2015 BMDCR SYMPOSIUM

Cancer Immunotherapy


april 6, 2015 (monday)

Reva and David Logan Center for the Arts

915 East 60th Street Chicago, Illinois 60637

 

SCHEDULE: PDF DOWNLOAD

(Registration 7:30 AM  Symposium 8:00 AM - 5:00 PM)

KEYNOTE SPEAKER
James P. Allison, PhD
The University of Texas MD Anderson Cancer Center
"Immune Checkpoint Blockade in Cancer Therapy"
 
Lisa M. Coussens, PhD
Oregon Health & Science University
"Inflamation and Cancer:Reprogramming the Immune Microenviroment as an Anti-Cancer Therapeutic Strategy"
 
Thomas F Gajewski, MD, PhD
The University of Chicago
"Molecular Mechanisms of the T Cell-Inflamed Tumor Microenviroment"
 
Nicholas P Restifo, MD
National Cancer Institute, Center for Cancer Research
"Developing Curative Cancer Treatments Using Adoptive Cell Transfer-Based Immunotherapies"
 
Antoni Ribas, MD, PhD
University of California, Los Angeles
"T Cell and Melanoma Cell Interactions Leading to Response with PD-1 Blockade"
 
Alexander Rudensky, PhD
Memorial Sloan Kettering Cancer Center
"Regulatory T Cells and Cancer"
 
Michel Sadelain, MD, PhD
Memorial Sloan Kettering Cancer Center
"CAR T Cell Therapy and the Promise of T Cell Engineering"
 
Robert D. Schreiber, PhD
Washington University School of Medicine
"Personalizing Cancer Immunotherapy"
 
Melody A. Swartz, PhD
The University of Chicago
"Tumor-Associated Lymphatic Vessels Modulate the Stromal Microenviroment to Promote Tumor Invasion"

 

ABSTRACTS

James P. Allison, PhD

The existence of multiple non-redundant inhibitory pathways that limit T cell responses offers novel strategies for mobilizing the immune system to attack cancer cells.  The best characterized of these immune checkpoints is CTLA-4, which inhibits T cell proliferation by interfering with the interaction of the costimulatory molecule CD28 with its ligands B7-1 and B7-2 on the surface of antigen presenting cells.    Antibodies to CTLA-4 have proven effective against multiple tumor types in both pre-clinical and clinical studies.  Ipilimumab, an antibody to human CTLA-4, showed long term (>10 years) survival benefit in about 20% of patients in a randomized, placebo-controlled trial in late stage melanoma.  In 2011 it was approved by the FDA for treatment of late stage melanoma and is now a standard of care for that disease. 

The mechanism(s) of action of anti-CTLA-4 are still being elucidated.  We and others have shown that CLTA-4 limits T cell proliferation by a cell intrinsic mechanism.  However, there is also evidence that anti-CTLA-4 has to engage the target on both effector (Teff) and regulatory (Treg) T cells. Thus anti-CTLA-4 exerts its anti-tumor effects by multiple mechanisms.

PD-1, another checkpoint, recruits a phosphatase and seems to interfere with T cell antigen receptor mediated signaling.  It has two ligands, PD-L1 and PD-L2, which are both expressed on dendritic cells.  However, many tumor cells also express PD-L1.  Antibodies to PD-1 and PD-L1 have both shown objective responses against several tumor types in clinical trials with response rates of about 25% .  A recent phase II trial of a combination of anti-PD-1 and anti-CTLA-4 in melanoma showed objective responses in about 50% of late stage melanoma patients.

These studies and their implications for cancer therapy will be discussed


Lisa M. Coussens, PhD

The concept that leukocytes are critical components of solid tumors is now generally accepted, however, their role(s) in regulating aspects of neoplastic progression, and/or response to cytotoxic therapy is only beginning to be understood. Utilizing de novo mouse models of organ-specific cancer development, we now appreciate that adaptive leukocytes differentially regulate myeloid cell recruitment, activation and behavior, and in turn, engaged tumor-infiltrating myeloid cells activate tissue-based programs to foster malignancy, as well as repress anti-tumor immunity by a diversity of mechanisms. Treatment of tumor-bearing mice with therapeutic agents that disrupt lymphocyte-myeloid cell interaction, myeloid cell activation, or myeloid cell functionality invariably results in slowing of primary tumor growth, and also improved responses to cytotoxic therapies, and significantly diminished presence of metastatic disease. To be presented will be our recent insights into organ and tissue-specific regulation of cancer development by adaptive and innate immune cells, and new studies evaluating how attenuating protumor properties of select lymphoid and myeloid cells can be exploited to enhance therapeutic responses to cytotoxic therapy. 

