Different modulatory effect of the synthetic cannabinoid WIN55,212-2 on tumor cell migration.

MicroRNAs are small non-coding regulatory molecules exerting pleiotropic action in different biological processes such as proliferation, differentiation, apoptosis, migration and metastasis. Deregulation of miRNA expression has been observed in various cancers, and accumulating data suggest that miRNAs can display an oncogenic, antioncogenic or an ambiguous behavior in relationship to tumor environment. In a previous research we showed that the synthetic cannabinoid WIN55,212-2 is able to reduce the migratory activity of osteosarcoma MG63 cells analyzed by means of wound healing assay. So we undertook a study to evaluate the biochemical mechanism through which WIN plays this action. To this purpose we evaluated the levels of miR-29b1, a member of miR-29 family which has been shown to impact critical steps in the migratory and metastatic cascade, such as EMT, apoptosis and angiogenesis. RT-PCR experiments showed that in MG63 cells 5 M WIN increased the level of miR-29b1 of about 700-fold. This effect was accompanied by the reduction in its putative targets MMP-2, PDGF-B and N-MYC, thus indicating that the miRNA is functionally active. Moreover, cells stably overexpressing miR-29b1 did not close the wound after 48 h, mimicking the effect of WIN in untransfected control cells. Notably, ERα(+) MCF-7 and triple negative MDA-MB-231 cells, two different breast cancer models, treated with the cannabinoid migrated into the scratched area significantly faster than the respective control cells. In these cells WIN also increased the level of miR-29b1 targets. Therefore, differently from osteosarcoma cells, these preliminary observations seem to indicate that WIN promotes migration ability in breast cancer cells. The reasons for this diverse behaviour could rely on miR-29b1, whose expression can change in different cell types or show temporal differences dictated by cell physiology and tumor microenvironment impact. Studies are in progress to shed light on the molecular mechanisms underlying this different response.