The RET/PTC3 oncogene activates classical NF-κB by stabilizing NIK.

The oncogenic fusion protein RET/PTC3 (RP3) that is expressed in papillary thyroid carcinoma (PTC) and thyroid epithelia in Hashimoto's thyroiditis activates nuclear factor-kappa B (NF-κB) and induces pro-inflammatory gene expression; however, the mechanism of this activation is unknown. To address this, we expressed RP3 in murine embryonic fibroblasts (MEFs) lacking key classical and noncanonical NF-κB signaling components. In wild-type MEFs, RP3 upregulated CCL2, CXCL1, granulocyte-macrophage colony-stimulating factor and tumor necrosis factor expression and activated classical but not noncanonical NF-κB. RP3-activated NF-κB in IκB kinase (IKK)ß(-/-) MEFs but not IKKα- or NF-κB essential modulator (NEMO)-deficient cells and activation was inhibited by a peptide that blocks NEMO binding to the IKKs. RP3 increased the levels of NF-κB-inducing kinase (NIK) and did not activate NF-κB in NIK-deficient MEFs. Notably, NIK stabilization was not accompanied by TRAF3 degradation demonstrating that RP3 disrupts normal basal NIK regulation. Dominant-negative NIK blocked RP3-induced NF-κB activation and an RP3 signaling mutant (RP3(Y588F)) did not stabilize NIK. Finally, examination of PTC specimens revealed strong positive staining for NIK. We therefore conclude that RP3 activates classical NF-κB via NIK, NEMO and IKKα. Importantly, our findings reveal a novel mechanism for oncogene-induced NF-κB activation via stabilization of NIK.

Cancer mucosa antigens as a novel immunotherapeutic class of tumor-associated antigen.

Colorectal cancer is a leading cause of cancer-related mortality worldwide. Surgery and chemoradiation exhibit incomplete efficacy and, ultimately, 50% of patients die of metastatic disease. In the context of that unmet clinical need, immunotherapeutic approaches have enjoyed limited success, partly because of a paucity of suitable antigen targets. However, exploitation of immune compartmentalization, employing antigens with expression restricted to normal intestinal mucosa and derivative colorectal tumors--cancer mucosa antigens (CMAs)--may represent a previously unrecognized class of immune targets supporting efficacious antitumor immunotherapy. Guanylyl cyclase C (GCC) is an intestine/colorectal cancer-restricted protein ideally suited as the first CMA for clinical evaluation.

Thyroid targeting of the N-ras(Gln61Lys) oncogene in transgenic mice results in follicular tumors that progress to poorly differentiated carcinomas.

Ras oncogenes are frequently mutated in thyroid carcinomas. To verify the role played by N-ras in thyroid carcinogenesis, we generated transgenic mice in which a human N-ras(Gln61Lys) oncogene (Tg-N-ras) was expressed in the thyroid follicular cells. Tg-N-ras mice developed thyroid follicular neoplasms; 11% developed follicular adenomas and approximately 40% developed invasive follicular carcinomas, in some cases with a mixed papillary/follicular morphology. About 25% of the Tg-N-ras carcinomas displayed large, poorly differentiated areas, featuring vascular invasion and forming lung, bone or liver distant metastases. N-ras(Gln61Lys) expression in cultured PC Cl 3 thyrocytes induced thyroid-stimulating hormone-independent proliferation and genomic instability with micronuclei formation and centrosome amplification. These findings support the notion that mutated ras oncogenes could be able to drive the formation of thyroid tumors that can progress to poorly differentiated, metastatic carcinomas.

Human papilloma virus 16 E7 oncogene does not cooperate with RET/PTC 3 oncogene in the neoplastic transformation of thyroid cells in transgenic mice.

