Trial Information

Cancer of the larynx and hypopharynx remains the third most common head and neck malignancy,
constituting about 20% of all tumors. Squamous cell carcinoma (SCC) is the most common
histopathologic type of the laryngeal and hypopharyngeal malignancies, accounting for more
than 90% of cancers occurring in this region (1). Lymph node metastasis directly affects
the prognosis of patients with laryngeal and hypopharyngeal SCC (2). The presence of lymph
node metastasis significantly reduces the probability of regional control and survival (3).
Furthermore, the American Cancer Society shows no trend toward an improvement in 5-year
survival rates between patients diagnosed in 1974 to 1976 and 1989 to 1995 (4).

Tumor metastasis is the hallmark of malignancy, and is probably a result of the interaction
between tumor cells and a supportive microenvironment. Malignant cells that have the
capability to metastasize to a particular organ may have various properties supporting their
tissue invasion or growth such as enhanced adherence to the microvascular cells of the
organ, higher responsiveness to chemotactic signals released from the target organs and
increased response to local soluble or tissue associated growth signals in the target organ
(5,6). Though there are several molecules expressed or produced in cancer cells are
considered the metastatic factors, it remains unknown which factors produced by the lymph
node or tissue affect the metastasis of cancer cells.

Chemokines are a large family of pro-inflammatory polypeptide cytokines, consisting of small
(7–15 kDa), structurally related heparin-binding proteins. They are grouped into CXC
chemokines and CC chemokines, on the basis of the characteristic presence of four conserved
cysteine residues (7-9). Chemokines are produced locally in the tissues and act on target
cells through G-protein-coupled receptors, which are characterized structurally by seven
transmembrane spanning domains. Chemokines are involved in the attraction and activation of
mononuclear and polymorphonuclear leukocytes to sites of inflammatory responses, bacterial
or viral infections, allergy, cardiovascular diseases and wound healing (5, 9-14).
Chemokines are known to also function as regulatory molecules in the leukocyte maturation,
trafficking, and homing of T and B lymphocytes, in the development of lymphoid tissues, and
in dendritic cell maturation (15,16). Other functions of chemokines have been described
more recently, particularly for the CXC chemokines. The role of chemokines in malignant
tumors is not clear yet. Some chemokines may enhance innate or specific host immunity
against tumor dissemination. On the other hand, some may advocate tumor growth and
metastasis by promoting tumor cell proliferation, migration or angiogenesis in tumor tissue
(5). Reports have suggested that several types of cancer, such as breast (17), ovary (18),
prostate (19), kidney (20), brain (21), lung (22), and thyroid (23), expressed the chemokine
receptor and used the chemokines to metastasize to the target organ as in the homing of
hematopoietic cells.

SDF-1 belongs to the CXC chemokine family and is a ligand for CXCR4 (24, 25). SDF-1 was
initially cloned by Tashiro et al. (26) and later identified as a growth factor for B cell
progenitors, a chemotactic factor for T cells and monocytes, and in B-cell lymphopoiesis and
bone marrow myelopoiesis (24, 27–28). Most of the chemokine receptors interact with
pleural ligands, and vice versa, but the SDF-1/CXCR4 receptor ligand system has been shown
to involve a one-on-one interaction (29, 30). Recently, several studies have been conducted
to detect the mRNA expression of CXCR4 and SDF-1 in solid tumors. The results are not
uniform, and the relevance to cancer progression is not determined (31, 32). Sehgal et al.
(31, 33) concluded that CXCR4 plays an important role of proliferation and tumorigenic
properties of human glioblastoma tumors. Muller et al. (34) have reported that SDF-1
signaling through CXCR4 interaction appears to determine the directional migration of breast
cancer cells through the basement membrane. Furthermore in vivo, the interaction between
SDF-1 and CXCR4 significantly represses the metastatic potential of breast cancer cells to
lymph node and lung. Barnard and his colleagues (35, 36) showed the contrary results that
CXCR4 mRNA expression was reduced in hepatocellular carcinoma tissue when compared with
noncancerous tissue, but was not changed in colon, esophageal, and gastric cancer. They
also found reduced mRNA expression of SDF-1 in these malignant tissues (32). Thus, there is
a diversity of views on the role of the SDF-1/CXCR4 receptor ligand system in malignant
tissues. And such studies are limited in laryngeal and hypopharyngeal cancer.

Since metastasis of laryngeal and hypopharyngeal cancer occur frequently through the
lymphatic system, and metastasis is a key prognostic factor for the disease. Evaluation of
the relationship between SDF-1/CXCR4 system and metastasis in laryngeal and hypopharyngeal
cancer could help us understand whether this system is important in the metastasis of this
disease.

We hypothesized that SDF-1/CXCR4 (ligand/receptor) system plays an important role in
laryngeal and hypopharyngeal cancer metastasis. To test this hypothesis, we will
investigate (1) the distribution of CXCR4 protein expression in cancer and lymph node
tissues by means of immunohistochemical analysis of tissue samples obtained from surgical
operation, (2) the relationship between CXCR4 expression and clinicopathological findings
with special reference to cancer metastasis, (3)the expression of SDF-1 and CXCR4 in the
cancer cell lines cells and tissues, (4) the chemotactic activity and the growth-promoting
effect of SDF-1 on cancer cell lines cells, (5) the role of Src, MAPK, and Akt signal
transduction pathway in this response, (6) the effect of the blocking agent on this
response.

Undoubtedly, the findings of this study will help us understand whether SDF-1/CXCR4 system
could be a focal point of anti-cancer research. If laryngeal and hypopharyngeal SCC that
express high levels of CXCR4 show a consistently higher incidence of lymphatic and distant
metastasis, then blocking SDF-1/CXCR4 signaling may be a novel approach to inhibit
metastasis in these patients. The development of SDF-1/CXCR4 system antagonists will
provide opportunity to improve the survival rate.