduced growth of CRPC xenografts. Abiraterone resistance may occur through upregulation of the abiraterone target CYP17, and/or the induction of AR and AR splice variants that confer ligand-independent AR trans-activation.

[Table: see text]

On-target activity of neoadjuvant cixutumumab and combined androgen deprivation therapy for high-risk prostate cancer: A phase II trial

153

Background: IMC-A12 (cixutumumab) is a fully human monoclonal antibody which targets the insulin-like growth factor receptor 1. Preclinical data suggests that the combination of androgen deprivation and IMC-A12 is much more effective than either treatment alone. This clinical trial tests the effectiveness of the combined treatment in a neoadjuvant fashion before radical prostatectomy. We have assayed serum samples from the first 18 patients to identify signs of on-target activity in this setting.

Methods: Eligible men with high risk localized prostate cancer are defined by one of the following: Gleason score ≥ 8, PSA ≥ 20, Clinical Stage T2c-T3, or a risk for relapse exceeding 50% as defined by the Kattan nomogram. Men are treated for 3 months with goserelin, bicalutamide, and biweekly IMC-A12 infusions (10 mg/kg). The primary objective of the trial is to determine the rate of pathological complete response with an accrual goal of 28 men. Using samples from the first 18 patients on study, serum protein markers were assayed by ELISA and serum PSA and glucose levels were determined by clinical laboratory analysis.

Results: Significant increases in c-peptide (1.7-fold, p<0.01), IGF-I (4.1-fold, p<0.01), IGF-II (1.32-fold, p<0.001), IGFBP-3 (1.9-fold, p<0.01), growth hormone (8-fold, p<0.01) were noted after initiation of ADT+IMC-A12, compared to pre-treatment levels. Non-significant increases of insulin (1.9-fold), IGFBP-1 (2-fold), and glucose (1.24-fold) levels were seen. Stratification of patients by nadir PSA levels correlated with residual tumor volume, likelihood of positive surgical margins and likelihood of lymph node metastases. Interestingly, patients with lower nadir PSA levels had smaller increases in c-peptide (50%, p<0.01), insulin (66%, p<0.02) and blood sugar (21%, P<0.01) compared to the patients with higher nadir PSA levels.

Conclusions: Combined with ADT in the neoadjuvant setting, IMC-A12 effectively targets the IGF-1R axis in prostate cancer patients. Metabolic differences between patients may alter the efficacy of IMC-A12 in this setting.

[Table: see text]

Conditioning of a free operant in Octupus cyaneus Gray

Operant conditioning was studied in six specimens of Octopus cyaneus Gray. An "arm-out-of-water" operant, in which the octopus inserted an arm up a feeding-tube breaking the water surface, proved susceptible to reinforcement schedules. An apparatus was developed that provided automated reinforcement and recording. Performance was studied under continuous reinforcement, fixed-ratio and variable-ratio schedules, and extinction conditions.

Duration of the first off treatment period is associated with time to androgen independence (AI) and survival in men with localized or biochemical relapse of prostate cancer treated on a prospective trial of intermittent androgen deprivation (IAD)

