Promotion agents with a structure-activity relationship (SAR) that points to some mechanism(s) other than NT inhibition. For example, among novel tetrahydroisoquinoline riboside NT inhibitors tested as anti-tumor promotion agents in the JB6 P+ carcinogenesis model, the relative order of potency with regard to anti-promotion activity was: Compound 23 >Compound 3 >Compound 4, whereas the NT inhibitory potency order was the opposite, with Compound 4 being the most potent (Ki = 0.45 nM) followed by Compound 3 (Ki = 15 nM) and then followed by Compound 23, the least potent (Ki = 300 nM). Upon further investigation with Compound 23, we have shown that in addition to inhibiting TPA-induced tumorigenic transformation, it also inhibits TPA-induced AP-1 transcription factor activation, which has been shown to have a major role in TPA-induced tumor promotion in the JB6 mouse epidermal cell carcinogenesis model, as well as in many other in vitro and in vivo carcinogenesis processes. Thus, in this application, we propose to initiate an investigation of the mechanisms of action of compound 23, as well as conduct antitumor promotion SAR and test the compounds'cancer chemopreventive potential in an in vivo mouse skin carcinogenesis model.
The specific aims are: 1) to synthesize and test new aromatic and heterocyclic analogs of Compound 23, 2) to investigate interference with AP-1 DNA binding, and MAP kinase signaling pathways that might account for the possible AP-1-dependent antitumor promotion activity of the compounds, and 3) to evaluate the best compound from Aim 2 in an in vivo mouse skin carcinogenesis model. AP-1-SEAP JB6 reporter cells created by us will be used for the in vitro investigations of SAR and mechanism. We will use the AP-1-SEAP reporter and anchorage independent cell growth clonogenic transformation assays to test the potential chemopreventive activity of new compounds to be synthesized activity. Interference with AP-1 DNA binding, protein kinase C, as well as the role of the mitogen-activated protein kinases (MAPKs) ERK, p38 and JNK, known to be upstream of AP-1, will be analyzed. The SENCAR mouse skin two-stage carcinogenesis model will be used to assess the in vivo anti-tumor promotion activity of this class of compounds in attempts to identify potential lead compounds for preclinical optimization. The success of this research program may lead to the identification of novel promising agents for skin cancer chemoprevention.
