The processing of human pro-tumor necrosis factor

Human pro-TNF-$\alpha$ is a 26 kd type II transmembrane protein, and it is the precursor of 17 kd mature TNF. Pro-TNF release mature from its extracellular domain by proteolytic cleavage between resideu Ava ($-$1) and Val (+1). Both forms of TNF are biologically active and the native form of mature TNF is a bell-shaped trimer. The structure of pro-TNF was studied both in intact cell system and in an in vitro translation system by chemical crosslinking. We found that human pro-TNF protein exist as a trimer in intact cells (LPS-induced THP-1 cells and TNF cDNA transfected COS-3 cells) and this trimeric structure is assembled intracellularly, possibly in the ER. By analysis several deletion mutants, we observed a correlation between expression of pro-TNF cytotoxicity in a juxtacrine fashion and detection of the trimer, suggesting the trimeric structure is very important for its biologic activity. With a series of deletion mutants in the linking domain, we found that the small deletion did not block the cleavage and large deletion did regardless of the presence or absence of the native cleavage site, suggesting that the length of the residues between the plasma membrane and the base of the trimer determines the rate of the cleavage, possibly by blocking the accessibility of the cleavage enzyme to its action site. Our data also suggest that the native cleavage site is not sufficient for the release of mature TNF and alternative cleavage site(s) exists. ^

Deviation of the alloimmune response toward tolerance by chimeric class I MHC molecules

Class I major histocompatibility complex (MHC) molecules induce either accelerated rejection or prolonged survival of allografts, presumably because of the presence of immunogenic or tolerogenic epitopes, respectively. To explore the molecular basis of this phenomenon, three chimeric class I molecules were constructed by substituting the rat class I RT1.A$\sp{\rm a}$ sequences with the N-terminus of HLA-A2.1 (N$\sp{\rm HLA-A2.1}$-RT1.A$\sp{\rm a}$), the $\alpha\sb1$ helix (h) with $\rm\alpha\sb{1h}\sp{u}$ sequences ( ($\rm\alpha\sb{1h}\sp{u}$) -RT1.A$\sp{\rm a}$) or the entire $\alpha\sb2$ domain (d) with $\rm\alpha\sb{2d}\sp{u}$ sequences ( ($\rm\alpha\sb{2d}\sp{u}$) -RT1.A$\sp{\rm a}$). Wild type (WT) and chimeric cDNAs were sequenced prior to transfection into Buffalo (BUF; RT1$\sp{\rm b}$) hepatoma cells. Stable transfectants were injected subcutaneously (s.c.) into different hosts 7 days prior to challenge with a heart allograft. In BUF hosts, chimeric ($\rm\alpha\sb{1h}\sp{u}$) -RT1.A$\sp{\rm a}$ accelerated the rejection of Wistar Furth (WF; RT1$\sp{\rm u}$) heart allografts, but had no effect on the survival of ACI (RT1$\sp{\rm a}$) grafts. In contrast, the ($\rm\alpha\sb{2d}\sp{u}$) -RT1.A$\sp{\rm a}$ (containing $\rm\alpha\sb{1d}\sp{a}$ sequences) immunized BUF recipients toward RT1$\sp{\rm a}$ grafts. In WF hosts, WT-RT1.A$\sp{\rm a}$ was a potent immunogen and accelerated ACI graft rejection, N$\sp{\rm HLA-A2.1}$-RT1.A$\sp{\rm a}$ was less effective and ($\rm\alpha\sb{\rm 1h}\sp{u}\rbrack$-RT1.A$\sp{\rm a}$ was not immunogenic. Thus, dominant and subdominant epitopes inducing in vivo sensitization to cardiac allografts are present in the $\alpha\sb1$ helix and the N-terminus, respectively. The failure of ($\rm\alpha\sb{2d}\sp{u}$) -RT1.A$\sp{\rm a}$ transfectants (containing recipient-type $\alpha\sb{\rm 2d}$ sequences) to sensitize WF hosts toward ACI (RT1$\sp{\rm a}$) grafts, despite the presence of donor-type immunogenic $\alpha\sb{\rm 1d}\sp{\rm a}$, suggests that "self-$\alpha\sb2$" sequences displayed on chimeric antigens interfere with immunogenicity. The ($\rm\alpha\sb{1h}\sp{u}$) -RT1.A$\sp{\rm a}$ transfectants injected s.c. prolonged the survival of WF (RT1$\sp{\rm u}$) hearts in ACI (RT1$\sp{\rm a}$) recipients. Furthermore, intra-portal injection of extracts from ($\rm\alpha\sb{1h}\sp{u}$) -RT1.A$\sp{\rm a}$, but not WT-RT1.A$\sp{\rm a}$ or RT1.A$\sp{\rm u}$, in conjunction with a brief cyclosporine course rendered ACI hosts permanently and specifically tolerant to donor-type WF cardiac allografts. Thus, immunodominant allodeterminants are present in the $\alpha\sb1$, but not the $\alpha\sb2$, domain of rat class I MHC molecules. Furthermore, the $\rm\alpha\sb{1h}\sp{u}$ immunogenic epitopes trigger tolerogenic responses when flanked by host-type N-terminal$\sp{\rm a}$ and $\rm\alpha\sb{2d}\sp{a}$ sequences. ^

