Abstract IA020: Targeting mTOR signaling in oral premalignant lesions: From bench to clinic and back

Despite encouraging recent results from novel treatment options, such as immunotherapy, for head and neck squamous cell carcinoma (HNSCC), limited progress has been made in improving outcomes for most patients. Prevention and early detection are key to improving the prognosis of HNSCC. Our team has focused on decoding the oncogenic signaling circuitries driving HNSCC initiation and progression, aimed at identifying novel druggable targets to treat and prevent this aggressive malignancy. These efforts led to the early discovery that persistent activation of PI3K/mTOR signaling circuitry is the most frequent dysregulated signaling mechanism in HNSCC, and that in turn, the overreliance on PI3K/mTOR for HNSCC initiation and progression can be exploited for therapeutic purposes. Evidence will presented that mTOR inhibition exerts a potent antitumor activity in HNSCC patients in a recently reported window of opportunity clinical trial (NCT01195922). Thus, mTOR inhibitors can be considered for the prevention of HNSCC development and for the treatment of existing HNSCC lesions. However, their safety profile and tolerability may hamper their potential long-term use for HNSCC prevention. In this regard, we have shown that the repurposed drug metformin, which is safely used by millions of type 2 diabetes patients, decreases mTOR signaling in HNSCC and displays potent chemopreventive activity in experimental oral premalignancy models. Based on these findings, we have conducted a Phase IIa Clinical Trial using metformin for HNSCC prevention (NCT02581137) in patients with oral premalignant lesions (OPL), which was recently completed. Metformin administration resulted in mTOR inhibition, and improvement in the histological severity of 60% of the OPLs, including a subset (17%) of patients that exhibited complete responses. Ongoing experimental and planned clinical studies will be presented, which may provide a mechanistic framework for the use of metformin as a precision preventive agent for HNSCC.

Citation Format: J. Silvio Gutkind. Targeting mTOR signaling in oral premalignant lesions: From bench to clinic and back [abstract]. In: Proceedings of the Second Biennial NCI Meeting: Translational Advances in Cancer Prevention Agent Development (TACPAD); 2022 Sep 7-9. Philadelphia (PA): AACR; Can Prev Res 2022;15(12 Suppl_2): Abstract nr IA020.

A Randomized Multi-institutional Phase II Trial of Everolimus as Adjuvant Therapy in Patients with Locally Advanced Squamous Cell Cancer of the Head and Neck

PURPOSE

Investigate whether adjuvant everolimus, an mTOR inhibitor, improves progression-free survival (PFS) in advanced-stage head and neck squamous cell carcinoma (HNSCC) and provide outcomes related to correlative biological factors associated with disease control.

PATIENTS AND METHODS

This was a prospective, randomized, double-blind phase II trial of patients with advanced-stage HNSCC from 13 institutions who were confirmed disease-free post-definitive therapy and enrolled between December 2010 and March 2015. Patients received adjuvant everolimus or placebo daily (10 mg, oral) for a maximum of 1 year. p16 IHC as a surrogate marker for human papillomavirus infection and whole-exome sequencing were performed. Cox proportional hazard models estimated hazard rates. Log-rank tests evaluated differences in survival. The primary endpoint was PFS. Secondary endpoints and objectives included overall survival (OS) and toxicity assessment.

RESULTS

52 patients [median (range) age, 58 (37-76) years; 43 men (83%), 9 women (17%)] were randomized to placebo (n = 24) or everolimus (n = 28). PFS favored everolimus, but was not significant [log-rank P = 0.093; HR = 0.44; 95% confidence interval (CI), 0.17-1.17]. There was no difference in OS (P = 0.29; HR = 0.57; 95% CI, 0.20-16.2). Everolimus resulted in significant improvement in PFS for p16-negative patients (n = 31; P = 0.031; HR = 0.26; 95% CI, 0.07-0.97), although subgroup analysis showed no difference for p16-positive patients (n = 21; P = 0.93). Further, PFS was significantly higher in TP53-mutated (TP53mut) patients treated with everolimus compared with placebo (log-rank P = 0.027; HR = 0.24; 95% CI, 0.06-0.95). No treatment difference was seen in patients with TP53 wild-type tumors (P = 0.79).

CONCLUSIONS

p16-negative and TP53mut patients may benefit from adjuvant treatment with everolimus.

Challenges and Emerging Opportunities for Targeting mTOR in Cancer

The mechanistic target of rapamycin (mTOR) plays a key role in normal and malignant cell growth. However, pharmacologic targeting of mTOR in cancer has shown little clinical benefit, in spite of aberrant hyperactivation of mTOR in most solid tumors. Here, we discuss possible reasons for the reduced clinical efficacy of mTOR inhibition and highlight lessons learned from recent combination clinical trials and approved indications of mTOR inhibitors in cancer. We also discuss how the emerging systems level understanding of mTOR signaling in cancer can be exploited for the clinical development of novel multimodal precision targeted therapies and immunotherapies aimed at achieving tumor remission.

