Proton Based Stereotactic Radiotherapy for Skull Base Patients: Dosimetric Comparison to 4 Modern Radiation Treatment Modalities

PURPOSE/OBJECTIVE(S)

Re-irradiation with ablative doses to a smaller target volume and strict critical structure constraint is a challenge for modern radiation planning and delivery systems. Several advanced radiation treatment techniques can be used for fractionated stereotactic ablative radiosurgery (FSRS) in select patients with unresectable recurrent head and neck tumors. In this study, in order to better understand the dosimetry advantage of each technique, we compare the stereotactic treatment plans of our new small spot size Hitachi proton treatment unit to those of CyberKnife stereotactic radiosurgery (CK), Gamma Knife radiosurgery (GK), volumetric modulated arc therapy (VMAT), and MR Linac radiotherapy (MRL).

MATERIALS/METHODS

Ten FSRS skull base patients treated at our institution using VMAT (n = 5) or GK (n = 5) techniques. Intensity-modulated proton therapy (IMPT) plans were created in Raystation using Monte Carlo dose calculation algorithm. VMAT, CK, GK and MRL plans were generated in RayStation, Accuray Precision, Leksell Gamma Plan, and Monaco treatment planning systems, separately. Planning goals were to achieve the best target coverage of prescribed dose without compromising the critical organs at risk dose volume constraints of the clinical treatment plans. Plans were compared based on percent CTV coverage, Paddick conformity index (PCI), gradient index (GI, V50/V100), dose homogeneity index (HI, (D2-D98)/D50), low dose bath volume (LDBV, ratio of total volume irradiated between 20% and 50% prescription dose and the target volume), beam-on-time (BOT), and mean/maximum doses to brainstems.

RESULTS

The median target volume was 15.5 cm3 (range 1.0 - 36.23 cm3). The prescription was 45 Gy in 5 fractions for VMAT patients, and 21 - 27 Gy in 3 fractions for GK patients. The comparison of the treatment plans of these 5 delivery modalities was shown in table. All techniques achieved comparable CTV coverage. GI was superior for GK plans and outstanding in CK and IMPT plans. IMPT plans were also outstanding in regard to BOT and PCI. Significantly improved HI, LDBV and brainstem mean doses were achieved in IMPT plans. For adjacent brainstem and other OARs, maximum doses were comparable among all techniques.

CONCLUSION

In these five advanced radiation therapy modalities, proton therapy SBRT showed dosimetric advantage over other modalities to spare nearby OARs without sacrifice of target coverage. Further studies are needed to utilize this clinical benefit and investigate plan robustness.

Disease Control and Toxicity Outcomes after Intraoperative HDR Brachytherapy for Neck Recurrences in Patients Previously Irradiated Head and Neck Cancer

PURPOSE/OBJECTIVE(S)

Despite recent advances in local and systemic therapies for head and neck squamous cell carcinomas (HNSCC), the most common types of treatment failure remain local and regional. Patients with HNSCC also have a higher risk of developing secondary head and neck tumors due to a field cancerization phenomenon. Treatment of these recurrences poses a challenge, particularly in patients having previously received full dose external beam radiotherapy (EBRT) to the head and neck region. This study evaluates the clinical outcomes of intraoperative Harrison-Anderson-Mick applicator (HAM) HDR brachytherapy (BT) after salvage neck dissection for neck recurrences in patients previously irradiated for HNSCC.

MATERIALS/METHODS

All patients having received HAM BT for HNSCC neck recurrences at a single institution were identified. Demographic, treatment, disease control and toxicity data were collected retrospectively. Toxicity was graded as per Common Terminology Criteria for Adverse events version 5. The Kaplan Meier method was used to assess overall survival (OS) and ipsilateral regional control (IRC) from the time of HAM BT.

RESULTS

Nineteen patients with regional recurrence of HNSCC were treated with HAM BT Ir-192 between July 2006 and June 2022, with a median follow-up for survival of 51.4 months (range: 2.5-186.7). The median BT dose was 12.5 Gy delivered intraoperatively at 5 mm tissue depth/1 cm from source. Fifteen patients (78.9%) also received postoperative EBRT to a median dose of 46 Gy in 23 fractions and 13 (68.4%) received systemic therapy. Six patients (31.6%) developed ipsilateral neck recurrences (4 who had adjuvant EBRT and 2 who did not), 2 patients had primary site recurrences and 5 patients developed distant metastases. In terms of acute toxicity, 4 patients had grade 3 dysphagia requiring feeding tube (FT) placement and one patient required surgical intervention for wound necrosis. In terms of late toxicity, 2 additional patients required FT placement and 1 was able to have it removed. No grade 4+ late toxicities were noted. The IRC at the site of HAM BT at 1 year was 71.5% and 63.6% at 5 years. The 1-year OS was 81.3% and 5-year OS was 40.9%.

CONCLUSION

Intraoperative HAM BT resulted in favorable rates of IRC with acceptable toxicity in the reirradiation setting for HNSCC.

Re-treatment with radium-223: first experience from an international, open-label, phase I/II study in patients with castration-resistant prostate cancer and bone metastases

Background

Six radium-223 injections at 4-week intervals is indicated for patients with castration-resistant prostate cancer and symptomatic bone metastases. However, patients usually develop disease progression after initial treatment. This prospective phase I/II study assessed re-treatment safety and efficacy of up to six additional radium-223 injections.

Patients and methods

Patients had castration-resistant prostate cancer and bone metastases and six initial radium-223 injections with no on-treatment bone progression; all had subsequent radiologic or clinical progression. Concomitant agents were allowed at investigator discretion, excluding chemotherapy and initiation of new abiraterone or enzalutamide. The primary endpoint was safety; additional exploratory endpoints included time to radiographic bone progression, time to total alkaline phosphatase and prostate-specific antigen progression, radiographic progression-free survival, overall survival, time to first symptomatic skeletal event (SSE), SSE-free survival, and time to pain progression.

Results

Among 44 patients, 29 (66%) received all six re-treatment injections. Median time from end of initial radium-223 treatment was 6 months. Forty-one (93%) reported ≥1 treatment-emergent adverse event. No grade 4–5 hematologic treatment-emergent adverse events occurred. Only one (2%) patient had radiographic bone progression; eight (18%) had radiographic soft tissue tumor progression (three lymph node and five visceral metastases). Median times to total alkaline phosphatase and prostate-specific antigen progression were not reached and 2.2 months, respectively. Median radiographic progression-free survival was 9.9 months (12.8-month maximum follow-up). Five (11%) patients died and eight (18%) experienced first SSEs. Median overall survival, time to first SSE, and SSE-free survival were not reached. Five (14%) of 36 evaluable patients (baseline worst pain score ≤7) had pain progression. After 2 years of follow-up, 28 (64%) patients died, and the median overall survival was 24.4 months.

Conclusions

Re-treatment with a second course of six radium-223 injections after disease progression is well tolerated, with minimal hematologic toxicity and low radiographic bone progression rates in this small study with limited follow-up. Favorable safety and early effects on disease progression indicate that radium-223 re-treatment is feasible and warrants further evaluation in larger prospective trials.

[Proton therapy for head and neck cancers]

The absence of exit dose and the sharp lateral penumbra are key assets for proton therapy, which are responsible for its dosimetric superiority over advanced photon radiotherapy. Dosimetric comparisons have consistently shown a reduction of the integral dose and the dose to organs at risk favouring intensity-modulated proton therapy (IMPT) over intensity-modulated radiotherapy (IMRT). The structures that benefit the most of these dosimetric improvements in head and neck cancers are the anterior oral cavity, the posterior fossa, the visual apparatus and swallowing structures. A number of publications have concluded that these dosimetric differences actually translate into reduced toxicities with IMPT, for example with regards to reduced weight loss or need for feeding tube. Patient survival is usually similar to IMRT series, except in base of skull or sinonasal malignancies, where a survival advantage of IMPT could exist. The goals of the present review is to describe the major characteristics of proton therapy, to analyse the clinical data with regards to head and neck cancer patients, and to highlight the issue of patient selection and physical and biological uncertainties.

Select men benefit from androgen deprivation therapy delivered with salvage radiation therapy after prostatectomy

BACKGROUND

Which men benefit most from adding androgen deprivation therapy (ADT) to salvage radiation therapy (SRT) after prostatectomy has not clearly been defined; therefore, we evaluated the impact of ADT to SRT on failure-free survival (FFS) in men with a rising or persistent PSA after prostatectomy.

METHODS

We identified 332 men who received SRT after prostatectomy from 1987 to 2010. Recursive partitioning analysis (RPA) identified favorable, intermediate and unfavorable groups based on the risk of failure after SRT alone. Kaplan-Meier and log-rank tests compared FFS with and without ADT.

