Negative Growth Factors Research Articles

Economic psychology for laymen

Neuroeconomics can now replace the Paradigm of Bounded Rationality (BR) by a rooting in positivist economic psychology. The key finding is that the neuroeconomic Model of Decision-Making (NeM), based on neuroeconomic trials, suspends subjectivism, identifying risk-willingness as a basal parameter of economic behavior. Further, NeM and behavioral psychology (Big5 Taxonomy) integrates correlation studies into an Economic Psychology that simplifies Sensi-training in the Big5 to persons without specialism in Psychology. Finally, this Economic Psychology implicates a new interdisciplinary outlook on three domains of Economics: Evidence of the Florida Thesis on the Rise of the Creative Class as a qualitative growth effect A positivist framework for modern stress-management by classical meditative in-depth relaxation Recognition of prejudices as a special problem of behavioral science due to the interaction of subject and object Discussion focuses on the significance to economic growth theory to abandon BR. The conclusion is, that the simple model of accounting real growth in GDP, must be replaced by a tripartite model already termed 3P in management research (Planet, Personnel and Profit) including negative growth factors, too. The 3P has a common outcome in Quality-Adjusted Life Years (QALY) which at the global level has a negative aggregated value in the 21 Century. So, political measures to counterbalance, for instance the damage to the climate, are discussed concluding an urgent need for a global CO2 Tariff (ET).

Analysis of combustion instability of hydrogen fueled scramjet combustor on high-speed OH-PLIF measurements and dynamic mode decomposition

This paper investigated the combustion instability of spanwise positions in a hydrogen fueled scramjet combustor with a cavity flame holder. High-speed OH-PLIF technique was performed on a direct-connect supersonic combustion facility, and dynamic mode decomposition (DMD) as postprocessing. Combustion instability was investigated by characterizing the dominant frequencies and growth factors. By changing the equivalence ratio of hydrogen, the peak frequencies of scramjet mode and ramjet mode were obtained. Scramjet mode tended to have small oscillation at 150–200 Hz reflected by negative growth factors due to the stable flame structure. At ram-to-scram transition, oscillations at 80–120 Hz were remarkably enhanced due to the positive growth factors. In ramjet mode, the large differences of frequency characteristics in spanwise positions were observed. The dominant DMD modes near the cavity wall appeared to have negative growth factors leading to a stable flame with small oscillations. Besides, the characteristics of frequency-shift were affected by the positions of injector.

A novel oleanolic acid derivative HA-19 ameliorates muscle atrophy via promoting protein synthesis and preventing protein degradation

Muscle atrophy refers to a decrease in the size of muscles in the body, occurs in certain muscles with inactivity in many diseases and lacks effective therapies up to date. Natural products still play an important role in drug discovery. In the present study, derivatives of a natural product, oleanolic acid, were screened with myoblast differentiation and myotube atrophy assays, respectively. Results revealed that one of the derivatives, HA-19 showed the most potent anti-muscle atrophy activity, and was used for further studies. We demonstrated that HA-19 led to the increase of the protein synthesis by activating mechanistic target of rapamycin complex 1 (mTORC1)/p70 S6K pathways, and also enhanced myoblast proliferation and terminal differentiation via up-regulating of the myogenic transcription factors Pax7, MyoD and Myogenin. The interesting thing was that HA-19 also suppressed protein degradation to prevent myotube atrophy by down-regulating negative growth factors, FoxO1, MuRF1 and Atrogin-1. The results were also supported by puromycin labelling and protein ubiquitination assays. These data revealed that HA-19 possessed a “dual effect” on inhibition of muscle atrophy. In disuse-induced muscle atrophy mice model, HA-19 treatment significantly increased the weights of bilateral tibialis anterior (TA), gastrocnemius (Gastroc.), quadriceps (Quad.), suggesting the effectiveness of HA-19 to remit disuse-induced muscle atrophy. Our finding demonstrated that HA-19 has a great potential as an inhibitor or lead compound for the anti-muscle atrophy drug discovery.

The Effect of Polydeoxyribonucleotide on Chronic Non-healing Wound of an Amputee: A Case Report.

