Signal transducer and activator of transcription 3 (STAT3), a member of the STAT protein family, can be phosphorylated by receptor-associated Janus kinases (JAKs) in response to stimulation by cytokines and growth factors. It forms homo- or heterodimers that can translocate to the cell nucleus where they act as transcription activators. Constitutive activation of STAT3 has been found to be associated with initiation and progression of various cancers. It can exert proliferative as well as anti-apoptotic effects. This review focuses on the role of STAT3 in pathogenesis i.e., proliferation, differentiation, migration, and apoptosis of hematological malignancies viz. leukemia, lymphoma and myeloma, and briefly highlights the potential therapeutic approaches developed against STAT3 activation pathway.

STAT3 is an oncogenic transcription factor that controls the expression of genes associated with oncogenesis and malignant progression. Persistent activation of STAT3 is observed in human malignancies, including hepatocellular carcinoma (HCC) and multiple myeloma (MM). Here, we have investigated the action of Tris(dibenzylideneacetone) dipalladium 0 (Tris DBA) on STAT3 signaling in HCC and MM cells. Tris DBA decreased cell viability, increased apoptosis, and inhibited IL-6 induced/constitutive activation of STAT3, JAK1, JAK2, and Src in HCC and MM cells. Tris DBA downmodulated the nuclear translocation of STAT3 and reduced its DNA binding ability. It upregulated the expression of SHP2 (protein and mRNA) to induce STAT3 dephosphorylation, and the inhibition of SHP2 reversed this effect. Tris DBA downregulated the expression of STAT3-driven genes, suppressed cell migration/invasion. Tris DBA significantly inhibited tumor growth in xenograft MM and orthotopic HCC preclinical mice models with a reduction in the expression of various prosurvival biomarkers in MM tumor tissues without displaying significant toxicity. Overall, Tris DBA functions as a good inhibitor of STAT3 signaling in preclinical HCC and MM models.

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Cancer is complex disease involving complex genetic and epigenetic heterogeneity making it the second leading cause of death globally after heart disease. While conventional treatments like surgery, radiotherapy, chemotherapy are principal strategies, the focus is shifting to therapies that can target multiple pathways to treat cancers. In the present report, we hypothesized that Tris DBA, an organometallic compound, can inhibit proliferation, tumor growth, and induce apoptosis in multiple myeloma (MM) and hepatocellular carcinoma (HCC) cells, thereby potentially exhibiting significant anticancer effects. Our preliminary results clearly indicated that Tris DBA could substantially inhibit both constitutive as well as IL-6 inducible STAT3 activation and abrogate proliferation/survival in MM and HCC cells. A phospho-proteomic profiling revealed several key phosphorylation changes induced by Tris DBA treatment which further indicate broad anticancer potential of the compound. Additionally, the agent exhibited potent antitumor actvitiy in vivo, with little adverse effects. The ongoing work is aimed at investigating the possible binding target(s) of Tris DBA and further characterize the molecular mechanism(s) underlying STAT3 inhibitory effects of the drug. Citation Format: Loukik Arora, Chris Soon Heng Tan, Radoslaw M. Sobota, Gautam Sethi. Identification of molecular targets of Tris DBA [Tris(dibenzylideneacetone)dipalladium(0)] for cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1240.