Embracing cancer complexity: Hallmarks of systemic disease

The last 50 years have witnessed extraordinary developments in understanding mechanisms of carcinogenesis, synthesized as the hallmarks of cancer. Despite this logical framework, our understanding of the molecular basis of systemic manifestations and the underlying causes of cancer-related death remains incomplete. Looking forward, elucidating how tumors interact with distant organs and how multifaceted environmental and physiological parameters impinge on tumors and their hosts will be crucial for advances in preventing and more effectively treating human cancers. In this perspective, we discuss complexities of cancer as a systemic disease, including tumor initiation and promotion, tumor micro- and immune macro-environments, aging, metabolism and obesity, cancer cachexia, circadian rhythms, nervous system interactions, tumor-related thrombosis, and the microbiome. Model systems incorporating human genetic variation will be essential to decipher the mechanistic basis of these phenomena and unravel gene-environment interactions, providing a modern synthesis of molecular oncology that is primed to prevent cancers and improve patient quality of life and cancer outcomes.

Cancer Evolution: A Multifaceted Affair

Cancer cells adapt and survive through the acquisition and selection of molecular modifications. This process defines cancer evolution. Building on a theoretical framework based on heritable genetic changes has provided insights into the mechanisms supporting cancer evolution. However, cancer hallmarks also emerge via heritable nongenetic mechanisms, including epigenetic and chromatin topological changes, and interactions between tumor cells and the tumor microenvironment. Recent findings on tumor evolutionary mechanisms draw a multifaceted picture where heterogeneous forces interact and influence each other while shaping tumor progression. A comprehensive characterization of the cancer evolutionary toolkit is required to improve personalized medicine and biomarker discovery.

SIGNIFICANCE

Tumor evolution is fueled by multiple enabling mechanisms. Importantly, genetic instability, epigenetic reprogramming, and interactions with the tumor microenvironment are neither alternative nor independent evolutionary mechanisms. As demonstrated by findings highlighted in this perspective, experimental and theoretical approaches must account for multiple evolutionary mechanisms and their interactions to ultimately understand, predict, and steer tumor evolution.

Cancer hallmarks intersect with neuroscience in the tumor microenvironment

The mechanisms underlying the multistep process of tumorigenesis can be distilled into a logical framework involving the acquisition of functional capabilities, the so-called hallmarks of cancer, which are collectively envisaged to be necessary for malignancy. These capabilities, embodied both in transformed cancer cells as well as in the heterotypic accessory cells that together constitute the tumor microenvironment (TME), are conveyed by certain abnormal characteristics of the cancerous phenotype. This perspective discusses the link between the nervous system and the induction of hallmark capabilities, revealing neurons and neuronal projections (axons) as hallmark-inducing constituents of the TME. We also discuss the autocrine and paracrine neuronal regulatory circuits aberrantly activated in cancer cells that may constitute a distinctive "enabling" characteristic contributing to the manifestation of hallmark functions and consequent cancer pathogenesis.

Bispecific PD1-IL2v and anti-PD-L1 break tumor immunity resistance by enhancing stem-like tumor-reactive CD8+ T cells and reprogramming macrophages

Immunotherapies have shown remarkable, albeit tumor-selective, therapeutic benefits in the clinic. Most patients respond transiently at best, highlighting the importance of understanding mechanisms underlying resistance. Herein, we evaluated the effects of the engineered immunocytokine PD1-IL2v in a mouse model of de novo pancreatic neuroendocrine cancer that is resistant to checkpoint and other immunotherapies. PD1-IL2v utilizes anti-PD-1 as a targeting moiety fused to an immuno-stimulatory IL-2 cytokine variant (IL2v) to precisely deliver IL2v to PD-1⁺ T cells in the tumor microenvironment. PD1-IL2v elicited substantial infiltration by stem-like CD8⁺ T cells, resulting in tumor regression and enhanced survival in mice. Combining anti-PD-L1 with PD1-IL2v sustained the response phase, improving therapeutic efficacy both by reprogramming immunosuppressive tumor-associated macrophages and enhancing T cell receptor (TCR) immune repertoire diversity. These data provide a rationale for clinical trials to evaluate the combination therapy of PD1-IL2v and anti-PD-L1, particularly in immunotherapy-resistant tumors infiltrated with PD-1⁺ stem-like T cells.

Abstract B41: Reprogramming immunosuppressive tumor-associated macrophages potentiates standard-of-care therapy in melanoma

Cutaneous melanoma is a highly aggressive cancer capable of distant and lethal metastatic spread. Recent breakthroughs have come from understanding oncogenic signaling and cancer immunobiology. Targeted therapies successfully block MAPK signaling in BRAFV600e mutant melanoma with remarkably high clinical responses followed by rapid relapse, whereas checkpoint inhibitors activating the immune response induce long-lasting responses, albeit only in a subset of patients. These limitations have driven interest in understanding innate and acquired resistance. Using an immunocompetent genetically-engineered mouse model of BRAF-driven melanoma, which phenocopies the human disease in its development, histopathology, and response to therapy, we focused on the tumor microenvironment (TME), seeking to elucidate resistance mechanisms. Our investigations have revealed that tumor-associated macrophages (TAMs) are a critical component of the TME, predominantly polarized toward a pro-tumoral “M2-like” phenotype, producing immunosuppressive factors and exhibiting extensive immuno-suppressive capabilities suggesting that they might significantly hinder immune responses in the melanoma TME. Seeking to assess their functional importance, we have found that combining conventional strategies with TAMs-reprogramming agents stimulates anti-tumor immune responses, leading to improved survival and responsiveness to standard-of-care therapies. These data highlight the central role played by macrophages in melanoma progression and demonstrate that pharmacologic reprogramming of macrophages represents a new therapeutic modality with the potential to elicit more effective anti-tumor immune responses against this devastating disease.

Citation Format: Melanie Tichet, Agnieszka Chryplewicz, Douglas Hanahan. Reprogramming immunosuppressive tumor-associated macrophages potentiates standard-of-care therapy in melanoma [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B41.

Aberrant hyperexpression of the RNA binding protein FMRP in tumors mediates immune evasion

Many human cancers manifest the capability to circumvent attack by the adaptive immune system. In this work, we identified a component of immune evasion that involves frequent up-regulation of fragile X mental retardation protein (FMRP) in solid tumors. FMRP represses immune attack, as revealed by cancer cells engineered to lack its expression. FMRP-deficient tumors were infiltrated by activated T cells that impaired tumor growth and enhanced survival in mice. Mechanistically, FMRP’s immunosuppression was multifactorial, involving repression of the chemoattractant C-C motif chemokine ligand 7 (CCL7) concomitant with up-regulation of three immunomodulators—interleukin-33 (IL-33), tumor-secreted protein S (PROS1), and extracellular vesicles. Gene signatures associate FMRP’s cancer network with poor prognosis and response to therapy in cancer patients. Collectively, FMRP is implicated as a regulator that orchestrates a multifaceted barrier to antitumor immune responses.

