FDA Approval Summary: Capmatinib and Tepotinib for the Treatment of Metastatic NSCLC Harboring MET Exon 14 Skipping Mutations or Alterations

The FDA approved capmatinib and tepotinib on May 6, 2020, and February 3, 2021, respectively. Capmatinib is indicated for patients with metastatic non-small cell lung cancer (mNSCLC) whose tumors have a mutation leading to mesenchymal-epithelial transition (MET) exon 14 skipping as detected by an FDA-approved test. Tepotinib is indicated for mNSCLC harboring MET exon 14 skipping alterations. The approvals were based on trials GEOMETRY mono-1 (capmatinib) and VISION (tepotinib). In GEOMETRY mono-1, overall response rate (ORR) per Blinded Independent Review Committee (BIRC) was 68% [95% confidence interval (CI), 48-84] with median duration of response (DoR) 12.6 months (95% CI, 5.5-25.3) in 28 treatment-naïve patients and 41% (95% CI: 29, 53) with median DoR 9.7 months (95% CI, 5.5-13) in 69 previously treated patients with NSCLC with mutations leading to MET exon 14 skipping. In VISION, ORR per BIRC was 43% (95% CI: 32, 56) with median DoR 10.8 months (95% CI, 6.9-not estimable) in 69 treatment-naïve patients and 43% (95% CI, 33-55) with median DoR 11.1 months (95% CI, 9.5-18.5) in 83 previously-treated patients with NSCLC harboring MET exon 14 alterations. These are the first two therapies to be FDA approved specifically for patients with metastatic NSCLC with MET exon 14 skipping.

FDA Approval Summary: Selpercatinib for the Treatment of Lung and Thyroid Cancers with RET Gene Mutations or Fusions

On May 8, 2020, the FDA granted accelerated approval to selpercatinib for (i) adult patients with metastatic RET fusion-positive non-small cell lung cancer (NSCLC), (ii) adult and pediatric patients ≥12 years of age with advanced or metastatic RET-mutant medullary thyroid cancer who require systemic therapy, and (iii) adult and pediatric patients ≥12 years of age with advanced or metastatic RET fusion-positive thyroid cancer who require systemic therapy and who are radioactive iodine refractory (if radioactive iodine is appropriate). Approval was granted on the basis of the clinically important effects on the overall response rate (ORR) with prolonged duration of responses observed in a multicenter, open-label, multicohort clinical trial (LIBRETTO-001, NCT03157128) in patients whose tumors had RET alterations. ORRs within the approved patient populations ranged from 64% [95% confidence interval (CI), 54-73] in prior platinum-treated RET fusion-positive NSCLC to 100% (95% CI, 63-100) in systemic therapy-naïve RET fusion-positive thyroid cancer, with the majority of responders across indications demonstrating responses of at least 6 months. The product label includes warnings and precautions for hepatotoxicity, hypertension, QT interval prolongation, hemorrhagic events, hypersensitivity, risk of impaired wound healing, and embryo-fetal toxicity. This is the first approval of a drug specifically for patients with RET alterations globally.

Gene expression signatures of breast cancer stem and progenitor cells do not exhibit features of Warburg metabolism

INTRODUCTION

Cancers are believed to adapt to continual changes in glucose and oxygen availability by relying almost exclusively on glycolytic metabolism for energy (i.e. the Warburg effect). The process by which breast cancers sustain growth in avascular tissue is thought to be mediated via aberrant hypoxia response with ensuing shifts in glycolytic metabolism. Given their role in initiating and perpetuating tumors, we sought to determine whether breast cancer stem and progenitor cells play an instrumental role in this adaptive metabolic response.

METHODS

Breast cancer stem/progenitor cells were isolated from invasive ductal carcinomas, and benign stem cells (SC) were isolated from reduction mammoplasty tissues. Relative expression of 33 genes involved in hypoxia and glucose metabolism was evaluated in flow cytometrically isolated stem and progenitor cell populations. Significance between cohorts and cell populations was determined using Student's 2-tailed t test.

RESULTS

While benign stem/progenitor cells exhibited few significant inter-group differences in expression of genes involved in hypoxia regulation or glucose metabolism, breast cancer stem/progenitor cells demonstrated significant inter-group variability. Breast cancer stem/progenitor cells adapted to microenvironments through changes in stem cell numbers and transcription of glycolytic genes. One of four breast cancer stem/progenitor cells subpopulations exhibited an aerobic glycolysis gene expression signature. This subpopulation comprises the majority of the tumor and therefore best reflects invasive ductal carcinoma tumor biology. Although PI3K/AKT mutations are associated with increased proliferation of breast cancer cells, mutations in breast cancer stem/progenitor cells subpopulations did not correlate with changes in metabolic gene expression.

CONCLUSIONS

The adaptive capacity of breast cancer stem/progenitor cells may enable tumors to survive variable conditions encountered during progressive stages of cancer growth.