Interactions between cyclosporin A, low-density lipoprotein and the low-density lipoprotein receptor

Cyclosporine A (CSA) is a cyclic eleven amino acid, lipophilic molecule used therapeutically as an immunosuppressive agent. Cyclosporine can specifically inhibit the transcription of a number of different genes. It is known that CSA is bound almost exclusively to lipoproteins in plasma, however, the relationship between the low density lipoprotein (LDL), the LDL receptor, and CSA has not been fully elucidated. The exact mechanism of cellular uptake of CSA is unknown, but it is believed to be by simple passive diffusion across the cell membrane. In addition, it has been recently shown that the frequent finding of hypercholesterolemia seen in patients treated with CSA can be explained by a CSA-induced effect. The mechanism by which CSA induces hypercholesterolemia is not known. We have used an LDL receptor-deficient animal model, the Watanabe Heritable Hyperlipidemic (WHHL) rabbit to investigate the role of LDL and the LDL receptor in the cellular uptake of CSA. Using this animal model, we have shown that CSA uptake by lymphocytes is predominantly LDL receptor-mediated. Chemical modification of apoB-100 on LDL particles abolishes their ability to bind to the LDL receptor. When CSA is incubated with modified LDL much less is taken-up than when native LDL is incubated with CSA. Treatment of two human cell lines with CSA results in a dose-dependent decrease in LDL receptor mRNA levels. Using a novel transfection system involving the 5$\sp\prime$-flanking region of the LDL receptor gene, we have found that CSA decreases the number of transcripts, but is dependent on whether or not cholesterol is present and the stage of growth of the cells. ^

Molecular evolution of primate immunodeficiency viruses and hepatitis delta virus

Primate immunodeficiency viruses, or lentiviruses (HIV-1, HIV-2, and SIV), and hepatitis delta virus (HDV) are RNA viruses characterized by rapid evolution. Infection by primate immunodeficiency viruses usually results in the development of acquired immunodeficiency syndrome (AIDS) in humans and AIDS-like illnesses in Asian macaques. Similarly, hepatitis delta virus infection causes hepatitis and liver cancer in humans. These viruses are heterogeneous within an infected patient and among individuals. Substitution rates in the virus genomes are high and vary in different lineages and among sites. Methods of phylogenetic analysis were applied to study the evolution of primate lentiviruses and the hepatitis delta virus. The following results have been obtained: (1) The substitution rate varies among sites of primate lentivirus genes according to the two parameter gamma distribution, with the shape parameter $\alpha$ being close to 1. (2) Primate immunodeficiency viruses fall into species-specific lineages. Therefore, viral transmissions across primate species are not as frequent as suggested by previous authors. (3) Primate lentiviruses have acquired or lost their pathogenicity several times in the course of evolution. (4) Evidence was provided for multiple infections of a North American patient by distinct HIV-1 strains of the B subtype. (5) Computer simulations indicate that the probability of committing an error in testing HIV transmission depends on the number of virus sequences and their length, the divergence times among sequences, and the model of nucleotide substitution. (6) For future investigations of HIV-1 transmissions, using longer virus sequences and avoiding the use of distant outgroups is recommended. (7) Hepatitis delta virus strains are usually related according to the geographic region of isolation. (8) Evolution of HDV is characterized by the rate of synonymous substitution being lower than the nonsynonymous substitution rate and the rate of evolution of the noncoding region. (9) There is a strong preference for G and C nucleotides at the third codon positions of the HDV coding region. ^