RESULTS

Forty-three percent received SRT alone and 57% received SRT with ADT (median 6.6 months (interquartile range (IQR) 5.8-18.1) ADT). Median SRT dose was 70 Gy (IQR 70-70), and median follow-up after SRT was 6.7 years (IQR 4.5-10.8). On Cox's proportional hazard regression, ADT improved FFS (adjusted hazard ratio 0.60, 95% confidence interval: 0.42-0.86; P=0.006). RPA classified unfavorable disease as negative surgical margins (SMs) and preradiation PSA of ⩾0.5 ng ml^-1. Favorable disease had neither adverse factor, and intermediate disease had one adverse factor. The addition of ADT to SRT improved 5-year FFS for men with unfavorable disease (70.3% vs 23.4%; P<0.001) and intermediate disease (69.8% vs 48.0%; P=0.003), but not for men with favorable disease (81.2% vs 78.0%; P=0.971).

CONCLUSIONS

The addition of ADT to SRT appears to improve FFS for men with a preradiation PSA of ⩾0.5 ng ml^-1 or with negative SM at prostatectomy. Men with involved surgical margins and PSA <0.5 ng ml^-1 appear to be at a lower risk of failure after SRT alone and may not derive as much benefit from the administration of ADT with SRT. These results are hypothesis-generating only, and further prospective data are required to see if ADT can safely be omitted in this select group of men.

American Brachytherapy Society Task Group Report: Use of androgen deprivation therapy with prostate brachytherapy-A systematic literature review

PURPOSE

Prostate brachytherapy (PB) has well-documented excellent long-term outcomes in all risk groups. There are significant uncertainties regarding the role of androgen deprivation therapy (ADT) with brachytherapy. The purpose of this report was to review systemically the published literature and summarize present knowledge regarding the impact of ADT on biochemical progression-free survival (bPFS), cause-specific survival (CSS), and overall survival (OS).

METHODS AND MATERIALS

A literature search was conducted in Medline and Embase covering the years 1996-2016. Selected were articles with >100 patients, minimum followup 3 years, defined risk stratification, and directly examining the role and impact of ADT on bPFS, CSS, and OS. The studies were grouped to reflect disease risk stratification. We also reviewed the impact of ADT on OS, cardiovascular morbidity, mortality, and on-going brachytherapy randomized controlled trials (RCTs).

RESULTS

Fifty-two selected studies (43,303 patients) were included in this review; 7 high-dose rate and 45 low-dose rate; 25 studies were multi-institutional and 27 single institution (retrospective review or prospective data collection) and 2 were RCTs. The studies were heterogeneous in patient population, risk categories, risk factors, followup time, and treatment administered, including ADT administration and duration (median, 3-12 months);71% of the studies reported a lack of benefit, whereas 28% showed improvement in bPFS with addition of ADT to PB. The lack of benefit was seen in low-risk and favorable intermediate-risk (IR) disease and most high-dose rate studies. A bPFS benefit of up to 15% was seen with ADT use in patients with suboptimal dosimetry, those with multiple adverse risk factors (unfavorable IR [uIR]), and most high-risk (HR) studies. Four studies reported very small benefit to CSS (2%). None of the studies showed OS advantage; however, three studies reported an absolute 5-20% OS detriment with ADT. Literature suggests that OS detriment is more likely in older patients or those with pre-existing cardiovascular disease. Four RCTs with an adequate number of patients and well-defined risk stratification are in progress. One RCT will answer the question regarding the role of ADT with PB in favorable IR patients and the other three RCTs will focus on optimal duration of ADT in the uIR and favorable HR population.

CONCLUSIONS

Patients treated with brachytherapy have excellent long-term disease outcomes. Existing evidence shows no benefit of adding ADT to PB in low-risk and favorable IR patients. UIR and HR patients and those with suboptimal dosimetry may have up to 15% improvement in bPFS with addition of 3-12 months of ADT, with uncertain impact on CSS and a potential detriment on OS. To minimize morbidity, one should exercise caution in prescribing ADT together with PB, in particular to older men and those with existing cardiovascular disease. Due to the retrospective nature of this evidence, significant selection, and treatment bias, no definitive conclusions are possible. RCT is urgently needed to define the potential role and optimal duration of ADT in uIR and favorable HR disease.

Addition of short-term androgen deprivation therapy to dose-escalated radiation therapy improves failure-free survival for select men with intermediate-risk prostate cancer

BACKGROUND

Dose-escalated (DE) radiation therapy (RT) and androgen deprivation therapy (ADT) improve prostate cancer outcomes over standard-dose RT. The benefit of adding ADT to DE-RT for men with intermediate-risk prostate cancer (IR-PrCa) is uncertain.

PATIENTS AND METHODS

We identified 636 men treated for IR-PrCa with DE-RT (>75Gy). The adult comorbidity evaluation-27 index classifed comorbidity. Kaplan-Meier and log-rank tests compared failure-free survival (FFS) with and without ADT.

RESULTS

Forty-five percent received DE-RT and 55% DE-RT with ADT (median 6 months). On Cox proportional hazard regression that adjusted for comorbidity and tumor characteristics, ADT improved FFS (adjusted hazard ratio 0.36; P = 0.004). Recursive partitioning analysis of men without ADT classified Gleason 4 + 3 = 7 or ≥50% positive cores as unfavorable disease. The addition of ADT to DE-RT improved 5-year FFS for men with unfavorable disease (81.6% versus 92.9%; P = 0.009) but did not improve FFS for men with favorable disease (96.3% versus 97.4%; P = 0.874). When stratified by comorbidity, ADT improved FFS for men with unfavorable disease and no or mild comorbidity (P = 0.006) but did not improve FFS for men with unfavorable disease and moderate or severe comorbidity (P = 0.380).

CONCLUSION

The addition of ADT to DE-RT improves FFS for men with unfavorable IR-PrCa, especially those with no or minimal comorbidity.

Prostate cancer–specific mortality after definitive radiation therapy: Who dies of disease?

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Background: A competing risks analysis was undertaken to identify patient subgroups at greatest risk of dying from prostate cancer (CAP) after treatment with definitive external beam radiation therapy (RT) +/− androgen deprivation therapy (ADT) in the PSA era, and to determine which factors predict for survival from disease.

Methods: A total of 2,675 men with localized CAP treated with RT +/− ADT at M. D. Anderson Cancer Center from 1987-2007 were evaluated. Prostate cancer-specific mortality (PCSM) and other cause mortality rates were calculated after stratifying patients according to NCCN risk group, RT dose, use of ADT, and age at treatment. In total, 21% had low-risk, 40% had intermediate-risk, and 39% had high-risk disease. Multivariate analysis (MVA) was performed using Cox regression modeling.

Results: Median age was 68.5 years and median follow-up was 6.4 years. For patients with low-risk disease, only 0.2% died of CAP 10 years after treatment. None of the low-risk patients <70 years old who received ≥72 Gy died of CAP. The majority of deaths in the intermediate-risk group were also due to other causes; men ≥70 years old who received <72 Gy had the highest 10-year PCSM (5%). High-risk patients <70 years old who received <72 Gy without ADT had similar 10-year rates of CAP (15.2%) and non-CAP (18.5%) mortality. Men with high-risk disease <70 years old treated with higher doses >72 Gy were twice as likely to die from non-CAP causes (15.9%) than die from CAP (8.6%). In older men ≥70 years old with high risk disease, dose-escalation with ADT reduced 10-year PCSM from 14% to 4%, and most deaths were due to other causes (41% and 20%). On MVA, dose (p=0.002), ADT (p=0.007), PSA (p<0.0001) and Gleason score (p<0.0001) were predictive of PCSM in the high-risk group.

Conclusions: Men with low- and intermediate-risk CAP treated with definitive RT are unlikely to die of disease. PCSM is higher in men with high-risk disease but can be reduced with dose escalation and ADT, although patients are still twice as likely to die of other causes.

No significant financial relationships to disclose.

