Penile cancer is a malignant tumor originating from the mucous membrane of the head, coronal sulcus, inner foreskin, and the skin of the penis(MM et al., 2016). It is the most common malignant tumor of the penis, accounting for over 90% of penile tumors. The most common pathological type of penile cancer is squamous cell carcinoma, which accounts for approximately 95% of penile cancers, whereas the other types are rare. It occurs in the inner foreskin plate and head of the penis, it and has a variety of histological subtypes that are pathologically similar to squamous cell carcinoma of other tissue origins(N & Z, 2012). For early-stage patients, surgical excision of the lesion is the primary and most effective treatment. Patients with advanced penile cancer and distant metastases, who were not suitable for surgical resections, should consider chemotherapy, and platinum and paclitaxel-based chemotherapy combined with inguinal lymph node dissection is the main treatment for advanced stages of this disease(Y et al., 2017). However, platinum-based chemotherapy regimens have low response rates and high toxicity. Therefore, new research is necessary to develop more effective and better tolerated systemic therapies. As penile cancer is rare, research on this type of cancer is insufficient and deficient, although literature has reported that cell line models of penile cancer have been established(M et al., 2014). However, these cell lines remain relatively few, and cell lines and cell line xenografts cannot reproduce the heterogeneity and microenvironment of the tumor; thus, the clinical translation rate of studies related to cell lines and cell line xenografts in penile cancer is poor(R et al., 2022).
A patient-derived xenograft (PDX) model is a tumor model generated by implanting fresh human tissue (tumor, enriched circulating tumor cells) into immunodeficient mice(J, Y, R, & X, 2020). The PDX model provides a complete tumor–host environment, preserving the histology, genomic features, and drug responsiveness of the original human patient tumor, which can be used as an “avatar” for studies on drug responsiveness studies(SY et al., 2016). The PDX model preserves the heterogeneity and microenvironment of the tumor, and the experimental results are up to 90% consistent with the clinical results(GJ, 2020). To date, a large number of PDX models of tumors have been constructed in humans, but the establishment of the PDX model of penile cancer has been rarely reported(J, HS, & S, 2018). Patient-derived Xenograft explants (PDXE) model is an in vitro culture and drug screening of tumor tissue from PDX tumor-bearing mice. The fragments preserve the heterogeneity and microenvironment of the source patient’s tumor (particularly the preservation of immune cells within the tumor). Thus, their drug screening results are highly compatible with the clinical results and are also used for tumor immune drug testing. The PDXE model is inexpensive, and it has a short testing cycle. The PDX model has the highest clinical agreement, and PDXE is characterized by high throughput. Therefore, the use of PDX tumor tissue and PDXE efficacy evaluation has short processing time, low cost, high throughput, and high in vivo and ex vivo result consistency. It is also in accordance with the reduction and substitution principle within the 3R principle of experimental animals. Our team has developed a new drug screening method based on histoculture, which is known as hydrogel-embedded histoculture drug sensitivity test (HDST). HDST drug screening using PDX tumor-bearing mouse tissue fragment is a kind of PDXE. HDST drug screening may improve the inconsistency of ex vivo and in vivo results, reduce the amounts of mice used, and increase the success rate of new drug development.
Selinexor is an inhibitor of the human nuclear export protein XPO1(JC et al., 2021), which is a major protein that mediates multiple nuclear outputs and plays a crucial role in maintaining cellular homeostasis. XPO1 is an export receptor responsible for the nuclear-cytoplasmic transport of hundreds of proteins and multiple RNA species(NG & Y, 2020).Studies have shown that XPO1 was overexpressed in myeloma, lymphoma, ovarian cancer, brain glioblastoma, osteosarcoma, pancreatic cancer, cervical cancer, gastric cancer, and other malignant tumors. XPO1 is frequently overexpressed and/or mutated in human cancers and functions as an oncogenic driver. Therefore, suppression of XPO1-mediated nuclear export presents a unique therapeutic strategy(GL et al., 2014). On July 3, 2019, Selinexor was approved by the US Food and Drug Administration for the treatment of relapsed refractory multiple myeloma(P et al., 2020). Selinexor has also been reported to treat other tumors, but whether it could treat penile cancer remains unknown(AL et al., 2021).
In this study, we established a penile cancer PDX model to explore the effect and mechanism of XPO1 on penile cancer by using the PDX models and HDST. In addition, the safety of Selinexor against penile cancer was tested. The results of this study could provide experimental basis for the clinical application of Selinexor.