Polydeoxyribonucleotide (PDRN) is safe and effective in wound healing, cellular growth, synthesis of extracellular matrix protein, and inflammation reduction via activation of adenosine A2 receptors. We report a 28-year-old male patient treated with PDRN injections for chronic non-healing wound refractory to negative pressure wound therapy, skin graft, or growth factors. Three injections of PDRN were administered at the wound site into the anterior and medial sides of the left stump on the 1st, 4th, and 9th days of hospitalization. The PDRN ameliorated wound healing by enhancing cell growth, tissue repair, and angiogenesis. PDRN application represents a potential treatment for non-healing wounds obviating the need for additional therapies, and hospitalization, as well as improve patient’s activities of daily living.

Dressings and topical agents for treating venous leg ulcers.

Venous leg ulcers are open skin wounds on the lower leg which can be slow to heal, and are both painful and costly. The point prevalence of open venous leg ulcers in the UK is about 3 cases per 10,000 people, and many people experience recurrent episodes of prolonged ulceration. First-line treatment for venous leg ulcers is compression therapy, but a wide range of dressings and topical treatments are also used. This diversity of treatments makes evidence-based decision-making challenging, and a clear and current overview of all the evidence is required. This review is a network meta-analysis (NMA) which assesses the probability of complete ulcer healing associated with alternative dressings and topical agents.To assess the effects of (1) dressings and (2) topical agents for healing venous leg ulcers in any care setting and to rank treatments in order of effectiveness, with assessment of uncertainty and evidence quality.In March 2017 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also scanned reference lists of relevant included studies as well as reviews, meta-analyses, guidelines and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting. We updated this search in March 2018; as a result several studies are awaiting classification.We included published or unpublished randomised controlled trials (RCTs) that enrolled adults with venous leg ulcers and compared the effects of at least one of the following interventions with any other intervention in the treatment of venous leg ulcers: any dressing, or any topical agent applied directly to an open venous leg ulcer and left in situ. We excluded from this review dressings attached to external devices such as negative pressure wound therapies, skin grafts, growth factors and other biological agents, larval therapy and treatments such as laser, heat or ultrasound. Studies were required to report complete wound healing to be eligible.Two review authors independently performed study selection, 'Risk of bias' assessment and data extraction. We conducted this NMA using frequentist meta-regression methods for the efficacy outcome; the probability of complete healing. We assumed that treatment effects were similar within dressings classes (e.g. hydrocolloid, foam). We present estimates of effect with their 95% confidence intervals (CIs) for individual treatments focusing on comparisons with widely used dressing classes, and we report ranking probabilities for each intervention (probability of being the best, second best, etc treatment). We assessed the certainty (quality) of the body of evidence using GRADE for each network comparison and for the network as whole.We included 78 RCTs (7014 participants) in this review. Of these, 59 studies (5156 participants, 25 different interventions) were included in the NMA; resulting in 40 direct contrasts which informed 300 mixed-treatment contrasts.The evidence for the network as a whole was of low certainty. This judgement was based on the sparsity of the network leading to imprecision and the general high risk of bias in the included studies. Sensitivity analyses also demonstrated instability in key aspects of the network and results are reported for the extended sensitivity analysis. Evidence for individual contrasts was mainly judged to be low or very low certainty.The uncertainty was perpetuated when the results were considered by ranking the treatments in terms of the probability that they were the most effective for ulcer healing, with many treatments having similar, low, probabilities of being the best treatment. The two most highly-ranked treatments both had more than 50% probability of being the best (sucralfate and silver dressings). However, the data for sucralfate was from one small study, which means that this finding should be interpreted with caution. When exploring the data for silver and sucralfate compared with widely-used dressing classes, there was some evidence that silver dressings may increase the probability of venous leg ulcer healing, compared with nonadherent dressings: RR 2.43, 95% CI 1.58 to 3.74 (moderate-certainty evidence in the context of a low-certainty network). For all other combinations of these five interventions it was unclear whether the intervention increased the probability of healing; in each case this was low- or very low-certainty evidence as a consequence of one or more of imprecision, risk of bias and inconsistency.More research is needed to determine whether particular dressings or topical agents improve the probability of healing of venous leg ulcers. However, the NMA is uninformative regarding which interventions might best be included in a large trial, largely because of the low certainty of the whole network and of individual comparisons.The results of this NMA focus exclusively on complete healing; whilst this is of key importance to people living with venous leg ulcers, clinicians may wish to take into account other patient-important outcomes and factors such as patient preference and cost.