Phase I evaluation of vandetanib with radiation therapy (RT) ± cisplatin in previously untreated advanced head and neck squamous cell carcinoma (HNSCC)

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Background: Vandetanib is a once-daily oral anticancer agent that selectively targets VEGF, EGF and RET receptor tyrosine kinases. We report preliminary results from an ongoing open-label phase I study of vandetanib with RT ± cisplatin in patients (pts) with previously untreated, unresected, locally advanced (stage III-IV) HNSCC. Methods: Eligible pts received once-daily vandetanib for 14 days followed by either 1) concomitant vandetanib + RT (2 Gy/d, 5 d/wk; total 70 Gy) + cisplatin (30 mg/m2, 2 h iv infusion/wk) for 7 wks, or 2) concomitant vandetanib + RT (2.2 Gy/d accelerated fractionation, 5 d/wk; total 66 Gy) for 6 wks. The primary objective was to determine the safety, tolerability and maximum tolerated dose (MTD) of vandetanib in both regimens. The first pt cohort received vandetanib 100 mg/day; escalation to 200 mg and 300 mg in subsequent cohorts was permitted providing <2/6 (33%) pts in the preceding cohort experienced a dose-limiting toxicity (DLT). Cohort expansion at the MTD of vandetanib was also planned. Results: As of Dec 1 2008, 24 pts (median age 53.5 yrs; 19 male; all M0) had received treatment with vandetanib + RT + cisplatin (n=18) or vandetanib + RT (n=6). In the triplet arm, no DLTs occurred in the initial vandetanib 100 mg cohort (n=6); an additional 6 pts were enrolled to receive vandetanib 200 mg but this dose was considered to exceed the MTD since DLTs were reported in 3/5 evaluable pts (Table). Vandetanib 100 mg was therefore declared the MTD with RT + cisplatin and cohort expansion at this dose continues. In regimen 2), 6 pts have received vandetanib 100 mg + RT and evaluation of this initial cohort is ongoing. Conclusions: This study, which continues to recruit, is the first to evaluate dual targeting of VEGFR/EGFR tyrosine kinases with chemoradiation or radiation alone in HNSCC pts. Among the 24 treated pts, 2 have completed the 2-year follow up, 1 death occurred that was causally related to cisplatin, and 21 remain in follow up or continue to receive treatment.

[Table: see text]

[Table: see text]

Effect of nutrition on the GH responsiveness of liver and adipose tissue in dairy cows

Dairy cows enter a period of energy insufficiency after parturition. In liver, this energy deficit leads to reduced expression of the liver-specific GH receptor transcript (GHR1A) and decreased GHR abundance. As a consequence, hepatic processes stimulated by GH, such as IGF-I production, are reduced. In contrast, adipose tissue has been assumed to remain fully GH responsive in early lactation. To determine whether energy insufficiency causes contrasting changes in the GH responsiveness of liver and adipose tissue, six lactating dairy cows were treated for 4 days with saline or bovine GH when adequately fed (AF, 120% of total energy requirement) or underfed (UF, 30% of maintenance energy requirement). AF cows mounted robust GH responses in liver (plasma IGF-I and IGF-I mRNA) and adipose tissue (epinephrine-stimulated release of non-esterified fatty acids in plasma, IGF-I mRNA, and p85 regulatory subunit of phosphatidylinositol 3-kinase mRNA). Reductions of these responses were seen in the liver and adipose tissue of UF cows and were associated with decreased GHR abundance. Reduced GHR abundance occurred without corresponding reductions of GHR1A transcripts in liver or total GHR transcripts in adipose tissue. In contrast, undernutrition did not alter the abundance of proteins involved in the early post-receptor signaling steps. Thus, a feed restriction reproducing the energy deficit of early lactation depresses GH actions not only in liver but also in adipose tissue. It remains unknown whether a similar reduction of GH action occurs in the adipose tissue of early lactating dairy cows.

Tumour necrosis factor alpha blockade induces an anti-inflammatory growth hormone signalling pathway in experimental colitis

BACKGROUND

Neutralisation of tumour necrosis factor alpha (TNFalpha) restores systemic growth hormone function in patients with Crohn's disease, and induces mucosal healing. Anabolic effects of growth hormone depend on activation of the STAT5 transcription factor. Although it has recently been reported that both administration of growth hormone and neutralisation of TNFalpha reduce mucosal inflammation in experimental colitis, whether this involved activation of STAT5 in the gut is not known.

AIM

To determine whether TNFalpha blockade in colitis up regulates a growth hormone:STAT5 signalling pathway in the colon.

METHODS

Interleukin 10-deficient mice and wild-type controls received growth hormone or anti-TNFalpha antibody, and T84 human colon carcinoma cells were treated with TNFalpha or growth hormone. Activation and expression of STAT5b, peroxisome proliferator-activated receptor gamma (PPARgamma), NFkappaB/IkappaB and growth hormone receptor were determined.

RESULTS

Growth hormone activated STAT5b and up regulated expression of PPARgamma in normal mouse colon; inflamed colon was partially resistant to this. Chronic administration of growth hormone, nevertheless, significantly reduced activation of colonic NFkappaB (p = 0.028). Neutralisation of TNFalpha rapidly increased abundance of growth hormone receptor, activation of STAT5 and abundance of PPARgamma in the colon, but reduced activation of NFkappaB in colitis. Growth hormone activated STAT5, and directly reduced TNFalpha activation of NFkappaB, in T84 cells.

CONCLUSIONS

Reduced activation of colonic STAT5 and expression of PPARgamma may contribute to persistent mucosal inflammation in colitis. Up regulation of STAT5 and PPARgamma, either through neutralisation of TNFalpha or chronic administration of growth hormone, may exert an anti-inflammatory effect in inflammatory bowel disease.

Prolactin modulates phosphorylation, signaling and trafficking of epidermal growth factor receptor in human T47D breast cancer cells

Prolactin (PRL) is a polypeptide hormone produced by the anterior pituitary gland and other sites that acts both systemically and locally to cause lactation and other biological effects by interacting with the PRL receptor, a Janus kinase (JAK)2-coupled cytokine receptor family member, and activating downstream signal pathways. Recent evidence suggests PRL is a player in the pathogenesis and progression of breast cancer. Epidermal growth factor (EGF) also has effects on breast tissue, working through its receptors, epidermal growth factor receptor (EGFR) and ErbB-2 (c-neu, HER2), both intrinsic tyrosine kinase growth factor receptors. EGFR promotes pubertal breast ductal morphogenesis in mice, and both EGFR and ErbB-2 are relevant in pathogenesis and behavior of breast and other human cancers. Previous studies showed that PRL and EGF synergize to enhance motility in the human breast cancer cell line, T47D. In this study, we explored crosstalk between the PRL and EGF signaling pathways in T47D cells, with an ultimate aim of understanding how these two important factors might work together in vivo to affect breast cancer behavior. Both PRL and EGF caused robust signaling in T47D cells; PRL acutely activated JAK2, signal transducer and activator of transcription-5 (STAT5), and extracellular signal-regulated kinase-1 and -2 (ERK1 and ERK2), whereas EGF caused EGFR activation and consequent src homology collagen (SHC) activation and ERK activation. Notably, PRL also caused phosphorylation of the EGFR and ErbB-2 at sites detected by PTP101, an antibody that recognizes threonine phosphorylation at consensus motifs for ERK-induced phosphorylation. PRL-induced PTP101-reactive phosphorylation was prevented by pretreatment with PD98059, an ERK pathway inhibitor. Furthermore, PRL synergized with EGF in activating SHC and ERK and transactivating a luciferase reporter driven by c-fos gene enhancer elements, suggesting that PRL allowed markedly enhanced EGF signaling. This was accompanied by substantial inhibition of EGF-induced EGFR downregulation when PRL and EGF cotreatment was compared to EGF treatment alone. This effect of PRL was abrogated by ERK pathway inhibitor pretreatment. Our data suggest that PRL synergistically augments EGF signaling in T47D breast cancer cells at least in part by lessening EGF-induced EGFR downregulation and that this effect requires PRL-induced ERK activity and threonine phosphorylation of EGFR.

Effects of chronic ethanol on hepatic and renal CYP2C11 in the male rat: interactions with the Janus-kinase 2-signal transducer and activators of transcription proteins 5b pathway

Chronic alcohol intake in male rats results in: 1) demasculinization of the GH pulse pattern; 2) reduced serum testosterone concentrations; and 3) decreased expression hepatic CYP2C11. Hepatic CYP2C11 expression is regulated by the male pattern of GH through the Janus-kinase/signal transducer and activators of transcription proteins (JAK/STAT) signal transduction pathway in the male rat. Renal CYP2C11 is regulated by testosterone, not GH. The involvement of the JAK/STAT5b signal transduction pathway in renal CYP2C11 signaling has not been studied. We tested the hypothesis that ethanol reduces CYP2C11 levels by interfering with the JAK/STAT5b pathway. Using a total enteral nutrition (TEN) model to feed rats a well-balanced diet, we have studied the effects of chronic ethanol intake (21 d) on hepatic and renal JAK/STAT pathway of adult male rats (8-10/group). We found decreased hepatic and renal expression of CYP2C11 in ethanol-fed rats with concomitant decreases in STAT5b and phospho-STAT5b, decreased in vitro hepatic STAT5b binding to a CYP2C11 promoter element and no effects on hepatic GHR levels. Ethanol caused tissue specific effects in phospho-JAK2 and JAK2, with increased levels in the liver, but decreased JAK2 expression in the kidney. We conclude that ethanol suppression of CYP2C11 expression is clearly associated with reductions in STAT5b levels, but not necessarily in reductions of JAK2 levels. The mechanisms underlying ethanol-induced suppression of STAT5b is yet to be determined, as is the question of whether this is secondary to hormonal effects or a direct ethanol effect.