5146

Background: Patients (pts) with localized prostate cancer or biochemical relapse who are treated with AD eventually develop AI and die. In an effort to better understand the natural history of this population, various characteristics of the patients and the first cycle of IAD were analyzed. Methods: Eligible pts had histological diagnosis of prostate cancer, no evidence of bone metastases by bone scan or visceral disease by CT scan, and at least 2 consecutive rising PSA = 2 weeks apart after diagnosis, radical prostatectomy (RP), or radiation therapy (XRT). Pts were treated with IAD consisting of 9 months of leuprolide acetate and an anti-androgen. Subsequently AD was stopped and monthly PSA and testosterone levels were followed during the off treatment period (Toff) until the PSA reached a threshold value (1 ng/mL if prostate removed or 4 ng/mL if prostate intact). At that time AD was resumed as before in a new cycle. Pts were treated until AI, defined as two rising PSAs while on AD with a castrate level of testosterone. Results: To date, 57 of 88 accrued pts are evaluable for this analysis. The median age at diagnosis is 62.2 yrs (range 43.9–77.4 yrs), median Gleason sum is 7. For the 49 pts with biochemical relapse after prior RP or XRT, median time from diagnosis to PSA relapse is 3.2 yrs (0–14.7 yrs) and from diagnosis to IAD was 4.9 yrs (range 0.1–14.9 yrs). For the 8 pts with no prior therapy, median time from diagnosis to IAD is 0.2 yrs (range 0–3.9 yrs). The median PSA value for all pts at study entry is 16 ng/mL (range 4–175 ng/mL); the value at study entry or after 3, 5, or 7 months of AD is not associated with time to AI or survival. Entry PSA is predictive of length of first Toff, and the length of the first Toff is associated with both time to AI (P<0.010) and survival (P<0.01). Conclusions: The duration of the first Toff in other studies of IAD should be evaluated for similar associations with time to AI and survival.

No significant financial relationships to disclose.

Expression of oncogenic epidermal growth factor receptor family kinases induces paclitaxel resistance and alters beta-tubulin isotype expression

Oncogenic transformation confers resistance to chemotherapy through a variety of mechanisms, including suppression of apoptosis, increased drug metabolism, and modification of target proteins. Oncogenic epidermal growth factor receptor family members, including EGFRvIII and HER2, are expressed in a broad spectrum of human malignancies. Cell lines transfected with EGFRvIII and HER2 are more resistant to paclitaxel-mediated cytotoxicity, and tubulin polymerization induced by paclitaxel is suppressed compared with cells expressing wild type epidermal growth factor receptor. Because differential expression of beta-tubulin isotypes has been proposed to modulate paclitaxel resistance, we analyzed beta-tubulin isotypes expressed in cell lines transfected with different oncogenes. EGFRvIII- and HER2-expressing cells demonstrated equivalent total beta-tubulin protein compared with cells transfected with wild type receptor or untransfected controls. EGFRvIII-expressing cells demonstrated increases in class IVa (2.5-fold) and IVb (3.1-fold) mRNA, and HER2-expressing cells showed increases in class IVa (2. 95-fold) mRNA. Expression of oncogenic Ha-Ras did not change class IV RNA levels significantly. Inhibition of EGFRvIII kinase activity using a mutant allele with an inactivating mutation in the kinase domain decreased expression of class IVa by 50% and partially reversed resistance to paclitaxel. Expression of oncogenic epidermal growth factor receptor family members is associated with modulation of both beta-tubulin isotype expression and paclitaxel resistance in cells transformed by expression of the receptor. This effect on tubulin expression may modulate drug resistance in human malignancies that express these oncogenes.

Constitutive activation of phosphatidylinositol 3-kinase by a naturally occurring mutant epidermal growth factor receptor

The most frequently found alteration of the epidermal growth factor receptor (EGFR) in human tumors is a deletion of exons 2-7. This receptor, termed EGFRvIII, can transform NIH 3T3 cells, and the frequent expression of this variant implies that it confers a selective advantage upon tumor cells in vivo. Although EGFRvIII is a constitutively activated tyrosine kinase, there is no increase in Ras.GTP levels and low levels of mitogen-activated protein kinase activity in NIH 3T3 cells expressing this variant. We investigated whether phosphatidylinositol (PI) 3-kinase was an effector in transformation by the EGFRvIII. High levels of PI 3-kinase activity were constitutively present in EGFRvIII-transformed cells and were dependent upon the kinase activity of the receptor. While mitogen-activated protein kinase activity was quickly down-regulated to basal levels after 12 h of continuous EGFR activation, there was a 3-fold increase in PI 3-kinase activity in cells expressing normal EGFR and an 8-fold increase in cells expressing EGFRvIII after 48 h. This increased activity may reflect enhanced binding to EGFRvIII and the presence of novel PI 3-kinase isoforms. Treatment with the PI 3-kinase inhibitors wortmannin and LY294002 blocked both anchorage-independent growth and growth in low serum media and also resulted in morphological reversion of EGFRvIII-transformed cells. These results support an essential role for PI 3-kinase in transformation by this EGFR variant.

