Cancer Cell-Type-Dependent Modifications of Metastatic Parameters by SLIT2-ROBO1 and RHOA cAMP Signaling in Response to TGFβ1 and FGF2.

The epithelial to mesenchymal transition (EMT) is a multistep process involving structural and functional alterations that are required for cancer metastasis, as well as loss of epithelial markers (e.g., E-cadherin/CDH1) and gain of mesenchymal markers (e.g., N-cadherin/CDH2, vimentin/VIM). Pathological events modify cell-cell interactions, cell-matrix adhesion and extra cellular matrix integrity leading to cell migration, evasion from the primary tumor and augmented invasiveness in the metastatic niche. This transformation is modulated by multiple paracrine factors (e.g., chemokines, growth factor), as well as SLIT2-ROBO1 signaling that collectively regulate expression of RHO GTPases (e.g., RHOA) and EMT marker genes. Yet, the roles of SLIT proteins in cancer remain enigmatic. In some cancer types, SLIT2 is anti-tumorigenic, while in other cancers it contributes towards the metastatic phenotype. Here we investigated the ambivalent metastatic activity of SLIT2 by analyzing how cAMP/RHOA signal transduction modulates SLIT-ROBO controlled metastatic parameters in response to the phosphodiesterase inhibitor IBMX (3-isobutyl-1-methylxanthine) and paracrine factors (TGF-β/TGFβ1 and FGF2). Upon SLIT2 administration cell migration and proliferation increases in colon cancer cells and decreases in cervical cancer cells, while altering cell morphology and proliferation in both cancer types. These effects are reinforced by TGF-β/TGFβ1 and FGF2, but attenuated by elevation of cAMP with IBMX, depending on the cancer cell type. Our data indicate that SLIT2 represents a potential biomarker for cancer diagnosis, prognosis, and therapy.