S/MAR sequence confers long-term mitotic stability on non-integrating lentiviral vector episomes without selection

Insertional oncogene activation and aberrant splicing have proved to be major setbacks for retroviral stem cell gene therapy. Integrase-deficient human immunodeficiency virus-1-derived vectors provide a potentially safer approach, but their circular genomes are rapidly lost during cell division. Here we describe a novel lentiviral vector (LV) that incorporates human ß-interferon scaffold/matrix-associated region sequences to provide an origin of replication for long-term mitotic maintenance of the episomal LTR circles. The resulting 'anchoring' non-integrating lentiviral vector (aniLV) achieved initial transduction rates comparable with integrating vector followed by progressive establishment of long-term episomal expression in a subset of cells. Analysis of aniLV-transduced single cell-derived clones maintained without selective pressure for >100 rounds of cell division showed sustained transgene expression from episomes and provided molecular evidence for long-term episome maintenance. To evaluate aniLV performance in primary cells, we transduced lineage-depleted murine hematopoietic progenitor cells, observing GFP expression in clonogenic progenitor colonies and peripheral blood leukocyte chimerism following transplantation into conditioned hosts. In aggregate, our studies suggest that scaffold/matrix-associated region elements can serve as molecular anchors for non-integrating lentivector episomes, providing sustained gene expression through successive rounds of cell division and progenitor differentiation in vitro and in vivo.

Cell-cell transmission of VSV-G pseudotyped lentivector particles

Many replicating viruses, including HIV-1 and HTLV-1, are efficiently transmitted from the cell surface of actively infected cells upon contact with bystander cells. In a previous study, we reported the prolonged cell surface retention of VSV-G replication-deficient pseudotyped lentivector prior to endocytic entry. However, the competing kinetics of cell surface versus dissociation, neutralization or direct transfer to other cells have received comparatively little attention. Here we demonstrate that the relative efficiency of cell-cell surface transmission can outpace "cell-free" transduction at limiting vector input. This coincides with the prolonged half-life of cell bound vector but occurs, unlike HTLV-1, without evidence for particle aggregation. These studies suggest that cell-surface attachment stabilizes particles and alters neutralization kinetics. Our experiments provide novel insight into the underexplored cell-cell transmission of pseudotyped particles.

RNA trafficking by acute myelogenous leukemia exosomes

Extrinsic signaling cues in the microenvironment of acute myelogenous leukemia (AML) contribute to disease progression and therapy resistance. Yet, it remains unknown how the bone marrow niche in which AML arises is subverted to support leukemic persistence at the expense of homeostatic function. Exosomes are cell membrane-derived vesicles carrying protein and RNA cargoes that have emerged as mediators of cell-cell communication. In this study, we examined the role of exosomes in developing the AML niche of the bone marrow microenvironment, investigating their biogenesis with a focus on RNA trafficking. We found that both primary AML and AML cell lines released exosome-sized vesicles that entered bystander cells. These exosomes were enriched for several coding and noncoding RNAs relevant to AML pathogenesis. Furthermore, their uptake by bone marrow stromal cells altered their secretion of growth factors. Proof-of-concept studies provided additional evidence for the canonical functions of the transferred RNA. Taken together, our findings revealed that AML exosome trafficking alters the proliferative, angiogenic, and migratory responses of cocultured stromal and hematopoietic progenitor cell lines, helping explain how the microenvironmental niche becomes reprogrammed during invasion of the bone marrow by AML.

Intra-hematopoietic cell fusion as a source of somatic variation in the hematopoietic system

Cell fusion plays a well-recognized, physiological role during development. Bone-marrow-derived hematopoietic cells have been shown to fuse with non-hematopoietic cells in a wide variety of tissues. Some organs appear to resolve the changes in ploidy status, generating functional and mitotically-competent events. However, cell fusion exclusively involving hematopoietic cells has not been reported. Indeed, genomic copy number variation in highly replicative hematopoietic cells is widely considered a hallmark of malignant transformation. Here we show that cell fusion occurs between cells of the hematopoietic system under injury as well as non-injury conditions. Experiments reveal the acquisition of genetic markers in fusion products, their tractable maintenance during hematopoietic differentiation and long-term persistence after serial transplantation. Fusion events were identified in clonogenic progenitors as well as differentiated myeloid and lymphoid cells. These observations provide a new experimental model for the study of non-pathogenic somatic diversity in the hematopoietic system.

Entry kinetics and cell-cell transmission of surface-bound retroviral vector particles

BACKGROUND

Transduction with recombinant HIV-1 derived lentivirus vectors is a multi-step process initiated by surface attachment and subsequent receptor-directed uptake into the target cell. We previously reported the retention of vesicular stomatitis virus G protein pseudotyped particles on murine progenitor cells and their delayed cell-cell transfer.

METHODS

To examine the underlying mechanism in more detail, we used a combination of approaches focused on investigating the role of receptor-independent factors in modulating attachment.