Abstract 2971: The prognostic relevance of inflammatory cytokines and growth factors elaborated from adipose-derived stem cells in breast cancer

Abstract Introduction: Given the high rates of obesity and aggressive breast cancers, it is paramount to understand how adipose tissue supports the tumor microenvironment. We previously found that adipose-derived stem cells cultured with triple-negative tumor cells enhanced the expression of numerous pro-inflammatory cytokines. This finding is significant as it could explain, in part, how obesity contributes to worse outcomes in breast cancer. To further expand this study, we probed the Cancer Genome Atlas (TCGA) breast invasive carcinoma dataset for the expression profiles of the inflammatory cytokines we found to be highly up-regulated in vitro. We predicted TCGA data would demonstrate a correlation between cytokine overexpression and worse clinical scenarios. Methods: Cytokines and growth factors were measured in the media of adipose stromal cells and MDA-MB-231 tumor cells via membrane-based antibody array. To validate clinical significance, we compared each cytokine’s mRNA expression profile, available from primary tumor samples of TCGA breast invasive carcinoma dataset (n = 1,005), to indices of tumor progression and survival status. For survival analysis, samples were dichotomized as high or low expression by individual cytokines (z score ≥ 1.5). Cytokine and growth factor expression was further stratified according to molecular subtype of breast cancer (luminal A, luminal B, HER2, triple negative) and receptor status. Ingenuity pathway analysis (IPA) was performed to identify candidate markers related to obesity or inflammation. Results: High levels of FGF7 and CCL5 protein were found in the conditioned media of tumor and adipose stem cell co-cultures and together they showed a significant impact on breast cancer survival within TCGA data. FGF7, CCL5, together with CCL2, IL6, and IL6R were further analyzed for expression across molecular subtypes of breast cancer. IL6R, CCL5, and CCL2 expression varied significantly between breast cancer subtypes, with mean expression highest in triple-negative tumors. After dichotomizing the samples for estrogen receptor status, IL6R, CCL5, and CCL2 showed significantly higher mean expression in ER negative tumors. Greater expression of these cytokines in tumors was correlated with reduced patient survival in triple-negative tumors and ER negative subtypes. IPA analysis indicated IL6, IL6R, CCL5, and CCL2, but not FGF7, cooperate through inflammatory pathways to promote tumor progression. Conclusions: Genomic data analysis supports in vitro findings that IL6R, CCL5, and CCL2 overexpression, either independently or synergistically, predict a worse prognosis in breast cancer. For adipose-driven, hormone receptor negative breast tumors, these cytokines and growth factors could serve as novel therapeutic targets. (Supported by NIH P20GM103434 and NIGMS U54GM104942) Citation Format: Nicole Werwie, Kelsey Sadlek, Eric Lundstrom, Daniel Berrebi, Gerald Hobbs, Linda Vona-Davis. The prognostic relevance of inflammatory cytokines and growth factors elaborated from adipose-derived stem cells in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2971. doi:10.1158/1538-7445.AM2017-2971

Highlights of This Issue

Metabolomics captures the interactions between genetic alterations, enzymatic activity, and metabolic reactions. Here, comparative mass spectrometry-based metabolomics was performed using matched frozen and fixed isogenic prostate cancer cells and clinical specimens. A sufficient number of metabolites were retained in formalin-fixed, paraffin-embedded (FFPE) tissue to allow unsupervised hierarchical clustering of cell populations. This metabolomic profiling approach creates the opportunity, for research and diagnostic purposes, to interrogate annotated tumor banks retrospectively and link metabolomics with clinicopathologic endpoints. Combined, metabolic profiling to discover and validate metabolism-based diagnostic, prognostic or predictive biomarkers in archival diagnostic tissue adds a new, powerful technology for precision medicine.A critical aspect of metastatic epithelial ovarian cancer (EOC) is tumor cell dormancy, rendering these cells resistant to chemotherapeutics. Employing a systematic approach to analyze the role of negative growth factors, MacDonald and colleagues demonstrate that disruption of the DP, RB family, E2F, and MuvB complex (DREAM) results in death of EOC cells. Specifically, loss of the DREAM assembly factor Dyrk1A, or the DREAM component p130, impairs repression of DREAM target genes, leads to continued DNA synthesis, and is coincident with increased cell death. Importantly, chemical inhibition of Dyrk1A synergizes with conventional chemotherapies to kill EOC cells under dormant conditions.The basis of resistance or sensitivity to irinotecan in colorectal cancer has still not been clearly established. Strategies to identify susceptible patients and targetable pathways to reverse resistance are urgently needed. Cabal-Hierro and O’Dwyer highlight a role for RIP1 kinase in SN38 sensitivity by mediating cell death/DNA damage signaling in colon adenocarcinoma model systems through the TNF/TNFR pathway. Downregulation of RIP1 protects from SN-38 in vitro and in vivo, suggesting that RIP1 has potential as a biomarker. Activation of TNF/TNFR signaling potentiates SN38 activity in a RIP1-dependent manner; thus, suggesting a re-evaluation of TNF-based interventions to enhance treatment efficacy.Early metastasis and therapeutic resistance are huge setbacks to patients diagnosed with pancreatic ductal adenocarcinoma (PDAC). Here, Smigiel and colleagues report a unique function of the tumor microenvironment (TME) cytokine oncostatin M (OSM) in inducing epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) properties in pancreatic cancer cells. Elevated levels of OSM in PDAC induce EMT transcription factors ZEB1 and Snail, and induce CD44+ CSC that are more migratory, tumorigenic, highly metastatic and resistant to gemcitabine. As such, targeting OSM or OSM-signaling in PDAC is a potential therapeutic strategy to prevent de novo acquisition of CSC properties such as drug resistance and metastasis.

