Oral squamous cell carcinoma (OSCC), which is the most common malignancy of the oral cavity, is often associated with local and regional invasion. Increased expression of matrix metalloproteinase-9 (MMP-9) is correlated with invasive behavior of OSCC. Because transforming growth factor B1 (TGF-B1) is up-regulated in OSCC tumors, we examined the relationship between TGF-B1 signaling and MMP-9 in human OSCC specimens. Evaluation of human specimens showed that tumors with enhanced TGF-B1 signaling also showed increased MMP-9 expression.

Members of Snail family of transcription factors play an important role in oral cancer progression by inducing epithelial-mesenchymal transition, by promoting invasion and by increasing matrix metalloproteinase (MMP) expression. Although Snail (Snai1) is the best characterized and the most extensively studied member of this family, the role and regulation of Slug (Snai2) in oral cancer progression is less well understood. In this report, we show that transforming growth factor-beta1 (TGF-beta1) increases Slug levels in tert-immortalized oral keratinocytes and in malignant oral squamous cell carcinoma (OSCC) cells. Inhibiting ERK1/2 signaling, but not PI3-kinase signaling, blocked TGF-beta1-induced Slug expression in the malignant UMSCC1 cells. To further examine the role of Slug in OSCC progression, we generated UMSCC1 cells with inducible expression of Slug protein. Induction of Slug in UMSCC1 cells did not repress E-cadherin levels or regulate individual movement of UMSCC1 cells. Instead, Slug enhanced cohort migration and Matrigel invasion by UMSCC1 cells. Slug increased MMP-9 levels and MMP-9-specific siRNA blocked Slug-induced Matrigel invasion. Interestingly, Slug-specific siRNA attenuated TGF-beta1-induced MMP-9 expression and Matrigel invasion. These data demonstrate that TGF-beta1 increases Slug via ERK1/2 signaling, and thereby contributes to OSCC progression.

promoter activity exclusively in oral keratinocytes but not in OSCC cells. The effect of EGF on TGFβ1-mediated Smad-driven promoter activity and N-cadherin expression was reversed when activation of ERK1/2 was blocked. Although EGF and TGFβ1 independently promoted migration of both oral keratinocytes and OSCC cells, EGF decreased TGFβ1-mediated migration of oral keratinocytes but enhanced migration of OSCC cells. Together, these data support a model wherein EGF signaling has an important negative regulatory role on TGFβ1-mediated N-cadherin expression and motility in normal oral keratinocytes, and in which loss of this regulatory mechanism accompanies malignant transformation of the oral epithelium.

Ca2+ messages are broadly important in cellular signal transduction. In immune cells, Ca2+ signaling is an essential step in many forms of activation. Neutrophil-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) is one form of leukocyte activation that plays an important role in tumor cell killing in vitro and in patient care. Using fluorescence methodologies, we found that neutrophils exhibit Ca2+ signals during ADCC directed against breast fibrosarcoma cells. Importantly, these signals were localized to Ca2+ microdomains at the neutrophil-to-tumor cell interface where they display dynamic features such as movement, fusion and fission. These signals were blocked by the intracellular Ca2+ buffer BAPTA. At the neutrophil-tumor cell synapse, the neutrophil’s cytoplasm was enriched in STIM1, a crucial mediator of Ca2+ signaling, whereas the Ca2+ binding proteins calbindin and parvalbumin were not affected. Our findings suggest that Ca2+ microdomains are due to an active signaling process. As Ca2+ signals within neutrophils were necessary for specific tumor cell apoptosis, a central role of microdomains in leukocyte-mediated tumor cell destruction is indicated.