Competency-based assessment for the training of PhD students and early-career scientists.

The training of PhD students and early-career scientists is largely an apprenticeship in which the trainee associates with an expert to become an independent scientist. But when is a PhD student ready to graduate, a postdoctoral scholar ready for an independent position, or an early-career scientist ready for advanced responsibilities? Research training by apprenticeship does not uniformly include a framework to assess if the trainee is equipped with the complex knowledge, skills and attitudes required to be a successful scientist in the 21 century. To address this problem, we propose competency-based assessment throughout the continuum of training to evaluate more objectively the development of PhD students and early-career scientists.

Targeted overexpression of OGFr in epithelium of transgenic mice suppresses cell proliferation and impairs full-thickness wound closure.

The opioid growth factor (OGF) and its receptor, OGFr, play a regulatory role in cell proliferation, and maintain homeostasis through a tonically active negative feedback mechanism. To directly evaluate the repercussion of increased OGFr expression and consequent gain-of-function in epithelium, bovine keratin 5 promoter elements were used to direct the expression of OGFr to skin in a tetracycline-regulated manner. Three founder lines overexpressing OGFr (OGFrTG/K5-tTA) were established.

Effects of fish oil and Tamoxifen on preneoplastic lesion development and biomarkers of oxidative stress in the early stages of N-methyl-N-nitrosourea-induced rat mammary carcinogenesis.

Epidemiologic studies on the protective role of omega-3 fatty acids (n:3) on breast cancer prevention remain inconclusive but studies in preclinical models provide more positive outcome. However, the mechanisms accounting for the protective effect of n:3 are not defined. In the present study, conducted in the N-methyl-N-nitrosourea-induced rat mammary carcinogenesis model, we examined the effects of n:3 individually and in combination with the anti-estrogen Tamoxifen (Tam) on a comprehensive panel of systemic and preneoplastic mammary gland restricted biomarkers which may be critical in the progression to invasive cancer.

The effects of Tamoxifen and fish oil on mammary carcinogenesis in polyoma middle T transgenic mice.

In these experiments, we tested the hypothesis that inhibition of the estrogen receptor (ER) with Tamoxifen and activation of PPARγ with fish oil (FO) rich in omega-3 (n-3; known PPAR agonists) inhibit the development of hormone-independent breast cancer in view of the known crosstalk between the ER and PPARγ pathways. We selected the polyoma middle T transgenic mouse model, since in this system the development of ER- tumors is preceded by ER positive preneoplastic lesions. Tamoxifen admixed with a 20% corn oil (CO) modified AIN-76A diet delayed mammary carcinogenesis and inhibited tumor multiplicity, volume, and weight in a dose-dependent (1, 10, and 100 ppm) fashion.

The impact of fish oil on the chemopreventive efficacy of tamoxifen against development of N-methyl-N-nitrosourea-induced rat mammary carcinogenesis.

The antiestrogen tamoxifen reduces breast cancer incidence in high-risk women but is unable to inhibit the development of hormone-independent tumors. Omega-3 polyunsaturated fatty acids (n-3 PUFA), known ligands of the peroxisome proliferator activated receptor-gamma (PPARgamma), generally exert tumor-suppressive effects. Based on the known crosstalk between the estrogen and the PPARgamma receptors, we tested the hypothesis that the combination of tamoxifen with n-3 PUFA results in a superior antitumor action over the individual interventions.

Dependence on nuclear localization signals of the opioid growth factor receptor in the regulation of cell proliferation.

The opioid growth factor receptor (OGFr) mediates the inhibitory action of OGF on cell replication of normal and neoplastic cells. The spatiotemporal course of OGFr nucleocytoplasmic trafficking was determined with a probe of full-length OGFr fused to enhanced green fluorescent protein (eGFP). Translation of OGFr required 8.

The OGF-OGFr axis utilizes the p16INK4a and p21WAF1/CIP1 pathways to restrict normal cell proliferation.

Opioid growth factor (OGF) is an endogenous opioid peptide ([Met(5)]enkephalin) that interacts with the OGF receptor (OGFr) and serves as a tonically active negative growth factor in cell proliferation of normal cells. To clarify the mechanism by which OGF inhibits cell replication in normal cells, we investigated the effect of the OGF-OGFr axis on cell cycle activity in human umbilical vein endothelial cells (HUVECs) and human epidermal keratinocytes (NHEKs). OGF markedly depressed cell proliferation of both cell lines by up to 40% of sterile water controls.

The OGF-OGFr axis utilizes the p21 pathway to restrict progression of human pancreatic cancer.