Cancer cell autophagy, reprogrammed macrophages, and remodeled vasculature in glioblastoma triggers tumor immunity

Glioblastoma (GBM) is poorly responsive to therapy and invariably lethal. One conceivable strategy to circumvent this intractability is to co-target distinctive mechanistic components of the disease, aiming to concomitantly disrupt multiple capabilities required for tumor progression and therapeutic resistance. We assessed this concept by combining vascular endothelial growth factor (VEGF) pathway inhibitors that remodel the tumor vasculature with the tricyclic antidepressant imipramine, which enhances autophagy in GBM cancer cells and unexpectedly reprograms immunosuppressive tumor-associated macrophages via inhibition of histamine receptor signaling to become immunostimulatory. While neither drug is efficacious as monotherapy, the combination of imipramine with VEGF pathway inhibitors orchestrates the infiltration and activation of CD8 and CD4 T cells, producing significant therapeutic benefit in several GBM mouse models. Inclusion up front of immune-checkpoint blockade with anti-programmed death-ligand 1 (PD-L1) in eventually relapsing tumors markedly extends survival benefit. The results illustrate the potential of mechanism-guided therapeutic co-targeting of disparate biological vulnerabilities in the tumor microenvironment.

Hallmarks of Cancer: New Dimensions

The hallmarks of cancer conceptualization is a heuristic tool for distilling the vast complexity of cancer phenotypes and genotypes into a provisional set of underlying principles. As knowledge of cancer mechanisms has progressed, other facets of the disease have emerged as potential refinements. Herein, the prospect is raised that phenotypic plasticity and disrupted differentiation is a discrete hallmark capability, and that nonmutational epigenetic reprogramming and polymorphic microbiomes both constitute distinctive enabling characteristics that facilitate the acquisition of hallmark capabilities. Additionally, senescent cells, of varying origins, may be added to the roster of functionally important cell types in the tumor microenvironment. SIGNIFICANCE: Cancer is daunting in the breadth and scope of its diversity, spanning genetics, cell and tissue biology, pathology, and response to therapy. Ever more powerful experimental and computational tools and technologies are providing an avalanche of "big data" about the myriad manifestations of the diseases that cancer encompasses. The integrative concept embodied in the hallmarks of cancer is helping to distill this complexity into an increasingly logical science, and the provisional new dimensions presented in this perspective may add value to that endeavor, to more fully understand mechanisms of cancer development and malignant progression, and apply that knowledge to cancer medicine.

Cancer Cells Retrace a Stepwise Differentiation Program during Malignant Progression

Pancreatic neuroendocrine tumors (PanNET) comprise two molecular subtypes, relatively benign islet tumors (IT) and invasive, metastasis-like primary (MLP) tumors. Until now, the origin of aggressive MLP tumors has been obscure. Herein, using multi-omics approaches, we revealed that MLP tumors arise from IT via dedifferentiation following a reverse trajectory along the developmental pathway of islet β cells, which results in the acquisition of a progenitor-like molecular phenotype. Functionally, the miR-181cd cluster induces the IT-to-MLP transition by suppressing expression of the Meis2 transcription factor, leading to upregulation of a developmental transcription factor, Hmgb3. Notably, the IT-to-MLP transition constitutes a distinct step of tumorigenesis and is separable from the classic proliferation-associated hallmark, temporally preceding accelerated proliferation of cancer cells. Furthermore, patients with PanNET with elevated HMGB3 expression and an MLP transcriptional signature are associated with higher-grade tumors and worse survival. Overall, our results unveil a new mechanism that modulates cancer cell plasticity to enable malignant progression. SIGNIFICANCE: Dedifferentiation has long been observed as a histopathologic characteristic of many cancers, albeit inseparable from concurrent increases in cell proliferation. Herein, we demonstrate that dedifferentiation is a mechanistically and temporally separable step in the multistage tumorigenesis of pancreatic islet cells, retracing the developmental lineage of islet β cells.This article is highlighted in the In This Issue feature, p. 2355.

The Porto European Cancer Research Summit 2021

Key stakeholders from the cancer research continuum met in May 2021 at the European Cancer Research Summit in Porto to discuss priorities and specific action points required for the successful implementation of the European Cancer Mission and Europe's Beating Cancer Plan (EBCP). Speakers presented a unified view about the need to establish high-quality, networked infrastructures to decrease cancer incidence, increase the cure rate, improve patient's survival and quality of life, and deal with research and care inequalities across the European Union (EU). These infrastructures, featuring Comprehensive Cancer Centres (CCCs) as key components, will integrate care, prevention and research across the entire cancer continuum to support the development of personalized/precision cancer medicine in Europe. The three pillars of the recommended European infrastructures - namely translational research, clinical/prevention trials and outcomes research - were pondered at length. Speakers addressing the future needs of translational research focused on the prospects of multiomics assisted preclinical research, progress in Molecular and Digital Pathology, immunotherapy, liquid biopsy and science data. The clinical/prevention trial session presented the requirements for next-generation, multicentric trials entailing unified strategies for patient stratification, imaging, and biospecimen acquisition and storage. The third session highlighted the need for establishing outcomes research infrastructures to cover primary prevention, early detection, clinical effectiveness of innovations, health-related quality-of-life assessment, survivorship research and health economics. An important outcome of the Summit was the presentation of the Porto Declaration, which called for a collective and committed action throughout Europe to develop the cancer research infrastructures indispensable for fostering innovation and decreasing inequalities within and between member states. Moreover, the Summit guidelines will assist decision making in the context of a unique EU-wide cancer initiative that, if expertly implemented, will decrease the cancer death toll and improve the quality of life of those confronted with cancer, and this is carried out at an affordable cost.

Abstract 1652: Co-targeting distinct hallmark capabilities for therapeutic benefit in pre-clinical GBM models

Glioblastoma (GBM) is the most common primary tumor arising in the central nervous system (CNS). The currently approved standard of care has transient clinical benefit as GBM tends to be exceedingly aggressive. Despite pronounced efforts to identify novel therapies, curative options for GBM do not exist and the survival rate of diagnosed patients is very low. Therefore, there is an urgent need for new treatment strategies, and one approach would be to co-target and thereby disrupt distinct hallmarks of cancer, aiming to elicit sustained therapeutic responses. We have assessed this concept by combining a tricyclic antidepressant -imipramine - with drugs targeting VEGF-A ligand or VEGF-Receptor in mice bearing de novo GBM. All monotherapies were ineffective. In notable contradistinction, we found that combinatorial regimens significantly increased survival benefit and regressed established tumors. Investigation of the basis for the therapeutic efficacy revealed that combining the VEGF pathway inhibitor with imipramine hyperactivated autophagy to the level of eliciting cancer cell-intrinsic autophagy-associated cell death, whilst modifying the tumor vasculature to be more normal-like. In addition, imipramine downregulated an M2-like phenotype of tumor-associated macrophages and reprogramed them to express chemokines attracting otherwise rare CD8 T cells, which were demonstrably contributing to the observed efficacy. As such, these hallmark co-targeting combinations served to reprogram the GBM microenvironment from immunosuppressive to pro-inflammatory, thereby sensitizing the tumors to immune checkpoint blockade, as evidenced by enhanced responses when an anti-PD-L1 therapy was included in the mix. The results to be presented will elaborate a provocative new therapeutic approach for glioblastoma that has prospect to motivate clinical evaluation in this daunting form of human cancer.

