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Open Access Publications from the University of California

Scholarly Works (7 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2024)

All living matter is under constant environmental stress that jeopardizes the genomic integrity of individual cells and the functional integrity of tissues in higher organisms. At the level of non-post-mitotic tissues, stem cells constantly divide to give rise to all lineages of differentiated cells. Once thought to be unidirectional, cellular differentiation can now be reversed and overexpression of developmental transcription factors can turn somatic cells into induced pluripotent stem cells by means of reprogramming. This process is critically dependent on optimal co-stimulation of the innate immune response through activation of pattern recognition receptors (PRRs) by pathogen and/or damage associated molecular patterns (PAMPs/DAMPs). Ionizing radiation (IR) being an extreme form of genotoxic stress, can lead to the release of DAMPs. Our lab has identified that radiation induces the formation of cancer stem cells from non-cancer stem cells, a process termed IR-induced phenotype conversion. Cellular plasticity, an umbrella term encompassing reprogramming and radiation-induced phenotypic conversion events, allows cells to effectively respond to triggers that would otherwise compromise them. The underlying mechanisms driving these processes are incompletely understood but PAMPs and DAMPs are readily involved and employ common pathways downstream of their respective receptors. Glioblastoma (GBM) is a highly aggressive, malignant primary brain tumor for which cancer stem cells play a critical role in therapy resistance, recurrence and overall disease progression. This in combination with the radiation-induced cellular plasticity response could further exacerbate patient outcome if unaccounted for. Thus, to better understand the underlying mechanisms driving IR-induced cellular plasticity events, cancer stem cell maintenance/self-renewal (SFAs, ELDAs) and de novo stem cell induction (reprogramming assays) were studied using patient-derived glioblastoma cells. Several Toll-like receptors (TLRs) as well as components of the free cytosolic DNA sensing machinery, the cGAS/STING pathway, were evaluated. Our main study findings were as follows: 1) stem cell maintenance following irradiation is mediated through cGAS-independent STING signaling, with potential crosstalk with TLR4 and TLR9 and 2) de novo stem cell induction following irradiation implicates TLR3 signaling and potentially other receptors and processes affected by chloroquine. Collectively, these point to a direct link between innate immune signaling and IR-induced cellular plasticity events.

