Efficacy of an ALDH peptide-based dendritic cell vaccine targeting cancer stem cells.

Cancer immunotherapies may be limited by their failure to target cancer stem cells (CSCs). We previously described an approach to target these cells using a dendritic cell (DC) vaccine primed with lysates of CSCs identified by aldehyde dehydrogenase (ALDH). However, its clinical application is limited by the difficulty of obtaining adequate amounts of tumor from patient to make CSC lysate for vaccine preparation. To address this issue, we evaluated targeting ALDHhigh CSCs using two antigenic peptides derived from ALDH in D5 melanoma model in both protection and therapeutic settings. ALDH 1A1 or 1A3 peptide-DC vaccines primed cytotoxic T lymphocytes (CTLs) that specifically killed ALDHhigh D5 CSCs, with ALDH 1A1 + 1A3 dual peptides-DC vaccine mediating an additive CTL effect compared to single peptide-DC vaccines. In a tumor challenge model, ALDH peptide-DC vaccines induced significant protective immunity suppressing D5 tumor growth with the dual peptides-DC vaccine being superior to each peptide individually. In a therapeutic model, dual peptide-DC vaccine resulted in significant tumor growth suppression with anti-PD-L1 administration significantly augmenting this effect. Immune monitoring studies revealed that ALDH dual peptides-DC vaccination elicited strong T cell (CTL & IFNγ Elispot) and antibody immunity targeting ALDHhigh CSCs, resulting in significant reduction of ALDHhigh D5 CSCs. ALDH dual peptides-DC vaccination plus anti-PD-L1 administration resulted in increased recruitment of CD3+ TILs in the residual tumors and further reduction of ALDHhigh D5 CSCs. ALDH peptide(s)-based vaccine may allow for clinical translation via immunological targeting of ALDHhigh CSCs. Furthermore, this vaccine augments the efficacy of immune checkpoint blockade.

iASPP-Mediated ROS Inhibition Drives 5-Fu Resistance Dependent on Nrf2 Antioxidative Signaling Pathway in Gastric Adenocarcinoma.

AIMS: Inhibitor for the apoptosis-stimulating protein of p53 (iASPP) has been reported to be correlated with 5-fluorouracil (5-Fu) resistance in renal cell carcinoma. Here, we uncover mechanisms of iASPP-Nrf2-ROS regulation of 5-Fu resistance which are important for the development of alternative treatment strategies for gastric adenocarcinoma treatment. METHODS: We analyzed iASPP and Nrf2 through TCGA RNA-seq data, UALCAN analysis, and cBioPortal datasets. Intracellular ROS generation was determined by 2',7'-dichloro-fluorescin diacetate staining. Transwell was used to evaluate the invasion. The expression of iASPP, Nrf2, HO-1, and GSTP1 was tested using western blot. RESULTS: We found that iASPP KD led to an apparent 5-Fu-induced ROS accumulation in MGC803 and SCG790 cells. Accompanied by iASPP KD, Nrf2 was markedly decreased. iASPP-induced ROS inhibition relies on Nrf2, and due to both knocked down iASPP and Nrf2, the level of ROS did not show an obvious difference with Nrf2 KD solely. Similarly, iASPP KD failed to enhance the Nrf2 KD-mediated ROS accumulation after 5-Fu treatment, suggesting that iASPP-induced antioxidative effects related to 5-Fu resistance are partially dependent on Nrf2. Also, the combination of iASPP KD and Nrf2 KD did not show any synergistic effect on apoptosis after 5-Fu treatment in MGC803 and SCG790 cells. Further studies revealed that iASPP KD or Nrf2 KD could decrease the expression of HO-1 and GSTP1. CONCLUSIONS: Our data highlight that iASPP plays a crucial role in the inhibition of 5-Fu-induced apoptosis resistance by removing ROS accumulation in gastric adenocarcinoma, and that the removal of ROS induced by iASPP is Nrf2 signaling dependent.