Gene transfer by viral vectors

To initiate our clinical trial for chemotherapy protection, I established the retroviral vector system for human MDR1 cDNA gene transfer. The human MDR1 cDNA continued to be expressed in the transduced bone marrow cells after four cohorts of serial transplants, 17 months after the initial transduction and transplant. In addition, we used this retroviral vector pVMDR1 to transduce human bone marrow and peripheral blood CD34$\sp+$ cells on stromal monolayer in the presence of hematopoietic growth factors. These data suggest that the retroviral vector pVMDR1 could modify hematopoietic precursor cells with a capacity for long-term self renewal. Thus, it may be possible to use the MDR1 retroviruses to confer chemotherapeutic protection on human normal hematopoietic precursor cells of ovarian and breast cancer patients in whom high doses of MDR drugs may be required to control the diseases.^ Another promising vector system is recombinant adeno-associated virus (rAAV) vector. An impediment to use rAAV vectors is that production of rAAV vectors for clinical use is extremely cumbersome and labor intensive. First I set up the rAAV vector system in our laboratory and then, I focused on studies related to the production of rAAV vectors for clinical use. By using a self-inactivating retroviral vector carrying a selection marker under the control of the CMV immediate early promoter and an AAV genome with the deletion of both ITRs, I have developed either a transient or a stable method to produce rAAV vectors. These methods involve infection only and can generate high-titer rAAV vectors (up to 2 x 10$\sp5$ cfu/ml of CVL) with much less work.^ Although recombinant adenoviral vectors hardly infect early hematopoietic precursor cells lacking $\alpha\sb v\beta\sb5$ or $\alpha\sb v\beta\sb3$ integrin on their surface, but efficiently infect other cells, we can use these properties of adenoviral vectors for bone marrow purging as well as for development of new viral vectors such as pseudotyped retroviral vectors and rAAV vectors. Replacement of self-inactivating retroviral vectors by recombinant adenoviral vectors will facilitate the above strategies for production of new viral vectors. In order to accomplish these goals, I developed a new method which is much more efficient than the current methods to construct adenoviral vectors. This method involves a cosmid vector system which is utilized to construct the full-length recombinant adenoviral vectors in vitro.^ First, I developed an efficient and flexible method for in vitro construction of the full-length recombinant adenoviral vectors in the cosmid vector system by use of a three-DNA fragment ligation. Then, this system was improved by use of a two-DNA fragment ligation. The cloning capacity of recombinant adenoviral vectors constructed by this method to develop recombinant adenoviral vectors depends on the efficiency of transfection only. No homologous recombination is required for development of infectious adenoviral vectors. Thus, the efficiency of generating the recombinant adenoviral vectors by the cosmid method reported here was much higher than that by the in vitro direct ligation method or the in vivo homologous recombination method reported before. This method of the in vitro construction of recombinant adenoviral vectors in the cosmid vector system may facilitate the development of adenoviral vector for human gene therapy. (Abstract shortened by UMI.) ^

{\it RAS\/} is required for the expression of interleukin-1$\beta$ in two diverse leukemic cell lines