Citation Format: Agnieszka Chryplewicz, Douglas Hanahan. Co-targeting distinct hallmark capabilities for therapeutic benefit in pre-clinical GBM models [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 1652.

Abstract 71: The immunocytokine PD1-IL2v overcomes immune checkpoint resistance, and combination with an anti-PD-L1 antibody further enhances its anti-tumor activity

Cancer immunotherapies have shown therapeutic benefits in the clinic, but treatments involving immuno-stimulatory agents such as interleukin 2 (IL-2) are typically accompanied by severe adverse events. One strategy to limit the systemic toxicity of IL-2 is to target it specifically to the tumor microenvironment. Here we evaluated the therapeutic efficacy of the bi-specific immunocytokine PD1-IL2v in the genetically engineered, spontaneous RIP1-Tag5 (RT5) mouse model of pancreatic neuroendocrine tumors (PanNETs). PD1-IL2v is a bi-specific molecule based on a bivalent PD-1 antibody to which a single IL2 variant (IL2v) is fused. PD-1 serves as a targeting moiety to deliver IL2v in cis to PD-1-positive T cells located in the immune tumor microenvironment, and IL2v has been engineered to lack binding to CD25 in order to selectively expand effector T cells but not immuno-suppressive regulatory T cells (Tregs). Although RT5 mice are capable of mounting an adaptive immune response against the tumor-driving oncoprotein, PanNETs developing in RT5 are resistant to immune checkpoint inhibitors. In comparing the untargeted version of IL2v combined with an anti-PD-1 antibody vs. the PD-1 targeted immunocytokine PD1-IL2v, we found that PD1-IL2v, but not the mixture, produced significant anti-tumor activity. PD1-IL2v treatment resulted in a substantial infiltration of CD8+ T cells into the pancreatic islet tumors, which in the context of sustained treatment with PD1-IL2v resulted in tumor regression. Interestingly, following tumor shrinkage, the PanNETs appeared to stabilize and eventually relapsed. Notably, we identified up-regulation of PD-L1 on the tumor vasculature in relapsing tumors as a potential factor in the observed adaptive resistance, which encouraged combining an anti-PD-L1 antibody with PD1-IL2v, leading to enhanced therapeutic benefit. The data obtained in this spontaneous de novo tumor model motivate consideration of evaluating the PD1-IL2v/anti-PD-L1 combination therapy in the clinical setting, in particular in anti-PD-1/anti-PD-L1 resistant tumors infiltrated with PD1+CD8+ T cells.

Citation Format: Stephan Wullschleger, Mélanie Tichet, Laura Codarri-Deak, Pablo Umana, Christian Klein, Douglas Hanahan. The immunocytokine PD1-IL2v overcomes immune checkpoint resistance, and combination with an anti-PD-L1 antibody further enhances its anti-tumor activity [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 71.

Towards a cancer mission in Horizon Europe: recommendations

A comprehensive translational cancer research approach focused on personalized and precision medicine, and covering the entire cancer research-care-prevention continuum has the potential to achieve in 2030 a 10-year cancer-specific survival for 75% of patients diagnosed in European Union (EU) member states with a well-developed healthcare system. Concerted actions across this continuum that spans from basic and preclinical research through clinical and prevention research to outcomes research, along with the establishment of interconnected high-quality infrastructures for translational research, clinical and prevention trials and outcomes research, will ensure that science-driven and social innovations benefit patients and individuals at risk across the EU. European infrastructures involving comprehensive cancer centres (CCCs) and CCC-like entities will provide researchers with access to the required critical mass of patients, biological materials and technological resources and can bridge research with healthcare systems. Here, we prioritize research areas to ensure a balanced research portfolio and provide recommendations for achieving key targets. Meeting these targets will require harmonization of EU and national priorities and policies, improved research coordination at the national, regional and EU level and increasingly efficient and flexible funding mechanisms. Long-term support by the EU and commitment of Member States to specialized schemes are also needed for the establishment and sustainability of trans-border infrastructures and networks. In addition to effectively engaging policymakers, all relevant stakeholders within the entire continuum should consensually inform policy through evidence-based advice.

Roadmap for the Emerging Field of Cancer Neuroscience

Mounting evidence indicates that the nervous system plays a central role in cancer pathogenesis. In turn, cancers and cancer therapies can alter nervous system form and function. This Commentary seeks to describe the burgeoning field of "cancer neuroscience" and encourage multidisciplinary collaboration for the study of cancer-nervous system interactions.

ALK7 Signaling Manifests a Homeostatic Tissue Barrier That Is Abrogated during Tumorigenesis and Metastasis

Herein, we report that the TGFß superfamily receptor ALK7 is a suppressor of tumorigenesis and metastasis, as revealed by functional studies in mouse models of pancreatic neuroendocrine and luminal breast cancer, complemented by experimental metastasis assays. Activation in neoplastic cells of the ALK7 signaling pathway by its principal ligand activin B induces apoptosis. During tumorigenesis, cancer cells use two different approaches to evade this barrier, either downregulating activin B and/or downregulating ALK7. Suppressing ALK7 expression additionally contributes to the capability for metastatic seeding. ALK7 is associated with shorter relapse-free survival of various human cancers and distant-metastasis-free survival of breast cancer patients. This study introduces mechanistic insights into primary and metastatic tumor development, in the form of a protective barrier that triggers apoptosis in cells that are not "authorized" to proliferate within a particular tissue, by virtue of those cells expressing ALK7 in a tissue microenvironment bathed in its ligand.

Myeloid Cells Orchestrate Systemic Immunosuppression, Impairing the Efficacy of Immunotherapy against HPV+ Cancers

Cancers induced by human papillomaviruses (HPV) should be responsive to immunotherapy by virtue of expressing the immunogenic oncoproteins E6/E7. However, advanced forms of cervical cancer, driven by HPV, are poorly responsive to immune response-enhancing treatments involving therapeutic vaccination against these viral neoantigens. Leveraging a transgenic mouse model of HPV-derived cancers, K14HPV16/H2b, we demonstrated that a potent nanoparticle-based E7 vaccine, but not a conventional "liquid" vaccine, induced E7 tumor antigen-specific CD8+ T cells in cervical tumor-bearing mice. Vaccination alone or in combination with anti-PD-1/anti-CTLA4 did not elicit tumor regression nor increase CD8+ T cells in the tumor microenvironment (TME), suggesting the presence of immune-suppressive barriers. Patients with cervical cancer have poor dendritic cell functions, have weak cytotoxic lymphocyte responses, and demonstrate an accumulation of myeloid cells in the periphery. Here, we illustrated that myeloid cells in K14HPV16/H2b mice possess potent immunosuppressive activity toward antigen-presenting cells and CD8+ T cells, dampening antitumor immunity. These immune-inhibitory effects inhibited synergistic effects of combining our oncoprotein vaccine with immune checkpoint-blocking antibodies. Our data highlighted a link between HPV-induced cancers, systemic amplification of myeloid cells, and the detrimental effects of myeloid cells on CD8+ T-cell activation and recruitment into the TME. These results established immunosuppressive myeloid cells in lymphoid organs as an HPV+ cancer-induced means of circumventing tumor immunity that will require targeted abrogation to enable the induction of efficacious antitumor immune responses.

