Dual-functionality of RASSF1A overexpression in A375 cells is mediated by activation of IL-6/STAT3 regulatory loop

The RASSF1A, a microtubule associated protein, is a well-known tumor suppressor silenced in various cancer via promoter hypermethylation. RASSF1A is implicated in the regulation of cellular proliferation and apoptosis. However, its role in melanoma A375 cells invasion and metastasis remain unclear. Here, we report an unusual dual function role of ectopic RASSF1A in A375 cells. RASSF1A suppressed A375 cells proliferation but enhanced cells migration, invasiveness and metastatic potential in vivo. We demonstrated RASSF1A simultaneously up-regulated p21 and vimentin expression in A375 cells. Increase of vimentin expression contributes to RASSF1A mediated enhancement of cells mobility and invasion. Transcriptome assay unclosed that RASSF1A promoted IL-6 expression in A375 cells, which in turn activate JAK2/STAT3 signaling. Treatment with recombinant IL-6 enhanced both p21 and vimentin protein level in the empty vector transfected A375 cells to similar level as RASSF1A expressing cells. In contrast, knockdown IL-6 expression by siRNAs decreased p21 and vimentin level in RASSF1A expressing cells. Blockade of JAK2/STAT3 signaling by use of JAK2 inhibitor WP1066 led to decrease of IL-6, p21 and vimentin protein in RASSF1A expressing cells. Our findings unclosed a unusual dual functionality of ectopic RASSF1A overexpression in A375 cells by regulating IL-6/STAT3 regulatory loop, suggesting it should be cautious about the safety of RASSF1A-based gene therapy.