Abstract A035: Infection of primary mammary fibroblasts with cytomegalovirus coordinately increases autotaxin-lysophosphatidate-inflammatory signaling, which could increase breast cancer metastasis
Authors: Khan Humayara , Tang Xiaoyun , Wuest Frank , Brindley David N. , Hemmings Denise G. 
Published: November 2024

Background: Metastatic breast cancer is the most prevalent cause of mortality by cancer-related deaths in women. Our group showed that the 63% of Canadian breast cancer patients who were infected with CMV were 5.6-times more likely to develop Stage IV cancers with reduced relapse-free survival. Also, the metastatic phenotype of breast tumors and the number and sizes of lung metastases were increased in mice with latent infections. Fibroblasts are important sites of CMV infection. Cancer-associated fibroblasts (CAFs) are also major sites of autotaxin (ATX) secretion in breast tumors, whereas ATX production and CMV infection in breast cancer cells is negligible. ATX produces lysophosphatidate (LPA), which increases inflammatory cytokine production that stimulates further ATX secretion in a feedforward cycle. LPA promotes breast tumor growth and metastasis by signaling through six G protein-coupled receptors. Signaling is terminated by lipid phosphate phosphatases (LPPs)-1 and -3, which degrade LPA and are decreased in breast tumors. Hypothesis: Breast cancer metastasis could be increased by active CMV infection of CAFs through increased inflammation and LPA signaling. Results: Quiescent fibroblasts isolated and cultured from mammary tissue of non-tumor bearing mice (n&gt;3) produced negligible quantities of ATX. LPA signaling was coordinately promoted in these primary fibroblasts infected for 48 h with 1 MOI of mouse CMV (n=3) with a 5-fold increase in mRNA for ATX (p=0.008), increased mRNAs for LPA2,3,4 receptors (p&lt;0.05) and decreased mRNA expressions for LPP1 and LPP3 (p&lt;0.05). An increase in the secretion of granulocyte monocyte-colony stimulating factor of 548 pg/ml (p=0.01) and Interleukin-6 by 8307 pg/ml (p=0.03) was observed post infection (n=5), thus creating a pro-inflammatory environment. Increased mRNA expression of fibroblast markers, including alpha-smooth muscle actin (p=0.005), fibroblast-associated protein (p=0.007), epidermal growth factor receptor (EGFR) (p=0.001) and transforming growth factor- ß receptor 1 (TGF-ßR1) (p=0.03) was also observed post-infection (n=3). The results were analyzed by student’s t-test. Assessment of these factors in breast cancer patients (n=1100) using the Tumor Immune Estimation Resource Analysis showed a positive correlation in the expression of EGFR and TGF-ßR1 with the LPA3,4 receptors (p&lt;0.05). Conclusion: The changes in expression of ATX, LPA receptors and LPPs in CMV- infected fibroblasts are consistent with increased metastasis. Our results show that mCMV infection of primary mammary fibroblasts dramatically reprograms them to express CAF-like properties and promotes ATX-LPA-inflammatory signaling. CAFs are a major constituent of the tumor stroma. They promote tumor progression by secreting factors such as ATX, which increases metastasis, fibrosis and favors immunosuppression. Our results support the use of pharmacological agents to block signaling by the ATX-LPA-inflammatory cycle to treat breast and other cancers, especially for the majority of patients who are infected with CMV.

Citation Format: Humayara Khan, Xiaoyun Tang, Frank Wuest, David N. Brindley, Denise G. Hemmings. Infection of primary mammary fibroblasts with cytomegalovirus coordinately increases autotaxin-lysophosphatidate-inflammatory signaling, which could increase breast cancer metastasis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A035.