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Open Access Publications from the University of California

Scholarly Works (8 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2022)

Hotspot activating mutations in GNAQ/GNA11, encoding Gαq proteins, are driver oncogenes in uveal melanoma (UM), the primary cancer of the eye in adults, with limited additional aberrancies. However, there are few effective therapies available for UM and metastatic UM (mUM) patients, posing a critical need for novel therapeutic strategies against UM and mUM. Here, we have focused our efforts on dissecting Gαq-regulated signaling circuitries towards a better understanding of how Gαq promotes aberrant cell growth when activated, and to identify which Gαq-regulated signaling events can serve as actionable therapeutic targets for the treatment of UM. Using the convergence of bioinformatic, genetic and biochemical investigation, we uncovered a molecular framework poising Focal Adhesion Kinase (FAK) as a central mediator of oncogenic Gαq-regulated signaling, and as a controller of YAP through a mechanism suppressing the Hippo kinase cascade. We show that FAK inhibitors (FAKi) suppress YAP activation in vivo and halt UM growth, exposing a signaling vulnerability that can be targeted for UM treatment. Further interrogation into Gαq/FAK-regulated signaling mechanisms demonstrates that in addition to YAP, FAK controls PI3K/AKT signaling, and that UM cells require PI3K/AKT signaling for survival. These findings establish a novel link between Gαq-driven signaling and the stimulation of PI3K, and the aberrant activation of signaling networks underlying the growth and survival of UM. Finally, through a high-throughput, chemogenetic drug screen we profile the druggable landscape of UM and identified PKC inhibitors (PKCi) as a class targeting UM-specific vulnerabilities. Of note, we identified one compound with the highest preferential activity against UM. We investigated the mechanism of action of this compound, revealing a unique activity profile inhibiting PKC and PKC-related kinases, priming it to target cell-essential pathways that drive tumor growth in UM. Further work demonstrated that the combination of PKCi and FAKi synergistically inhibit UM growth and promote cytotoxic cell death in vitro and in preclinical xenograft and metastatic mouse models representing an exciting and highly translatable therapeutic strategy against UM. Collectively, the data presented here provides a wealth of information that can be readily translated to fill the lack of precision therapies against UM.