We have previously reported that the thyroid-targeted expression of the RET/PTC3 oncogene (Tg-RET/PTC3) in transgenic mice induces follicular hyperplasia with papillary architecture, resulting in a modest increase of the thyroid gland volume, followed by the appearance of papillary carcinomas in approximately 1-year-old animals. In order to analyze the genetic alterations that may cooperate with RET/PTC3 in the development or progression of thyroid tumors, we interbred Tg-RET/PTC3 mice with Tg-E7 transgenic mice, which express the E7 oncogene of the human papilloma virus 16 in thyroid cells. Tg-E7 mice develop large colloid goiters with small papillae and well-differentiated thyroid carcinomas in older animals. Here we show that thyroid lesions in Tg-RET/PTC3-Tg-E7 double transgenics were morphologically different from those occurring in Tg-RET/PTC3 mice, while they were virtually indistinguishable from those occurring in Tg-E7 mice. In addition, the coexpression of RET/PTC3 and E7 oncogenes neither enhanced the malignant phenotype nor reduced the latency period of thyroid lesions with respect to parental transgenic lines. We conclude that the coexpression of RET/PTC3 and E7 lacks any cooperative effect in the neoplastic transformation of thyroid cells and that the E7-induced thyroid phenotype is dominant with respect to the RET/PTC3 one.

Expression of NeuroD and TrkB in developing and aged mouse olfactory epithelium.

To better understand the roles of NeuroD, a member of the basic helix-loop-helix transcription factor family, during the differentiation of olfactory receptor neurons, we studied the expression of NeuroD in developing and aging mouse olfactory epithelium (OE). During embryonic period, NeuroD expression is confined in the basal compartment of OE. During neonatal period, NeuroD expression is detected in the middle compartment and in the basal compartment of OE. In the adult, the number of NeuroD expressing cells in the basal compartment significantly decreased, while the NeuroD-positive cells in the middle compartment was maintained throughout lifetime. This dual phase expression pattern of NeuroD suggests multiple roles of NeuroD in the neurogenesis of ORNs.

Altered gene expression in immunogenic poorly differentiated thyroid carcinomas from RET/PTC3p53-/- mice.

Cancers develop and progress via activation of oncogenes and loss of tumor suppressor genes, a progression that can be recapitulated through cross breeding mouse strains harboring genetic mutations. To define the role of RET/PTC3, p53 and Fhit in thyroid carcinogenesis, we intercrossed RET/PTC3 transgenics with p53-/- mice. This new strain, RET/PTC3p53-/-, succumb to rapidly growing and strikingly large multilobed thyroid tumors containing mixtures of both well and poorly differentiated, highly proliferative follicular epithelial cells. Interestingly, transplanted tumors from RET/PTC3p53-/- mice grew in SCID but not syngeneic immunocompetent mice indicating that these advanced tumors were immunogenic. RET/PTC3 protein expression was reduced to undetectable levels in tumors of older mice suggesting that the continued elevated expression of RET/PTC3 may not be necessary for tumor progression. Similarly, expression of Fhit protein was reduced in early tumors and undetected in older tumors irrespective of tumor histopathology. In contrast to RET/PTC3p53-/- mice, RET/PTC3Fhit-/- mice did not develop advanced thyroid carcinomas. These studies support a model of human thyroid cancer whereby thyroid epithelium expresses RET/PTC3 protein at early stages of tumor development, followed by the reduction of RET/PTC3 and loss of p53 function with progressive reduction of Fhit protein expression coincident with malignant progression.

Pathologic features of Hashimoto's-associated papillary thyroid carcinomas.

Some investigators have found an increased incidence of papillary carcinoma (PC) of the thyroid in patients with Hashimoto's (autoimmune) thyroiditis (HT), which raises the possibility that there may be more than an incidental association between these 2 diseases. In this study, we analyzed the pathology of Hashimoto's-associated thyroid carcinomas to see if these tumors showed any distinctive features. The possible significance of solid cellular nodules as preneoplastic lesions in patients with HT was investigated. A review of all the cases of HT during a 16-year period yielded 30 PC and 3 follicular carcinomas (FC). Within the PC there were 7 (23%) follicular variants. Twenty (67%) of the PC showed various degree of intratumoral fibrosis, ranging from thick fibrous septa separating tumor nodules to almost complete obliteration of the tumor by the fibrosis, with only microscopic residual tumor nests. In most of the cases, the desmoplastic response within the tumors was of the fibromatosis-like type with dense hyalinized collagen and bland-appearing spindle cells. All the tumors, independently of the degree of fibrosis, showed the nuclear features of PC. No correlation was found between the degree of fibrosis in the tumors and the thyroid gland outside the tumors. There were tumors with marked fibrosis without fibrosis outside the tumors. Four cases of PC (13%) showed a growth pattern characterized by cystic spaces with thick hyalinized walls and focal papillary hyperplasia lined by flat and cuboidal epithelium, reminiscent of a vascular neoplasm. There were 4 atypical solid microscopic nodules with confluent cellularity; 2 of them associated with a PC and the other 2 with diffuse HT without PC. These nodules were composed of cells with clear nuclei and occasional grooves without nuclear pseudoinclusions. By immunohistochemistry, 2 of 3 nodules showed cytoplasmic reactivity for cytokeratin 19, and 2 of 3 nodules were positive for the RET/PTC (rearranged during transfection, papillary thyroid carcinoma) antibody. In summary, HT-associated PC may frequently display prominent stromal desmoplasia and a pseudovascular pattern, both of which can present diagnostic difficulties if the cytologic features of PC are not recognized because of the marked obliteration of the tumor by the fibrosis. Atypical nodules may represent a precursor lesion of PC in patients with HT.