Literature review on the management of diabetic foot ulcer.

Diabetic foot ulcer (DFU) is the most costly and devastating complication of diabetes mellitus, which affect 15% of diabetic patients during their lifetime. Based on National Institute for Health and Clinical Excellence strategies, early effective management of DFU can reduce the severity of complications such as preventable amputations and possible mortality, and also can improve overall quality of life. The management of DFU should be optimized by using a multidisciplinary team, due to a holistic approach to wound management is required. Based on studies, blood sugar control, wound debridement, advanced dressings and offloading modalities should always be a part of DFU management. Furthermore, surgery to heal chronic ulcer and prevent recurrence should be considered as an essential component of management in some cases. Also, hyperbaric oxygen therapy, electrical stimulation, negative pressure wound therapy, bio-engineered skin and growth factors could be used as adjunct therapies for rapid healing of DFU. So, it's suggested that with appropriate patient education encourages them to regular foot care in order to prevent DFU and its complications.

Do neuro‐humoral signaling molecules participate in colorectal carcinogenesis/cancer progression?

AbstractSignaling molecules in the gastrointestinal (GI) tract, as released from intrinsic, or extrinsic neurons, or from local endocrine cells may serve as positive or negative growth factors, and it has been suggested that such could participate also in colorectal carcinogenesis/cancer progression. Sporadic colorectal cancer arises from an initially benign adenoma, which, in turn, develops from the stem cell compartment, located in the bottom of the crypts of the colorectal mucosa. It was recently demonstrated in rat that intrinsic denervation of the colon appeared to be protective against chemically induced carcinogenesis. Of the various GI signaling molecules, noradrenaline (NA) and substance P (SP) may be of particular importance as growth factors involved in colorectal cancer. In the current issue of Neurogastroenterology and Motility, Graf et al. demonstrate that in benign, human colon polyps, there was a loss of innervation compared with adjacent mucosa, affecting efferent, noradrenergic, as well as sensory, SP‐ergic fibers, while there was an increase in SP‐immunoreactive non‐neuronal cells in the polyps. The results obtained could suggest that loss of mucosal innervation, due to e.g. luminal, pro‐inflammatory stimuli, could result in unbalanced pro‐tumorigenic stimulation of the stem cell region by non‐neuronal SP. The current findings may be important for the further understanding of the development of sporadic colorectal cancer.

Retraction: Myostatin Induces Degradation of Sarcomeric Proteins through a Smad3 Signaling Mechanism During Skeletal Muscle Wasting

Ubiquitination-mediated proteolysis is a hallmark of skeletal muscle wasting manifested in response to negative growth factors, including myostatin. Thus, the characterization of signaling mechanisms that induce the ubiquitination of intracellular and sarcomeric proteins during skeletal muscle wasting is of great importance. We have recently characterized myostatin as a potent negative regulator of myogenesis and further demonstrated that elevated levels of myostatin in circulation results in the up-regulation of the muscle-specific E3 ligases, Atrogin-1 and muscle ring finger protein 1 (MuRF1). However, the exact signaling mechanisms by which myostatin regulates the expression of Atrogin-1 and MuRF1, as well as the proteins targeted for degradation in response to excess myostatin, remain to be elucidated. In this report, we have demonstrated that myostatin signals through Smad3 (mothers against decapentaplegic homolog 3) to activate forkhead box O1 and Atrogin-1 expression, which further promotes the ubiquitination and subsequent proteasome-mediated degradation of critical sarcomeric proteins. Smad3 signaling was dispensable for myostatin-dependent overexpression of MuRF1. Although down-regulation of Atrogin-1 expression rescued approximately 80% of sarcomeric protein loss induced by myostatin, only about 20% rescue was seen when MuRF1 was silenced, implicating that Atrogin-1 is the predominant E3 ligase through which myostatin manifests skeletal muscle wasting. Furthermore, we have highlighted that Atrogin-1 not only associates with myosin heavy and light chain, but it also ubiquitinates these sarcomeric proteins. Based on presented data we propose a model whereby myostatin induces skeletal muscle wasting through targeting sarcomeric proteins via Smad3-mediated up-regulation of Atrogin-1 and forkhead box O1.