    Cover page: Investigating the role of select receptors in radiation-induced cellular plasticity events in glioblastoma
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2022)
    Hair shafts from three trichothiodystrophy (TTD) patients with mutations in the ERCC2 (XPD) gene were examined by transmission electron microscopy. TTD is a rare, recessive disorder with mutations in several genes in the DNA repair/transcription pathway, including ERCC2. Unlike previous studies, the hair shafts were examined after relaxation of their structure by partial disulphide bond reduction in the presence of sodium dodecyl sulphate, permitting improved visualization. Compared with hair shafts of normal phenotype, TTD cuticle cells displayed aberrant marginal bands and exocuticle layers. Clusters of cells stained differently (light versus dark) in the cortex of aberrant shafts, and the keratin macrofibrils appeared much shorter in the cytoplasm. Considerable heterogeneity in these properties was evident among samples and even along the length of single hair shafts. The results are consistent with not only a paucity of high sulphur components, such as keratin-associated proteins, but also a profound imbalance in protein content and organization.
      Cover page: Trichothiodystrophy hair shafts display distinct ultrastructural features
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2021)
      Pro-inflammatory conditions have long been associated with mammary carcinogenesis and breast cancer progression. The underlying mechanisms are incompletely understood but signaling of pro-inflammatory cytokine TNFα through its receptors TNFR1 and TNFR2 is a major mediator of inflammation in both obesity and in the response of tissues to radiation, 2 known risk factors for the development of breast cancer. Here, we demonstrated the loss of one TNFR2 allele led to ductal hyperplasia in the mammary gland with increased numbers of mammary epithelial stem cell and terminal end buds. Furthermore, loss of one TNFR2 allele increased the incidence of breast cancer in MMTV-Wnt1 mice and resulted in tumors with a more aggressive phenotype and metastatic potential. The underlying mechanisms include a preferential activation of canonical NF-κB signaling pathway and autocrine production of TNFα. Analysis of the TCGA dataset indicated inferior overall survival for patients with down-regulated TNFR2 expression. These findings unravel the imbalances in TNFR signaling promote the development and progression of breast cancer, indicating that selective agonists of TNFR2 could potentially modulate the risk for breast cancer in high-risk populations.
        Cover page: Tumor necrosis factor receptor signaling modulates carcinogenesis in a mouse model of breast cancer
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2024)
        Glioblastoma (GBM) is the deadliest adult brain cancer. Under the current standard of care, almost all patients succumb to the disease and novel treatments are urgently needed. Recognizing that GBMs are addicted to cholesterol, past clinical trials have repurposed statins against GBM but failed. The purpose of this study was to test whether treatments that upregulate the cholesterol biosynthesis pathway in GBM would generate a metabolic vulnerability that can be exploited using statins and to determine the underlying mechanisms.Effects of radiotherapy and temozolomide or dopamine receptor antagonists on the mevalonate pathway in GBM were assessed in vitro and in vivo. The impact of statins on self-renewal of glioma stem cells and median survival was studied. Branches of the mevalonate pathway were probed to identify relevant effector proteins.Cells surviving combination treatments that converge in activating the immediate early response, universally upregulated the mevalonate pathway and increased stemness of GBM cells through activation of the Rho-GTPase Rac-1. Activation of the mevalonate pathway and Rac-1 was inhibited by statins, which led to improved survival in mouse models of glioblastoma when combined with radiation and drugs that target the glioma stem cell pool and plasticity of glioma cells.We conclude that a combination of dopamine receptor antagonists and statins could potentially improve radiotherapy outcome and warrants further investigation.

        Significance

        Combination therapies that activate the mevalonate pathway in GBM cells after sublethal treatment enhance self-renewal and migratory capacity through Rac-1 activation, which creates a metabolic vulnerability that can be further potentially exploited using statins.
          Cover page: Activation of the Mevalonate Pathway in Response to Anti-cancer Treatments Drives Glioblastoma Recurrences Through Activation of Rac-1
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2021)

          Background

          Glioblastoma (GBM) is the deadliest of all brain cancers in adults. The current standard-of-care is surgery followed by radiotherapy and temozolomide, leading to a median survival time of only 15 months. GBM are organized hierarchically with a small number of glioma-initiating cells (GICs), responsible for therapy resistance and tumor recurrence, suggesting that targeting GICs could improve treatment response. ONC201 is a first-in-class anti-tumor agent with clinical efficacy in some forms of high-grade gliomas. Here we test its efficacy against GBM in combination with radiation.

          Methods

          Using patient-derived GBM lines and mouse models of GBM we test the effects of radiation and ONC201 on GBM self-renewalin vitro and survivalin vivo.A possible resistance mechanism is investigated using RNA-Sequencing.

          Results

          Treatment of GBM cells with ONC201 reduced self-renewal, clonogenicity and cell viabilityin vitro. ONC201 exhibited anti-tumor effects on radioresistant GBM cells indicated by reduced self-renewal in secondary and tertiary glioma spheres. Combined treatment of ONC201 and radiation prolonged survival in syngeneic and patient-derived orthotopic xenograft mouse models of GBM. Subsequent transcriptome analyses after combined treatment revealed shifts in gene expression signatures related to quiescent GBM populations, GBM plasticity, and GBM stem cells.

