Abstract P6-06-01: High-grade human cytomegalovirus IEA is associated with expression of COX-2 and 5-LO in human breast cancer samples

Abstract

Abstract Background: The role of cyclooxygenase-2 (COX-2) in breast cancer development and progression has been supported by an increasing number of studies that show the overexpression of COX-2 in all the stages of the disease but in particular, in the metastatic phase. Besides COX-2 and its derived metabolites, 5-lipoxygenase (5-LO) and leukotrienes have also been associated with cancer progression. Human Cytomegalovirus (HCMV) detection in samples from primary BC, sentinel lymph nodes and brain metastases obtained from breast cancer patients' suggests that viral infection may also have a critical role in the development of breast cancer metastasis. Interestingly, in vitro studies showed that HCMV infections induce COX-2 in human fibroblasts, which augments viral replication through a prostaglandin dependent pathway. Thus, our main objective was to investigate whether there is a correlation between HCMV infection and overexpression of COX-2 and 5-LO in breast cancer. If so, HCMV could be an important additional target for breast cancer treatment. Material and Methods: Paraffin embedded breast cancer biopsies (n=48), ductal carcinoma in-situ (DCIS, n=14) and adjacent, benign breast tissue samples (n=29) were retrospectively examined for HCMV-immediate early (IE), HCMV-Late (LA) proteins, COX2 and 5LO by using immunohistochemical techniques established in our laboratory. Clinical data were available from the patients´ hospital files provided from the departments of oncology and pathology at Akershus University Hospital, Norway. All patients underwent direct surgery in 2011. All patients received standard adjuvant treatment according to the Norwegian guidelines. For in vitro studies, breast cancer cell lines (MCF-7, MB-MDA-231 and SKBR3) were infected with HCMV VR1814 strain and levels of COX-2 and 5-LO were determined by qPCR and western blot and immunofluorescence. Results: High levels of COX-2, 5-LO and HCMV-IE were detected mainly in breast cancer samples. High grade HCMV-IE (defined as >50% positive cells in the tumor tissues) was detected in 72% of infiltrating BC and in 28% of DCIS, but it was detected only in 7% of benign, adjacent breast tissue samples. Similarly, high grade COX-2 and 5-LO were detected in 58% and 53% of BC, in 21% and 8% of DCIS, and in 4% and 7% of benign, adjacent breast tissue samples, respectively. We found a statistically significant positive correlation for the levels of HCMV-IE and COX-2 (p=0.001) as well as for HCMV-IE and5-LO (p=0.0002) in infiltrating breast cancer. Furthermore, induction of COX-2 and 5-LO was confirmed in breast cancer cell lines following infection with HCMV was shown at both mRNA and protein level. Conclusion: Our findings confirm a positive correlation of HCMV-IE protein synthesis and overexpression of COX-2 and 5-LO in infiltrating breast cancer, DCIS and benign, adjacent breast tissue samples, which is consistent with the up-regulation of these enzymes in breast cancer cells infected with HCMV. These results suggest that the inflammation driven by COX-2 and 5-LO in human breast cancer might be induced by HCMV infections and lead to tumor progression. Thus, anti-viral therapy should be considered as an additional experimental treatment in selected breast cancer patients. Citation Format: Costa H, Touma J, Davoudi B, Geisler J, Vetvik K, Söderberg Naucler C, Rahbar A. High-grade human cytomegalovirus IEA is associated with expression of COX-2 and 5-LO in human breast cancer samples [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-06-01.