Under normal physiological conditions, cells of the hematopoietic system produce Interleukin-1$\beta$(IL-1$\beta)$ only when a stimulus is present. Leukemic cells, however, can constitutively produce this cytokine without an exogenous source of activation. In addition, IL-1$\beta$ can operate as an autocrine and/or paracrine growth factor for leukemic blasts. In order to study the cellular basis for this aberrant production, we analyzed two leukemic cell lines (B1 and W1) which express high levels of IL-1$\beta$ and use IL-1$\beta$ as an autocrine growth factor. Initial studies demonstrated: (1) lack of rearrangement and/or amplification in the IL-1$\beta$ gene and its promoter; and (2) intact responsiveness to regulators such as cycloheximide and dexamethasone, implying that the molecular defect was upstream. Analysis of the Ras inducible transcription factors by gel shift assay demonstrated constitutive transcription factor binding in the IL-1$\beta$ promoter. Furthermore, RAS mutations were found at codon 12 in the K-RAS and N-RAS genes in the B1 and W1 cells, respectively. To deduce the effects of activated Ras on IL-1$\beta$ expression, two classes of farnesyltransferase inhibitors and an adenoviral vector expressing antisense targeted to K-RAS were utilized. The farnesyltransferase inhibitors perillyl alcohol and B581 were able to reduce IL-1$\beta$ levels by 80% and 50% in the B1 cells, respectively. In W1 cells, IL-1$\beta$ was reduced by 60% with 1mM perillyl alcohol. Antisense RNA targeted to K-RAS confirmed the results demonstrating a 50% reduction in IL-1$\beta$ expression in the B1 cells. In addition, decreased binding at the crucial NF-IL6/CREB binding site correlated with decreased IL-1$\beta$ production and cellular proliferation implying that this site was a downstream effector of Ras signaling. Our data suggest that mutated RAS genes may be responsible for autocrine IL-1$\beta$ production in some leukemias by stimulating signal transduction pathways that activate the IL-1$\beta$ promoter. ^

Regulation and function of {\it Xparaxis\/} during the development of paraxial mesoderm in {\it Xenopus laevis\/}

Genes of the basic helix-loop-helix transcription factor family have been implicated in many different developmental processes from neurogenesis to myogenesis. The recently cloned bHLH transcription factor, paraxis, has been found to be expressed in the paraxial mesoderm of the mouse suggesting a role for paraxis in the development of this mesodermal subtype which gives rise to the axial muscle, skeleton, and dermis of the embryo. In order to perform in vivo gain of function assays and obtain a better understanding of the possible roles of paraxis in mesodermal and somitic development, we have successfully identified homologues of paraxis in the frog, Xenopus laevis, where the process of mesodermal induction and development is best understood. The two homologues, Xparaxis-a and Xparaxis-b, are conserved with respect to their murine homologue in structure and expression within the embryo. Xparaxis genes are expressed immediately after gastrulation in the paraxial mesoderm of Xenopus embryos and are down regulated in the myotome of the mature somite with continued expression in the undifferentiated dermatome. Overexpression of Xparaxis-b in Xenopus embryos caused defects in the organization and morphology of the somites. This effect was not dependent on DNA binding of Xparaxis but is likely due to its dimerization with other bHLH factors. Co-injections with XE12 did not diminish the effects indicating that the defects were not the result of limiting amounts of XE12. We also demonstrated that Xparaxis does not cause obvious defects in the cell adhesions and movements required for proper mesoderm patterning during gastrulation. The paraxis proteins also lacked the ability to activate transcription as GAL4 fusion proteins in a GAL4 reporter assay, indicating that the genes may function more as modulators of the activity of dimerization partners than as positively acting cell determination factors. In agreement with this, Xparaxis is regulated in response to other pathways of bHLH gene action, in that XE12 can activate Xparaxis-b, in vivo. In addition we show regulation of Xparaxis in response to mMyoD induced myogenesis pathways, again suggesting Xparaxis plays an important role in the patterning and organization of the paraxial mesoderm. ^

