Epithelial Mutant p53 Promotes Resistance to Anti-PD-1-Mediated Oral Cancer Immunoprevention in Carcinogen-Induced Mouse Models

Abstract

Oral squamous cell carcinoma (OSCC) develops through the multistep malignant progression of squamous epithelium. This process can be prevented by PD-1 blockade in a mouse model for oral carcinogenesis. OSCCs exhibit a high incidence of p53 mutations that confer oncogenic gain-of-function (GOF) activities that promote resistance to standard therapies and poor clinical outcomes. To determine whether epithelial p53 mutations modulate anti-PD-1-mediated oral cancer immunoprevention, we generated mouse models for oral carcinogenesis by exposing mice carrying epithelial-specific p53 mutations to the carcinogen 4NQO. Consistent with the oncogenic functions of mutant p53, mice with OSCCs expressing the p53R172H GOF mutation developed higher metastasis rates than mice with loss-of-function (LOF) p53 deletion or with wild-type p53. Throughout oral cancer progression, pre-invasive and invasive lesions showed a gradual increase in T-cell infiltration, recruitment of immunosuppressive regulatory T-cells (Tregs), and induction of PD-1/PD-L1 immune checkpoint proteins. Notably, while PD-1 blockade prevented the development of OSCCs in mice with wild-type p53 or p53 deletion, GOF p53R172H abrogated the immunopreventive effects of anti-PD-1, associated with upregulation of IL17 signaling and depletion of exhausted CD8 cells in the microenvironment of the p53R172H tumors. These findings sustain a potential role for p53 profiling in personalized oral cancer immunoprevention.

Genetic Changes Driving Immunosuppressive Microenvironments in Oral Premalignancy

“…This study not only showed the capacity of the hydrogels to control the release of PD-1 antibody and reduce OPL frequency, but also provided evidence of the role of mutant p53 in the mechanism of immunosuppression in OPLs. Other immunoprevention studies using p53 mutant mice have showed similar results but required 8 doses of parental immunotherapy administration (89,123), compared to a single hydrogel-PD1 dose (88). A recent comprehensive study of patient samples of leukoplakia identified that proliferative leukoplakia predicts a high rate of malignant transformation within 5 years of diagnosis.…”

“…This carcinogenesis model exhibits similar histological, molecular and chromosomal alterations as observed in human oral carcinogenesis ( 86 , 87 ). We and others have recently reported that 4NQO induced oral lesions expressing mutant Trp53 -R172H contain a higher infiltration of FoxP3+ T regulatory cells (Tregs) compared to Trp53 wild-type mice ( 88 , 89 ). It is known that Tregs are suppressors of antitumor responses that disrupt the maturation of dendritic cells (DC) and prevent the activation of CD4 + effector and CD8 + cytotoxic cells in the tumor microenvironment ( 90 ).…”

p53 mutation and deletion contribute to tumor immune evasion

“…PD-L1 expression is regulated by multiple pathways. The gain-of-function mutant p53 upregulated IL-17 signaling and induced the transformation of infiltrating T cells into exhausted CD8 + T cells to counteract the effects of PD-1 inhibitors ( Wang J. et al, 2021 ). Besides, PD-L1 expression is upregulated by IFN-γ induced immune response, and both wt- and mut-p53 work in this process.…”

“…The numbers of cytotoxic T cells, helper T cells, as well as NK cells significantly reduced. Meanwhile, highly immunosuppressive Tregs ( Sallman et al, 2020 ) and M2 macrophages ( Wang et al, 2021 ) are expanded in cases with TP53 mutations.…”

Mass cytometry and transcriptomic profiling reveal PD1 blockade induced alterations in oral carcinogenesis

“…[3][4][5] To assess the efficacy of PD1 blockade in oral precancers, numerous studies have revealed that PD1 blockade can impede the advancement of oral carcinogenesis in the 4-NQO induced mouse model, which is consistent with our findings. [21][22][23][24][25][26][27][28] Nevertheless, PD1 blockade alone is insufficient to halt or even reverse oral carcinogenesis progression. Given that no studies have systematically characterized the TME, we utilized various platforms to delineate PD1 blockade-induced changes within the TME for oral carcinogenesis.…”