FIGURE 1.

The hierarchy of tumor ecosystem. Taking breast cancer as an example, the patient's systemic environment can be perceived as an integral ecosystem and scoped at three different levels: primary (cancerous breast), regional (metastatic lymph node) and distal (metastatic brain, lung, liver or bone) onco‐spheres. The material and energy flow throughout the systemic onco‐sphere are largely ascribed to its metabolic function within the host macroenvironment. Besides internal factors, food and nutrient, microorganisms (e.g., viruses and bacteria) and therapeutic interventions (e.g., irradiation) serve as external stimuli that also shape the tumor ecosystem. Abbreviations: Tregs, Regulatory T cells; MDSCs, myeloid‐derived suppressor cells.