Human TNF receptor p75/80 gene structure and promoter characterization

Tumor necrosis factor receptor p75/80 ((TNF-R p75/80) is a 75 kDa type 1 transmembrane protein expressed predominately on cells of hematopoietic lineage. TNF-R p75/80 belongs to the TNF receptor superfamily characterized by cysteine-rich extracellular regions composed of three to six disulfide-linked domains. In the present report, we have characterized, for the first time, the complete gene structure for human TNF-R p75/80 which spans approximately 43 kbp. The gene consists of 10 exons (ranging from 34 bp to 2.5 kbp) and 9 introns (343 bp to 19 kbp). Consensus elements for transcription factors involved in T cell development and activation were noted in the 5$\sp\prime$ flanking region including TCF-1, Ikaros, AP-1, CK-2, IL-6RE, ISRE, GAS, NF-$\kappa$B and SP1, as well as an unusually high GC content and CpG frequency that appears characteristic of some TNF-R family members. The unusual (GATA)$\sb{\rm n}$ and (GAA)(GGA) repeats found within intron 1 may prove useful for further genome analysis within the 1p36 chromosomal locus. The human TNF-R p75/80 gene structure will permit further assessment of its involvement in normal hematopoietic cell development and function, autoimmune disease, and non-random translocations in hematopoietic malignancies. The region 1.8 kb 5$\sp\prime$ of the ATG was able to drive luciferase expression when transfected into cell lines expressing TNF-R p75/80. Further characterization of the 5$\sp\prime$-regulatory region will aid in determining factors and signal transduction pathways involved in regulating TNF-R p75/80 expression. ^

Expression and regulation of interleukins in human head and neck squamous cell carcinoma

Patients with head and neck squamous cell carcinoma (HNSCC) demonstrate abnormal cell-mediated immunity which is most pronounced at the primary tumor site. Therefore, we tested whether this aberrant immunity could be due to tumor-derived cytokines. We investigated the presence of cytokine mRNA and protein in 8 HNSCC-derived cell lines; RT-PCR results indicated mRNA's for IL-1$\alpha$ and TGF-$\alpha$ (8/8), TGF-$\beta$ (7/8), IL-1$\beta$ (7/8), IL-4 and IL-6 (4/8). IL-2, IFN-$\gamma,$ and TNF-$\alpha$ mRNA was not detected. Supernatants from 6 of these cell lines were analyzed by ELISA and IL-1$\alpha,$ IL-1$\beta,$ and IL-6 were markedly increased compared to HPV-16 immortalized human oral keratinocytes. IL-1$\alpha$ was found in the highest concentration $>$IL-6 $>$ IL-1$\beta.$^ To approach the mechanisms of cytokine regulation, 4 cell lines were compared for HPV DNA presence, p53 status, and cytokine expression. An association between HPV DNA and cytokine expression was not found. However, cell lines secreting the most IL-6 had mutant p53 and/or HPV 16 E6/E7 expression. Further regulatory investigations revealed that exogenous IL-1$\alpha$ and/or IL-1$\beta$ minimally stimulated the proliferation of 2/3 cell lines, as well as strongly induced IL-6 production in 3/3; this effect was completely abrogated by IL-1Ra. IL-1Ra also inhibited the secretion of IL-1$\alpha$ and IL-1$\beta$ in 2/3 cell lines. These data suggest an IL-1 autocrine loop in certain HNSCC cell lines. Because IL-2 induces IL-1 and is used in therapy of HNSCC, the expression of IL-2 receptor was also investigated; IL-2 $\alpha$ and $\beta$ subunits were detected in 3/3 cell lines and $\gamma$ subunits was detected in one. Exogenous IL-2 inhibited the proliferation, but stimulated the secretion of IL-1$\alpha$ in 2/3, and IL-1$\beta$ and IL-6 in 1/3 cell lines.^ To determine if our cell line findings were applicable to patients, immunohistochemistry was performed on biopsies from 12 invasive tumors. Unexpectedly, universal intracellular production of IL-1$\alpha,$ IL-1$\beta,$ and IL-6 protein was detected. Therefore, the aberrant elaboration of biologically active IL-1 and IL-6 may contribute to altered immune status in HNSCC patients. ^