    Cover page: The GNAQ-oncogenic signaling network: Targeting FAK and its synthetic lethal interactome as a precision therapeutic approach against uveal melanoma
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2021)
    Breast cancer represents the most common diagnosed malignancy and the main leading cause of tumor-related death among women worldwide. Therefore, several efforts have been made in order to identify valuable molecular biomarkers for the prognosis and prediction of therapeutic responses in breast tumor patients. In this context, emerging discoveries have indicated that focal adhesion kinase (FAK), a non-receptor tyrosine kinase, might represent a promising target involved in breast tumorigenesis. Of note, high FAK expression and activity have been tightly correlated with a poor clinical outcome and metastatic features in several tumors, including breast cancer. Recently, a role for the integrin-FAK signaling in mechanotransduction has been suggested and the function of FAK within the breast tumor microenvironment has been ascertained toward tumor angiogenesis and vascular permeability. FAK has been also involved in cancer stem cells (CSCs)-mediated initiation, maintenance and therapeutic responses of breast tumors. In addition, the potential of FAK to elicit breast tumor-promoting effects has been even associated with the capability to modulate immune responses. On the basis of these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. Here, we recapitulate the multifaceted action exerted by FAK and its prognostic significance in breast cancer. Moreover, we highlight the recent clinical evidence regarding the usefulness of FAK inhibitors in the treatment of breast tumors.
      Cover page: Focal Adhesion Kinase Fine Tunes Multifaced Signals toward Breast Cancer Progression.
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2020)
      BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) has been rising in incidence primarily related to HPV-associated oropharyngeal cancers. Novel molecular therapeutics are evolving with the mTOR pathway as a new target. Previous studies have shown variable outcomes with relatively low toxicity. This study reports the tumor response, survivability, and toxicity of mTOR inhibitors (mTORi) in HNSCC. Despite expanding research on this pathway, there remains controversy around mTORi use for treatment of HNSCC. MATERIALS AND METHODS: Studies were included if: (a) Used mTORi alone or in combination with other treatment modalities in HNSCC. (b) Site of cancer included were one of the following: nasopharyngeal, oral cavity, oropharynx, hypopharynx or larynx. (c) All stages of cancer and treatment stage (neoadjuvant, adjuvant, and palliative) were included. The rate of adverse events (AEs), tumor response, progression free survival, and overall survival were meta-analyzed. RESULTS: From 1299 publications only 11 studies met inclusion criteria with a combined 232 total patients treated. Two studies used mTORi neoadjuvantly, five adjuvantly, and four in palliative/unresectable/metastatic setting. Monotherapeutic mTORi resulted in stabilization of disease (52.5%), but partial response was the most common response when mTORi were combined with chemotherapy and/or radiation (CRT) (48.1%). Survival rate was the highest in the mTORi combined with CRT. Hyperglycemia of any grade was the most commonly reported toxicity while grade 3 or less AEs were the most common grade of toxicity. CONCLUSION: The use of mTORi as monotherapy in HNSCC has thus far not yielded significant tumor response, however, in combination with other agents, an improved partial tumor response is evident that may or may not be associated with the addition of mTORi. Although adverse events were common, grade 4/5 AEs were uncommon. Further prospective, randomized clinical trials are necessary to confirm the direct roles of these agents in HNSCC tumor response. LEVEL OF EVIDENCE: 2a.
        Cover page: mTOR inhibitor use in head and neck squamous cell carcinoma: A meta-analysis on survival, tumor response, and toxicity.
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2024)
        Mathematical models of biochemical reaction networks are an important and emerging tool for the study of cell signaling networks involved in disease processes. One promising potential application of such mathematical models is the study of how disease-causing mutations promote the signaling phenotype that contributes to the disease. It is commonly assumed that one must have a thorough characterization of the network readily available for mathematical modeling to be useful, but we hypothesized that mathematical modeling could be useful when there is incomplete knowledge and that it could be a tool for discovery that opens new areas for further exploration. In the present study, we first develop a mechanistic mathematical model of a G-protein coupled receptor signaling network that is mutated in almost all cases of uveal melanoma and use model-driven explorations to uncover and explore multiple new areas for investigating this disease. Modeling the two major, mutually-exclusive, oncogenic mutations (Gαq/11 and CysLT2R) revealed the potential for previously unknown qualitative differences between seemingly interchangeable disease-promoting mutations, and our experiments confirmed oncogenic CysLT2R was impaired at activating the FAK/YAP/TAZ pathway relative to Gαq/11. This led us to hypothesize that CYSLTR2 mutations in UM must co-occur with other mutations to activate FAK/YAP/TAZ signaling, and our bioinformatic analysis uncovers a role for co-occurring mutations involving the plexin/semaphorin pathway, which has been shown capable of activating this pathway. Overall, this work highlights the power of mechanism-based computational systems biology as a discovery tool that can leverage available information to open new research areas.
          Cover page: Systems modeling of oncogenic G-protein and GPCR signaling reveals unexpected differences in downstream pathway activation.
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2019)
          Imbalanced angiogenesis is a characteristic of several diseases. Rho GTPases regulate multiple cellular processes, such as cytoskeletal rearrangement, cell movement, microtubule dynamics, signal transduction and gene expression. Among the Rho GTPases, RhoA, Rac1 and Cdc42 are best characterized. The role of endothelial Rac1 and Cdc42 in embryonic development and retinal angiogenesis has been studied, however the role of endothelial RhoA is yet to be explored. Here, we aimed to identify the role of endothelial RhoA in endothelial cell functions, in embryonic and retinal development and explored compensatory mechanisms. In vitro, RhoA is involved in cell proliferation, migration and tube formation, triggered by the angiogenesis inducers Vascular Endothelial Growth Factor (VEGF) and Sphingosine-1 Phosphate (S1P). In vivo, through constitutive and inducible endothelial RhoA deficiency we tested the role of endothelial RhoA in embryonic development and retinal angiogenesis. Constitutive endothelial RhoA deficiency, although decreased survival, was not detrimental for embryonic development, while inducible endothelial RhoA deficiency presented only mild deficiencies in the retina. The redundant role of RhoA in vivo can be attributed to potential differences in the signaling cues regulating angiogenesis in physiological versus pathological conditions and to the alternative compensatory mechanisms that may be present in the in vivo setting.
            Cover page: Endothelial RhoA GTPase is essential for in vitro endothelial functions but dispensable for physiological in vivo angiogenesis.
            • Article
            • Peer Reviewed
            UC San Francisco Previously Published Works (2016)

            Background

            Patients with recurrent/metastatic head and neck squamous cell carcinoma (HNSCC) demonstrate aberrant activation of the phosphotidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. We examined the efficacy of everolimus, an mTOR inhibitor, in patients with recurrent or metastatic HNSCC.

