E2F1 Signalling is Predictive of Chemoresistance and Lymphogenic Metastasis in Penile Cancer: A Pilot Functional Study Reveals New Prognostic Biomarkers.

BACKGROUND

For penile cancer (PC) there are no known molecular predictors of lymphatic spread and/or chemoresistance.

OBJECTIVE

To identify functional biomarkers that can predict malignant progression and treatment responsiveness.

DESIGN, SETTING, AND PARTICIPANTS: We used four patient-derived PC cell lines and measured invasion and capillary tube formation, chemoresponsiveness, and mRNA and protein expression. Data were further validated in E2F1 transcription factor knockdown and overexpression experiments. We quantified E2F1 transcript levels in a set of nonmetastatic tumours (NM), metastasised primary tumours (PT), and lymph node metastases (M) from 24 patients. E2F1 immunohistochemistry was performed in another set of 13 PC biopsies.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Relationships between different parameters were analysed using Student t tests. Transcript levels in patient samples were compared using Mann-Whitney U tests. Significance was set at p<0.05.

RESULTS AND LIMITATIONS

In cell lines established from lymph node metastases, E2F1 was more abundantly expressed, pRB was inactivated, and CDK2, CDK4, and cyclins D and E were elevated in comparison to cells from primary PC. Overexpression of E2F1 enhanced migratory capacity and lymphatic endothelial tubule formation, while depletion reduced invasiveness and increased chemosensitivity. VEGFR-3 and VEGF-C and mesenchymal markers were upregulated by high E2F1. E2F1 was clearly upregulated in infiltrative and metastatic primary tumours and metastases (NM vs PT, p<0.05; NM vs M, p<0.0005). E2F1 Quick scores increased from grade I to grade III tumours. A limitation of the study is the small number of patients.

CONCLUSIONS

E2F1 is a driver of invasion and lymphatic dissemination and promotes chemoresistance. E2F1-related biomarkers might assist in stratifying PC patients for different treatment regimens.

PATIENT SUMMARY

The availability of penile cancer cell lines allows molecular research on the mechanisms underlying metastasis and chemotherapy. A critical pathway involved in both features has been identified and may lead to better patient stratification for treatment selection.