LMC acknowledges generous support from the NIH / NCI, the Department of Defense Era of Hope Scholar Expansion Award, Susan G. Komen Foundation, the Breast Cancer Research Foundation, and a SU2C award supported by the AACR and Lustgarten Foundation. 


Thomas F Gajewski, MD, PhD

Most cancers express tumor antigens that can be recognized by T cells of the host.  The fact that cancers that become clinically relevant grow nonetheless implies that immune escape must occur to allow cancer outgrowth.  We have observed two major subsets of human melanoma metastases based on gene expression profiling and confirmatory assays.  One subgroup of patients has an inflamed phenotype that includes expression of chemokines, T cell markers, and a type I IFN signature.  In contrast, the other major subset lacks this phenotype and appears to display immune “exclusion”.  The mechanisms of immune escape are likely distinct in these two phenotypes, and therefore the optimal immunotherapeutic interventions necessary to promote clinical responses may be different.  The T cell-inflamed tumor microenvironment subset shows the highest expression of negative regulatory factors, including PD-L1, IDO, and FoxP3+ Tregs, and evidence for T cell-intrinsic anergy has also emerged aided by a recently defined functional role of EGR2.  In addition, the mechanism of induction of these inhibitory mechanisms has been elucidated—PD-L1 and IDO are induced by IFN-g, and Tregs are largely recruited by the chemokine CCL22, both being produced by activated CD8+ effector T cells.  Preclinical experiments have confirmed a critical role for each of these mechanisms in limiting anti-tumor T cell efficacy in vivo, giving candidate treatment strategies for translation back into the clinic.  These include anti-PD-1/PD-L1 mAbs, IDO inhibitors, and approaches to deplete CD25+ Tregs and/or reverse anergy.  The presence of multiple inhibitory mechanisms in the same tumor microenvironment argues that combination therapies may be advantageous.  Preclinical data have indicated synergy between anti-CTLA-4 +/- anti-PD-L1 +/- IDO inhibition.  The mechanism of synergy is striking, as it correlates with a marked improvement of IL-2 production and proliferation of tumor-infiltrating CD8+ T cells.  Clinical translation of multiple combination immunotherapies is promising and ongoing.  In contrast to the T cell-inflamed melanomas, a new paradigm may be needed to promote de novo inflammation in cases of the non-T cell-infiltrated tumor microenvironment.  Natural innate immune sensing of tumors appears to occur via the host STING pathway, type I IFN production, and cross-priming of T cells via CD8a+ DCs.  New strategies are being developed to engage or mimic this pathway as a therapeutic endeavor.  The molecular mechanisms that mediate the presence or absence of the T cell-inflamed tumor microenvironment in patients are being elucidated using parallel genomics platforms and should open up additional new treatment approaches to ultimately expand the fraction of patients who respond to novel immunotherapies.  The first of these identified mechanisms is tumor-intrinsic b-catenin signaling, which potently mediates immune exclusion. 


Nicholas P. Restifo, MD

Adoptive cell therapy (ACT) is a highly personalized cancer therapy that involves administration to the cancer bearing host of immune cells with direct anti-cancer activity. ACT has multiple advantages compared to other forms of cancer immunotherapy that rely on the active in vivo development of sufficient numbers of anti-tumor T cells with the functions necessary to mediate cancer regression. For use in ACT, large numbers of anti-tumor lymphocytes (up to 1011) can be readily grown in vitro and selected for high avidity recognition of the tumor as well as for the effector functions required to mediate cancer regression. In vitro activation allows such cells to be released from the inhibitory factors that exist in vivo. Perhaps most importantly, ACT enables the manipulation of the host prior to cell transfer to provide a favorable microenvironment that better supports anti-tumor immunity. ACT is a ‘living’ treatment: the administered cells can exhibit ‘stem cell-like’ proliferative behavior, maintaining their anti-tumor effector functions long-term.

