“…In particular, we hypothesize that inhibition of SK activity will alter signaling through the PD-1/PD-L1 pathway such that the host immune response to the cancer is improved. This postulate is based on the observations that PD-L1 expression in tumor cells is induced by IFN-γ (Cheng et al, 2007; Dondero et al, 2016; Iwai et al, 2002; Muhlbauer et al, 2006), and IFN-γ signaling is dependent on sphingolipid metabolism (Bajwa et al, 2017; Ottenlinger et al, 2016; Seo, Alexander, & Hahm, 2011; Wakita, Nishimura, Tokura, Furukawa, & Takigawa, 1996). Furthermore, Akt- (Abdelhamed, Ogura, Yokoyama, Saiki, & Hayakawa, 2016; Atefi et al, 2014; Dong et al, 2016; Lastwika et al, 2016; Song et al, 2013; Yang et al, 2017; Zhao et al, 2017), NF-kB- (Gowrishankar et al, 2015), and TNFα- (Wang et al, 2017) signaling induce PD-L1 expression, and all of these pathways are regulated by sphingolipid signaling.…”