Patients with colorectal cancer (CRC) have been shown to have elevated levels of circulating prostaglandin E2 (PGE2) which promotes cancer progression and suppresses T cell immune responses. In this study we evaluated whether signaling responses in T lymphocytes obtained from peripheral blood of CRC patients were affected by the sustained exposure to increased levels of PGE2. The phosphorylation status of an extended panel of proteins involved in downstream signaling cascades in T cells was profiled at a single cell level both in naïve and antigen-experienced cells after triggering T cell-, prostaglandin- and interleukin-2 receptors. Peripheral T cells from patients with elevated PGE2 levels displayed aberrant T cell signaling responses downstream of the T cell receptor (assessed by reduced phosphorylation of CD3ζ and SLP76), and after triggering the IL-2 receptor (assessed by reduced phosphorylation of STAT5) when compared to T cells from CRC patients with lower levels of PGE2 and T cells from healthy blood donors. This signaling study of circulating T cells from CRC patients indicates that increased systemic PGE2 levels affect proximal T cell responses and confirms phospho-specific flow cytometry to be a valuable tool for revealing signaling signatures in immunological disorders.
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