15-Deoxy-Δ<sup>12,14</sup>-prostaglandin J<sub>2</sub> Induces Epithelial-tomesenchymal Transition in Human Breast Cancer Cells and Promotes Fibroblast Activation
Jeehye Choi, Jinyoung Suh, Do‐Hee Kim, Hye‐Kyung Na, Young‐Joon Surh
Abstract
In inflammation-associated carcinogenesis, COX-2 is markedly overexpressed, resulting in accumulation of various prostaglandins. 15-deoxy- 12,14 -prostaglandin J 2 (15d-PGJ 2 ) is one of the terminal products of COX-2-catalyzed arachidonic acid catabolism with oncogenic potential. Epithelial-to-mesenchymal transition (EMT) is a process by which epithelial cells lose their polarity and adhesiveness, and thereby gain migratory and invasive properties. Treatment of human breast cancer MCF-7 cells with 15d-PGJ 2 induced EMT as evidenced by increased expression of Snail and ZEB1, with concurrent down-regulation of E-cadherin. Nuclear extract from 15d-PGJ 2 -treated MCF-7 cells showed the binding of Snail and ZEB1 to E-box sequences present in the E-cadherin promoter, which accounts for repression of E-catherin expression. Unlike 15d-PGJ 2 , its non-electrophilic analogue 9,10-dihydro-15d-PGJ 2 failed to induce EMT, suggesting that the ,b-unsaturated carbonyl group located in the cyclopentenone ring of 15d-PGJ 2 is essential for its oncogenic function. Notably, the mRNA level of interleukin-8 (IL-8)/CXCL8 was highly elevated in 15d-PGJ 2 -stimulated MCF-7 cells. 15d-PGJ 2 -induced up-regulation of IL-8/CXCL8 expression was abrogated by silencing of Snail short interfering RNA. Treatment of normal fibroblast with conditioned medium obtained from cultures of MCF-7 cells undergoing EMT induced the expression of activated fibroblast marker proteins, -smooth muscle actin and fibroblasts activation protein-. Co-culture of normal fibroblasts with 15d-PGJ 2 -stimulated MCF-7 cells also activated normal fibroblast cells to cancer associated fibroblasts. Taken together, above findings suggest that 15d-PGJ 2 induces EMT through up-regulation of Snail expression and subsequent production of CXCL8 as a putative activator of fibroblasts, which may contribute to tumor-stroma interaction in inflammatory breast cancer microenvironment.