A major factor limiting the successful utilization of ACT in humans is the identification of cells that can target antigens selectively expressed on the cancer and not on essential normal tissues. ACT has used either natural host cells that exhibit anti-tumor reactivity or host cells that have been genetically engineered with anti-tumor T cell receptors (TCR) or chimeric antigen receptors (CAR). Utilizing these approaches, ACT has mediated dramatic regressions in a variety of cancer histologies including melanoma, cervical cancer, lymphoma, leukemia, bile duct cancer, and neuroblastoma. We will discuss the current state of ACT for the treatment of human cancer as well as the principles of effective treatment that point towards improvements in this approach.

ACT is a more complex approach to the delivery of cancer treatment than many other types of immunotherapy and has often been criticized as ‘impractical’ and ‘too costly’ for widespread application. The need to develop highly personalized treatments for each patient does not fit into the paradigm of major pharmaceutical companies who depend on ‘off the shelf’ reagents. However, curative immunotherapies for patients with common epithelial cancers may dictate the need for new personalized cell-based approaches. Technology might reduce the cost of selecting and expanding a patient’s lymphocytes, and detailed genetic analysis of individual tumors is already commonplace at large academically-affiliated medical centers. Ultimately, the effectiveness of treatment will need to trump convenience of administration in the application of new effective approaches to cancer immunotherapy based on ACT.


Antoni Ribas, MD, PhD

Immunotherapy with PD-1 or PD-L1 blockade is changing the landscape of cancer therapy, as best evidenced in advanced melanoma with sustained tumor responses in a significant number of patients leading to the first approvals of anti-PD-1 therapy by the FDA.

PD-1 regulates primarily the effector phase of T-cell responses after chronic antigen exposure. The hypothesized mechanism of action of anti-PD-1 blockade led us to focus on the study of intratumoral T cell distribution and clonality at baseline and post-dosing biopsies. PD-L1 can be expressed constitutively (in a minority of cancers) or induced by interferons produced by tumor –infiltrating lymphocytes. The PD-L1 inducible process has been termed “adaptive immune resistance”, and represents a mechanism by which cancer cells attempt to protect themselves from immune-cell mediated cell killing.

We analyzed samples obtained before and during anti-PD1 therapy using quantitative immunohistochemistry, immunofluorescence and next generation sequencing for T-cell receptors (TCR). Pre-treatment samples obtained from responding patients showed increased numbers of CD8, PD-1, and PD-L1 expressing cells at the invasive tumor margin and inside tumors, with close proximity between PD-1 and PD-L1, and a more clonal TCR repertoire.

In serially sampled tumors, responding patients showed proliferation of intratumoral CD8+ T-cells. Using multivariate analysis incorporating CD8 T cell distribution at baseline, TCR clonality, as well as PD-1 and PD-L1 expression and proximity, we established a predictive model based on CD8 expression at the invasive margin. We validated this model in an independent cohort of biopsies form 15 patients that we obtained from our colleagues at the Gustave Roussy in Villejuif, France. Our model could correctly predict the clinical outcome of 13 of the 15 patients.

The implications of this work is that we should be able to select patients for single agent anti-PD-1/L1 therapies if there are pre-existing tumor antigen-specific intratumoral T cells that are inactive due to PD-1/L1 interactions, or select patients for combined therapy adding other immune activating strategies to PD-1/L1 blockade because such cells were not in tumors. Additionally, in some cases there may not be T cell recognition of tumors, and in these cases gene engineering approaches for adoptive cell transfer therapy would provide the required T cells for an antitumor immune response.


Alexander Rudensky, PhD


Michel Sadelain, MD, PhD

T cell engineering is emerging as a powerful means to rapidly generate large supplies of tumor-targeted T cells for cancer immunotherapy. To this end, a new toolbox of synthetic receptors used to genetically target and reprogram T lymphocytes has been created, the best known of which are chimeric antigen receptors (CARs). CARs are recombinant receptors for antigen that retarget and reprogram T cell function to destroy tumor cells, sustain T cell persistence and enhance T cell function within the tumor microenvironment. Over a decade ago, we proposed that CD19 may serve as an effective target for CAR therapies. We were the first to report that human peripheral blood T lymphocytes could be effectively targeted to CD19 by retroviral-mediated gene transfer and that CD19 CAR T cells could eradicate established, systemic B cell malignancies in xenogeneic tumor models. Four groups including our own recently reported exciting clinical results in B cell malignancies, most dramatically in patients with relapsed, chemorefractory acute lymphoblastic leukemia (ALL). The CD19 model has emerged as the paradigm for CAR therapy and paves the way for extending this cell-based treatment to other cancers.