Metalloproteinases and the modulation of GH signaling

The metzincin metalloproteinase, tumor necrosis factor-alpha-converting enzyme (TACE), also known as ADAM (a disintegrin and metalloproteinase) 17, has recently been identified as an important enzyme for cleavage of the GH receptor (GHR) and shedding of GH-binding protein (GHBP). Proteolysis can be induced by phorbol esters, platelet-derived growth factor and serum; it is dependent on protein kinase C and partially on MAP kinase pathways. Proteolysis occurs at the cell surface, leading to extracellular release of GHBP and intracellular GHR remnant accumulation. The GHR remnant is further processed by gamma-secretase activity, possibly leading to biologically active products. TACE-dependent GHR proteolysis can be inhibited by GH as the dimerized GHR is resistant to cleavage. The cleavage site lies within a short juxtamembranous stem region that extends between the transmembrane helix and the globular dimerization domain of the GHR. GHR proteolysis leads to downregulation of functional GHRs at the cell surface, and has complex secondary effects on GH action via GHBP and GHR remnant generation.

Growth hormone signalling and its regulation: preventing too much of a good thing

Growth hormone (GH) is a major growth-promoting and metabolic regulatory hormone. Interaction of GH with its cell surface GH receptor (GHR), by virtue of receptor dimerization, causes activation of the GHR-associated cytoplasmic tyrosine kinase, JAK2. Several signalling pathways, including the STAT5, PI3 kinase and MAP kinase pathways, are thereby accessed, resulting in various biochemical and biological cellular signalling outcomes which are rapidly becoming deciphered. Various mechanisms probably exist to terminate, modulate and prevent GH signalling. Some of these mechanisms regulate receptor abundance and/or availability while others may alter the responsiveness of downstream signalling molecules to receptor engagement. In this review, recent insights into modulation of GH signalling are discussed. Special emphasis is placed on mechanisms of homologous and heterologous desensitization and on the likelihood that inducible GHR proteolysis, in addition to causing GH binding protein generation, may also serve as an important mechanism of heterologous GHR downregulation.

Growth hormone (GH)-induced dimerization inhibits phorbol ester-stimulated GH receptor proteolysis

Growth hormone (GH) initiates its cellular action by properly dimerizing GH receptor (GHR). A substantial fraction of circulating GH is complexed with a high-affinity GH-binding protein (GHBP) that in many species can be generated by GHR proteolysis and shedding of the receptor's ligand-binding extracellular domain. We previously showed that this proteolysis 1) can be acutely promoted by the phorbol ester phorbol 12-myristate 13-acetate (PMA), 2) requires a metalloprotease activity, 3) generates both shed GHBP and a membrane-associated GHR transmembrane/cytoplasmic domain remnant, and 4) results in down-regulation of GHR abundance and GH signaling. Using cell culture model systems, we now explore the effects of GH treatment on inducible GHR proteolysis and GHBP shedding. In human IM-9 lymphocytes, which endogenously express GHRs, and in Chinese hamster ovary cells heterologously expressing wild-type or cytoplasmic domain internal deletion mutant rabbit GHRs, brief exposure to GH inhibited PMA-induced GHR proteolysis (receptor loss and remnant accumulation) by 60-93%. PMA-induced shedding of GHBP from Chinese hamster ovary transfectants was also inhibited by 70% in the presence of GH. The capacity of GH to inhibit inducible GHR cleavage did not rely on JAK2-dependent GH signaling, as evidenced by its continued protection in JAK2-deficient gamma2A rabbit GHR cells. The GH concentration dependence for inhibition of PMA-induced GHR proteolysis paralleled that for its promotion of receptor dimerization (as monitored by formation of GHR disulfide linkage). Unlike GH, the GH antagonist, G120K, which binds to but fails to properly dimerize GHRs, alone did not protect against PMA-induced GHR proteolysis; G120K did, however, antagonize the protective effect of GH. Our data suggest that GH inhibits PMA-induced GHR proteolysis and GHBP shedding by inducing GHR dimerization and that this effect does not appear to be related to GH site 1 binding, GHR internalization, or GHR signaling. The implications of these findings with regard to GH signaling and GHR down-regulation are discussed.

Demonstration of direct effects of growth hormone on neonatal cardiomyocytes

The cellular and molecular basis of growth hormone (GH) actions on the heart remain poorly defined, and it is unclear whether GH effects on the myocardium are direct or mediated at least in part via insulin-like growth factor (IGF-1). Here, we demonstrate that the cultured neonatal cardiomyocyte is not an appropriate model to study the effects of GH because of artifactual loss of GH receptors (GHRs). To circumvent this problem, rat neonatal cardiomyocytes were infected with a recombinant adenovirus expressing the murine GHR. Functional integrity of GHR was suggested by GH-induced activation of the cognate JAK2/STAT5, MAPK, and Akt intracellular pathways in the cells expressing GHR. Although exposure to GH resulted in a significant increase in the size of the cardiomyocyte and increased expression of c-fos, myosin light chain 2, and skeletal alpha-actin mRNAs, there were no significant changes in IGF-1 or atrial natriuretic factor mRNA levels in response to GH stimulation. In this model, GH increased incorporation of leucine, uptake of palmitic acid, and abundance of fatty acid transport protein mRNA. In contrast, GH decreased uptake of 2-deoxy-d-glucose and levels of Glut1 protein. Thus, in isolated rat neonatal cardiomyocytes expressing GHR, GH induces hypertrophy and causes alterations in cellular metabolic profile in the absence of demonstrable changes in IGF-1 mRNA, suggesting that these effects may be independent of IGF-1.

Pulmonary hypoplasia in mice lacking tumor necrosis factor-alpha converting enzyme indicates an indispensable role for cell surface protein shedding during embryonic lung branching morphogenesis

Many membrane-bound protein precursors, including cytokines and growth factors, are proteolytically shed to yield soluble intercellular regulatory ligands. The responsible protease, tumor necrosis factor-alpha converting enzyme (TACE/ADAM-17), is a transmembrane metalloprotease-disintegrin that cleaves multiple cell surface proteins, although it was initially identified for the enzymatic release of tumor necrosis factor-alpha (TNF-alpha). Mammalian lung growth and development are tightly controlled by cytokines and peptide growth factors. However, the biological function of the cell shedding mechanism during lung organogenesis is not understood. We therefore evaluated the role of TACE as a "sheddase" during lung morphogenesis by analyzing the developmental phenotypes of lungs in mice with an inactive TACE gene in both in vivo and ex vivo organ explant culture. Neonatal TACE-deficient mice had visible respiratory distress and their lungs failed to form normal saccular structures. These newborn mutant lungs had fewer peripheral epithelial sacs with deficient septation and thick-walled mesenchyme, resulting in reduced surface for gas exchange. At the canalicular stage of E16.5, the lungs of TACE mutant mice were impaired in branching morphogenesis, inhibited in epithelial cell proliferation and differentiation, and delayed in vasculogenesis. Embryonic TACE knockout mouse lungs (E12) branched poorly compared to wild-type lungs, when placed into serumless organ culture. Gene expression of both surfactant protein-C and aquaporin-5 were inhibited in cultured TACE-mutant embryonic lungs, indicating defects in both branching and peripheral epithelial cytodifferentiation in the absence of TACE protein. Furthermore, both the hypoplastic phenotype and the delayed cytodifferentiation in TACE-deficient lungs were rescued by exogenous addition of soluble stimulatory factors including either TNF-alpha or epidermal growth factor in embryonic lung culture. Thus, the impaired lung branching and maturation without TACE suggest a broad role for TACE in the processing of multiple membrane-anchored proteins, one or more of which is essential for normal lung morphogenesis. Taken together, our data indicate that the TACE-mediated proteolytic mechanism which enzymatically releases membrane-tethered proteins plays an indispensable role in lung morphogenesis, and its inactivation leads to abnormal lung development.