RESULTS

The investigation of synchronized transduction reveals cell-type specific rates of vector particle clearance with substantial delays during particle entry into murine hematopoietic progenitor cells. The observed uptake kinetics from the surface of the 1 degrees cell correlate inversely with the magnitude of transfer to 2 degrees targets, corresponding with our initial observation of preferential cell-cell transfer in the context of brief vector exposures. We further demonstrate that vector particle entry into cells is associated with the cell-type specific abundance of extracellular matrix fibronectin. Residual particle-extracellular fibronectin matrix binding and 2 degrees transfer can be competitively disrupted by heparin exposure without affecting murine progenitor homing and repopulation.

CONCLUSIONS

Although cellular attachment factors, including fibronectin, aid gene transfer by colocalizing particles to cells and disfavoring early dissociation from targets, they also appear to stabilize particles on the cell surface. The present study highlights the inadvertent consequences for cell entry and cell-cell transfer.

Cellular microvesicle pathways can be targeted to transfer genetic information between non-immune cells

Eukaryotic cell communication is based on protein signaling cascades that require direct cell-cell apposition, or receptor engagement by secreted molecules. The transmission of genetic information is thought to be uncommon, apart from recent reports of exosomal RNA transfer in immune and glioblastoma cells. We wished to examine if existing microvesicle pathways could be directly targeted for the horizontal transfer of RNA genomes in less specialized cell types. Using replication-deficient retrovirus vector, studies herein confirm that a range of cells routinely sequester a small population of these RNA genomes in a non-canonical compartment, refractory to antibody neutralization and unaffected by specific pharmacological inhibition of pathways involved in conventional viral trafficking. Our experiments further reveal the cytoplasmic colocalization of vector genomes with tetraspanin proteins as well as the PI-3-kinase sensitive trafficking and subsequent transmission to 2 degrees targets. Collectively, our results indicate a scalable process whereby cells route vector genomes to multivesicular bodies (MVB) for cytoplasmic trafficking and exosomal release. Our findings imply that cells can serve to deliver recombinant payload, targeted for the stable genetic modification of 2 degrees target cells.

CXCR4 induction in hematopoietic progenitor cells from Fanca(-/-), -c(-/-), and -d2(-/-) mice

OBJECTIVE

Bone marrow failure is a near-universal occurrence in patients with Fanconi anemia (FA) and is thought to result from exhaustion of the hematopoietic stem cell (HSC) pool. Retrovirus-mediated expression of the deficient protein corrects this phenotype and makes FA a candidate disease for HSC-directed gene therapy. However, inherent repopulation deficits and stem cell attrition during conventional transduction culture prevent therapeutic chimerism.

MATERIALS AND METHODS

We previously reported rapid transduction protocols to limit stem cell losses after ex vivo culture. Here we describe a complementary strategy intended to improve repopulation through upregulation of chemokine receptor (CXCR) 4, a principal factor in hematopoietic homing.

RESULTS

Using murine models with transgenic disruption of Fanca, -c, and -d2, we found that c-kit(+) and sca-1(+) progenitor cells express levels of CXCR4 comparable with those of wild-type littermates. Lineage-depleted progenitor populations rapidly upregulated CXCR4 transcript and protein in response to cytokine stimulation or hypoxia, regardless of genotype. Hypoxia conditioning of lineage-depleted Fancc(-/-) progenitors also reduced oxidative stress, improved in vitro migration and led to improved chimerism in myeloablated recipients after transplantation.

CONCLUSION

These studies provide evidence that CXCR4 regulation in progenitor cells from transgenic mice representing multiple FA genotypes is intact and that modulation of homing offers a potential strategy to offset the FA HSC repopulation deficiency.

High frequency induction of CC to TT tandem mutations in DNA repair-proficient mammalian cells

The CC to TT tandem mutation is induced by UV radiation exposure, though at relatively low frequencies when compared with the more commonly induced C to T mutation. Induction of the tandem mutation by UV is enhanced in mammalian cells with certain genetic deficiencies; however, conditions have not been described in which the frequency of this mutation is enhanced in DNA repair-proficient mammalian cells. For this study, an integrated construct that detects C to T and CC to TT mutations at a single codon in mouse Aprt was used to examine UVB mutagenesis under various conditions. Oxidative stress, in the form of intracellular hydrogen peroxide, increased the frequency of UVB-induced CC to TT mutations. Surprisingly, exposure of the cells to two antioxidants (N-acetylcysteine and trolox), either alone or in combination, also enhanced UVB induction of CC to TT tandem mutations. These results demonstrate, for the first time, that the frequency of UVB-induced CC to TT tandem mutations can be enhanced dramatically in DNA repair-proficient mammalian cells, and suggest that the enhancing effect does not require direct damage to DNA.

