IL17A and neoplasm: Recent research has shown that, both cells and cell factors, inside the tumor microenvironment are directly or indirectly involved in drug resistance, including cells such as T-regulatory cells (Tregs) [9], cancer stem cells (CSCs) [10], tumor-associated fibroblasts (TAFs) [11], and tumor-associated microphages (TAMs) [12], and cell factors such as transforming growth factor (TGF)-β1 [13], hypoxia-inducible factor (HIF)-1α [14], interleukin (IL)-17 [15], IL-6 [16], IL-8 [17], IL-10 [18], and tumour necrosis factor (TNF)-α [19].