A thyroid tumor-specific antigen formed by the fusion of two self proteins

RET-mediated modulation of tumor microenvironment and immune response in multiple endocrine neoplasia type 2 (MEN2)

Medullary thyroid carcinomas (MTC) arise from thyroid parafollicular, calcitonin-producing C-cells and can occur either as sporadic or as hereditary diseases in the context of familial syndromes, including multiple endocrine neoplasia 2A (MEN2A), multiple endocrine neoplasia 2B (MEN2B) and familial MTC (FMTC). In a large fraction of sporadic cases, and virtually in all inherited cases of MTC, activating point mutations of the RET proto-oncogene are found. RET encodes for a receptor tyrosine kinase protein endowed with transforming potential on thyroid parafollicular cells. As in other cancer types, microenvironmental factors play a critical role in MTC. Tumor-associated extracellular matrix, stromal cells and immune cells interact and influence the behavior of cancer cells both in a tumor-promoting and in a tumor-suppressing manner. Several studies have shown that, besides the neoplastic transformation of thyroid C-cells, a profound modification of tumor microenvironment has been associated to the RET FMTC/MEN2-associated oncoproteins. They influence the surrounding stroma, activating cancer-associated fibroblasts (CAFs), promoting cancer-associated inflammation and suppressing anti-cancer immune response. These mechanisms might be exploited to develop innovative anti-cancer therapies and novel prognostic tools in the context of familial, RET-associated MTC.

Intracellular signal transduction and modification of the tumor microenvironment induced by RET/PTCs in papillary thyroid carcinoma

RET gene rearrangements (RET/PTCs) represent together with BRAF point mutations the two major groups of mutations involved in papillary thyroid carcinoma (PTC) initiation and progression. In this review, we will examine the mechanisms involved in RET/PTC-induced thyroid cell transformation. In detail, we will summarize the data on the molecular mechanisms involved in RET/PTC formation and in its function as a dominant oncogene, on the activated signal transduction pathways and on the induced gene expression modifications. Moreover, we will report on the effects of RET/PTCs on the tumor microenvironment. Finally, a short review of the literature on RET/PTC prognostic significance will be presented.

Identification of functionally distinct TRAF proinflammatory and phosphatidylinositol 3-kinase/mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (PI3K/MEK) transforming activities emanating from RET/PTC fusion oncoprotein

Thyroid carcinomas that harbor RET/PTC oncogenes are well differentiated, relatively benign neoplasms compared with those expressing oncogenic RAS or BRAF mutations despite signaling through shared transforming pathways. A distinction, however, is that RET/PTCs induce immunostimulatory programs, suggesting that, in the case of this tumor type, the additional pro-inflammatory pathway reduces aggressiveness. Here, we demonstrate that pro-inflammatory programs are selectively activated by TRAF2 and TRAF6 association with RET/PTC oncoproteins. Eliminating this mechanism reduces pro-inflammatory cytokine production without decreasing transformation efficiency. Conversely, ablating MEK/ERK or PI3K/AKT signaling eliminates transformation but not pro-inflammatory cytokine secretion. Functional uncoupling of the two pathways demonstrates that intrinsic pro-inflammatory pathways are not required for cellular transformation and suggests a need for further investigation into the role inflammation plays in thyroid tumor progression.

Thyroid cancer and inflammation

Some cancer types are strongly associated with chronic inflammatory or infectious diseases whereas others are not, but an inflammatory component is present in most human neoplastic lesions. This review focuses on various aspects of thyroid cancer and inflammation. The incidence of thyroid cancer, in particular of well-differentiated papillary thyroid carcinomas (PTCs), is increased in autoimmune thyroid diseases such as Hashimoto's thyroiditis. Thyroid cancer often has an inflammatory cell infiltrate, which includes lymphocytes, macrophages, dendritic cells and mast cells, whose role in thyroid cancer is still not completely understood. However, most experimental evidence suggests these cells exert a protumorigenic function. Moreover, oncoproteins typically expressed in human PTCs, such as RET/PTC, RAS, and BRAF, trigger a proinflammatory programme in thyreocytes. These data suggest that inflammatory molecules are promising targets for thyroid cancer therapy.

The tight relationship between papillary thyroid cancer, autoimmunity and inflammation: clinical and molecular studies

OBJECTIVE

The recent concept that oncogenes responsible for thyroid neoplastic transformation are able to elicit an inflammatory protumourigenic microenvironment raises interest in further studies on papillary thyroid cancer (PTC) associated with thyroid autoimmunity.

