Abstract 5547: Exploration of selective small molecule compounds as caspase inhibitors for treatment of oral mucositis caused by cancer therapy.
Authors: Wu Jianghong , Qian Jie , Lu Lihui , Ma Haiching 
Published: August 2014

Oral mucositis is major and painful side effect, and often a dose limiting factor in head and neck cancer therapy. Our objective is to develop small molecule caspase inhibitors to inhibit apoptosis for cytoprotection of normal cells from harmful side effects of cancer therapy. We previously used the Bionet 37,500 compound library and successfully completed High Throughput Screening (HTS) against caspase-1, 3, and 9 and got 43 hit compounds using the fluorogenic substrates DEVD-AMC and LEHD-AMC. In this study, the 43 hit compounds were screened for cytoprotection activity against staurosporine-induced cell death in NIH3T3 cells by Cell Tito-glo cell viability assay. 19 compounds were found to have significant protective effects. We also confirmed that compound #23 and #27 selected from the above 19 compounds protect NIH3T3 cells from staurosporine-induced caspase activation using cell-based Apo-one Caspase-3/7 activity assay. To explore the molecular mechanisms of the protective effect, a comprehensive phospho and signaling proteomic based study was performed using Phospho Explorer (containing 1328 antibodies) and Signaling Explorer (containing 1358 antibodies) antibody microarray. The results showed that compound#23 or #27 alone treatment induces increase of phosphorylation levels of a spectrum of proteins involved in cell survival signaling including Lyn, LIMK1, IKK-γ, IkB-α, p38 MAPK, NFkB-p65, EGFR and AKT1S. When we compare compound #23 or #27 plus staurosporine group with staurosporine alone group, we discover elevation of phosphorylation of some signaling proteins (c-met, FGFR1, NFAT4, MEK-2 and NFkB-p65) that are linked to cell proliferation and differentiation. In comparison to staurosporine alone treatment, co-treatment of compound #23 or #27 with staurosporine up-regulated the expression levels of some cellular signaling protein targets: HSP90A, RAB40B, FGF22, and CLIP. In addition, our DNA microarray analysis using Affymetrix GeneChip Mouse Gene 1.0ST which covers 26, 166 coding transcripts showed significant expression alterations of many apoptosis and signaling related genes such as Htra2 (Omi), Diablo (Smac), caspase-12 and Tuba1b in staurosporine and compound #23 or #27 plus staurosporine treated samples. Furthermore, compounds # 23 and #27 were also shown to protect human oral keratinocytes (HOK) cells from radiation insult using radiation colony formation assay. Currently, Cal27 and Fadu head and neck cancer cell lines and human normal HOK and HPLF cells are being tested in parallel in terms of cell viability, and apoptosis with anticancer drug Doxorubicin and Etoposide treatments with or without caspase inhibitors. Our study may lead to the discovery of applicable therapeutic drugs to combat oral mucositis caused by radiotherapy, chemotherapy, or combined chemo/radiotherapy.

Citation Format: Jianghong Wu, Jie Qian, Lihui Lu, Haiching Ma. Exploration of selective small molecule compounds as caspase inhibitors for treatment of oral mucositis caused by cancer therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5547. doi:10.1158/1538-7445.AM2013-5547