The frequency of CC to TT tandem mutations in mismatch repair-deficient cells is increased in a cytosine run

Mononucleotide runs are hot spots for frameshift mutations in mismatch repair (MMR)-deficient cells. However, a role for mononucleotide runs in the formation of base pair substitutions has not been tested. Previously, we demonstrated that ultraviolet radiation C (UVC)- or reactive oxygen species-induced CC to TT tandem mutations are markedly enhanced in MMR-deficient cells. The target for the mutational analysis was two cytosines in a run of five cytosines (5C) within mouse Aprt. Because mutation from C to T for either or both of the two critical cytosines created a codon yielding a functional Aprt protein, this assay allowed both single and tandem substitutions to be quantified and the relative ratios compared. To determine if the cytosine run increased the frequency of single and/or tandem base pair substitutions, alternative constructs were created in which the cytosine run was disrupted by flanking the target cytosines with either thymines (2Cpyr) or adenines (2Cpur). Disruption of the cytosine run dramatically decreased the frequency of UVC-induced tandem mutations in the 2Cpyr and 2Cpur constructs, as compared with the 5C construct. Moreover, CC to TT tandem mutations occurred spontaneously or were induced by oxidative stress only within the 5C construct. These results demonstrate that CC to TT tandem mutations in MMR-deficient cells form more readily in a homocytosine run than in a sequence limited to two cytosines.

A role for Pms2 in the prevention of tandem CC --> TT substitutions induced by ultraviolet radiation and oxidative stress

DNA mismatch repair (MMR) is important for preventing base-pair substitutions caused by spontaneous or damage-related DNA polymerase errors. We have used a reversion assay based on mouse Aprt to investigate the role of MMR in preventing ultraviolet radiation (UV) and oxidative stress induced tandem CC --> TT base pair substitutions in cultured mammalian cells. The reversion construct used for this assay can detect both C --> T and CC --> TT mutational events. Most spontaneous mutations in Pms2-deficient cells were single C --> T substitutions (88%), with the remainder being tandem CC --> TT substitutions (12%). The percentage of tandem CC --> TT substitutions rose to 64% and 94% for Pms2-deficient cells exposed to UV and a mixture of hydrogen peroxide and metals (Cu/Fe), respectively. Exposure to hydrogen peroxide alone or metals alone did not induce the tandem substitutions, nor did treatment of the cells with the alkylating agent ethylmethane sulfonate, which induces G --> A substitutions on the opposite strand. Tandem CC --> TT substitutions were also induced by UV irradiation and the hydrogen peroxide/metal mixture in Pms2-proficient cells, but at frequencies significantly lower than those observed in the Pms2-deficient cells. We conclude that mismatch repair plays an important role in preventing tandem CC --> TT substitutions induced by certain genotoxin exposures.

Oxidative mutagenesis, mismatch repair, and aging

A PubMed search for the term "oxidative stress" yields over 29,000 articles published on the subject over the past 10 years; more than 2000 of these articles also include the term "aging" in their title or abstract. Many theories of aging predict causal roles for oxidative stress in the myriad of pathological changes that occur as a function of age, including an increasing propensity to develop cancer. A possible link between aging and cancer is the induction and accumulation of somatic mutations caused by oxidative stress. This Review focuses on small mutational events that are induced by oxidative stress and the role of mismatch repair (MMR) in preventing their formation. It also discusses a possible inhibitory effect of oxidative stress on MMR. We speculate that a synergistic interaction between oxidative damage to DNA and reduced MMR levels will, in part, account for an accumulation of small mutational events, and hence cancer, with aging.

Post-transfusion white cell count in the sick preterm neonate

OBJECTIVE

A previous report demonstrated post-transfusion leucocytosis as a potential confounding factor in the diagnosis of sepsis in critically ill adult patients. In We wished to establish if the same phenomenon occurred in the sick preterm neonate and whether this significantly altered the indices considered for potential neonatal infection.

METHODOLOGY

Transfusion and full blood count data in a level 3 neonatal intensive care unit were prospectively recorded for 3 months.

RESULTS

One hundred and fourteen transfusion events were recorded from 37 infants. Median white blood cell count increased 0.9 x 109/L (confidence interval (CI) 0.4-2.4) in the first 8 h following transfusion (P = 0.032). Median neutrophil count increased by 0.4 x 109/L (CI 0.1-1.7) in the same 8 h (P = 0.05). Median neutrophil left shift decreased 1.2% (CI 1.1-5.8%) over the 24 h post-transfusion. No change in band count was observed.

CONCLUSIONS

A mild post-transfusion white cell increase occurs in sick neonates. Because of the magnitude of effect, it is unlikely that this interesting physiological response would interfere with the diagnosis of sepsis in this population.