bFGF induces differentiation and death of olfactory neuroblastoma cells.

Olfactory neuroblastoma (ONB) is a highly vascularized and malignant tumor arising in olfactory neuronal precursors from the paranasal sinuses. Previously, we showed that treatment of JFEN cells with transforming growth factor (TGF)-alpha caused them to differentiate and respond to chemical odorants, whereas basic fibroblast growth factor (bFGF) treated cells differentiated and died. In the present study we show that established ONB tumors treated with bFGF upregulate the bFGF receptor (FGFR1) prior to differentiation. This cellular differentiation was evidenced by bFGF-induced expression of the human runt homologue AML1 (PEBP2 alpha B, CBFA-2) that is highly expressed in developing olfactory neuroepithelium and TrkA, a preferred nerve growth factor receptor. Since TrkA is expressed in supporting cells, but not in mature olfactory neurons, we hypothesize that the expression of AML1 and TrkA in bFGF-treated JFEN cells induced supporting cell differentiation. Collectively, these results have implications for the treatment of patients afflicted with ONB.

The TRK-T1 fusion protein induces neoplastic transformation of thyroid epithelium.

Genetic analysis of human papillary thyroid carcinomas (PTC) has revealed unique chromosomal translocations that form oncogenic fusion proteins and promote thyroid tumorigenesis in up to 60% of tumors examined. Although, the majority of thyroid specific translocations involve the growth factor receptor c-RET, variant rearrangements of the receptor for nerve growth factor, NTRK1 have also been described. One such translocation, TRK-T1, forms a fusion protein composed of the carboxyl terminal tyrosine kinase domain of NTRK1 and the amino terminal portion of TPR (Translocated Promoter Region). To determine if TRK-T1 expression can cause thyroid cancer in vivo, we developed transgenic mice that express the human TRK-T1 fusion protein in the thyroid. Immunohistochemical analysis of TRK-T1 transgenic mouse thyroids revealed TRK-T1 staining within the thyroid follicular epithelium. In contrast to nontransgenic littermates, 54% of transgenic mice developed thyroid abnormalities that included follicular hyperplasia and papillary carcinoma. Furthermore, all transgenic mice examined greater than 7 months of age developed thyroid hyperplasia and/or carcinoma. These data support the conclusion that TRK-T1 is oncogenic in vivo and contributes to the neoplastic transformation of the thyroid.

Purification and characterization of recombinant forms of murine Tcl1 proteins.