Background: Pancreatic cancer is the 4th leading cause of death from cancer in the U.S. The opioid growth factor (OGF; [Met5]-enkephalin) and the OGF receptor form an inhibitory growth regulatory system involved in the pathogenesis and treatment of pancreatic cancer.

Role of non-receptor and receptor tyrosine kinases (TKs) in the antitumor action of alpha-difluoromethylornithine (DFMO) in breast cancer cells.

We have shown that administration of alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), the first and rate-limiting enzyme in polyamine (PA) biosynthesis, reduces the invasive and metastatic properties of MDA-MB-435 breast cancer cells while activating multiple signal transduction pathways, including MAPK, Stat3, Stat1, and JNK. Since the activity of these signaling mechanisms is frequently regulated by upstream tyrosine kinases (TKs), we tested whether non-receptor and receptor TKs may be involved in the signaling and biological effects of DFMO in MDA-MB-435 cells. Treatment with DFMO (1 mM for 48 h) did not affect Src phosphorylation (Tyr 416).

The opioid growth factor (OGF)-OGF receptor axis uses the p16 pathway to inhibit head and neck cancer.

Head and neck squamous cell carcinoma (HNSCC) represents 5.5% of malignancies worldwide, with approximately 30,000 new cases and approximately 11,000 deaths reported in the United States annually. The opioid growth factor (OGF; [Met(5)]-enkephalin) and the OGF receptor (OGFr) form an endogenous growth regulating system; the OGF-OGFr axis influences the G(0)-G(1) phase of the cell cycle in HNSCC.

Effects of alpha-difluoromethylornithine on thrombospondin-1 production by human breast cancer cells.

We have previously observed that inhibition of polyamine biosynthesis with alpha-difluoromethylornithine (DFMO) upregulates production of thrombospondin-1 (TSP-1), an extracellular matrix protein with potent anti-angiogenic and antimetastatic properties, by MDA-MB-435 human breast cancer cells in culture. The present experiments were designed to investigate the mechanisms by which DFMO regulates TSP-1 production in this system. 35S-methionine pulse chase experiments indicated that DFMO administration increased TSP-1 synthesis by approximately 6-fold, while it slightly but significantly decreased protein half-life from 35 to 28 min.

The TATA binding protein associated factor 4b (TAF4b) mediates FSH stimulation of the IGFBP-3 promoter in cultured porcine ovarian granulosa cells.

We have established the gene for IGF binding protein-3 (IGFBP-3) as a target for FSH action. FSH effects on this gene require the PKA pathway as well as the PI-3 kinase and MAPK pathways. At the IGFBP-3 promoter, FSH effects depend on a site for TATA box binding protein (TBP) and formation of a high molecular weight transcription complex.

Effects of polyamine depletion by alpha-difluoromethylornithine on in vitro and in vivo biological properties of 4T1 murine mammary cancer cells.

Increased polyamine synthesis has been associated with proliferation and progression of breast cancer, and thus, is a potential target for anticancer therapy. Polyamine depletion by alpha-difluoromethylornithine (DFMO) has been shown to decrease pulmonary and bone metastasis from human breast cancer cell xenografts. Following these observations, this study was designed to test the effects of DFMO on in vitro and in vivo features of the highly invasive and metastatic 4T1 murine mammary cancer cells.

Activation of protein kinase A (PKA) signaling mitigates the antiproliferative and antiinvasive effects of alpha-difluoromethylornithine in breast cancer cells.

We have shown that alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, the first and rate-limiting enzyme in polyamine synthesis, has significant antiproliferative and antiinvasive effects in breast cancer cells. We have also reported that these antitumor effects are associated with activation of multiple signaling pathways, including STAT-3, STAT-1, Jun-N-Terminal kinase (JNK), and Mitogen activated protein kinase (MAPK), the latter being found to mediate its antiinvasive action in MDA-MB-435 cells. The present experiments were designed to test the effect of DFMO on the protein kinase A (PKA) pathway and determine its biological significance.

Overexpression of the opioid growth factor receptor potentiates growth inhibition in human pancreatic cancer cells.

The opioid growth factor (OGF), [Met5]-enkephalin, and OGF receptor (OGFr) form an inhibitory axis regulating the growth of human pancreatic cancer. This study examined whether overexpression of OGFr decreases the growth of pancreatic cells in vitro. MIA PaCa-2 cells were transfected with OGFr cDNA, and six clonal lines were examined for protein expression and function.

Overexpression of the opioid growth factor receptor downregulates cell proliferation of human squamous carcinoma cells of the head and neck.

The opioid growth factor (OGF) is a constitutively expressed negative growth regulator whose action is mediated by the OGF receptor (OGFr). The OGF-OGFr axis tonically regulates the growth of human squamous cell carcinoma of the head and neck (SCCHN). To examine the repercussions of amplifying OGFr in SCCHN, constructs were prepared to overexpress OGFr in SCC-1 cells; six clonal lines were examined.

