Oral Microbiome Induced Tumor Stemness Pathway in Oral Cancer
Akeel, Ibrahim Saleh
MetadataShow full item record
CitationAkeel, Ibrahim Saleh. 2020. Oral Microbiome Induced Tumor Stemness Pathway in Oral Cancer. Doctoral dissertation, Harvard School of Dental Medicine.
AbstractBackground: The mechanisms of Oral squamous cell carcinoma (OSCC) development and progression are largely unknown. Various studies have identified self-renewing population of cancer cells, the cancer stem cells (CSCs) among the heterogeneous cell population of OSCC. These CSCs maintain stemness (self-renewal and undifferentiated state) by activating molecular pathways of stemness. Our lab’s previous work has characterized the hypoxia inducible factor 2 alpha (HIF-2α) tumor stemness pathway in lymphoma, as well as OSCC. The purpose of the study was to develop an in vitro assay platform that can identify oral bacteria having potential ability to modulate the tumor stemness pathways. We hypothesized that the oral microbiome of patients affected with OSCC activates the HIF-2α tumor stemness pathway. Innovation: The completion of the study may help to identify oral bacteria that may mediate tumor stemness pathway, and therefore facilitate in early diagnosis, as well as therapeutic monitoring of OSCC treatment. Materials and Methods: The SCC-25 cell line that contain ABCG2+ CSCs were treated with lipopolysaccharide (LPS) to define the toll-like receptor (TLR) mediated activation of tumor stemness switch. The assay for tumor stemness switch included the qPCR study of genes involved in the HIF-2α tumor stemness pathway, invasion/migration in a Boyden Chamber assay, self-sufficiency (the ability of the ABCG2+ cells to maintain stemness in the serum-free media), and niche-modulation (ability of the conditioned media of the ABCG2+ CSCs to reprogram cell components of tumor microenvironment such as mesenchymal stem cells and or immune cells). Next, the assays for the tumor stemness switch was repeated in SCC-25 cells treated with the processed saliva of OSCC patients. Finally, we attempted to recover live bacteria from the SCC-25 cells that exhibited tumor stemness switch following saliva treatment. Moreover, the identified bacteria was then tested for its direct ability to induce tumor stemness switch in SCC-25 cells. Results: SCC-25 cells tolerated the treatment of 5/22 saliva samples obtained from 22 OSCC patients. Out of these 5 saliva samples, 2 (patient #21 and 22) showed significant induction of genes involved in the tumor stemness switch. From the patient #21 saliva sample, we identified Fusobacterium nucleatum that internalized into ABCG2+ CSCs and modulated tumor stemness switch. Conclusion: The in vitro assay of tumor stemness switch using SCC-25 cell line has shown to be effective in identifying oral bacteria relevant in OSCC progression. Therefore, there is a great relevance of this assay to be used as a platform to study the role of oral microbiome induced tumor stemness switch, a cellular and molecular mechanism having clinical significance in OSCC diagnosis and management.
Citable link to this pagehttps://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37365590