Carboplatin/paclitaxel, E7-vaccination and intravaginal CpG as tri-therapy towards efficient regression of genital HPV16 tumors

High-risk human papillomavirus (HPV) are responsible for genital and oral cancers associated with the expression of the E6/E7 HPV oncogenes. Therapeutic vaccines targeting those oncogenes can only partially control tumor progression, highlighting the necessity to investigate different treatment strategies. Using the genital orthotopic HPV16 TC-1 model, herein we sequentially investigated in progressively more stringent settings the effects of systemic administration of carboplatin/paclitaxel (C + P) chemotherapy combined with HPV16-E7 synthetic long peptide (E7LP) vaccination, followed by intravaginal immunostimulation with the synthetic toll-like-receptor-9 agonist CpG. Our data show that systemic delivery of C + P prior to E7LP vaccination significantly increased mice survival. This survival benefit was associated with both reduced genital tumor growth at the time of vaccination, and a decreased infiltration of Ly6G myeloid cells and tumor-associated macrophages. Adding intravaginal CpG, which results in increased E7-specific CD8 T cells locally, to E7LP vaccination and the chemotherapy formed a tri-therapy, which significantly increased mice survival as compared to any of the dual treatments. When the tri-therapy was further refined by using a recently optimized nanoparticle-conjugated E7LP vaccine, even larger end-stage genital-TC-1 tumors responded, with 90% of mice showing a survival benefit as compared to 30% of mice with the tri-therapy involving the traditional E7LP ‘liquid’ vaccine. C + P is commonly used to treat cervical cancer patients and its combination with E7/E6 vaccination is currently being tested in a phase I/II trial (NCT02128126). Our data suggests that new vaccine formulations combined with local immunostimulation and standard-of-care chemotherapy have promise to further benefit patients with HPV-associated cancer.

Nanoparticle Conjugation of Human Papillomavirus 16 E7-long Peptides Enhances Therapeutic Vaccine Efficacy against Solid Tumors in Mice

Treatment of patients bearing human papillomavirus (HPV)-related cancers with synthetic long-peptide (SLP) therapeutic vaccines has shown promising results in clinical trials against premalignant lesions, whereas responses against later stage carcinomas have remained elusive. We show that conjugation of a well-documented HPV-E7 SLP to ultra-small polymeric nanoparticles (NP) enhances the antitumor efficacy of therapeutic vaccination in different mouse models of HPV⁺ cancers. Immunization of TC-1 tumor-bearing mice with a single dose of NP-conjugated E7LP (NP-E7LP) generated a larger pool of E7-specific CD8⁺ T cells with increased effector functions than unconjugated free E7LP. At the tumor site, NP-E7LP prompted a robust infiltration of CD8⁺ T cells that was not accompanied by concomitant accumulation of regulatory T cells (Tregs), resulting in a higher CD8⁺ T-cell to Treg ratio. Consequently, the amplified immune response elicited by the NP-E7LP formulation led to increased regression of large, well-established tumors, resulting in a significant percentage of complete responses that were not achievable by immunizing with the non-NP-conjugated long-peptide. The partial responses were characterized by distinct phases of regression, stable disease, and relapse to progressive growth, establishing a platform to investigate adaptive resistance mechanisms. The efficacy of NP-E7LP could be further improved by therapeutic activation of the costimulatory receptor 4-1BB. This NP-E7LP formulation illustrates a "solid-phase" antigen delivery strategy that is more effective than a conventional free-peptide ("liquid") vaccine, further highlighting the potential of using such formulations for therapeutic vaccination against solid tumors. Cancer Immunol Res; 6(11); 1301-13. ©2018 AACR.

Tumor lymphangiogenesis promotes T cell infiltration and potentiates immunotherapy in melanoma

In melanoma, vascular endothelial growth factor-C (VEGF-C) expression and consequent lymphangiogenesis correlate with metastasis and poor prognosis. VEGF-C also promotes tumor immunosuppression, suggesting that lymphangiogenesis inhibitors may be clinically useful in combination with immunotherapy. We addressed this concept in mouse melanoma models with VEGF receptor-3 (VEGFR-3)-blocking antibodies and unexpectedly found that VEGF-C signaling enhanced rather than suppressed the response to immunotherapy. We further found that this effect was mediated by VEGF-C-induced CCL21 and tumor infiltration of naïve T cells before immunotherapy because CCR7 blockade reversed the potentiating effects of VEGF-C. In human metastatic melanoma, gene expression of VEGF-C strongly correlated with CCL21 and T cell inflammation, and serum VEGF-C concentrations associated with both T cell activation and expansion after peptide vaccination and clinical response to checkpoint blockade. We propose that VEGF-C potentiates immunotherapy by attracting naïve T cells, which are locally activated upon immunotherapy-induced tumor cell killing, and that serum VEGF-C may serve as a predictive biomarker for immunotherapy response.

GKAP Acts as a Genetic Modulator of NMDAR Signaling to Govern Invasive Tumor Growth

Genetic linkage analysis previously suggested that GKAP, a scaffold protein of the N-methyl-D-aspartate receptor (NMDAR), was a potential modifier of invasion in a mouse model of pancreatic neuroendocrine tumor (PanNET). Here, we establish that GKAP governs invasive growth and treatment response to NMDAR inhibitors of PanNET via its pivotal role in regulating NMDAR pathway activity. Combining genetic knockdown of GKAP and pharmacological inhibition of NMDAR, we implicate as downstream effectors FMRP and HSF1, which along with GKAP demonstrably support invasiveness of PanNET and pancreatic ductal adenocarcinoma cancer cells. Furthermore, we distilled genome-wide expression profiles orchestrated by the NMDAR-GKAP signaling axis, identifying transcriptome signatures in tumors with low/inhibited NMDAR activity that significantly associate with favorable patient prognosis in several cancer types.

