Abstract: Approximately 53,000 people in the United States are diagnosed with oral cancer yearly, and the 5-
year survival rate remains poor due to late diagnosis and intervention. Recent evidence has suggested
periodontal disease as a potential risk factor, and it is also associated with poor outcomes. Interestingly,
periodontal disease and oral cancer share common phenomenon: disruption of epithelial barrier integrity and
inflammation. More specifically, the periodontal pathogen Fusobacterium nucleatum has been associated with
both barrier disruption and with oral cancer. Still, it is unclear whether disruption of the oral epithelial barrier by
Fusobacterium nucleatum is a mechanistic promoter of pro-tumorigenic oral transformation, or just a
consequence of it. To answer this question, we interrogate here a cellular complex that is essential for epithelial
barrier integrity, called the adherens junction. More specifically, we have found that the adherens junction
component PLEKHA7, which is an E-cadherin and p120 binding partner, recruits core components of the RNA
interference machinery including the microprocessor, the RNA induced silencing complex, and sets of mRNAs
and miRNAs to maintain epithelial homeostasis. PLEKHA7 depletion from cultured epithelial cells results in mis-
localization of the RNAi machinery, decreased miRNA silencing activity, increased oncogene expression, and
pro-tumorigenic cell transformation. However, such disruption of the RNAi interference machinery, particularly
associated with barrier integrity, has not been studied to date in oral cancer, exposing a significant gap in
knowledge. We hypothesize that PLEKHA7 recruits and regulates the RNAi machinery at oral epithelial adherens
junctions to maintain homeostasis, and that this mechanism is disrupted in the presence of oral pathogens, which
in turn promote expression of pro-tumorigenic and inflammatory markers. We will test our hypothesis through
two Specific Aims: 1) determine whether oral epithelial adherens junctions recruit the RNAi machinery to regulate
function and levels of miRNAs and of their target mRNAs, using two dimensional and three-dimensional epithelial
cell models and by examining tissues from patients; 2) determine if the oral periodontal pathogen Fusobacterium
nucleatum promotes upregulation of oncogenic and pro-inflammatory markers through miRNA dysregulation,
using co-cultures with Fusobacterium nucleatum, immunofluorescence, protein, and RNA analyses. This project
is significant, since it will identify a novel molecular mechanism of epithelial pro-tumorigenic transformation in
the oral mucosa, advancing our understanding of the disease. The study is innovative, as it links pathogens, oral
epithelial barrier function, and localized RNAi and miRNA regulation with oral cancer. We anticipate that the
study will be impactful and contribute to future development of effective biomarkers oral cancer, which are
critically needed for timely and successful intervention, as well as to the potential development of RNA-based
therapeutics. Altogether, this fellowship will provide foundational training in oral epithelial biology to foster the
development of the DMD/PhD trainee into a unique and critically needed academic dental scientist.
