TGFB1 and neoplasm: Potential reasons for the lack of effectiveness of intratumoral immunotherapy in advanced cancer states include the development of complex immunosuppressive features: (i) low CD8 T-cell to tumor ratio [4], (ii) extensive systemic suppressive cell populations such as myeloid derived suppressor cells (MDSCs) [5] and T-regulatory cells [6], (iii) poor T-cell trafficking into the tumor [7], (iv) an immunosuppressive tumor microenvironment [8], and (vi) increased levels of soluble immunosuppressive substances such as prostaglandin E2 [9], TGF-β [10], VEGF [11] or IL-10 [12,13].