Combined antiangiogenic and anti-PD-L1 therapy stimulates tumor immunity through HEV formation

Inhibitors of VEGF (vascular endothelial growth factor)/VEGFR2 (vascular endothelial growth factor receptor 2) are commonly used in the clinic, but their beneficial effects are only observed in a subset of patients and limited by induction of diverse relapse mechanisms. We describe the up-regulation of an adaptive immunosuppressive pathway during antiangiogenic therapy, by which PD-L1 (programmed cell death ligand 1), the ligand of the negative immune checkpoint regulator PD-1 (programmed cell death protein 1), is enhanced by interferon-γ-expressing T cells in distinct intratumoral cell types in refractory pancreatic, breast, and brain tumor mouse models. Successful treatment with a combination of anti-VEGFR2 and anti-PD-L1 antibodies induced high endothelial venules (HEVs) in PyMT (polyoma middle T oncoprotein) breast cancer and RT2-PNET (Rip1-Tag2 pancreatic neuroendocrine tumors), but not in glioblastoma (GBM). These HEVs promoted lymphocyte infiltration and activity through activation of lymphotoxin β receptor (LTβR) signaling. Further activation of LTβR signaling in tumor vessels using an agonistic antibody enhanced HEV formation, immunity, and subsequent apoptosis and necrosis in pancreatic and mammary tumors. Finally, LTβR agonists induced HEVs in recalcitrant GBM, enhanced cytotoxic T cell (CTL) activity, and thereby sensitized tumors to antiangiogenic/anti-PD-L1 therapy. Together, our preclinical studies provide evidence that anti-PD-L1 therapy can sensitize tumors to antiangiogenic therapy and prolong its efficacy, and conversely, antiangiogenic therapy can improve anti-PD-L1 treatment specifically when it generates intratumoral HEVs that facilitate enhanced CTL infiltration, activity, and tumor cell destruction.

Exploratory analysis of multiprotein serum predictors at baseline of progression-free survival of ipilimumab or ipilimumab and nivolumab in the Checkmate-069 study

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Background: Checkpoint inhibitors have revolutionized the treatment of stage IV melanoma patients. Selection of patients for PD-1 monotherapy or CTLA4/PD1 combination remains an important challenge. We set out to perform a discovery study of pretreatment serum protein biomarkers to identify predictors of progression free survival (PFS) for ipilimumab (IPI) or ipilimumab/nivolumab (IPI/NIVO). Methods: We performed an exploratory analysis of baseline serum samples from 135 treatment-naive patients with metastatic melanoma included in the randomized phase II clinical trial, CheckMate 069 (NCT01927419). We used the RayBiotech 440 human cytokine array and evaluated the relationship of serum protein levels with 44 clinical parameters. R, Prism 7.0 and TensorFlow were used for analyses. Results: We focused on correlation of serum protein markers with PFS as a predictor of long-term benefit. In the IPI arm (n = 46), high FGF4 correlated with worse PFS outcome (p = 0.0012). However, FGF4 levels alone were unable to select responsive vs. non-responsive patients. In contrast, a set of three markers consisting of FGF4 ( < 760pg/ml), CCL15 ( > 2.7 ng/ml), and TACE ( > 600pg/ml) separated non-progressing versus progressing patients. Moreover a small group of FGF4-high patients who were concomitantly TIM-3-low also had longer PFS (combined of both: p = 0.0004, HRlogrank: 0.07, 95% CI: 0.03279 to 0.1533). The same markers did not discriminate between IPI/NIVO patients (p = 0.467, HR: 15). In the IPI/NIVO arm, three different markers could select patients. Patients either with low CCL2 ( < 72 pg/ml) or alternatively with high CCL2 combined with high PDGF-AA ( > 8.2 ng/ml) and low GASP-1 ( < 1.3 ng/ml) had longer PFS (p < 0.0001, HR: 0.115, 95% CI: 0.03848 to 0.3408). Conversely, these markers did not predict benefit for IPI-monotherapy. Conclusions: In this study we identified protein signatures in baseline serum that correlate with PFS for therapies with IPI or IPI/NIVO. The markers were exclusive for IPI or IPI/NIVO but not for both. Additional research is warranted to substantiate these results and evaluate the possibility of incorporating into clinical practice.

Procathepsin E is highly abundant but minimally active in pancreatic ductal adenocarcinoma tumors

The cathepsin family of lysosomal proteases is increasingly being recognized for their altered expression in cancer and role in facilitating tumor progression. The aspartyl protease cathepsin E is overexpressed in several cancers and has been investigated as a biomarker for pancreatic ductal adenocarcinoma (PDAC). Here we show that cathepsin E expression in mouse PDAC tumors is increased by more than 400-fold when compared to healthy pancreatic tissue. Cathepsin E accumulates over the course of disease progression and accounts for more than 3% of the tumor protein in mice with end-stage disease. Through immunoblot analysis we determined that only procathepsin E exists in mouse PDAC tumors and cell lines derived from these tumors. By decreasing the pH, this procathepsion E is converted to the mature form, resulting in an increase in proteolytic activity. Although active site inhibitors can bind procathepsin E, treatment of PDAC mice with the aspartyl protease inhibitor ritonavir did not decrease tumor burden. Lastly, we used multiplex substrate profiling by mass spectrometry to identify two synthetic peptides that are hydrolyzed by procathepsin E near neutral pH. This work represents a comprehensive analysis of procathepsin E in PDAC and could facilitate the development of improved biomarkers for disease detection.

Abstract 1907: Multi-step microRNA control of pancreatic neuroendocrine tumors metastatic cascade

MicroRNAs (miRs) are implicated in the pathogenesis of various malignancies, including pancreatic cancer, and may represent key players in the metastatic process. In a previous study (Olson et al., 2009), we identified two unique miR signatures associated with tumour metastasis in the mouse model of pancreatic neuroendocrine tumour (PNET), RIP-Tag2. The first signature was characteristic of rare liver metastases. Intriguingly, the second signature, identified in a subset of primary PNET, had overlap with the liver metastasis signature. This signature was denoted “met-like primary” (referred to as MLP-miRs). Bioinformatic analysis revealed that three MLP-miRs (miR-181, miR-137, and miR-132), as well as three metastasis-specific miRs (miR-23b, miR-27b, and miR-24-1) are also upregulated in human PNET MLP samples.

To examine the potential pro-metastatic role of the aforementioned miRs, we generated PNET cancer cell lines (β-TC) that stably express single miRs or combinations. We first audited their effect using orthotopic studies. MiR-181 caused a significant delay in the tumor progression, while the rest of the miRs did not affect tumor growth. Notably, the orthotopic tumors overexpressing miR-137 and miR-132 were characterized by markedly enhanced invasion into adjacent normal tissue. Then, using experimental metastasis assays we examined potential roles in distant metastasis. Overexpression of the miR-23b cluster (miR-23b, -27b and -24-1) caused a dramatic increase in the number of liver metastatic foci, indicating that they play a significant role in seeding distant metastases. The aforementioned pro-invasive miRs had little activity in this assay. Using an inducible system we went on to demonstrate that the three miRs comprising the 23b cluster act together in a synergistic manner during the early stages of distant colonization.

Transcriptome analysis of miRNA isolated from β-TC expressing cell lines revealed enrichment of genes involved in axonal guidance, actin nucleation and integrin signaling in the case of miR-137, and of glutamate receptor signaling and EMT in the case of miR-23b cluster.

Overall, our results suggest a multi-step miRNA control of the PNET metastatic cascade, during which miR-137 and miR-132 enables PNET cancer cells to invade,, while the miR-23b cluster plays an important role in distant metastasis. Using miR gene target prediction algorithms applied to mouse and human PNET transcriptome datasets, we are in the process of identifying and validating possible effector genes involved in distinctive aspects of the invasion-metastasis cascade, potentially guiding the design of new therapeutic strategies to target metastasis.