Functional inhibition of PI3K by the βGBP molecule suppresses Ras–MAPK signalling to block cell proliferation

The mechanisms of signal transduction from cell surface receptors to the interior of the cell are fundamental to the understanding of the role that positive and negative growth factors play in cell physiology and in human diseases. Here, we show that a functional link between phosphatidylinositol-3-OH kinase (PI3K) and Ras is suppressed by the beta-galactoside binding protein (betaGBP) molecule, a cytokine and a negative cell-cycle regulator. Ras-mitogen-activated protein kinase (MAPK) signalling is blocked by betaGBP owing to its ability to inhibit the p110 catalytic subunit of PI3K, whose basal activity is required for Ras activation. Functional inhibition of p110 by betaGBP results in downregulation of PI3K activity, suppression of Ras-GTP loading, consequent loss of MAPK activation and block of cell proliferation. This study sheds light on the molecular mechanisms whereby betaGBP can control cell proliferation and, by extension, may potentially control tumorigenesis by controlling PI3K.

TGF-β superfamily members modulate growth, branching, shaping, and patterning of the ureteric bud

Protein-rich fractions inhibitory for isolated ureteric bud (UB) growth were separated from a conditioned medium secreted by cells derived from the metanephric mesenchyme (MM). Elution profiles and immunoblotting indicated the presence of members of the transforming growth factor-β (TGF-β) superfamily. Treatment of cultured whole embryonic kidney with BMP2, BMP4, activin, or TGF-β1 leads to statistically significant differences in the overall size of the kidney, the number of UB branches, the length and angle of the branches, as well as in the thickness of the UB stalks. Thus, the pattern of the ureteric tree is altered. LIF, however, appeared to have only minimal effect on growth and development of the whole embryonic kidney in organ culture. The factors all directly inhibited, in a concentration-dependent fashion, the growth and branching of the isolated UB, albeit to different extents. Antagonists of some of these factors reduced their inhibitory effect. Detailed examination of TGF-β1-treated UBs revealed only a slight increase in the amount of apoptosis in tips by TUNEL staining, but diminished proliferation throughout by Ki67 staining. These data suggest an important direct modulatory role for BMP2, BMP4, LIF, TGF-β1, and activin (as well as their antagonists) on growth and branching of the UB, possibly in shaping the growing UB by playing a role in determining the number of branches, as well as where and how the branches occur. In support of this notion, UBs cultured in the presence of fibroblast growth factor 7 (FGF7), which induces the formation of globular structures with little distinction between the stalk and ampullae [Mech. Dev. 109 (2001) 123], and TGF-β superfamily members lead to the formation of UBs with clear stalks and ampullae. This indicates that positive (i.e., growth and branch promoting) and negative (i.e., growth and branch inhibiting) modulators of UB morphogenesis can cooperate in the formation of slender arborized UB structures similar to those observed in the intact developing kidney or in whole embryonic kidney organ culture. Finally, purification data also indicate the presence of an as yet unidentified soluble non-heparin-binding activity modulating UB growth and branching. The data suggest how contributions of positive and negative growth factors can together (perhaps as local bipolar morphogenetic gradients existing within the mesenchyme) modulate the vectoral arborization pattern of the UB and shape branches as they develop, thereby regulating both nephron number and tubule/duct caliber. We suggest that TGF-β-like molecules and other non-heparin-binding inhibitory factors can, in the appropriate matrix context, facilitate “braking” of the branching program as the UB shifts from a rapid branching stage (governed by a feed-forward mechanism) to a stage where branching slows down (negative feedback) and eventually stops.

