Innate immunity in Cancer Immunotherapy
RATIONALE
Sentinels of the innate immune system have been suggested to possess a dichotomous role in cancer, capable of both tumor progression and suppression, in a context dependent manner. Growing evidence indicates that innate immune effectors can be driven to impart anti-tumor immunity both directly and indirectly, given the proper cues. Diagnosis of cancer presents a significant challenge, resulting in morbidity and management costs of billions of dollars/year in the U.S. Immunotherapy has revolutionized the treatment of a variety of cancers (ex., lung, skin, lymphoma, myeloma, etc). However, not all patients respond to treatment. A deeper understanding of the interaction between the immune system and specific cancer is critical to improve existing therapies and to discover more effective treatments.
Cancer immunotherapy drugs called checkpoint inhibitors are one of the most promising approaches for cancer treatment today. These drugs target proteins like PD-1, PD-L1, and CTLA-4, which put the ‘brakes’ on the immune response by repressing the ability of T-cells to recognize and kill cancer cells. Checkpoint inhibitors act against these proteins and enable the patient T-cells to ‘see’ the tumors and attack them. However, these therapies are truly effective only in a handful of cancer patients as tumors can develop resistance. Therefore, new strategies are needed to enhance the effectiveness of these checkpoint inhibitors.
RESEARCH STRATEGY
A. SIGNIFICANCE
Cancer immunotherapy attempts to boost the body’s own defense mechanism – the immune system, to kill cancer cells and defeat cancer. Immunotherapy with T cell checkpoint inhibitors is promising to revolutionize cancer therapy. However, a major limitation of these therapies is that they are effective in only a subset of patients. Recent evidence suggests that enhanced T cell infiltration in the tumor is a predictive marker of positive response to T cell checkpoint inhibitors. Thus, failure to respond to T cell checkpoint inhibitors may correspond to a defect in the ability of the innate immune system to effectively engage adaptive anti-tumor immune response. Several innate immune cell populations, appropriately activated, can directly kill tumor cells. Natural killer (NK) cells and NK T cells can recognize cell surface stress ligands and tumor-derived glycolipids expressed by tumor cells, respectively, leading to innate cell activation and tumor cell lysis.1 Macrophages can kill tumor cells through secretion of nitric oxide species.2 Thus, immunotherapies stimulating these innate immune cell populations have the potential to augment the cytotoxic activities of T cells.
B. INNOVATION
Our approach will focus on to activate innate immunity in the cancer cells that is elicited when immune cells detect certain pathogenic molecules and actively recruit T-cells to the tumor. KRAS is one of the most commonly mutated oncogenes in human cancer, with selectively high frequency in tumors of the lung (30% of patients). KRAS mutant tumors are associated with poor prognosis, yet there are no effective therapies to specifically treat cancers expressing the KRAS oncogene. No direct inhibitor of mutant KRAS has been approved so far and first-line therapy for patients with advanced KRAS mutant disease remains systemic chemotherapy with associated toxicity and therapeutic limitations. Therefore, an urgent need remains for innovative and effective therapeutic strategies to improve outcomes for KRAS mutant cancer patients. We will use genetic-defined tools to broaden the current understanding of the biology of KRAS in cancer with the ultimate goal of developing new therapeutic approaches for KRAS-driven cancers.
Aim 1. Define the infiltrated Immune cell populations in the tumor microenvironment utilizing solid tumor models (B16-melanoma and Mc-38 colon Carcinoma).
With the help of next generation technologies, Nanostring in combination with CyToF we will identify the tumor infiltrating immune cell populations in a time-dependent manner and their gene signatures to identify the innate immune effectors.
