HDAC9 and cancer: Pyroptosis degree was in most cancer types significantly positively related to cytotoxic T-lymphocyte antigen 4 (CTLA4) pathway, interferon (IFN) pathway, hypoxia and glycolosis pathway, T cell and B cell pathway, histone deacetylase (HDAC) pathway, human epidermal growth factor receptor 2 (HER2) pathway, and phosphatidylinositol 3 kinase (PI3K) pathway.