Colorectal cancer is one of the leading causes of death in most developed countries including the United States. Colon cancer chemotherapy relies on a number of cytotoxic drugs, targeted agents and their combinations, and there is an increasing need to develop alternative drugs targeting specific pathways that inhibit tumor growth, progression and metastasis and induce apoptosis. Specificity proteins (Sps) are transcription factors overexpressed in many tumors, and Sps regulate expression of genes required for cancer cell and tumor growth (p27 suppression), survival (survivin), and angiogenesis (VEGF, VEGFR1 and VEGFR2). Studies in this laboratory have now shown that tolfenamic acid (TA) and betulinic acid (BA) and a novel synthetic triterpenoid acid (ester), namely methyl-2-cyano-3,11-dioxo-18?-olean-1,12-dien-30-oate (CDODA-Me) induce G2/M growth arrest and proteasome-independent degradation of Sp proteins in colon cancer cells. These effects are directly linked to compound-induced modulation of expression of oncogenic microRNA-27a (mir-27a) and other miRs. Therefore, we hypothesize that TA, BA and CDODA-Me represent a unique class of anticancer agents that target miR-27a and other miRs. The proposed studies will characterize the mechanisms of action and effects resulting from drug-miR interactions in colon cancer.
Aim 1 will focus on TA-/BA-/CDODA-Me-miR-27a interactions and investigate the activation of miR-27a-dependent ZBTB10 and Myt-1 expression and their subsequent downstream modulation of Sp and Sp-dependent genes, growth inhibitory, antiangiogenic and proapoptotic responses in colon cancer cells. TA, BA and CDODA-Me also decrease expression of other miRs in colon cancer cells, and these include miR-23a and miR-24-2 which form a cluster with miR-27a.
Aim 2 will investigate TA-, BA- and CDODA-Me-miR(23a~24-2) interactions and determine their role in mediating the anticarcinogenic activities of these compounds.
Aim 3 will investigate the in vivo anticarcinogenic activity of TA, BA and CDODA-Me in a mouse xenograft and "Min" model for colon cancer and determine the compound-miR interactions. In addition, mice overexpressing miR-27a have been developed as probes for investigating the role of this oncogenic miR in colon carcinogenesis. These studies will provide critical data on the efficacy and mechanisms of action of TA, BA and CDODA-Me as a novel class of anticancer drugs that act through multiple pathways including direct effects on microRNAs and their associated gene transcripts.
Recent studies in this laboratory have identified two structural classes of compounds that induce Sp protein repression in cancers and inhibit cancer cell growth and survival. These compounds include the triterpenoids betulinic acid (BA) and methyl 2-cyano-3,11-dioxo-18?-olean-1,12-dien-30-oate (CDODA-Me) and the NSAID tolfenamic acid (TA). The studies proposed in this project will focus on the mechanisms of action of these anticancer agents with emphasis on their effects on the oncogenic microRNA-27a (miR-27a) and other miRs and the role in repression of Sp proteins and other critical genes.
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