University of Illinois Urbana-Champaign

Toward an epigenetic classification of human testicular germ cell tumors (TGCTs): preliminary assessment of histone H3-K27 trimethylation according to TGCT subtype, aggressiveness, and response to therapy

Parker, Maryanna H.

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Description

Title
Toward an epigenetic classification of human testicular germ cell tumors (TGCTs): preliminary assessment of histone H3-K27 trimethylation according to TGCT subtype, aggressiveness, and response to therapy
Author(s)
Parker, Maryanna H.
Issue Date
2024-04-30
Director of Research (if dissertation) or Advisor (if thesis)
Spinella, Michael
Committee Member(s)
  • Vieson, Miranda D
  • Samuelson, Jonathan P
Department of Study
Vet Clinical Medicine
Discipline
VMS-Veterinary Clinical Medcne
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
  • testicular cancer
  • epigenetics
  • embryonal carcinoma
  • cisplatin
  • resistance
  • testicular germ cell tumors
Abstract
Testicular Germ Cell Tumors (TGCTs) are a heterogenous group of neoplasms derived from totipotent primordial germ cells. These tumors are the most common solid tumor of men 15-44 years of age within the United States, and there has been an estimated 43.6% increase in cases between 2000-2022. The majority of these tumors are exceptionally susceptible to cisplatin-based chemotherapies, however, there are no second-line treatments for chemoresistant tumors. Recent studies have suggested that epigenetic factors may influence both the development of TGCTs and their sensitivity to cisplatin. An important epigenetic modification is the transformation of H3K27 to H3K27me3 via methylation of the histone 3 at the docking site K27 on polycomb repressive complex 2. Decreased H3K27me3 levels have been associated with chemoresistance in TGCT cell lines, and restoration of normal methylation levels has conferred chemosensitivity to these previously resistant cells. This association has not been exhaustively studied in vivo. The objective of this work was to develop an immunohistochemical (IHC) stain for H3K27me3 that could be applied to patient TGCT samples to determine levels of H3K27me3 expression, and to correlate that expression to clinical behavior. We hypothesized that the H3K27me3 IHC would be effective in demonstrating different levels of H3K27me3 expression in both TGCT cell lines and in human biopsy samples. Additionally, we hypothesized that there will be differences in staining depending on the TGCT aggressiveness, subtype, and response to chemotherapy. Specifically, that more differentiated and more chemoresistant tumors would have lower H3K27me3 expression. This study confirmed the primary hypothesis that an immunohistochemical stain for H3K27me3 could be used for analysis of H3K27me3 expression. Additionally, a detailed protocol for the evaluation of the H3K27me3 IHC was established, which utilized both digital whole-slide imaging techniques and basic artificial intelligence programs to minimize human subjectivity and error in IHC analysis. Through this protocol, semi-quantitative data was derived from each whole-slide image, allowing for analysis of IHC staining intensity within each slide, and comparison between each case for assessment of trends. Our overall findings show significantly lower expression of H3K27me3 amongst cisplatin resistant TGCTs compared to their cisplatin susceptible counterparts. In particular, cisplatin resistant teratomas and embryonal carcinomas both have lower expressions than cisplatin susceptible teratomas. Metastatic TGCTs had a greater H3K27me3 expression than primary tumors, but this difference was not statistically significant. No differences were seen within the H3K27me3 expression between cisplatin susceptible and cisplatin resistant primary and metastatic TGCTs. Overall, this data supports our hypothesis that cisplatin resistant tumors would have a lower expression than cisplatin susceptible tumors and suggests that H3K27me3 may have an influence on the behavior of TGCTs.
Graduation Semester
2024-05
Type of Resource
Thesis
Copyright and License Information
Copyright 2024 Maryanna Parker

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