title: The Role of SOX2 and SOX9 as Regulatory Genes of the Head and Neck Squamous Cell Carcinoma Microenvironment
creator: Barbosa, Silvia
subject: 610
subject: 610 Medical sciences Medicine
description: Head and neck squamous cell carcinoma (HNSCC) is a highly heterogeneous disease with a rather diverse patient outcome. An epigenetic switch between SOX2 and SOX9 has been associated with modulation of cancer cells plasticity. Moreover, numerous studies support an association of altered expression for both transcription factors with the capacity to evade the immune surveillance, to develop treatment resistance and to promote metastasis. However, the molecular mechanisms involved in SOX2/SOX9 regulation and their clinical impact are still largely unknown. Main hypothesis of this study was that the stem cell-related transcription factors SOX2 and SOX9 modulate a gene-regulatory network and thereby influence the treatment response of cancer cells. The aims were to elucidate the role of the SOX2/SOX9 relationship and its heterogeneous expression in tumors, and how this potentially influences the tumor microenvironment including radiotherapy, which finally impacts patient response to therapy. SOX2 and SOX9 expression was investigated in established cancer cell lines, which showed a heterogenous expression pattern for both transcriptional factors. Immunohistochemical staining confirmed a heterogeneous and inverse SOX2/SOX9 expression pattern in most tumor tissues of patients from the Heidelberg Center for Personalized Oncology (HIPO) HNC cohort. Bioinformatics analysis of transcriptome data from The Cancer Genome Atlas for Head and Neck Squamous Cell Carcinoma (TCGA-HNSCC) unraveled candidate genes that might regulate or are the consequence of inverse SOX2/SOX9 expression. Ingenuity Pathway Analysis for selected candidate genes predicted TGF-ß signaling as one of the top canonical pathways related to inverse SOX2/SOX9 expression. The analysis of clinical data from TCGA-HNSCC confirmed that HPV-negative HNSCC with a high SOX2 and low SOX9 expression pattern exhibit an improved overall survival, when radiotherapy is part of the treatment. In line with the clinical data, SOX2 silencing in the OSCC cell line HNO223 reduced their survival capabilities after a single dose as well as fractionated dose of irradiation. A more detailed molecular characterization of established HNSCC cell lines revealed a trend toward reduced SOX2 expression but increased SOX9 protein levels for irradiated cancer cells as compared to controls. An increase of INHBA expression was also evident after irradiation supporting the predicted model of the bioinformatic analysis (positive association between TGF- signaling and a SOX2lowSOX9high phenotype). To investigate whether SOX2 modulates the susceptibility of cancer cells to immune cell attack after irradiation, co-culture assays were established with peripheral blood mononuclear cells that demonstrated the involvement of a more complex network in the regulation of immune effectors. To investigate the putative relation of SOX2/SOX9 expression in tumor cells with the tumor immune milieu in patient samples, single cells dissociated from primary tumors were investigated for marker expression of pan-leukocytes and Natural Killer cells. The analysis revealed an increased occurrence of immune cells in the tumor sample as compared to matched non-malignant adjacent tissue. Immunohistochemistry staining for SOX2 and SOX9 confirmed their heterogenous expression pattern also in those matched pathological samples. Further investigation on the relation between SOX2/SOX9 and the immune milieu for patient tumor material need be performed in order to correlate above findings with the treatment outcome. The recent findings shown that SOX2 and SOX9 predicted a signature gene set which can modulate radioresistance and the TGF-ß signaling is one of the top canonical pathways acting in the overexpression of candidate genes. These results pave the way for a further investigation where these transcription factors could be used as predictive outcome of head and neck squamous cell carcinoma patients.
date: 2024
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/33995/1/Barbosa_Silvia_Thesis_2022.pdf
identifier: DOI:10.11588/heidok.00033995
identifier: urn:nbn:de:bsz:16-heidok-339957
identifier:   Barbosa, Silvia  (2024) The Role of SOX2 and SOX9 as Regulatory Genes of the Head and Neck Squamous Cell Carcinoma Microenvironment.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/33995/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng