Transcriptional switching model for the regulation of tumorigenesis and metastasis by the ha-ras oncogene - transcriptional changes in the ha-ras tumor-suppressor gene lysyl oxidase

A model system is described that allows an analysis of the molecular and biochemical changes associated with expression and suppression of the oncogenic and metastatic phenotype of cloned rat embryo fibroblast (CREF) cells. Ha-ras-transformed CREF cells are morphologically transformed, anchorage-independent and both tumorigenic and metastatic in athymic nude mice and syngeneic Fischer rats. Co-expression of the Ha-ras oncogene and Krev-1 tumor suppressor gene in CREF cells results in suppression of in vitro transformation. In contrast, Ha-ras/Krev-1 transformed CREF cells retain, with greatly extended latency periods, both tumorigenic and metastatic capabilities in athymic nude mice. The present study investigates changes in the Ha-ms suppressor gene, rrg (lysyl oxidase), during expression and suppression of the oncogenic phenotype in CREF cells. Nontumorigenic CREF cells and CREF cells transformed by the Ha-ras and Krev-1 gene that express a suppression in in vitro transformation contain elevated levels of lysyl oxidase mRNA and protein. In contrast, Ha-ms and Ha-ras/Krev-1 nude mouse tumor- and nude mouse lung metastasis-derived CREF cells contain reduced levels of lysyl oxidase mRNA and protein. Nuclear run-on assays indicate that suppression of lysyl oxidase expression in transformed subclones of CREF cells correlates with a reduction in transcription of the lysyl oxidase gene. Taken together, the current studies support a transcriptional switching model in which lysyl oxidase expression correlates directly with suppression of the Ka-ms-induced transformation phenotype and escape from oncogenic suppression correlates with a transcriptional silencing of the lysyl oxidase gene and decreased lysyl oxidase mRNA and protein.

Identification of potential CSF biomarkers in ALS

BACKGROUND

The clinical diagnosis of ALS is based entirely on clinical features. Identification of biomarkers for ALS would be important for diagnosis and might also provide clues to pathogenesis.

OBJECTIVE

To determine if there is a specific protein profile in the CSF that distinguishes patients with ALS from those with purely motor peripheral neuropathy (PN) and healthy control subjects.

METHODS

CSF obtained from patients with ALS, disease controls (patients with other neurologic disorders), and normal controls were analyzed using the surface-enhanced laser desorption/ionization time-of-flight mass spectrometry proteomics technique. Biomarker sensitivity and specificity was calculated with receiver operating characteristic curve methodology. ALS biomarkers were purified and sequence identified by mass spectrometry-directed peptide sequencing.

RESULTS

In initial proteomic discovery studies, three protein species (4.8-, 6.7-, and 13.4-kDa) that were significantly lower in concentration in the CSF from patients with ALS (n = 36) than in normal controls (n = 21) were identified. A combination of three protein species (the "three-protein" model) correctly identified patients with ALS with 95% accuracy, 91% sensitivity, and 97% specificity from the controls. Independent validation studies using separate cohorts of ALS (n = 13), healthy control (n = 25), and PN (n = 7) subjects confirmed the ability of the three CSF protein species to separate patients with ALS from other diseases. Protein sequence analysis identified the 13.4-kDa protein species as cystatin C and the 4.8-kDa protein species as a peptic fragment of the neurosecretory protein VGF.

CONCLUSION

Additional application of a "three-protein" biomarker model to current diagnostic criteria may provide an objective biomarker pattern to help identify patients with ALS.

Gene expression profiling of the tau mutant (P301L) transgenic mouse brain

To provide a global analysis of the influence of Tau neuropathology at molecular level, we used cDNA arrays representing 8832 genes to determine the mRNA expression profile in transgenic mice expressing the most common frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) Tau mutation (P301L) (Nat. Genet. (2000) 402). Genes whose expression is associated with development of neurofibrillary tangles and neuron loss in P301L mice with motor and behavioral deficits were identified. The data suggest that a major mechanism underlying P301LTau neurodegeneration primarily involved altered expression of genes contributing to inhibition of apoptosis and intracellular transport. We propose that the expression of mutated P301L may lead to select altered expression of genes which may cause neurodegeneration in FTDP-17.

Altered expression of a-type but not b-type synapsin isoform in the brain of patients at high risk for Alzheimer's disease assessed by DNA microarray technique

Using a cDNA microarray representing 6794 distinct human genes, we identified candidate genes whose expression is altered in cerebral cortex of cases of early Alzheimer's disease (AD); among these was the synaptic vesicle protein synapsin II, which plays an important role in neurotransmitter release. While other candidate genes are presently under investigation in our lab, in this study we discuss the regulation of synapsin gene expression during the transition from normal cognitive function to early AD. We found a selective decrease in the expression of the synapsin splice variants I-III of the a-type isoform in the entorhinal (EC, BM36) but not visual cortex (VC, BM17) of cases characterized by the earliest clinically detectable stage of AD. In contrast, we found no changes in synapsin splice variant II of the b-type isoform. Alteration of synapsin expression at the earliest clinical stage of AD may suggest novel strategies for improved treatment.

