Establishment and characterization of a penile cancer cell line, penl1, with a deleterious TP53 mutation as a paradigm of HPV-negative penile carcinogenesis

Systemic treatment of penile squamous cell carcinoma-hurdles and hopes of preclinical models and clinical regimens: a narrative review

Despite contemporary research efforts, the prognosis of penile squamous cell carcinoma (PeSCC) has not significantly improved over the past decade. Despite frequently encountered patient-related delayed medical consultations impairing outcomes, several other aspects contribute to the lack of advancement in the treatment of this condition. One essential reason is that translational research, a prerequisite for the clinically successful disease management, is still at an early stage in PeSCC as compared to many other malignancies. Preclinical experimental models are indispensable for the evaluation of tumor biology and identification of genomic alterations. However, since neither commercial PeSCC cell lines are available nor xenograft models sustainably established, such analyses are challenging in this field of research. In addition, systemic therapies are less effective and toxic without decisive breakthroughs over recent years. Current systemic management of PeSCC is based on protocols that have been investigated in small series of only up to 30 patients. Thus, there is an unmet medical need for new approaches necessitating research efforts to develop more efficacious systemic strategies. This review aims to highlight the current state of knowledge in the molecular alterations involved in the etiology and ensuing steps for cancer progression, existing preclinical models of translational research, clinically relevant systemic protocols, and ongoing clinical trials.

Penile Cancer-Derived Cells Molecularly Characterized as Models to Guide Targeted Therapies

Penile cancer (PeCa) is a common disease in poor and developing countries, showing high morbidity rates. Despite the recent progress in understanding the molecular events involved in PeCa, the lack of well-characterized in vitro models precludes new advances in anticancer drug development. Here we describe the establishment of five human primary penile cancer-derived cell cultures, including two epithelial and three cancer-associated fibroblast (CAF) cells. Using high-throughput genomic approaches, we found that the epithelial PeCa derived- cells recapitulate the molecular alterations of their primary tumors and present the same deregulated signaling pathways. The differentially expressed genes and proteins identified are components of key oncogenic pathways, including EGFR and PI3K/AKT/mTOR. We showed that epithelial PeCa derived cells presented a good response to cisplatin, a common therapeutic approach used in PeCa patients. The growth of a PeCa-derived cell overexpressing EGFR was inhibited by EGFR inhibitors (cetuximab, gefitinib, and erlotinib). We also identified CAF signature markers in three PeCa-derived cells with fibroblast-like morphology, indicating that those cells are suitable models for PeCa microenvironment studies. We thus demonstrate the utility of PeCa cell models to dissect mechanisms that promote penile carcinogenesis, which are useful models to evaluate therapeutic approaches for the disease.

Penile cancer

Penile squamous cell carcinoma (PSCC) is a rare cancer with orphan disease designation and a prevalence of 0.1-1 per 100,000 men in high-income countries, but it constitutes up to 10% of malignancies in men in some African, Asian and South American regions. Risk factors for PSCC include the absence of childhood circumcision, phimosis, chronic inflammation, poor penile hygiene, smoking, immunosuppression and infection with human papillomavirus (HPV). Several different subtypes of HPV-related and non-HPV-related penile cancers have been described, which also have different prognostic profiles. Localized disease can be effectively managed by topical therapy, surgery or radiotherapy. As PSCC is characterized by early lymphatic spread and imaging is inadequate for the detection of micrometastatic disease, correct and upfront surgical staging of the inguinal lymph nodes is crucial in disease management. Advanced stages of disease require multimodal management. Optimal sequencing of treatments and patient selection are still being investigated. Cisplatin-based chemotherapy regimens are the mainstay of systemic therapy for advanced PSCC, but they have poor and non-durable responses and high rates of toxic effects, indicating a need for the development of more effective and less toxic therapeutic options. Localized and advanced penile cancers and their treatment have profound physical and psychosexual effects on the quality of life of patients and survivors by altering sexual and urinary function and causing lymphoedema.

Experimental Models for Studying HPV-Positive and HPV-Negative Penile Cancer: New Tools for An Old Disease

Simple Summary

Penile cancer is an uncommon and understudied malignancy that is most commonly diagnosed in developing countries. Therapeutic advances have been slow, in part due to the lack of in vitro and in vivo models for testing new drugs before performing clinical trials. Recently, this difficulty has been partly overcome and multiple new pre-clinical models were reported. These important developments will help develop new therapies for penile cancer patients. The present review summarizes and discusses the available data concerning the pre-clinical models of penile cancer and their uses. Comparisons are drawn between different models, allowing researchers to choose the most adequate setting for their experiments. The remaining gaps in this array of penile cancer models are also discussed, in particular the lack of models for studying metastatic disease and cell lines representing tumors associated with human papillomavirus.