PATIENTS

The clinical and molecular features, and the expression of inflammation-related genes, were investigated in a large series of PTCs with and without associated thyroiditis (groups A, n = 128 and B, n = 215).

RESULTS

The two groups did not show significant differences in clinical and prognostic features, whereas they harboured a significantly different genetic background (P = 0.001), with RET/PTC1 being more represented in PTCs associated with autoimmunity, and BRAF(V600E) in patients with PTC alone. A RET/PTC rearrangement was also found in 41% of non-neoplastic thyroiditis tissues, contralateral to tumours harbouring either RET/PTC or BRAF mutations. The expression of genes encoding CCL20, CXCL8 and l-selectin was significantly higher in PTC specimens (either with RET/PTC, BRAF(V600E) or unknown genetic lesion) compared with normal thyroid samples. On the contrary, thyroiditis showed l-selectin expression levels even higher than PTCs, but CCL20 and CXCL8 levels comparable with normal tissues.

CONCLUSIONS

The present data extend the knowledge about the tight relationships among oncogenes, thyroiditis and thyroid cancer. A different genetic background among PTCs with and without associated autoimmunity has been firstly demonstrated. The strong association between RET/PTC1 and thyroiditis points to a critical role of this oncoprotein in the modulation of the autoimmune response. Moreover, preliminary expression studies, indicating enhanced expression of inflammatory molecules in PTCs, suggest a proinflammatory, nonautoimmune relationship between thyroiditis and thyroid cancer.

Oncoprotein signaling mediates tumor-specific inflammation and enhances tumor progression

The RET/PTC3 (RP3) fusion protein is an oncogene expressed during the development of thyroid cancer and in thyroid epithelial cells of patients with Hashimoto's thyroiditis. RP3 has two immunological properties: 1) it encodes a chimeric protein including peptides that may be targets of antitumor immune responses and 2) it is a tyrosine kinase that can activate NF-kappaB transcriptional programs, induce secretion of proinflammatory mediators, and stimulate innate immunity. To distinguish the antigenic properties of the RP3 oncoprotein from its signaling function, a transplantable tumor system was developed. Tumors expressing the functional, but not mutant, form of RP3 show enhanced infiltration of CD8(+) lymphocytes, myeloid-derived CD11b(+)Gr1(+) cells, and enhanced growth in immunocompetent mice. In contrast, RP3 signaling mutant-expressing tumors maintained enhanced infiltration of CD8(+) lymphocytes did not enhance recruitment of CD11b(+)Gr1(+) cells and showed a decreased tumor incidence. These results implicate a role for RP3 function in enhancing a tumor-suppressive innate inflammatory response. These experiments support a mechanism whereby oncogenes can directly recruit and activate innate and adaptive immune cells, resulting in enhanced tumor progression.

Papillary thyroid cancer, although strongly associated with lymphocytic infiltration on histology, is only weakly predicted by serum thyroid auto-antibodies in patients with nodular thyroid diseases

OBJECTIVE

We evaluated the association between thyroid autoimmunity and thyroid cancer in a retrospective series of unselected thyroid nodules submitted to fine-needle aspiration (FNA) cytology.

DESIGN

Anti-thyroid antibodies (TAb) were measured in patients with multinodular goiter (MNG) and single/isolated thyroid nodule (S/I) submitted to FNA. Thyroid lymphocytic infiltration (LI) on histology was studied in a subgroup of patients submitted to thyroidectomy; 13,021 patients were included: on cytology 622 had papillary thyroid cancer (c- PTC) and 12,399 benign thyroid nodular diseases (c-BTN). LI was evaluated in histological samples of 688 patients: 304 with PTC (h-PTC) and 384 with BTN (h-BTN).

RESULTS

TAb prevalence was not different in c-BTN and c-PTC (38.7% vs 35.6%). TAb were more frequent in c-BTN than c-PTC in females with MNG (40.1% vs 32.5%, p=0.02), and in c-PTC than in c-BTN in males with S/I (31.2% vs 20.4%, p=0.02) and, although not significantly, in females younger than 30 yr (35.1% vs 30.7%). The frequency and severity of LI was significantly higher in h-PTC than h-BTN, both in MNG (82.5% vs 45.0%, p<0.001) and S/I (85.6% vs 71.0%, p<0.001), but a higher number of patients with h-PTC had negative circulating TAb, despite the presence of moderate/severe LI.