The TCL1 gene, which is located on chromosome 14, plays a major role in human hematopoietic malignancies and encodes a 14-kDa protein whose function has not been determined. This gene is expressed in pre-B cells, in immature thymocytes, and, at low levels, in activated T cells but not in peripheral mature B cells and in normal cells. The Tcl1 protein is similar in its primary structure to a protein encoded by the mature T-cell proliferation gene (MTCP1). The MTCP1 gene is located on the X chromosome and has been shown to be involved in rare chromosomal translocations in T-cell proliferative diseases. The murine TCL1 gene resides on mouse chromosome 12 and is homologous to the human TCL1 and MTCP1 genes. Murine Tcl1 protein has 116 amino acid residues and shares 50% sequence identity with human Tcl1, while the human and mouse Mtcp1 are nearly identical, with conservative differences in only six residues. The TCL1 and MTCP1 genes appear to be members of a family of genes involved in lymphoid proliferation and T-cell malignancies. Our laboratory has undertaken the study of the Tcl1 and Mtcp1 proteins to determine the structure and the function of these related proteins. In the present report, we have produced, using a bacterial expression system, the purified murine Tcl1 protein and a mutant form of murine Tcl1 protein containing a cysteine to alanine mutation at amino acid position 85. The recombinant proteins were purified by chromatography on a Ni-NTA resin followed by reverse-phase FPLC using a buffer system at pH 7.9 and a polymer-based reverse-phase column. The murine Tcl1 recombinant protein displays limited solubility and forms disulfide-linked dimers and oligomers, while the mutant murine Tcl1 C86A protein has increased solubility and does not form higher order oligomers. The purified recombinant murine proteins were characterized by N-terminal sequence analysis, mass spectrometry, and circular dichroism spectroscopy. Initial results indicate that the mutant murine Tcl1 C86A protein is suitable for both NMR and X-ray crystallographic methods of structure determination.

Genomic analysis of human and mouse TCL1 loci reveals a complex of tightly clustered genes.

TCL1 and TCL1b genes on human chromosome 14q23.1 are activated in T cell leukemias by translocations and inversions at 14q32.1, juxtaposing them to regulatory elements of T cell receptor genes. In this report we present the cloning, mapping, and expression analysis of the human and murine TCL1/Tcl1 locus. In addition to TCL1 and TCL1b, the human locus contains two additional genes, TCL1-neighboring genes (TNG) 1 and 2, encoding proteins of 141 and 110 aa, respectively. Both genes show no homology to any known genes, but their expression profiles are very similar to those of TCL1 and TCL1b. TNG1 and TNG2 also are activated in T cell leukemias with rearrangements at 14q32.1. To aid in the development of a mouse model we also have characterized the murine Tcl1 locus and found five genes homologous to human TCL1b. Tcl1b1-Tcl1b5 proteins range from 117 to 123 aa and are 65-80% similar, but they show only a 30-40% similarity to human TCL1b. All five mouse Tcl1b and murine Tcl1 mRNAs are abundant in mouse oocytes and two-cell embryos but rare in various adult tissues and lymphoid cell lines. These data suggest a similar or complementary function of these proteins in early embryogenesis.

Human N-ras, TRK-T1, and RET/PTC3 oncogenes, driven by a thyroglobulin promoter, differently affect the expression of differentiation markers and the proliferation of thyroid epithelial cells.

The ras family members and the tyrosine kinases RET and TRK are frequently activated in human tumors of the thyroid gland. To ascertain the effects of these oncogenes in cultured thyroid cells we have generated expression vectors containing activated versions of the three genes under the control of the thyroid-specific thyroglobulin gene promoter. Here we show that the expression of the three oncogenes differently affects thyroid differentiation. While the TRK-T1 oncogene interferes with the capability of thyroid cells of trapping iodide and only marginally affects thyroglobulin gene expression, both RET/PTC3 and N-ras(Gln61-Lys) induce a dramatic reduction of thyroglobulin mRNA and alleviate TSH dependency for cellular growth. However, none of the three oncogenes is able to induce the appearance of neoplastic transformation markers, such as growth in semisolid medium and tumorigenicity in athymic mice. This indicates that genetic events additional to TRK, RET, or N-ras activation are required for fully malignant transformation of thyroid cells.

Olfactory neuron-specific expression of NeuroD in mouse and human nasal mucosa.

Human olfactory neuroepithelium (OE) is situated within the olfactory cleft of the nasal cavity and has the characteristic property of continually regenerating neurons during the lifetime of the individual. This regenerative ability of OE provides a unique model for neuronal differentiation, but little is known about the structure and biology of human olfactory mucosa. Thus, to better understand neurogenesis in human OE, we studied the expression of olfactory marker protein (OMP), TrkB and NeuroD in human nasal biopsies and autopsy specimens and compared these data with those obtained from normal and regenerating mouse OE. We show that NeuroD and TrkB are coordinately expressed in human OE. Thus, by using these markers we have been able to extend the known boundaries of the human OE to include the inferior middle turbinate. In normal mouse OE, TrkB and OMP expression overlap in cells closest to the superficial layer, but TrkB is expressed more strongly in the lower region of this layer. In contrast, NeuroD expression is more basally restricted in a region just above the globose basal cells. These characteristic expression patterns of OMP, TrkB and NeuroD were also observed in the regenerating mouse OE induced by axotomy. These results support a role of NeuroD and brain-derived neurotrophic actor (BDNF), the preferred ligand for TrkB, in the maintenance of the olfactory neuroepithelium in humans and mice.

