| Author: | Mahanty, Arpan |
| Title: | Development of a fluorescence molecular imaging technique for glioblastoma diagnosis by targeting macrophage polarization |
| Advisors: | Yoo, Jung Sun (HTI) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Glioblastoma multiforme Gliomas -- Imaging Brain -- Tumors Molecular probes Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Health Technology and Informatics |
| Pages: | xix, 201 pages : color illustrations |
| Language: | English |
| Abstract: | The glioblastoma multiforme (GBM), known as human brain cancer (Class IV), is extremely aggressive and lethal in nature. The overall survival period of the patients can be extended up to only 14 months even after early diagnosis or treatment with advanced technologies. Only 10% of patients have a survival period of 5 years after diagnosis. The GBM does not have any prominent boundary, which makes it difficult to be properly identified from the normal brain tissues. Surgery is the current gold standard for GBM treatment but the complete surgical removal of GBM tissues is almost impossible due to their diffusive characteristics into the surrounding normal brain tissues, thus resulting in high recurrence rates [4-6]. Temozolomide chemotherapy is an additional treatment option; however, its efficacy is not satisfactory and therapeutic resistance is high because of molecularly heterogeneous malignancy of GBM. Invasive, infiltrative, and heterogeneous features of GBM challenge the currently available diagnostic and therapeutic practice in clinics. To overcome this limitation, there is an urgent need to develop a reliableimaging tool for correct diagnosis and assessment of GBM, as well as image-guided surgery to demonstrate a clear margin of GBM in the surgery room. Moreover, a diagnostic index to be used in further therapeutic decision making that maximizes clinical efficacy to increase patient survival rates is needed. The immune system is crucial in cancer biology, and it is also important to understand the complexities of GBM by investigating the immune responses in order to create a new strategy for sensitive diagnosis and treatments. Earlier studies have shown that a large proportion of immune responsive microglias and macrophages infiltrating intoglioblastoma, which contribute to 30-50 % of the tumor mass. As a consequence, for effective glioblastoma therapy, it is critical to assess not only the tumor cell fate but also the prevalence of differentiated microglias/macrophages. M1 (inflammatory) and M2 (non-inflammatory) subsets of microglia/macrophages exist. The M1 subset offers tumor suppressive abilities and promotes immune vigilance and pathogen termination. Conversely, the M2 subset has a tumor-supportive behavior with immune suppression to promote tumor progression, angiogenesis, and tissue remodeling. GBM can eliminate the inflammatory immune response and allow tumor growth by transforming the microenvironment as immunosuppressive through various pathways, specifically cytokine-dependent pathways, which leads to recruiting tumor supportive M2 microglias/ macrophages. As the diffuse characteristic of glioma morphology does not exhibit the regular tumor margin, recent research has focused on the possibility of identifying M2 macrophages for improved cancer diagnosis and prognosis. However, efforts to measure specifically M1 and M2 macrophages together and target 'bad' macrophages without affecting 'good' macrophages are scarce and remain challenging. We believe specific M1/M2 macrophage ratio imaging and M2-targeted treatment will provide a powerful tool for better diagnosis and prognosis, surgery guidance by revealing glioblastoma margin, and improve patient outcome. From the above background and niche of this research, I have optimized M1 and M2 specific molecular probes for M1/M2 macrophage/microglia identification. I demonstrated in vitro M1/M2 differentiation using mouse bone marrow-derived macrophages (BMDM) and a mouse microglia cell line (BV2) to target M1/M2 cells and a newly created automated CellProfiler-based pipeline was constructed to identify polarization state from fluorescence images of macrophage/microglias. The newly developed pipeline was cross-examined with CD86⁺ and CD206⁺ staining, flow cytometry, and qRT- analysis were used to identify differentiated M1 and M2 macrophages/microglias. In vivo fluorescence imaging on orthotopic xenograft and allograft GBM models comprised with an enriched localization of M2 macrophages/microglias to the tumor site. In vivo histopathological staining examination revealed the presence of M1 and M2 macrophage/microglial localization surrounding the GBM tumor (co-localized with GBM/M1/M2⁺). Ex-vivo organ distribution imaging also demonstrates molecular probe selectivity with little nonspecific organ distribution. This study investigated molecular probes that allow visualization of the condition of GBM tumors with prominent boundaries, which provides a basis for helping a surgeon for real time defining the GBM boundary area from its surrounding tissues and allows them to optimize decision making for precise tumor resection. My research, which has improved real time immune cell imaging (M1/M2) in GBM, has provided the groundwork for future diagnostic and therapeutic developments with translational importance. |
| Rights: | All rights reserved |
| Access: | open access |
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