Calcitonin receptor isoforms expressed in the developing rat kidney

Development in the metanephric-kidney transition period involves the precise expression of paracrine and autocrine events in an ordered spatio-temporal manner. Expression of these molecular events is tightly controlled and includes positive and negative growth factors and cognate receptors within close proximity in developing structures in the expanding renal cortex and medulla. The expression of calcitonin receptor (CTR) isoforms C1a and C1b in this context has not previously been described. Our current study also explored the relationship between the expression of CTR isoforms and amylin binding sites. Techniques included immunohistochemistry with novel antibodies that detect CTR isoforms, real time PCR for the quantification of CTR isoforms, Western blot and in vitro autoradiography, on tissues from embryo day 18 to postnatal day 30. The CTR C1a isoform is expressed in the ureteric ducts of the metanephros and both isoforms are expressed in the developing distal convoluted tubules, ascending limbs of the loop of Henle and collecting ducts in the postnatal rat kidney. There was a 60-fold excess of C1a versus C1b isoforms. An apparent molecular weight of 63 kD was found. In vitro autoradiography demonstrated that while amylin binding sites were predominantly in the cortex, CTR expression was largely localized in the medulla in an earlier event, followed by cortical expression. CTR C1a protein expression has been identified in the ureteric ducts in the metanephros and both isoforms expressed in the distal portions of the developing nephrons and collecting ducts. Since amylin binding sites have been localized on the proximal tubules of the cortex, it is unlikely that amylin receptors can be represented by modification of CTR affinity with receptor activity modifying proteins in the kidney.

EPITHELIAL GROWTH OF THE SMALL INTESTINE OCCURS BY BOTH CRYPT FISSION and CRYPT HYPERPLASIA DURING INFANCY and CHILDHOOD IN HUMANS

Our previous study has shown physiological crypt hyperplasia during infancy. Another mechanism of epithelial growth is crypt fission but this has not been investigated in humans. During crypt fission, crypts divide by unzipping from the base. A founder crypt divides into two daughter crypts with duplication of stem cells in the base. We investigated both crypt fission and crypt hyperplasia in infants (aged < 2 years, n = 4), children (aged 2–10 years, n = 7) and adults (n = 14) who had endoscopy for irritability/reflux oesophagitis in whom intestinal disease was unlikely. Duodenal biopsies were taken during endoscopy and villus area, crypt length, mitotic count per crypt and percentage of bifid crypts (a measure of crypt fission) were assessed by a microdissection technique. Villus area and crypt length correlate with villous and crypt enterocyte population, respectively. Mean ± SE villus area in infants, children and adults was 0.298 ± 0.009 mm2, 0.251 ± 0.029 mm2, and 0.257 ± 0.024 mm2, respectively, although no biopsies were available from neonates or infants < 6 months of age. Mean ± SE crypt length in infants, children, and adults was 284 ± 6, 299 ± 16 and 208 ± 13 μm, respectively. Mean ± SE mitotic count per crypt in infants, children and adults was 4.2 ± 0.1, 4.3 ± 0.8 and 2.1 ± 0.3, respectively. Thus, physiological crypt hyperplasia was present in both infants and children with longer crypts and higher proliferation of crypt cells. The mean ± SE percentage of bifid crypts in infants, children and adults was 9.1 ± 1.0, 5.0 ± 0.9 and 1.8 ± 0.5%, respectively. We conclude that crypt fission is predominantly elevated during infancy and to a lesser extent during childhood, whereas crypt hyperplasia is elevated equally during both infancy and childhood. We speculate this is due to differences in gene expression of positive and negative growth factors and their receptors.

Action of polypeptide growth factors in colon cancer development of new therapeutic approaches

There has been no significant improvement in the treatment of metastatic colon cancer over the last four decades. A major reason for therapeutic failure is the nonselective nature of conventional chemotherapy. Therefore, new selective therapeutic approaches must be explored to improve survival. Recent advances in cell and molecular biology have opened up new avenues of developing selective molecular therapy for colon cancer. In view of the heterogeneity of cells in colon cancer, it is likely that the use of more than one cellular target will be required to achieve a significant antitumor response. Mechanistic studies of how proliferation, differentiation and malignant properties are controlled by negative growth factors, positive growth factors and adhesion molecules have allowed the identification of several molecular targets of attack in colon cancer. Disruption of one or more of these targets should have a highly antiproliferative and/or cytotoxic effect on colon cancer cells. Additionally, disrupting the expression of these targets may augment sensitivity to conventional chemotherapy. In this article, we will discuss how polypeptide growth factors act in colon cancer cells, identify several molecular targets of attack and discuss strategies for selective disruption of these targets in colon cancer. Where appropriate, the biologic similarities or differences by comparison with other types of tumor will also be discussed.