CONCLUSIONS

TAb are weakly associated to PTC in males and young females, while they are more frequent in older females with BTN. The frequency and severity of LI is significantly higher in PTC than in BTN, but in cancer patients TAb are frequently negative, despite the evidence of histological thyroiditis. These data suggest that different kinds of immune response may be involved in PTC and BTN.

RET/PTC rearrangement occurring in primary peritoneal carcinoma

RET/PTC rearrangements are initiating events in the development of a significant proportion of papillary thyroid carcinomas. Activated RET/PTC mutations are thought to be restricted to thyroid disease, but this study proposes that these events may also occur in nonthyroid tumors. A total of 57 nonthyroid papillary tumors were examined for RET/PTC rearrangements using interphase fluorescence in situ hybridization, Taqman reverse transcriptase polymerase chain reaction, and immunohistochemistry. Taqman single nucleotide polymorphism detection was used to analyze for expression of mutated BRAF T1799A. In all, 20% (3/15) of primary peritoneal carcinoma had detectable RET/PTC1 rearrangements by all 3 methodologies. A further case of similar histotype had an alternate RET/ PTC rearrangement. No RET/PTC1 rearrangements were detected in the remaining tumor cohort. All 57 tumors were homozygous for wild-type BRAF. The results indicate that RET/PTC rearrangements occur in a small subset of nonthyroid papillary tumors. These rearrangements may not be directly implicated in tumor growth; rather representing "passenger" mutations reflecting RET instability in secondary tumor subclones.

Gene expression in RET/PTC3 and E7 transgenic mouse thyroids: RET/PTC3 but not E7 tumors are partial and transient models of human papillary thyroid cancers

We studied gene expression profiles in two mouse models of human thyroid carcinoma: the Tg-RET/PTC3 (RP3) and Tg-E7 mice. RP3 fusion gene is the most frequent mutation found in the first wave post-Chernobyl papillary thyroid cancers (PTCs). E7 is an oncoprotein derived from the human papillomavirus 16 responsible for most cervical carcinoma in women. Both transgenic mice develop thyroid hyperplasia followed by solid differentiated carcinoma in older animals. To understand the different steps leading to carcinoma, we analyzed thyroid gene expression in both strains at different ages by microarray technology. Important biological processes were differentially regulated in the two tumor types. In E7 thyroids, cell cycle was the most up-regulated process, an observation consistent with the huge size of these tumors. In RP3 thyroids, contrary to E7 tumors, several human PTC characteristics were observed: overexpression of many immune-related genes, regulation of human PTC markers, up-regulation of EGF-like growth factors and significant regulation of angiogenesis and extracellular matrix remodeling-related genes. However, similarities were incomplete; they did not concern the overall gene expression and were not conserved in old animals. Therefore, RP3 tumors are partial and transient models of human PTC. They constitute a good model, especially in young animals, to study the respective role of the biological processes shared with human PTC and will allow testing drugs targeting these validated variables.

Gene expression and the biological phenotype of papillary thyroid carcinomas

The purpose of this paper is to correlate the molecular phenotype of papillary thyroid carcinoma (PTC) to their biological pathology. We hybridized 26 PTC on microarrays and showed that nearly 44% of the transcriptome was regulated in these tumors. We then combined our data set with two published PTC microarray studies to produce a platform- and study-independent list of PTC-associated genes. We further confirmed the mRNA regulation of 15 genes from this list by quantitative reverse transcription-PCR. Analysis of this list with statistical tools led to several conclusions: (1) there is a change in cell population with an increased expression of genes involved in the immune response, reflecting lymphocyte infiltration in the tumor compared to the normal tissue. (2) The c-jun N-terminal kinase pathway is activated by overexpression of its components. (3) The activation of ERKK1/2 by genetic alterations is supplemented by activation of the epidermal growth factor but not of the insulin-like growth factor signaling pathway. (4) There is a downregulation of immediate early genes. (5) We observed an overexpression of many proteases in accordance with tumor remodeling, and suggested a probable role of S100 proteins and annexin A2 in this process. (6) Numerous overexpressed genes favor the hypothesis of a collective migration mode of tumor cells.

