RESUMO
Tyrosine kinase inhibitors (TKIs) that block the vascular endothelial growth factor receptors (VEGFRs) disrupt tumor angiogenesis but also have many unexpected side-effects that impact tumor cells directly. This includes the induction of molecular markers associated with senescence, a form of cellular aging that typically involves growth arrest. We have shown that VEGFR TKIs can hijack these aging programs by transiently inducting senescence-markers (SMs) in tumor cells to activate senescence-associated secretory programs that fuel drug resistance. Here we show that these same senescence-mimicking ('senomimetic') VEGFR TKI effects drive an enhanced immunogenic signaling that, in turn, can alter tumor response to immunotherapy. Using a live-cell sorting method to detect beta-galactosidase, a commonly used SM, we found that subpopulations of SM-expressing (SM+) tumor cells have heightened interferon (IFN) signaling and increased expression of IFN-stimulated genes (ISGs). These ISG increases were under the control of the STimulator of INterferon Gene (STING) signaling pathway, which we found could be directly activated by several VEGFR TKIs. TKI-induced SM+ cells could stimulate or suppress CD8 T-cell activation depending on host:tumor cell contact while tumors grown from SM+ cells were more sensitive to PD-L1 inhibition in vivo, suggesting that offsetting immune-suppressive functions of SM+ cells can improve TKI efficacy overall. Our findings may explain why some (but not all) VEGFR TKIs improve outcomes when combined with immunotherapy and suggest that exploiting senomimetic drug side-effects may help identify TKIs that uniquely 'prime' tumors for enhanced sensitivity to PD-L1 targeted agents.
RESUMO
Cadmium (Cd) is a toxic heavy metal, exposure to which leads to adverse health effects including chronic kidney damage. Tremendous efforts have been explored in identifying safe chelating agents for removing accumulated Cd from kidney, but with limited success owing to their associated side effects and the ineffectiveness in eliminating Cd. A newly developed chelating agent, sodium (S)-2-(dithiocarboxylato((2S,3 R,4R,5 R)-2,3,4,5,6-pentahydroxyhexyl) amino)-4(methylthio)butanoate (GMDTC), has been shown to effectively mobilize Cd from kidney. However, the mechanism(s) of removal are unclear, while it has been hypothesized that renal glucose transporters potentially play key roles mainly because GMDTC contains an open chain glucose moiety. To test this hypothesis, we utilized the CRISPR/Cas9 technology and human kidney tubule HK-2 cells, and constructed sodium-dependent glucose transporter 2 (SGLT2) or glucose transporter 2 (GLUT2) gene knockout cell lines. Our data showed that GMDTC's ability in removing Cd from HK-2 cells was significantly reduced both in GLUT2-/- or SGLT2-/- cells, with a removal ratio reduced from 28.28% in the parental HK-2 cells to 7.37% in GLUT2-/- cells and 14.6% in SGLT2-/- cells. Similarly, knocking out the GLUT2 or SGLT2 led to a compromised protective effect of GMDTC in reducing cytotoxicity of HK-2 cells. This observation was further observed in animal studies, in which the inhibition of GLUT2 transporter by phloretin treatment resulted in reduced efficiency of GMDTC in removing Cd from the kidney. Altogether, our results show that GMDTC is safe and highly efficient in removing Cd from the cells, and this effect is mediated by renal glucose transporters.