Since 2016 the WHO has recommended the classification of PSCC as HPV-related (HPV+) and HPV-unrelated (HPV-) PSCC, based on the differences in carcinogenesis and the better 5-year disease-specific survival in HPV+ PSCC.2,3 Nevertheless, the latter shows similar rates of pathologically confirmed positive lymph nodes and substantially higher rates of poorly differentiated disease compared to HPV-PSCC. Differences seen between HPV+ and HPV-PSCC are not well understood and differences in cisplatin-responsiveness may stem from distinct molecular mechanisms. It has been shown that 75% of HPV- PSCC harbour TP53 loss-of-function (LOF) mutations while only 10% of HPV+ PSCC carry this mutation,4 therefore we hypothesized that the guardian of our genome might be the driver of poor prognosis.
To meet the pressing needs of this devastating disease, we used single-cell RNA and T-cell receptor (TCR) sequencing along with targeted genomics to establish the first transcriptomic atlas of penile cancer, stratified by HPV and TP53 mutations.5 Six healthy penile samples, 6 HPV+ TP53 wild type (WT), 6 HPV-TP53WT and 4 TP53 LOF treatment-naïve samples were included. Single-cell RNA and T-cell receptor (TCR) sequencing revealed 14 major cell types and 65 cellular subtypes within 83.682 single cells. The prognostic validity of our patient strata was confirmed using Kaplan Meier estimates in an independent cohort (n=541) showing that patients with a TP53LOF mutation have a tremendously poor prognosis irrespective of HPV status. Hence p53 immunohistochemistry, as a highly specific correlate for TP53 mutation might play a role as a prognostic biomarker and supersede HPV-status.
In this study, we explored biological pathways and deciphered molecular distinctions between these patient groups. Our data reveal the molecular justification underlying poor prognosis in TP53 LOF patients as these tumors are characterized by a partial epithelial-to-mesenchymal (pEMT) phenotype histologically confirmed as tumor budding which is a marker of metastases and poor prognosis. These tumors also exhibit a tumor-supportive, immune-evasive TME with high angiogenic features, promoting invasiveness. As these patients fare poorly and show signatures related to therapy resistance, we recommend exploring combinatorial therapies and routinely adopting immunohistochemical p53 assessment, to support clinical decision-making and patient counseling.
On the other hand, HPV+TP53WT patients have the ability to mirror normal epithelial maturation into cornified and superficial ridge cells. These differentiated cells exhibit an abundance of antibody-drug conjugate (ADC) targets, hypothetically sensitizing these patients to ADC and potentially allowing them to avoid toxic chemotherapy regimens.
Lastly, HPV-TP53WT patients showed high levels of C1QC+ tumor-associated macrophages which has been correlated with abundant expression of exhausted CD8 T cells. Remarkably, they displayed upregulation of immune checkpoint receptors such as PD1, LAG3, and CTLA4, confirming their role as inducers of exhaustion. This immune-exhausted phenotype combined with high clonality of the TCR suggests that these patients might benefit from immune checkpoint blockade therapies.
In conclusion: we challenged the currently used stratification of penile cancer based on HPV. By incorporating TP53 mutations in the stratification framework, we were able to explain why some HPV+ patients exhibit a more aggressive phenotype than expected. Clinically, we call for optimization of stratification systems with regular assessment of p53 and p16 immunohistochemistry in penile cancer. Early stratification of PSCC patients could allow more accurate prediction of prognosis and therapy response and may enable personalized treatment decisions. Further validation of these signatures is needed to improve patient outcomes in this rare disease with limited treatment options.
Written by: Laura Elst,1,2,3 Maarten Albersen2,3
- VIB-KU Leuven, Center for Cancer Biology, Laboratory of Translational Genetics, Leuven, Belgium.
- Department of Urology, University Hospitals Leuven, Leuven, Belgium.
- Department of development and regeneration, KU Leuven, Leuven, Belgium.
- A. Thomas et al., Penile cancer. Nature Reviews Disease Primers 7, (2021).
- R. S. Djajadiningrat et al., Human papillomavirus prevalence in invasive penile cancer and association with clinical outcome. J Urol 193, 526-531 (2015).
- J. Chahoud et al., Prognostic Significance of p16 and Its Relationship with Human Papillomavirus Status in Patients with Penile Squamous Cell Carcinoma: Results of 5 Years Follow-Up. Cancers (Basel) 14, (2022).
- L. Elst et al., Establishment and Characterization of Advanced Penile Cancer Patient-derived Tumor Xenografts: Paving the Way for Personalized Treatments. Eur Urol Focus, (2022).
- L. Elst et al., Single-cell Atlas of Penile Cancer Reveals TP53 Mutations as a Driver of an Aggressive Phenotype, Irrespective of Human Papillomavirus Status, and Provides Clues for Treatment Personalization. Eur Urol, (2024)..