Possible reasons for different pattern disappearance of thyroglobulin and thyroid peroxidase autoantibodies in patients with differentiated thyroid carcinoma following total thyroidectomy and iodine-131 ablation

The purpose of this study was to reveal some possible factors for the differences between the pattern of disappearance of thyroglobulin autoantibodies (anti-Tg) and thyroid peroxidase autoantibodies (anti-TPO) in patients with differentiated thyroid carcinoma following thyroidectomy and iodine-131 ablation. Patients with a history of follicular cell derived cancer (papillary, follicular, both papillary and follicular, Hürthle cell) and high pre-operative titers of anti-TPO and/or anti-Tg autoantibodies were retrospectively studied. Thyroglobulin (Tg) levels were measured using radio-immunometric assay (RIA). Anti-Tg and anti-TPO levels during the first 6 yr' follow-up were measured by passive agglutination, during the following 10 yr by ELISA method and during the last 2 yr by chemiluminescence assay. A statistically significant difference was observed between median time (72 months) of disappearance of anti-TPO and median time (39 months) of disappearance of anti-Tg in patients with complete ablation of thyroid tissue, following iodine-131 administration (p=0.0395, Logrank statistic=4.24, Kaplan-Meier method). A statistically significant difference was observed between median time (106 months) of disappearance of anti-TPO and median time (33 months) of disappearance of anti-Tg in patients >45 yr of age (p=0.034) and between median time (111 months) of disappearance of anti-TPO and median time (41 months) of disappearance of anti-Tg in patients with tumor size <2 cm (p=0.0175). We concluded that patients with differentiated thyroid carcinoma and pre-surgical elevated titers of both Tg and anti-TPO tend to become earlier anti-Tg seronegative. Although tumor size and age may influence the pattern of thyroid autoantibody reduction, the exact reasons for the different rhythm of autoantibodies decrease must further be evaluated.

Thyroid cancer and the immune system: a model for effective immune surveillance

Differentiated thyroid cancers, including papillary and follicular variants, are a useful model with which to examine interactions between cancer and the immune system. Differentiated thyroid cancers are detected in only 20,000 individuals annually in the USA, but thyroid microcarcinomas (< 1 cm in diameter) are far more common. This suggests that the immune system might restrain the growth of these microcarcinomas. On the clinical level, patients with lymphocytes that infiltrate into papillary thyroid cancer have improved survival, supporting the notion that immune system activation might improve this. Together, these observations suggest that the growth and distant spread of thyroid carcinoma are suppressed by mechanisms of immune surveillance, possibly involving lymphocytes, macrophages and their secreted products. In this review, we examine the general hypothesis of immune surveillance and the data pertaining to the roles of lymphocytes, dendritic cells and cytokines in the immune response against thyroid cancers.

Well differentiated thyroid carcinoma is associated with human lymphocyte antigen D-related 11 in Eastern Hungarians: a case of changing circumstances

BACKGROUND

Using serologic human lymphocyte antigen (HLA) typing, the authors previously described a strong association between well differentiated thyroid carcinoma and HLA D-related 1 (HLA-DR1) in a population of unselected patients from Eastern Hungary.

METHODS

In the current study, the authors used polymerase chain reaction-single strand conformational polymorphism to determine the HLA-DR type in 75 patients with well differentiated thyroid carcinoma from the same area as their previous population, and they compared the current results with the results from a group of 170 healthy controls.

RESULTS

A significant increase in HLA-DR11, rather than HLA-DR1, was observed in patients with well differentiated thyroid carcinoma among a population of patients from the same area that was studied previously. After excluding technical reasons to account for differences in disease association, they postulated that interim environmental factors, possibly radiation fall-out, may have resulted in differences in genetic susceptibility to thyroid carcinoma. Consideration of the potential antigenic peptides that may be restricted by the two HLA-DR alleles may have allowed for the binding of similar peptides to initiate an immune response, likely leading to progressive immunomodulation of the tumor. Discriminat function analysis indicated a significant relation between tumor size and metastases and less lymphocytic infiltration of the tumor, but this was not related to HLA-DR phenotypes.

CONCLUSIONS

The authors found that the study of major histocompatability complex alleles holds promise for understanding the events that initiate and maintain tumor immunomodulation.