(i) NanoString’s nCounter analysis system offers advantages over current gene expression profiling methods including digital output of data and direct mRNA measurement without enzymatic reaction.3 The nCounter technology has been used to evaluate gene signatures in many clinical trial settings. In melanoma, a 53-gene immune signature identified by the nCounter system was able to predict non-progression, prolonged recurrence-free survival, and disease-specific survival.4
(ii) Cytometry by time-of-flight (CyTOF) uses heavy metal isotopes to label antibodies, and then labeled cells are analyzed by high-throughput spectrometry on a single-cell level. This approach of cell profiling provides more parameters to quantify than does traditional flow cytometry, which is limited by overlap between the emission spectra of individual fluorophores.5,6
Aim 2. Elucidating mechanisms of tumor-induced macrophage/dendritic cell tolerization and immune suppression. (using spontaneous cancer models)
In this proposal, we will use unique Tamoxifen (Tm)-inducible transgenics, widely used to perform gene inactivation and lineage tracing studies in mice. Using a lung cancer model of KRAS, we will investigate cancer-mediated paracrine signaling pathways and cancer-derived exosome-dependent pathways that functionally tolerize macrophages/dendritic cells within the tumor microenvironment. Understanding the metabolic shifts of macrophages/dendritic cells within the tumor microenvironment that enable the development of regulatory T cells, will definitely provide novel leads to effective immunotherapy. These pre-clinical studies will provide critical evidence for clinical development of this immunomodulatory approach either alone or combined with chemotherapy to improve lung cancer treatment and ultimately, clinical outcomes.
We will then define the mechanisms by which macrophages/dendritic cells residing outside of the tumor microenvironment regulate T cell immunosurveillance in our cancer models. Together, these aims will inform the development of myeloid-directed combinatorial therapies designed to align innate and adaptive immunity for cancer therapy.
Conclusion
Past efforts to comprehensively define tumor genomes have revealed critical tumor dependencies that ultimately enabled the development of more effective therapeutics and treatments for patients. Preclinical experimentation guides the discovery and evaluation of therapeutic targets, making it vital to fully understand the extent and limits of their fidelity to human correlates. Immunotherapy regimens aiming to drive T cell responses against tumors are often limited by the lack of activated antigen presenting cells in tumors and tumor-draining lymph nodes. To this end, intratumoral treatment with agonists of pattern recognition receptors and other innate danger sensors expressed by DCs and macrophages has been successfully used to substantially reshape the number and phenotype of tumor infiltrating leukocytes. In this proposal, we propose to characterize tumor infiltrating innate immune cell population and to identify novel innate effector molecules for combinatorial immunotherapy.
PUBLIC HEALTH RELEVANCE
The proposed studies will incorporate clinically-relevant mouse models of skin, colon or lung cancer to facilitate the identification of new targets and development of novel immunotherapies capable of improving patient outcomes.
REFERENCE
1. Woo SR, Corrales L, Gajewski TF. Innate immune recognition of cancer. Annu Rev Immunol. 2015;33:445–74. doi: 10.1146/annurev-immunol-032414-112043.
2. Singh M, Khong H, Dai Z, Huang X-F, Wargo JA, Cooper ZA, Vasilakos JP, Hwu P, Overwijk WW. Effective Innate and Adaptive Antimelanoma Immunity through Localized TLR7/8 Activation. The Journal of Immunology. 2014;193(9):4722–31. doi: 10.4049/jimmunol.1401160.
3. Geiss, G. K. et al. Direct multiplexed measurement of gene expression with color-coded probe pairs. Nat. Biotechnol. 26, 317–325 (2008).
4. Sivendran, S. et al. Dissection of immune gene networks in primary melanoma tumors critical for antitumor surveillance of patients with stage II-III resectable disease. J. Invest. Dermatol. 134, 2202–2211 (2014).
5. Newell, E. W., Sigal, N., Bendall, S. C., Nolan, G. P. & Davis, M. M. Cytometry by time-of-flight shows combinatorial cytokine expression and virus-specific cell niches within a continuum of CD8+T cell phenotypes. Immunity 36, 142–152 (2012).
6. Yao, Y. et al. CyTOF supports efficient detection of immune cell subsets from small samples. J. Immunol. Methods 415, 1–5 (2014).