Growth and growth factors in premature infants receiving dexamethasone for bronchopulmonary dysplasia

Physical growth and the serum growth factors, insulin growth factor 1 (IGF1) and its binding protein (IGFBP3) were measured weekly during dexamethasone treatment and for 3 weeks after stopping therapy in 10 ventilated babies [median (range) birth weight 860 g (640-1210); median (range) gestational age 26 weeks (24-29)] with bronchopulmonary dysplasia (BPD). The mean (+/- SE) rates of change of all physical measures except crown-rump length (CRL) increased significantly after stopping dexamethasone: weight gain 13.2 (+/- 1.5) on versus 1.0 (+/- 1.9) g/day off treatment; occipital-frontal circumference 0.7 (+/- 0.1) cm/week; CRL 0.5 (+/- 0.1) versus 0.7 (+/- 0.1) (TBL) 0.7 (+/- 0.1) versus 1.1 (+/- 0.1) cm/week; CRL 0.5 (+/- 0.1) versus 0.7 (+/- 0.1) cm/week, and knee-ankle length (KAL) 0.13 (+/- 0.02) versus 0.36 (+/- 0.04) cm/week. Mean serum IGF-1 (1.57 +/- 0.13 versus 3.56 +/- 0.41 nmol/L) and IGFBP3 (0.94 +/- 0.03 versus 1.12 +/- 0.05 mg/L) levels also increased off treatment. The weekly dose of dexamethasone (mg/kg) was significantly negatively correlated with all physical growth measures (P < 0.01), but showed no correlation with growth factors. Protein intake (g/kg/day) was significantly correlated (P < 0.01) with weight gain (r = 0.28), changes (TBL) (r = 0.32), serum IGF1 levels (r = 0.60), and IGFBP3 levels (r = 0.37). All aspects of physical growth are compromised during dexamethasone treatment for BPD. Poor growth during steroid treatment is associated with lower IGF1 and IGFBP3 levels. Further study is needed to examine the effect of varying dexamethasone dosage regimes and nutritional intake on the growth process in BPD.

The measurement of knee-heel length in newborn infants using a simple vernier calipers

OBJECTIVE

To assess the usefulness of a simple vernier calipers for measuring knee-heel length in neonates.

SUBJECTS AND METHODS

Using a simple vernier calipers, knee-heel length was measured five times by 2 observers in 50 babies (29M, 21F; mean birthweight 1597 g; median gestational age at birth 29 weeks) at a median postnatal age of 11 days. A subgroup of 20 babies had knee-heel length measured similarly at weekly intervals for 3 weeks. Corrected gestational age and weight were simultaneously recorded. One observer was experienced in using the vernier calipers. The precision of the calipers was established using 4 steel gauge blocks of varying length (7.62-10.17 cm).

RESULTS

The calipers were very precise when measuring steel gauge blocks. In babies, there was a downward trend across the first 2 measurements for both observers, the measurements stabilizing over the last three. Using the final three measurements per baby (n = 50), the experienced observer had a mean standard deviation of 0.023 cm and mean coefficient of variation 0.23% when measuring an average knee-heel length of 9.99 cm. The inexperienced observer had a mean standard deviation of 0.057 cm and a mean coefficient of variation of 0.56%, when measuring an average knee-heel length of 10.14 cm. The inter-observer reliability, measured by the intra-class correlation coefficient, was 0.99. The agreement between observers was such that one observer measured knee-heel length consistently less (0.15 cm, SD 0.18 cm) than the other. The reliability for knee-heel length velocity was lower (R = 0.85), but agreement between observers was high with an average difference of 0.016 cm/week. Knee-heel length was significantly correlated (p < 0.001) with corrected gestational age (r = 0.85) and with weight (r = 0.96). There was a weaker but significant correlation (r = 0.47, p < 0.001) between knee-heel length velocity and rate of weight gain (g/day), indicating that weight gain may not always be accompanied by an increase in linear growth.

CONCLUSION

The measurement of knee-heel length by a simple vernier calipers is an accurate, reproducible and non-invasive method of assessing short-term linear growth in neonates. However, it is recommended that measurements of knee-heel length in a individual baby should be made by a single experienced observer.

Changes in the urinary excretion of creatinine, albumin and N-acetyl-beta-D-glucosaminidase with increasing age and maturity in healthy schoolchildren

Raised urinary levels of albumin and N-acetyl-beta-D-glucosaminidase (NAG) are predictive of abnormal renal function and excretion of these substances is often expressed as a creatinine ratio. However, it is important to establish normal reference limits of albumin and NAG excretion for comparison of values from patients. For this reason, overnight excretion rates of creatinine, albumin and NAG were determined in timed overnight urine samples from 528 healthy schoolchildren (260 boys, 268 girls; 4-16 years) of normal size. There was a significant correlation with age and puberty for all substances in both sexes (P < 0.01). Peak creatinine excretion occurred at 16 years in boys, at 15 years in girls and at pubertal stage 5 in both sexes. Maximum albumin excretion was seen at 15 years and genital stage 5 in boys and at 16 years and breast stage 4 in girls. Peak NAG excretion occurred earlier, at 14 years and genital stage 4 in boys and at 13 years and breast stage 3 in girls. Boys excreted significantly more creatinine compared with girls before and during puberty (reflecting greater muscle mass) (P < 0.001) while excretion rates for albumin and NAG were similar in both sexes. Height and weight combined accounted for 58% and 29% of the variation in creatinine and NAG excretion respectively, while height alone predicted 20% of variation in albumin excretion.

