Combined Point Mutation in a Single Allele of the TP53 Gene Potentiates the Oncogenic and Transcriptional Properties of TP53 in Lung Cancer.

Although multi-hit TP53 mutations correlate with rapid disease progression, treatment resistance, recurrence, and poor survival, their occurrence within an individual TP53 gene molecule (cbTP53) remains unexplored. Consequently, the impact of cbTP53 on protein conformation, transcriptional architecture, and oncogenicity is unknown. We show that cbTP53 with combined mutations (Y220C+R248Q+R282Q) does not drastically alter local stability or structural conformation, but significantly affects TP53 binding to DNA promoters comparing it to a single Y220C mutation. Functionally, cbTP53 promotes divergent cellular phenotypes, characterized by enhanced cell proliferation, increased formation of multicellular tumor spheroids (MCTS) and spheroids, altered responses to chemotherapeutic drugs (e.g., cisplatin, carboplatin) and p53 inhibitors (e.g., MB710, PK11007), and increased resistance to carboplatin-induced DNA damage. Furthermore, cbTP53 is linked to distinct immune cell profiles (e.g., CD4+ and CD8+ T cells, nature killer cells, dendritic cells), more circulating tumor cells, a higher rate of tumor engraftment, and an increased number of lung tumor nodules. Mechanistically, introduction of R248Q/R282Q mutations changes 42.7% of Y220C-regulated gene expression, and cbTP53 (vs Y220C) owns a distinctive transcriptomic signature with 1,004 up- and 1,747 down-regulated genes. cbTP53 shows the enhanced binding affinity in the promoters of inflammatory cytokines, leading to their increased production. This study establishes causative and mechanistic links of cbTP53 to lung aggressive cancer metastasis and disease progression, providing a novel perspective on the genetics of TP53 mutations in cancer.