1. Esophageal squamous cell carcinoma and Activin/TGF signaling in tumor microenvironment

The overall research in our laboratory is to identify the role of Activin A signaling in esophageal epithelial cell invasion. With this project we address the question if Activin A and its receptors in the absence of functional TGFb receptor II mediate the activation of downstream targets such as SMAD2 resulting in epithelial-mesenchymal transition and increased cell invasion. We found that loss of E-cadherin and TGFb receptor II (TβRII) leads to the activation of fibroblasts adjacent to affected epithelial cells, and to the induction of epithelial cell invasion mediated through a fibroblast-secreted factor. Using three-dimensional organotypic cultures, we discovered that the upregulation of cathepsin B in invasive double mutant cells results in increased levels of active TGFb that activates fibroblasts, which in turn support the esophageal cell invasion (Neoplasia 2010, PLoS One 2011). We developed an innovative model that allows the analysis of epithelial-mesenchymal interactions and the microenvironment in a physiological context. We have published data showing an increase of Activin A in the absence of functional E-cadherin and TβRII and activation of Smad2 in vivo and in vitro (Lab Investigation 2014). Similar to classic TGFb, Activin A is described as having pro- and anti-tumorigenic function.

Characteristically, Activin A acts as a regulator of stem cell fate and differentiation during embryogenesis and a growth and proliferation inhibitor in differentiated cells. Similar to other members of the TGFβ superfamily, in the context of cancer, Activin A has been found to have both tumor promoting and inhibiting functions. Clinical studies have shown increased Activin A expression in oral squamous cell carcinomas, correlating with cancer progression and overall poor patient prognosis. Our current research aims to address the modulation of the tumor microenvironment in the context of Activin A signaling.

We currently aim to define the role of cancer cell-derived Activin A on cancer-associated fibroblasts and to determine the signaling changes and functional consequences upon Activin receptor loss.



  1. Esophageal inquiry through acid reflux disease (GERD) results in biomarker upregulation mediated by TGFb and ERK signaling pathways.

Esophageal adenocarcinoma is often considered to arise from a clonal stem-like population of cells, which is potentially responsible for its poor prognosis. TGFβ and Notch signaling pathways play important roles in regulating self-renewal of stem cells and cell-fate determination. Both pathways are frequently implicated in gastrointestinal carcinogenesis. However, their contributions to esophageal adenocarcinoma remain unclear. It is generally assumed that in esophageal metaplasia, the normal squamous esophageal epithelium undergoes transdifferentiation upon inquiry by acid reflux disease to resemble the columnar epithelium of the gastric tract and the intestine. BMP4, a member of the TGFβ family, has been shown to regulate the processes involved in this metaplastic transformation. Interestingly, in a series of resected adenocarcinomas of the distal esophagus TGF-beta1 mRNA was expressed at significantly higher levels in tumor tissues compared to squamous epithelium and Barrett’s mucosa. Activin A, has been shown to be upregulated in the progression from Barrett’s Esophagus to dysplasia and ultimately esophageal adenocarcinoma. Through our analysis of Activin A function in esophageal squamous cell carcinoma, we found that Activin effects are largely context- and dose-dependent. We therefore aimed to identify the role of Activin A in the progression to esophageal adenocarcinoma and we could show that Activin A signaling regulates cell invasion and proliferation in the progression to esophageal adenocarcinoma (Oncotarget 2015).

With current projects we are aiming to determine whether reflux inquiry through bile salt and acid induces Activin A, TGFb and ERK signaling as well as to define the regulation of stem cell markers in response to inquiry and in the progression from Barrett’s esophagus to esophageal adenocarcinoma.


  1. Oral squamous cell carcinoma and cancer initiating cell expansion following loss of E-cadherin and TGF signaling

Cancers of the oral cavity are among the 10 most common cancers in the US. It is estimated that 42,440 new oral squamous cell carcinoma (OSCC) cases are diagnosed in 2014. Current detection techniques often diagnose squamous cell carcinoma in late stages, requiring wide local resection and radiation therapy, from which patients suffer severe disfiguration. In addition, due to limitations in early diagnostics and treatment, the 5-year survival of OSCC has remained virtually unchanged over the last 30 years. Therefore, it is necessary to understand the molecular mechanisms underpinning OSCC development. Cancer stem cells or cancer initiating cells (CIC) are considered the driving cell type of the tumorigenic process. The importance of CICs is highlighted by their key role in therapy resistance and recurrence. A chief CIC feature is the acquisition of stemness through epithelial-mesenchymal transition (EMT). Transforming growth factor b b signaling is known to be a regulator of EMT and loss of E-cadherin is a major hallmark of the EMT process. We have shown that a subset of normal stem cell characteristics is maintained in CICs and upon loss of TGFb signaling and E-cadherin loss modified to promote key aspects of tumorigenesis. We have previously shown that coordinated loss of E-cadherin and TGFBR2 is a frequent event in squamous carcinogenesis and that E-cadherin is a prognostic factor in ESCC (Cancer Res 2006, Am J Pathol 2007).

We have developed a mouse model based on the hypothesis that expanding the population of cells with low or no E-cadherin expression and the reduced anti-proliferative effects of TGFb signaling will result in enhanced tumorigenesis. This model ensues in targeted loss of E-cadherin (Cdh1) and Tgfbr2 in the oral cavity, producing oral cancer. Advanced tumors in this system display regional lymph node invasion and distant pulmonary metastasis (Carcinogenesis 2014). About 20% of OSCC patients have cervical lymph node metastases at the time of diagnosis. The mouse tumors phenocopy the human disease on a pathologic and molecular level

In ongoing projects we address which aspects of normal stem cells are activated in CICs and how TGFb signaling impacts these pathways. AS smoking and alcohol consumption are the main risk factors for head-and-neck squamous cell carcinoma, we would like to determine whether these risk factors enhance CIC characteristics, e.g. expression of EMT and cancer stem cell markers and functional self-renewal and therapy resistance.


Identifying signaling components involved in the progression of head-and neck cancers has direct clinical relevance as it could result in new targeted or personalized combination therapies for oral squamous cell carcinoma.