The angiotensin II-dependent nuclear translocation of Stat1 is mediated by the Jak2 protein motif 231YRFRR

In response to angiotensin II, Jak2 autophosphorylates and binds the angiotensin II AT(1) receptor. By studying a variety of Jak2 deletion proteins, we now show that the Jak2 protein motif (231)YRFRR is required for the co-association of this kinase with the AT(1) receptor. We also used a full-length Jak2 protein containing a (231)FAAAA amino acid substitution. Although this protein still autophosphorylated in response to angiotensin II, it did not co-associate with the AT(1) receptor. This uncoupling indicates that AT(1)/Jak2 co-association is not necessary for angiotensin II-induced Jak2 autophosphorylation and that Jak2 autophosphorylation per se is insufficient for AT(1) receptor co-association. In response to angiotensin II, the Jak2-(231)FAAAA mutant will tyrosine phosphorylate Stat1. However, in the absence of AT(1)/Jak2 co-association, Stat1 did not translocate into the cell nucleus and failed to mediate gene transcription. This notable result indicates that Stat1 tyrosine phosphorylation alone is insufficient for Stat1 nuclear translocation. In summary, we now show that, although Jak2-mediated tyrosine phosphorylation of Stat1 is independent of receptor co-association, Jak2-mediated recruitment of Stat1 to the AT(1) receptor is critical for Stat1 nuclear translocation and subsequent gene transcription.

Constitutive alpha-secretase cleavage of the beta-amyloid precursor protein in the furin-deficient LoVo cell line: involvement of the pro-hormone convertase 7 and the disintegrin metalloprotease ADAM10

The beta-amyloid precursor protein (betaAPP) undergoes a physiological cleavage triggered by one or several proteolytic activities referred to as alpha-secretases, leading to the secretion of sAPPalpha. Several lines of evidence indicate that the alpha-secretase cleavage is a highly regulated process. Thus, besides constitutive production of sAPPalpha, several studies have reported on protein kinase C-regulated sAPPalpha secretion. Studies aimed at identifying alpha-secretase(s) candidates suggest the involvement of enzymes belonging to the pro-hormone convertases and disintegrin families. The delineation of respective contributions of proteolytic activities in constitutive and regulated sAPPalpha secretion is rendered difficult by the fact that the overall regulated response always includes the basal constitutive counterpart that cannot be selectively abolished. Here we report on the fact that the furin-deficient LoVo cells are devoid of regulated PKC-dependent sAPPalpha secretion and therefore represent an interesting model to study exclusively the constitutive sAPPalpha secretion. We show here, by a pharmacological approach using selective inhibitors, that pro-hormone convertases and proteases of the ADAM (disintegrin metalloproteases) family participate in the production/secretion of sAPPalphas in LoVo cells. Transfection analysis allowed us to further establish that the pro-hormone convertase 7 and ADAM10 but not ADAM17 (TACE, tumour necrosis factor alpha-converting enzyme) likely contribute to constitutive sAPPalpha secretion by LoVo cells.

Phorbol ester- and growth factor-induced growth hormone (GH) receptor proteolysis and GH-binding protein shedding: relationship to GH receptor down-regulation

GH signals by interacting with GH receptor (GHR). A substantial fraction of circulating GH complexes with GH-binding protein (GHBP), which corresponds to the GHR extracellular domain. GHBP is generated by 1) alternative splicing of a common GHR precursor messenger RNA to encode secreted GHBP (the source of the vast majority of GHBP in rodents); and 2) proteolysis of the cell-associated GHR with shedding of GHBP (a mechanism operative in rabbits and humans). We previously observed that phorbol ester (PMA)-induced activation of protein kinase C (PKC) causes metalloprotease-mediated GHR proteolysis and GHBP shedding in human IM-9 lymphocytes. We now demonstrate that PMA-induced hydroxamate (IC3)-inhibitable GHR proteolysis and GHBP shedding were also detected in murine 3T3-F442A and 3T3-L1 preadipocytes and in Chinese hamster ovary (CHO) cells stably expressing rabbit GHR (rbGHR), although the degree of GHBP shedding was much smaller for murine GHR than for rabbit or human GHRs. PMA-induced GHR proteolysis in 3T3-F442A, 3T3-L1, and CHO-rbGHR cells was significantly reduced by pretreatment with mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1 inhibitors, suggesting involvement of the mitogen-activated protein kinase pathway in regulating this PKC-dependent effect. In contrast, GHR proteolysis promoted by N-ethylmaleimide, although inhibited by IC3, was unaffected by inhibition of either PKC or mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1. Thus, different pathways leading to metalloprotease-mediated receptor proteolysis are accessed by PMA vs. N-ethylmaleimide. To determine whether other, possibly more physiologically relevant, stimuli induce GHR proteolysis, we tested effects of platelet-derived growth factor (PDGF) and serum. Treatment of serum-deprived cells with PDGF (in 3T3-F442A cells) or serum (in 3T3-F442A and CHO-rbGHR cells) promoted GHR proteolysis, which was inhibited by IC3. Interestingly, PMA-, PDGF-, and serum-induced GHR proteolysis was associated with substantial decreases in GH-induced activation of Janus kinase-2, which were also prevented by IC3. These findings suggest that inducible metalloprotease-mediated GHR proteolysis constitutes an important mechanism of receptor down-regulation and modulation of GH signaling.

Src homology 3 domain-dependent interaction of Nck-2 with insulin receptor substrate-1

Insulin receptor substrate-1 (IRS-1) is a multi-domain protein that mediates signal transduction from receptors for insulin and other growth factors to a variety of downstream molecules through both tyrosine-phosphorylation-dependent and -independent interactions. While the tyrosine-phosphorylation-dependent interactions mediated by IRS-1 have been well characterized, the molecular basis underlying the tyrosine-phosphorylation-independent IRS-1 interactions is largely unknown. We previously detected, in an in vitro binding assay, interactions of Nck-2 Src homology (SH) 3 domains with IRS-1. We show here that IRS-1 associates with Nck-2 in vivo. Additionally, we have investigated the molecular basis underlying the IRS-1-Nck-2 complex formation. We have found that (i) mutations at the highly conserved tryptophan within the Nck-2 SH3 domains markedly reduced the association with IRS-1, (ii) interactions mediated by multiple SH3 domains enhance the complex formation of Nck-2 with IRS-1, (iii) deletion of either the phosphotyrosine-binding/Shc and IRS-1 NPXY-binding (PTB/SAIN) domains or the Pre-C-terminal domain of IRS-1, but not the pleckstrin homology (PH) domain, reduced the Nck-2 binding, (iv) PTB/SAIN domains or the Pre-C-terminal domain alone is capable of interacting with Nck-2, and (v) the IRS-1-Nck-2 interaction occurs in the absence of other proteins and therefore is direct. These results establish that IRS-1 is a bona fide target of the Nck-2 SH3 domains and reveal that IRS-1 forms a complex with Nck-2 via direct interactions mediated by multiple domains from both binding partners.

Tumor necrosis factor-alpha converting enzyme (TACE) is a growth hormone binding protein (GHBP) sheddase: the metalloprotease TACE/ADAM-17 is critical for (PMA-induced) GH receptor proteolysis and GHBP generation

The GH binding protein (GHBP), which exists in many vertebrates, is a circulating high affinity binding protein corresponding to the extracellular domain of the GH receptor (GHR). In humans, rabbits, and several other species, the GHBP is generated by proteolysis of the GHR and shedding of its extracellular domain. We previously showed that GHBP shedding is inducible by the phorbol ester phorbol 12-myristate,13-acetate (PMA) and inhibited by the metalloprotease inhibitor, Immunex Corp. Compound 3 (IC3). The metzincin metalloprotease, tumor necrosis factor-alpha (TNF-alpha)-converting enzyme (TACE), catalyzes the shedding of TNF-alpha from its transmembrane precursor, a process that is also inhibitable by IC3. TACE may hence be a candidate for GHBP sheddase. In this study, we reconstitute fibroblasts derived from a TACE knockout mouse (Null cells) with either the rabbit (rb) GHR alone (Null/R) or rbGHR plus murine TACE (Null/R+T). Although GHR in both cells was expressed at similar abundance, dimerized normally and caused JAK2 activation in response to GH independent of TACE expression, PMA was unable to generate GHBP from Null/R cells. In contrast, PMA caused ample GHBP generation from TACE reconstituted (Null/R + T) cells, and this GHBP shedding was substantially inhibited by IC3 pretreatment. Corresponding to the induced shedding of GHBP from Null/R + T cells, PMA treatment caused a significant loss of immunoblottable GHR in Null/R+T, but not in Null/R cells. We conclude that TACE is an enzyme required for PMA-induced GHBP shedding and that PMA-induced down-regulation of GHR abundance may in significant measure be attributable to TACE-mediated GHR proteolysis.