Epidermal growth factor receptor stimulation of diacylglycerol kinase

The epidermal growth factor receptor (EGFR) activates formation of the phospholipid signal messenger phosphatidic acid (PA) on ligand binding. We explored the effects of chronic EGF stimulation on cellular PA in NIH3T3 cells expressing intact EGFR a mutant EGFR (EGFRvIII). The presence of EGFRvIII increased PA levels to twice those induced by chronic EGFR activation. Fatty acid methyl ester analysis revealed a marked increase in oleic acid containing PA. No apparent increase in phospholipase D (PLD) activity was detected, and diacylglycerol (DAG) kinase assays demonstrated a marked preference for dioleoyl DAG in the presence of activated EGFR or EGFRvIII. Levels of PA which were lower than would be predicted by DAG kinase activation are explained by increased phosphatidate phosphohydrolase activity. Specific inhibitors of EGFR kinase and DAG kinase suppressed DAG kinase activation and PA production by EGFRvIII. EGFR kinase activation by chronic exposure to ligand or by deletional mutation stimulates formation of a specific form of signalling PA.

Transformational and altered signal transduction by a naturally occurring mutant EGF receptor

An amino-truncated variant form of the epidermal growth factor receptor (EGFRvIII) has been identified in human brain, breast, lung and ovarian tumors. We have found that overexpression of this mutant EGF receptor in NIH3T3 cells results in transformation as a result of the activation of the receptor kinase via ligand-independent dimerization. Transformation was correlated with tyrosine phosphorylation of only a subset of the proteins observed in cells overexpressing the normal EGF receptor. This suggested that further studies on cells expressing the EGFRvIII might provide insights into the pathways most relevant to transformation. In clones expressing high levels of mutant EGF receptor, the levels of both Grb2 and SHC were decreased. Despite this decrease, much of the endogenous Grb2 immunoprecipitated with EGFRvIII. Interestingly, no increase in ras-GTP loading was found in clones expressing the EGFRvIII and MAP kinase assays indicated only a small increase in activity. These results indicate that high-level expression of the EGFRvIII induces down-regulation of the ras-MAP kinase pathway and that other components involved in EGF receptor signal transduction may play a greater role in neoplastic transformation by the EGFRvIII.

Differential modulation of mitogen-activated protein (MAP) kinase/extracellular signal-related kinase kinase and MAP kinase activities by a mutant epidermal growth factor receptor

A paradigm has been established whereby mutant tyrosine kinase receptors such as the v-erbB and v-fms gene products function as oncoproteins in the absence of ligand. A spontaneously occurring deletional mutant of the human epidermal growth factor receptor (EGFR-vIII) has been isolated from astrocytic neoplasms and transforms NIH3T3 cells in the absence of ligand. The EGFRvIII is constitutively complexed with the majority of cellular GRB2, suggesting a link to the Ras-Mitogen-activated protein (MAP) kinase pathway (D. Moscatello, R. B. Montgomery, P. Sundareshan, H. McDanel, M. Y. Wong, and A. J. Wong, submitted for publication). In this report, we document that expression of EGFRvIII in fibroblasts is associated with downstream activation of mitogen-activated protein (MAP) kinase/extracellular signal-regulated kinase (MEK) and modest activation of p42 and p44 MAP kinases. The presence of EGFRvIII suppresses activation of p42 and p44 MAP kinases by phorbol 12-myristate 13-acetate (PMA) and serum; however, MEK activation by PMA is not suppressed by EGFRvIII. Basal and PMA-stimulated MAP kinase activity in EGFRvIII-transfected cells is augmented by the tyrosine phosphatase inhibitor sodium vanadate. EGFR-vIII is capable of transducing downstream signals through MAP kinase as evidenced by activation of cytoplasmic phospholipase A2 at levels similar to that induced by intact EGFR. Our results suggest that EGFR-vIII constitutively activates downstream signal transduction through MAP kinase, and this chronic stimulation of the MAP kinase pathway may represent one means by which mutant EGFR transduces an oncogenic signal.

