Positive Interplay Between CD3+ T-lymphocytes and Concurrent COX-2/EGFR Expression in Canine Malignant Mammary Tumors.

BACKGROUND/AIM:The ability of tumors to evade the immune system is one of cancer hallmarks. In breast cancer, it has been demonstrated that the cyclooxygenase-2(+)/ epidermal growth factor receptor(+) (COX-2(+)/EGFR(+)) status might influence tumor microenvironment allowing escape of cancer cells to the immune system. This topic is unknown in canine mammary tumors (CMT). Therefore, the potential relationship between CD3(+) T-lymphocytes and concurrent COX-2/EGFR expression was investigated. MATERIALS AND METHODS:Formalin-fixed paraffin-embedded malignant CMT samples (n=63) were submitted to immunohistochemical staining to detect CD3, COX-2 and EGFR. RESULTS:Tumoral CD3(+) T-lymphocytes were significantly associated with tubular differentiation grade (p=0.006), tumor necrosis (p=0.025), histological grade of malignancy (p=0.027) and presence of lymph node metastasis (p=0.009). A correlation between COX-2 and EGFR was observed (r=0.741, p<0.0001). The COX-2(+)/EGFR(+) group was associated with tumor size (p=0.002), mitotic index (p=0.019), histological grade of malignancy (p=0.035) and presence of lymph node metastasis (p=0.041). CD3(+) T-lymphocytes and COX-2/EGFR groups were significantly associated (p=0.025) and positively correlated (r=0.399; p=0.003). CONCLUSION:The present results suggest that the COX-2(+)/EGFR(+) status may be part of a strategy adopted by tumor cells to evade the cytotoxic tumor-specific immune responses.

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