Targeting of {\it HER\/}-{\it 2\/}/{\it neu\/} with E1A gene therapy

Amplification or overexpression of HER-2/neu has been demonstrated in human cancers of the ovary, breast, lung and correlated with chemoresistance and poor clinic prognosis. We have previously found that the adenovirus type 5 early region 1A (E1A) gene product can repress the overexpression and suppress the tumorigenic potential of HER-2/neu-overexpressing cancer cells. In addition, E1A has been reported to induce apoptosis and inhibit the metastatic potential of tumor cells. Therefore, E1A could be considered as a tumor suppressor gene in HER-2/neu-overexpressing cancer cells. To develop an efficient HER-2/neu-targeting gene therapy with E1A, adenoviral vector or cationic liposome was used to introduce E1A into human ovarian, breast and lung cancer cells. Successful therapeutic effects were achieved.^ A replication-deficient adenovirus containing the E1A gene, Ad.E1A(+), was used to infect HER-2/neu-overexpressing human ovarian cancer cell line. Ovarian cancer growth in vitro and colony formation in soft agarose were greatly inhibited.^ To examine tumor suppressor function of E1A in breast cancer, we introduced E1A in vitro by adenovirus into both HER-2/neu-overexpressing and low-expressing human breast cancer cell lines. In HER-2/neu-overexpressing cells, E1A greatly inhibited tumor cell growth in vitro and colony formation in soft agarose. However, in low HER-2/neu expressing cancer cell lines, E1A could only reduce colony formation in soft agarose but had no significant effect on cell growth in monolayer, indicating different effects of E1A in these two types of cancer cells. To test the local therapeutic efficacy of E1A, we used either adenovirus- or liposome-mediated E1A gene delivery systems in an orthotopic breast cancer animal model.^ To test the therapeutic efficacy of systemically-delivered E1A in vivo lung cancer, we treated mice bearing intratracheal lung cancer by i.v. tail injections of Ad.E1A(+). As a result, Ad.E1A(+) suppressed HER-2/neu overexpression and inhibited intratracheal lung cancer growth. However, no significant tumor suppression effect of Ad.E1A(+) was observed in mice bearing HER-2/neu low expressing cell line when the same therapeutic procedure was followed. (Abstract shortened by UMI.) ^

drp, A novel cell density regulated protein

Growing cells are continuously processing signals of all varieties and responding to these signals by changes in cellular gene expression. One signal that cells in close proximity relay to each other is cell-cell contact. Non-transformed cells respond to cell-cell contact by arrest of growth and entry into G$\sb0,$ a process known as contact inhibition. Transformed cells do not respond to contact inhibition and continue to grow to high cell density, forming foci when in cell culture and tumors in the living organism. The events surrounding the generation, transduction, and response to cellular contact are poorly understood. In the present study, a novel gene product, drp, is shown to be expressed at high levels in cultured cells at high cell density. This density regulated protein, drp, has an apparent molecular weight of 70 kDa. Northern analysis shows drp to be highly expressed in cardiac and skeletal muscle and least abundant in lung and kidney tissues. By homology to two independently derived sequence tagged sites (STSs) used in the human genome project, drp or a closely related sequence maps to human chromosome 12. Density-dependent increases in drp expression have been demonstrated in six different cell lines including NIH 3T3, Hela and a human teratocarcinoma cell line, PA-1. Cells exhibit increased drp expression both when they are plated at increasing concentrations per unit area, or plated at low density and allowed to grow naturally to higher cell density. Cells at high density can exhibit several phenotypes including growth arrest, accumulation of soluble factors in the media, and increased numbers of cell contacts. Growth arrest by serum starvation or TGF-$\beta$ treatment fails to produce an increase in drp expression. Similarly, treatment of low density cells with conditioned media from high density cells fails to elicit drp expression. These results argue that neither soluble factors accumulated or expressed at high density nor simple exit from the cell cycle is sufficient to produce an increase in drp expression. The expression of drp appears to be uniquely regulated by cell density alone. ^

Mechanisms of liposomal all-{\it trans\/} retinoic acid and vitamin D3 induced inhibition of cell proliferation and stimulation of apoptosis in aggressive B-cell non-Hodgkin's lymphoma

