e13549 Background: Inhibition of nuclear export can promote re-activation of tumor suppressor pathways. CRM1 (chromosomal regional maintenance 1) or XPO1 (exportin 1) is the major protein that mediates nuclear export. We hypothesized that CRM1 mediated nuclear export represents a novel therapeutic target that can be manipulated to inhibit melanoma cell survival. Methods: The growth inhibitory and pro-apoptotic effects of KPT-185, KPT-276 and KPT-330, small molecules selective inhibitor of nuclear export (SINE) were evaluated in human melanoma cell lines using an MTT assay and Annexin V/PI staining, respectively. Fluorescence microscopy and immunoblots were used to assess nuclear accumulation of tumor suppressor proteins. The trans-isomer of KPT-185 and DMSO (vehicle) were used as a negative controls in all assays. The pharmacokinetic (PK) profile of all compounds was evaluated in mice. Results: CRM1 protein was highly expressed in human melanoma cell lines with diverse molecular profiles (i.e., B-Raf, NRAS, p53). KPT-SINE inhibited melanoma cell growth in a concentration-dependent manner and induced apoptosis at nanomolar concentrations. Importantly, there was no evidence that B-Raf V600 mutational status influenced melanoma cell response to these agents. Nuclear accumulation and/or induction of p53, p21, FOXO3a, STAT1 and BAD, and reduction of MCL-1 occurred in melanoma cells at time points prior to apoptosis as shown by increase in cleaved PARP and caspase 3 levels. PK studies were conducted in mice following oral administration of 10 mg/kg, to guide drug selection for our ongoing efficacy studies in murine melanoma models. KPT-185 showed limited bioavailability and systemic exposure, while KPT-276 and KPT-330 showed >50% bioavailability reaching Cmax >5µM. Conclusions: This study represents the first report of CRM1 inhibition in melanoma. These data indicate that the novel SINE compounds can effectively inhibit CRM1-mediated nuclear export and induce apoptosis in melanoma cells. KPT-330 is currently under development as orally bioavailable, small molecule inhibitors for a human clinical trial.
MT1-MMP dependent repression of the tumor suppressor SPRY4 contributes to MT1-MMP driven melanoma cell motility