Tumor Progression Tumor-Specific Inflammation and Enhances Oncoprotein Signaling Mediates

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- (cid:1) B 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 (cid:2) lymphocytes, myeloid-derived CD11b (cid:2) Gr1 (cid:2) cells, and enhanced growth in immunocompetent mice. In contrast, RP3 signaling mutant-expressing tumors maintained enhanced inﬁltration of CD8 (cid:2) lymphocytes did not enhance recruitment of CD11b (cid:2) Gr1 (cid:2) 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. The Journal of Immunology, 2009, 182: 5498–5506. sensitivity to changes in the inﬂammatory microenvironment due to paracrine cytokines and chemokines contributed by activated lymphocytes (55). Our previous studies correlated RP3- mediated transformation and coexistent inﬂammation with enhanced development of thyroid hyperplasia in mice transgenic for thyroid-spe-ciﬁc expression of RP3 (44). In these mice however, the inﬂuence of RP3-mediated transformation was not separated from any positive growth inﬂuences contributed by local inﬂammatory inﬁltrates. In this study, the use of 4102-PRO progressor tumor model provided a means to analyze the inﬂuence of RP3 inﬂammatory functions on tumor progression independent of its function in cellular transformation. We showed equivalent in vitro growth rates of the 4102 tumor cells expressing RP3 or vector control constructs, indicating that RP3 kinase signaling does not interfere with the transformation and cell growth phenotype of the parental 4102 tumor cells. When transplanted into C3H/SCID-immunodeﬁcient mice, 4102 tumors expressing RP3 progressed with a similar frequency and rate as tumors expressing mutant RP3 Y588F or control tumors, corroborating the in vitro growth rate data and conﬁrming that RP3 function did not enhance intrinsic cell growth rate. We observed enhancement of both tumor incidence and growth rate only when tumors were grown in mice with an intact adaptive immune system, suggesting that the contribution of T cells is necessary. RP3 kinase function provided a progressive advantage for tumors, despite increased inﬁltration of CD8 (cid:1) lymphocytes, suggesting that tumor-inﬁltrating lymphocytes may be playing a supportive role. We ﬁnd that RP3 expression also correlates with an enhanced innate cell inﬁltrate. This observed inﬁltration is likely the result of the mediators synthesized from RP3-expressing cells consequent to the activation of NF- (cid:1)