Integrating Genetic Alterations and the Hippo Pathway in Head and Neck Squamous Cell Carcinoma for Future Precision Medicine

Genetic alterations and dysregulation of signaling pathways are indispensable for the initiation and progression of cancer. Understanding the genetic, molecular, and signaling diversities in cancer patients has driven a dynamic change in cancer therapy. Patients can select a suitable molecularly targeted therapy or immune checkpoint inhibitor based on the driver gene alterations determined by sequencing of cancer tissue. This “precision medicine” approach requires detailed elucidation of the mechanisms connecting genetic alterations of driver genes and aberrant downstream signaling pathways. The regulatory mechanisms of the Hippo pathway and Yes-associated protein/transcriptional co-activator with PDZ binding motif (YAP/TAZ) that have central roles in cancer cell proliferation are not fully understood, reflecting their recent discovery. Nevertheless, emerging evidence has shown that various genetic alterations dysregulate the Hippo pathway and hyperactivate YAP/TAZ in cancers, including head and neck squamous cell carcinoma (HNSCC). Here, we summarize the latest evidence linking genetic alterations and the Hippo pathway in HNSCC, with the aim of contributing to the continued development of precision medicine.

Structural/functional studies of Trio provide insights into its configuration and show that conserved linker elements enhance its activity for Rac1

Trio is a large and highly conserved metazoan signaling scaffold that contains two Dbl family guanine nucleotide exchange factor (GEF) modules, TrioN and TrioC, selective for Rac and RhoA GTPases, respectively. The GEF activities of TrioN and TrioC are implicated in several cancers, especially uveal melanoma. However, little is known about how these modules operate in the context of larger fragments of Trio. Here we show via negative stain electron microscopy that the N-terminal region of Trio is extended and could thus serve as a rigid spacer between the N-terminal putative lipid-binding domain and TrioN, whereas the C-terminal half of Trio seems globular. We found that regions C-terminal to TrioN enhance its Rac1 GEF activity and thus could play a regulatory role. We went on to characterize a minimal, well-behaved Trio fragment with enhanced activity, Trio1284-1959, in complex with Rac1 using cryo-electron microscopy and hydrogen-deuterium exchange mass spectrometry and found that the region conferring enhanced activity is disordered. Deletion of two different strongly conserved motifs in this region eliminated this enhancement, suggesting that they form transient intramolecular interactions that promote GEF activity. Because Dbl family RhoGEF modules have been challenging to directly target with small molecules, characterization of accessory Trio domains such as these may provide alternate routes for the development of therapeutics that inhibit Trio activity in human cancer.

Lymphatic-preserving treatment sequencing with immune checkpoint inhibition unleashes cDC1-dependent antitumor immunity in HNSCC

Despite the promise of immune checkpoint inhibition (ICI), therapeutic responses remain limited. This raises the possibility that standard of care treatments delivered in concert may compromise the tumor response. To address this, we employ tobacco-signature head and neck squamous cell carcinoma murine models in which we map tumor-draining lymphatics and develop models for regional lymphablation with surgery or radiation. We find that lymphablation eliminates the tumor ICI response, worsening overall survival and repolarizing the tumor- and peripheral-immune compartments. Mechanistically, within tumor-draining lymphatics, we observe an upregulation of conventional type I dendritic cells and type I interferon signaling and show that both are necessary for the ICI response and lost with lymphablation. Ultimately, we provide a mechanistic understanding of how standard oncologic therapies targeting regional lymphatics impact the tumor response to immune-oncology therapy in order to define rational, lymphatic-preserving treatment sequences that mobilize systemic antitumor immunity, achieve optimal tumor responses, control regional metastatic disease, and confer durable antitumor immunity.

Monomethyl auristatin antibody and peptide drug conjugates for trimodal cancer chemo-radio-immunotherapy

Locally advanced cancers remain therapeutically challenging to eradicate. The most successful treatments continue to combine decades old non-targeted chemotherapies with radiotherapy that unfortunately increase normal tissue damage in the irradiated field and have systemic toxicities precluding further treatment intensification. Therefore, alternative molecularly guided systemic therapies are needed to improve patient outcomes when applied with radiotherapy. In this work, we report a trimodal precision cytotoxic chemo-radio-immunotherapy paradigm using spatially targeted auristatin warheads. Tumor-directed antibodies and peptides conjugated to radiosensitizing monomethyl auristatin E (MMAE) specifically produce CD8 T cell dependent durable tumor control of irradiated tumors and immunologic memory. In combination with ionizing radiation, MMAE sculpts the tumor immune infiltrate to potentiate immune checkpoint inhibition. Here, we report therapeutic synergies of targeted cytotoxic auristatin radiosensitization to stimulate anti-tumor immune responses providing a rationale for clinical translational of auristatin antibody drug conjugates with radio-immunotherapy combinations to improve tumor control.