Effects of polyamine depletion by alpha-difluoromethylornithine on in vitro and in vivo biological properties of 4T1 murine mammary cancer cells.

Increased polyamine synthesis has been associated with proliferation and progression of breast cancer, and thus, is a potential target for anti-cancer therapy. Polyamine depletion by DFMO has been shown to decrease pulmonary and bone metastasis from human breast cancer cell xenografts. Following these observations, this study was designed to test the effects of DFMO on in vitro and in vivo features of the highly invasive and metastatic 4T1 murine mammary cancer cells.

Interaction between Polyamines and the Mitogen-Activated Protein Kinase Pathway in the Regulation of Cell Cycle Variables in Breast Cancer Cells.

Inhibition of polyamine biosynthesis with alpha-difluoromethylornithine (DFMO) has been shown to inhibit proliferation of breast cancer cells although its mechanism of action has not been fully elucidated. To address this issue, we tested the effects of DFMO on cell cycle variables of MDA-MB-435 human breast cancer cells in culture. We also focused on the possible mediatory role of the mitogen-activated protein kinase (MAPK) pathway on the cell cycle effects of DFMO because this compound has been shown to activate MAPK signaling.

Effects of polyamine synthesis inhibitors on primary tumor features and metastatic capacity of human breast cancer cells.

We have previously reported that inhibition of polyamine biosynthesis with alpha-difluoromethylornithine (DFMO) reduces pulmonary metastasis from MDA-MB-435 human breast cancer xenografts without affecting the volume of the primary tumors (Manni et al. Clin Exp Mets 20:321, 2003). In these experiments, we show that DFMO treatment (2% in drinking H(2)O) reduced the growth fraction of the primary tumors by 60%.

Particle-mediated gene transfer of opioid growth factor receptor cDNA regulates cell proliferation of the corneal epithelium.

Purpose: This study was designed to determine at the molecular level whether interactions between the opioid growth factor (OGF) and OGF receptor (OGFr) play a role in regulating DNA synthesis in the homeostasis of the corneal epithelium.

Methods: The plasmid pcDNA3.1+OGFr-HA, carrying the rat OGFr cDNA epitope-tagged with a C-terminal hemagglutinin (HA), or the empty-vector (pcDNA3.

Combination chemotherapy with gemcitabine and biotherapy with opioid growth factor (OGF) enhances the growth inhibition of pancreatic adenocarcinoma.

Gemcitabine is the standard of care for advanced pancreatic neoplasia, and exerts its effect through inhibition of DNA synthesis. However, gemcitabine has limited survival benefits. Opioid growth factor (OGF) is an autocrine-produced peptide that interacts with the nuclear receptor, OGFr, to inhibit cell proliferation but is not cytotoxic or apoptotic.

Opioid growth factor enhances tumor growth inhibition and increases the survival of paclitaxel-treated mice with squamous cell carcinoma of the head and neck.

Paclitaxel is used as a single agent, and in combination with other drugs, as a standard of care in the treatment of squamous cell carcinoma of the head and neck (SCCHN). However, the use of paclitaxel for therapy of SCCHN may be accompanied by serious side effects. Paclitaxel is a known cytotoxic inhibitor of cell proliferation that acts by stabilizing microtubules and inducing apoptosis.

Follicle-stimulating hormone induction of ovarian insulin-like growth factor-binding protein-3 transcription requires a TATA box-binding protein and the protein kinase A and phosphatidylinositol-3 kinase pathways.

The current study was done to elucidate the mechanism of the FSH stimulation of IGF-binding protein 3 (IGFBP-3) expression and map the FSH response element on the pig IGFBP-3 promoter. Forskolin induced IGFBP-3 reporter activity in transiently transfected granulosa cells. The protein kinase A (PKA) inhibitor [N-[2-(p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide, 2HCl] (and cotransfection with a PKA inhibitor expression vector), the phosphatidylinositol-3 kinase inhibitor [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], and the ERK inhibitor [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene], all blocked FSH stimulation.

Enhanced growth inhibition of squamous cell carcinoma of the head and neck by combination therapy of paclitaxel and opioid growth factor.

This study evaluated the effects of a combination of opioid growth factor (OGF) and paclitaxel on squamous cell carcinoma of the head and neck (SCCHN) using a tissue culture model of human SCCHN. The combination of OGF and paclitaxel was markedly inhibitory to SCCHN proliferation, reducing growth from control levels by 48 to 69% within 48 h. OGF in combination with carboplatin also depressed cell growth.