Gene therapy for thyroid cancer

Thyroid carcinomas are suitable targets for gene therapy because they can be highly lethal on one hand, while being susceptible to specific tumour targeting on the other hand. Several gene therapy modalities have been evaluated so far in experimental models of thyroid cancer, including tumour suppressor gene replacement, oncogene inhibition, suicide gene therapy, immunotherapy, antiangiogenesis, and viral oncolysis. All of these strategies have shown promising results, but clinical studies are lacking. Based on the clinical experience achieved in a pilot study in patients with advanced thyroid cancer and on clinical results in other types of solid cancer, it is suggested that combined gene therapy approaches, as well as multimodality therapeutic regimens, including gene therapy and conventional treatments, should be pursued to achieve clinically significant results.

Detection and molecular characterisation of thyroid cancer precursor lesions in a specific subset of Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) represents the most common cause of hypothyroidism and nonendemic goiter, but its clinical and pathological heterogeneity opens the question if this disease should be more properly considered as a spectrum of different thyroid conditions rather than as a single nosological entity. In this study, we analysed 133 cases of HT for the expression of galectin-3, a lectin molecule involved in malignant transformation, apoptosis and cell cycle control. An unexpected expression of galectin-3 was demonstrated in a subset of HT together with the presence of HBME-1, c-met and cyclin-D1 that are also involved in malignant transformation and deregulated cell growth. Furthermore, a loss of allelic heterozygosity in a specific cancer-related chromosomal region was demonstrated in some HT harbouring galectin-3-positive follicular cells, by using laser capture microdissection. On the basis of the morphological and molecular findings we identified four subsets of HT: (a) HT with classic features of chronic autoimmune thyroiditis; (b) HT associated to hyperplastic/adenomatous lesions; (c) HT harbouring thyroid cancer precursors; (d) HT associated to unequivocal thyroid microcarcinomas. Our findings provide a well-substantiated morphological and molecular demonstration that HT may include a spectrum of different thyroid conditions ranging from chronic autoimmune thyroiditis to thyroiditis triggered by specific immune-response to cancer-related antigens.

Interleukin 24 is induced by the RET/PTC3 oncoprotein and is an autocrine growth factor for epithelial cells

Thyroid cancers, like hematological malignancies, are commonly associated with chromosomal translocations leading to the formation of fusion proteins. Through altered signaling by fusion proteins, cell death and survival pathways are disrupted and the physiological balance of cell-cell communication may be lost. A consequence of this disruption is the release of factors by stressed cells that alert the host. One type of host response is leukocytic infiltration that may develop into chronic inflammation or autoimmune disease. Although inflammation can be associated with neoplastic tissue, the mechanism driving this process is largely unknown. Therefore, to address the mechanism of cancer inflammation we investigated the effects of an oncogene in a murine model system. A comprehensive genetic analysis revealed several soluble factors that were induced by RET/papillary thyroid carcinoma (PTC)3 gene expression including several proinflammatory cytokines, chemokines and immunologically relevant costimulatory molecules. Following a large genetic screen using RP3-expressing thyroid cells, we identified a highly abundant transcript and later identified it as interleukin 24 (Il24), a cytokine with diverse tumor suppressor and inflammatory activities. We show that RET/PTC3 induces Il24 expression in rat thyrocytes and that this expression is dependent on the signaling properties of its tyrosine kinase. Likewise, RET/PTC3 induces large amounts of Il24 following expression in murine thyrocytes, but its expression is dramatically reduced in poorly differentiated carcinomas, a finding that parallels the loss of RET/PTC3 expression. Consistent with its behavior as a tumor suppressor, the loss of Il24 coincided with the loss of RET/PTC3 in poorly differentiated mouse tumors. A functional role of Il24 in the autocrine growth/survival of RET/PTC3-expressing thyroid cells was identified helping to support its role in cellular transformation. These data suggest that the induction of Il24 by oncogenes may support tumor growth at the early stages of cancer.

Regulation of Signal Transducer and Activator of Transcription 1 (STAT1) and STAT1-Dependent Genes by RET/PTC (Rearranged in Transformation/Papillary Thyroid Carcinoma) Oncogenic Tyrosine Kinases