Pentoxifylline inhibits tumor necrosis factor-alpha-mediated cytotoxicity and cytostasis in L929 murine fibrosarcoma cells

Tumor necrosis factor-alpha (TNF alpha) is recognized as a principal mediator of a variety of inflammatory conditions. In animal models, pentoxifylline attenuates the morbidity and mortality of bacterial sepsis, an effect which has been attributed to its ability to suppress the induction of TNF alpha. To determine whether pentoxifylline also directly inhibits the effects of TNF alpha, the ability to inhibit cytotoxicity on the TNF alpha-sensitive murine fibrosarcoma cell line, L929, was examined. Cell viability was assessed by crystal violet staining and cell proliferation was assessed by [3H]-thymidine uptake assay. TNF alpha induced dose-dependent cytotoxicity. At concentrations of TNF alpha of 1000 U/ml, viability at 3 days was approximately 35% of control. When L929 cells were co-incubated with TNF alpha (1000 U/ml) and pentoxifylline (1 mM), cell viability increased to approximately 75% of control (P = 0.001). At concentrations of TNF alpha of 10,000 U/ml, cell viability which was 11% of control with TNF alpha alone increased to 53% in the presence of pentoxifylline (P = 0.002). TNF alpha at 1000 and 10,000 U/ml concentrations decreased [3H]-thymidine uptake to approximately 5% of control values. Co-incubation with pentoxifylline significantly increased uptake to 13% of control at both TNF alpha concentrations (P = 0.002). Pentoxifylline did not affect the level of type I TNF alpha receptor--ligand cross-link product. However, in TNF alpha receptor binding assays, incubation with pentoxifylline 1 mM for 4 h was associated with an increase in the receptor affinity (control: KD = 0.42 nM vs pentoxifylline-treated: KD = 0.21 nM, P = 0.006), without significant change in number of type I TNF alpha receptors, suggesting that pentoxifylline affects post-receptor signalling events. We have observed that pentoxifylline prevents the TNF alpha-mediated activation of sn-2 arachidonic acid-specific cytosolic phospholipase A2, an important component of the signal transduction pathway of TNF alpha cytotoxicity. Because pentoxifylline does not inhibit all activities mediated by the type I TNF alpha receptor, its selective inhibition of post-receptor signalling may facilitate further study into the mechanisms underlying the diverse effects of TNF alpha.

Elimination of malignant clonogenic T cells from human bone marrow using chemoimmunoseparation with 2'-deoxycoformycin, deoxyadenosine and an immunotoxin

Autologous bone marrow transplantation may contribute to the treatment of several types of lymphoreticular malignancies. Recent studies have suggested that a combination of chemoseparation and immunoseparation may be more effective than either modality alone in eliminating malignant cells from human bone marrow. In this report an immunotoxin has been prepared by conjugating pokeweed antiviral protein (PAP) to the 3A1 murine monoclonal antibody that recognizes a 40 kD (CD7) determinant expressed by most T cell acute lymphoblastic leukemias and a majority of normal mature peripheral T cells. When HSB-2 T lymphoma cells were mixed with normal human bone marrow and incubated with 3A1-PAP and 100 microM chloroquine, approximately 3 logs of clonogenic T cells could be eliminated from a 20-fold excess of bone marrow. Treatment of cell mixtures with 2'deoxycoformycin (2'-dCF) and deoxyadenosine (dAdo) eliminated 2 logs of clonogenic tumor cells. The use of 3A1-PAP and chloroquine with dCF/dAdo was more effective than either single modality, eliminating up to 6 logs of HSB-2 tumor cells in optimal experiments. Anti-tumor activity of the combined treatment extended to T leukemia cells taken directly from patients. Although 3A1-PAP reduced CFU-GM by only 13% and BFU-E by 36%, the addition of 2'-dCF and dAdo was more toxic for normal marrow precursors, further reducing CFU-GM, GEMM and BFU-E as well as preventing recovery of CFU-GM in long-term bone marrow culture.(ABSTRACT TRUNCATED AT 250 WORDS)