Abstract

Penile cancer is an uncommon malignancy that occurs most frequently in developing countries. Two pathways for penile carcinogenesis are currently recognized: one driven by human papillomavirus (HPV) infection and another HPV-independent route, associated with chronic inflammation. Progress on the clinical management of this disease has been slow, partly due to the lack of preclinical models for translational research. However, exciting recent developments are changing this landscape, with new in vitro and in vivo models becoming available. These include mouse models for HPV⁺ and HPV⁻ penile cancer and multiple cell lines representing HPV⁻ lesions. The present review addresses these new advances, summarizing available models, comparing their characteristics and potential uses and discussing areas that require further improvement. Recent breakthroughs achieved using these models are also discussed, particularly those developments pertaining to HPV-driven cancer. Two key aspects that still require improvement are the establishment of cell lines that can represent HPV⁺ penile carcinomas and the development of mouse models to study metastatic disease. Overall, the growing array of in vitro and in vivo models for penile cancer provides new and useful tools for researchers in the field and is expected to accelerate pre-clinical research on this disease.

HPV16 induces penile intraepithelial neoplasia and squamous cell carcinoma in transgenic mice: first mouse model for HPV-related penile cancer

Penile cancer is an under-studied disease that occurs more commonly in developing countries and 30-50% of cases show high-risk human papillomavirus (HPV) infection. Therapeutic advances are slow, largely due to the absence of animal models for translational research. Here, we report the first mouse model for HPV-related penile cancer. Ten-week-old mice expressing all the HPV16 early genes under control of the cytokeratin 14 (Krt14) gene promoter and matched wild-type controls were exposed topically to dimethylbenz(a)anthracene (DMBA) or vehicle for 16 weeks. At 30 weeks of age, mice were sacrificed for histological analysis. Expression of Ki67, cytokeratin 14, and of the HPV16 oncogenes E6 and E7 was confirmed using immunohistochemistry and quantitative PCR, respectively. HPV16-transgenic mice developed intraepithelial lesions including condylomas and penile intraepithelial neoplasia (PeIN). Lesions expressed cytokeratin 14 and the HPV16 oncogenes E6 and E7 and showed deregulated cell proliferation, demonstrated by Ki67-positive supra-basal cells. HPV16-transgenic mice exposed to DMBA showed increased PeIN incidence and squamous cell carcinoma. Malignant lesions showed varied histological features closely resembling those of HPV-associated human penile cancers. Wild-type mice showed no malignant or pre-malignant lesions even when exposed to DMBA. These observations provide the first experimental evidence to support the etiological role of HPV16 in penile carcinogenesis. Importantly, this is the first mouse model to recapitulate key steps of HPV-related penile carcinogenesis and to reproduce morphological and molecular features of human penile cancer, providing a unique in vivo tool for studying its biology and advancing basic and translational research. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Up-regulation of indoleamine 2,3-dioxygenase 1 (IDO1) expression and catalytic activity is associated with immunosuppression and poor prognosis in penile squamous cell carcinoma patients

Background

Indoleamine 2,3‐dioxygenase 1 (IDO1) and tryptophan (Trp) catabolism have been demonstrated to play an important role in tumor immunosuppression. This study examined the expression and catalytic activity of IDO1 in penile squamous cell carcinoma (PSCC) and explored their clinical significance.

Methods

IDO1 expression level, serum concentrations of Trp and kynurenine (Kyn) were examined in 114 PSCC patients by immunohistonchemistry and solid‐phase extraction‐liquid chromatography‐tandem mass spectrometry. The survival was analyzed using Kaplan‐Meier method and the log‐rank test. Hazard ratio of death was analyzed via univariate and multivariate Cox regression. Immune cell types were defined by principal component analysis. The correlativity was assessed by Pearson's correlation analysis.