Cell proliferation and regulation of negative growth factors in mouse liver foci.

Foci of altered hepatocytes are preneoplastic lesions capable of progressing to hepatocellular carcinomas. To characterize the growth of preneoplastic hepatic lesions, size of hepatic foci was analyzed with regard to growth factor regulation and hepatocyte proliferation in focal and non-focal hepatocytes. Twelve-day-old female B6C3F1 mice were initiated with a single dose of the potent mutagen N-nitrosodiethylamine (DEN) (5 mg/kg body weight). Beginning at 6 weeks of age, mice were exposed for 16 weeks to 2038 p.p.m. unleaded gasoline (UG) vapor or 1 p.p.m. ethinyl estradiol (EE) in the diet. Analysis of hepatic foci demonstrated that UG significantly increased, but EE significantly decreased the size of DEN-initiated foci. Hepatic labeling index (LI), as measured by the incorporation of 5-bromo-2'-deoxyuridine, was similar in non-focal hepatocytes at 16 weeks in all groups (0.4-0.8%) and greatly increased in hepatic foci. Hepatocyte LI was significantly increased in DEN/UG foci (29%, n = 41) and significantly decreased in DEN/EE foci (6%, n = 23) relative to DEN/control focal hepatocytes (18%, n = 25). The mean LI of foci correlated with the focal size differences observed in the treatment groups. Immunohistochemical analysis with antibodies directed to the negative growth regulator transforming growth factor-beta 1 (TGF-beta1) demonstrated a consistent decrease of TGF-beta 1 in DEN/Ct and DEN/UG hepatic foci relative to non-lesion hepatocytes. Similar results were seen with mannose 6-phosphate/insulin-like growth factor-II receptor (M6P/IGF-II R), which facilitates activation of latent TGF-beta 1. In contrast, only 50% of DEN/EE foci had decreased levels of TGF-beta 1 and M6P/IGF-II R relative to non-focal hepatocytes. These data suggest that proliferative responses observed in hepatic foci may be correlated with foci size. In contrast, chemically induced proliferative responses in non-focal hepatocytes after subchronic exposure cannot necessarily be used to predict proliferative effects in preneoplastic cell populations. Furthermore, these studies suggest that hepatic foci may occur by M6P/IGF-II R enhancing activation of latent TGF-beta 1 in non-focal hepatocytes but not in the focal hepatocytes, thereby affording focal hepatocytes a selective growth advantage.

Regulation of DNA synthesis of myocardial and epicardial cells in developing rat heart by [Met5]enkephalin.

Endogenous opioids serve as negative growth factors in neural and nonneural tissues in addition to being neuromodulators. This study investigated the hypothesis that native opioid peptides are inhibitory growth factors in heart development. DNA synthesis of ventricular myocardial and epicardial cells in 1-day-old rats was examined. Administration of a variety of opioids and peptides revealed that [Met5]enkephalin had the greatest inhibitory effect on DNA synthesis; peptides related to mu-, delta-, kappa-, epsilon-, and sigma-receptors had no influence on cell proliferation, even at concentrations as high as 10 mg/kg. [Met5]enkephalin, also termed opioid growth factor (OGF), depressed DNA synthesis at 1 and 10 mg/kg but not at 0.01 or 0.1 mg/kg. The effects of OGF were noted within 1 h of treatment, persisted for as long as 22 h after drug administration, and could depress DNA synthesis in myocardial and epicardial cells to 43 and 36%, respectively, of control values. The effect of OGF on DNA synthesis of heart cells was opioid receptor-mediated. Organ culture experiments revealed that opioids acted directly on developing cardiac cells. Both OGF and its receptor, zeta, were detected in heart cells of 1-day-old rats by immunocytochemistry. mRNA for preproenkephalin, the precursor to OGF, was observed in 1-day-old rat heart. These results indicate that an autocrine- or paracrine-produced endogenous opioid peptide (i.e., OGF) and its receptor (i.e., zeta) are present in the developing heart and govern DNA synthesis, with OGF acting directly as a tonic negative regulator of cell generation.