CONCLUSION

Age and puberty influence the urinary excretion of albumin and NAG while sex has an additional effect on creatinine excretion. The urinary excretion of albumin and NAG in children with renal disorders should be compared with age-related normal ranges while creatinine excretion could be used as a marker of muscle growth.

Urinary insulin-like-growth factor I in normal children: relationship to age, pubertal status and urinary growth hormone

Authentic insulin-like growth factor 1 (IGF-I) can be detected in human urine at one thousandth of the serum level, with which it correlates closely. The aim of this study was to establish the normal range of urinary IGF-I (uIGF-I) in relation to age, sex, and pubertal status, and to define the relationship between uIGF-I and urinary growth hormone (uGH). IGF-I was measured by RIA after acid extraction of IGF-I binding protein, and separation by gel chromatography in 302 healthy children (149 boys and 153 girls) in whom uGH had already been measured. The mean amount of uIGF-I excreted each night ranged from 17.5 ng (males) and 14.9 ng (females) at pubertal stage I (PS 1), to a peak of 66.8 ng (males) at PS 4, and 55.8 ng (females) at PS 3, coinciding with peak uGH excretion. Highly significant correlations were found between uGH and uIGF-I both before and during puberty (P < 0.01). These findings extend the range of non-invasive investigation available in growth disorders and physiological studies.

Nocturnal urinary growth hormone excretion in growth hormone-deficient children on and off growth hormone treatment

Non-compliance has been reported as a major issue in growth hormone (GH) therapy. We explored the use of urinary GH (uGH) measurements to monitor the GH treatment of 18 children (aged 5-16 years) diagnosed as GH deficient on the basis of history, phenotype, auxology and peak GH concentration during 2 provocation tests of < 15 mU/l. Each child collected 5 consecutive overnight urine samples while on GH replacement schedules, then discontinued treatment for 2 days and collected a further 5 urine samples. The mean mass of uGH excreted on treatment (8.6 ng, range 3.6-13.0 ng) was significantly greater than that off treatment (1.2 ng, range 0.6-2.7 np; p < 0.01). All uGH values on treatment exceeded the mean nocturnal uGH excretion of normal age- and sex-matched children. The clear distinction between uGH levels on and off GH treatment indicates that uGH measurement would determine whether two or more GH injections had been missed. A series of uGH estimates over a 2-week period may provide a realistic perspective on injection frequency.

The influence of body mass index on growth hormone secretion in normal and short statured children

Obesity is one of the factors which limits the value of growth hormone (GH) provocation tests in the diagnosis of GH deficiency. We have therefore examined (1) the relationship between urinary GH (uGH), a physiological parameter of GH secretion, and percent ideal body mass index (BMI%), an indirect estimate of body fat, in 528 schoolchildren; and (2) the extent to which peak arginine stimulated (0.5 g/kg i.v.) GH concentrations were influenced by BMI% in 176 short normal (SN) children and 48 girls with Turner syndrome (TS). The mean BMI% (SD) for each group was 102.9 (10.8) in schoolboys, 102.7 (13.4) in schoolgirls, 95.8 (13.9) in SN boys, 98.2 (21.4) in SN girls and 105.9 (18.0) in TS. BMI% correlated inversely with log uGH in school-children (boys r = -0.16, P = 0.01; girls r = -0.25, P < 0.001). However, if each sex was subdivided by pubertal status, the inverse relationship only persisted in pubertal (boys r = -0.18, P = 0.04; girls r = -0.39, P < 0.001) but not prepubertal children (boys r = -0.1, P = 0.3; girls r = -0.11, P = 0.3). BMI% was also inversely related to log peak stimulated GH concentration in SN girls (r = -0.49, P < 0.001) but not SN boys (r = -0.14, P = 0.2) or girls with TS (r = 0.19, P = 0.2). The inverse relationship between normal body fat and physiological GH secretion becomes significant during puberty; in girls it accounts for 15% of the variability in uGH excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Variability in the urinary excretion of growth hormone in children: a comparison with other urinary proteins

As a basis for assessment of the clinical validity of urinary GH (uGH) measurements in children, the day-to-day variability in renal handling of GH has been compared with that of albumin, N-acetylglucosaminidase (NAG) and creatinine. Five overnight urine specimens were collected over a 2-week period from 78 healthy children (aged 5-16 years), 20 of normal stature and 58 with growth disorders; ten children were classified as GH-deficient (GHD) and 48 were designated short normal (SN). The variability of excretion of each substance was expressed as a coefficient of variation (C.V.) which was not influenced by expressing the urine results as total mass excreted, concentration, excretion rate or as a ratio to creatinine. There was considerable night-to-night variability in the excretion of all substances (mean C.V. values for all groups: 56% for albumin, 41% for GH, 33% for NAG and 27% for creatinine). No differences were found in the variability of GH excretion between males and females, nor between prepubertal and pubertal subjects. The mean C.V. for uGH excretion ranged from 37% in normal and 35% in SN children to 52% in those with GHD (P < 0.05). Assay variation rather than a change in renal protein handling accounted for the large variations in uGH concentrations of < 5 pg/ml, thus contributing to the high uGH C.V. of the GHD group.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary growth hormone excretion in the assessment of children with disorders of growth

OBJECTIVE

We wished to evaluate the use of urinary GH measurements when compared to conventional GH provocation tests in the assessment of short children.