A component analysis of biofeedback induced self-control of peripheral (finger) temperature

Most of the research on biofeedback induced peripheral temperature control is open to serious methodological and theoretical criticisms. In the present research investigation, increase in peripheral (finger) temperature was targeted because of the possible therapeutic implications for the treatment of migraine and Raynaud's disease. Two experiments are reported in which the pretest-posttest control group design was employed to test the power of the variables in biofeedback induced self-control of finger temperature, and the necessity for subjects to engage in somatic manoeuvres. Significant increases in within-session and absolute finger temperature occurred in a test for self-control only for those subjects who had undergoing contingent feedback-somatic activity training conditions. It is suggested that future research should examine the role of mediational strategies in biofeedback-temperature training.

An experimental brief course in sexual behaviour and counseling

A brief course in sexual behaviour and counseling was given to a sample of 30 fifth-year medical students from Monash University, as an adjunct to their curriculum in gynaecology. The effectiveness of the course in increasing the student's knowledge of sexual behaviour and ability in sexual counselling, and in reducing anticipated anxiety or embarrassment in sexual discussions, was assessed by precourse and postcourse measures. It was concluded that the course was reasonably successful in achieving these aims and provides a basis for desirable future developments in this area.

Functional relationship of lateral hypothalamus and amygdala in control of eating

Cannulas were stereotactically implanted in the lateral hypothalamus and the ipsilateral amygdaloid cortical nucleus of 7 male albino rats, Wistar strain. After functional checking of the accuracy of implants by adrenergic elicitation of increased food intake, the animals were injected with combinations of noradrenaline, phenoxybenzamine or tolazoline, or placebo under 6 treatment conditions, while food-and water satiated. The elicitation of increased food intake in the satiated rat by adrenergic stimulation of the lateral hypothalamus was confirmed, and it was further found that simultaneous adrenergic stimulation of the amygdaloid cortical nucleus augmented this increase. However, simultaneous anti-adrenergic blockade in the amygdaloid cortical nucleus reduced eating to control level. The lack of response of the amygdaloid cortical nucleus to adrenergic stimulation in the satiated rat, under simultaneous stimulation of the lateral hypothalamus with either placebo or an adrenergic blocker, was also demonstrated. It was concluded that the amygdaloid cortical nucleus has a modulatory influence on eating behavior, which is dependent on the level of activity in the lateral hypothalamus, and further that this modulatory influence is necessary to the behavioral output of the hypothalamic system. This is the same relationship between the hypothalamus and amygdala previously demonstrated in regard to drinking behavior and these results are seen as supporting the behavioral generality of the functional relationships reported.

Cafeteria behavior in the rat after hypothalamic cholinergic and adrenergic stimulation

Norepinephrine, carbachol, or placebo was micro-injected into the perifornical region of the rat hypothalamus, via stereotaxically implanted cannulas. Ingestive behavior was observed in the hour after injection in a cafeteria situation in which water, milk, mash, powdered food, and lab chow were all freely available. After adrenergic stimulation, animals ingested significant amounts of mash only; after cholinergic stimulation, animals ingested significant amounts of water and milk, but water was significantly preferred to milk. These findings are seen as providing further support for the behavioral specificity of direct chemical stimulation of the brain, and as casting serious doubts on the interpretation of milk-ingestion as eating behavior.

Neurohumoral interaction in the rat amygdala after central chemical stimulation

The interactions of chemically induced thirst and hunger with deprivation-induced hunger and thirst, respectively, were studied in the amygdala. The results suggest direct neurohumoral blocking at this locus, rather than mediation through activated circuits.