Abstract 2107: CHMP2A regulates NK cell-mediated anti-tumor activity in a syngeneic HNSCC model

Natural killer (NK) cells are a key effector in antitumor immunity. However, tumors often acquire resistance programs to escape NK cell-mediated immunosurveillance. Identifying targetable vulnerabilities that reinvigorate NK cell-driven antitumor immunity can enable new therapeutic strategies to improve NK cell-mediated anti-tumor activity. Previous studies from our group used a whole genome CRISPR-Cas9 screen that identified CHMP2A as a gene that mediates tumor-intrinsic resistance to NK cell cytotoxicity. CHMP2A is a member of the ESCRTIII complex and regulates secretion of tumor-derived chemokines and extracellular vehicles (EVs) that express NK cell-activating ligands MICA/B and TRAIL, which induce NK apoptosis. Previously, we demonstrated that the deletion of CHMP2A in glioblastoma and head and neck squamous cell carcinoma (HNSCC) increases allogeneic NK cell-mediated killing both in vitro and in vivo. Here, we extend these studies to explore whether CHMP2A may serve as a targetable regulator of NK cell-mediated immunity. Employing our recently characterized syngeneic, tobacco-signature murine HNSCC model, 4MOSC (PMID: 31804466), we deleted CHMP2A in both the immune-responsive 4MOSC1 and immune-insensitive 4MOSC2 cell line. In vitro NK cell cytotoxicity assays reveal that 4MOSC1-CHMP2A-KO cells were more potently killed by NK cells compared to 4MOSC1-WT cells (53% increased cytotoxicity, p<0.001). In contrast, there was no significant difference in NK cell-mediated killing of 4MOSC2-WT versus CHMP2A-KO cells. Following orthotopic transplantation into immunocompetent hosts, we find that 4MOSC1-KO, but not 4MOSC2-WT, tumors spontaneously regress in vivo compared to wild type tumors (4MOSC1 KO with 80% regression, p=0.0476). Moreover, we find that NK cell depletion, achieved with systemic delivery of the blocking antibody PK136, was sufficient to reverse the complete response of 4MOSC1 tumors to anti CTLA-4 immune checkpoint inhibition (p<0.01), implying promise for combination therapeutic strategies in immunotherapy insensitive tumors. Ongoing studies are using IHC and mass cytometry (Cytof) to characterize the immune infiltrates to better define immune cell populations regulated by CHMP2A-mediated resistance of tumor cells to NK cell and possibly T-cell-mediated responses. Together, these studies demonstrate that CHMP2A provides a targetable, tumor-derived inhibitor of NK cell-driven antitumor immunity. Moreover, our preclinical model features HNSCC cell lines with variable sensitivity to CHMP2A-deletion to enable future studies to target key pathways to overcome resistance programs and mediate improved anti-tumor activity.

Citation Format: Jiyoung Yun, Robert Saddawi-Konefka, Benjamin Goldenson, Riyam Al-msari, J Silvio Gutkind, Dan S. Kaufman. CHMP2A regulates NK cell-mediated anti-tumor activity in a syngeneic HNSCC model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2107.

Abstract 3027: Elucidating the role of glutamine metabolism in head & neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, resulting in over 14,600 deaths each year in the United States alone. HNSCC is associated with human papillomavirus (HPV) infection, tobacco use, and abusive alcohol intake. Without truly effective targeted therapies, surgery and radiotherapy represent the primary treatment options for most patients. Unfortunately, these treatments are associated with significant morbidity and a reduction in quality of life. Immunotherapies have recently revolutionized HNSCC treatment, but <20% of patients exhibit clinical responses, albeit often not durable (Saddawi-Konefka et al. Frontiers in Oncology 2021). This highlights the unmet need to identify novel therapeutic options and biomarkers predicting a more favorable response to maximize the efficacy of targeted cancer strategies for HNSCC treatment. Glutamine is a conditionally essential amino acid for rapidly proliferating cancer cells making glutamine pathway inhibition an attractive approach for anti-cancer therapy. We found that treatment with the broad glutamine antagonist sirpiglenastat (DRP-104), which irreversibly inhibits all known enzymes involved in glutamine metabolism, results in metabolically halted cell growth in a large panel (n=8) of HPV- and HPV+ HNSCC cell lines (IC50 of 0.2-25uM). Interestingly, HNSCC cells bearing genetic alterations in PIK3CA and PTEN were significantly more sensitive to glutamine antagonism than unaltered HNSCC cells. The dependence of glutamine in HNSCC growth and the increased sensitivity of PIK3CA/PTEN aberrant cells was also observed in orosphere assays and HNSCC tumor xenografts in mice in vivo. We next explored the mechanism of glutamine suppression in HNSCC by integrating the results from genome-wide CRISPR-Cas9 knockout library screens and broad-spectrum metabolomics analysis. Both approaches converged on the identification of a dysregulated metabolic pathway that represents a synthetic lethal vulnerability that can be exploited via targeted therapies. Our data suggest that broad glutamine antagonism using sirpiglenastat (DRP-104) has therapeutic potential in HNSCC by dismantling cancer metabolism and sensitizing cells to additional perturbations leading to specific cell death. A clinical trial of sirpiglenastat (DRP-104) is currently ongoing (NCT04471415).

Citation Format: Michael Allevato, Yumi Yokoyama, Robert Wild, J. Silvio Gutkind. Elucidating the role of glutamine metabolism in head & neck squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3027.

Abstract 3825: Germline modifiers of the tumor immune microenvironment reveal drivers of immunotherapy response

With the continued promise of immunotherapy as an avenue for treating cancer, understanding how host genetics contributes to the tumor immune microenvironment (TIME) is essential to tailoring cancer risk screening and treatment strategies. Using genotypes from over 8,000 European individuals in The Cancer Genome Atlas and 137 heritable tumor immune phenotype components (IP components), we identified and investigated 532 TIME-SNPs. Focusing on 77 variants that were relevant to cancer risk, survival, or treatment response, we explored their potential to reveal novel targets for immunotherapy. Many variants overlapped regions with histone marks indicating active transcription, and influenced gene activities in specific immune cell subsets, such as macrophages and dendritic cells. TIME-SNPs implicated genes such as LAIR1, TREX1, CTSS, CTSW and LILRB2 were differentially expressed between responders and non-responders to immune-checkpoint blockade (ICB) in preclinical studies. Of these, LILRB2 and LAIR1 have already been identified as putative targets for immunotherapy. Here we found that inhibition of CTSS led to better tumor control and survival in murine models, alone or in combination with anti-PD-1. Collectively we show that through an integrative approach, it is possible to link host genetics to TIME characteristics, informing novel biomarkers for cancer risk and target identification in immunotherapy.