The RET/PTC3 oncogene: metastatic solid-type papillary carcinomas in murine thyroids.

Our research goal is to better understand the mechanisms controlling the initiation and progression of thyroid diseases. One such disease, papillary thyroid carcinoma (PTC), is the leading endocrine malignancy in the United States. Recently, a family of related fusion proteins, RET/PTC1-5, has been implicated in the early stages of PTC. Although all five members of this family have the c-RET proto-oncogene kinase domain in their COOH terminus, little is known about how these genes alter follicular cell biology. Consequently, to answer questions related to the mechanism of the RET/PTC fusion protein action, we have devised a molecular genetic strategy to study PTC using a mouse model of thyroid disease. A new member of this fusion oncogene family, RET/PTC3, which has been implicated in more cases of solid tumor carcinoma (79%) than PTC1 or PTC2 and predominates (80%) in radiation-induced thyroid cancer of children, was investigated in our study. We have generated transgenic mice expressing human RET/PTC3 exclusively in the thyroid. These mice develop thyroid hyperplasia, solid tumor variants of papillary carcinoma and metastatic cancer. This new transgenic line will be useful in deciphering the molecular and biological mechanisms that cause PTC and histological variations in humans.

Crystal structure of MTCP-1: implications for role of TCL-1 and MTCP-1 in T cell malignancies.

Two related oncogenes, TCL-1 and MTCP-1, are overexpressed in T cell prolymphocytic leukemias as a result of chromosomal rearrangements that involve the translocation of one T cell receptor gene to either chromosome 14q32 or Xq28. The crystal structure of human recombinant MTCP-1 protein has been determined at 2.0 A resolution by using multiwavelength anomalous dispersion data from selenomethionine-enriched protein and refined to an R factor of 0.21. MTCP-1 folds into a compact eight-stranded beta barrel structure with a short helix between the fourth and fifth strands. The topology is unique. The structure of TCL-1 has been predicted by molecular modeling based on 40% amino acid sequence identity with MTCP-1. The identical residues are clustered inside the barrel and on the surface at one side of the barrel. The overall structure of MTCP-1 superficially resembles the structures of proteins in the lipocalin family and calycin superfamily. These proteins have diverse functions, including transport of retinol, fatty acids, chromophores, pheromones, synthesis of prostaglandin, immune modulation, and cell regulation. However, MTCP-1 differs in the topology of the beta strands. The structural similarity suggests that MTCP-1 and TCL-1 form a unique family of beta barrel proteins that is predicted to bind small hydrophobic ligands and function in cell regulation.

Deregulated expression of TCL1 causes T cell leukemia in mice.

The TCL1 oncogene on human chromosome 14q32.1 is involved in the development of T cell leukemia in humans. These leukemias are classified either as T prolymphocytic leukemias, which occur very late in life, or as T chronic lymphocytic leukemias, which often arise in patients with ataxia telangiectasia (AT) at a young age. The TCL1 oncogene is activated in these leukemias by juxtaposition to the alpha or beta locus of the T cell receptor, caused by chromosomal translocations t(14:14)(q11:q32), t(7:14)(q35:q32), or by inversions inv(14)(q11:q32). To show that transcriptional alteration of TCL1 is causally involved in the generation of T cell neoplasia we have generated transgenic mice that carry the TCL1 gene under the transcriptional control of the p56(lck) promoter element. The lck-TCL1 transgenic mice developed mature T cell leukemias after a long latency period. Younger mice presented preleukemic T cell expansions expressing TCL1, and leukemias developed only at an older age. The phenotype of the murine leukemias is CD4-CD8+, in contrast to human leukemias, which are predominantly CD4+CD8-. These studies demonstrate that transcriptional activation of the TCL1 protooncogene can cause malignant transformation of T lymphocytes, indicating the role of TCL1 in the initiation of malignant transformation in T prolymphocytic leukemias and T chronic lymphocytic leukemias.

