UC Irvine

Glioblastoma is a highly aggressive CNS cancer that affects 3 in 100,000 people each year in the U.S. Most patients experience recurrence within the first year after initial diagnosis and after receiving standard of care. GBM is characterized by its high mitotic index, capacity to invade other regions of the brain and modulate the tumor microenvironment. Given the high rate of tumor recurrence treatment options are limited for patients suffering from GBM as tumors become non-responsive to standard of care treatment. Mechanisms of resistance in GBM can come from a variety of sources that include DNA damage response (DDR), glioma stem cells (GSCs), tumor microenvironment (TME), cell cycle arrest and metabolic reprogramming. Mitochondria-associated granulocyte macrophage colony-stimulating factor molecule (MAGMAS), a mitochondria protein and subunit of the translocase of the inner membrane 23 (TIM23) complex, regulates protein trafficking into the mitochondria by recruiting DNAJC19 to the TIM23 complex. Our research aim was to uncover the role of MAGMAS in GBM tumor biology and its contribution to mechanisms of resistance for TMZ. Computational analysis of MAGMAS/PAM16 expression levels from publicly available databases revealed that MAGMAS levels are significantly elevated in recurrent tumors and is positively correlated with the DNA repair MGMT. We tested our genetically modified glioma cells expressing shpam16 constructs and found that MAGMAS deficient glioma cells were sensitized to standard of care treatment. Additionally, we discovered that silencing MAGMAS/PAM16 reduced MGMT expression, increased IL7 expression and reduced extracellular excretion of lactic acid. Using our orthotopic xenograft mouse model, we transplanted our genetically modified cell lines with either scramble control or KD cells. We observed a significant increase in overall survival in KD TMZ treated mice when compared to scramble control TMZ group. Additionally, we also tested the efficacy of our small molecule inhibitor BT9 and its impact on cell death, cell proliferation and assessed the mechanism of action in GBM cells. Our results revealed that BT9 treatment induced ROS mediated apoptosis and was ameliorated by adding N-acetyl cysteine in combination with BT9, indicating that ROS is the main mechanism of programmed cell death. We also demonstrate that BT9 treatment reduces protein trafficking of nuclear encoded pre-cursor proteins important for aerobic respiration and maintaining mitochondrial homeostasis. Taken together, our results demonstrate that MAGMAS plays an important role in chemotherapy resistance, metabolic reprogramming and modulating the TME.