Crentsil, Hannah Elizabeth
(2024)
A receptor tyrosine kinase/MALT1 axis promotes hallmarks of cancer in H3K27-altered diffuse midline glioma.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Background: H3K27-altered diffuse midline glioma (DMG) is a devastating pediatric brainstem tumor that affects 200-300 individuals in the US per year. Median survival is 9-11 months, and there are virtually no long-term survivors. Despite decades of clinical trials, radiation therapy remains standard of care, extending survival by 2-3 months. Elucidating the mechanisms that drive H3K27-altered DMG pathogenesis in order to uncover therapeutic vulnerabilities is of critical importance.
Recent studies implicate MALT1 as a potential therapeutic target in gliomas. MALT1 is the effector molecule of the CARMA-BCL10-MALT1 (CBM) signalosome, a cytoplasmic protein complex that drives downstream pro-survival transcriptional activity. MALT1, which possesses scaffolding and protease functions, promotes cell viability, proliferation, and migration/invasion in multiple solid tumor types in response to receptor tyrosine kinase (RTK) or G protein-coupled receptor (GPCR) signaling. We aim to evaluate the hypothesis that MALT1 promotes H3K27-altered DMG cell proliferation and migration in response to RTK activation and represents a therapeutic target in H3K27-altered DMG.
Methods/Results: We screened a panel of H3K27-altered DMG cell lines by Western blot and found that the CBM complex members CARMA3, MALT1 and BCL10 are expressed in H3K27-altered DMG cells. We next demonstrated that MALT1 is proteolytically active in H3K27-altered DMG cell lines. Specifically, we showed that the MALT1 protease substrate HOIL1 is cleaved in DMG cells, and that this cleavage is abrogated by treatment with the MALT1 protease inhibitor MLT-748. We next engineered multiple H3K27-altered DMG cell lines to express dox-inducible MALT1 shRNA in order to assess the impact of MALT1 deficiency on H3K27-altered DMG cell biology. Results from an Oncology Array membrane evaluating expression of over 80 cancer-implicated proteins in HSJD-DIPG-007 DMG cells demonstrate that among all proteins tested, the RTK EGFR demonstrates the greatest decrease in expression following MALT1 knockdown. Subsequent studies indicate the operation of a MALT1-RTK signaling axis in HSJD-DIPG-007 DMG cells, whereby MALT1 knockdown leads to reduced expression of the RTKs EGFR and FGFR1, as well as diminished proliferation in response to EGF and FGF and reduced migration towards EGF. In contrast, MALT1 knockdown does not lead to a phenotypic effect on migration and proliferation of BT245 and SF8628 DMG cell lines, indicating that these effects of MALT1 knockdown are cell line specific. These differences may be due to the distinct mutational profiles of the H3K27-altered DMG cell lines tested.
Conclusions/Future Directions: MALT1 is expressed and proteolytically active in H3K27-altered DMG cells. Our studies implicate MALT1 as a regulator of EGFR and FGFR1 expression and migration/proliferation in response to RTK ligand stimulation in HSJD-DIPG-007 DMG cells. Future studies will evaluate whether MALT1 regulates RTK expression in additional cell lines and cancer types and will determine whether MALT1 knockdown reduces H3K27-altered DMG tumor progression in vivo. As we continue to uncover the specific pathways at work that sensitize some H3K27-altered DMG cells to MALT1 targeting, we hope to determine whether MALT1 represents a potential therapeutic target in a subset of patients with H3K27-altered DMG.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
14 October 2024 |
| Date Type: |
Publication |
| Defense Date: |
29 July 2024 |
| Approval Date: |
14 October 2024 |
| Submission Date: |
12 August 2024 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
185 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Medicine > Cellular and Molecular Pathology |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
H3K27-altered DMG, MALT1, CBM signalosome, Cancer cell signaling |
| Date Deposited: |
14 Oct 2024 15:55 |
| Last Modified: |
14 Oct 2024 15:55 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/46918 |
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