The murine Tcl1 oncogene: embryonic and lymphoid cell expression.

In human leukemias and lymphomas nonrandom chromosomal rearrangements cause changes in cell growth and/or survival in such a way as to promote malignancy. The detailed study of the biochemical and genetic pathways altered in human cancer requires the identification or development of models to allow the study and manipulation of cancer gene function. Recently, the breakpoint gene TCL1, involved in chromosome translocations observed mostly in mature T-cell proliferations and chronic lymphocytic leukemias (CLL), was isolated and characterized, and showed to be part of a new gene family of proteins involved in these tumors. The murine Tcl1 gene, is similar in sequence to the murine and human MTCP1 gene also involved in T cell leukemias. The murine Tcl1 gene was shown to reside on mouse chromosome 12 in a region syntenic to human chromosome 14. Furthermore, we show that the murine Tcl1 gene is expressed early in mouse embryonic development and demonstrates expression in fetal hematopoietic organs as well as in immature T and B cells. Characterization of the murine Tcl1 gene will help in developing a mouse model of CLL and would provide the best opportunity to study and decipher the role of TCL1 in malignant transformation.

Expression of the RET/PTC fusion gene as a marker for papillary carcinoma in Hashimoto's thyroiditis.

Hashimoto's thyroiditis is an inflammatory disease of the thyroid gland with autoimmune etiology. Patients afflicted with Hashimoto's have a higher risk of thyroid malignancies such as papillary thyroid carcinoma. In the present study, we investigated the frequency of papillary thyroid carcinoma specific genes in patients diagnosed with Hashimoto's disease. The newly identified oncogenes RET/PTC1 and RET/PTC3 provide useful and specific markers of the early stages of papillary carcinoma as they are highly specific for malignant cells. Using a sensitive and specific reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we found messenger RNA (mRNA) expression for the RET/PTC1 and RET/PTC3 oncogenes in 95% of the Hashimoto's patients studied. All Hashimoto's patients presenting without histopathologic evidence of papillary thyroid cancer showed molecular genetic evidence of cancer. These data suggest that multiple, independent occult tumors exist in these patients at high frequency.

Induction of differentiation of human olfactory neuroblastoma cells into odorant-responsive cells.

Olfactory neuroblastoma is a rare malignancy of the olfactory mucosa that may be derived from the olfactory epithelium. To characterize this tumor, we cultured olfactory neuroblastoma cells in the presence or absence of growth factors (transforming growth factor alpha and basic fibroblast growth factor) known to affect olfactory tissue and assessed their responsiveness to known odorants by measuring changes in intracellular calcium. Untreated cells did not respond to odorants. Basic fibroblast growth factor treatment had cytotoxic effects, and treated cells did not respond to odorants. Transforming growth factor alpha treatment resulted in the induction of odor responsiveness in these cells. Cells responded to odorants at 100 nM to 100 microM concentrations and responded with both increases and decreases in intracellular calcium. Increases in intracellular calcium were mediated by a calcium influx and were reversibly blocked by compounds known to inhibit second messenger pathways in olfactory receptor neurons. The calcium responses of the olfactory neuroblastoma cells were thus specific to the odorants and similar to those found in olfactory receptor neurons. The results support the notion that olfactory neuroblastoma cells may be of olfactory origin and thus they can be used as a model cell line to study human olfaction.

Genetic mapping and embryonic expression of a novel, maternally transcribed gene Mem3.

To study the molecular function of genes expressed during preimplantation development, we isolated a novel maternal transcript SSEC (Stage Specific Embryonic cDNA)-26 from a partial subtraction library of mouse unfertilized eggs and preimplantation embryos. The SSEC-26 transcript is abundant in the unfertilized egg and also actively transcribed from the newly formed zygotic genome. On the basis of its expression in eggs and embryos, this new mouse gene is named Mem (maternal-embryonic) 3. The genomic locus of Mem3 has been mapped to Chromosome (Chr) 8 near the D8Mit78 marker and the glutaryl CoA dehydrogenase (Gcdh) locus. The deduced amino acid sequence of MEM3 resembles that of the yeast VPS (Vacuolar Protein Sorting) 35 in two separate domains. A cDNA sequence of the potential human homolog of Mem3 has been assembled with partial clones from the EST database and assigned to human Chr 16.