The therapeutic potential of ML induced MET

The therapeutic potential of ML327-induced MET against Piericidin A of mesenchymal origin has not been explored. In the present study, we hypothesized that induction of MET using ML327 would block the growth of ES cells and sensitize to TRAIL-mediated apoptosis. Herein, we report that ML327 induces apoptosis in ES cells and has additive pro-apoptotic effects when used in combination with TRAIL in vitro. These findings provide a rationale to investigate the in vivo effects of small molecule-mediated MET agents, such as ML327, in the treatment of sarcomas, both alone and in combination with TRAIL-based therapeutic strategies.
Materials and methods
Results
Discussion Therapeutic resistance is a consistent feature of tumors arising from cells of mesenchymal origin and carcinomas that have undergone EMT in their disease progression [14]. We originally identified ML327 as a small molecule that is capable of inducing the expression of E-cadherin, a hallmark of epithelial cell fate, in advanced carcinoma cells of the lung and colon [10]. We have systemically expanded our observations to encompass tumors of neural crest origin, neuroblastoma, and now cells of mesenchymal origin (ES) [11]. E-cadherin is consistently upregulated by ML327 in all tested cell lines (colon, lung, breast, neuroblastoma, and ES cells) with the exception of RKO (colon) and MDA-MB-231 (breast) cancer cells, whose E-cadherin promoters are silenced by DNA hypermethylation [10], [18]. Intriguingly, the predominant cellular response observed within colon and lung carcinomas is blockade of cellular migration with no observed changes in cellular viability appreciated in vitro and in vivo[10]. The predominant feature of our trials in neuroblastoma is growth arrest and necrosis with minimal induction of apoptotic markers [11]. Herein, we report a marked induction of apoptotic markers, Caspase 3 and PARP cleavage, in association with MET induction in ES cells. Overall, these findings suggest an enhanced sensitivity of non-epithelial derived tumors, such as ES cells, to ML327. Incremental progress has been made in improving the outcomes of children afflicted with ES, prompting considerable investigation into the potential use of death-inducing ligands, such as TRAIL [4], [12], [19]. Of these agents, TRAIL has received much attention given its lack of toxicity to non-transformed cells, highlighting a potential therapeutic window for exploitation [14]. Rapid clearance and resistance have plagued early clinical trials using TRAIL, highlighting the need to identify novel small molecules that sensitize to TRAIL-based therapeutics [14], [20]. Reversal of mesenchymal or migratory features has been identified as one potential strategy for TRAIL sensitization [14]. Specifically, the HDAC inhibitor, MS-275, has been shown to both reverse EMT, attenuate metastasis, and sensitize breast cancer cells to TRAIL [21]. Our findings support these observations, as ML327 induces epithelial-like features and sensitizes ES cells to TRAIL-mediated apoptosis. We have previously reported the capacity of ML327 to mediate TRAIL sensitization in colon cancer cells, demonstrating this process to be in part mediated by down regulation of cFLIPs [18]. Our results are in support of our previous investigation, as we observe consistent downregulation of cFLIPs in association with ML327-mediated TRAIL sensitization. Further investigation into the therapeutic potential of the EMT reversal/MET induction agents, such as ML327, in combination with TRAIL-based strategies merits further investigation featuring studies to determine in vivo efficacy. In conclusion, we have validated the capacity of ML327 to elicit features of MET in ES cells. In contrast to prior characterizations in carcinoma and neural crest-derived tumors, ML327 elicits striking induction of apoptosis in all tested ES cell lines. Furthermore, partial MET induction in ES cells using ML327 sensitized ES cells to TRAIL-mediated apoptosis. Together, these findings support further in vivo characterization of ML327 in mesenchymal cancers, such as ES, both alone and in combination with TRAIL-based therapeutic strategies.