Results

The expression level of IDO1 in PSCC cells was positively correlated with serum Kyn concentration and Kyn/Trp radio (KTR; both P < 0.001) but negatively correlated with serum Trp concentration (P = 0.001). Additionally, IDO1 up‐regulation in cancer cells and the increase of serum KTR were significantly associated with advanced N stage (both P < 0.001) and high pathologic grade (P = 0.008 and 0.032, respectively). High expression level of IDO1 in cancer cells and serum KTR were associated with short disease‐specific survival (both P < 0.001). However, besides N stage (hazard radio [HR], 6.926; 95% confidence interval [CI], 2.458‐19.068; P < 0.001) and pathologic grade (HR, 2.194; 95% CI, 1.021‐4.529; P = 0.038), only serum KTR (HR, 2.780; 95% CI, 1.066‐7.215; P = 0.036) was an independent predictor for PSCC prognosis. IDO1 expression was positively correlated with the expression of interferon‐γ (IFNγ, P < 0.001) and immunosuppressive markers (programmed cell death protein 1, cytotoxic T‐lymphocyte‐associated protein 4 and programmed death‐ligand 1 and 2; all P < 0.05), and the infiltration of immune cells (including cytotoxic T lymphocytes, regulatory T lymphocytes, tumor‐associated macrophages, and myeloid‐derived suppressor cells; all P < 0.001) in PSCC tissues. Furthermore, the expression of IDO1 was induced by IFNγ in a dose‐dependent manner in PSCC cells.

Conclusions

IFNγ‐induced IDO1 plays a crucial role in immunoediting and immunosuppression in PSCC. Additionally, serum KTR, an indicator of IDO1 catabolic activity, can be utilized as an independent prognostic factor for PSCC.

Aberrant CEACAM19 expression is associated with metastatic phenotype in penile cancer

Objective

A greater knowledge of the mechanisms of the pathogenesis of penile cancers may assist in the development of more tailored targeted therapy. Herein, we aimed to evaluate the expression of CEACAM19 in penile cancer and to explore its regulatory mechanisms.

Material and methods

This retrospective study enrolled 64 penile cancer patients who underwent penectomy between 2011 and 2015. CEACAM19 expression in tissues was detected by immunohistochemistry, which was analyzed in association with clinicopathological parameters. Kaplan–Meier analysis was performed to evaluate the relationship between CEACAM19 expression and prognosis of patients with penile cancer. Cell Counting Kit-8 assay and clonogenic assay were used to evaluate the cell viability and tumorigenic potential of penile cancer cell line, respectively; wound healing assay and transwell invasion assay were conducted to evaluate the effect of CEACAM19 depletion on cell migration and invasion in penile cancer cells; CEACAM19 protein expression was analyzed by Western blotting. Culture supranatant matrix metalloproteinase 2/9 (MMP2/9) was detected by ELISA.

Results

CEACAM19 was differentially expressed in non-cancerous and penile cancer tissues. Over-expression of CEACAM19 was significantly associated with nodal and distant metastasis, and predicted unfavorable cancer-specific survival in penile cancer. Depletion of CEACAM19 expression suppressed cell proliferation, reduced colony formation, and attenuated cell migration and invasion in Penl1 cells. Furthermore, knockdown of CEACAM19 expression attenuated the levels of p-Smad2/3 and reduced secretion of MMP2/9 in Penl1 cells. The effects of CEACAM19 might result from its function in regulating the Smad2/3 activation, as inhibition on Smad2/3 activation suppressed cell migration and invasion and reduced MMP2/9 secretion in Penl1 cells.

Conclusion

Over-expression of CEACAM19 might serve as a potential prognostic biomarker for clinical management of penile cancer. Strategies targeting CEACAM19-regulated signaling pathways may have a therapeutic benefit in penile cancer.

Elevated serum LAMC2 is associated with lymph node metastasis and predicts poor prognosis in penile squamous cell carcinoma

Purpose

Molecular biomarkers, especially serologic factors, have been widely applied in cancer diagnosis and patient follow-up. However, there are few valuable prognostic factors in penile squamous cell carcinoma (PSCC). Here, the authors investigated whether laminin gamma 2 (LAMC2) expression, especially serum LAMC2 (sLAMC2) level, was a suitable prognostic factor that could aid in the prediction of survival in PSCC.

Patients and methods

This study included 114 PSCC patients. Reverse transcription-quantitative polymerase chain reaction, Western blotting, and immunohistochemistry were performed to detect LAMC2 expression; enzyme-linked immunosorbent assays were used to test sLAMC2 concentration; and a Transwell assay and an in vivo experiment in nude mice were used to test PSCC cell migration, invasion, and metastasis. The chi-squared test was used to analyze the association between LAMC2 level and clinical parameters, the Cox proportional hazards regression model was used to evaluate the hazard ratio for death, and Kaplan–Meier analysis with a log-rank test was used for the survival analysis.