The Non-Hodgkin's Lymphoma (NHLs) are neoplasms of the immune system. Currently, less than 1% of the etiology of the 22,000 newly diagnosed lymphoma cases in the U.S.A. every year is known. This disease has a significant prevalence and high mortality rate. Cell growth in lymphomas has been shown to be an important parameter in aggressive NHL when establishing prognosis, as well as an integral part in the pathophysiology of the disease process. While many aggressive B cell NHLs respond initially to chemotherapeutic regimens such as CHOP-bleo (adriamycin, vincristine and bleomycin) etc., relapse is common, and the patient is then often refractory to further salvage treatment regimens.^ To assess their potential to inhibit aggressive B cell NHLs and induce apoptosis (also referred to as programmed cell death (PCD)), it was proposed to utilize the following biological agents-liposomal all-trans retinoic acid (L-ATRA) which is a derivative of Vitamin A in liposomes and Vitamin D3. Preliminary evidence indicates that L-ATRA may inhibit cell growth in these cells and may induce PCD as well. Detailed studies were performed to understand the above phenomena by L-ATRA and Vitamin D3 in recently established NHL-B cell lines and primary cell cultures. The gene regulation involved in the case of L-ATRA was also delineated. ^

Study of retinoic acid signaling in cancer cells: Cloning and characterization of retinoic acid responsive genes

Retinoids such as all-trans-retinoic acid (ATRA) are promising agents for cancer chemoprevention and therapy. ATRA can cause growth inhibition, induction of differentiation and apoptosis of a variety of cancer cells. These effects are thought to be mediated by nuclear retinoids receptors which are involved in ligand-dependent transcriptional activation of downstream target genes. Using differential display, we identified several retinoic acid responsive genes in the head and neck squamous carcinoma cells and lung cancer cells, including tissue type transglutaminase, cytochrome P450-related retinoic acid hydroxylase, and a novel gene, designated RAIG1. RAIG1 has two transcripts of 2.4 and 6.8 kbp, respectively, that are generated by alternative selection of polyadenylation sites. Both transcripts have the same open reading frame that encodes a protein comprised of 357 amino acid residues. The deduced RAIG1 protein sequence contains seven transmembrane domains, a signature structure of G protein-coupled receptors. RAIG1 mRNA is expressed at high level in fetal and adult lung tissues. Induction of RAIG1 expression by ATRA is rapid and dose-dependent. A fusion protein of RAIG1 and the green fluorescent protein was localized in the cell surface membrane and perinuclear vesicles in transiently transfected cells. The locus for RAIG1 gene was mapped to a region between D12S358 and D12S847 on chromosome 12p12.3-p13. Our study of the novel retinoic acid induced gene RAIG1 provide evidence for a possible interaction between retinoid and G protein signaling pathways.^ We further examined RAIG1 expression pattern in a panel of 84 cancer cell lines of different origin. The expression level varies greatly from very high to non-detectable. We selected a panel of different cancer cells to study the effects of retinoids and other differentiation agents. We observed: (1) In most cases, retinoids (including all-trans retinoic acid, 4HPR, CD437) could induce the expression of RAIG-1 in cells from cancers of the breast, colon, head and neck, lung, ovarian and prostate. (2) Compare to retinoids, butyrate is often a more potent inducer of RAIG-1 expression in many cancer cells. (3) Butyrate, Phenylacetate butyrate, (R)P-Butyrate and (S)P-Butyrate have different impact on RAIG1 expression which varies among different cell lines. Our results indicate that retinoids could restore RAIG1 expression that is down-regulated in many cancer cells.^ A mouse homologous gene, mRAIG1, was cloned by 5$\sp\prime$ RACE reaction. mRAIG1 cDNA has 2105 bp and shares 63% identity with RAIG1 cDNA. mRAIG1 encodes a polypeptide of 356 amino acid which is 76% identity with RAIG1 protein. mRAIG1 protein also has seven transmembrane domains which are structurally identical to those of RAIG1 protein. Only one 2.2 kbp mRAIG1 transcript could be detected. The mRAIG1 mRNA is also highly expressed in lung tissue. The expression of mRAIG1 gene could be induced by ATRA in several mouse embryonal carcinoma cells. The induction of mRAIG1 expression is associated with retinoic acid-induced neuroectoderm differentiation of P19 cells. Similarity in cDNA and protein sequence, secondary structure, tissue distribution and inducible expression by retinoic acid strongly suggest that the mouse gene is the homologue of the human RAIG1 gene. ^