Initial validation of the functional impairment scale for children and adolescents

OBJECTIVE

Two studies assessed the validity of the Functional Impairment Scale for Children and Adolescents (FISCA), a multidimensional parent-report questionnaire.

METHOD

In study 1, quasi-exploratory and confirmatory procedures tested whether FISCA data for 804 inpatients (mean age = 13.4, 456 boys), collected October 1994 through December 1995, fit a 3-factor model. Study 2 (n = 330) used survival and discriminant analyses to predict recidivism status at 3 and 6 months follow-up from FISCA scores at intake.

RESULTS

The 8 FISCA scales reduced to 3 factors describing undercontrolled aggression, social role violations, and self-focused aspects of child functional impairment. Serious impairment on the Aggression and School scales each predicted a 3-fold increase in recidivism risk. Together, impairment scores for Aggression, School, Thinking, and Delinquency correctly identified 73% of the recidivists. However, 51% of the nonrecidivists also were classified as recidivists.

CONCLUSIONS

Although these data initially support the FISCA's validity, they underscore the need for more effective strategies to identify severely impaired children whose problems will be sporadic or short-lived.

Insulin receptor substrate-1-mediated enhancement of growth hormone-induced mitogen-activated protein kinase activation

Interaction of GH with the cell-surface GH receptor (GHR) causes activation of the GHR-associated tyrosine kinase, JAK2, and consequent triggering of signaling cascades including the STAT, Ras/Raf/MEK1/MAP kinase, and insulin receptor substrate-1(IRS-1)/PI3kinase pathways. We previously showed that IRS- and GHR-deficient 32D cells that stably express the rabbit GHR and rat IRS-1 (32D-rbGHR-IRS-1) exhibited markedly enhanced GH-induced proliferation and MAP kinase (ERK1 and ERK2) activation compared with cells expressing only the GHR (32D-rbGHR). We now examine biochemical mechanism(s) by which IRS-1 augments GH-induced MAP kinase activation. Time-course experiments revealed a similarly transient (maximal at 15 min) GH-induced ERK1 and ERK2 activation in both 32D-rbGHR and 32D-rbGHR-IRS-1 cells, but, consistent with our prior findings, substantially greater activation was seen in the IRS-1-containing cells. In both cells, GH-induced MAP kinase activation was markedly blunted by the MEK1 inhibitor, PD98059, but not by the PKC inhibitor, GF109203X. Interestingly, pretreatment with the PI3K inhibitor, wortmannin (EC50 approximately 10 nM), significantly reduced GH-induced MAP kinase activation in both 32D-rbGHR and 32D-rbGHR-IRS-1 cells. This same pattern in both cells of IRS-1-dependent augmentation and IRS-1-independent wortmannin sensitivity was also observed for GH-induced activation of Akt and MEK1 (using state-specific antibody blotting for both), despite the lack of difference in GHR, JAK2, SHP-2, p85, Akt, Ras, Raf-1, MEK1, ERK1, or ERK2 abundance between the two cells. A different PI3K inhibitor, LY294002 (50 microM), substantially inhibited (roughly 72%) GH-induced MAP kinase activation in 32D-rbGHR-IRS-1 cells, but only marginally (and statistically insignificantly) inhibited GH-induced MAP kinase activation in 32D-rbGHR cells. Because GH-induced Akt activation was completely inhibited in both cells by the same concentration of LY294002, these findings indicate that the wortmannin sensitivity of both the IRS-1-independent and -dependent GH-induced MAP kinase activation may reflect the activity of another wortmannin-sensitive target(s) in addition to PI3K in mediation of GH-induced MAP kinase activation in these cells. Notably, GH-induced STAT5 tyrosine phosphorylation, unlike Akt or MAPK activation, did not differ between the cells. Finally, while GH promoted accumulation of activated Ras in both cells, both basal and GH-induced activated Ras levels were greater in cells expressing IRS-1 than in 32D-rbGHR cells. These data indicate that while GH induces tyrosine phosphorylation of STAT5 and activation of the Ras/Raf/MEK1/MAPK and PI3K pathways, IRS-1 expression augments the latter two more than the former.

Structural, relative, and absolute agreement between parents' and adolescent inpatients' reports of adolescent functional impairment

This study assessed agreement between parents' and adolescent inpatients' scores on caretaker and self-report versions of the Functional Impairment Scale for Children and Adolescents (FISCA and FISCA-SR). Self-report data describing impairment in eight domains were collected from 375 inpatients (M age = 15.0 years, 55% females), with parent data available for 233 (62%). Confirmatory factor analysis demonstrated structural congruence between a hypothesized, three-factor model, based on a prior study of the parent FISCA, and an observed model, based on responses to the FISCA-SR (GFI = .95). Correlations (measuring relative agreement) and paired comparisons of means (assessing absolute agreement) generally identified stronger agreement in "public" than "private" domains of impairment, and greater relative than absolute agreement in covert, antisocial domains.

Growth hormone-induced alteration in ErbB-2 phosphorylation status in 3T3-F442A fibroblasts

The growth hormone receptor (GHR), a cytokine receptor superfamily member, requires the JAK2 tyrosine kinase for signaling. We now examine functional interactions between growth hormone (GH) and epidermal growth factor (EGF) in 3T3-F442A fibroblasts. Although EGF enhanced ErbB-2 tyrosine phosphorylation, GH, while causing retardation of its migration on SDS-polyacrylamide gel electrophoresis, decreased ErbB-2's tyrosine phosphorylation. GH-induced retardation was reversed by treatment of anti-ErbB-2 precipitates with both alkaline phosphatase and protein phosphatase 2A, suggesting that GH induced serine/threonine phosphorylation of ErbB-2. Both GH-induced shift in ErbB-2 migration and GH-induced MAP kinase activation were unaffected by a protein kinase C inhibitor but were blocked by the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1 (MEK1) inhibitor, PD98059. Notably, leukemia inhibitory factor, but not interferon-gamma, also promoted ErbB-2 shift and mitogen-activated protein kinase activation. Cotreatment with EGF and GH versus EGF alone resulted in a 35% decline in acute ErbB-2 tyrosine 1248 autophosphorylation, a marked decline (approximately 50%) in DNA synthesis, and substantially decreased cyclin D1 expression. We conclude that in 3T3-F442A cells, 1) the GH-induced decrease in ErbB-2 tyrosine phosphorylation correlates with MEK1/mitogen-activated protein kinase activity and 2) GH antagonizes EGF-induced DNA synthesis and cyclin D1 expression in a pattern consistent with its alteration in ErbB-2 phosphorylation status.

Disulfide linkage of growth hormone (GH) receptors (GHR) reflects GH-induced GHR dimerization. Association of JAK2 with the GHR is enhanced by receptor dimerization

The growth hormone (GH) receptor (GHR) binds GH in its extracellular domain and transduces activating signals via its cytoplasmic domain. Both GH-induced GHR dimerization and JAK2 tyrosine kinase activation are critical in initiation of GH signaling. We previously described a rapid GH-induced disulfide linkage of GHRs in human IM-9 cells. In this study, three GH-induced phenomena (GHR dimerization, GHR disulfide linkage, and enhanced GHR-JAK2 association) were examined biochemically and immunologically. By using the GH antagonist, G120K, and an antibody recognizing a dimerization-sensitive GHR epitope, we demonstrated that GH-induced GHR disulfide linkage reflects GH-induced GHR dimerization. GH, not G120K, promoted both GHR disulfide linkage and enhanced association with JAK2. Measures that diminished GH-dependent JAK2 and GHR tyrosine phosphorylation diminished neither GH-induced GHR disulfide linkage nor GH-enhanced GHR-JAK2 association. By using both transient and stable expression systems, we determined that cysteine 241 (an unpaired extracellular cysteine) was critical for GH-induced GHR disulfide linkage; however, GH-induced GHR dimerization, GHR-JAK2 interaction, and GHR, JAK2, and STAT5 tyrosine phosphorylation still proceeded when this cysteine residue was mutated. We conclude GH-induced GHR disulfide linkage is not required for GHR dimerization, and activation and GH-enhanced GHR-JAK2 association depends more on GHR dimerization than on GHR and/or JAK2 tyrosine phosphorylation.

