In recent decades, cancer research has expanded exponentially beyond the study of abnormally dividing cells to include complex and extensive heterotypic interactions between cancer and noncancer cells that constitute the tumor microenvironment (TME). Modulation of stromal, immune, and endothelial cells by cancer cells promotes proliferation, survival, and metabolic changes that support tumor growth and metastasis. Recent evidence demonstrates that tumors can recruit peripheral nerves to the TME, leading to enhanced tumor growth in a range of cancer models through distinct mechanisms. This process, termed tumor innervation, is associated with an aggressive tumor phenotype and correlates with poor prognosis in clinical studies. Therefore, the peripheral nervous system may play an underrecognized role in cancer development, harboring targetable pathways that warrant investigation. To date, nerves have been implicated in driving proliferation, invasion, metastasis, and immune evasion through locally delivered neurotransmitters. However, emerging evidence suggests that cell-cell communication via exosomes induces tumor innervation, and thus exosomes may also mediate neural regulation of the TME. In this Review, seminal studies establishing tumor innervation are discussed, and known and putative signaling mechanisms between peripheral nerves and components of the TME are explored as a means to identify potential opportunities for therapeutic intervention.
Stefan M. Gysler, Ronny Drapkin
Iron plays an important role in mammalian physiological processes. It is a critical component for the function of many proteins, including enzymes that require heme and iron-sulfur clusters. However, excess iron is also detrimental because of its ability to catalyze the formation of reactive oxygen species. As a result, cellular and systemic iron levels are tightly regulated to prevent oxidative damage. Iron deficiency can lead to a number of pathological conditions, the most prominent being anemia. Iron deficiency should be corrected to improve adult patients’ symptoms and to facilitate normal growth during fetal development and childhood. However, inappropriate use of intravenous iron in chronic conditions, such as cancer and heart failure, in the absence of clear iron deficiency can lead to unwanted side effects. Thus, this form of therapy should be reserved for certain patients who cannot tolerate oral iron and need rapid iron replenishment. Here, we will review cellular and systemic iron homeostasis and will discuss complications of iron deficiency.
Navid Koleini, Jason S. Shapiro, Justin Geier, Hossein Ardehali
First administered to a human subject as a tuberculosis (TB) vaccine on July 18, 1921, Bacillus Calmette-Guérin (BCG) has a long history of use for the prevention of TB and later the immunotherapy of bladder cancer. For TB prevention, BCG is given to infants born globally across over 180 countries and has been in use since the late 1920s. With about 352 million BCG doses procured annually and tens of billions of doses having been administered over the past century, it is estimated to be the most widely used vaccine in human history. While its roles for TB prevention and bladder cancer immunotherapy are widely appreciated, over the past century, BCG has been also studied for nontraditional purposes, which include (a) prevention of viral infections and nontuberculous mycobacterial infections, (b) cancer immunotherapy aside from bladder cancer, and (c) immunologic diseases, including multiple sclerosis, type 1 diabetes, and atopic diseases. The basis for these heterologous effects lies in the ability of BCG to alter immunologic set points via heterologous T cell immunity, as well as epigenetic and metabolomic changes in innate immune cells, a process called “trained immunity.” In this Review, we provide an overview of what is known regarding the trained immunity mechanism of heterologous protection, and we describe the current knowledge base for these nontraditional uses of BCG.
Alok K. Singh, Mihai G. Netea, William R. Bishai
The immunoprevention of cancer and cancer recurrence is an important area of concern for the scientific community and society as a whole. Researchers have been working for decades to develop vaccines with the potential to alleviate these health care and economic burdens. So far, vaccines have made more progress in preventing cancer than in eliminating already established cancer. In particular, vaccines targeting oncogenic viruses, such as the human papillomavirus and the hepatitis B virus, are exceptional examples of successful prevention of virus-associated cancers, such as cervical cancer and hepatocellular carcinoma. Cancer-preventive vaccines targeting nonviral antigens, such as tumor-associated antigens and neoantigens, are also being extensively tested. Here, we review the currently approved preventive cancer vaccines; discuss the challenges in this field by covering ongoing preclinical and clinical human trials in various cancers; and address various issues related to maximizing cancer vaccine benefit.
Tomohiro Enokida, Alvaro Moreira, Nina Bhardwaj
Tumor metastasis is a singularly important determinant of survival in most cancers. Historically, radiation therapy (RT) directed at a primary tumor mass was associated infrequently with remission of metastasis outside the field of irradiation. This away-from-target or “abscopal effect” received fringe attention because of its rarity. With the advent of immunotherapy, there are now increasing reports of abscopal effects upon RT in combination with immune checkpoint inhibition. This sparked investigation into underlying mechanisms and clinical trials aimed at enhancement of this effect. While these studies clearly attribute the abscopal effect to an antitumor immune response, the initial molecular triggers for its onset and specificity remain enigmatic. Here, we propose that DNA damage–induced inflammation coupled with neoantigen generation is essential during this intriguing phenomenon of systemic tumor regression and discuss the implications of this model for treatment aimed at triggering the abscopal effect in metastatic cancer.