DESIGN

Children presenting for the first time to a regional growth clinic were assessed clinically by one observer. Investigations comprising standard GH provocation tests and measurement of urinary GH were undertaken to exclude GH deficiency.

PATIENTS

Fifty-eight children aged 5.8-16 years were enrolled. Ten were diagnosed on clinical assessment as GH deficient, 43 had delayed growth and/or familial short stature, and five had idiopathic short stature; the 48 children in the last two groups were defined as short normal.

MEASUREMENTS

GH secretion was evaluated by two standard provocation tests and by the measurement of GH in five overnight urine collections. A normal peak GH concentration was defined as > 16 mU/l. The values for urinary GH excretion were compared to normal ranges (+/- 2 standard deviations from the mean), established in healthy schoolchildren of normal stature.

RESULTS

All children considered GH deficient on clinical grounds had low peak GH concentrations on provocation tests, while 8/10 had low values of urinary GH excretion. All short normal children with normal peak GH concentrations (n = 36) on provocation tests and 11/12 children with low peak GH concentrations had urinary GH excretion within the normal range. There was therefore a significant difference in the classification of 'normal' GH secretion in the two tests. If the clinical diagnosis was used as the standard by which GH tests were judged, the predictive value of a positive urinary GH test in the diagnosis of GH deficiency was 89% compared with 45% for GH provocation tests.

The influence of age, size, pubertal status and renal factors on urinary growth hormone excretion in normal children and adolescents

Overnight urinary growth hormone (GH) excretion was measured in 528 schoolchildren (aged 4-16 years) whose heights and weights were between the third and 97th centiles. Urinary GH increased significantly with age, reaching a maximum in boys at 15-years-old and in girls at 13-years-old. Peak levels were five and three times higher in boys and girls respectively than in 4-year-olds. Maximum urinary GH excretion was seen at breast stages 3 and 4 in girls and at genital stage 4 in boys followed by a decline in both sexes at stage 5. Boys excreted more GH than girls during prepubertal and pubertal years. During prepubertal years there were fluctuations of urinary excretion of GH with age. Height, weight and pubertal status predicted 31% of the variability of urinary excretion of GH, and urinary excretion of creatinine, albumin and N-acetylglucosaminidase (NAG) predicted 52% of the variability. The importance of establishing sound age and sex-related reference ranges for urinary growth hormone is stressed before application of this test to children with growth disorders.

Topical chemotherapy for burns using cerium salts and silver sulfadiazine

These experimental data indicate that cerium compounds exert a measurable antimicrobial action in vitro. In vivo the simultaneous use of cerium sulfadiazine and silver sulfadiazine was more effective than silver sulfadiazine alone or the combination of cerous nitrate and silver sulfadiazine. When cerous nitrate was used clically, gram-positive bacteria predominated. In contrast, wounds exposed to silver salts alone harbor a predominately gram-negative flora. The combination of cerous nitrate and silver sulfadiazine appears to provide a broad spectrum inhibitory to both types of organisms. It is apparent that a sampling problem exists in any attempt to monitor wounds that may exceed a square meter in extent. These bacteriologic data pertain only to the surface flora. The need to culture tissue samples of burn wounds has been emphasized. Our experience, however, is that invasion of deep tissue without dense surface colonization, greater than 10(5), is infrequent. Furthermore, fragments of eschar were submitted regularly for culture; those results confirmed the surface culture findins. The characteristic yellow-green color of cerium nitrate treated eschars may results from oxidation of trivalent cerium to yellow ceric ions. Free silver and sulfadiazine ions are available also in small amounts because of limited ionization of the highly insoluble silver sulfadiazine. This might promote the in vivo formation of cerous sulfadiazine and would provide a continuous source of ionic cerium for microbial inhibition. The modification of silver sulfadiazine cream by incorporating cerous nitrate into it strikingly enhances its topical antiseptic effect in burn wounds without increasing toxicity.

Cerium nitrate: a new topical antiseptic for extensive burns

The wounds of 60 burned patients were treated topically with cerium nitrate, which was applied either as a cream or in aqueous solution. Cerium nitrate has a potent antiseptic effect in human burn wounds, especially against gram negative bacteria and fungi. Pseudomonas aeruginosa was recovered from the wounds infrequently and never predominated. Fungi were practically never found. No patient treated with cerium developed a necrotizing wound infection. Analysis of the detailed bacteriological data indicated that, in contrast to previous results with use of the nitrate or sulfadiazine salts of silver, when gram negative species predominated, the flora tended to be predominantly gram positive when cerium was used. Therefore, some patients were treated simultaneously with cerium nitrate and silver sulfadiazine; this resulted in an even more efficient suppression of the wound flora than was observed previously with either cerium alone or silver salts alone; results with the simultaneous topical therapy in patients with injuries that previously were uniformly lethal were excellent. No toxicity attributable to the use of cerium was observed, although one instance of methemoglobinemia due to nitrate was documented. The adsorption of topically applied cerium essentially is nil. The use of cerium nitrate was associated with a nearly 50 percent reduction in the anticipated death rate. Cerium nitrate is a promising new topical antiseptic agent for the treatment of burns, particularly when it is used in combination with silver sulfadiazine.

