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Abstract

PDA is one of the deadliest cancers with poor prognosis and profound therapy resistance, which is associated with the loss of gap junctional intercellular communication and Cx43 expression. A promising bioactive agent with multiple anti-cancer activities is sulforaphane, an isothiocyanate that is naturally found in cruciferous vegetables. Sulforaphane restored the gap junctional intercellular communication and thereby therapy sensitivity in PDA and I investigated whether microRNA signaling is involved in this mechanism. Established cell lines were evaluated in vitro by gap junction and gemcitabine bystander effect assays, microRNA and gene arrays, bioinformatics analysis and luciferase reporter assay, while in ovo xenograft studies with miRNA-transfected tumors were performed. miRNA and gene expression were also analyzed in patient tissue by in situ hybridization and immunohistochemistry. My results revealed that sulforaphane inhibited the expression of the top candidate miR30a-3p. Transfection with miR30a-3p inhibitors increased the gap junctional intercellular communication, Cx43 expression and gemcitabine bystander effect. In ovo, the xenotransplantation of these transfected cells decreased the tumor volume and enhanced the efficacy of gemcitabine. In a pancreatic cancer tissue array, the expression of miR30a-3p was present in malignant tissues but not in normal and the opposite result was observed for Cx43 expression. These findings provide new knowledge on the mechanism of sulforaphane-induced gap junctional intercellular communication and gemcitabine cytotoxicity in pancreatic cancer. With the aim to develop sulforaphane-based drugs for pancreatic cancer, I screened 7 unprecedented sulforaphane derivatives for their bioactivity against PDA and other tumor entities. MTT and colony forming assays, apoptosis analysis with flow cytometry, immunohistochemistry, microRNA studies as well as tumor xenograft and C. elegans studies were performed with these analogs. My observations suggest the anti-tumor activity of two out of the 7 derivatives, SF102 and SF134. SF102 was most effective in inhibition of viability, clonogenicity and tumor growth along with induction of apoptosis, followed by SF134, most importantly without obvious side effects. miRNA array profiling revealed differentially expressed candidates between sulforaphane derivatives and parental sulforaphane. My results indicate that sulforaphane-induced downregulation of the miR30a-3p enhances gap junctional intercellular communication and gemcitabine efficacy in pancreatic cancer. Sulforaphane derivatives SF102 and SF134 are shown to suppress the progression of pancreatic cancer. I expect that the development of new sulforaphane- or sulforaphane analogs-related drugs will forge new therapeutic options for pancreatic cancer.