Cytokine gene expression as a function of the clinical progression of Alzheimer disease dementia

BACKGROUND

Inflammatory cytokines have been linked to Alzheimer disease (AD) neurodegeneration, but little is known about the temporal control of their expression in relationship to clinical measurements of AD dementia progression.

DESIGN AND MAIN OUTCOME MEASURES

We measured inflammatory cytokine messenger RNA (mRNA) expression in postmortem brain specimens of elderly subjects at different clinical stages of dementia and neuropathological dysfunction.

SETTING AND PATIENTS

Postmortem study of nursing home patients.

RESULTS

In brains of cognitively normal control subjects, higher interleukin 6 (IL-6) and transforming growth factor beta1 (TGF-beta1) mRNA expression was observed in the entorhinal cortex and superior temporal gyrus compared with the occipital cortex. Compared with age-matched controls, subjects with severe/terminal dementia, but not subjects at earlier disease stages, had higher IL-6 and TGF-beta1 mRNA expression in the entorhinal cortex (P<.01) and superior temporal gyrus (P<.01). When stratified by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropathological criteria, IL-6 mRNA expression in both the entorhinal cortex (P<.05) and superior temporal gyrus (P<.01) correlated with the level of neurofibrillary tangles but not neuritic plaques. However, in the entorhinal cortex, TGF-beta1 mRNA did not correlate with the level of either neurofibrillary tangles or neuritic plaques. Interestingly, in the superior temporal gyrus, TGF-beta1 mRNA expression negatively correlated with neurofibrillary tangles (P<.01) and showed no relationship to the pathological features of neuritic plaques.

CONCLUSIONS

The data are consistent with the hypothesis that cytokine expression may differentially contribute to the vulnerability of independent cortical regions during the clinical progression of AD and suggest that an inflammatory cytokine response to the pathological effects of AD does not occur until the late stages of the disease. These findings have implications for the design of anti-inflammatory treatment strategies. Arch Neurol. 2000;57:1153-1160

Detection of circulating thyroid cells in peripheral blood

BACKGROUND

Detection of circulating malignant thyroid cells may provide a method to identify postoperative patients at risk for metastatic thyroid cancer.

METHODS

On the basis of tissue specificity of thyroglobulin gene expression and the sensitivity of the reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, we performed RT-PCR using primers for thyroglobulin on blood samples from patients with thyroid disease to detect thyroglobulin RNA transcripts. Postoperative peripheral blood samples from 100 patients, including patients with known metastatic thyroid cancer (six papillary and three follicular), thyroid cancer and no evidence of current metastases (63 papillary, 10 follicular, and five patients with both papillary and follicular), benign thyroid disease (six nontoxic nodular goiters), and normal volunteers (seven).

RESULTS

Thyroglobulin transcripts were detected in nine of nine patients with metastatic thyroid cancer, seven of 78 patients with thyroid cancer and no current metastases (although of these seven patients, five had a history of metastatic disease that had been previously treated by surgery, one had a coexisting parathyroid cancer, and one had both papillary and follicular thyroid cancers), zero of six patients with benign thyroid disease, and zero of seven normal volunteers. Identity of amplicons was confirmed by restriction enzyme digestion and by cloning and sequencing of RT-PCR amplified thyroglobulin fragment (the latter in a limited number of cases).

CONCLUSIONS

These data indicate that RT-PCR can be used to detect thyroglobulin mRNA in peripheral blood. The presence of these transcripts correlates with the existence of extrathyroidal disease.

c-fos is a positive regulator of carcinogen enhancement of adenovirus transformation