Characterization of lymphocyte transformation induced by zinc ions

Lymphocyte cultures from all normal human adults are stimulated by zinc ions to increase DNA and RNA synthesis and undergo blast transformation. Optimal stimulation occurs at 0.1 mM Zn(++). Examination of the effects of other divalent cations reveals that 0.01 mM Hg(++) also stimulates lymphocyte DNA synthesis. Ca(++) and Mg(++) do not affect DNA synthesis in this culture system, while Mn(++), Co(++), Cd(++), Cu(++), and Ni(++) at concentrations of 10(-7)-10(-3) M are inhibitory. DNA and RNA synthesis and blast transformation begin to increase after cultures are incubated for 2-3 days with Zn(++) and these processes reach a maximum rate after 6 days. The increase in Zn(++)-stimulated lymphocyte DNA synthesis is prevented by rendering cells incapable of DNA-dependent RNA synthesis with actinomycin D or by blocking protein synthesis with cycloheximide or puromycin. Zn(++)-stimulated DNA synthesis is also partially inhibited by 5'-AMP and chloramphenicol. Zn(++) must be present for the entire 6-day culture period to produce maximum stimulation of DNA synthesis. In contrast to its ability to independently stimulate DNA synthesis, 0.1 mM Zn(++) inhibits DNA synthesis in phytohemagglutinin-stimulated lymphocytes and L1210 lymphoblasts.

Isolation of a clone of Chinese hamster ovary cells deficient in plant lectin-binding sites

Ricin, a galactose-binding lectin with potent cytotoxic activity, was used to select a clone of Chinese hamster ovary cells with altered plant lectin-binding properties. The clone (15B) is 80-fold less sensitive to the toxic action of ricin than the parent line. In the absence of ricin, it grows both in monolayer and suspension culture with a normal generation time. Plating efficiency, however, is significantly reduced. Relative to the parent cells, its binding of the Ricinus communis lectins, Phaseolus vulgaris erythroagglutinating phytohemagglutinin, Abrus precatorius phytohemagglutinin, and soybean phytohemagglutinin is less than 7%, while binding of lentil phytohemagglutinin, wheat-germ agglutinin, and mushroom phytohemagglutinin is 17%, 40%, and 109%, respectively. In contrast, its concanavalin A binding is increased by 70%. Consistent with these alterations, crude membrane preparations of the 15B cells were found to contain the same sugars as the parent-cell membranes but in different proportions. The 15B membranes have 28% less sialic acid, 38% less N-acetylglucosamine, 49% less galactose, the same amount of N-acetylgalactosamine, and 53% more mannose than the membranes of the parent cells.

Studies of two subpopulations of human lymphocytes differing in responsiveness to concanavalin A

We have identified two populations of human lymphocytes differing in responsiveness to the plant mitogen concanavalin A (Con-A). When peripheral blood lymphocytes are passed through a nylon column a population of lymphocytes highly responsive to Con-A adheres to the fibers while a second population of cells relatively unresponsive to Con-A emerges from the column. The untreated peripheral blood lymphocytes are termed "unfiltered" cells while the lymphocytes which pass through the column are termed "filtered" cells. Under standard assay conditions the Con-A-stimulated DNA synthesis is 6.5-fold greater, and the percentage blast formation is four-to fivefold greater in the unfiltered than in the filtered population. Mixing unfiltered with filtered cells fails to induce responsiveness in the latter indicating that a "helper" cell is not involved. The failure of filtered cells to respond to Con-A is specific for that mitogen since both populations respond nearly equally to erythroagglutinating phytohemagglutinin (E-PHA) and the poke weed mitogen (PWM). Binding studies with Con-A-(131)I demonstrate that the unfiltered population possesses approximately three times as many Con-A receptor sites per cell as the filtered cells, although both cell populations bind the mitogen with the same affinity (apparent association constant [K] of 1.67 x 10(6)m(-1)). The relationship between Con-A binding and lymphocyte activation was determined by measuring the effect on DNA synthesis of incubating the two lymphocyte populations with increasing amounts of Con-A. The concentration of Con-A required for half-maximal stimulation of DNA synthesis was 5-14 times greater for the filtered cells. However in the presence of very high Con-A concentrations the filtered cells achieved a maximal rate of DNA synthesis approaching that of the unfiltered population. These data implicate the decreased number of Con-A receptor sites on the filtered cells in their failure to respond to low concentrations of Con-A. A crucial event in the activation of lymphocytes by plant mitogens may be the binding of a critical number of the mitogen molecules to the cell surface.