Development of prostate cancer gene therapy

Osseous metastases account for most of the morbidity and mortality associated with prostate cancer, for which there are currently no effective therapies. In the skeletal metastatic environment, neoplastic prostatic epithelial cells interact in a bidirectional stimulatory manner with osteoblastic stromal cells. Similarly, the presence of osteoblastic cells is essential for the survival and maintenance of intraosseous prostate cancer cells. In this thesis, I have developed novel gene therapy strategies for the treatment of androgen-independent human prostate cancers in experimental animal models. First, Ad-CMV-p53, a recombinant adenovirus (Ad) containing p53 tumor suppressor gene driven by the universal cytomegalovirus promoter, was effective in inhibiting prostate cancer cell growth, and direct intratumoral injections of Ad-CMV-p53 resulted in tumor regression. Second, because prostate cancer cells as well as osteoblastic cells produce osteocalcin (OC), OC promoter mediated tissue/tumor specific toxic gene therapy is developed to interrupt stromal-epithelial communications by targeting both cell types. Ad-OC-TK, a recombinant Ad containing the herpes simplex virus thymidine kinase (TK) gene driven by the OC promoter, was generated to inhibit the growth of osteoblastic osteosarcoma with prodrug acyclovir (ACV). Ad-OC-TK/ACV also inhibited the growth of prostate cancer cells and suppressed the growth of subcutaneous and intraosseous prostate tumor. In order to combine treatment modalities to maximize tumor cell-kill with minimized host toxicities, Ad-OC-TK/ACV was applied in combination with low dose methotrexate to eradicate osteoblastic osteosarcoma. In targeting of micrometastatic disease, intravenous Ad-OC-TK/ACV treatment resulted in significant tumor nodule reduction and prolonged the survival of animals harboring osteosarcoma lung metastases without significant host toxicity. Ad-OC-TK is a rational choice for the treatment of prostate cancer skeletal metastasis because OC is uniformly detected in both primary and metastatic human prostate cancer specimens by immunohistochemistry. Ad-OC-TK/ACV inhibits the growth not only of prostate cancer cells but also of their supporting bone stromal cells. Targeting both prostate cancer epithelium and its supporting stroma may be most efficacious for the treatment of prostate cancer osseous metastases. ^

The effects of population density on the spread of disease

The objective of this study is to identify the relationship between population density and the initial stages of the spread of disease in a local population. This study proposes to concentrate on the question of how population density affects the distribution of the susceptible individuals in a local population and thus affects the spread of the disease, measles. Population density is measured by the average of the number of contacts with susceptible individuals by each individual in the population during a fixed-length time period. The term “contact with susceptible individuals” means sufficient contact between two people for the disease to pass from an infectious person to a susceptible person. The fixed-length time period is taken to be the average length of time an infected person is infectious without symptoms of the disease. For this study of measles, the time period will be seven days. ^ While much attention has been given to modeling the entire epidemic process of measles, attempts have not been made to study the characteristics of contact rates required to initiate an epidemic. This study explores the relationship between population density, given a specific herd immunity rate in the population, and initial rate of the spread of the disease by considering the underlying distribution of contacts with susceptibles by the individuals in the population. ^ This study does not seek to model an entire measles epidemic, but to model the above stated relationship for the local population within which the first infective person is introduced. This study describes the mathematical relationship between population density parameters and contact distribution parameters. ^ The results are displayed in graphs that show the effects of different population densities on the spread of disease. The results support the idea that the number of new infectives is strongly related to the distribution of susceptible contacts. The results also show large differences in the epidemic measures between populations with densities equal to four versus three. ^