Chimeric RET/PTC (rearranged in transformation/papillary thyroid carcinoma) oncoproteins are constitutively active tyrosine kinases found in thyroid papillary carcinoma and nonneoplastic Hashimoto’s thyroiditis. Although several proteins have been identified to be substrates of RET/PTC kinases, the pathogenic roles played by RET/PTC in malignant and benign thyroid diseases and the molecular mechanisms that are involved are not fully understood. We found that RET/PTC expression phosphorylates the Y701 residue of STAT1, a type II interferon (IFN)-responsive protein. RET/PTC-mediated signal transducer and activator of transcription 1 (STAT1) phosphorylation requires RET/PTC kinase activity to be intact but other tyrosine kinases, such as Janus kinases or c-Src, are not involved. RET/PTC-induced STAT1 transcriptional activation was not inhibited by suppressor of cytokine signaling-1 or -3, or protein inhibitors of activated STAT3 [(protein inhibitor of activated STAT (PIAS3)], but PIAS1 strongly repressed the RET/PTC-induced transcriptional activity of STAT1. RET/PTC-induced STAT1 activation caused IFN regulatory factor-1 expression. We found that STAT1 and IFN regulatory factor-1 cooperated to significantly increase transcription from type IV IFN-γresponsive promoters of class II transactivator genes. Significantly, cells stably expressing RET/PTC expressed class II transactivator and showed enhanced de novo membrane expression of major histocompatibility complex (MHC) class II proteins. Furthermore, RET/PTC1-bearing papillary thyroid carcinoma cells strongly expressed MHC class II (human leukocyte-associated antigen-DRα) genes, whereas the surrounding normal tissues did not. Thus, RET/PTC is able to phosphorylate and activate STAT1. This may lead to enhanced MHC class II expression, which may explain why the tissues surrounding RET/PTC-positive cancers are infiltrated with lymphocytes. Such immune response-promoting activity of RET/PTC may also relate to the development of Hashimoto’s thyroiditis.

Proinflammatory mediators and genetic background in oncogene mediated tumor progression

RET/PTC3 (RP3) is an oncogenic fusion protein which is frequently expressed in papillary thyroid carcinomas and has been detected in thyroid tissue from patients diagnosed with Hashimoto's thyroiditis. The constitutive activation of the tyrosine kinase domain in the carboxyl-terminal end of RP3 induces signaling pathways within thyrocytes and causes cellular transformation. One of the signaling pathways activated in RP3-expressing cells involves the activity of the transcription factor NF-kappaB and the production of downstream targets including GM-CSF and macrophage chemotactic protein 1. These factors are known to be immunostimulatory, making RP3 a molecular adjuvant and potentially promoting tissue-specific immunity. However compelling, these in vitro data do not reliably predict gene function in vivo or the cumulative effects of time-dependent processes such as angiogenesis, inflammation, or the influence of genetic background. To address these issues, we analyzed the production of proinflammatory mediators in mouse thyroid organs and demonstrate consistency with in vitro studies performed previously that Il1alpha, Il1beta, Il6, and Tnfalpha and the enzyme Cox2 are produced by RP3-transgenic thyroid tissue, but absent from nontransgenic thyroids. Furthermore, we find that that the genetic background of the host is important in the observed RP3-induced inflammation and tumor progression. These findings provide support for the notion that oncogene-induced cytokine secretion is important for the development and progression of thyroid carcinomas in genetically permissive hosts.

Tyrosine kinase oncoprotein, RET/PTC3, induces the secretion of myeloid growth and chemotactic factors

Differentiated thyroid carcinomas are the most frequent endocrine neoplasms, but account for few cancer-related deaths. Although the indolent growth of these cancers correlates well with longevity, the biological basis for this good prognosis is not known. In contrast, two of the most frequent autoimmune diseases involve the thyroid suggesting a high propensity for this organ to invoke destructive immunity. Unfortunately, the mechanism linking malignancy and autoimmunity is not clear, although the expression of the oncogenic fusion protein RET/PTC3 (RP3) in both of these disorders may provide a clue. Interestingly, the signaling caused by activated RET kinase involves overlapping pathways and some common to the inflammatory response. Accordingly, we analyzed the function of RP3 and a mutant RP3 molecule to induce proinflammatory pathways in thyroid epithelial cells. Indeed, we find that RP3 alone causes increases in nuclear NF-kappaB activity and secretion of MCP-1 and GM-CSF. Finally, transfer of RP3-expressing thyrocytes into mice in vivo attracted dense macrophage infiltrates, which lead to rapid thyroid cell death. Further, cytokine synthesis and inflammation was largely abrogated by mutation of RP3 Tyr588; an important protein-binding site for downstream signaling. Together, these studies implicate oncogene-induced cytokine-signaling pathways in a new mechanism linking inflammation with cancer.