Even with the prolific clinical use of next-generation cancer therapeutics, many tumors remain unresponsive or become refractory to therapy, creating a medical need. In cancer, DCs are indispensable for T cell activation, so there is a restriction on cytotoxic T cell immunity if DCs are not present in sufficient numbers in the tumor and draining lymph nodes to take up and present relevant cancer antigens. To address this bottleneck, we developed a therapeutic based on albumin fused with FMS-related tyrosine kinase 3 ligand (Alb-Flt3L) that demonstrated superior pharmacokinetic properties compared with Flt3L, including significantly longer half-life, accumulation in tumors and lymph nodes, and cross-presenting-DC expansion following a single injection. We demonstrated that Alb-Flt3L, in combination with standard-of-care chemotherapy and radiation therapy, serves as an in situ vaccination strategy capable of engendering polyclonal tumor neoantigen–specific immunity spontaneously. In addition, Alb-Flt3L–mediated tumor control synergized with immune checkpoint blockade delivered as anti–PD-L1. The mechanism of action of Alb-Flt3L treatment revealed a dependency on Batf3, type I IFNs, and plasmacytoid DCs. Finally, the ability of Alb-Flt3L to expand human DCs was explored in humanized mice. We observed significant expansion of human cross-presenting-DC subsets, supporting the notion that Alb-Flt3L could be used clinically to modulate human DC populations in future cancer therapeutic regimens.

Background: Ly6C expression in naïve CD8+ T cells plays a crucial role in enhancing their effector activity, suggesting potential implications for cancer immunotherapy. This study investigates the functional impact of Ly6C expression on CD8⁺ T cells and explores albumin-conjugated IFNβ (Alb-IFNβ) as a strategy to modulate Ly6C expression and improve cancer vaccine efficacy. Methods: We analyzed the functional differences between Ly6C high-expressing (Ly6C^hi) and Ly6C low-expressing (Ly6C^lo) naïve CD8⁺ T cells in tumor suppression. To assess the role of type I interferon signaling, we administered Alb-IFNβ in C57BL/6J and IFNAR^−/− mice and measured Ly6C expression in CD8⁺ T cells. The therapeutic potential of Alb-IFNβ was further evaluated in combination with a vaccinia virus encoding the HPV-16 E7 antigen (CRT-E7 vaccine) in a syngeneic TC-1 tumor model, assessing tumor growth, survival, and antigen-specific CD8⁺ T cell responses. Results: Naïve CD8⁺ T cells with elevated Ly6C expression exhibited enhanced tumor-suppressive capacity and required lower activation thresholds for effector function. Alb-IFNβ treatment selectively increased Ly6Chi naïve CD8⁺ T cells in C57BL/6J mice but not in IFNAR^−/− mice, confirming type I interferon’s role in Ly6C regulation. Combining Alb-IFNβ pretreatment with the CRT-E7 vaccine significantly enhanced antigen-specific CD8⁺ T cell immunity, reducing tumor growth and prolonging survival in TC-1 tumor-bearing mice. Conclusions: Our findings suggest that Alb-IFNβ may enhance the antitumor activity of naïve CD8⁺ T cells by modulating Ly6C expression. Alb-IFNβ could potentially improve the efficacy of HPV vaccinia-based cancer vaccines, warranting further investigation as an adjuvant strategy in cancer immunotherapy.

Human papillomavirus (HPV) remains a global health concern because it contributes to the initiation of various HPV-associated cancers such as anal, cervical, oropharyngeal, penile, vaginal, and vulvar cancer. In HPV-associated cancers, oncogenesis begins with an HPV infection, which is linked to the activation of the Janus protein tyrosine kinase (JAK)/STAT signaling pathway. Various STAT signaling pathways, such as STAT3 activation, have been well documented for their tumorigenic role, yet the role of STAT1 in tumor formation remains unclear. In the current study, STAT1^−/− mice were used to investigate the role of STAT1 in the tumorigenesis of a spontaneous HPV E6/E7-expressing oral tumor model. Subsequently, our candidate HPV DNA vaccine CRT/E7 was administered to determine whether the STAT1^−/− host preserves a therapeutic-responsive tumor microenvironment. The results indicated that STAT1^−/− induces robust tumorigenesis, yet a controlled tumor response was attained upon CRT/E7 vaccination. Characterizing this treatment effect, immunological analysis found a higher percentage of circulating CD4+ and CD8+ T cells and tumor-specific cytotoxic T cells. In addition, a reduction in exhaustive lymphocyte activity was observed. Further analysis of a whole-cell tumor challenge affirmed these findings, as spontaneous tumor growth was more rapid in STAT1^−/− mice. In conclusion, STAT1 deletion accelerates tumorigenesis, but STAT1^−/− mice maintains immunocompetency in CRT/E7 treatments.