Introduction:

Penile Cancer (PeCa) is a rare cancer, and over 90% are squamous cell carcinoma (SCC). The most significant risk factors are human papillomavirus (HPV) infection and phimosis.  Molecular oncogenic pathways between HPV-Positive and HPV-Negative PeCa are thought to be different, but this is difficult to validate because there are few preclinical models of PeCa and no models of HPV-Positive PeCa. Our goal is to establish PeCA patient-derived xenograft (PDX) models to recapitulate tumor architecture and elucidate molecular patterns of HPV-Positive and HPV-Negative pathways for potential therapeutic targets.

Methods:

PeCa specimens from penectomies and inguinal lymph node dissections (ILND) were collected from 2019-2020. Tumor specimens were processed for PDX generation. Tissue was coated in Matrigel and transplanted subcutaneously into NOD SCID gamma (NSG™) mice. Tumor growth was monitored and was harvested at ≈ 1500 m³ for subsequent propagation.  Short tandem repeat (STR) fingerprinting analysis was performed on genomic DNA from PDX tissue and parental patient tumor tissue.  Immunohistochemistry was performed on all PDX models and original patient primary tumors to validate the expression of p16 protein, a surrogate marker for HPV-Positive disease.  For p16 immunohistochemistry, positivity was determined using the scaling system [1], a score of 3 was assessed as positive and a score of ≤2 as negative.  

Results:

5 PDXs were established from tissue from 4 patients. Age, race, and type of surgery were determined (Table 1).  SCC histology was confirmed in all patients, 2 patients with different variants: basaloid and verrucous. For pathological staging, 2 patients were pT3N3Mx, 1 was pT2N1M0, and 1 was pT3Nx. One ILND had no evidence of disease.  2 PDX models (MDAPe3 and MDAPe7) were derived from two specimens from the same patient (1 pre-treatment, 1 post-treatment). All models were matched to the patient's primary tumor by STR fingerprinting analysis and SCC histology (Figure 1). 3 PDX models are currently in passage 3 and 3 PDXs were p16 positive. HPV genotyping in p16 positive PDX and patient tissue is underway.

Conclusion:

Our study established 5 PeCa PDX models with retained histological features to the patient's tumor, including 3 PDXs confirmed as p16 positive.

Funding: Supplement to U54 CA96300 ; NHI/NCI Cancer Center Support Grant PA30CA016672