Citation Format: Iacovos P. Michael, Douglas Hanahan. Multi-step microRNA control of pancreatic neuroendocrine tumors metastatic cascade. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1907.

Metabolic Symbiosis Enables Adaptive Resistance to Anti-angiogenic Therapy that Is Dependent on mTOR Signaling

Therapeutic targeting of tumor angiogenesis with VEGF inhibitors results in demonstrable, but transitory efficacy in certain human tumors and mouse models of cancer, limited by unconventional forms of adaptive/evasive resistance. In one such mouse model, potent angiogenesis inhibitors elicit compartmental reorganization of cancer cells around remaining blood vessels. The glucose and lactate transporters GLUT1 and MCT4 are induced in distal hypoxic cells in a HIF1α-dependent fashion, indicative of glycolysis. Tumor cells proximal to blood vessels instead express the lactate transporter MCT1, and p-S6, the latter reflecting mTOR signaling. Normoxic cancer cells import and metabolize lactate, resulting in upregulation of mTOR signaling via glutamine metabolism enhanced by lactate catabolism. Thus, metabolic symbiosis is established in the face of angiogenesis inhibition, whereby hypoxic cancer cells import glucose and export lactate, while normoxic cells import and catabolize lactate. mTOR signaling inhibition disrupts this metabolic symbiosis, associated with upregulation of the glucose transporter GLUT2.

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Angiogenesis inhibitors causing acute hypoxia elicit metabolic compartmentalization

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Hypoxic cancer cells import and metabolize glucose, secreting lactate

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Normoxic vessel-proximal cancer cells import and metabolize lactate, involving mTOR

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Co-inhibiting mTOR disrupts the metabolic symbiosis

Bruton Tyrosine Kinase-Dependent Immune Cell Cross-talk Drives Pancreas Cancer

Pancreas ductal adenocarcinoma (PDAC) has one of the worst 5-year survival rates of all solid tumors, and thus new treatment strategies are urgently needed. Here, we report that targeting Bruton tyrosine kinase (BTK), a key B-cell and macrophage kinase, restores T cell-dependent antitumor immune responses, thereby inhibiting PDAC growth and improving responsiveness to standard-of-care chemotherapy. We report that PDAC tumor growth depends on cross-talk between B cells and FcRγ(+) tumor-associated macrophages, resulting in T(H)2-type macrophage programming via BTK activation in a PI3Kγ-dependent manner. Treatment of PDAC-bearing mice with the BTK inhibitor PCI32765 (ibrutinib) or by PI3Kγ inhibition reprogrammed macrophages toward a T(H)1 phenotype that fostered CD8(+) T-cell cytotoxicity, and suppressed PDAC growth, indicating that BTK signaling mediates PDAC immunosuppression. These data indicate that pharmacologic inhibition of BTK in PDAC can reactivate adaptive immune responses, presenting a new therapeutic modality for this devastating tumor type.

SIGNIFICANCE

We report that BTK regulates B-cell and macrophage-mediated T-cell suppression in pancreas adenocarcinomas. Inhibition of BTK with the FDA-approved inhibitor ibrutinib restores T cell-dependent antitumor immune responses to inhibit PDAC growth and improves responsiveness to chemotherapy, presenting a new therapeutic modality for pancreas cancer.

The consensus molecular subtypes of colorectal cancer

Colorectal cancer (CRC) is a frequently lethal disease with heterogeneous outcomes and drug responses. To resolve inconsistencies among the reported gene expression-based CRC classifications and facilitate clinical translation, we formed an international consortium dedicated to large-scale data sharing and analytics across expert groups. We show marked interconnectivity between six independent classification systems coalescing into four consensus molecular subtypes (CMSs) with distinguishing features: CMS1 (microsatellite instability immune, 14%), hypermutated, microsatellite unstable and strong immune activation; CMS2 (canonical, 37%), epithelial, marked WNT and MYC signaling activation; CMS3 (metabolic, 13%), epithelial and evident metabolic dysregulation; and CMS4 (mesenchymal, 23%), prominent transforming growth factor-β activation, stromal invasion and angiogenesis. Samples with mixed features (13%) possibly represent a transition phenotype or intratumoral heterogeneity. We consider the CMS groups the most robust classification system currently available for CRC-with clear biological interpretability-and the basis for future clinical stratification and subtype-based targeted interventions.

Dual Targeting of the Autophagic Regulatory Circuitry in Gliomas with Repurposed Drugs Elicits Cell-Lethal Autophagy and Therapeutic Benefit

The associations of tricyclic antidepressants (TCAs) with reduced incidence of gliomas and elevated autophagy in glioma cells motivated investigation in mouse models of gliomagenesis. First, we established that imipramine, a TCA, increased autophagy and conveyed modest therapeutic benefit in tumor-bearing animals. Then we screened clinically approved agents suggested to affect autophagy for their ability to enhance imipramine-induced autophagy-associated cell death. The anticoagulant ticlopidine, which inhibits the purinergic receptor P2Y12, potentiated imipramine, elevating cAMP, a modulator of autophagy, reducing cell viability in culture, and increasing survival in glioma-bearing mice. Efficacy of the combination was obviated by knockdown of the autophagic regulatory gene ATG7, implicating cell-lethal autophagy. This seemingly innocuous combination of TCAs and P2Y12 inhibitors may have applicability for treating glioma.

A Cross-Species Analysis in Pancreatic Neuroendocrine Tumors Reveals Molecular Subtypes with Distinctive Clinical, Metastatic, Developmental, and Metabolic Characteristics

Seeking to assess the representative and instructive value of an engineered mouse model of pancreatic neuroendocrine tumors (PanNET) for its cognate human cancer, we profiled and compared mRNA and miRNA transcriptomes of tumors from both. Mouse PanNET tumors could be classified into two distinctive subtypes, well-differentiated islet/insulinoma tumors (IT) and poorly differentiated tumors associated with liver metastases, dubbed metastasis-like primary (MLP). Human PanNETs were independently classified into these same two subtypes, along with a third, specific gene mutation-enriched subtype. The MLP subtypes in human and mouse were similar to liver metastases in terms of miRNA and mRNA transcriptome profiles and signature genes. The human/mouse MLP subtypes also similarly expressed genes known to regulate early pancreas development, whereas the IT subtypes expressed genes characteristic of mature islet cells, suggesting different tumorigenesis pathways. In addition, these subtypes exhibit distinct metabolic profiles marked by differential pyruvate metabolism, substantiating the significance of their separate identities.

SIGNIFICANCE

This study involves a comprehensive cross-species integrated analysis of multi-omics profiles and histology to stratify PanNETs into subtypes with distinctive characteristics. We provide support for the RIP1-TAG2 mouse model as representative of its cognate human cancer with prospects to better understand PanNET heterogeneity and consider future applications of personalized cancer therapy.

