As a point of convergence for numerous oncogenic signaling pathways, signal transducer and activator of transcription 3 (STAT3) is central in regulating the anti-tumor immune response. STAT3 is broadly hyperactivated both in cancer and non-cancerous cells within the tumor ecosystem and plays important roles in inhibiting the expression of crucial immune activation regulators and promoting the production of immunosuppressive factors[1]. STAT3 is widely expressed and located in the cytoplasm in an inactive form. STAT3 is rapidly and transiently activated by tyrosine phosphorylation by a range of signalling pathways, including cytokines from the IL-6 family and growth factors, such as EGF and PDGF. STAT3 activation and subsequent dimer formation initiates nuclear translocation of STAT3 for the regulation of target gene transcription[2].Tetramethylcurcumin (FLLL31), derived from curcumin, specifically suppresses the phosphorylation of STAT3 by binding selectively to Janus kinase 2 and the STAT3 Src homology-2 domain. Tetramethylcurcumin exhibits anti-inflammatory and anti-cancer effects[3]. Tetramethylcurcumin (FLLL31; 2.5 and 5 µM; for 24 hours) downregulats STAT3 phosphorylation and DNA-binding activity in MDA-MB-231 breast and PANC-1 pancreatic cancer cells. Tetramethylcurcumin inhibits cell viability, cell invasion. Tetramethylcurcumin is a effective inhibitor of STAT3 phosphorylation, DNA-binding activity, and transactivation in vitro, leading to the impediment of multiple oncogenic processes and the induction of apoptosis in pancreatic and breast cancer cell lines[3].
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