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.

The Ras/PI3K/ERK signaling network is frequently mutated and overactivated in various human cancers. Focal adhesion kinase (FAK) is commonly overexpressed in several cancer types and has been implicated in treatment resistance mechanisms. A positive feedback loop between Ras, PI3K, the cytoskeleton, and FAK was previously shown to drive Ras signaling excitability. In this study, we investigated the effectiveness of targeting Ras signaling excitability by concurrently inhibiting FAK and PI3K in cervical and pancreatic cancer cells, which depend on activation Ras/PI3K signaling. We found that the combination of FAK and PI3K inhibitors synergistically suppressed the growth of cervical and pancreatic cancer cell lines through increased apoptosis and decreased mitosis. PI3K inhibitors alone caused only a transient suppression of downstream AKT activity and paradoxically increased FAK signaling in cancer cells. The addition of an FAK inhibitor effectively counteracted this PI3K-inhibitor-induced FAK activation. Furthermore, PI3K inhibitors were found to activate multiple receptor tyrosine kinases (RTKs), including insulin receptor, IGF-1R, EGFR, HER2, HER3, AXL, and EphA2. Taken together, our results suggest that FAK inhibition is necessary to counteract the compensatory RTK activation induced by PI3K inhibitors, thereby achieving more effective suppression of cancer cell growth. These findings highlight the therapeutic potential of combined FAK and PI3K inhibition in cancer treatment.