A catalytically active Jak2 is required for the angiotensin II-dependent activation of Fyn

Recent work with interleukins has shown a convergence of tyrosine phosphorylation signal transduction cascades at the level of the Janus and Src families of tyrosine kinases. Here we demonstrate that activation of the seven-transmembrane AT(1) receptor by angiotensin II induces a physical association between Jak2 and Fyn, in vivo. This association requires the catalytic activity of Jak2 but not Fyn. Deletion studies indicate that the region of Jak2 that binds Fyn is located between amino acids 1 and 240. Studies of the Fyn SH2 and SH3 domains demonstrate that the SH2 domain plays the primary role in Jak2/Fyn association. Not surprisingly, this domain shows a marked preference for tyrosine-phosphorylated Jak2. Surface plasmon resonance estimated the dissociation equilibrium constant (K(d)) of this association to be 2.36 nM. Last, in vivo studies in vascular smooth muscle cells show that, in response to angiotensin II, Jak2 activation is required for Fyn activation and induction of the c-fos gene. The significance of these data is that Jak2, in addition to serving as a critical angiotensin II activated signal transduction kinase, also functions as a docking protein and participates in the activation of Fyn by providing phosphotyrosine residues that bind the SH2 domain of Fyn.

Daily behavior ratings among child and adolescent inpatients: the abbreviated Child Behavior Rating Form

OBJECTIVE

Child and adolescent psychiatric inpatient facilities are in need of standardized behavior rating scales to assess continuous change in patient behaviors. This study used daily staff ratings to examine the factor structure and psychometric properties of an abbreviated version of the Child Behavior Rating Form (CBRF-A).

METHOD

Three hundred eighty-seven inpatients, aged 3 to 17 years, were rated daily by unit staff. Subsamples of patients and/or their parents completed additional measures of behavior problems (Child Behavior Checklist, Functional Impairment Scale for Children and Adolescents) to assess the instrument's validity.

RESULTS

Confirmatory factor analyses identified 5 behavior problem dimensions (Oppositionalism, Attention Problems, Overactivity, Withdrawal/Depression, and Anxiety), a second-order Externalizing dimension, and 2 positive behavior dimensions (Positive/Adaptive Social and Compliance/Self-Control). The scales were found to be internally consistent and showed expected age differences, and the scale factor structures were relatively stable over 1- and 2-week intervals. The scales correlated meaningfully with parent ratings of child behavior problems and functional impairment and were predictive of total hospital days.

CONCLUSIONS

The psychometric properties of the CBRF-A appear adequate for daily inpatient rating; additional research is needed to determine the usefulness of the CBRF-A in assessing treatment and medication effects over the hospital stay.

Growth hormone-mediated regulation of insulin-like growth factor I promoter activity in C6 glioma cells

The molecular mechanisms by which GH regulates insulin-like growth factor (IGF-I) gene expression remain obscure. One difficulty has been the lack of established GH-responsive cell lines that express the IGF-I gene. To develop such a cell line, we used rat C6 glioma cells which, as determined by RNase protection assay, express the IGF-I gene but not the GH receptor gene. To confer GH responsiveness, C6 cells were cotransfected with vectors that express the GH receptor (pRc/CMV WTrGHR) and Jak2 (pRc/CMV Jak2). GH responsiveness was demonstrated using luciferase reporter genes containing either the Sis-inducible element from the c-fos gene (pTK81-SIE-Luc) or 6 copies of the GH-responsive GAS-like element (GLE) from the rat spi2.1 gene (pSpi-GLE-Luc). The SIE is activated by binding of STAT1 and 3, whereas the GLE binds STAT5. In cells cotransfected with pRc/CMV WTrGHR, pRc/CMV Jak2, and either pTK81-SIE-Luc or pSpi GLE-Luc, treatment with 500 ng/ml GH for 24 h stimulated a 3.1- and 1.7-fold increase in luciferase activity, respectively. These data suggest that in C6 cells cotransfected with pRc/CMV WTrGHR and pRc/CMV Jak2, GH activates STAT1, 3, and 5. To determine whether GH-responsive IGF-I promoter activity could be demonstrated, C6 cells were cotransfected with pRc/CMV WTrGHR, pRc/ CMV Jak2, and an IGF-I-luciferase fusion gene that contained a fragment of the rat IGF-I gene that extended from -412 in the 5'-flanking region of exon 1 to the Met-22 in exon 3. GH stimulated a modest, but reproducible, 1.7-fold increase in luciferase activity in these cells, suggesting that a GH-responsive element is present in this region of the IGF-I gene. To better localize the GH-responsive element, cells were cotransfected with pRc/CMV WTrGHR, pRc/CMV Jak2 plus one of several IGF-I-luciferase fusion genes containing either fragments of one of the two promoters in the IGF-I gene or a fragment of intron 2 that includes a GH-responsive DNase I hypersensitivity site. For all constructs, treatment with GH for 24 h did not stimulate a significant increase in luciferase activity, suggesting that GH-responsive sequences are not located in these specific regions of the IGF-I gene or that GH-directed transcription of the IGF-I gene is mediated via several different regions of the IGF-I gene and the effect of any one of these regions in isolation was not sufficiently robust to be detected in this model system. In summary, transient expression of the GH receptor and Jak2 in C6 cells creates a GH-responsive system that activates STAT1, 3, and 5. Moreover, a fragment of the IGF-I gene that contains exons 1 and 2, a fragment of exon 3, and introns 1 and 2 is GH responsive using this model system.

Developmental regulation of insulin-like growth factor-I and growth hormone receptor gene expression

During development, the insulin-like growth factor I (IGF-I) gene is expressed in a tissue specific manner; however, the molecular mechanisms governing its developmental regulation remain poorly defined. To examine the hypothesis that expression of the growth hormone (GH) receptor accounts, in part, for the tissue specific expression of the IGF-I gene during development, the developmental regulation of IGF-I and GH receptor gene expression in rat tissues was examined. The level of IGF-I and GH receptor mRNA was quantified in RNA prepared from rats between day 17 of gestation (E17) and 17 months of age (17M) using an RNase protection assay. Developmental regulation of IGF-I gene expression was tissue specific with four different patterns of expression seen. In liver, IGF-I mRNA levels increased markedly between E17 and postnatal day 45 (P45) and declined thereafter. In contrast, in brain, skeletal muscle and testis, IGF-I mRNA levels decreased between P5 and 4M but were relatively unchanged thereafter. In heart and kidney, a small increase in IGF-I mRNA levels was observed between the early postnatal period and 4 months, whereas in lung, minimal changes were observed during development. The changes in GH receptor mRNA levels were, in general, coordinate with the changes in IGF-I mRNA levels, except in skeletal muscle. Interestingly, quantification of GH receptor levels by Western blot analysis in skeletal muscle demonstrated changes coordinate with IGF-I mRNA levels. The levels of the proteins which mediate GH receptor signaling (STAT1, -3, and -5, and JAK2) were quantified by Western blot analysis. These proteins also are expressed in a tissue specific manner during development. In some cases, the pattern of expression was coordinate with IGF-I gene expression, whereas in others it was discordant. To further define molecular mechanisms for the developmental regulation of IGF-I gene expression, protein binding to IGFI-FP1, a protein binding site that is in the major promoter of the rat IGF-I gene and is important for basal promoter activity in vitro, was examined. Gel shift analyses using a 34-base pair oligonucleotide that contained IGFI-FP1 did not demonstrate changes in protein binding that paralleled those in IGF-I gene expression, suggesting that protein binding to IGFI-FP1 does not contribute to the developmental regulation of IGF-I gene expression, at least in brain and liver. In summary, the present studies demonstrate coordinate expression of the IGF-I gene and GH receptor during development and suggest that GH receptor expression contributes to the tissue specific expression of the IGF-I gene during development.

The angiotensin II-dependent association of Jak2 and c-Src requires the N-terminus of Jak2 and the SH2 domain of c-Src

The binding of angiotensin II (Ang II) to AT1 is known to increase the kinase activity of several nonreceptor tyrosine kinases including Jak2 and c-Src. In the present study, we demonstrate that treatment of vascular smooth muscle cells with Ang II results in a rapid and transient association of Jak2 and c-Src. This association is dependent on a catalytically active Jak2 kinase, because it is blocked both by pharmacological means and by the inability of a catalytically inactive Jak2 to associate with c-Src. c-Src bound tyrosine phosphorylated Jak2 but was unable to bind an equal amount of unphosphorylated Jak2 protein, indicating that the SH2 domain of c-Src mediates this association. In vivo studies indicated that c-Src binds the N-terminus of Jak2 as expression of a Jak2 molecule lacking the initial 240 amino acids, including 16 tyrosines, and was unable to bind c-Src. Lastly, using transiently transfected COS-7 cells, we found that Ang II treatment induced an association between c-Src and wild-type Jak2 but not between c-Src and the Jak2 molecule that lacks the initial 240 amino acids. Thus, our data suggest that in addition to increasing the kinase activities Jak2 and c-Src, treatment of cells with Ang II results in the physical association of Jak2 and c-Src; an association that is mediated by the SH2 domain of c-Src and the N-terminus of Jak2.

