The process of epithelial–mesenchymal transition (EMT) is crucial in various physiological/pathological circumstances such as development, wound healing, stem cell behavior, and cancer progression. It involves the conversion of epithelial cells into a mesenchymal phenotype, which causes the cells to become highly motile. This reprogramming is initiated and controlled by various signaling pathways and governed by several key transcription factors, including Snail 1, Snail 2 (Slug), TWIST 1, TWIST2, ZEB1, ZEB2, PRRX1, GOOSECOID, E47, FOXC2, SOX4, SOX9, HAND1, and HAND2. The intracellular signaling pathways are activated/inactivated by signals received from the extracellular environment and the transcription factors are carefully regulated at the transcriptional, translational, and post-translational levels to maintain tight regulatory control of EMT. One of the most important pathways involved in this process is the transforming growth factor-β (TGFβ) family signaling pathway. This review will discuss the role of EMT in promoting epithelial cancer progression and the convergence/interplay of multiple signaling pathways and transcription factors that regulate this phenomenon.

Background: Prostate cancer progression to androgen independence is the primary cause of mortality by this tumor type. The IGF-1/IGF-1R axis is well known to contribute to prostate cancer initiation, but its contribution to invasiveness and the downstream signalling mechanisms that are involved are unclear at present. Results: We examined the invasive response of androgen independent DU145 prostate carcinoma cells to IGF-1 stimulation using Matrigel assays. We then examined the signaling mechanisms and protease activities that are associated with this response. IGF-1 significantly increased the invasive capacity of DU145 cells in vitro, and this increase was inhibited by blocking IGF-1R. We further demonstrated that specific inhibitors of the MAPK and PI3-K pathways decrease IGF-1-mediated invasion. To determine potential molecular mechanisms for this change in invasive capacity, we examined changes in expression and activity of matrix metalloproteinases. We observed that IGF-1 increases the enzymatic activity of MMP-2 and MMP-9 in DU145 cells. These changes in activity are due to differences in expression in the case of MMP-9 but not in the case of MMP-2. This observation is corroborated by the fact that correlated changes of expression in a regulator of MMP-2, TIMP-2, were also seen. Conclusion: This work identifies a specific effect of IGF-1 on the invasive capacity of DU145 prostate cancer cells, and furthermore delineates mechanisms that contribute to this effect.