The Opioid Growth Factor, [Met5]-Enkephalin, and the ζ(Zeta) Opioid Receptor Are Present in Human and Mouse Skin and Tonically Act to Inhibit DNA Synthesis in the Epidermis

Opioid peptides serve as tonically active negative growth factors in neural and non-neural cells, in addition to being neuromodulators. To investigate the involvement of opioids in homeostatic renewal of epithelial cells in the epidermis, mice were given systemic injections of the potent opioid antagonist, naltrexone (NTX) (20 mg/kg). Disruption of opioid-receptor interaction by NTX resulted in an elevation of 42 and 72% in DNA synthesis in skin from the dorsum and plantar surface of the hindfoot, respectively, within 2 h; response to NTX was dependent on the circadian rhythm in each region examined. Injection of the naturally occurring and potent opioid growth factor (OGF), [Met5]-enkephalin, at 1 mg/kg depressed DNA synthesis in the dorsum and plantar surface by 42 and 19%, respectively, within 2 h; the effects of OGF complied with the pattern of circadian rhythm in each area of skin. The decreases in labeling index evoked by OGF were blocked by concomitant administration of the opioid antagonist, naloxone (10 mg/kg); naloxone alone at the dosage utilized had no influence on cell replicative processes. In tissue culture studies, OGF and NTX respectively depressed and elevated DNA synthesis. Both OGF and its receptor, zeta, were detected in all but the cornified layer of the epidermis in murine skin from the dorsum, plantar surface, pinnae, and tail. In addition, both peptide and receptor were observed in basal and suprabasal cells of the human epidermis. These results lead to the suggestion that an endogenous opioid peptide and its receptor are present and govern cellular renewal processes in the skin in a direct manner, regulating DNA synthesis in a tonically inhibitory, circadian rhythm-dependent fashion.

Growth factor balance and tumor progression

The role of balance of negative and positive autocrine growth factors in malignant progression is reviewed with an emphasis on transforming growth factor alpha (TGF-alpha) as a stimulating factor and transforming growth factor beta (TGF-beta) as an inhibiting factor. Evidence suggests that in normal cells TGF-alpha is down regulated in non-dividing or quiescent states in vitro. Tumor cells which have early stage characteristics as represented by poor clonal growth and poor tumorigenicity in athymic mice also show repression of TGF-alpha in non-dividing states. Progression of this phenotype is induced by uncontrolled low level expression of TGF-alpha by transfection with a constitutive expression vector for the polypeptide. Transfection of the unprogressed phenotype with a constitutive anti-sense vector for TGF-beta, also leads to tumor progression by repressing the autocrine negative TGF-beta activity normally expressed by these cells. Both the upregulation of TGF-alpha and the repression of TGF-beta generated in vivo progression without changing growth rates in vitro. Instead, clonality and ability to reenter the cell cycle from quiescence were increased. Thus, it is concluded that an autocrine balance of positive and negative factors is important for maintaining controlled re-entry into dividing states from non-dividing states and that disruption of this balance leads to malignant progression characterized by greater independence of the malignant cells from the control of exogenous growth factors.

Growth factor independence and growth regulatory pathways in human melanoma development

This review concentrates on growth autonomy of tumor cells in relation to tumor progression. Human malignant melanoma serves as an example for progressive growth factor independence at subsequent stages of tumor progression. Mechanisms by which malignant cells acquire growth factor independence are discussed. In melanoma, deregulation of growth regulatory pathways has been described on four levels: 1) aberrant production of autocrine growth factors that substitute for exogenous growth factors (basic fibroblast growth factor [bFGF]); 2) alterations in the response to negative autocrine growth factors (interleukin [IL]-6 and transforming growth factor [TGF]-beta); 3) overexpression of epidermal growth factor receptors (EGF-R); and 4) alterations of cellular protooncogenes involved in signal transduction (RAS, MYB) and growth suppression (p53). In addition to bFGF and IL-6, multiple other growth factor genes are activated in malignant melanoma cells but not normal melanocytes. These include both chains of platelet-derived growth factor (PDGF), TGF-alpha, IL-1, IL-8, and tumor necrosis factor (TNF)-alpha. Of these, PDGF-B has been investigated in more detail. Melanoma-derived PDGF clearly does not act in a direct autocrine mode, but has important paracrine effects on normal tissue constituents, notably fibroblasts and endothelial cells, that are essential for tumor development in vivo. It is speculated that other melanoma-derived growth factors with as yet undefined functions similarly exert such paracrine or 'indirect' autocrine effects that cannot be sufficiently addressed in studies on cultured cells.