Immunohistochemical analysis of primary breast tumors and tumor-draining lymph nodes by means of the T-cell costimulatory molecule OX-40

Objectives: The OX-40 receptor (OX-40R/CD134) is expressed primarily on activated CD4+ (“helper”) T cells. We have previously reported the presence of OX-40+ T cells in head and neck cancer and melanoma, where they appear to be restricted to tumor compartments (primary tumor infiltrating lymphocytes [TILs] and draining lymph node cells) and therefore may represent the tumor antigen-specific CD4+ T cells. Methods: In order to determine the degree of OX-40R expression, and any relationship with the presence of tumor cells (lobular and/or infiltrating ductal carcinoma), 45 archived paraffin-embedded breast primary tumors and their associated draining (axillary) lymph nodes were retrospectively analyzed using standard immunohistochemical techniques. Results: Seven of 45 primary tumors (16%) and 7 of 29 with lympocytic infiltrates (24%) were noted to have elevated levels of OX-40R+ lymphocytes within the tumor specimens, including 2 of 4 specimens thought to have only “pure” ductal carcinoma in situ (DCIS). No OX-40R+ lymphocytes were noted in normal breast tissue. Twenty-one (43%) patients had axillary metastases at the time of resection. High levels of OX-40R expression was seen in 9 (45%) of these 21 axillary node specimens, whereas no such staining was seen in the node-negative specimens (P <0.001). Furthermore, in a patient thought to be without axillary disease, several subcapsular single-cell metastases were retrospectively discovered near a lone cluster of OX-40R+ lymphocytes. In general, visual inspection showed OX-40R+ T cells to be in close proximity to tumor and often in direct contact with metastatic cells.