Constitutive p38 activation in DCs enhances antitumor immune responses and increases survival. (A) Groups of 5 mice were injected with OVA-expressing EG7 lymphoma cells. After tumor growth, mice were vaccinated with immature DCs (only DC), DCs loaded with class I OVA peptide (DC + OVA PEP), LPS-matured peptide-loaded (DC + OVA PEP + LPS), or with DCs transduced with lentivectors coexpressing the inactive MKK6 K82A mutant or MKK6EE with IiOVA. Tumor growth was quantified as tumor scores and plotted as a function of days after inoculation of EG7 cells. Mice were killed when tumor scores were higher than 150 to 160 mm². (B) The graph on the left shows a Kaplan-Meier survival plot of mice vaccinated with immature DCs (DC), peptide-loaded DCs (DCp), LPS-matured peptide-loaded DCs (DCp LPS), DCs coexpressing MKK6K82A with IiOVA (K82A), and DCs coexpressing MKK6 EE with IiOVA (MKK6EE). A log-rank test showed significant differences in survival between the groups (P = .03). The column graph on the right shows mean survival days (y-axis) in each vaccination group (x-axis). Each column represents the mean with error bars (SD). Relevant statistical comparisons are shown within each graph. *, significant differences (P< 0.05); **, very significant differences (P < .01). (C) OVA-specific immunoblot from representative tumors of mice vaccinated with immature DCs or peptide-loaded DCs (DCp), or from tumors arising after previous regression in groups vaccinated with DCs coexpressing MKK6EE with IiOVA (DC MKK6), DCs coexpressing MKK6 K82A with IiOVA (DC K82A), or with LPS-matured peptide-loaded DCs (DCp LPS). (D) FLAG-specific immunoblots show expression of the indicated activators together with NY-ESO from dual lentivectors encoding activators under the control of SFFV promoter, and NY-ESO under the control of ubiquitin promoter. Groups of 5 mice were vaccinated with the indicated dual lentivectors. NY-ESO-specific CD8 T cells in spleen were evaluated by IFN-γ ELISPOT, and represented as column graphs. Each column shows the mean together with error bars (SD). GFP represents lentivectors expressing only GFP; K82A, MKK6, MEK, and IRF3 represent lentivectors coexpressing MKK6 K82A, MKK6EE, MEK1 ΔNES AA, or IRF3 2D with NY-ESO.