Citation Format: Meghana Pagadala, Victoria Wu, Eva Pérez-Guijarro, Hyo Kim, Andrea Castro, James Talwar, Cristian Gonzalez-Colin, Steven Cao, Benjamin J. Schmiedel, Timothy Sears, Shervin Goudarzi, Divya Kirani, Rany M. Salem, Gerald P. Morris, Olivier Harismendy, Sandip P. Patel, Jill P. Mesirov, Maurizio Zanetti, Chi-Ping Day, Chun C. Fan, Wesley K. Thompson, Glenn Merlino, J. Silvio Gutkind, Pandurangan Vijayanand, Hannah Carter. Germline modifiers of the tumor immune microenvironment reveal drivers of immunotherapy response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3825.

Focal Adhesion Kinase (FAK)-Hippo/YAP transduction signaling mediates the stimulatory effects exerted by S100A8/A9-RAGE system in triple-negative breast cancer (TNBC)

BACKGROUND

Understanding the intricate signaling network involved in triple-negative breast cancer (TNBC) represents a challenge for developing novel therapeutic approaches. Here, we aim to provide novel mechanistic insights on the function of the S100A8/A9-RAGE system in TNBC.

METHODS

TNM plot analyzer, Kaplan-Meier plotter, Meta-analysis, GEPIA2 and GOBO publicly available datasets were used to evaluate the clinical significance of S100A8/A9 and expression levels of S100A8/A9, RAGE and Filamin family members in breast cancer (BC) subtypes. METABRIC database and Cox proportional hazard model defined the clinical impact of high RAGE expression in BC patients. Multiple bioinformatics programs identified the main enriched pathways within high RAGE expression BC cohorts. By lentiviral system, TNBC cells were engineered to overexpress RAGE. Western blotting, immunofluorescence, nucleus/cytoplasm fractionation, qRT-PCR, gene silencing and luciferase experiments were performed to identify signal transduction mediators engaged by RAGE upon stimulation with S100A8/A9 in TNBC cells. Proliferation, colony formation and transwell migration assays were carried out to evaluate the growth and migratory capacity of TNBC cells. Statistical analysis was performed by ANOVA and independent t-tests.

RESULTS

We found a remarkable high expression of S100A8 and S100A9 in BC, particularly in HER2-positive and TNBC, with the latter associated to worst clinical outcomes. In addition, high RAGE expression correlated with a poor overall survival in BC. Next, we determined that the S100A8/A9-RAGE system triggers FAK activation by engaging a cytoskeleton mechanosensing complex in TNBC cells. Through bioinformatics analysis, we identified the Hippo pathway as the most enriched in BC patients expressing high RAGE levels. In accordance with these data, we demonstrated the involvement of S100A8/A9-RAGE-FAK signaling in the control of Hippo/YAP activities, and we established the crucial contribution of RAGE-FAK-YAP circuitry in the growth and migratory effects initiated by S100A8/A9 in TNBC cells.

CONCLUSIONS

The present study provides novel mechanistic insights on RAGE actions in TNBC. Moreover, our findings suggest that RAGE-FAK-YAP transduction pathway could be exploited as a druggable system halting the aggressive TNBC subtype.

PRECOGx: exploring GPCR signaling mechanisms with deep protein representations

In this study we show that protein language models can encode structural and functional information of GPCR sequences that can be used to predict their signaling and functional repertoire. We used the ESM1b protein embeddings as features and the binding information known from publicly available studies to develop PRECOGx, a machine learning predictor to explore GPCR interactions with G protein and β-arrestin, which we made available through a new webserver (https://precogx.bioinfolab.sns.it/). PRECOGx outperformed its predecessor (e.g. PRECOG) in predicting GPCR-transducer couplings, being also able to consider all GPCR classes. The webserver also provides new functionalities, such as the projection of input sequences on a low-dimensional space describing essential features of the human GPCRome, which is used as a reference to track GPCR variants. Additionally, it allows inspection of the sequence and structural determinants responsible for coupling via the analysis of the most important attention maps used by the models as well as through predicted intramolecular contacts. We demonstrate applications of PRECOGx by predicting the impact of disease variants (ClinVar) and alternative splice forms from healthy tissues (GTEX) of human GPCRs, revealing the power to dissect system biasing mechanisms in both health and disease.