Robert D. Schreiber, PhD

Cancer Immunoediting is the process by which the immune system controls and shapes cancer. In its most complex form, cancer immunoediting occurs in three phases: Elimination (the host protective phase of the process), Equilibrium (where tumor cells that survive immune elimination are maintained in a state of functional tumor dormancy) and Escape (where clinically apparent tumors emerge because immune sculpting of the tumor cells has produced variants that display either reduced immunogenicity or enhanced immunosuppressive activity). Strong experimental data have been obtained using mouse cancer models to demonstrate the existence of each phase of the cancer immunoediting process and compelling clinical data suggests that a similar process also occurs in human cancer. Our efforts now focus on elucidating the molecular and cellular mechanisms that underlie each phase of cancer immunoediting and identifying the critical checkpoints that regulate progression from one phase of the process to the next. We previously used a combination of exome sequencing and epitope prediction algorithms to show that mutant proteins in highly immunogenic tumor cells derived from methylcholanthrene treated immunodeficient mice represent immunodominant, tumor specific antigens for CD8+ T cells and that immunoselection is a major mechanism of immunoediting. More recently, we asked whether our approach could identify antigens in progressively growing tumors that render them susceptible to checkpoint blockade immunotherapy. T cell lines generated from anti-PD-1 treated mice that rejected d42m1-T3 progressor sarcoma cells displayed restriction to H-2Kb but not to H-2Db. We then identified expressed nonsynonymous mutations in d42m1-T3 cells using exome sequencing and generated a prioritized list of potential H-2Kb binding epitopes. This analysis predicted two unequivocal "best candidates"—a mutant form of Laminin α subunit 4 (mLama4) and a mutant glucosyltransferase (mAlg8). When tested in vitro, these two epitopes were the only ones among the 62 top predicted H-2Kb binding sequences that stimulated d42m1-T3 specific T cell lines. These findings were validated by showing that: (i) CTLs expressing TCRs for mLama4 and mAlg8 accumulated in d42m1-T3 tumors in anti-PD-1-treated, tumor-bearing mice; (ii) vaccination of naïve WT mice with mutant but not WT forms of Lama4 or Alg8 induced strong CD8+ T cell responses; and (iii) naïve mice vaccinated either prophylactically or therapeutically against mLama4 plus mAlg8 controlled outgrowth of d42m1-T3 tumors. These findings reveal that our genomics approach may help identify individuals who will benefit from checkpoint blockade cancer immunotherapy and may also provide insights needed to develop personalized cancer vaccines.


Melody A. Swartz, PhD

Lymphatic vessels and cancer metastasis have long been correlated: the presence of the lymphatic growth factors VEGF-C/D in the tumor microenvironment associates with increased metastasis and poor prognosis, and function-blocking antibodies against their main receptor VEGFR-3, which prevent new lymphatic growth, are being tested in clinical trials to prevent metastasis. On the other hand, VEGF-C likely plays complex roles in the tumor microenvironment; in addition to driving lymphatic expansion locally and in the draining lymph node (LN), it has also been shown to increase lymphatic drainage, alter immune cell transport to the LN, and increase levels of the lymphoid chemokine CCL21, which attracts leukocytes, naïve T cells, and regulatory T cells, among others. VEGF-C can be secreted by tumor-associated macrophages and even tumor cells themselves. In this study, we asked how VEGF-C-driven lymphatic activation alters the tumor stroma, both biomechanically as well as immunologically, particularly in its support of immune cell infiltrates and suppressive cytokine environment. In addition to causing lymphatic expansion, we found that VEGF-C stimulates multiple and complex alterations in the tumor stroma that promote immune suppression and invasion. These include lymphatic secretion of tenascin-C and TGF-b, driving myofibroblast activation and pro-invasive stromal remodeling, as well as secretion of immune suppressive factors like IDO. Furthermore, we found that VEGF-C enhances lymphatic endothelial cell scavenging and presentation of tumor antigens on MHCI and MHCII molecules as well as PD-L1, in turn dampening anti-tumor T cell responses. Together, these data suggest that VEGF-C/VEGFR-3 targeting could potentially be important not only for preventing lymphangiogenesis, but also in strategies that aim to alter the tumor microenvironment in order to make traditional therapies and immunotherapies more effective.