Chemokines are small molecules secreted by cells at inflammatory sites that mediate homing and recruitment of immune cells, through G-protein linked receptors. Recently, tumor cells have been shown to express chemokine receptor (CCR)7 that may facilitate lymph node metastasis, and we have shown upregulation of functional CCR7 on metastatic squamous cell carcinoma of the head and neck (SCCHN), compared to nonmetastatic tumors. Our data suggest that NF-KB mediates downstream CCR7-induced activities, as well as the expression of CCR7, itself, and its ligands in an autocrine loop. However, the mechanism and functional importance of CCR7 upregulation in vivo are not well understood. Our central hypotheses are that i) inflammatory signals in the tumor microenvironment lead to upregulation and activation of CCR7 by SCCHN cells, and ii) CCR7-mediated signals promote tumor progression, survival and metastasis. To test these hypotheses, in AIM 1 the effect of inflammatory autocrine/paracrine cytokines on CCR7 expression and activation of NF-KB will be analyzed in SCCHN cells, and the prognostic value of CCR7 expression as a biomarker of clinical disease status in SCCHN specimens will be analyzed by immunohistochemistry.
AIM 2, we will elucidate the intracellular CCR7-mediated signals promoting invasion, survival and cis-platinum resistance of metastatic SCCHN cells. Because inhibition of a single signaling pathway is unlikely to have significant clinical benefit, combination targeting strategies are needed. Thus, the antitumor effect of CCR7 inhibition will be evaluated in vitro, and combined with another important signaling pathway in SCCHN, EGFR, to enhance the translational therapeutic potential.
In AIM 3, the importance CCR7 activity on tumor progression in vivo will be tested in preclinical murine SCCHN model systems. We have observed that CCR7 overexpression increased migratory capacity of a poorly metastatic murine SCCHN tumor cell line. Using this model, the antitumor efficacy of CCR7 inhibition, in modulating tumor growth and metastasis will be tested alone or in combination with EGFR blockade. These data will be compared to tumor formation in pit/pit mice, which are deficient in CCR7 ligands. Overall these studies are designed to identify the EGFR-independent, CCR7-mediated pathways relevant to invasion and survival of SCCHN and to use this information to facilitate the development of CCR7 targeted therapeutic strategies.
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