The early gene expression changes mediating carcinogen enhancement of viral transformation (CET) remain to be elucidated. A model cell culture system has been developed that is now permitting a molecular analysis of CET. Pretreatment of cloned rat embryo fibroblast (CREF) cells with methyl methanesulfonate (MMS) prior to infection with the cold-sensitive host-range type 5 adenovirus mutant, H5hr1, results in a dose-dependent increase in viral transformation. The present study investigates the role of immediate-early response genes, specifically c-fos, in the CET process. MMS pretreatment, alone or in combination with infection with H5hr1 temporally and differentially increases c-fos, c-jun, jun-B, jun-D and c-myc steady-state mRNA levels. Maximum induction occurs with c-fos and c-jun 8 to 12 h posttreatment and the magnitude of response is generally greatest in CREF cells pretreated with MMS and then infected with H5hr1. Enhancement in RNA levels is observed in the presence of cycloheximide indicating that ongoing protein synthesis is not required for induction of c-fos, c-jun, jun-B or c-myc expression. Nuclear run-on analysis indicates an enhancement in transcriptional rates for c-fos, c-jun, jun-B and c-myc in CREF cells treated with MMS or MMS plus infection with H5hr1. A requirement for elevated c-fos in the early stages of CET is indicated by the ability of c-fos antisense oligonucleotides to prevent the CET process. Direct evidence implicating early increases in c-fos as a mediator of the CET process is demonstrated by stably expressing mouse mammary tumor virus promoter-regulated human sense and antisense c-fos genes in CREF cells. Induction of c-fos sense expression by dexamethasone (DEX) in the absence of MMS treatment results in enhanced c-fos mRNA, Fos protein, AP-1 DNA-binding activity and H5hr1-induced transformation and CET. Induction of c-fos expression by DEX in stable c-fos-sense CREF constructs also results in elevated levels of c-jun, jun-B and c-myc mRNA and protein. Conversely, induction of c-fos antisense expression prevents the increase in c-fos mRNA, Fos protein and AP-1 DNA-binding activity and eliminates CET. In the antisense-c-fos constructs, increases in c-jun, jun-B and c-myc mRNA and protein normally induced by MMS also are not apparent. Thus, induction or inhibition in c-fos expression affects the level of expression of additional immediate-early response genes, including c-jun, jun-B and c-myc.(ABSTRACT TRUNCATED AT 400 WORDS)

Radioimmunoimaging of human breast carcinoma xenografts in nude mouse model with 111In-labeled new monoclonal antibody EBA-1 and F(ab')2 fragments

Radioimmunoimaging characteristics of a new monoclonal antibody EBA-1 and its F(ab')2 fragments utilizing nu/nu mice bearing human breast carcinoma xenografts are described. 111In-DTPA conjugates of EBA-1 localized with tumor/blood ratios of 0.99 +/- 0.10 (P < 0.3) and 4.65 +/- 1.60 (P < 0.05), and localization indices of 1.25 and 2.61 at 24 and 72 h, respectively. A tumor/blood ratio as high as 28.86 +/- 6.90 (P < 0.025) was obtained with EBA-1 F(ab')2 radioconjugates at 48 h. These results suggest that EBA-1 and its F(ab')2 might be useful reagents in radioimmunoimaging and radioimmunotherapy.

Tumor localization in nude mice bearing human breast carcinoma xenografts using 111In-DTPA conjugates of monoclonal antibodies

Biodistribution of monoclonal antibody T43 and its F(ab')2 111In-DTPA conjugates were determined in nu/nu mice bearing human breast tumor and rat pituitary tumor xenografts. T43 localized in the target tumor with tumor/blood ratios of 3.9 (P less than 0.01) and 4.5 (P less than 0.05) at 48 and 72 h, respectively. T43 F(ab')2 fragments localized with tumor/blood ratio of 14.2 (P less than 0.1) at 72 h. Tumors as small as 4 mm were detected without computer subtraction technique. These studies suggest that T43 and T43 F(ab')2 might be useful reagents in radioimaging.

Phototoxic liposomes coupled to an antibody that alone cannot modulate its cell-surface antigen kill selected target cells

Molecules such as antibodies that bind to cell surfaces can be used to deliver cytotoxic drugs to selected cells. To be effective the drug must usually be taken into the cells by endocytosis. In this study a T-cell line (CCRF-CEM) was effectively killed by liposomes carrying a photosensitizer and bearing the antibody OKT4 (anti-CD4). The unconjugated antibody does not induce antigenic modulation in the target cells, an indication of the absence of endocytosis, and would therefore not normally have been selected as an agent for drug delivery. It cannot, however, be concluded with certainty that the conjugates act at the cell surface and several alternative explanations of their efficacy are offered.

Selective killing of T lymphocytes by phototoxic liposomes

Two-fold specificity in drug delivery obtained through the localized activation of drugs by physical means and the attachment of drugs to proteins that bind to target cells might be used for highly selective cancer chemotherapy or for immunosuppression. Toward this end, a monoclonal antibody against an antigen on the surface of T lymphocytes was covalently attached to liposomes containing a phototoxic drug, pyrene, bound to the lipid bilayer. When unfractionated peripheral blood lymphocytes, or B- and T-cell lines, were irradiated after treatment with these liposomes, T cells were killed while B cells were spared, demonstrating the validity of the approach in a simple in vitro assay.