Genomic Hippo Pathway Alterations and Persistent YAP/TAZ Activation: New Hallmarks in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) represents a highly prevalent and deadly malignancy worldwide. The prognosis for locoregionally advanced HNSCC has not appreciably improved over the past 30 years despite advances in surgical, radiation, and targeted therapies and less than 20% of HNSCC patients respond to recently approved immune checkpoint inhibitors. The Hippo signaling pathway, originally discovered as a mechanism regulating tissue growth and organ size, transduces intracellular and extracellular signals to regulate the transcriptional co-activators YAP and TAZ. Alterations in the Hippo pathway resulting in persistent YAP and TAZ activation have emerged as major oncogenic drivers. Our analysis of the human HNSCC oncogenome revealed multiple genomic alterations impairing Hippo signaling and activating YAP and TAZ, which in turn contribute to HNSCC development. This includes mutations and deletions of the FAT1 gene (29%) and amplification of the WWTR1 (encoding TAZ, 14%) and YAP1 genes (8%), together representing one of the most genetically altered signaling mechanisms in this malignancy. Here, we discuss key elements of the mammalian Hippo pathway, detail mechanisms by which perturbations in Hippo signaling promote HNSCC initiation and progression and outline emerging strategies to target Hippo signaling vulnerabilities as part of novel multimodal precision therapies for HNSCC.

Microneedle-mediated Intratumoral Delivery of Anti-CTLA-4 Promotes cDC1-dependent Eradication of Oral Squamous Cell Carcinoma with Limited irAEs

Head and neck squamous cell carcinoma (HNSCC) ranks sixth in cancer incidence worldwide and has a 5-year survival rate of only 63%. Immunotherapies-principally immune checkpoint inhibitors (ICI), such as anti-PD-1 and anti-CTLA-4 antibodies that restore endogenous antitumor T-cell immunity-offer the greatest promise for HNSCC treatment. Anti-PD-1 has been recently approved for first-line treatment of recurrent and metastatic HNSCC; however, less than 20% of patients show clinical benefit and durable responses. In addition, the clinical application of ICI has been limited by immune-related adverse events (irAE) consequent to compromised peripheral immune tolerance. Although irAEs are often reversible, they can become severe, prompting premature therapy termination or becoming life threatening. To address the irAEs inherent to systemic ICI therapy, we developed a novel, local delivery strategy based upon an array of soluble microneedles (MN). Using our recently reported syngeneic, tobacco-signature murine HNSCC model, we found that both systemic and local-MN anti-CTLA-4 therapy lead to >90% tumor response, which is dependent on CD8 T cells and conventional dendritic cell type 1 (cDC1). However, local-MN delivery limited the distribution of anti-CTLA-4 antibody from areas distal to draining lymphatic basins. Employing Foxp3-GFPDTR transgenic mice to interrogate irAEs in vivo, we found that local-MN delivery of anti-CTLA-4 protects animals from irAEs observed with systemic therapy. Taken together, our findings support the exploration of MN-intratumoral ICI delivery as a viable strategy for HNSCC treatment with reduced irAEs, and the opportunity to target cDC1s as part of multimodal treatment options to boost ICI therapy.

601 Sequencing immunotherapy before lymphatic ablation unleashes cDC1-dependent antitumor immunity in HNSCC

Background

Despite the proven efficacy of immune checkpoint inhibitor (ICI) therapy in the recurrent/metastatic setting for head and neck squamous cell carcinoma (HNSCC), clinical trials of ICI combined with curative-intent therapies have yielded equivocal results [1–4]. Collectively, this highlights gaps in our understanding of rational immune oncology (IO) treatment sequencing and suggests that the efficacy ICI may be disrupted by standard therapies, which necessarily compromise regional lymphatics.

Methods

We employ a preclinical model of tobacco-signature HNSCC to identify sequences of therapy that maximize durable response. By mapping the cervical lymphatic basins in the mouse, we define patterns of active antitumor immunosurveillance. Additionally, we establish tumors with distinct patterns of regional lymphatic drainage and develop a murine neck dissection (ND) model.

Results

We find that cervical lymphatic ablation, with ND or stereotactic body radiation therapy, in tumor bearing animals abolishes the response to ICI therapy, significantly impacting overall survival. Examination of the tumor immune microenvironment following ND reveals dramatic changes with a ten-fold increase in CD45 cells and exclusion of cytotoxic and antigen-specific lymphocytes. By examining the lymphatics removed at the time of ND, we find that conventional type I dendritic cells (cDC1s) and type I interferon (IFN-I) signaling are significantly increased, suggesting that these effectors are lost after curative-intent therapy. Depleting IFN-I or cDC1s blocks the response to ICI similar to lymphatic ablation. We find that successful primary response to ICI leads to durable immunity, conferred by systemically distributed memory T cells, not impaired by delayed ND. Lastly, we discover a rational IO treatment sequence by delivering neoadjuvant ICI followed by ND. Neoadjuvant ICI leads to complete tumor response, accumulation of nodal cDC1, and durable immunity. Surprisingly, the incidence of nodal metastasis at early timepoints reveals a similar burden of nodal disease between control and ICI-treated animals that decreases at late timepoints only with ICI treatment (44% vs 15%, n=25, p=0.033). This suggests that ICI also drives active immunosurveillance in regional, tumor-draining lymphatics, challenging the landmark findings from the definitive clinical trial demonstrating the benefit of elective versus therapeutic neck dissection for oral SCC patients with clinically negative necks.

Conclusions

This work demonstrates the necessity of preserving tumor-draining lymphatics during the tumor response to ICI therapy in HNSCC. Overall, we define rational IO treatment sequences to achieve optimal primary tumor response, durable antitumor immunity and immunosurveillance of regional metastatic disease. These findings can inform future clinical trials investigating combination IO therapy and treatment sequencing.