Insulin inhibits growth hormone signaling via the growth hormone receptor/JAK2/STAT5B pathway

Insulin is important for maintaining the responsiveness of the liver to growth hormone (GH). Insulin deficiency results in a decrease in liver GH receptor (GHR) expression, which can be reversed by insulin administration. In osteoblasts, continuous insulin treatment decreases the fraction of cellular GHR localized to the plasma membrane. Thus, it is not clear whether hyperinsulinemia results in an enhancement or inhibition of GH action. We asked whether continuous insulin stimulation, similar to what occurs in hyperinsulinemic states, results in GH resistance. Our present studies suggest that insulin treatment of hepatoma cells results in a time-dependent inhibition of acute GH-induced phosphorylation of STAT5B. Whereas total protein levels of JAK2 were not reduced after insulin pretreatment for 16 h, GH-induced JAK2 phosphorylation was inhibited. There was a concomitant decrease in GH binding and a reduction in immunoreactive GHR levels following pretreatment with insulin for 8-24 h. In summary, continuous insulin treatment in rat H4 hepatoma cells reduces GH binding, immunoreactive GHR, GH-induced phosphorylation of JAK2, and GH-induced tyrosine phosphorylation of STAT5B. These findings suggest that hepatic GH resistance may develop when a patient exhibits chronic hyperinsulinemia, a condition often observed in patients with obesity and in the early stage of Type 2 diabetes.

Insulin receptor substrate-1 enhances growth hormone-induced proliferation

GH exerts a variety of metabolic and growth-promoting effects. GH induces activation of the GH receptor (GHR)-associated cytoplasmic tyrosine kinase, JAK2, resulting in tyrosine phosphorylation of the GHR and activation of STAT (signal transducer and activator of transcription), Ras-mitogen-activated protein kinase, and phosphoinositol 3-kinase signaling pathways, among others. GH-stimulated tyrosine phosphorylation of insulin receptor substrate (IRS) proteins has been demonstrated in vitro and in vivo. IRS-1 is a multiply phosphorylated cytoplasmic docking protein involved in metabolic and proliferative signaling by insulin, IL-4, and other cytokines, but the physiological role of IRS-1 in GH signaling is unknown. In this study, as noted by others, we detected in murine 3T3-F442A pre-adipocytes GH-dependent tyrosine phosphorylation of IRS-1 and specific GH-induced coimmunoprecipitation with JAK2 of a tyrosine phosphoprotein consistent with IRS-1. We further examined this interaction by in vitro affinity precipitation experiments with glutathione-S-transferase fusion proteins incorporating regions of rat IRS-1 and, as a source of JAK2, extracts of 3T3-F442A cells. Fusion proteins containing amino-terminal regions of IRS-1 that include the pleckstrin homology, phosphotyrosine-binding, and Shc and IRS-1 NPXY-binding domains, but not those containing other IRS-1 regions or glutathione-S-transferase alone, bound JAK2 from cell extracts. Tyrosine-phosphorylated JAK2 resulting from GH stimulation was included in the amino-terminal IRS-1 fusion precipitates; however, neither tyrosine phosphorylation of JAK2 nor treatment of cells with GH before extraction was necessary for the specific JAK2-IRS-1 interaction to be detected. In contrast, in this assay, specific insulin receptor association with the IRS-1 phosphotyrosine-binding, and Shc and IRS-1 NPXY-binding domains was insulin and phosphotyrosine dependent, as previously shown. To test for significance of IRS-1 with regard to GH signaling, IRS- and GHR-deficient 32D cells were stably reconstituted with the rabbit (r) GHR, either alone (32D-rGHR) or with IRS-1 (32D-rGHR-IRS-1). As assayed by three independent methods, GH induced proliferation in 32D-rGHR cells, even in the absence of transfected IRS-1. Notably, however, GH-induced proliferation was markedly enhanced in cells expressing IRS-1. Similarly, GH-induced mitogen-activated protein kinase activation was significantly augmented in IRS-1-expressing cells relative to that in cells harboring no IRS-1. These results indicate that IRS-1 enhances GH-induced proliferative signaling.

Growth hormone-dependent tyrosine phosphorylation of a GH receptor-associated high molecular WEIGHT protein immunologically related to JAK2

A critical step in growth hormone (GH) signalling is the GH-induced activation of the GH receptor (GHR)-associated tyrosine kinase, JAK2. JAK2 is a 120 kD member of the Janus family of tyrosine kinases, whose other mammalian members include JAK1, JAK3, and TYK2. Using 3T3-F442A murine preadipocytes, we now report detection of a Mr approximately 170 kD protein, referred to as HMW ("high molecular weight") JAK2, that is specifically reactive in immunoprecipitation and immunoblotting experiments with three independently-derived anti-JAK2 antibodies--two directed at carboxyl-terminal regions of the molecule and one directed at the amino-terminus. Like JAK2, HMW JAK2 is tyrosine phosphorylated in response to GH treatment of cells and is coimmunoprecipitated with anti-GHR serum. Thus, HMW JAK2 is a protein not heretofore described that is immunologically related to JAK2 and is physically and functionally associated with the GHR.

Blockade of growth hormone receptor shedding by a metalloprotease inhibitor

GH, an important growth-promoting and metabolic hormone, exerts its biological effects by interacting with cell surface GH receptors (GHRs). The GHR is a single membrane-spanning protein that binds GH via its extracellular domain. The high affinity GH-binding protein (GHBP), which corresponds to a soluble form of the GHR extracellular domain, carries a substantial fraction of the GH in the circulation of various species and probably has a role in modulation of the hormone's bioavailability. Although in rodents, it is believed that the GHBP is largely derived by translation of an alternatively spliced GHR messenger RNA, in humans and rabbits, proteolytic cleavage of the membrane-anchored receptor releases the GHR extracellular domain, which is believed to thereby become the GHBP. In this study, we used human IM-9 lymphocytes and GHR antibodies to study this proteolytic shedding of the GHBP. As determined by immunoblotting with anti-GHR cytoplasmic domain serum, addition of phorbol 12-myristate 13-acetate (PMA; 1 microg/ml) to serum-starved cells led to rapid loss (roughly 60% decline after 1 h; t(1/2) = approximately 5 min) of mature GHRs (115-140 kDa) from either total cell or detergent-soluble extracts. Loss of full-length GHRs was accompanied by accumulation of four proteins (65-68 kDa), each reactive with the cytoplasmically directed antiserum. The pattern of appearance of these GHR ctyoplasmic domain proteins, the electrophoretic and immunological characteristics of which are similar to those of a recombinant rabbit GHR mutant that lacks the extracellular domain, was such that progressively faster migrating forms were evident between 5-60 min of PMA exposure. Treatment with N-ethylmaleimide (NEM; 5 mM), an agent known to cause GHBP shedding from IM-9 cells, promoted a similar rapid loss of full-length GHRs and an accumulation of GHR cytoplasmic domain remnant proteins. PMA-induced, but not NEM-induced, GHR proteolysis was blocked by the protein kinase C inhibitor, GF109203X. Both PMA- and NEM-induced receptor proteolysis were, however, inhibited by the metalloprotease inhibitor, Immunex Compound 3 (minimum effective concentration, 10 microM). Notably, PMA and NEM also promoted shedding of GHBP into the conditioned medium of the cells, as determined by a chromatographic [125I]human GH binding assay; this GHBP shedding was also inhibited by Immunex Compound 3. These results strongly implicate a member(s) of the metalloprotease family as a potential GHBP-generating enzyme.

From the laboratory to the hospital, adults to adolescents, and disorders to personality: the case of psychological reactance

Study 1 assessed whether trait reactance in disturbed adolescents (ages 12 to 17) is part of the same constellation of personality variables associated with reactance in adults, and Study 2 examined whether reactance predicts inpatient treatment duration and outcomes. Correlations between reactance and MMPI-A variables among 76 inpatients (41 girls) showed that reactance is associated with oppositional, nonaffiliative, and narcissistic traits in disturbed adolescents as well as adults. Reactance predicted longer hospital stays among 176 adolescents (90 girls), and also changes in aggression, mood problems, and substance abuse among those in middle (n=89) but not early (n=87) adolescence. Additional analyses identified "typically male" and "typically female" patterns of reactance-change relationships. The clinical significance and utility of these findings are discussed.