Results

LAMC2 was overexpressed in PSCC tissues, and the LAMC2 expression level was higher in metastatic lymph node (LN) tissues than in primary cancer tissues; moreover, the LAMC2 levels in primary cancer tissues and sLAMC2 were higher in patients with LN metastasis than in those without LN metastasis. Upregulated LAMC2 facilitated the migration, invasion, and epithelial-to-mesenchymal transition of PSCC cells in vitro and promoted LN metastasis of PSCC cells in nude mice. Elevated LAMC2 levels were strongly correlated with advanced clinicopathologic parameters, especially LN metastasis, in PSCC patients and predicted shorter disease-specific survival. The predictive value of sLAMC2 is superior to that of C-reactive protein and squamous cell carcinoma antigen previously reported in PSCC patients, and a stratification analysis revealed that the level of sLAMC2 had a higher predictive value for disease-specific survival in early penile cancer (especially at the N_0/X stage) than in later-stage penile cancer.

Conclusion

These findings suggest that sLAMC2 is a potential serologic prognostic marker in PSCC and could aid in risk stratification in early-stage PSCC patients.

Molecular characterization and integrative genomic analysis of a panel of newly established penile cancer cell lines

Cell line models are essential tools to study the molecular mechanisms underlying tumor initiation and progression. There are limited treatment options for penile squamous cell carcinoma (PSCC), accounting for 1–2% of male tumors in developing countries, and limited progress in preclinical research in PSCC due to lacking available models with identified genomic characteristics. Here, biological and molecular characteristics and whole-genomic alterations were analyzed in a panel of PSCC cell lines newly established in our laboratory. These cell lines were all human papillomavirus (HPV)-negative, epithelial-like, immortalized, and tumorigenic in nude mice, whereas they displayed different proliferation, migration and invasion capacities in vitro, and tumorigenic ability in nude mice. They were all cisplatin sensitive, anti-EGFR therapy resistant, and androgen irresponsive. Whole-genomic sequecing analysis revealed that transition mutations (C:G>T:A and T:A>C:G) were the most common substitution types in these cell lines, whereas ERCC5, TP53, PTH1, CLTCL1, NOTCH2, MAP2K3, CDK11A/B, USP6, ADCH5, BCLAF1, CDKN2A, FANCD2, HRAS, and NOTCH1 were the most frequently altered genes. Amplifications of MYC, PLAG1, NCOA2, RUNX1T1, COX6C, and EGFR and losses of FBXW7, TET2, XPC, and FANCE were frequently observed in cell lines. The exomic variations between cell lines and their corresponding cancer tissues were highly consistent. Genetic variations were mainly involved in the MAPK, Jak-STAT, TGF-beta, Notch, and apoptosis signaling pathways. Conclusively, these panel of PSCC cell lines established in our laboratory harbor some common or specific biological characteristics and genomic variations, and they may serve as optimal models to investigate the molecular mechanisms underlying the progression, metastasis, relapses, and treatment resistance of PSCC and to develop effective treatment strategy.

Tumor PD-L1 expression is correlated with increased TILs and poor prognosis in penile squamous cell carcinoma

Despite its rare incidence worldwide, penile squamous cell carcinoma (PeSCC) still presents with significant morbidity and mortality due to the limited treatment options for advanced patients, especially those in developing countries. The program death-1 (PD-1)/PD-1 ligand (PD-L1) axis has been demonstrated to play an important role in tumor immune escape, and immunotherapies targeting this pathway have shown great success in certain cancer types. Here, we analyzed the expression pattern of PD-L1 in tumor cells and tumor-infiltrating lymphocytes (TILs) in PeSCC with a multi-center cohort. We found that the majority of PeSCCs (53.4%) were PD-L1-positive and that high PD-L1 expression in tumor cells was associated with a poor prognosis. Notably, PD-L1 expression in tumor cells was significantly associated with the extent of TILs and CD8⁺ TILs. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) showed that PD-L1 was positively correlated with interferon-gamma (IFNγ) and CD8⁺ gene expression. Moreover, we defined the constitutive and inducible surface expression of PD-L1 in newly established primary PeSCC cell lines. Interestingly, two PeSCC cell lines had high intrinsic PD-L1 expression. Another cell line showed low PD-L1 expression, but the PD-L1 expression could be induced by IFNγ stimulation. Overall, our data showed that high PD-L1 expression in penile tumor cells indicated a poor prognosis. The upregulation of PD-L1 in PeSCC included both extrinsic and intrinsic mechanisms. These findings indicated that the PD-1/PD-L1 axis might be a potential therapeutic target for patients with penile squamous cell carcinoma.