References

Harrington, K. J. et al. Nivolumab versus standard, single-agent therapy of investigator’s choice in recurrent or metastatic squamous cell carcinoma of the head and neck (CheckMate 141): health-related quality-of-life results from a randomised, phase 3 trial. Lancet Oncology 18, 1104–1115 (2017).

Burtness, B. et al. Pembrolizumab alone or with chemotherapy versus cetuximab with chemotherapy for recurrent or metastatic squamous cell carcinoma of the head and neck (KEYNOTE-048): a randomised, open-label, phase 3 study. Lancet (London, England) 394, 1915–1928 (2019).

Lee, N. Y. et al. Avelumab plus standard-of-care chemoradiotherapy versus chemoradiotherapy alone in patients with locally advanced squamous cell carcinoma of the head and neck: a randomised, double-blind, placebo-controlled, multicentre, phase 3 trial. Lancet Oncol 22, 450–462 (2021).

D’Cruz, A. K. et al. Elective versus Therapeutic Neck Dissection in Node-Negative Oral Cancer. New England Journal of Medicine 373, 521–529 (2015).

A protein network map of head and neck cancer reveals PIK3CA mutant drug sensitivity

[Figure: see text].

Interpretation of cancer mutations using a multiscale map of protein systems

A major goal of cancer research is to understand how mutations distributed across diverse genes affect common cellular systems, including multiprotein complexes and assemblies. Two challenges—how to comprehensively map such systems and how to identify which are under mutational selection—have hindered this understanding. Accordingly, we created a comprehensive map of cancer protein systems integrating both new and published multi-omic interaction data at multiple scales of analysis. We then developed a unified statistical model that pinpoints 395 specific systems under mutational selection across 13 cancer types. This map, called NeST (Nested Systems in Tumors), incorporates canonical processes and notable discoveries, including a PIK3CA-actomyosin complex that inhibits phosphatidylinositol 3-kinase signaling and recurrent mutations in collagen complexes that promote tumor proliferation. These systems can be used as clinical biomarkers and implicate a total of 548 genes in cancer evolution and progression. This work shows how disparate tumor mutations converge on protein assemblies at different scales.

Gαs-Protein Kinase A (PKA) Pathway Signalopathies: The Emerging Genetic Landscape and Therapeutic Potential of Human Diseases Driven by Aberrant Gαs-PKA Signaling

Many of the fundamental concepts of signal transduction and kinase activity are attributed to the discovery and crystallization of cAMP-dependent protein kinase, or protein kinase A. PKA is one of the best-studied kinases in human biology, with emphasis in biochemistry and biophysics, all the way to metabolism, hormone action, and gene expression regulation. It is surprising, however, that our understanding of PKA's role in disease is largely underappreciated. Although genetic mutations in the PKA holoenzyme are known to cause diseases such as Carney complex, Cushing syndrome, and acrodysostosis, the story largely stops there. With the recent explosion of genomic medicine, we can finally appreciate the broader role of the Gαs-PKA pathway in disease, with contributions from aberrant functioning G proteins and G protein-coupled receptors, as well as multiple alterations in other pathway components and negative regulators. Together, these represent a broad family of diseases we term the Gαs-PKA pathway signalopathies. The Gαs-PKA pathway signalopathies encompass diseases caused by germline, postzygotic, and somatic mutations in the Gαs-PKA pathway, with largely endocrine and neoplastic phenotypes. Here, we present a signaling-centric review of Gαs-PKA-driven pathophysiology and integrate computational and structural analysis to identify mutational themes commonly exploited by the Gαs-PKA pathway signalopathies. Major mutational themes include hotspot activating mutations in Gαs, encoded by GNAS, and mutations that destabilize the PKA holoenzyme. With this review, we hope to incite further study and ultimately the development of new therapeutic strategies in the treatment of a wide range of human diseases. SIGNIFICANCE STATEMENT: Little recognition is given to the causative role of Gαs-PKA pathway dysregulation in disease, with effects ranging from infectious disease, endocrine syndromes, and many cancers, yet these disparate diseases can all be understood by common genetic themes and biochemical signaling connections. By highlighting these common pathogenic mechanisms and bridging multiple disciplines, important progress can be made toward therapeutic advances in treating Gαs-PKA pathway-driven disease.

Calcium signaling induces a partial EMT

Epithelial plasticity, or epithelial-to-mesenchymal transition (EMT), is a well-recognized form of cellular plasticity, which endows tumor cells with invasive properties and alters their sensitivity to various agents, thus representing a major challenge to cancer therapy. It is increasingly accepted that carcinoma cells exist along a continuum of hybrid epithelial-mesenchymal (E-M) states and that cells exhibiting such partial EMT (P-EMT) states have greater metastatic competence than those characterized by either extreme (E or M). We described recently a P-EMT program operating in vivo by which carcinoma cells lose their epithelial state through post-translational programs. Here, we investigate the underlying mechanisms and report that prolonged calcium signaling induces a P-EMT characterized by the internalization of membrane-associated E-cadherin (ECAD) and other epithelial proteins as well as an increase in cellular migration and invasion. Signaling through Gαq-associated G-protein-coupled receptors (GPCRs) recapitulates these effects, which operate through the downstream activation of calmodulin-Camk2b signaling. These results implicate calcium signaling as a trigger for the acquisition of hybrid/partial epithelial-mesenchymal states in carcinoma cells.