Deficiency for the cysteine protease cathepsin L impairs Myc-induced tumorigenesis in a mouse model of pancreatic neuroendocrine cancer

Motivated by the recent implication of cysteine protease cathepsin L as a potential target for anti-cancer drug development, we used a conditional MycERTAM;Bcl-xL model of pancreatic neuroendocrine tumorigenesis (PNET) to assess the role of cathepsin L in Myc-induced tumor progression. By employing a cysteine cathepsin activity probe in vivo and in vitro, we first established that cathepsin activity increases during the initial stages of MycERTAM;Bcl-xL tumor development. Among the cathepsin family members investigated, only cathepsin L was predominately produced by beta-tumor cells in neoplastic pancreata and, consistent with this, cathepsin L mRNA expression was rapidly upregulated following Myc activation in the beta cell compartment. By contrast, cathepsins B, S and C were highly enriched in tumor-infiltrating leukocytes. Genetic deletion of cathepsin L had no discernible effect on the initiation of neoplastic growth or concordant angiogenesis. However, the tumors that developed in the cathepsin L-deficient background were markedly reduced in size relative to their typical wild-type counterparts, indicative of a role for cathepsin L in enabling expansive tumor growth. Thus, genetic blockade of cathepsin L activity is inferred to retard Myc-driven tumor growth, encouraging the potential utility of pharmacological inhibitors of cysteine cathepsins in treating late stage tumors.

Rethinking the war on cancer

Some 40 years ago a metaphor was posed that cancer was such an insidious adversary that a declaration of war on the disease was justified. Although this statement was a useful inspiration for enlistment of resources, despite extraordinary progress in our understanding of disease pathogenesis, in most cases and for most forms of cancer this war has not been won. A second metaphor was about magic bullets--targeted therapies based on knowledge of mechanisms that were envisaged to strike with devastating consequences for the disease. The reality, however, is that targeted therapies are generally not curative or even enduringly effective, because of the adaptive and evasive resistance strategies developed by cancers under attack. In this Series paper, I suggest that, much like in modern warfare, the war on cancer needs to have a battlespace vision.

Reconciliation of classification systems defining molecular subtypes of colorectal cancer: interrelationships and clinical implications

Recently we published two independent studies describing novel gene expression-based classifications of colorectal cancer (CRC). Notably, each study stratified CRC into a different number of subtypes: one reported 3 subtypes, whereas the second highlighted 5. Given that each ascribed clinical significance, distinctive biology, and therapeutic prognosis to the different subtypes, we sought to reconcile this apparent incongruity in subtype stratification of CRC, and to interrelate the results. To do so, we each evaluated the other's data sets and analytical methods and discovered that the subtypes and their classifiers are, in fact, clearly related to each other; indeed, the 5 subtype outcomes can be coalesced into the same three. In addition to presenting this clarification, we briefly discuss how both classification methods can be viewed within the broader literature on CRC subtypes, and potentially applied.

A new twist on radiation oncology: low-dose irradiation elicits immunostimulatory macrophages that unlock barriers to tumor immunotherapy

Tumor-infiltrating macrophages typically promote angiogenesis while suppressing antitumoral T cell responses. In this issue of Cancer Cell, Klug and colleagues report that clinically-feasible, low-dose irradiation redirects macrophage differentiation from a tumor-promoting/immunosuppressive state to one that enables cytotoxic T cells to infiltrate tumors and kill cancer cells, rendering immunotherapy successful in mice.

Transformation-associated changes in sphingolipid metabolism sensitize cells to lysosomal cell death induced by inhibitors of acid sphingomyelinase

Lysosomal membrane permeabilization and subsequent cell death may prove useful in cancer treatment, provided that cancer cell lysosomes can be specifically targeted. Here, we identify acid sphingomyelinase (ASM) inhibition as a selective means to destabilize cancer cell lysosomes. Lysosome-destabilizing experimental anticancer agent siramesine inhibits ASM by interfering with the binding of ASM to its essential lysosomal cofactor, bis(monoacylglycero)phosphate. Like siramesine, several clinically relevant ASM inhibitors trigger cancer-specific lysosomal cell death, reduce tumor growth in vivo, and revert multidrug resistance. Their cancer selectivity is associated with transformation-associated reduction in ASM expression and subsequent failure to maintain sphingomyelin hydrolysis during drug exposure. Taken together, these data identify ASM as an attractive target for cancer therapy.

A biocompatible in vivo ligation reaction and its application for noninvasive bioluminescent imaging of protease activity in living mice

The discovery of biocompatible reactions had a tremendous impact on chemical biology, allowing the study of numerous biological processes directly in complex systems. However, despite the fact that multiple biocompatible reactions have been developed in the past decade, very few work well in living mice. Here we report that D-cysteine and 2-cyanobenzothiazoles can selectively react with each other in vivo to generate a luciferin substrate for firefly luciferase. The success of this "split luciferin" ligation reaction has important implications for both in vivo imaging and biocompatible labeling strategies. First, the production of a luciferin substrate can be visualized in a live mouse by bioluminescence imaging (BLI) and furthermore allows interrogation of targeted tissues using a "caged" luciferin approach. We therefore applied this reaction to the real-time noninvasive imaging of apoptosis associated with caspase 3/7. Caspase-dependent release of free D-cysteine from the caspase 3/7 peptide substrate Asp-Glu-Val-Asp-D-Cys (DEVD-(D-Cys)) allowed selective reaction with 6-amino-2-cyanobenzothiazole (NH(2)-CBT) in vivo to form 6-amino-D-luciferin with subsequent light emission from luciferase. Importantly, this strategy was found to be superior to the commercially available DEVD-aminoluciferin substrate for imaging of caspase 3/7 activity. Moreover, the split luciferin approach enables the modular construction of bioluminogenic sensors, where either or both reaction partners could be caged to report on multiple biological events. Lastly, the luciferin ligation reaction is 3 orders of magnitude faster than Staudinger ligation, suggesting further applications for both bioluminescence and specific molecular targeting in vivo.

Abstract SY18-02: Molecular genetic subtypes of pancreas and colon cancer: Phenotypes and potential therapeutic significance

Pancreatic neuroendocrine tumors (PNETs) are relatively uncommon but nevertheless a serious, often fatal disease. While the prognosis of functional PNETs (secreting one or more hormones such as insulin at detectable levels in blood) is better, non-functional PNETs (NF; no hormones secreted) often present late with metastasis, and hence their prognosis is poor, with an overall 5-year survival rate of roughly 30%. Moreover, current standard therapies given to unselected NF PNET populations provide only modest and variable benefit. Seeking to stratify such PNET patients according to their likely responses to therapy, we have defined three molecular genetic subtypes (based on mRNA and microRNA transcriptome profiling) using human PNET samples. Interestingly, we observed that two of the three human PNET subtypes - ‘islet tumors’ (IT; insulinomas) and ‘metastasis-like primaries’ (MLP) - were similar at the molecular level to tumor subtypes found in a well-characterized genetically engineered mouse model of PNET. Both human and mouse PNETs of the MLP subtype had microRNA/mRNA transcriptome profiles similar to liver metastases and to precursor/stem cells. The distinctive characteristics of these subtypes may suggest new approaches for selective therapeutic targeting of human PNET, leveraging the capability to study subtype characteristics and drug responses in vivo using the mouse model that phenocopies two of the three PNET subtypes.