          Conclusions

          Our findings suggest that combined treatment with the DRD2/3 antagonist ONC201 and radiation improves the efficacy of radiation against GBMin vitroandin vivothrough suppression of GICs without increasing toxicity in mouse models of GBM. A clinical assessment of this novel combination therapy against GBM is further warranted.
            Cover page: Effects of the DRD2/3 antagonist ONC201 and radiation in glioblastoma
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2021)

            Background

            Glioblastoma is the deadliest brain tumor in adults, and the standard of care consists of surgery followed by radiation and treatment with temozolomide. Overall survival times for patients suffering from glioblastoma are unacceptably low indicating an unmet need for novel treatment options.

            Methods

            Using patient-derived HK-157, HK-308, HK-374, and HK-382 glioblastoma lines, the GL261 orthotopic mouse models of glioblastoma, and HK-374 patient-derived orthotopic xenografts, we tested the effect of radiation and the dopamine receptor antagonist quetiapine on glioblastoma self-renewal in vitro and survival in vivo. A possible resistance mechanism was investigated using RNA-sequencing. The blood-brain-barrier-penetrating statin atorvastatin was used to overcome this resistance mechanism. All statistical tests were 2-sided.

            Results

            Treatment of glioma cells with the dopamine receptor antagonist quetiapine reduced glioma cell self-renewal in vitro, and combined treatment of mice with quetiapine and radiation prolonged the survival of glioma-bearing mice. The combined treatment induced the expression of genes involved in cholesterol biosynthesis. This rendered GL261 and HK-374 orthotopic tumors vulnerable to simultaneous treatment with atorvastatin and further statistically significantly prolonged the survival of C57BL/6 (n = 10 to 16 mice per group; median survival not reached; log-rank test, P < .001) and NOD Scid gamma mice (n = 8 to 21 mice per group; hazard ratio = 3.96, 95% confidence interval = 0.29 to 12.40; log-rank test, P < .001), respectively.

            Conclusions

            Our results indicate promising therapeutic efficacy with the triple combination of quetiapine, atorvastatin, and radiation treatment against glioblastoma without increasing the toxicity of radiation. With both drugs readily available for clinical use, our study could be rapidly translated into a clinical trial.
              Cover page: Dopamine Receptor Antagonists, Radiation, and Cholesterol Biosynthesis in Mouse Models of Glioblastoma
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2020)

              Background

              Normal tissue toxicity is an inevitable consequence of primary or secondary brain tumor radiotherapy. Cranial irradiation commonly leads to neurocognitive deficits that manifest months or years after treatment. Mechanistically, radiation-induced loss of neural stem/progenitor cells, neuroinflammation, and demyelination are contributing factors that lead to progressive cognitive decline.

              Methods

              The effects of 1-[(4-nitrophenyl)sulfonyl]-4-phenylpiperazine (NSPP) on irradiated murine neurospheres, microglia cells, and patient-derived gliomaspheres were assessed by sphere-formation assays, flow cytometry, and interleukin (IL)-6 enzyme-linked immunosorbent assay. Activation of the hedgehog pathway was studied by quantitative reverse transcription PCR. The in vivo effects of NSPP were analyzed using flow cytometry, sphere-formation assays, immunohistochemistry, behavioral testing, and an intracranial mouse model of glioblastoma.

              Results

              We report that NSPP mitigates radiation-induced normal tissue toxicity in the brains of mice. NSPP treatment significantly increased the number of neural stem/progenitor cells after brain irradiation in female animals, and inhibited radiation-induced microglia activation and expression of the pro-inflammatory cytokine IL-6. Behavioral testing revealed that treatment with NSPP after radiotherapy was able to successfully mitigate radiation-induced decline in memory function of the brain. In mouse models of glioblastoma, NSPP showed no toxicity and did not interfere with the growth-delaying effects of radiation.

              Conclusions

              We conclude that NSPP has the potential to mitigate cognitive decline in patients undergoing partial or whole brain irradiation without promoting tumor growth and that the use of this compound as a radiation mitigator of radiation late effects on the central nervous system warrants further investigation.
                Cover page: 1-[(4-Nitrophenyl)sulfonyl]-4-phenylpiperazine treatment after brain irradiation preserves cognitive function in mice
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