Inhibition of mTOR signaling and clinical activity of metformin in oral premalignant lesions

BACKGROUND

The aberrant activation of the PI3K/mTOR signaling circuitry is one of the most frequently dysregulated signaling events in head and neck squamous cell carcinoma (HNSCC). Here, we conducted a single-arm, open-label phase IIa clinical trial in individuals with oral premalignant lesions (OPLs) to explore the potential of metformin to target PI3K/mTOR signaling for HNSCC prevention.

METHODS

Individuals with OPLs, but who were otherwise healthy and without diabetes, underwent pretreatment and posttreatment clinical exam and biopsy. Participants received metformin for 12 weeks (week 1, 500 mg; week 2, 1000 mg; weeks 3–12, 2000 mg daily). Pretreatment and posttreatment biopsies, saliva, and blood were obtained for biomarker analysis, including IHC assessment of mTOR signaling and exome sequencing.

RESULTS

Twenty-three participants were evaluable for response. The clinical response rate (defined as a ≥50% reduction in lesion size) was 17%. Although lower than the proposed threshold for favorable clinical response, the histological response rate (improvement in histological grade) was 60%, including 17% complete responses and 43% partial responses. Logistic regression analysis revealed that when compared with never smokers, current and former smokers had statistically significantly increased histological responses (P = 0.016). Remarkably, a significant correlation existed between decreased mTOR activity (pS6 IHC staining) in the basal epithelial layers of OPLs and the histological (P = 0.04) and clinical (P = 0.01) responses.

CONCLUSION

To our knowledge this is the first phase II trial of metformin in individuals with OPLs, providing evidence that metformin administration results in encouraging histological responses and mTOR pathway modulation, thus supporting its further investigation as a chemopreventive agent.

TRIAL REGISTRATION

NCT02581137

FUNDING

NIH contract HHSN261201200031I, grants R01DE026644 and R01DE026870

Abstract 1610: Local delivery of anti CTLA4 mediates cDC1 dependent eradication of HNSCC with limited IRAEs in a preclinical model of oral squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) ranks 6th in cancer incidence worldwide and has a five-year survival rate of only 63%. Despite advances in curative-intent therapies over the past three decades, rates of recurrence exceed 50% and long-term toxicities remain unacceptably morbid. Immunotherapies - principally immune checkpoint inhibitors (ICI) such as αPD-1 and αCTLA-41 antibodies which restore endogenous antitumor T cell immunity - offer the greatest promise for achieving durable response in HNSCC. However, the clinical application of ICI has been limited by immune-related adverse events (irAEs), which is a consequence of compromised peripheral immune tolerance after ICI therapy. Although irAEs are often reversible they can become severe, at best prompting premature termination of therapy or at worst becoming life-threatening. To address the off-target irAEs inherent to systemic ICI therapy, we developed a novel, local delivery strategy based upon an array of soluble microneedles (MN). Leveraging our recently reported syngeneic, tobacco-signature murine HNSCC model, we characterized the αCTLA-41 anti-tumor response as both CD8 T cell- and conventional dendritic cell type 1-dependent. When comparing αCTLA-4 therapy delivered in the traditional systemic format or with our local-MN delivery system, we found that while both routes of delivery led to >90% tumor responses, local-MN delivery achieved responses with lower total dosing while also limiting distribution of αCTLA-41 antibody from areas distal to draining lymphatic basins. Employing the previously described Foxp3-GFP-DTR GEMM developed for interrogation of murine irAEs, we found that local-MN protected animals from irAEs observed with systemic therapy. Taken together, our findings support the exploration of the microneedle array as a viable delivery strategy for ICI treatment in HNSCC.

Citation Format: Mara Gilardi, Zhiyong Wang, Victoria H. Wu, Miguel Angel Lopez-Ramirez, Fernando Soto-Alvarez, Robert Saddawi-Konefka, Dana Steffen, Marco Proietto, Zbigniew Mikulski, Haruka Miki, Jayanth Shankara Narayanan, Alfredo Molinolo, Joseph Wang, J. Silvio Gutkind. Local delivery of anti CTLA4 mediates cDC1 dependent eradication of HNSCC with limited IRAEs in a preclinical model of oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1610.

Abstract 1425: Synergistic antitumor efficacy of the dual RAF/MEK inhibitor VS-6766 with FAK inhibition for treatment of RAS-dependent solid tumors

