Regulatory T cells (Tregs) are crucial mediators of immune homeostasis. They regulate immune response by suppressing inflammation and promoting self-tolerance. In addition to their immunoregulatory role, a growing body of evidence highlights the dynamic role of Tregs in angiogenesis, the process of forming new blood vessels. Although angiogenesis is critically important for normal tissue regeneration, it is also a hallmark of pathological processes, including malignancy and chronic inflammation. Interestingly, the role of Tregs in angiogenesis has been shown to be highly tissue- and context-specific and as a result can yield either pro- or antiangiogenic effects. For these reasons, there is considerable interest in determining the molecular underpinnings of Treg-mediated modulation of angiogenesis in different disease states. The present review summarizes the role of Tregs in angiogenesis and mechanisms by which Tregs regulate angiogenesis and discusses how these mechanisms differ in homeostatic and pathological settings.

The identification of the barriers to care for patients with head and neck cancer in low-income and lower-middle-income countries is a crucial first step toward the identification of targets for developing and implementing cost-effective programs to increase awareness, prevention, and treatment of head and neck cancer in this setting.OBJECTIVE To identify the barriers to care for patients presenting with head and neck cancer in low-income and lower-middle-income countries.EVIDENCE REVIEW Nine databases were searched from their inception to December 21, 2017: Africa-Wide Information, the Cochrane Library, Embase, Global Health, LILACS, MEDLINE, BIOSIS Previews, and Web of Science. Search terms referred to head and neck cancer, barriers to care, and low-and lower-middle-income countries, and no temporal and linguistic restrictions were imposed. Articles were reviewed by 2 independent investigators, and differences in inclusion were resolved by discussion. Bibliographies of all included articles were screened, and all relevant articles were reviewed using the same procedure. Quantitative articles were assessed using the Methodological Index for Non-Randomized Studies tool, and articles with qualitative data used the Critical Appraisal Skills Programme qualitative checklist. This systematic review was registered in PROSPERO (registration No. CRD42018092448) and followed the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols.FINDINGS Of the 44 articles selected for review, 18 (41%) met the selection criteria. All articles reported quantitative results, and 3 (17%) added some qualitative material to the study design. Most (11 [61%]) of the studies originated from India. A total of 41 different barriers to care were identified, with low level of education (cited in 8 articles [44%]), low socioeconomic status (in 4 articles [22%]), and lack of knowledge about head and neck cancer (in 3 articles [17%]) being statistically associated with a delayed presentation. Misunderstanding of signs and symptoms, use of alternative medicine, and inability to access health care were other barriers discussed in the qualitative articles.CONCLUSIONS AND RELEVANCE This systematic review highlighted the lack of both qualitative and quantitative information for patients with head and neck cancer in low-income and lower-middle-income countries. The findings suggest that integrating the barriers to care with information from patient lives may identify the clinical and social relevance of these barriers and guide future research.