Suwa 27/9

In order to evaluate host immune response to cancer, many methods have been applied. However, in the field of oral squamous cell carcinoma, evaluation of host immune response on the basis of proliferative activity of tumor-infiltrating T-cells (TIL) has not been reported. Therefore, we applied double immunohistochemical staining of proliferation markers Ki-67 and CD8 to surgically resected and paraffin-embedded tissue sections for 35 cases of oral squamous cell carcinoma. With this method, there was a significant correlation between the percentage of Ki67+CD8+TIL and the intra-tumor epithelium infiltration rate of CD8+TIL (P=0.0237). In the process of analysis, we found that the proliferative activity of CD8+TIL tended to correlate (P=0.0859) with clinical N factor (lymph node metastasis), which was previously reported to suppress host immune response. We therefore assumed there was another factor inducing host immune response. The proliferative activity of CD8+TIL was well correlated with preoperative radiotherapy (P=0.0200) while there was no significant correlation between the proliferative activity of CD8+TIL and other clinical factors; age, tumor size, clinical stage, pathological N factor (P=0.5410, 0.7769, 0.1041, and 0.1072, respectively). Our present results strongly imply that preoperative radiotherapy is a very important factor in oral squamous cell carcinoma inducing host immune response regardless of the clinical factors present. Introduction CD8+ T-cells recognize tumor cells through tumor associated antigen (TAA) presented on the surface of major histocompatibility complex (MHC) class I molecules on the tumor cells via T-cell receptor (TCR) on CD8+ T-cells (1). However, the naïve CD8+ T-cell cannot be adequately activated by the tumor cell itself because activation of the naïve T-cell requires a co-stimulatory signal that is typically mediated by the interaction of a B7 family molecule expressed on the surface of the immune cell and CD28 on the T-cell (1). We had previously reported the importance of the introduction of B7 molecules into tumor cells in order to make the tumor cells play the role of antigen presenting cells (APC) (2,3). On the other hand, the already-activated effector CD8+ T-cells require TAA and MHC class I complex on the tumor surface but do not require a co-stimulatory signal in order to recognize tumor cells for tumor killing (4). In general, the effector CD8+ T-cell itself does not proliferate well at the target organ (5) because T-cell proliferation is induced through the recognition of both first and second signals (6) with the help of CD4+ T-cells in the lymph node (7,8). A recent article revealed that tumor-infiltrating T-cells (TIL) show weak proliferative activity in hepatocellular carcinoma (9). In addition, in renal cell carcinoma (10), and colorectal carcinoma (11) patients, proliferative activity of CD8+TIL is well related with patient prognosis. For head and neck squamous cell carcinoma (HNSCC), no study has observed proliferative activity of TIL in situ to evaluate immune response to tumor cells. Therefore, in the present study we evaluated CD8+TIL proliferative activity by Ki-67 and CD8 double staining on formalin-fixed paraffin-embedded tumor tissue samples. Materials and methods Oral squamous cell carcinoma samples. Surgically removed human oral tumors were fixed in 4% paraformaldehyde in phosphate-buffered saline (PBS) and embedded in paraffin. Sections (4 μm-thick) were prepared and stained with hematoxyline and eosin (H&E) for pathological diagnosis. ONCOLOGY REPORTS 15: 757-763, 2006 757 Preoperative radiotherapy contributes to induction of proliferative activity of CD8+ tumor-infiltrating T-cells in oral squamous cell carcinoma TATSUHIKO SUWA1,2, MASANAO SAIO2, NAOKI UMEMURA1,2, TOMOMI YAMASHITA1, MAKOTO TOIDA1, TOSHIYUKI SHIBATA1 and TSUYOSHI TAKAMI2 Departments of 1Oral and Maxillofacial Sciences, 2Immunopathology, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu, Gifu 501-1194, Japan Received September 27, 2005; Accepted December 1, 2005 _________________________________________ Correspondence to: Dr Masanao Saio, Department of Immunopathology, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu, Gifu 501-1194, Japan E-mail: [email protected]