Timothy P. Lippert, Roger A. Greenberg
Since the discovery of myostatin (MSTN; also known as GDF-8) as a critical regulator of skeletal muscle mass in 1997, there has been an extensive effort directed at understanding the cellular and physiological mechanisms underlying MSTN activity, with the long-term goal of developing strategies and agents capable of blocking MSTN signaling to treat patients with muscle loss. Considerable progress has been made in elucidating key components of this regulatory system, and in parallel with this effort has been the development of numerous biologics that have been tested in clinical trials for a wide range of indications, including muscular dystrophy, sporadic inclusion body myositis, spinal muscular atrophy, cachexia, muscle loss due to aging or following falls, obesity, and type 2 diabetes. Here, I review what is known about the MSTN regulatory system and the current state of efforts to target this pathway for clinical applications.
Se-Jin Lee
Sickle cell disease (SCD) is a monogenic disorder characterized by recurrent episodes of severe bone pain, multi-organ failure, and early mortality. Although medical progress over the past several decades has improved clinical outcomes and offered cures for many affected individuals living in high-income countries, most SCD patients still experience substantial morbidity and premature death. Emerging technologies to manipulate somatic cell genomes and insights into the mechanisms of developmental globin gene regulation are generating potentially transformative approaches to cure SCD by autologous hematopoietic stem cell (HSC) transplantation. Key components of current approaches include ethical informed consent, isolation of patient HSCs, in vitro genetic modification of HSCs to correct the SCD mutation or circumvent its damaging effects, and reinfusion of the modified HSCs following myelotoxic bone marrow conditioning. Successful integration of these components into effective therapies requires interdisciplinary collaborations between laboratory researchers, clinical caregivers, and patients. Here we summarize current knowledge and research challenges for each key component, emphasizing that the best approaches have yet to be developed.
Phillip A. Doerfler, Akshay Sharma, Jerlym S. Porter, Yan Zheng, John F. Tisdale, Mitchell J. Weiss
Scientific progress and discovery of preventions and cures for life-threatening diseases depend on the vitality of the biomedical research workforce. We analyzed the workforce of cancer researchers applying for and receiving R01 awards from the National Cancer Institute (NCI) from fiscal years 1990 to 2016, the last year prior to implementation of the Next Generation Researchers Initiative. Here we report that the NCI R01 Principal Investigator (PI) workforce expanded 1.4-fold and aged over this time frame. We tracked 9 age groups and found that the number of PIs in the 3 oldest groups increased dramatically, in contrast with the younger groups. Sustained increases in the number of funded older PIs stemmed from increases in the number of older PIs submitting applications, rather than higher funding rates for older PIs. The decline in the number of funded younger PIs was driven in part by (a) a marked increase in time from PhD degree to first R01 application and award, as well as (b) a decrease in retention of PIs in the funded R01 workforce beyond their first R01 award. The NCI is using these and other analyses to inform strategies and policies for attracting, supporting, and retaining meritorious early-career researchers.
Melissa D. Antman, Roman Gorelik, Amy Kennedy, Grace F. Liou, Eddie N. Billingslea, James G. Corrigan, L. Michelle Bennett
As part of the centennial celebration of insulin’s discovery, this review summarizes the current understanding of the genetics, pathogenesis, treatment, and outcomes in type 1 diabetes (T1D). T1D results from an autoimmune response that leads to destruction of the β cells in the pancreatic islet and requires life-long insulin therapy. While much has been learned about T1D, it is now clear that there is considerable heterogeneity in T1D with regards to genetics, pathology, response to immune-based therapies, clinical course, and susceptibility to diabetes-related complications. This review highlights knowledge gaps and opportunities to improve the understanding of T1D pathogenesis and outlines emerging therapies to treat or prevent T1D and reduce the burden of T1D.
Alvin C. Powers
Immune checkpoint inhibitors (ICIs) have transformed the treatment of various cancers, including malignancies once considered untreatable. These agents, however, are associated with inflammation and tissue damage in multiple organs. Myocarditis has emerged as a serious ICI-associated toxicity, because, while seemingly infrequent, it is often fulminant and lethal. The underlying basis of ICI-associated myocarditis is not completely understood. While the importance of T cells is clear, the inciting antigens, why they are recognized, and the mechanisms leading to cardiac cell injury remain poorly characterized. These issues underscore the need for basic and clinical studies to define pathogenesis, identify predictive biomarkers, improve diagnostic strategies, and develop effective treatments. An improved understanding of ICI-associated myocarditis will provide insights into the equilibrium between the immune and cardiovascular systems.
Javid Moslehi, Andrew H. Lichtman, Arlene H. Sharpe, Lorenzo Galluzzi, Richard N. Kitsis
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