Colorectal cancer (CRC) is a heterogeneous disease, and overall survival remains limited despite recent advances in the treatment of metastatic CRC. Unfortunately, the molecular classification methods currently available for CRC do not predict treatment strategies. Seeking new means of classification, we combined gene expression profiling with drug response data to develop clinically deployable assays that identify six integrated patient tumor subtypes with differential prognosis and cellular origin. We asked whether first line CRC therapies might exhibit selectivity for one or more of our subtypes. Indeed, we found that one of the CRC subtypes, which has better disease free prognosis (DFS) in the adjuvant setting, responds to cetuximab in the metastatic setting, whereas a second subtype with poor DFS responds to chemotherapy (but not cetixumab) both in the adjuvant and metastatic settings. As a proof of principle, we identified several subtype-specific CRC cell lines, and tested them as xenograft mouse models, which revealed similar drug responses to those of patients from the same subtype. Overall, the correlation of our CRC subtypes with patient outcome and drug responsiveness, along with clinically deployable means to identify them, support the proposition that targeting selected populations for treatment with this classification system could be clinically beneficial. Our informative cross-filtering between mouse and human tumors that revealed clinically significant subtypes in PNET (to be described) and PDAC (Collison, Sadananadam, et al Nature Medicine 2011) should motivate similar studies in genetically engineered mouse models of CRC, which may produce further knowledge about the biology and therapeutic sensitivities of these provocative new subtypes of CRC.

Citation Format: Anguraj Sadanandam, Douglas Hanahan. Molecular genetic subtypes of pancreas and colon cancer: Phenotypes and potential therapeutic significance. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr SY18-02. doi:10.1158/1538-7445.AM2013-SY18-02

Abstract LB-301: Copper chelation therapy suppresses tumor growth by inhibiting mitochondrial ATP production in tumors

Through our yeast genetic screen, we have previously identified the copper transporter Ctr1 as a major mediator of cisplatin uptake in mammals (1), and have subsequently shown in a transgenic mouse model of human cervical cancer that reducing systemic copper levels with a copper chelator, which is clinically used to treat patients with copper disorders, results in enhanced uptake of cisplatin selectively in tumors but not in normal, non-cancerous tissues (2), suggesting that tumors are particularly sensitive to changes in copper levels. In fact, environmental copper exposure has been associated with cancer risk in humans, although the nature of its effects on tumourigenesis remains unclear. Using a transgenic mouse model of pancreatic islet carcinoma, here we demonstrate that chronic exposure to elevated levels of copper in drinking water, corresponding to the maximum level allowed in our drinking water, accelerate tumor growth by stimulating proliferation of cancer cells. Conversely, reducing systemic copper with a chelating drug resulted in inhibition of tumor growth and cancer cell proliferation. Under copper limitation, tumors displayed decreased activity of the copper-binding mitochondrial enzyme cytochrome c oxidase and reduced ATP levels, despite enhanced glycolysis. The anti-proliferative effect of copper chelation was not observed in cells deficient in cytochrome c oxidase activity, but was enhanced when combined with inhibitors of glycolysis. Interestingly, larger tumors contained less copper than smaller tumors, and exhibited lower activity of cytochrome c oxidase and higher glucose uptake, suggesting that a shift towards glycolytic metabolism observed in tumors even in the presence of ample oxygen (Warburg effect) may in part reflect insufficient copper bioavailability in the tumour microenvironment. Our work identifies copper as a rate-limiting element for tumor growth and mitochondrial ATP production, and provides experimental evidence that explains the association between copper intake levels and cancer implicated in previous epidemiological and clinical studies. These findings offer a novel concept of limiting intake levels of this environmental factor as a strategy for cancer prevention and treatment.

Citation Format: Seiko Ishida, Pénélope Andreux, Johan Auwerx, Douglas Hanahan. Copper chelation therapy suppresses tumor growth by inhibiting mitochondrial ATP production in tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-301. doi:10.1158/1538-7445.AM2013-LB-301

A colorectal cancer classification system that associates cellular phenotype and responses to therapy

Colorectal cancer (CRC) is a major cause of cancer mortality. Whereas some patients respond well to therapy, others do not, and thus more precise, individualized treatment strategies are needed. To that end, we analyzed gene expression profiles from 1,290 CRC tumors using consensus-based unsupervised clustering. The resultant clusters were then associated with therapeutic response data to the epidermal growth factor receptor-targeted drug cetuximab in 80 patients. The results of these studies define six clinically relevant CRC subtypes. Each subtype shares similarities to distinct cell types within the normal colon crypt and shows differing degrees of 'stemness' and Wnt signaling. Subtype-specific gene signatures are proposed to identify these subtypes. Three subtypes have markedly better disease-free survival (DFS) after surgical resection, suggesting these patients might be spared from the adverse effects of chemotherapy when they have localized disease. One of these three subtypes, identified by filamin A expression, does not respond to cetuximab but may respond to cMET receptor tyrosine kinase inhibitors in the metastatic setting. Two other subtypes, with poor and intermediate DFS, associate with improved response to the chemotherapy regimen FOLFIRI in adjuvant or metastatic settings. Development of clinically deployable assays for these subtypes and of subtype-specific therapies may contribute to more effective management of this challenging disease.

Abstract 4391: CD20 as a target for therapy in solid tumors

Using the K14-HPV16 mouse model of squamous carcinogenesis (SCC), we previously reported that B cells foster neoplastic progression through deposition of immunoglobulin complexes in premalignant tissue via Fcα receptor-dependent activation of recruited myeloid cells. Here we evaluated therapeutic interventions targeting these pathways in preclinical trials through administration of depleting αCD20 antibody and small molecule inhibitor of Syk kinase. Both approaches harbored efficacy in preventing premalignant progression to the dysplastic/carcinoma in situ state. Screening a diverse spectrum of human solid tumors revealed SCCs of the vulva, head and neck, as well as pancreatic ductal adenocarcinomas (PDAC) as scoring positively for “signatures” of B cell or plasma cell infiltration, i.e. Ig or CD20 mRNA expression, thereby identifying carcinomas potentially amenable to anti-B cell therapies. Accordingly, B cell-deficient mice failed to support growth of either transplantable orthotopic SCC or PDAC. While administration of αCD20 mAB as a single agent was inefficient in impeding growth of preexisting SCCs, when delivered in combination with cytotoxic chemotherapy, e.g., paclitaxel, carboplatin or cisplatin, αCD20 mAb significantly improved chemotherapeutic response and improved survival by a mechanism dependent on CD8+ T cells. These data reveal that blocking protumorigenic programs regulating by humoral immunity, in combination with chemotherapy, effectively reprograms the tumor immune microenvironment and improves outcome. The authors acknowledge generous support from the NIH/NCI (R01CA130980, R01CA13256, R01CA140943, R01CA15531), the Department of Defense (W81XWH-09-1-0342, W81XWH-10-BCRP-EOHS-EXP) and the Susan G Komen Foundation (KG111084)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4391. doi:1538-7445.AM2012-4391