The RAS/RAF/MEK/ERK pathway is the most mutated oncogenic pathway in cancer, and RAS pathway mutations often present with an overall worse prognosis. Although RAF and MEK have been validated as anticancer targets and several BRAF and MEK inhibitors (MEKi) are FDA approved, acquired resistance develops in most patients. Preclinically, inhibition of RAF or MEK has been found to activate focal adhesion kinase (FAK) signaling which may bypass RAS pathway blockade by driving tumor growth through activation of downstream pathways such as RhoA and YAP. VS-6766 is a unique dual RAF/MEK inhibitor which allows VS-6766 to block MEK signaling without the compensatory MEK activation that limits the efficacy of other MEK inhibitors. Defactinib is a selective FAK inhibitor (FAKi). Clinical studies are ongoing evaluating VS-6766 and defactinib for the treatment of various solid tumors. In 3D proliferation assays in vitro, defactinib was synergistic with VS-6766 or trametinib (MEKi) in reducing viability of several human tumor cell lines, including KRAS mutant (mt) ovarian cancer (TOV-21G) and KRAS-G12V mt non-small cell lung cancer (NSCLC; H441). We next investigated whether FAKi augments the efficacy of VS-6766 in solid tumor models. Combination of a FAKi with VS-6766 in a KRAS mt ovarian xenograft model (TOV21G) induced >30% tumor regression in 9/10 mice, whereas each agent alone induced mainly tumor stasis (>30% tumor regression with FAKi monotherapy or VS-6766 monotherapy in 1/10 and 3/10 mice, respectively) following 11 days of treatment. Similar results were observed in KRAS mt NSCLC (H2122) and GNAQ mt uveal melanoma (92.1) models in which the combination of FAKi with VS-6766 or trametinib induced tumor regression. In several patients with KRAS mt tumors, sequential biopsies showed that treatment with VS-6766 induced FAK activation (pY397) as a potential resistance mechanism, and this increased FAK activation was reversed in the presence of the defactinib/VS-6766 combination. Accordingly, the combination of VS-6766 with defactinib showed clinical activity in low grade serous ovarian cancer (LGSOC; ORR = 56% in KRAS-G12 mt and ORR = 41% in all 17 LGSOC patients; 8/17/20 data cut off). Importantly, the combination of defactinib with VS-6766 also induced responses in patients who had progressed on previous MEK inhibitor regimens. VS-6766 with defactinib also showed clinical activity in KRAS-G12V mt NSCLC. Furthermore, this combination regimen of VS-6766 with defactinib exhibited a manageable safety profile with no patients discontinuing for adverse events (NCT03875820). These preclinical and clinical data support the recent initiation of two registration-directed studies evaluating VS-6766 ± defactinib for the treatment of recurrent LGSOC with or without a KRAS mutation (NCT04625270) and recurrent NSCLC with KRAS-G12V or other KRAS mutation (NCT04620330).

Citation Format: Silvia Coma, Justine S. Paradis, J Silvio Gutkind, Jonathan A. Pachter. Synergistic antitumor efficacy of the dual RAF/MEK inhibitor VS-6766 with FAK inhibition for treatment of RAS-dependent solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1425.

G Protein-Coupled receptors and heterotrimeric G proteins as cancer drivers

G protein-coupled receptors (GPCRs) and heterotrimeric G proteins play central roles in a diverse array of cellular processes. As such, dysregulation of GPCRs and their coupled heterotrimeric G proteins can dramatically alter the signalling landscape and functional state of a cell. Consistent with their fundamental physiological functions, GPCRs and their effector heterotrimeric G proteins are implicated in some of the most prevalent human diseases, including a complex disease such as cancer that causes significant morbidity and mortality worldwide. GPCR/G protein-mediated signalling impacts oncogenesis at multiple levels by regulating tumour angiogenesis, immune evasion, metastasis, and drug resistance. Here, we summarize the growing body of research on GPCRs and their effector heterotrimeric G proteins as drivers of cancer initiation and progression, and as emerging antitumoural therapeutic targets.

Synthetic Lethal Screens Reveal Cotargeting FAK and MEK as a Multimodal Precision Therapy for GNAQ-Driven Uveal Melanoma

PURPOSE

Uveal melanoma is the most common eye cancer in adults. Approximately 50% of patients with uveal melanoma develop metastatic uveal melanoma (mUM) in the liver, even after successful treatment of the primary lesions. mUM is refractory to current chemo- and immune-therapies, and most mUM patients die within a year. Uveal melanoma is characterized by gain-of-function mutations in GNAQ/GNA11, encoding Gαq proteins. We have recently shown that the Gαq-oncogenic signaling circuitry involves a noncanonical pathway distinct from the classical activation of PLCβ and MEK-ERK. GNAQ promotes the activation of YAP1, a key oncogenic driver, through focal adhesion kinase (FAK), thereby identifying FAK as a druggable signaling hub downstream from GNAQ. However, targeted therapies often activate compensatory resistance mechanisms leading to cancer relapse and treatment failure.

EXPERIMENTAL DESIGN

We performed a kinome-wide CRISPR-Cas9 sgRNA screen to identify synthetic lethal gene interactions that can be exploited therapeutically. Candidate adaptive resistance mechanisms were investigated by cotargeting strategies in uveal melanoma and mUM in vitro and in vivo experimental systems.

RESULTS

sgRNAs targeting the PKC and MEK-ERK signaling pathways were significantly depleted after FAK inhibition, with ERK activation representing a predominant resistance mechanism. Pharmacologic inhibition of MEK and FAK showed remarkable synergistic growth-inhibitory effects in uveal melanoma cells and exerted cytotoxic effects, leading to tumor collapse in uveal melanoma xenograft and liver mUM models in vivo.

CONCLUSIONS

Coupling the unique genetic landscape of uveal melanoma with the power of unbiased genetic screens, our studies reveal that FAK and MEK-ERK cotargeting may provide a new network-based precision therapeutic strategy for mUM treatment.See related commentary by Harbour, p. 2967.