            Methods

            This single-arm phase II study enrolled biomarker-unselected patients with recurrent or metastatic HNSCC who failed at least 1 prior therapy. Everolimus was administered until progressive disease or unacceptable toxicity. Primary endpoint was clinical benefit rate (CBR). Secondary endpoints included progression-free survival (PFS), overall survival (OS), and evaluation of tissue and serum biomarkers related to the PIK3CA pathway.

            Results

            Seven of 9 patients treated in the first stage were evaluable. No objective responses were seen; CBR was 28%. Three patients discontinued everolimus because of toxicity. Median PFS and OS were 1.5 and 4.5 months, respectively. No activating PI3K mutations were identified in available tumor tissue.

            Conclusion

            Everolimus was not active as monotherapy in unselected patients with recurrent/metastatic HNSCC. © 2016 Wiley Periodicals, Inc. Head Neck 38: 1759-1764, 2016.
              Cover page: Phase II trial of everolimus in patients with previously treated recurrent or metastatic head and neck squamous cell carcinoma
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2024)
              UNLABELLED: The comprehensive genomic analysis of the head and neck squamous cell carcinoma (HNSCC) oncogenome revealed the frequent loss of p16INK4A (CDKN2A) and amplification of cyclin D1 genes in most human papillomavirus-negative HNSCC lesions. However, cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors have shown modest effects in the clinic. The aberrant activation of the PI3K/mTOR pathway is highly prevalent in HNSCC, and recent clinical trials have shown promising clinical efficacy of mTOR inhibitors (mTORi) in the neoadjuvant and adjuvant settings but not in patients with advanced HNSCC. By implementing a kinome-wide CRISPR/Cas9 screen, we identified cell-cycle inhibition as a synthetic lethal target for mTORis. A combination of mTORi and palbociclib, a CDK4/6-specific inhibitor, showed strong synergism in HNSCC-derived cells in vitro and in vivo. Remarkably, we found that an adaptive increase in cyclin E1 (CCNE1) expression upon palbociclib treatment underlies the rapid acquired resistance to this CDK4/6 inhibitor. Mechanistically, mTORi inhibits the formation of eIF4G-CCNE1 mRNA complexes, with the consequent reduction in mRNA translation and CCNE1 protein expression. Our findings suggest that mTORi reverts the adaptive resistance to palbociclib. This provides a multimodal therapeutic option for HNSCC by cotargeting mTOR and CDK4/6, which in turn may halt the emergence of palbociclib resistance. SIGNIFICANCE: A kinome-wide CRISPR/Cas9 screen identified cell-cycle inhibition as a synthetic lethal target of mTORis. A combination of mTORi and palbociclib, a CDK4/6-specific inhibitor, showed strong synergistic effects in HNSCC. Mechanistically, mTORis inhibited palbociclib-induced increase in CCNE1.
                Cover page: A Kinome-Wide Synthetic Lethal CRISPR/Cas9 Screen Reveals That mTOR Inhibition Prevents Adaptive Resistance to CDK4/CDK6 Blockade in HNSCC.
                • Article
                • Peer Reviewed
                UC San Diego Previously Published Works (2023)
                Immune checkpoint blockade (ICB) treatment has demonstrated excellent medical effects in oncology, and it is one of the most sought after immunotherapies for tumors. However, there are several issues with ICB therapy, including low response rates and a lack of effective efficacy predictors. Gasdermin-mediated pyroptosis is a typical inflammatory death mode. We discovered that increased expression of gasdermin protein was linked to a favorable tumor immune microenvironment and prognosis in head and neck squamous cell carcinoma (HNSCC). We used the mouse HNSCC cell lines 4MOSC1 (responsive to CTLA-4 blockade) and 4MOSC2 (resistant to CTLA-4 blockade) orthotopic models and demonstrated that CTLA-4 blockade treatment induced gasdermin-mediated pyroptosis of tumor cells, and gasdermin expression positively correlated to the effectiveness of CTLA-4 blockade treatment. We found that CTLA-4 blockade activated CD8+ T cells and increased the levels of interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) cytokines in the tumor microenvironment. These cytokines synergistically activated the STAT1/IRF1 axis to trigger tumor cell pyroptosis and the release of large amounts of inflammatory substances and chemokines. Collectively, our findings revealed that CTLA-4 blockade triggered tumor cells pyroptosis via the release of IFN-γ and TNF-α from activated CD8+ T cells, providing a new perspective of ICB.
                  Cover page: CTLA-4 blockade induces tumor pyroptosis via CD8+ T cells in head and neck squamous cell carcinoma.
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